Is unilateral biportal endoscopic discectomy superior to percutaneous interlaminar endoscopic discectomy in the treatment of L5/S1 disc herniation? A retrospective study

Is unilateral biportal endoscopic discectomy superior to percutaneous interlaminar endoscopic discectomy in the treatment of L5/S1 disc herniation? 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A retrospective study Jianjian YIN, Tao MA, Gongming GAO, Qi CHEN, Luming NONG This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3965547/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose To compare the clinical outcomes of unilateral biportal endoscopic discectomy (UBED) and percutaneous interlaminar endoscopic discectomy (PIED) for treating L5/S1 disc herniation. Methods Patients with L5/S1 disc herniation treated with UBED (n = 46) and PIED (n = 50) in our hospital during the same period were retrospectively reviewed. Total blood loss (TBL), operation time, hospital stay, complications, total hospitalization costs, clinical efficacy and modified MacNab criteria were collected and evaluated. Percentage of facet joint preservation measured on axial CT scans obtained pre-operation and post-operation. Results The mean follow-up period was 14.07 ± 3.50 months in UBED group, and 14.52 ± 5.37 months in PIED group. The total blood loss and hospitalization cost was more in the UBED Group. The operative time and hospital stay time in the UBED Group was similar with that in PIED Group. The postoperative VAS back, leg scores and ODI score were significantly improved compared with the preoperative scores in both two groups. There was no significant difference in VAS back and leg scores between two groups at 1-day post-operation and final follow-up period. All patients of two groups had similar ODI scores at final follow-up period. The percentage of facet joint preservation is 96.56 ± 9.11% in UBED group, which is significantly less than in PIED group with 99.22 ± 1.52%. One patient in both groups showed postoperative hematoma. A dural tear occurred in UBED group and a never root injury occurred in PIED group. There was no significant difference in patient satisfaction rates between two groups. Conclusion UBED indicates similar clinical effect compared with PIED for treating L5/S1 disc herniation, and there was no significant increase in surgical time or hospital stay. However, more facet joint damage, total blood loss and hospitalization cost may be the disadvantages of UBED technique and need to be taken seriously. lumbar disc herniation unilateral biportal endoscopic discectomy percutaneous interlaminar endoscopic discectomy total blood loss facet joint preservation Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Since percutaneous interlaminar endoscopic discectomy (PIED) was firstly introduced by Ruetten in 2008 [ 1 ] . This minimally invasive spine surgery (MISS) has been widely performed and proved to be a safe and effective treatment for lumbar disc herniation with its less paraspinal muscle damage, clear surgical vision and efficient nerve decompression, especially for L5/S1 segment [ 2 , 3 ] . In previous experience [ 4 ] , uniportal full-endoscopic technique has been excellent enough in handling pure lumbar disc herniation (LDH). However, restricted by its single working channel and limited endoscopic surgical instruments. PIED can be clinically challenging in dealing with central type or highly migrated disc herniation [ 5 , 6 ] , and even cause nerve root damage when seeking sufficient decompression. Different from the limitation of uniportal full-endoscopic vision and control space, the unilateral biportal endoscopic (UBE) technique enables surgeons to control surgical instruments more flexibly through observation and working channels to complete a wider range of decompression procedures [ 7 ] . From the introduction of UBE technique to its widespread and flexible application, it has been proven by many scholