Impact of Self-Coiling Catheters for Continuous Popliteal Sciatic Block on Postoperative Pain Level and Dislocation Rate: A Randomized Controlled Trial

Impact of Self-Coiling Catheters for Continuous Popliteal Sciatic Block on Postoperative Pain Level and Dislocation Rate: A Randomized Controlled Trial | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Impact of Self-Coiling Catheters for Continuous Popliteal Sciatic Block on Postoperative Pain Level and Dislocation Rate: A Randomized Controlled Trial Rosa Nickl, Oliver Vicent, Thomas Müller, Anne Osmers, Konrad Schubert, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-959997/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background : Catheter dislocation within the tissue is a challenge in continuous regional anesthesia. A novel self-coiling catheter design has been available providing lower dislocation rate in a cadaver model. So far it hasn´t been demonstrated whether the self-coiling catheter offers any remarkable advantages for continuous peripheral regional anesthesia in vivo. Methods: After ethics committee approval 140 patients undergoing elective distal lower limb surgery were enrolled in this prospective randomized controlled trial. Preoperatively, patients were randomly assigned and received either the conventional (n=70) or self-coiling catheter (n=70) for ultrasound-guided popliteal sciatic nerve block in short axis view and in-plane approach from lateral. The primary endpoint was pain intensity after surgery and on the following days. Secondary outcomes investigated were dislocation rate in situ, externally visible catheter movement, opioid consumption as well as leakage at the puncture site. Results: All catheters were successfully inserted. The study population of self-coiling catheters had significantly lower mean numeric rating scale values than the reference cohort on the first (p=0.01) and second postoperative days (p<0.01). Sonographic evaluation has shown, 42 standard catheters (60 %) and 10 self-coiling catheters (14.3 %) were dislocated in situ within the first three postoperative days. The externally visible movement of the catheters at insertion site did not differ significantly and was on average less than 0.5 cm on the third day. The amount of opioids administered was significantly lower in the self-coiling catheter group on the day of surgery and on the second and third postoperative days (p=0.04, p=0.03 and p=0.04, respectively). Conclusion: The self-coiling catheter offers a superior postoperative pain control and a lower dislocation rate within the tissue for popliteal sciatic nerve blockade compared to a conventional catheter. Further trials in large patient cohorts are warranted to investigate potential beneficial effects of self-coiling catheters for other localisations and other application techniques. Trial registration : The trial was registered at German Clinical Trials Register (DRKS) on 08/04/2020 (DRKS00020938, retrospectively registered). Anesthesiology & Pain Medicine perineural catheter popliteal sciatic block self-coiling catheter dislocation ultrasound- guided re-gional anesthesia Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Background Continuous nerve blocks play an integral role in modern multimodal analgesia concepts [ 1 ]. Regional anesthesia is essential in orthopaedic and trauma surgery on the lower limb [ 2 ]. For both, the lower and upper extremities, randomized controlled trials have shown significant pain reduction by means of continuous regional anesthesia after surgery [ 3 , 4 ]. This also results in less chronic pain, a lower opioid requirement and associated side effects such as nausea, vomiting, constipation and fatigue [ 3 , 5 ]. However, in some studies analgesic advantages of continuous regional anesthesia fade after 24- 48 h [ 6 , 7 ]. The secondary failure rate of indwelling regional anesthesia catheters has been reported in literature up to 40 % [ 8 , 9 ]. Aside from initial misplacement secondary catheter dislocation during the postoperative course might be considered one possible explanation for the worsened efficacy of continuous regional anesthesia [ 10 ]. Secondary dislocation is commonly defined as outwardly visible displacement or sliding out of the catheter, partly accidently by the patient himself [ 11 , 12 ]. However, regarding dislocations, the rare event of external dislodgement at the insertion site has to be distinguished from internal catheter tip migration away from target structure or nerve surrounding compartment due to active and passive movement of adjacent muscles. The latter problem might be underestimated since pain scores, opioid consumption, sensory block distribution and patient´s satisfaction serve only unreliable surrogate measures for correct catheter position. Investigation of internal dislocations by direct visualization of the catheter tip or better by imaging of fluid spread referred to the nerve has been addressed only in a few studies with limited number of patients [ 10 , 13 , 14 ]. Two more studies have investigated dislocation rate in situ, either solely in healthy volunteers [ 15 ] or in human cadavers [ 16 ]. Stiff catheters placement using the most popular short axis (SAX) / in-plane (IP) approach might bear an increased risk of internal dislocations [ 10 , 16 ] since the catheter mostly can be placed only a short distance beyond the needle tip to avoid bypassing the nerve [ 17 ]. For a new catheter design it has been shown a very low risk of initial misplacement in cadavers for paravertebral blockades as well as sciatic nerve blockades [ 18 , 19 ] due to a 2.5 cm long self-coiling soft end of the catheter remaining close to the nerve. However, so far, no studies have investigated if self-coiling catheters are also more resistant to secondary dislocations with consecutive improvement of pain management in surgical patients. Therefore, we compared the self-coiling catheter with regular straight catheters for continuous popliteal sciatic blockade regarding efficacy and position change within and outside the tissue. Methods Study design This study is a prospective, randomized controlled, single-centre trial in a clinically interventional design. Ethics Positive ethic votum was approved by the Institutional Review Board of the Technische Universität Dresden (EK150042016). Written informed consent was obtained from all patients. This study is registered at the German Clinical Trials Register (DRKS00020938) and is reported according to the CONSORT guidelines 2010 [ 20 ]. Patients and randomisation 140 adult patients scheduled for continuous regional anesthesia with popliteal sciatic catheter as part of elective major surgery on the ankle or foot in the University Hospital Carl Gustav Carus at the Technische Universität Dresden, were enrolled between 09/2016 and 12/2017 for this trial. The applied inclusion and exclusion criteria are summarized in Table 1 . Randomisation was carried out immediately before catheter insertion by means of sequentially numbered sealed opaque envelopes, containing the study number and corresponding reference to the respective group. Patients were assigned to two groups: an interventional group with the application of the self-coiling catheter, SCC, (SonoLong Curl Echo 20 G 100 mm, Pajunk medical products, Geisingen, Germany) and a control group receiving the regular straight catheter, RSC, (SonoLong Sono 20 G 100 mm, Pajunk medical products, Geisingen, Germany) for popliteal sciatic block (figure 1 ). Surgeons, nurses, patients and members of the acute pain service and investigators apart from the anesthetists inserting the catheter were blinded to the study group. Investigators collecting data were not blinded to groups. Table 1 Inclusion and exclusion criteria Inclusion criteria Exclusion criteria − age between 18 and 75 years − indication for the application of a distal sciatic catheter within the scope of an elective surgical procedure − patient consent − patient suffering from chronic pain before surgery − polyneuropathy or ipsilateral neuropathy, involving the lower limb − refusal of regional anesthesia − patient not legally competent − intolerance or allergy to ropivacaine or oxy-codone − neuromuscular diseases − BMI >35 kg/m 2 − pre-existing opioid medication Application of regional anesthesia Patients were placed in supine position with the relevant leg elevated. After generous skin disinfection (ChloraPrep, Becton, Dickinson and Company, Franklin Lakes, USA) the area was covered with a sterile fenestrated sheet. The transducer was draped with a sterile ultrasound probe cover (CIV-Flex® Transducer Covers, Civco Medical Solutions, Kalona, Iowa, USA).The sciatic nerve was visualized from the posterior thigh in short axis view (SAX) at the level of the popliteal nerve bifurcation with a 4-12 MHz linear probe (L12-4) of a Philips Sparq or Philips Affiniti 70G ultrasound system (Philips Healthcare, Andover, Massachusetts, USA) or 5- 13 MHz linear probe (12L-RS) of a GE Logiq e ultrasound system (GE Healthcare, Milwaukee, Wisconsin, USA). Nerve bifurcation was defined as the most proximal point where the tibial and common fibular nerve clearly started to detach. After skin infiltration with 2-4 ml prilocaine 1 %, an 18 G Tuohy needle was advanced using an in-plane technique from lateral until the needle tip was located within the paraneural sheath. The designation of the sheaths of the sciatic nerve is referred to the previous publication of Andersen and colleagues [ 21 ]. Special care was taken not to touch the nerve or even puncture the epineurium. An initial bolus of 20 ml ropivacaine 0.5 % (Naropin 10 mg/ml, Astra Zeneca, London, UK) was applied directly via the injection line connected to the Tuohy puncture cannula under direct sonographic control. The desired spread of local anesthetic was circularly around both components of sciatic nerve within the paraneural sheath. If diffuse spreading into the surrounding tissue occurred, the cannula position was corrected. Afterwards, the previously randomized catheter was placed adjacent to the sciatic nerve within the paraneural sheath through the cannula. According to manufacturer instructions SCC was advanced approximately 2.5-3 cm beyond the needle tip to facilitate the coiling up of the distal catheter end. RSC was inserted approximately 3-4 cm past the needle tip. Subsequently proper catheter position was sonographically confirmed by observing the spread of a 2 ml bolus of saline injected via the catheter within the paraneural sheath. In case of spread outside of paraneural sheath catheter was retracted under real-time sonographic guidance until the injected saline bolus was reliably distributed around the nerves. Thereafter the catheter was connected to the associated bacterial filter and fixed with sterile wound suture strips (Omnistrip®, Fa. Paul Hartmann AG, Heidenheim, Germany). Finally, a sterile foil dressing (IV3000 10x12 cm, Smith & Nephew Medical Ltd., London, UK) was used to provide fixation of the catheter additionally. All catheters were placed as a part of the clinical anesthesia routine by a total of four senior anesthesiologists with substantial experience in performing ultrasound-guided popliteal sciatic nerve block. The success of the sciatic blockade was evaluated in all patients by testing warm-cold differentiation in the innervation area. Additional anesthetic procedures and hemodynamic monitoring The time course of proceeded interventions were summarized in figure 2 . After arriving in the operating area, peripheral venous access with an infusion of a balanced crystalloid solution, a 3- or 5-lead ECG monitoring including ST-segment analysis, a pulsoxymetry and non-invasive blood pressure measurement were established. Hemodynamic data were continuously recorded using a Philips Intellivue MP 70 (Philips Medicine Systems GmbH, Hamburg, Germany). If surgery involved the medial area of the lower leg, ankle or foot, an additional ultrasound guided saphenous nerve block was performed with 10 ml ropivacaine 0.5 % (Naropin 10 mg/ml, Astra Zeneca, London, UK) via an 80 mm 22 G Sonoplex cannula (Pajunk medical products, Geisingen, Germany) at femoral triangle by SAX view and in-plane approach. Further anesthesia procedures were based on the individual risk profile, patient´s comfort request and needs due to planned surgery procedures like tourniquet at the thigh. Independent of the randomization, in addition to the continuous peripheral sciatic blockade the following procedures were used: anesthesia standby, sedation, femoral and obturator nerve block and spinal or general anesthesia. For spinal anesthesia 2 to 2.4 ml of hyperbaric bupivacaine 0.5 % (Bucain hyperbar 5mg/ml, PUREN Pharma GmbH & Co. KG, Munich, Germany) with 10 µg fentanyl via a 25 G Sprotte cannula (Pajunk medical products, Geisingen, Germany) was used. Sedation was applied by use of propofol 20mg/ml (Fresenius Kabi Deutschland GmbH, Bad Homburg, Germany) with a rate of 1-2 mg/kg/h. General anesthesia was induced and maintained with propofol (Propofol 1 % and Propofol 2 %, Fresenius Kabi Deutschland GmbH, Bad Homburg, Germany) and sufentanile (Sufentanil-hameln 5 µg/ml, hameln pharmaceuticals gmbh, Hameln, Germany). The airway was secured by laryngeal mask (Ambu® AuraGain TM , Ambu GmbH, Bad Nauheim, Germany). Postoperative procedure and outcome parameter assessment After surgery, the patients were observed under cardiovascular monitoring in post anesthesia care unit, as appropriate. Afterwards they were transferred to general ward. Postoperatively, both groups received a continuous application of ropivacaine 0.2 % (Naropin 2 mg/ml, Astra Zeneca, London UK) at an initial rate of 6 ml/h. According to a multimodal pain management concept, all patients received oral ibuprofen 600 mg as basic analgesia every eight hours. In case of contraindications for ibuprofen, novamine sulfone (1 g every six hours) was administered as an alternative per os or intravenously. A pre-existing basic analgesia with novamine sulfone and ibuprofen, in the above-mentioned dosages, was maintained postoperatively. The patients were regularly visited by the acute pain service from the first post-operative day (POD) twice a day. Pain service visit included surveillance of infection signs, leakage and external dislocation at insertion site. In order to record the subjective pain level of the patient twice a day the numerical rating scale (NRS 0-10) was used as a semi-quantitative method. The first interview was conducted two hours after the end of the operation. The NRS, the spread of the sciatic blockage and any adverse events were recorded. For rescue pain (NRS>3) either, a manual bolus of 10 ml ropivacaine 0,3 % (Naropin, Astra Zeneca, London, UK) could be applicated by acute pain service staff or patients received oxycodone 10 mg (Oxygesic akut 10 mg, Mundipharma GmbH, Limburg, Germany) per os by ward nurses. The total daily requirement of ropivacaine and total oxycodone consumption was recorded. The position of indwelling catheters were revealed immediately after surgery at the PACU and daily on the first, second and third POD. For this purpose, distribution of a saline a bolus of 2- 8 ml via the catheter was observed under sonographic view with respect to the nerve and the adjacent paraneural sheath. Corresponding images were digitally stored and the detected position was documented. Three different positions of the catheter in relation to the nerve were categorized as depicted in figure 3 . In case of catheter dislocation, no further US-guided examinations were performed afterwards. Safety thresholds Participation in the trial was terminated at any time, if one of the following dropout criteria was fulfilled: request of the patient, allergic reaction to ropivacaine, novamine sulfone or ibuprofen, necessity of second operation during the follow up period. Primary and secondary outcomes The primary outcome was the individual postoperative pain intensity, assessed with the numerical rating scale (NRS) after surgery on the lower leg or foot in the first 72 hours. The patient classified the pain on a scale from 0 to 10. The following issues were identified as secondary outcomes: additional need for systemic opioids, rate of secondary dislocations within the tissue and dislocations and leakage at the injection site. Statistical analysis The sample size was calculated as followed. To demonstrate a clinically relevant difference of 1 level on an NRS of 0 to 10, a minimum of 64 patients were enrolled with a standard deviation of 2, a significance level of 0.05 and a power of 80 %. A drop-out rate of 8 % was expected. Therefore, 70 patients per group were included. In accordance with the case number planning, the evaluation was carried out with an unpaired two-sided Student´s t-test at 5 % level, assuming equality of variance. The distribution of continuous parameters was described by using of mean value and standard deviation (normally distributed) or by medians and quartiles. Categorical parameters were described by their absolute and relative frequencies, and differences between groups were examined using the Chi- square test according to Pearson or the exact test according to Fisher. Two-group comparisons of metric scaled variables were performed by independent two-sided t-tests after using Levene test checking equality of variances. To analyse the influence of possible covariates of respective baseline data, a covariance analysis was calculated to adjust for possible group differences for confounders. To correlate nominal and metric parameters, eta correlation coefficient was calculated. Statistical significance was considered at two-sided p <0.05. All calculations and graphs were performed and computed using SPSS (IBM SPSS Statistics Vers. 25, IBM Deutschland GmbH, Ehningen, Germany). Results From 09/2016 to 12/2017 1021 patients undergoing elective ankle or foot surgery were screened and 140 patients were enrolled in this study (figure 4 ). Both groups were comparable regarding baseline characteristics as depicted in Table 2 . The study was closed after enrolment of the planned 140 patients. Table 2 Baseline characteristics. RSC Group (n=70) SCC Group (n=70) Age [years] 50± 14 50± 13 Gender [no/%] Female 37 (53) 37 (53) Male 33 (47) 33 (47) Body height [cm] 171.7± 9,0 173.1± 10.2 Body weight [kg] 76.5± 13.7 79.3± 16.5 BMI [kg/m 2 ] 25.9± 3.7 26.3 ± 4.3 ASA [no./%] I 38 (54) 35 (50) II 27 (39) 33(47) III 5 (7) 2 (3) Surgical area Upper ankle joint 35 (50) 41 (59) Calcaneus 8 (11) 14 (20) Hallux 10 (14) 6 (9) Talus 6 (9) 0 (0) Metatarsal 10 (14.3) 7 (10) Tendons/syndesmosis of the ankle 1 (1) 2 (3) Values are given as absolute number (percentage) or mean (± standard deviation), as appropriate. ASA American Society of Anesthesiology physical status, BMI Body mass index, RSC regular straight catheter, SCC self-coiling catheter Catheter placement and additional anesthetic procedures Sonographic identification of the nerve and bifurcation was successfully possible in all patients. The mean performance time acquired for catheter placement was 12.9± 4.3 min (p=0.97) in both study groups. The catheter placement was successful in all patients indicated by the correct local anesthetic distribution within the paraneural sheath of the sciatic nerve and complete loss of sensory and motoric function in the supplied nerve territory. As shown in Table 3 , there was no statistic significant difference in duration of surgery and initial amount of administered ropivacaine. No difference between groups were detected regarding the number of additional saphenous nerve blocks and other additional anesthetic procedures as well as to the usage of postoperative basic analgesic medication. Table 3 Additional anesthetic procedures, duration of catheter placement and surgery, postoperative basic analgesic medication, ropivacaine consumption and leakage. RSC Group SCC Group p Value Saphenous nerve block 64 (91.4) 56 (80) 0.05 Additional anesthetic procedure [no/%] 0.17 General anesthesia 53 (75.7) 60 (85.7) Spinal anesthesia 10 (14.3) 6 (8.6) Femoral nerve and obturator nerve block 0 (0) 2 (2.9) Analgosedation 6 (8.6) 2 (2.9) none 1(1.4) 0 (0) Duration of catheter placement [min] 12.9± 4.3 12.9± 4.3 0.97 Duration of surgery [min] 94.4± 41.0 96.2± 39.4 0.79 Postop. analgesic medication [no/%] 0.2 Ibuprofen 46 (65.7) 55 (78.6) Novamine sulfone 19 (27.1) 13 (18.6) Ibuprofen+ Novamine sulfone 5 (7.1) 2 (2.9) Ropivacaine consumption [mg/ 24h] POD 0 283.8± 34.7 288.7± 10.0 0.26 POD 1 264± 112.1 233± 101.5 0.09 POD 2 108± 124.9 127.5± 116.7 0.38 POD 3 23± 84.4 52.1± 93.4 0.22 Leakage [no/%] POD 0 8 (11.4) 6 (8.6) 0.83 POD 1 22 (31.4) 21 (30) 0.84 POD 2 21 (30) 22 (31.4) 0.6 POD 3 3 (4.3) 9 (12.9) 0.07 Values are given as absolute number (percentage) or mean (± standard deviation), as appropriate. Difference between groups were tested with Chi-square test or two-sided Student´s t-test with statistical significance considered at p<0.05, POD postoperative day, RSC regular straight catheter, SCC self-coiling catheter. Primary outcome parameter- postoperative pain level The pain levels recorded daily over the observation period are depicted in figure 5 . The NRS scores did not differ significantly on the day of surgery (p=0.69). On POD 1 and POD 2, patients of SCC group showed significantly less pain than those in the RSC group. There was no difference in pain intensity between both study populations on POD 3. Secondary outcome parameters Opioid consumption The values of oxycodone consumption determined showed a wide spread and are summarized in Table 4 . All mean values of the oxycodone consumption are lower with the self-coiling catheter than with the conventional catheter. Significant differences between both groups were found on the day of surgery (p=0.04), POD 2 (p=0.03) and POD 3 (p=0.04). For POD 1 (p=0.19) a tendency in lower oxycodone consumption have been observed. Table 4 Oxycodone consumption of both study groups during study period. RSC Group SCC Group p Value Daily Oxycodone consumption (mg) POD 0 1.29± 4.45 0.14± 1.19 0.04* POD 1 15.57± 19.16 11.71± 15.32 0.19 POD 2 12.50± 14.90 7.57± 11.60 0.03* POD 3 7.94± 8.64 4.92± 7.88 0.04* Values are given as mean (± standard deviation). Statistical significance considered at p<0.05 (*). POD postoperative day, RSC regular straight catheter, SCC self-coiling catheter. Dislocation The spread of fluid could be detected in all sonographic examinations, which were performed throughout the study. Dislocation rates are shown in figure 6 . The majority of dislocations were found already after the surgical procedure and patient transfer to PACU. However, the dislocation of catheter was significant lower in the SCC group. (RSC n=19 vs. SCC n=1, p<0.01). Over the entire observation period, the SCC-cohort catheters dislocated less frequently than in the RSC group (p<0.01 for POD 1 & 2, p=0.01 for POD 3, respectively). The cumulative dislocation rate was 60 % (n=42) in RSC group and 14.3 % (n=10) in SCC group. For the first and second postoperative day, a significant influence of dislocation on the mean indicated NRS value could be demonstrated (POD 1 p<0.01; POD 2 p<0.01) as shown in figure 7 . Catheter insertion depth The puncture depth of both catheter groups did not differ significantly (p = 0.169) and averaged 5.8 (RSC) and 6.0 cm (SCC). However, the distance between the puncture depth and the final skin level of the catheters differed due to catheter design. The self-coiling catheters were placed at a mean of 2.4 cm above the final needle tip position. For the regular catheter, this value was 1.6 cm (p<0.01). No catheter in either group with an insertion depth greater than/equal to 3.5 cm dislocated in this study. The eta coefficient was 0.380 (p<0.01), resulting in a moderate correlation. Hence, 14.4 % of the dislocation variance can be explained by the insertion depth. External movement at the insertion site The outwardly visible movement of the pain catheters was documented daily. In contrast to the dislocation within the tissue, no significant difference between both groups could be detected over the entire observation period regarding the externally visible position at the insertion site (POD 0, p=0.86; POD 1, p=0.39; POD 2, p=0.65). In total, 7 (10 %) of the self- coiling catheters and 9 (12.9 %) of the regular straight catheters slipped back at least 1 cm or further (p=0.6). We could not observe any differences between correctly positioned and dislocated catheters regarding the outward movement of the catheters. Leakage Overall, leakage of the puncture sites was most frequently detected on the first and second postoperative day. We observed no significant differences in characteristics between the SCC and RSC group (POD 0, p=0.83; POD 1, p=0.84; POD 2, p=0.6; POD 3, p=0.07) as seen in Table 3 . Complications due to perineural catheter Eight patients (5.7 %) experienced minor local inflammation at the insertion site, which was utterly subsiding after removal in the further course of the trial. Because of catheter occlusion, one catheter in each study group (0.7 %) could no longer be used from the first and second postoperative day. One patient in the RSC group complained of a metallic taste and nausea after increasing the infusion rate of ropivacaine from 6 to 8 ml/h Ropivacaine 0.2 % and administration of a bolus. The catheter was then removed immediately and all symptoms were completely regressed within a few hours. No neurologic deficit occurred during the observation period. Discussion In this investigator-initiated randomized controlled trial it could be demonstrated that the use of a self-coiling catheter compared with a regular straight catheter for continuous popliteal sciatic block was more effective in terms of pain management and dislocation rate within the tissue. The latter appeared without visible external changes measured by leakage and external dislodgement of the catheter at the insertion site. The higher stability of the self-coiling catheter in its original positioning may result in lower pain levels on the first and second POD and a reduced opioid consumption compared to patients in the RSC group. To our knowledge this is the first trial investigating impact of different catheter characteristics on secondary dislocations and advantages of a self-coiling catheter for peripheral nerve block in clinical practice. Pain intensity Dislocation rate on the day of operation had no impact on pain levels because initial bolus of ropivacaine 0.5 % caused a long-lasting blockage of pain perception in both groups. Long acting ropivacaine provides nerve block duration of up to 18 hours, depending on dose and proximity of applied LA to the nerve. Christiansen et al. described a mean duration of action for distal sciatic blocks of more than 13 hours with a lower dose of 60 mg ropivacaine [ 22 ]. In this study 100 mg were administered. Various other studies have reported similar results. Several investigators compared a single popliteal block of the sciatic nerve with a continuous application of local anesthetic via catheter and determined no significant differences in pain intensity on the day of surgery for both groups [ 23 – 25 ]. The effect of the initially performed nerve block was effective in both groups and thus did not result in NRS-differences. The significance of the lower pain level of the SCC group on the first and second POD showed a measurable difference of 0.7 points on NRS to the control group. Even if this difference seems to be small, it can become relevant for the individual patient. The reason for the higher pain scores in the RSC group on POD 1 and 2 may be related to a higher dislocation rate outward of the fascial space of the sciatic nerve. Thus, a lower effective dose of continuous infused ropivacaine could act on the sciatic nerve. In contrast, the lack of difference on POD 3 might be explained by spontaneous pain relief in the late postoperative period. With the diminishing effect of the initial bolus of ropivacaine 0.5 % on the first postoperative day, the average pain level of all participants was highest compared to the other measure points. This might be caused by dislocations of indwelling catheters, insufficiency of lower continuous ropivacaine dose and pain perception in the regions not supplied by sciatic nerve when single shot of supplemental regional anesthesia had worn off. The latter issue is relevant if medial parts of the foot were involved in surgery and saphenous or femoral nerve block was established [ 26 ]. Pain perception in sensory territory of the saphenous nerve might have contributed to levelling pain intensity scores and scattering intergroup differences regarding perineural sciatic nerve catheter performance. Using an additional catheter for the saphenous nerve might have decreased pain scores and additional opioid use. However, reports about impact of the continuous or prolonged saphenous nerve block on pain after ankle surgery are conflicting. Whereas Fisker et al could not find advantage of continuous saphenous nerve block compared to single shot [ 27 ]. Jarell et al. showed lower pain scores and less opioid need with continuous block of saphenous nerve after ankle surgery [ 28 ]. Another investigator reported improved postoperative pain management with prolonged saphenous nerve block by additional perineural dexamethasone [ 29 ]. Surgery of the distal lower extremity or the foot has shown to be one of the most painful surgical interventions. In almost 71,000 patients with 179 different operations in all areas of the body, the calcaneus operation was revealed to be the most painful operation with a mean postoperative NRS of 6.68 on the first postoperative day. Other operations on the foot, forefoot or ankle were among the most painful fifteen operations with a mean NRS of at least 6 on the first postoperative day [ 2 ]. This underlines the importance of continuous regional anesthesia of the ankle and foot. In our study almost, all patients were free of pain on POD 0. In the further course, all mean NRS values in both cohorts remained at all examination times below 3.5 but only patients with self-coiling catheters performed with mean NRS 2.7 even lower than the commonly accepted intervention threshold of NRS 3. The absence of ultrasound-guidance and confirmation of proper catheter location, differently used local anesthetics and additional analgetic drugs, the heterogeneity of surgical procedures and the lack of information about mobilization strategies, complicate comparability with other studies. However, most studies show maximum pain intensity on POD 1 [ 23 – 25 , 30 – 32 ]. Similar to our results, usually pain level decreases day by day in the further course. The pain intensity of patients with continuous sciatic nerve block varied between 0 and 4 on POD 1. Our results are in this range. Many of the studies mentioned above had an outpatient setting which may be another reason for the fluctuation range in reported pain intensity. Patients were discharged with the peripheral nerve catheters on the day of surgery and received defined amounts of analgetics as well as instructions for mobilisation. Previous surgery, the duration and length of stay in hospital varied greatly or were not specified. The indicated operation times were very heterogeneous and ranged from 32 min [ 24 ] to 110 min [ 33 ]. That may have an impact on surgical trauma and consequently on pain intensity. The evaluation of pain and other criteria in the following days was conducted by telephone. As a result, it could not be clearly elucidated whether patients' statements are reliable and how mobilisation was carried out as additional pain stimulus. Oxycodone consumption Patients in the self-coiling catheter group had a lower need for oxycodone in the first three days after surgery. While the lower consumption of oxycodone in the SCC group differed by 1.1 mg from the RSC group on the day of surgery, already on POD 1 the consumption was 3.9 mg lower. This difference in lower consumption in the SCC group reached significant levels at the day of surgery, POD 2 (4.9 mg) and POD 3 (3 mg), with an overall decrease in the need for additional opioids already from the second postoperative day on. Interestingly, the significant elevated pain intensity in the RSC group did not reach the level to create a difference for opioid consumption on POD 1. Two facts might have influence accuracy of discrimination. First, we used a single prefixed dose of oxycodone 10 mg as rescue pain medication obeying our institutional multimodal pain concept. Therefore, discriminatory power regarding additional opioid need was low. Assumably, with lower opioid bolus provided by patient controlled intravenous analgesia we could have traced the opioid requirement more precisely. Second, over 50 % of patients in both groups had surgery that involved also innervation territory of saphenous nerve. Despite reliable sciatic nerve block, the fading effect of the single shot saphenous nerve block might have caused pain at the medial aspect to the ankle and foot and consequently might have led to elevated opioid consumption on POD 1. Thus, we could not distinguish, if opioid request was referred to poor catheter performance or terminated saphenous nerve block. However, the number of saphenous nerve blocks applied was not different between both catheter groups. Overall, the amount of opioid consumption in the present study is consistent with previous studies investigating continuous sciatic nerve block for foot and ankle surgery [ 25 , 30 – 32 ]. Additional anesthesia procedures A further aspect of the discussion is the possible influence of additional anesthetic procedures on postoperative pain intensity. Most patients (80.7 %) underwent adjunct general anesthesia, whereas 11.4 % received additional spinal anesthesia to the distal sciatic block. Sedation or additional peripheral regional anesthesia was given to the remaining 7.9 %. The choice of procedure was individually adapted to the comorbidities and patients request. Due to randomisation and group size there were no significant differences regarding the distribution between of additional anesthetic procedures between both groups, hence a possible influence might be negligible in this investigation. The question of whether spinal anesthesia has an influence on the postoperative pain level has not been conclusively clarified until now. YaDeau et al. compared general and spinal anesthesia, each in combination with PNB for operations on the ankle and foot in a recent randomised controlled trial. A significant difference of pain scores in favour of spinal anesthesia was found only one hour after the end of the operation [ 34 ]. In contrast to long acting morphine we used fentanyl as intrathecal supplemental opioid for spinal anesthesia. Thus, any effect on pain intensity beyond first 12 hours seems unlikely. Catheter orifices We compared in the present study a self-coiling catheter with a closed tip and six lateral microholes with a regular straight catheter that has only a single orifice at the end. One might question if this could have influenced our results. Fredrickson et al. investigated the outflow of injected fluid on catheters with a different number of orifices. They showed a dependency of the fluid spread pattern on the fluid flow rate. Below 80 ml per hour, fluid left multi-orifice catheters only on the most proximal orifice [ 35 ]. Only an injection rate over 100 ml per hour delivered all microholes. Considering our study´s flowrate of local anesthetics of 6- 10 ml per hour, the self-coiling catheter likely functioned rather as a single orifice catheter. Thus, we do not expect any relevant advantage of the multiple catheter orifice configuration in the present study. Moreover, considering that the SCC had been positioned only 2.4 cm into the target space within the perineural facial sheath, with continuous infusion the local anesthetic may have left the most proximal orifice only missing the target space partially if the catheter gets retracted by muscle movements. Clinical data regarding the influence of catheter orifice design on quality of pain management is conflicting, despite LA bolus application was used. Consequently, it can be concluded that catheters with multiple openings, such as the SCC, also function like conventional end-hole catheters at clinically relevant infusion rates. In this study there was a maximum continuous flow rate of 10 ml per hour. Only bolus applications by the acute pain service were probably applicated at speeds above 100 ml per hour. Since this injection was performed manually from a 10 ml syringe, no more precise statements can be made here about the application speed [ 36 , 37 ] Dislocation rate Despite the widespread use of continuous regional anesthesia the topic of perineural catheter dislocation is not well elucidated, neither in studies nor in clinical practice. Thus, the results of our study provide new insights regarding factors contributing to catheter dislocation. To our best knowledge, there is no clinical study investigating dislocation rate of self-coiling catheters compared to regular catheters so far. Luyet et al had shown a decreased initial misplacement rate for self-coiling catheters in human cadavers. However, the cadaver study design did not address dislocation rates in the further course [ 19 ]. Significantly fewer self-coiling catheters (14 %) slipped out of the subparaneural target space during the study period than regular catheters with straight ends (60 %). This significant difference might be caused by different insertion distances within the perineural fascia sheath. Ilfeld et al. [ 38 ] and Steffel et al. [ 16 ] described a higher dislodgement rate for lower insertion distance at the nerve. We used a regular straight catheter with an indwelling metal wire in the control group. Such firm catheters often pass the target structure and protrude out of the perineural fascia sheath during initial insertion of around 3 cm beyond the needle tip, especially if catheters are advanced in-plane perpendicular to the SAX imaged nerve. Thus, we had to adjust the catheter by retraction until LA injection was distributed well within the perineural fascia sheath under sonographic view. The self-coiling catheter provide a more reliable initial placement without passing the target space if the insertion distance of 3 cm beyond the needle tip is not exceeded using an in-plane approach [ 19 ]. Thus self-coiling catheters require less likely a withdrawal due to initial misplacement and have a longer catheter segment remaining around the target structure. For postoperative evaluation of catheter position and initial confirmation of correct catheter placement we used sonographic imaging of saline bolus via the catheter. Although the efficacy of continuous regional anesthesia is depending on proper catheter location, assessment of catheter position is still not a common procedure neither in studies nor in clinical routine [ 39 ]. Postoperative break through pain and need of additional systemic analgesic medication are often considered surrogate markers for insufficient catheter performance due to any reason. However, this concept is misleading to prove an incorrect catheter position. It has to be considered that the visualization of catheter position is often compromised by sterile dressing and swollen tissue in the affected area. Several methods for visualization of catheter position have been described in the literature, a.e. imaging of injected fluid (either saline, LA, or contrast medium) or air spreading out of catheter orifice or direct visualization of the catheter [ 14 , 16 , 40 – 42 ]. Imaging techniques include high resolution ultrasound (HRUS), computer tomography (CT), or magnetic resonance imaging (MRI) [ 19 , 40 , 41 , 43 ]. There are pros and cons of each technique that we would like to discuss briefly. We decided for the injection of saline to prove catheter tip position because it is a safe and straightforward method that is part of our daily clinical routine. Moreover, it avoids unnecessary local anesthetic doses and harm to vulnerable structures nearby. The use of air or agitated fluid with microbubbles may enhance contrast and visualization of the injectate. However, spreading air within the tissue decreases markedly sonographic imaging quality of the target structure and surrounding tissue by scattered ultrasound waves. In contrast, visualization of saline via the catheter is similar to common procedure of observing local anesthetic injection via the cannula. Finally, direct visualization of the catheter is less favourable. On the one hand, despite the improved echogenity of catheters they hardly alignm with the ultrasound beam plane like a firm needle. This issue is aggravated by the use of self-coiling catheters. On the other hand, according similar to the injection over needles, control of spread of LA around the target structure is more important for a reliable block success than the catheter tip position itself. Compared to CT and MRI high resolution ultrasound imaging is commonly available. HRUS is a real point of care technique that can be applied as often as desired by the anesthesiologist avoiding unnecessary patient transports and staff expenses. Furthermore, CT examination exposes patients to radiation burden. In our study the most dislocations were discovered after arrival at the PACU. It can be assumed that passive and/or active movement of the thigh musculature occurs when the patient is positioned prior to surgery or during patient transfer to bed. This causes mechanical traction to the catheter within the biceps femoris muscle pulling the catheter back outward of the target space within the nerve-surrounding fascia. The dislocation rate within tissue was 14 % for the self-coiling catheter or 60 % for the regular straight catheter. Marhofer et al. examined the dislocation rates within the tissue in healthy volunteers. They determined a dislocation rate after movement of 25 % and 5 % for perineural femoral and interscalene catheter [ 15 ]. In contrast to our investigation, catheters were only examined for six hours after insertion. In addition, both catheters were placed using the out-of-plane technique, which is more robust against dislocation [ 43 ]. Only two studies address internal dislocation rates for continuous popliteal sciatic nerve block. Steffel et al. compared a catheter-over-needle (CON) with a conventional catheter-through-needle (CTN) technique in human cadaver [ 16 ]. 27 % of the CON catheters dislocated from the fascial sheath of the sciatic nerve. In contrast, all conventional catheters remained perineural. Remarkably, Steffel et al. did not evaluate the spread of the local anesthetic, but only visualized sonographically the suspected end of the catheter in the sonography. However, LA spread around the target is the decisive determinant for a sufficient nerve block. Comparisons with our study are difficult, since only a tiny cohort of 30 persons was involved and the tissue characteristics of the body donors cannot be considered identical to those of living subjects [ 16 ]. In contrast to our patients, only passive flexion movements were performed on the body donors. However, we believe that an active contraction and relaxing of the muscle contributes considerably to the movements of the catheter within the tissue. Hauritz and colleagues compared two different approaches for popliteal sciatic blockade, regarding dislocation within the tissue. They confirmed catheter location 48 h after application by means of an MRI contrast bolus [ 10 ]. Whereas a dislocation rate of 10 % for the out-of-plane approach was reported, the use of an in-plane technique similar to our study protocol resulted in a much higher dislocation rate of 40 %. We found an even higher dislocation rate of 60 % for conventional catheters in our study. Important difference is the longer part of catheter remaining under the perineural fascia sheath. A catheter distance within the perineural fascia sheath of 1.6 cm in our study compared to 3.4 cm in the investigation of Hauritz et al. may increase catheter dislocations due to traction forces as already mentioned before. Interestingly, the application of self-coiling catheter using the in-plane approach decreased the dislocation rate to a level reported by Hauritz et al. for the out-of-plane technique. Whereas regular straight perineural catheters seem more reliable in point of dislocation rate using out-of-plane approach, whereas the self-coiling catheters may be placed with good results performing the in-plane technique. Leakage and catheter shift at the insertion site The maximum leakage rate was 31.4 % in both groups in our study. This is comparable with the leaking rate of 31 % for CTN technique in another study [ 40 ]. Lower leakage rates of 13.9 % for continuous distal sciatic catheters were reported [ 44 ]. Leakage problems commonly occur with catheter-through-needle approaches, because needle´s diameter is larger than the catheter. Thus, the tissue is not sealing the puncture track along the catheter and injected fluid as well as interstitial fluid or blood can flow retrogradely. Though catheter-over-needle technique decreases the occurrence of leaking, no superiority regarding dislocation rates has been shown in clinical trials so far [ 40 , 45 , 46 ]. Accordingly, we did not observe any relation between leakage and dislocations since both study groups showed the same leakage rate. Dislocation rates in terms of the catheter slipping out of the skin at the insertion site are reported with an incidence of 0.5 to 26 % [ 8 , 9 ]. In our study we considered an outward slipping at the insertion site of 1 cm or more as a clinically relevant movement. This was evident in 10 % in SCC group and 12.6 % in RSC group. According to findings of Marhofer et al. we could not observe a significant impact of outwardly slipped catheters at insertion site on the dislocation rate at target area [ 15 ]. Complications The overall complication rate was very low. No persistent neurologic deficit was observed. The most severe complication was a patient with a metallic taste several hours after catheter application considered as a mild sign of local anesthetic systemic toxicity. Ropivacaine infusion was stopped. Neither a negative aspiration test nor sonographic imaging of fluid spread via the catheter revealed a secondary intravascular dislocation. The catheter was removed immediately, followed by complete regression of symptoms. The overall mild infection rate of 5.7 % observed here ranges within the results of other studies [ 47 , 48 ]. Mild infection was considered as any redness of the puncture site during daily visit. The catheters were removed immediately without any further sequels. In this study, catheter occlusion occurred in one patient from each cohort (total 1.4 %). Ma et al. reported this rare incident with a rate of 1 % [ 44 ]. Limitations Our results are limited to the use of ropivacaine for the initial bolus. The dislocated catheters probably would have been earlier discovered by using a short- or middle-long acting local anesthetic for the initial bolus. Additionally, for rescue pain management patients received opioids orally by nurses only on demand in a fixed dosage of 10 mg Oxycodone. A more finely tuned opioid application, e.g. by patient controlled intravenous analgesia could have led to a clearer reflection of the actual need for additional painkillers. Another limitation is the single shot concept for saphenous nerve block with limited pain relief of 12- 18 hours. Thus, NRS scores may have been influenced by pain perception in saphenous nerve innervation area. Furthermore, the design of our study was not double blinded since the ultrasound examiner occasionally could have drawn conclusions regarding catheter type by watching insertion depth specific catheter length graduations. The results of this study apply only to our setting of short axis view of the nerve and in-plane needle approach. Beyond that, our results are not applicable for other catheter designs or alternative insertion sites. In the case of sonographically confirmed catheter dislocation in situ, no further positional checks were performed. Whether it is possible that the misalignment could spontaneously convert to a renewed perineural position or not remains unclear. Furthermore, extrafascial dislocation does not necessarily mean a complete loss of effectiveness. Our continuous ropivacaine dose may have been still sufficient to release pain by local anesthetic spreading toward the nerve along the residual puncture pathway or by diffusion through the connective tissue. Experience from the efficacy of interfascial plane blocks (e.g. the erector spinae block), we suspect some analgetic effects of even low amounts of LA by blocking small C-fibres, even if the application site is not close to the target nerve. Conclusions The self-coiling catheter design for continuous popliteal sciatic nerve block offers a superior postoperative pain control and a lower dislocation rate within the tissue than a conventional straight catheter design. Secondary migration, away from the nerve target structure, could only be visualised sonographically and was not related to the external appearance at the puncture site. Additional studies for other alternative techniques and localization are warranted to further evaluate this design. Abbrevations AE: adverse event; CTN: Catheter-through-needle; CON: Catheter-over-needle; CONSORT: Consolidated Standards of Reporting Trials; IP: in-plane; LA: local anesthetic; NRS: numeric rating scale; OOP: out-of-plane; PACU: post anesthesia care unit; PNB: peripheral nerve block; POD: postoperative day; RA: regional anesthesia; RSC: regular straight catheter; SAE: severe adverse event; SAX: short axis view; SCC: self-coiling catheter; US: ultrasound Declarations Ethics approval and consent to participate The present trial was approved by the local institutional review board of the TU Dresden, the “Ethikkomission an der Technischen Universität Dresden”, Dresden, Germany (approval number: EK 150042016). Written informed consent was obtained from all participants with the informed consent form prior to trial enrolment. All methods were carried out in accordance with the Declaration of Helsinki. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Competing interests OV performs consulting services and receives lecture honoraria from Pajunk, Geisingen, Germany and Sintetica GmbH, Muenster, Germany. All other authors declare that they have no competing interests. Funding The present trial was supported by Pajunk, Geisingen, Germany, who provided the trial catheters, but had no part in study design, data collection, interpreting the results or preparing the manuscript. Support was provided by the Open Access Funding by the Publication Fund of the TU Dresden. Author ´ s contribution OV and RN designed the study protocol, generated the random allocation sequence, enrolled participants, and collected data and contributed to manuscript preparation. OV, AO and TM helped with data collection including performance of sonographic controls of the catheter positions. RN, KS and TR performed the statistical data analysis. TR, OV and TK helped preparing the manuscript and interpreting the data. All authors have read and approved the manuscript. Acknowledgements The authors thank the anesthetic and surgical staff of the University Center of Orthopaedics and Traumatology and Comprehensive Pain Center, University Hospital Carl Gustav Carus Dresden, Dresden, Germany. Data was part of thesis by Rosa Nickl. Author ´ s information 1 Department of Anesthesiology and Critical Care Medicine, University Hospital Carl Gustav Carus at the Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany. 2 Institute for Medical Informatics and Biometry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany. References Chelly JE, Ghisi D, Fanelli A. Continuous peripheral nerve blocks in acute pain management. British Journal of Anaesthesia. 2010;105:i86–96. Gerbershagen HJ, Aduckathil S, van Wijck AJM, Peelen LM, Kalkman CJ, Meissner W. Pain Intensity on the First Day after Surgery: A Prospective Cohort Study Comparing 179 Surgical Procedures. Anesthesiology. 2013;118:934–44. Salviz EA, Xu D, Frulla A, Kwofie K, Shastri U, Chen J, et al. Continuous Interscalene Block in Patients Having Outpatient Rotator Cuff Repair Surgery: A Prospective Randomized Trial. Anesthesia & Analgesia. 2013;117:1485–92. Peng L, Ren L, Qin P, Chen J, Feng P, Lin H, et al. Continuous Femoral Nerve Block versus Intravenous Patient Controlled Analgesia for Knee Mobility and Long-Term Pain in Patients Receiving Total Knee Replacement: A Randomized Controlled Trial. Evidence-Based Complementary and Alternative Medicine. 2014;2014:1–12. Sakai N, Inoue T, Kunugiza Y, Tomita T, Mashimo T. Continuous Femoral Versus Epidural Block for Attainment Of 120° Knee Flexion After Total Knee Arthroplasty: A Randomized Controlled Trial. The Journal of Arthroplasty. 2013;28:807–14. Albrecht E, Bathory I, Fournier N, Jacot-Guillarmod A, Farron A, Brull R. Reduced hemidiaphragmatic paresis with extrafascial compared with conventional intrafascial tip placement for continuous interscalene brachial plexus block: a randomized, controlled, double-blind trial. British Journal of Anaesthesia. 2017;118:586–92. Abildgaard JT, Lonergan KT, Tolan SJ, Kissenberth MJ, Hawkins RJ, Washburn R, et al. Liposomal bupivacaine versus indwelling interscalene nerve block for postoperative pain control in shoulder arthroplasty: a prospective randomized controlled trial. Journal of Shoulder and Elbow Surgery. 2017;26:1175–81. Ahsan ZS, Carvalho B, Yao J. Incidence of Failure of Continuous Peripheral Nerve Catheters for Postoperative Analgesia in Upper Extremity Surgery. The Journal of Hand Surgery. 2014;39:324–9. Gurnaney H, Kraemer FW, Maxwell L, Muhly WT, Schleelein L, Ganesh A. Ambulatory Continuous Peripheral Nerve Blocks in Children and Adolescents: A Longitudinal 8-Year Single Center Study. Anesthesia & Analgesia. 2014;118:621–7. Hauritz RW, Pedersen EM, Linde FS, Kibak K, Børglum J, Bjoern S, et al. Displacement of popliteal sciatic nerve catheters after major foot and ankle surgery: a randomized controlled double-blinded magnetic resonance imaging study. British Journal of Anaesthesia. 2016;117:220–7. Fredrickson MJ, Leightley P, Wong A, Chaddock M, Abeysekera A, Frampton C. An analysis of 1505 consecutive patients receiving continuous interscalene analgesia at home: a multicentre prospective safety study. Anaesthesia. 2016;71:373–9. Walker BJ, Long JB, De Oliveira GS, Szmuk P, Setiawan C, Polaner DM, et al. Peripheral nerve catheters in children: an analysis of safety and practice patterns from the pediatric regional anesthesia network (PRAN). British Journal of Anaesthesia. 2015;115:457–62. Edward Kim T, Howard SK, Funck N, Kyle Harrison T, Walters TL, Wagner MJ, et al. A randomized comparison of long-axis and short-axis imaging for in-plane ultrasound-guided popliteal-sciatic perineural catheter insertion. J Anesth. 2014;28:854–60. Swenson JD, Davis JJ, DeCou JA. A Novel Approach for Assessing Catheter Position After Ultrasound-Guided Placement of Continuous Interscalene Block: Anesthesia & Analgesia. 2008;106:1015–6. Marhofer D, Marhofer P, Triffterer L, Leonhardt M, Weber M, Zeitlinger M. Dislocation rates of perineural catheters: a volunteer study. British Journal of Anaesthesia. 2013;111:800–6. Steffel L, Howard SK, Borg L, Mariano ER, Leng JC, Kim TE. Randomized comparison of popliteal-sciatic perineural catheter tip migration and dislocation in a cadaver model using two catheter designs. Korean Journal of Anesthesiology. 2017;70-72. Ilfeld BM, Fredrickson MJ, Mariano ER. Ultrasound-Guided Perineural Catheter Insertion: Three Approaches but Few Illuminating Data. Regional Anesthesia and Pain Medicine. 2010;35:123–6. Luyet C, Meyer C, Herrmann G, Hatch GM, Ross S, Eichenberger U. Placement of coiled catheters into the paravertebral space*: Placement of coiled catheters in the paravertebral space. Anaesthesia. 2012;67:250–5. Luyet C, Seiler R, Herrmann G, Hatch GM, Ross S, Eichenberger U. Newly Designed, Self-Coiling Catheters for Regional Anesthesia-An Imaging Study: Regional Anesthesia and Pain Medicine. 2011;36:171–6. Eldridge SM, Campbell MJ, Bond CM, Hopewell S, Thabane L, Lancaster GA. CONSORT 2010 statement: extension to randomised pilot and feasibility trials. Pilot Feasibility Stud. 2016;2:64, s40814-016-0105–8. Andersen HL, Andersen SL, Tranum-Jensen J. Injection Inside the Paraneural Sheath of the Sciatic Nerve: Direct Comparison Among Ultrasound Imaging, Macroscopic Anatomy, and Histologic Analysis. Regional Anesthesia and Pain Medicine. 2012;37:410–4. Christiansen CB, Madsen MH, Rothe C, Andreasen AM, Lundstrøm LH, Lange KHW. Volume of ropivacaine 0.2% and sciatic nerve block duration: A randomized, blinded trial in healthy volunteers. Acta Anaesthesiol Scand. 2020;64:238–44. Ding DY, Manoli A, Galos DK, Jain S, Tejwani NC. Continuous Popliteal Sciatic Nerve Block Versus Single Injection Nerve Block for Ankle Fracture Surgery: A Prospective Randomized Comparative Trial. Journal of Orthopaedic Trauma. 2015;29:393–8. Zaric D, Boysen K, Christiansen J, Haastrup U, Kofoed H, Rawal N. Continuous popliteal sciatic nerve block for outpatient foot surgery - a randomized, controlled trial. Acta Anaesthesiol Scand. 2004;48:337–41. Elliot R, Pearce CJ, Seifert C, Calder DJ. Continuous Infusion Versus Single Bolus Popliteal Block Following Major Ankle and Hindfoot Surgery: A Prospective, Randomized Trial. Foot & Ankle International. 2010;31:1043–7. Kåsine T, Romundstad L, Rosseland LA, Fagerland MW, Kessler P, Omenås IN, et al. Ultrasonographic needle tip tracking for in-plane infraclavicular brachialis plexus blocks: a randomized controlled volunteer study. Reg Anesth Pain Med. 2020;45:634–9. Fisker AK, Iversen BN, Christensen S, Linde F, Nielsen KK, Børglum J, et al. Combined saphenous and sciatic catheters for analgesia after major ankle surgery: a double-blinded randomized controlled trial. Can J Anesth/J Can Anesth. 2015;62:875–82. Jarrell K, McDonald E, Shakked R, Nicholson K, Kasper V, Raikin SM. Combined Popliteal Catheter With Single-Injection vs Continuous-Infusion Saphenous Nerve Block for Foot and Ankle Surgery. Foot Ankle Int. 2018;39:332–7. Bjørn S, Linde F, Nielsen KK, Børglum J, Hauritz RW, Bendtsen TF. Effect of Perineural Dexamethasone on the Duration of Single Injection Saphenous Nerve Block for Analgesia After Major Ankle Surgery: A Randomized, Controlled Study. Regional Anesthesia and Pain Medicine. 2017;42:210–6. Bendtsen TF, Nielsen TD, Rohde CV, Kibak K, Linde F. Ultrasound Guidance Improves a Continuous Popliteal Sciatic Nerve Block When Compared With Nerve Stimulation: Regional Anesthesia and Pain Medicine. 2011;36:181–4. Capdevila X, Dadure C, Bringuier S, Bernard N, Biboulet P, Gaertner E, et al. Effect of Patient-controlled Perineural Analgesia on Rehabilitation and Pain after Ambulatory Orthopedic Surgery: A Multicenter Randomized Trial. Anesthesiology. 2006;105:566–73. Ilfeld BM, Morey TE, Wang RD, Enneking FK. Continuous Popliteal Sciatic Nerve Block for Postoperative Pain Control at Home: A Randomized, Double-Blinded, Placebo-Controlled Study. Anesthesiology. 2002;97:959–65. White PF, Issioui T, Skrivanek GD, Early JS, Wakefield C. The Use of a Continuous Popliteal Sciatic Nerve Block After Surgery Involving the Foot and Ankle: Does It Improve the Quality of Recovery?: Anesthesia & Analgesia. 2003;97:1303–9. YaDeau JT, Fields KG, Kahn RL, LaSala VR, Ellis SJ, Levine DS, et al. Readiness for Discharge After Foot and Ankle Surgery Using Peripheral Nerve Blocks: A Randomized Controlled Trial Comparing Spinal and General Anesthesia as Supplements to Nerve Blocks. Anesthesia & Analgesia. 2018;127:759–66. Fredrickson MJ. Randomised Comparison of an End-Hole, Triple-Hole and Novel Six-Hole Catheter for Continuous Interscalene Analgesia. Anaesthesia and Intensive Care. 2014;42:37–42. Novello-Siegenthaler A, Hamdani M, Iselin-Chaves I, Fournier R. Ultrasound-guided continuous femoral nerve block: a randomized trial on the influence of femoral nerve catheter orifice configuration (six-hole versus end-hole) on post-operative analgesia after total knee arthroplasty. BMC Anesthesiol. 2018;18:191. Fredrickson MJ, Ball CM, Dalgleish AJ. Catheter Orifice Configuration Influences the Effectiveness of Continuous Peripheral Nerve Blockade: Regional Anesthesia and Pain Medicine. 2011;36:470–5. Ilfeld BM, Sandhu NS, Loland VJ, Madison SJ, Suresh PJ, Mariano ER, et al. Ultrasound-Guided (Needle-in-Plane) Perineural Catheter Insertion: The Effect of Catheter-Insertion Distance on Postoperative Analgesia. Regional Anesthesia and Pain Medicine. 2011;36:261–5. Schnabel A, Meyer-Frießem CH, Zahn PK, Pogatzki-Zahn EM. Ultrasound compared with nerve stimulation guidance for peripheral nerve catheter placement: a meta-analysis of randomized controlled trials. British Journal of Anaesthesia. 2013;111:564–72. Finneran JJ, Swisher MW, Gabriel RA, Said ET, Abanobi MU, Abramson WB, et al. Suture-method versus Through-the-needle Catheters for Continuous Popliteal-sciatic Nerve Blocks. Anesthesiology. 2020;132:854–66. Marhofer P, Anderl W, Heuberer P, Fritz M, Kimberger O, Marhofer D, et al. A retrospective analysis of 509 consecutive interscalene catheter insertions for ambulatory surgery. Anaesthesia. 2015;70:41–6. Brookes J, Sondekoppam R, Armstrong K, Uppal V, Dhir S, Terlecki M, et al. Comparative evaluation of the visibility and block characteristics of a stimulating needle and catheter vs an echogenic needle and catheter for sciatic nerve block with a low-frequency ultrasound probe. British Journal of Anaesthesia. 2015;115:912–9. Hauritz RW, Pedersen EM, Linde FS, Kibak K, Børglum J, Bjoern S, et al. Displacement of popliteal sciatic nerve catheters after major foot and ankle surgery: a randomized controlled double-blinded magnetic resonance imaging study. British Journal of Anaesthesia. 2016;117:220–7. Ma H-H, Chou T-FA, Tsai S-W, Chen C-F, Wu P-K, Chen W-M. The efficacy and safety of continuous versus single-injection popliteal sciatic nerve block in outpatient foot and ankle surgery: a systematic review and meta-analysis. BMC Musculoskelet Disord. 2019;20:441. Ip VHY, Rockley MC, Tsui BCH. The catheter-over-needle assembly offers greater stability and less leakage compared with the traditional counterpart in continuous interscalene nerve blocks: a randomized patient-blinded study. Canadian Journal of Anesthesia/Journal canadien d’anesthésie. 2013;60:1272–3. Tsui BC, Ip VH. Catheter-over-needle method reduces risk of perineural catheter dislocation. British Journal of Anaesthesia. 2014;112:759–60. Morin AM, Kerwat KM, Klotz M, Niestolik R, Ruf VE, Wulf H, et al. Risk factors for bacterial catheter colonization in regional anaesthesia. BMC Anesthesiology. 2005;5:1. Neuburger M, Breitbarth J, Reisig F, Lang D, Büttner J. Komplikationen bei peripherer Katheterregionalanästhesie: Untersuchungsergebnisse anhand von 3491 Kathetern. Der Anaesthesist. 2006;55:33–40. Kerwat K, Eberhart L, Kerwat M, Hörth D, Wulf H, Steinfeldt T, et al. Chlorhexidine Gluconate Dressings Reduce Bacterial Colonization Rates in Epidural and Peripheral Regional Catheters. BioMed Research International. 2015;2015:149785. Aubuchon A, Arnold WD, Bracewell A, Hoyle JC. Sciatic neuropathy due to popliteal fossa nerve block: Short Report. Muscle & Nerve. 2017;56:822–4. Park YU, Cho JH, Lee DH, Choi WS, Lee HD, Kim KS. Complications After Multiple-Site Peripheral Nerve Blocks for Foot and Ankle Surgery Compared With Popliteal Sciatic Nerve Block Alone. Foot & Ankle International. 2018;39:731-5. Uchino T, Miura M, Oyama Y, Matsumoto S, Shingu C, Kitano T. Lateral deviation of four types of epidural catheters from the lumbar epidural space into the intervertebral foramen. J Anesth. 2016;30:583–90. Mariano ER, Yun RDH, Kim TE, Carvalho B. Application of Echogenic Technology for Catheters Used in Ultrasound-Guided Continuous Peripheral Nerve Blocks. Journal of Ultrasound in Medicine. 2014;33:905–11. Takatani J, Takeshima N, Okuda K, Uchino T, Noguchi T. Ultrasound visibility of regional anesthesia catheters: an in vitro study. Korean J Anesthesiol. 2012;63:59-64. Moy DM, Kim TE, Harrison TK, Leng JC, Carvalho B, Howard SK, et al. Comparative Echogenicity of an Epidural Catheter and 2 New Catheters Designed for Ultrasound-Guided Continuous Peripheral Nerve Blocks: Echogenicity of 3 Regional Anesthesia Catheters. J Ultrasound Med. 2017;36:2571–6. Jaime F, Mandell GL, Vallejo MC, Ramanathan S. Uniport soft-tip, open-ended catheters versus multiport firm-tipped close-ended catheters for epidural labor analgesia: a quality assurance study. Journal of Clinical Anesthesia. 2000;12:89–93. Shih C-K, Wang F-Y, Shieh C-F, Huang J-M, Lu I-C, Wu L-C, et al. Soft catheters reduce the risk of intravascular cannulation during epidural block—A retrospective analysis of 1117 cases in a medical center. The Kaohsiung Journal of Medical Sciences. 2012;28:373–6. Additional Declarations Competing interest reported. OV performs consulting services and receives lecture honoraria from Pajunk, Geisingen, Germany and Sintetica GmbH, Muenster, Germany. All other authors declare that they have no competing interests. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major revision 17 Jan, 2022 Reviews received at journal 05 Jan, 2022 Reviewers agreed at journal 17 Dec, 2021 Reviewers agreed at journal 14 Dec, 2021 Editor assigned by journal 14 Dec, 2021 Reviewers invited by journal 13 Dec, 2021 Editor invited by journal 25 Oct, 2021 Submission checks completed at journal 25 Oct, 2021 First submitted to journal 08 Oct, 2021 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-959997","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":58860397,"identity":"7fd46718-3bbf-4e2c-b63d-03432a731685","order_by":0,"name":"Rosa Nickl","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzklEQVRIiWNgGAWjYPACCQYJduYDjA1szAwMB4jWwsyWQJIWoCZmHgPitJi3tz/8wLjDQl6ymeeb5Iwyawa+4w34tcicOWMswXhGwnA2M+82yQ3n0hkkzxCwRkIih0GCsU0iQQ6k5WHbYQaDGwmEtKQ//gHRwvMMouX+A0JaEszAtkgz87BJbgTbgl8HgwTPGTOLxDYJw5nNbMaWM86l80ieIeQw9vbHNz621clLHG9+eLOnzFqO7/gBAtaAALKxPESoHwWjYBSMglFACAAAZPI8pJ5/uzwAAAAASUVORK5CYII=","orcid":"","institution":"University Hospital Carl Gustav Carus Dresden, Technische Universität Dresden","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Rosa","middleName":"","lastName":"Nickl","suffix":""},{"id":58860398,"identity":"aa117a97-d291-4669-a886-98a6fd477e06","order_by":1,"name":"Oliver Vicent","email":"","orcid":"","institution":"University Hospital Carl Gustav Carus Dresden, Technische Universität Dresden","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Oliver","middleName":"","lastName":"Vicent","suffix":""},{"id":58860399,"identity":"ec154681-eb54-42cf-8d12-13f976e0a949","order_by":2,"name":"Thomas Müller","email":"","orcid":"","institution":"University Hospital Carl Gustav Carus Dresden, Technische Universität Dresden","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Thomas","middleName":"","lastName":"Müller","suffix":""},{"id":58860400,"identity":"6eef02ab-e4a0-45a5-be57-f8bc17be6f40","order_by":3,"name":"Anne Osmers","email":"","orcid":"","institution":"University Hospital Carl Gustav Carus Dresden, Technische Universität Dresden","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Anne","middleName":"","lastName":"Osmers","suffix":""},{"id":58860401,"identity":"8f168e44-1893-4a9e-b201-13b61c890351","order_by":4,"name":"Konrad Schubert","email":"","orcid":"","institution":"Technische Universität Dresden","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Konrad","middleName":"","lastName":"Schubert","suffix":""},{"id":58860402,"identity":"2f58e6a4-544c-4a42-bfd0-6963a81a0303","order_by":5,"name":"Thea Koch","email":"","orcid":"","institution":"University Hospital Carl Gustav Carus Dresden, Technische Universität Dresden","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Thea","middleName":"","lastName":"Koch","suffix":""},{"id":58860403,"identity":"63b042d2-2380-4120-bd24-92aebf31d09b","order_by":6,"name":"Torsten Richter","email":"","orcid":"","institution":"University Hospital Carl Gustav Carus Dresden, Technische Universität Dresden","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Torsten","middleName":"","lastName":"Richter","suffix":""}],"badges":[],"createdAt":"2021-10-08 08:44:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-959997/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-959997/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":14924528,"identity":"99d32652-6285-4266-b0ee-37c0f0525003","added_by":"auto","created_at":"2021-10-26 21:09:19","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1401443,"visible":true,"origin":"","legend":"Study catheters and needle.\na+c \tSelf-Coiling Catheter (Sono Long Curl Echo 20 G 100 mm, Pajunk medical products, Geising-en, Germany), a catheter tip; c entire catheter\n b+d \tRegular straight catheter (Sono Long Sono 20 G 100 mm, Pajunk medical products, Geising-en, Germany), b catheter tip; d entire catheter\n","description":"","filename":"Figure1Studycathetersandneedle..png","url":"https://assets-eu.researchsquare.com/files/rs-959997/v1/db77d1b4db24674bd6ee6e13.png"},{"id":14924580,"identity":"350f9117-b4e3-4c59-9218-1c9683e9134b","added_by":"auto","created_at":"2021-10-26 21:12:19","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":57884,"visible":true,"origin":"","legend":"Time course of proceeded interventions. Baseline characteristics were assessed as shown in Table 2. AE: adverse events, NRS: numeric rating scale, PACU: postoperative anesthesia care unit, POD: postoperative day, RA: regional anesthesia, RSC: regular straight catheter group, SAE: severe ad-verse events, SCC: self-coiling catheter group.","description":"","filename":"Figure2Timecourseofproceededinterventions..png","url":"https://assets-eu.researchsquare.com/files/rs-959997/v1/5e42856104469713ab9a073b.png"},{"id":14924525,"identity":"68fd5977-de93-4f64-8f7c-d20cafa635b0","added_by":"auto","created_at":"2021-10-26 21:09:19","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1442784,"visible":true,"origin":"","legend":"Catheter position categories in the sonographic image. \na- perineural intrafascial position: catheter tip is located within the paraneural sheath indicated by sa-line bolus spread. b- 1st degree dislocation, also called perineural extrafascial: catheter tip is located outside the paraneural sheath but still close to the nerve. Saline bolus (red frame line) moisture the fascial paraneural sheath (yellow frame line) but run away into surrounding tissue. This category is also recorded as dislocated for evaluation since efficacy is decreased. c- 2nd degree dislocation, catheter tip is outside the paraneural sheath without proximity to the nerve. Saline bolus spreads dif-fuse within the biceps femoris muscle. White arrow- catheter, * - preferred correct position.\n","description":"","filename":"Figure3Catheterpositioncategoriesinthesonographicimage..png","url":"https://assets-eu.researchsquare.com/files/rs-959997/v1/3d054f5a50ad7be546181142.png"},{"id":14924526,"identity":"5c13c35a-ec2d-4b2a-8102-20b86ae59bc1","added_by":"auto","created_at":"2021-10-26 21:09:19","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":133958,"visible":true,"origin":"","legend":"Flow chart. 140 consecutive patients were enrolled in this trial. Patients got lost to follow-up only be-cause of earlier hospital discharge. No patient has withdrawn his consent. POD postoperative day, RSC regular straight catheter, SCC self-coiling catheter.","description":"","filename":"Figure4Flowchart..png","url":"https://assets-eu.researchsquare.com/files/rs-959997/v1/a0fb91c538033b9d0fad7bdf.png"},{"id":14924581,"identity":"94d67248-81ce-4487-a10b-fc698f381a32","added_by":"auto","created_at":"2021-10-26 21:12:19","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":114920,"visible":true,"origin":"","legend":"Postoperative pain scores. Values are given as mean ± standard deviation on numeric rating scale. Statistical significance was considered to be at two-sided p\u003c0.05. Differences between groups were analysed using Student´s t-test. NRS numeric rating scale, POD postoperative day, RSC regular straight catheter, SCC self-coiling catheter.","description":"","filename":"Figure5Postoperativepainscores..png","url":"https://assets-eu.researchsquare.com/files/rs-959997/v1/8b6c1c7edbb36b9151e6b41f.png"},{"id":14924522,"identity":"bf8c117f-e0ab-4d9a-8e74-7c092ddca13e","added_by":"auto","created_at":"2021-10-26 21:09:19","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":48974,"visible":true,"origin":"","legend":"Percentual cumulative dislocation rate of the catheters. A Chi-square test with multiple regression approach was performed. Statistical significance was accepted at p\u003c0.05. POD postoperative day, RSC regular straight catheter, SCC self-coiling catheter, * p\u003c0.05.","description":"","filename":"Figure6Percentualcumulativedislocationratesofthecatheters..png","url":"https://assets-eu.researchsquare.com/files/rs-959997/v1/0c1f4b4bc3851488b2f64fbe.png"},{"id":14924524,"identity":"0f32d6cf-cb7e-4849-ab76-d55b0dac72a6","added_by":"auto","created_at":"2021-10-26 21:09:19","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":187048,"visible":true,"origin":"","legend":"Mean values of NRS assessment as a function of time for the different catheter types and dislocation categories in situ. NRS numeric rating scale, POD postoperative day, RSC regular straight catheter, SCC self-coiling catheter.","description":"","filename":"Figure7MeanvaluesofNRSassessmentofbothcathetertypesasafunctionofpositioninsitu..png","url":"https://assets-eu.researchsquare.com/files/rs-959997/v1/9e6c1d92677489c5e034ca23.png"},{"id":14924582,"identity":"b1260981-e200-4988-9d93-9cd4a39c3971","added_by":"auto","created_at":"2021-10-26 21:12:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1251716,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-959997/v1/f86e7bde-257d-4759-bf0a-0d381ba14368.pdf"}],"financialInterests":"Competing interest reported. OV performs consulting services and receives lecture honoraria from Pajunk, Geisingen, Germany and Sintetica GmbH, Muenster, Germany. All other authors declare that they have no competing interests.","formattedTitle":"\u003cp\u003eImpact of Self-Coiling Catheters for Continuous Popliteal Sciatic Block on Postoperative Pain Level and Dislocation Rate: A Randomized Controlled Trial\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cp\u003eContinuous nerve blocks play an integral role in modern multimodal analgesia concepts [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Regional anesthesia is essential in orthopaedic and trauma surgery on the lower limb [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. For both, the lower and upper extremities, randomized controlled trials have shown significant pain reduction by means of continuous regional anesthesia after surgery [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. This also results in less chronic pain, a lower opioid requirement and associated side effects such as nausea, vomiting, constipation and fatigue [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, in some studies analgesic advantages of continuous regional anesthesia fade after 24- 48 h [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The secondary failure rate of indwelling regional anesthesia catheters has been reported in literature up to 40 % [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Aside from initial misplacement secondary catheter dislocation during the postoperative course might be considered one possible explanation for the worsened efficacy of continuous regional anesthesia [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Secondary dislocation is commonly defined as outwardly visible displacement or sliding out of the catheter, partly accidently by the patient himself [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. However, regarding dislocations, the rare event of external dislodgement at the insertion site has to be distinguished from internal catheter tip migration away from target structure or nerve surrounding compartment due to active and passive movement of adjacent muscles. The latter problem might be underestimated since pain scores, opioid consumption, sensory block distribution and patient\u0026acute;s satisfaction serve only unreliable surrogate measures for correct catheter position. Investigation of internal dislocations by direct visualization of the catheter tip or better by imaging of fluid spread referred to the nerve has been addressed only in a few studies with limited number of patients [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Two more studies have investigated dislocation rate in situ, either solely in healthy volunteers [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] or in human cadavers [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Stiff catheters placement using the most popular short axis (SAX) / in-plane (IP) approach might bear an increased risk of internal dislocations [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] since the catheter mostly can be placed only a short distance beyond the needle tip to avoid bypassing the nerve [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFor a new catheter design it has been shown a very low risk of initial misplacement in cadavers for paravertebral blockades as well as sciatic nerve blockades [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] due to a 2.5 cm long self-coiling soft end of the catheter remaining close to the nerve. However, so far, no studies have investigated if self-coiling catheters are also more resistant to secondary dislocations with consecutive improvement of pain management in surgical patients.\u003c/p\u003e \u003cp\u003eTherefore, we compared the self-coiling catheter with regular straight catheters for continuous popliteal sciatic blockade regarding efficacy and position change within and outside the tissue.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design\u003c/h2\u003e \u003cp\u003eThis study is a prospective, randomized controlled, single-centre trial in a clinically interventional design.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEthics\u003c/h2\u003e \u003cp\u003e Positive ethic votum was approved by the Institutional Review Board of the Technische Universit\u0026auml;t Dresden (EK150042016). Written informed consent was obtained from all patients. This study is registered at the German Clinical Trials Register (DRKS00020938) and is reported according to the CONSORT guidelines 2010 [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003ePatients and randomisation\u003c/h2\u003e \u003cp\u003e140 adult patients scheduled for continuous regional anesthesia with popliteal sciatic catheter as part of elective major surgery on the ankle or foot in the University Hospital Carl Gustav Carus at the Technische Universit\u0026auml;t Dresden, were enrolled between 09/2016 and 12/2017 for this trial. The applied inclusion and exclusion criteria are summarized in Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Randomisation was carried out immediately before catheter insertion by means of sequentially numbered sealed opaque envelopes, containing the study number and corresponding reference to the respective group. Patients were assigned to two groups: an interventional group with the application of the self-coiling catheter, SCC, (SonoLong Curl Echo 20 G 100 mm, Pajunk medical products, Geisingen, Germany) and a control group receiving the regular straight catheter, RSC, (SonoLong Sono 20 G 100 mm, Pajunk medical products, Geisingen, Germany) for popliteal sciatic block (figure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Surgeons, nurses, patients and members of the acute pain service and investigators apart from the anesthetists inserting the catheter were blinded to the study group. Investigators collecting data were not blinded to groups.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eInclusion and exclusion criteria\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInclusion criteria\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eExclusion criteria\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026minus; age between 18 and 75 years\u003c/p\u003e \u003cp\u003e\u0026minus; indication for the application of a distal sciatic catheter within the scope of an elective surgical procedure\u003c/p\u003e \u003cp\u003e\u0026minus; patient consent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus; patient suffering from chronic pain before surgery\u003c/p\u003e \u003cp\u003e\u0026minus; polyneuropathy or ipsilateral neuropathy, involving the lower limb\u003c/p\u003e \u003cp\u003e\u0026minus; refusal of regional anesthesia\u003c/p\u003e \u003cp\u003e\u0026minus; patient not legally competent\u003c/p\u003e \u003cp\u003e\u0026minus; intolerance or allergy to ropivacaine or oxy-codone\u003c/p\u003e \u003cp\u003e\u0026minus; neuromuscular diseases\u003c/p\u003e \u003cp\u003e\u0026minus; BMI \u0026gt;35\u0026nbsp;kg/m\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e\u0026minus; pre-existing opioid medication\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eApplication of regional anesthesia\u003c/h2\u003e \u003cp\u003ePatients were placed in supine position with the relevant leg elevated. After generous skin disinfection (ChloraPrep, Becton, Dickinson and Company, Franklin Lakes, USA) the area was covered with a sterile fenestrated sheet. The transducer was draped with a sterile ultrasound probe cover (CIV-Flex\u0026reg; Transducer Covers, Civco Medical Solutions, Kalona, Iowa, USA).The sciatic nerve was visualized from the posterior thigh in short axis view (SAX) at the level of the popliteal nerve bifurcation with a 4-12 MHz linear probe (L12-4) of a Philips Sparq or Philips Affiniti 70G ultrasound system (Philips Healthcare, Andover, Massachusetts, USA) or 5- 13 MHz linear probe (12L-RS) of a GE Logiq e ultrasound system (GE Healthcare, Milwaukee, Wisconsin, USA). Nerve bifurcation was defined as the most proximal point where the tibial and common fibular nerve clearly started to detach. After skin infiltration with 2-4 ml prilocaine 1 %, an 18 G Tuohy needle was advanced using an in-plane technique from lateral until the needle tip was located within the paraneural sheath. The designation of the sheaths of the sciatic nerve is referred to the previous publication of Andersen and colleagues [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Special care was taken not to touch the nerve or even puncture the epineurium. An initial bolus of 20 ml ropivacaine 0.5 % (Naropin 10 mg/ml, Astra Zeneca, London, UK) was applied directly via the injection line connected to the Tuohy puncture cannula under direct sonographic control. The desired spread of local anesthetic was circularly around both components of sciatic nerve within the paraneural sheath. If diffuse spreading into the surrounding tissue occurred, the cannula position was corrected. Afterwards, the previously randomized catheter was placed adjacent to the sciatic nerve within the paraneural sheath through the cannula. According to manufacturer instructions SCC was advanced approximately 2.5-3 cm beyond the needle tip to facilitate the coiling up of the distal catheter end. RSC was inserted approximately 3-4 cm past the needle tip. Subsequently proper catheter position was sonographically confirmed by observing the spread of a 2 ml bolus of saline injected via the catheter within the paraneural sheath. In case of spread outside of paraneural sheath catheter was retracted under real-time sonographic guidance until the injected saline bolus was reliably distributed around the nerves. Thereafter the catheter was connected to the associated bacterial filter and fixed with sterile wound suture strips (Omnistrip\u0026reg;, Fa. Paul Hartmann AG, Heidenheim, Germany). Finally, a sterile foil dressing (IV3000 10x12 cm, Smith \u0026amp; Nephew Medical Ltd., London, UK) was used to provide fixation of the catheter additionally. All catheters were placed as a part of the clinical anesthesia routine by a total of four senior anesthesiologists with substantial experience in performing ultrasound-guided popliteal sciatic nerve block. The success of the sciatic blockade was evaluated in all patients by testing warm-cold differentiation in the innervation area.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003eAdditional anesthetic procedures and hemodynamic monitoring\u003c/h2\u003e \u003cp\u003eThe time course of proceeded interventions were summarized in figure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. After arriving in the operating area, peripheral venous access with an infusion of a balanced crystalloid solution, a 3- or 5-lead ECG monitoring including ST-segment analysis, a pulsoxymetry and non-invasive blood pressure measurement were established. Hemodynamic data were continuously recorded using a Philips Intellivue MP 70 (Philips Medicine Systems GmbH, Hamburg, Germany). If surgery involved the medial area of the lower leg, ankle or foot, an additional ultrasound guided saphenous nerve block was performed with 10 ml ropivacaine 0.5 % (Naropin 10 mg/ml, Astra Zeneca, London, UK) via an 80 mm 22 G Sonoplex cannula (Pajunk medical products, Geisingen, Germany) at femoral triangle by SAX view and in-plane approach. Further anesthesia procedures were based on the individual risk profile, patient\u0026acute;s comfort request and needs due to planned surgery procedures like tourniquet at the thigh. Independent of the randomization, in addition to the continuous peripheral sciatic blockade the following procedures were used: anesthesia standby, sedation, femoral and obturator nerve block and spinal or general anesthesia. For spinal anesthesia 2 to 2.4 ml of hyperbaric bupivacaine 0.5 % (Bucain hyperbar 5mg/ml, PUREN Pharma GmbH \u0026amp; Co. KG, Munich, Germany) with 10 \u0026micro;g fentanyl via a 25 G Sprotte cannula (Pajunk medical products, Geisingen, Germany) was used. Sedation was applied by use of propofol 20mg/ml (Fresenius Kabi Deutschland GmbH, Bad Homburg, Germany) with a rate of 1-2 mg/kg/h. General anesthesia was induced and maintained with propofol (Propofol 1 % and Propofol 2 %, Fresenius Kabi Deutschland GmbH, Bad Homburg, Germany) and sufentanile (Sufentanil-hameln 5 \u0026micro;g/ml, hameln pharmaceuticals gmbh, Hameln, Germany). The airway was secured by laryngeal mask (Ambu\u0026reg; AuraGain\u003csup\u003eTM\u003c/sup\u003e, Ambu GmbH, Bad Nauheim, Germany).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003ePostoperative procedure and outcome parameter assessment\u003c/h2\u003e \u003cp\u003eAfter surgery, the patients were observed under cardiovascular monitoring in post anesthesia care unit, as appropriate. Afterwards they were transferred to general ward. Postoperatively, both groups received a continuous application of ropivacaine 0.2 % (Naropin 2 mg/ml, Astra Zeneca, London UK) at an initial rate of 6 ml/h. According to a multimodal pain management concept, all patients received oral ibuprofen 600 mg as basic analgesia every eight hours. In case of contraindications for ibuprofen, novamine sulfone (1 g every six hours) was administered as an alternative per os or intravenously. A pre-existing basic analgesia with novamine sulfone and ibuprofen, in the above-mentioned dosages, was maintained postoperatively. The patients were regularly visited by the acute pain service from the first post-operative day (POD) twice a day. Pain service visit included surveillance of infection signs, leakage and external dislocation at insertion site. In order to record the subjective pain level of the patient twice a day the numerical rating scale (NRS 0-10) was used as a semi-quantitative method. The first interview was conducted two hours after the end of the operation. The NRS, the spread of the sciatic blockage and any adverse events were recorded. For rescue pain (NRS\u0026gt;3) either, a manual bolus of 10 ml ropivacaine 0,3 % (Naropin, Astra Zeneca, London, UK) could be applicated by acute pain service staff or patients received oxycodone 10 mg (Oxygesic akut 10 mg, Mundipharma GmbH, Limburg, Germany) per os by ward nurses. The total daily requirement of ropivacaine and total oxycodone consumption was recorded.\u003c/p\u003e \u003cp\u003eThe position of indwelling catheters were revealed immediately after surgery at the PACU and daily on the first, second and third POD. For this purpose, distribution of a saline a bolus of 2- 8 ml via the catheter was observed under sonographic view with respect to the nerve and the adjacent paraneural sheath. Corresponding images were digitally stored and the detected position was documented. Three different positions of the catheter in relation to the nerve were categorized as depicted in figure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. In case of catheter dislocation, no further US-guided examinations were performed afterwards.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003eSafety thresholds\u003c/h2\u003e \u003cp\u003eParticipation in the trial was terminated at any time, if one of the following dropout criteria was fulfilled: request of the patient, allergic reaction to ropivacaine, novamine sulfone or ibuprofen, necessity of second operation during the follow up period.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003ePrimary and secondary outcomes\u003c/h2\u003e \u003cp\u003eThe primary outcome was the individual postoperative pain intensity, assessed with the numerical rating scale (NRS) after surgery on the lower leg or foot in the first 72 hours. The patient classified the pain on a scale from 0 to 10. The following issues were identified as secondary outcomes: additional need for systemic opioids, rate of secondary dislocations within the tissue and dislocations and leakage at the injection site.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eThe sample size was calculated as followed. To demonstrate a clinically relevant difference of 1 level on an NRS of 0 to 10, a minimum of 64 patients were enrolled with a standard deviation of 2, a significance level of 0.05 and a power of 80 %. A drop-out rate of 8 % was expected. Therefore, 70 patients per group were included. In accordance with the case number planning, the evaluation was carried out with an unpaired two-sided Student\u0026acute;s t-test at 5 % level, assuming equality of variance. The distribution of continuous parameters was described by using of mean value and standard deviation (normally distributed) or by medians and quartiles. Categorical parameters were described by their absolute and relative frequencies, and differences between groups were examined using the Chi- square test according to Pearson or the exact test according to Fisher. Two-group comparisons of metric scaled variables were performed by independent two-sided t-tests after using Levene test checking equality of variances. To analyse the influence of possible covariates of respective baseline data, a covariance analysis was calculated to adjust for possible group differences for confounders. To correlate nominal and metric parameters, eta correlation coefficient was calculated. Statistical significance was considered at two-sided p \u0026lt;0.05.\u003c/p\u003e \u003cp\u003eAll calculations and graphs were performed and computed using SPSS (IBM SPSS Statistics Vers. 25, IBM Deutschland GmbH, Ehningen, Germany).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eFrom 09/2016 to 12/2017 1021 patients undergoing elective ankle or foot surgery were screened and\u003c/p\u003e \u003cp\u003e140 patients were enrolled in this study (figure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Both groups were comparable regarding baseline\u003c/p\u003e \u003cp\u003echaracteristics as depicted in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The study was closed after enrolment of the planned 140 patients.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBaseline characteristics.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRSC Group (n=70)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSCC Group (n=70)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge [years]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50\u0026plusmn; 14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u0026plusmn; 13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender [no/%]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37 (53)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e37 (53)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33 (47)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33 (47)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody height [cm]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e171.7\u0026plusmn; 9,0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e173.1\u0026plusmn; 10.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody weight [kg]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e76.5\u0026plusmn; 13.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e79.3\u0026plusmn; 16.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI [kg/m\u003csup\u003e2\u003c/sup\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.9\u0026plusmn; 3.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26.3 \u0026plusmn; 4.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eASA [no./%]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38 (54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35 (50)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27 (39)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33(47)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgical area\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUpper ankle joint\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35 (50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e41 (59)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCalcaneus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8 (11)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14 (20)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHallux\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 (9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTalus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMetatarsal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (10)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTendons/syndesmosis\u003c/p\u003e \u003cp\u003eof the ankle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eValues are given as absolute number (percentage) or mean (\u0026plusmn; standard deviation), as appropriate. \u003cem\u003eASA\u003c/em\u003e American Society of Anesthesiology physical status, \u003cem\u003eBMI\u003c/em\u003e Body mass index, \u003cem\u003eRSC\u003c/em\u003e regular straight catheter, \u003cem\u003eSCC\u003c/em\u003e self-coiling catheter\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eCatheter placement and additional anesthetic procedures\u003c/h2\u003e \u003cp\u003eSonographic identification of the nerve and bifurcation was successfully possible in all patients. The mean performance time acquired for catheter placement was 12.9\u0026plusmn; 4.3 min (p=0.97) in both study groups. The catheter placement was successful in all patients indicated by the correct local anesthetic distribution within the paraneural sheath of the sciatic nerve and complete loss of sensory and motoric function in the supplied nerve territory. As shown in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, there was no statistic significant difference in duration of surgery and initial amount of administered ropivacaine. No difference between groups were detected regarding the number of additional saphenous nerve blocks and other additional anesthetic procedures as well as to the usage of postoperative basic analgesic medication.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAdditional anesthetic procedures, duration of catheter placement and surgery, postoperative basic analgesic medication, ropivacaine consumption and leakage.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRSC Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSCC Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSaphenous nerve block\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e64 (91.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e56 (80)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAdditional anesthetic procedure [no/%]\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGeneral anesthesia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e53 (75.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60 (85.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpinal anesthesia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 (8.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemoral nerve and obturator nerve block\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (2.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnalgosedation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (8.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (2.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003enone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1(1.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDuration of catheter placement [min]\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.9\u0026plusmn; 4.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.9\u0026plusmn; 4.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDuration of surgery [min]\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e94.4\u0026plusmn; 41.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e96.2\u0026plusmn; 39.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePostop. analgesic medication [no/%]\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIbuprofen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e46 (65.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55 (78.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNovamine sulfone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19 (27.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13 (18.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIbuprofen+ Novamine sulfone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (7.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (2.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRopivacaine consumption [mg/ 24h]\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e283.8\u0026plusmn; 34.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e288.7\u0026plusmn; 10.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e264\u0026plusmn; 112.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e233\u0026plusmn; 101.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e108\u0026plusmn; 124.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e127.5\u0026plusmn; 116.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23\u0026plusmn; 84.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e52.1\u0026plusmn; 93.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLeakage [no/%]\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8 (11.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 (8.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.83\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22 (31.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21 (30)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.84\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21 (30)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22 (31.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (4.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 (12.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eValues are given as absolute number (percentage) or mean (\u0026plusmn; standard deviation), as appropriate. Difference between groups were tested with Chi-square test or two-sided Student\u0026acute;s t-test with statistical significance considered at p\u0026lt;0.05, \u003cem\u003ePOD\u003c/em\u003e postoperative day, \u003cem\u003eRSC\u003c/em\u003e regular straight catheter, \u003cem\u003eSCC\u003c/em\u003e self-coiling catheter.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003ePrimary outcome parameter- postoperative pain level\u003c/h2\u003e \u003cp\u003eThe pain levels recorded daily over the observation period are depicted in figure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The NRS scores did not differ significantly on the day of surgery (p=0.69). On POD 1 and POD 2, patients of SCC group showed significantly less pain than those in the RSC group. There was no difference in pain intensity between both study populations on POD 3.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003eSecondary outcome parameters\u003c/h2\u003e \u003cdiv id=\"Sec16\" class=\"Section4\"\u003e \u003ch2\u003eOpioid consumption\u003c/h2\u003e \u003cp\u003eThe values of oxycodone consumption determined showed a wide spread and are summarized in Table \u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. All mean values of the oxycodone consumption are lower with the self-coiling catheter than with the conventional catheter. Significant differences between both groups were found on the day of surgery (p=0.04), POD 2 (p=0.03) and POD 3 (p=0.04). For POD 1 (p=0.19) a tendency in lower oxycodone consumption have been observed.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eOxycodone consumption of both study groups during study period.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRSC Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSCC Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDaily Oxycodone consumption (mg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.29\u0026plusmn; 4.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.14\u0026plusmn; 1.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.04*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.57\u0026plusmn; 19.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.71\u0026plusmn; 15.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.19\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.50\u0026plusmn; 14.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.57\u0026plusmn; 11.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.03*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOD 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.94\u0026plusmn; 8.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.92\u0026plusmn; 7.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.04*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eValues are given as mean (\u0026plusmn; standard deviation). Statistical significance considered at p\u0026lt;0.05 (*). \u003cem\u003ePOD\u003c/em\u003e postoperative day, \u003cem\u003eRSC\u003c/em\u003e regular straight catheter, \u003cem\u003eSCC\u003c/em\u003e self-coiling catheter.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003eDislocation\u003c/h2\u003e \u003cp\u003eThe spread of fluid could be detected in all sonographic examinations, which were performed throughout the study. Dislocation rates are shown in figure \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The majority of dislocations were found already after the surgical procedure and patient transfer to PACU. However, the dislocation of catheter was significant lower in the SCC group. (RSC n=19 vs. SCC n=1, p\u0026lt;0.01). Over the entire observation period, the SCC-cohort catheters dislocated less frequently than in the RSC group (p\u0026lt;0.01 for POD 1 \u0026amp; 2, p=0.01 for POD 3, respectively). The cumulative dislocation rate was 60 % (n=42) in RSC group and 14.3 % (n=10) in SCC group. For the first and second postoperative day, a significant influence of dislocation on the mean indicated NRS value could be demonstrated (POD 1 p\u0026lt;0.01; POD 2 p\u0026lt;0.01) as shown in figure \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003eCatheter insertion depth\u003c/h2\u003e \u003cp\u003eThe puncture depth of both catheter groups did not differ significantly (p = 0.169) and averaged 5.8 (RSC) and 6.0 cm (SCC). However, the distance between the puncture depth and the final skin level of the catheters differed due to catheter design. The self-coiling catheters were placed at a mean of 2.4 cm above the final needle tip position. For the regular catheter, this value was 1.6 cm (p\u0026lt;0.01). No catheter in either group with an insertion depth greater than/equal to 3.5 cm dislocated in this study. The eta coefficient was 0.380 (p\u0026lt;0.01), resulting in a moderate correlation. Hence, 14.4 % of the dislocation variance can be explained by the insertion depth.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003eExternal movement at the insertion site\u003c/h2\u003e \u003cp\u003eThe outwardly visible movement of the pain catheters was documented daily. In contrast to the dislocation within the tissue, no significant difference between both groups could be detected over the entire observation period regarding the externally visible position at the insertion site (POD 0, p=0.86; POD 1, p=0.39; POD 2, p=0.65). In total, 7 (10 %) of the self- coiling catheters and 9 (12.9 %) of the regular straight catheters slipped back at least 1 cm or further (p=0.6). We could not observe any differences between correctly positioned and dislocated catheters regarding the outward movement of the catheters.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003eLeakage\u003c/h2\u003e \u003cp\u003eOverall, leakage of the puncture sites was most frequently detected on the first and second postoperative day. We observed no significant differences in characteristics between the SCC and RSC group (POD 0, p=0.83; POD 1, p=0.84; POD 2, p=0.6; POD 3, p=0.07) as seen in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section3\"\u003e \u003ch2\u003eComplications due to perineural catheter\u003c/h2\u003e \u003cp\u003eEight patients (5.7 %) experienced minor local inflammation at the insertion site, which was utterly subsiding after removal in the further course of the trial. Because of catheter occlusion, one catheter in each study group (0.7 %) could no longer be used from the first and second postoperative day. One patient in the RSC group complained of a metallic taste and nausea after increasing the infusion rate of ropivacaine from 6 to 8 ml/h Ropivacaine 0.2 % and administration of a bolus. The catheter was then removed immediately and all symptoms were completely regressed within a few hours. No neurologic deficit occurred during the observation period.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this investigator-initiated randomized controlled trial it could be demonstrated that the use of a self-coiling catheter compared with a regular straight catheter for continuous popliteal sciatic block was more effective in terms of pain management and dislocation rate within the tissue. The latter appeared without visible external changes measured by leakage and external dislodgement of the catheter at the insertion site. The higher stability of the self-coiling catheter in its original positioning may result in lower pain levels on the first and second POD and a reduced opioid consumption compared to patients in the RSC group. To our knowledge this is the first trial investigating impact of different catheter characteristics on secondary dislocations and advantages of a self-coiling catheter for peripheral nerve block in clinical practice.\u003c/p\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003ePain intensity\u003c/h2\u003e \u003cp\u003eDislocation rate on the day of operation had no impact on pain levels because initial bolus of ropivacaine 0.5 % caused a long-lasting blockage of pain perception in both groups. Long acting ropivacaine provides nerve block duration of up to 18 hours, depending on dose and proximity of applied LA to the nerve. Christiansen et al. described a mean duration of action for distal sciatic blocks of more than 13 hours with a lower dose of 60 mg ropivacaine [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. In this study 100 mg were administered. Various other studies have reported similar results. Several investigators compared a single popliteal block of the sciatic nerve with a continuous application of local anesthetic via catheter and determined no significant differences in pain intensity on the day of surgery for both groups [\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The effect of the initially performed nerve block was effective in both groups and thus did not result in NRS-differences.\u003c/p\u003e \u003cp\u003eThe significance of the lower pain level of the SCC group on the first and second POD showed a measurable difference of 0.7 points on NRS to the control group. Even if this difference seems to be small, it can become relevant for the individual patient. The reason for the higher pain scores in the RSC group on POD 1 and 2 may be related to a higher dislocation rate outward of the fascial space of the sciatic nerve. Thus, a lower effective dose of continuous infused ropivacaine could act on the sciatic nerve. In contrast, the lack of difference on POD 3 might be explained by spontaneous pain relief in the late postoperative period.\u003c/p\u003e \u003cp\u003eWith the diminishing effect of the initial bolus of ropivacaine 0.5 % on the first postoperative day, the average pain level of all participants was highest compared to the other measure points. This might be caused by dislocations of indwelling catheters, insufficiency of lower continuous ropivacaine dose and pain perception in the regions not supplied by sciatic nerve when single shot of supplemental regional anesthesia had worn off. The latter issue is relevant if medial parts of the foot were involved in surgery and saphenous or femoral nerve block was established [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Pain perception in sensory territory of the saphenous nerve might have contributed to levelling pain intensity scores and scattering intergroup differences regarding perineural sciatic nerve catheter performance. Using an additional catheter for the saphenous nerve might have decreased pain scores and additional opioid use. However, reports about impact of the continuous or prolonged saphenous nerve block on pain after ankle surgery are conflicting. Whereas Fisker et al could not find advantage of continuous saphenous nerve block compared to single shot [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Jarell et al. showed lower pain scores and less opioid need with continuous block of saphenous nerve after ankle surgery [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Another investigator reported improved postoperative pain management with prolonged saphenous nerve block by additional perineural dexamethasone [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSurgery of the distal lower extremity or the foot has shown to be one of the most painful surgical interventions. In almost 71,000 patients with 179 different operations in all areas of the body, the calcaneus operation was revealed to be the most painful operation with a mean postoperative NRS of 6.68 on the first postoperative day. Other operations on the foot, forefoot or ankle were among the most painful fifteen operations with a mean NRS of at least 6 on the first postoperative day [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. This underlines the importance of continuous regional anesthesia of the ankle and foot.\u003c/p\u003e \u003cp\u003eIn our study almost, all patients were free of pain on POD 0. In the further course, all mean NRS values in both cohorts remained at all examination times below 3.5 but only patients with self-coiling catheters performed with mean NRS 2.7 even lower than the commonly accepted intervention threshold of NRS 3.\u003c/p\u003e \u003cp\u003eThe absence of ultrasound-guidance and confirmation of proper catheter location, differently used local anesthetics and additional analgetic drugs, the heterogeneity of surgical procedures and the lack of information about mobilization strategies, complicate comparability with other studies. However, most studies show maximum pain intensity on POD 1 [\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Similar to our results, usually pain level decreases day by day in the further course. The pain intensity of patients with continuous sciatic nerve block varied between 0 and 4 on POD 1. Our results are in this range. Many of the studies mentioned above had an outpatient setting which may be another reason for the fluctuation range in reported pain intensity. Patients were discharged with the peripheral nerve catheters on the day of surgery and received defined amounts of analgetics as well as instructions for mobilisation. Previous surgery, the duration and length of stay in hospital varied greatly or were not specified. The indicated operation times were very heterogeneous and ranged from 32 min [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] to 110 min [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. That may have an impact on surgical trauma and consequently on pain intensity. The evaluation of pain and other criteria in the following days was conducted by telephone. As a result, it could not be clearly elucidated whether patients' statements are reliable and how mobilisation was carried out as additional pain stimulus.\u003c/p\u003e \u003cdiv id=\"Sec24\" class=\"Section3\"\u003e \u003ch2\u003eOxycodone consumption\u003c/h2\u003e \u003cp\u003ePatients in the self-coiling catheter group had a lower need for oxycodone in the first three days after surgery. While the lower consumption of oxycodone in the SCC group differed by 1.1 mg from the RSC group on the day of surgery, already on POD 1 the consumption was 3.9 mg lower. This difference in lower consumption in the SCC group reached significant levels at the day of surgery, POD 2 (4.9 mg) and POD 3 (3 mg), with an overall decrease in the need for additional opioids already from the second postoperative day on. Interestingly, the significant elevated pain intensity in the RSC group did not reach the level to create a difference for opioid consumption on POD 1.\u003c/p\u003e \u003cp\u003eTwo facts might have influence accuracy of discrimination. First, we used a single prefixed dose of oxycodone 10 mg as rescue pain medication obeying our institutional multimodal pain concept. Therefore, discriminatory power regarding additional opioid need was low. Assumably, with lower opioid bolus provided by patient controlled intravenous analgesia we could have traced the opioid requirement more precisely. Second, over 50 % of patients in both groups had surgery that involved also innervation territory of saphenous nerve. Despite reliable sciatic nerve block, the fading effect of the single shot saphenous nerve block might have caused pain at the medial aspect to the ankle and foot and consequently might have led to elevated opioid consumption on POD 1. Thus, we could not distinguish, if opioid request was referred to poor catheter performance or terminated saphenous nerve block. However, the number of saphenous nerve blocks applied was not different between both catheter groups. Overall, the amount of opioid consumption in the present study is consistent with previous studies investigating continuous sciatic nerve block for foot and ankle surgery [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e \u003ch2\u003eAdditional anesthesia procedures\u003c/h2\u003e \u003cp\u003eA further aspect of the discussion is the possible influence of additional anesthetic procedures on postoperative pain intensity. Most patients (80.7 %) underwent adjunct general anesthesia, whereas 11.4 % received additional spinal anesthesia to the distal sciatic block. Sedation or additional peripheral regional anesthesia was given to the remaining 7.9 %. The choice of procedure was individually adapted to the comorbidities and patients request. Due to randomisation and group size there were no significant differences regarding the distribution between of additional anesthetic procedures between both groups, hence a possible influence might be negligible in this investigation. The question of whether spinal anesthesia has an influence on the postoperative pain level has not been conclusively clarified until now. YaDeau et al. compared general and spinal anesthesia, each in combination with PNB for operations on the ankle and foot in a recent randomised controlled trial. A significant difference of pain scores in favour of spinal anesthesia was found only one hour after the end of the operation [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. In contrast to long acting morphine we used fentanyl as intrathecal supplemental opioid for spinal anesthesia. Thus, any effect on pain intensity beyond first 12 hours seems unlikely.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section3\"\u003e \u003ch2\u003eCatheter orifices\u003c/h2\u003e \u003cp\u003eWe compared in the present study a self-coiling catheter with a closed tip and six lateral microholes with a regular straight catheter that has only a single orifice at the end. One might question if this could have influenced our results. Fredrickson et al. investigated the outflow of injected fluid on catheters with a different number of orifices. They showed a dependency of the fluid spread pattern on the fluid flow rate. Below 80 ml per hour, fluid left multi-orifice catheters only on the most proximal orifice [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Only an injection rate over 100 ml per hour delivered all microholes. Considering our study\u0026acute;s flowrate of local anesthetics of 6- 10 ml per hour, the self-coiling catheter likely functioned rather as a single orifice catheter. Thus, we do not expect any relevant advantage of the multiple catheter orifice configuration in the present study. Moreover, considering that the SCC had been positioned only 2.4 cm into the target space within the perineural facial sheath, with continuous infusion the local anesthetic may have left the most proximal orifice only missing the target space partially if the catheter gets retracted by muscle movements. Clinical data regarding the influence of catheter orifice design on quality of pain management is conflicting, despite LA bolus application was used. Consequently, it can be concluded that catheters with multiple openings, such as the SCC, also function like conventional end-hole catheters at clinically relevant infusion rates. In this study there was a maximum continuous flow rate of 10 ml per hour. Only bolus applications by the acute pain service were probably applicated at speeds above 100 ml per hour. Since this injection was performed manually from a 10 ml syringe, no more precise statements can be made here about the application speed [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section3\"\u003e \u003ch2\u003eDislocation rate\u003c/h2\u003e \u003cp\u003eDespite the widespread use of continuous regional anesthesia the topic of perineural catheter dislocation is not well elucidated, neither in studies nor in clinical practice. Thus, the results of our study provide new insights regarding factors contributing to catheter dislocation. To our best knowledge, there is no clinical study investigating dislocation rate of self-coiling catheters compared to regular catheters so far. Luyet et al had shown a decreased initial misplacement rate for self-coiling catheters in human cadavers. However, the cadaver study design did not address dislocation rates in the further course [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSignificantly fewer self-coiling catheters (14 %) slipped out of the subparaneural target space during the study period than regular catheters with straight ends (60 %). This significant difference might be caused by different insertion distances within the perineural fascia sheath. Ilfeld et al. [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] and Steffel et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] described a higher dislodgement rate for lower insertion distance at the nerve. We used a regular straight catheter with an indwelling metal wire in the control group. Such firm catheters often pass the target structure and protrude out of the perineural fascia sheath during initial insertion of around 3 cm beyond the needle tip, especially if catheters are advanced in-plane perpendicular to the SAX imaged nerve. Thus, we had to adjust the catheter by retraction until LA injection was distributed well within the perineural fascia sheath under sonographic view. The self-coiling catheter provide a more reliable initial placement without passing the target space if the insertion distance of 3 cm beyond the needle tip is not exceeded using an in-plane approach [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Thus self-coiling catheters require less likely a withdrawal due to initial misplacement and have a longer catheter segment remaining around the target structure.\u003c/p\u003e \u003cp\u003eFor postoperative evaluation of catheter position and initial confirmation of correct catheter placement we used sonographic imaging of saline bolus via the catheter. Although the efficacy of continuous regional anesthesia is depending on proper catheter location, assessment of catheter position is still not a common procedure neither in studies nor in clinical routine [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Postoperative break through pain and need of additional systemic analgesic medication are often considered surrogate markers for insufficient catheter performance due to any reason. However, this concept is misleading to prove an incorrect catheter position. It has to be considered that the visualization of catheter position is often compromised by sterile dressing and swollen tissue in the affected area.\u003c/p\u003e \u003cp\u003eSeveral methods for visualization of catheter position have been described in the literature, a.e. imaging of injected fluid (either saline, LA, or contrast medium) or air spreading out of catheter orifice or direct visualization of the catheter [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan additionalcitationids=\"CR41\" citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Imaging techniques include high resolution ultrasound (HRUS), computer tomography (CT), or magnetic resonance imaging (MRI) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. There are pros and cons of each technique that we would like to discuss briefly. We decided for the injection of saline to prove catheter tip position because it is a safe and straightforward method that is part of our daily clinical routine. Moreover, it avoids unnecessary local anesthetic doses and harm to vulnerable structures nearby. The use of air or agitated fluid with microbubbles may enhance contrast and visualization of the injectate. However, spreading air within the tissue decreases markedly sonographic imaging quality of the target structure and surrounding tissue by scattered ultrasound waves. In contrast, visualization of saline via the catheter is similar to common procedure of observing local anesthetic injection via the cannula. Finally, direct visualization of the catheter is less favourable. On the one hand, despite the improved echogenity of catheters they hardly alignm with the ultrasound beam plane like a firm needle. This issue is aggravated by the use of self-coiling catheters. On the other hand, according similar to the injection over needles, control of spread of LA around the target structure is more important for a reliable block success than the catheter tip position itself. Compared to CT and MRI high resolution ultrasound imaging is commonly available. HRUS is a real point of care technique that can be applied as often as desired by the anesthesiologist avoiding unnecessary patient transports and staff expenses. Furthermore, CT examination exposes patients to radiation burden.\u003c/p\u003e \u003cp\u003eIn our study the most dislocations were discovered after arrival at the PACU. It can be assumed that passive and/or active movement of the thigh musculature occurs when the patient is positioned prior to surgery or during patient transfer to bed. This causes mechanical traction to the catheter within the biceps femoris muscle pulling the catheter back outward of the target space within the nerve-surrounding fascia.\u003c/p\u003e \u003cp\u003eThe dislocation rate within tissue was 14 % for the self-coiling catheter or 60 % for the regular straight catheter. Marhofer et al. examined the dislocation rates within the tissue in healthy volunteers. They determined a dislocation rate after movement of 25 % and 5 % for perineural femoral and interscalene catheter [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In contrast to our investigation, catheters were only examined for six hours after insertion. In addition, both catheters were placed using the out-of-plane technique, which is more robust against dislocation [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOnly two studies address internal dislocation rates for continuous popliteal sciatic nerve block. Steffel et al. compared a catheter-over-needle (CON) with a conventional catheter-through-needle (CTN) technique in human cadaver [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. 27 % of the CON catheters dislocated from the fascial sheath of the sciatic nerve. In contrast, all conventional catheters remained perineural. Remarkably, Steffel et al. did not evaluate the spread of the local anesthetic, but only visualized sonographically the suspected end of the catheter in the sonography. However, LA spread around the target is the decisive determinant for a sufficient nerve block. Comparisons with our study are difficult, since only a tiny cohort of 30 persons was involved and the tissue characteristics of the body donors cannot be considered identical to those of living subjects [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. In contrast to our patients, only passive flexion movements were performed on the body donors. However, we believe that an active contraction and relaxing of the muscle contributes considerably to the movements of the catheter within the tissue. Hauritz and colleagues compared two different approaches for popliteal sciatic blockade, regarding dislocation within the tissue. They confirmed catheter location 48 h after application by means of an MRI contrast bolus [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Whereas a dislocation rate of 10 % for the out-of-plane approach was reported, the use of an in-plane technique similar to our study protocol resulted in a much higher dislocation rate of 40 %. We found an even higher dislocation rate of 60 % for conventional catheters in our study. Important difference is the longer part of catheter remaining under the perineural fascia sheath. A catheter distance within the perineural fascia sheath of 1.6 cm in our study compared to 3.4 cm in the investigation of Hauritz et al. may increase catheter dislocations due to traction forces as already mentioned before. Interestingly, the application of self-coiling catheter using the in-plane approach decreased the dislocation rate to a level reported by Hauritz et al. for the out-of-plane technique. Whereas regular straight perineural catheters seem more reliable in point of dislocation rate using out-of-plane approach, whereas the self-coiling catheters may be placed with good results performing the in-plane technique.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec28\" class=\"Section3\"\u003e \u003ch2\u003eLeakage and catheter shift at the insertion site\u003c/h2\u003e \u003cp\u003eThe maximum leakage rate was 31.4 % in both groups in our study. This is comparable with the leaking rate of 31 % for CTN technique in another study [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Lower leakage rates of 13.9 % for continuous distal sciatic catheters were reported [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. Leakage problems commonly occur with catheter-through-needle approaches, because needle\u0026acute;s diameter is larger than the catheter. Thus, the tissue is not sealing the puncture track along the catheter and injected fluid as well as interstitial fluid or blood can flow retrogradely. Though catheter-over-needle technique decreases the occurrence of leaking, no superiority regarding dislocation rates has been shown in clinical trials so far [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. Accordingly, we did not observe any relation between leakage and dislocations since both study groups showed the same leakage rate. Dislocation rates in terms of the catheter slipping out of the skin at the insertion site are reported with an incidence of 0.5 to 26 % [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In our study we considered an outward slipping at the insertion site of 1 cm or more as a clinically relevant movement. This was evident in 10 % in SCC group and 12.6 % in RSC group. According to findings of Marhofer et al. we could not observe a significant impact of outwardly slipped catheters at insertion site on the dislocation rate at target area [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec29\" class=\"Section3\"\u003e \u003ch2\u003eComplications\u003c/h2\u003e \u003cp\u003eThe overall complication rate was very low. No persistent neurologic deficit was observed. The most severe complication was a patient with a metallic taste several hours after catheter application considered as a mild sign of local anesthetic systemic toxicity. Ropivacaine infusion was stopped. Neither a negative aspiration test nor sonographic imaging of fluid spread via the catheter revealed a secondary intravascular dislocation. The catheter was removed immediately, followed by complete regression of symptoms. The overall mild infection rate of 5.7 % observed here ranges within the results of other studies [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. Mild infection was considered as any redness of the puncture site during daily visit. The catheters were removed immediately without any further sequels.\u003c/p\u003e \u003cp\u003eIn this study, catheter occlusion occurred in one patient from each cohort (total 1.4 %). Ma et al. reported this rare incident with a rate of 1 % [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec30\" class=\"Section3\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eOur results are limited to the use of ropivacaine for the initial bolus. The dislocated catheters probably would have been earlier discovered by using a short- or middle-long acting local anesthetic for the initial bolus. Additionally, for rescue pain management patients received opioids orally by nurses only on demand in a fixed dosage of 10 mg Oxycodone. A more finely tuned opioid application, e.g. by patient controlled intravenous analgesia could have led to a clearer reflection of the actual need for additional painkillers.\u003c/p\u003e \u003cp\u003eAnother limitation is the single shot concept for saphenous nerve block with limited pain relief of 12- 18 hours. Thus, NRS scores may have been influenced by pain perception in saphenous nerve innervation area.\u003c/p\u003e \u003cp\u003eFurthermore, the design of our study was not double blinded since the ultrasound examiner occasionally could have drawn conclusions regarding catheter type by watching insertion depth specific catheter length graduations.\u003c/p\u003e \u003cp\u003eThe results of this study apply only to our setting of short axis view of the nerve and in-plane needle approach. Beyond that, our results are not applicable for other catheter designs or alternative insertion sites.\u003c/p\u003e \u003cp\u003eIn the case of sonographically confirmed catheter dislocation in situ, no further positional checks were performed. Whether it is possible that the misalignment could spontaneously convert to a renewed perineural position or not remains unclear.\u003c/p\u003e \u003cp\u003eFurthermore, extrafascial dislocation does not necessarily mean a complete loss of effectiveness. Our continuous ropivacaine dose may have been still sufficient to release pain by local anesthetic spreading toward the nerve along the residual puncture pathway or by diffusion through the connective tissue. Experience from the efficacy of interfascial plane blocks (e.g. the erector spinae block), we suspect some analgetic effects of even low amounts of LA by blocking small C-fibres, even if the application site is not close to the target nerve.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe self-coiling catheter design for continuous popliteal sciatic nerve block offers a superior postoperative pain control and a lower dislocation rate within the tissue than a conventional straight catheter design. Secondary migration, away from the nerve target structure, could only be visualised sonographically and was not related to the external appearance at the puncture site. Additional studies for other alternative techniques and localization are warranted to further evaluate this design.\u003c/p\u003e"},{"header":"Abbrevations","content":"\u003cp\u003eAE: adverse event; CTN: Catheter-through-needle; CON: Catheter-over-needle; CONSORT: Consolidated Standards of Reporting Trials; IP: in-plane; LA: local anesthetic; NRS: numeric rating scale; OOP: out-of-plane; PACU: post anesthesia care unit; PNB: peripheral nerve block; POD: postoperative day; RA: regional anesthesia; RSC: regular straight catheter; SAE: severe adverse event; SAX: short axis view; SCC: self-coiling catheter; US: ultrasound\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present trial was approved by the local institutional review board of the TU Dresden, the\u0026nbsp;\u0026ldquo;Ethikkomission an der Technischen Universit\u0026auml;t Dresden\u0026rdquo;, Dresden, Germany (approval number: EK 150042016). Written informed consent was obtained from all participants with the informed consent form prior to trial enrolment. All methods were carried out in accordance with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOV performs consulting services and receives lecture honoraria from Pajunk, Geisingen, Germany and Sintetica GmbH, Muenster, Germany. All other authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present trial was supported by Pajunk,\u0026nbsp;Geisingen, Germany, who provided the trial catheters, but had no part in study design, data collection, interpreting the results or preparing the manuscript.\u003c/p\u003e\n\u003cp\u003eSupport was provided by the Open Access Funding by the Publication Fund of the TU Dresden.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u003c/strong\u003e\u003cstrong\u003e\u0026acute;\u003c/strong\u003e\u003cstrong\u003es contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOV and RN designed the study protocol, generated the random allocation sequence, enrolled participants, and collected data and contributed to manuscript preparation. OV, AO and TM helped with data collection including performance of sonographic controls of the catheter positions. RN, KS and TR performed the statistical data analysis. TR, OV and TK helped preparing the manuscript and interpreting the data. All authors have read and approved the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors thank the anesthetic and surgical staff of the University Center of Orthopaedics and Traumatology and Comprehensive Pain Center, University Hospital Carl Gustav Carus Dresden, Dresden, Germany.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eData was part of thesis by Rosa Nickl.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u003c/strong\u003e\u003cstrong\u003e\u0026acute;\u003c/strong\u003e\u003cstrong\u003es information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eDepartment of Anesthesiology and Critical Care Medicine, University Hospital Carl Gustav Carus at the Technische Universit\u0026auml;t Dresden, Fetscherstr. 74, 01307 Dresden, Germany.\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e2\u0026nbsp;\u003c/sup\u003eInstitute for Medical Informatics and Biometry, Medical Faculty Carl Gustav Carus, Technische Universit\u0026auml;t Dresden, Fetscherstr. 74, 01307 Dresden, Germany.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eChelly JE, Ghisi D, Fanelli A. Continuous peripheral nerve blocks in acute pain management. British Journal of Anaesthesia. 2010;105:i86\u0026ndash;96.\u003c/li\u003e\n\u003cli\u003eGerbershagen HJ, Aduckathil S, van Wijck AJM, Peelen LM, Kalkman CJ, Meissner W. Pain Intensity on the First Day after Surgery: A Prospective Cohort Study Comparing 179 Surgical Procedures. Anesthesiology. 2013;118:934\u0026ndash;44.\u003c/li\u003e\n\u003cli\u003eSalviz EA, Xu D, Frulla A, Kwofie K, Shastri U, Chen J, et al. Continuous Interscalene Block in Patients Having Outpatient Rotator Cuff Repair Surgery: A Prospective Randomized Trial. Anesthesia \u0026amp; Analgesia. 2013;117:1485\u0026ndash;92.\u003c/li\u003e\n\u003cli\u003ePeng L, Ren L, Qin P, Chen J, Feng P, Lin H, et al. Continuous Femoral Nerve Block versus Intravenous Patient Controlled Analgesia for Knee Mobility and Long-Term Pain in Patients Receiving Total Knee Replacement: A Randomized Controlled Trial. Evidence-Based Complementary and Alternative Medicine. 2014;2014:1\u0026ndash;12.\u003c/li\u003e\n\u003cli\u003eSakai N, Inoue T, Kunugiza Y, Tomita T, Mashimo T. Continuous Femoral Versus Epidural Block for Attainment Of 120\u0026deg; Knee Flexion After Total Knee Arthroplasty: A Randomized Controlled Trial. The Journal of Arthroplasty. 2013;28:807\u0026ndash;14.\u003c/li\u003e\n\u003cli\u003eAlbrecht E, Bathory I, Fournier N, Jacot-Guillarmod A, Farron A, Brull R. Reduced hemidiaphragmatic paresis with extrafascial compared with conventional intrafascial tip placement for continuous interscalene brachial plexus block: a randomized, controlled, double-blind trial. British Journal of Anaesthesia. 2017;118:586\u0026ndash;92.\u003c/li\u003e\n\u003cli\u003eAbildgaard JT, Lonergan KT, Tolan SJ, Kissenberth MJ, Hawkins RJ, Washburn R, et al. Liposomal bupivacaine versus indwelling interscalene nerve block for postoperative pain control in shoulder arthroplasty: a prospective randomized controlled trial. Journal of Shoulder and Elbow Surgery. 2017;26:1175\u0026ndash;81.\u003c/li\u003e\n\u003cli\u003eAhsan ZS, Carvalho B, Yao J. Incidence of Failure of Continuous Peripheral Nerve Catheters for Postoperative Analgesia in Upper Extremity Surgery. The Journal of Hand Surgery. 2014;39:324\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eGurnaney H, Kraemer FW, Maxwell L, Muhly WT, Schleelein L, Ganesh A. Ambulatory Continuous Peripheral Nerve Blocks in Children and Adolescents: A Longitudinal 8-Year Single Center Study. Anesthesia \u0026amp; Analgesia. 2014;118:621\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eHauritz RW, Pedersen EM, Linde FS, Kibak K, B\u0026oslash;rglum J, Bjoern S, et al. Displacement of popliteal sciatic nerve catheters after major foot and ankle surgery: a randomized controlled double-blinded magnetic resonance imaging study. British Journal of Anaesthesia. 2016;117:220\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eFredrickson MJ, Leightley P, Wong A, Chaddock M, Abeysekera A, Frampton C. An analysis of 1505 consecutive patients receiving continuous interscalene analgesia at home: a multicentre prospective safety study. Anaesthesia. 2016;71:373\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eWalker BJ, Long JB, De Oliveira GS, Szmuk P, Setiawan C, Polaner DM, et al. Peripheral nerve catheters in children: an analysis of safety and practice patterns from the pediatric regional anesthesia network (PRAN). British Journal of Anaesthesia. 2015;115:457\u0026ndash;62.\u003c/li\u003e\n\u003cli\u003eEdward Kim T, Howard SK, Funck N, Kyle Harrison T, Walters TL, Wagner MJ, et al. A randomized comparison of long-axis and short-axis imaging for in-plane ultrasound-guided popliteal-sciatic perineural catheter insertion. J Anesth. 2014;28:854\u0026ndash;60.\u003c/li\u003e\n\u003cli\u003eSwenson JD, Davis JJ, DeCou JA. A Novel Approach for Assessing Catheter Position After Ultrasound-Guided Placement of Continuous Interscalene Block: Anesthesia \u0026amp; Analgesia. 2008;106:1015\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eMarhofer D, Marhofer P, Triffterer L, Leonhardt M, Weber M, Zeitlinger M. Dislocation rates of perineural catheters: a volunteer study. British Journal of Anaesthesia. 2013;111:800\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eSteffel L, Howard SK, Borg L, Mariano ER, Leng JC, Kim TE. Randomized comparison of popliteal-sciatic perineural catheter tip migration and dislocation in a cadaver model using two catheter designs. Korean Journal of Anesthesiology. 2017;70-72.\u003c/li\u003e\n\u003cli\u003eIlfeld BM, Fredrickson MJ, Mariano ER. Ultrasound-Guided Perineural Catheter Insertion: Three Approaches but Few Illuminating Data. Regional Anesthesia and Pain Medicine. 2010;35:123\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eLuyet C, Meyer C, Herrmann G, Hatch GM, Ross S, Eichenberger U. Placement of coiled catheters into the paravertebral space*: Placement of coiled catheters in the paravertebral space. Anaesthesia. 2012;67:250\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eLuyet C, Seiler R, Herrmann G, Hatch GM, Ross S, Eichenberger U. Newly Designed, Self-Coiling Catheters for Regional Anesthesia-An Imaging Study: Regional Anesthesia and Pain Medicine. 2011;36:171\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eEldridge SM, Campbell MJ, Bond CM, Hopewell S, Thabane L, Lancaster GA. CONSORT 2010 statement: extension to randomised pilot and feasibility trials. Pilot Feasibility Stud. 2016;2:64, s40814-016-0105\u0026ndash;8.\u003c/li\u003e\n\u003cli\u003eAndersen HL, Andersen SL, Tranum-Jensen J. Injection Inside the Paraneural Sheath of the Sciatic Nerve: Direct Comparison Among Ultrasound Imaging, Macroscopic Anatomy, and Histologic Analysis. Regional Anesthesia and Pain Medicine. 2012;37:410\u0026ndash;4.\u003c/li\u003e\n\u003cli\u003eChristiansen CB, Madsen MH, Rothe C, Andreasen AM, Lundstr\u0026oslash;m LH, Lange KHW. Volume of ropivacaine 0.2% and sciatic nerve block duration: A randomized, blinded trial in healthy volunteers. Acta Anaesthesiol Scand. 2020;64:238\u0026ndash;44.\u003c/li\u003e\n\u003cli\u003eDing DY, Manoli A, Galos DK, Jain S, Tejwani NC. Continuous Popliteal Sciatic Nerve Block Versus Single Injection Nerve Block for Ankle Fracture Surgery: A Prospective Randomized Comparative Trial. Journal of Orthopaedic Trauma. 2015;29:393\u0026ndash;8.\u003c/li\u003e\n\u003cli\u003eZaric D, Boysen K, Christiansen J, Haastrup U, Kofoed H, Rawal N. Continuous popliteal sciatic nerve block for outpatient foot surgery - a randomized, controlled trial. Acta Anaesthesiol Scand. 2004;48:337\u0026ndash;41.\u003c/li\u003e\n\u003cli\u003eElliot R, Pearce CJ, Seifert C, Calder DJ. Continuous Infusion Versus Single Bolus Popliteal Block Following Major Ankle and Hindfoot Surgery: A Prospective, Randomized Trial. Foot \u0026amp; Ankle International. 2010;31:1043\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eK\u0026aring;sine T, Romundstad L, Rosseland LA, Fagerland MW, Kessler P, Omen\u0026aring;s IN, et al. Ultrasonographic needle tip tracking for in-plane infraclavicular brachialis plexus blocks: a randomized controlled volunteer study. Reg Anesth Pain Med. 2020;45:634\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eFisker AK, Iversen BN, Christensen S, Linde F, Nielsen KK, B\u0026oslash;rglum J, et al. Combined saphenous and sciatic catheters for analgesia after major ankle surgery: a double-blinded randomized controlled trial. Can J Anesth/J Can Anesth. 2015;62:875\u0026ndash;82.\u003c/li\u003e\n\u003cli\u003eJarrell K, McDonald E, Shakked R, Nicholson K, Kasper V, Raikin SM. Combined Popliteal Catheter With Single-Injection vs Continuous-Infusion Saphenous Nerve Block for Foot and Ankle Surgery. Foot Ankle Int. 2018;39:332\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eBj\u0026oslash;rn S, Linde F, Nielsen KK, B\u0026oslash;rglum J, Hauritz RW, Bendtsen TF. Effect of Perineural Dexamethasone on the Duration of Single Injection Saphenous Nerve Block for Analgesia After Major Ankle Surgery: A Randomized, Controlled Study. Regional Anesthesia and Pain Medicine. 2017;42:210\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eBendtsen TF, Nielsen TD, Rohde CV, Kibak K, Linde F. Ultrasound Guidance Improves a Continuous Popliteal Sciatic Nerve Block When Compared With Nerve Stimulation: Regional Anesthesia and Pain Medicine. 2011;36:181\u0026ndash;4.\u003c/li\u003e\n\u003cli\u003eCapdevila X, Dadure C, Bringuier S, Bernard N, Biboulet P, Gaertner E, et al. Effect of Patient-controlled Perineural Analgesia on Rehabilitation and Pain after Ambulatory Orthopedic Surgery: A Multicenter Randomized Trial. Anesthesiology. 2006;105:566\u0026ndash;73.\u003c/li\u003e\n\u003cli\u003eIlfeld BM, Morey TE, Wang RD, Enneking FK. Continuous Popliteal Sciatic Nerve Block for Postoperative Pain Control at Home: A Randomized, Double-Blinded, Placebo-Controlled Study. Anesthesiology. 2002;97:959\u0026ndash;65.\u003c/li\u003e\n\u003cli\u003eWhite PF, Issioui T, Skrivanek GD, Early JS, Wakefield C. The Use of a Continuous Popliteal Sciatic Nerve Block After Surgery Involving the Foot and Ankle: Does It Improve the Quality of Recovery?: Anesthesia \u0026amp; Analgesia. 2003;97:1303\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eYaDeau JT, Fields KG, Kahn RL, LaSala VR, Ellis SJ, Levine DS, et al. Readiness for Discharge After Foot and Ankle Surgery Using Peripheral Nerve Blocks: A Randomized Controlled Trial Comparing Spinal and General Anesthesia as Supplements to Nerve Blocks. Anesthesia \u0026amp; Analgesia. 2018;127:759\u0026ndash;66.\u003c/li\u003e\n\u003cli\u003eFredrickson MJ. Randomised Comparison of an End-Hole, Triple-Hole and Novel Six-Hole Catheter for Continuous Interscalene Analgesia. Anaesthesia and Intensive Care. 2014;42:37\u0026ndash;42.\u003c/li\u003e\n\u003cli\u003eNovello-Siegenthaler A, Hamdani M, Iselin-Chaves I, Fournier R. Ultrasound-guided continuous femoral nerve block: a randomized trial on the influence of femoral nerve catheter orifice configuration (six-hole versus end-hole) on post-operative analgesia after total knee arthroplasty. BMC Anesthesiol. 2018;18:191.\u003c/li\u003e\n\u003cli\u003eFredrickson MJ, Ball CM, Dalgleish AJ. Catheter Orifice Configuration Influences the Effectiveness of Continuous Peripheral Nerve Blockade: Regional Anesthesia and Pain Medicine. 2011;36:470\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eIlfeld BM, Sandhu NS, Loland VJ, Madison SJ, Suresh PJ, Mariano ER, et al. Ultrasound-Guided (Needle-in-Plane) Perineural Catheter Insertion: The Effect of Catheter-Insertion Distance on Postoperative Analgesia. Regional Anesthesia and Pain Medicine. 2011;36:261\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eSchnabel A, Meyer-Frie\u0026szlig;em CH, Zahn PK, Pogatzki-Zahn EM. Ultrasound compared with nerve stimulation guidance for peripheral nerve catheter placement: a meta-analysis of randomized controlled trials. British Journal of Anaesthesia. 2013;111:564\u0026ndash;72.\u003c/li\u003e\n\u003cli\u003eFinneran JJ, Swisher MW, Gabriel RA, Said ET, Abanobi MU, Abramson WB, et al. Suture-method \u003cem\u003eversus\u003c/em\u003e Through-the-needle Catheters for Continuous Popliteal-sciatic Nerve Blocks. Anesthesiology. 2020;132:854\u0026ndash;66.\u003c/li\u003e\n\u003cli\u003eMarhofer P, Anderl W, Heuberer P, Fritz M, Kimberger O, Marhofer D, et al. A retrospective analysis of 509 consecutive interscalene catheter insertions for ambulatory surgery. Anaesthesia. 2015;70:41\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eBrookes J, Sondekoppam R, Armstrong K, Uppal V, Dhir S, Terlecki M, et al. Comparative evaluation of the visibility and block characteristics of a stimulating needle and catheter vs an echogenic needle and catheter for sciatic nerve block with a low-frequency ultrasound probe. British Journal of Anaesthesia. 2015;115:912\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eHauritz RW, Pedersen EM, Linde FS, Kibak K, B\u0026oslash;rglum J, Bjoern S, et al. Displacement of popliteal sciatic nerve catheters after major foot and ankle surgery: a randomized controlled double-blinded magnetic resonance imaging study. British Journal of Anaesthesia. 2016;117:220\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eMa H-H, Chou T-FA, Tsai S-W, Chen C-F, Wu P-K, Chen W-M. The efficacy and safety of continuous versus single-injection popliteal sciatic nerve block in outpatient foot and ankle surgery: a systematic review and meta-analysis. BMC Musculoskelet Disord. 2019;20:441.\u003c/li\u003e\n\u003cli\u003eIp VHY, Rockley MC, Tsui BCH. The catheter-over-needle assembly offers greater stability and less leakage compared with the traditional counterpart in continuous interscalene nerve blocks: a randomized patient-blinded study. Canadian Journal of Anesthesia/Journal canadien d\u0026rsquo;anesth\u0026eacute;sie. 2013;60:1272\u0026ndash;3.\u003c/li\u003e\n\u003cli\u003eTsui BC, Ip VH. Catheter-over-needle method reduces risk of perineural catheter dislocation. British Journal of Anaesthesia. 2014;112:759\u0026ndash;60.\u003c/li\u003e\n\u003cli\u003eMorin AM, Kerwat KM, Klotz M, Niestolik R, Ruf VE, Wulf H, et al. Risk factors for bacterial catheter colonization in regional anaesthesia. BMC Anesthesiology. 2005;5:1.\u003c/li\u003e\n\u003cli\u003eNeuburger M, Breitbarth J, Reisig F, Lang D, B\u0026uuml;ttner J. Komplikationen bei peripherer Katheterregionalan\u0026auml;sthesie: Untersuchungsergebnisse anhand von 3491 Kathetern. Der Anaesthesist. 2006;55:33\u0026ndash;40.\u003c/li\u003e\n\u003cli\u003eKerwat K, Eberhart L, Kerwat M, H\u0026ouml;rth D, Wulf H, Steinfeldt T, et al. Chlorhexidine Gluconate Dressings Reduce Bacterial Colonization Rates in Epidural and Peripheral Regional Catheters. BioMed Research International. 2015;2015:149785.\u003c/li\u003e\n\u003cli\u003eAubuchon A, Arnold WD, Bracewell A, Hoyle JC. Sciatic neuropathy due to popliteal fossa nerve block: Short Report. Muscle \u0026amp; Nerve. 2017;56:822\u0026ndash;4.\u003c/li\u003e\n\u003cli\u003ePark YU, Cho JH, Lee DH, Choi WS, Lee HD, Kim KS. Complications After Multiple-Site Peripheral Nerve Blocks for Foot and Ankle Surgery Compared With Popliteal Sciatic Nerve Block Alone. Foot \u0026amp; Ankle International. 2018;39:731-5.\u003c/li\u003e\n\u003cli\u003eUchino T, Miura M, Oyama Y, Matsumoto S, Shingu C, Kitano T. Lateral deviation of four types of epidural catheters from the lumbar epidural space into the intervertebral foramen. J Anesth. 2016;30:583\u0026ndash;90.\u003c/li\u003e\n\u003cli\u003eMariano ER, Yun RDH, Kim TE, Carvalho B. Application of Echogenic Technology for Catheters Used in Ultrasound-Guided Continuous Peripheral Nerve Blocks. Journal of Ultrasound in Medicine. 2014;33:905\u0026ndash;11.\u003c/li\u003e\n\u003cli\u003eTakatani J, Takeshima N, Okuda K, Uchino T, Noguchi T. Ultrasound visibility of regional anesthesia catheters: an in vitro study. Korean J Anesthesiol. 2012;63:59-64.\u003c/li\u003e\n\u003cli\u003eMoy DM, Kim TE, Harrison TK, Leng JC, Carvalho B, Howard SK, et al. Comparative Echogenicity of an Epidural Catheter and 2 New Catheters Designed for Ultrasound-Guided Continuous Peripheral Nerve Blocks: Echogenicity of 3 Regional Anesthesia Catheters. J Ultrasound Med. 2017;36:2571\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eJaime F, Mandell GL, Vallejo MC, Ramanathan S. Uniport soft-tip, open-ended catheters versus multiport firm-tipped close-ended catheters for epidural labor analgesia: a quality assurance study. Journal of Clinical Anesthesia. 2000;12:89\u0026ndash;93.\u003c/li\u003e\n\u003cli\u003eShih C-K, Wang F-Y, Shieh C-F, Huang J-M, Lu I-C, Wu L-C, et al. Soft catheters reduce the risk of intravascular cannulation during epidural block\u0026mdash;A retrospective analysis of 1117 cases in a medical center. The Kaohsiung Journal of Medical Sciences. 2012;28:373\u0026ndash;6.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-anesthesiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bane","sideBox":"Learn more about [BMC Anesthesiology](http://bmcanesthesiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bane","title":"BMC Anesthesiology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"perineural catheter, popliteal sciatic block, self-coiling catheter, dislocation, ultrasound- guided re-gional anesthesia","lastPublishedDoi":"10.21203/rs.3.rs-959997/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-959997/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e: Catheter dislocation within the tissue is a challenge in continuous regional anesthesia. A novel self-coiling catheter design has been available providing lower dislocation rate in a cadaver model. So far it hasn´t been demonstrated whether the self-coiling catheter offers any remarkable advantages for continuous peripheral regional anesthesia in vivo. \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e After ethics committee approval 140 patients undergoing elective distal lower limb surgery were enrolled in this prospective randomized controlled trial. Preoperatively, patients were randomly assigned and received either the conventional (n=70) or self-coiling catheter (n=70) for ultrasound-guided popliteal sciatic nerve block in short axis view and in-plane approach from lateral. The primary endpoint was pain intensity after surgery and on the following days. Secondary outcomes investigated were dislocation rate in situ, externally visible catheter movement, opioid consumption as well as leakage at the puncture site.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e All catheters were successfully inserted. The study population of self-coiling catheters had significantly lower mean numeric rating scale values than the reference cohort on the first (p=0.01) and second postoperative days (p\u0026lt;0.01). Sonographic evaluation has shown, 42 standard catheters (60\u0026nbsp;%) and 10 self-coiling catheters (14.3\u0026nbsp;%) were dislocated in situ within the first three postoperative days. The externally visible movement of the catheters at insertion site did not differ significantly and was on average less than 0.5\u0026nbsp;cm on the third day. The amount of opioids administered was significantly lower in the self-coiling catheter group on the day of surgery and on the second and third postoperative days (p=0.04, p=0.03 and p=0.04, respectively). \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e The self-coiling catheter offers a superior postoperative pain control and a lower dislocation rate within the tissue for popliteal sciatic nerve blockade compared to a conventional catheter. Further trials in large patient cohorts are warranted to investigate potential beneficial effects of self-coiling catheters for other localisations and other application techniques.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTrial registration\u003c/strong\u003e: The trial was registered at German Clinical Trials Register (DRKS) on 08/04/2020 (DRKS00020938, retrospectively registered).\u003c/p\u003e","manuscriptTitle":"Impact of Self-Coiling Catheters for Continuous Popliteal Sciatic Block on Postoperative Pain Level and Dislocation Rate: A Randomized Controlled Trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-10-26 21:09:17","doi":"10.21203/rs.3.rs-959997/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2022-01-17T06:08:19+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2022-01-06T01:29:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"c2bd4bfb-e097-4ae6-8f0b-84ae70e888c2","date":"2021-12-17T10:54:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"66e78cb6-9794-4d9c-8e06-46f80f3708af","date":"2021-12-14T15:44:51+00:00","index":"hide","fulltext":""},{"type":"editorAssigned","content":"","date":"2021-12-14T06:51:55+00:00","index":"","fulltext":""},{"type":"reviewersInvited","content":"","date":"2021-12-14T03:38:08+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2021-10-25T08:29:58+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2021-10-25T08:25:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Anesthesiology","date":"2021-10-08T08:41:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-anesthesiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bane","sideBox":"Learn more about [BMC Anesthesiology](http://bmcanesthesiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bane","title":"BMC Anesthesiology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7d530f19-bd5c-4aaa-8fac-6001fc655691","owner":[],"postedDate":"October 26th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":8113176,"name":"Anesthesiology \u0026 Pain Medicine"}],"tags":[],"updatedAt":"2022-05-19T05:29:20+00:00","versionOfRecord":[],"versionCreatedAt":"2021-10-26 21:09:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-959997","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-959997","identity":"rs-959997","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}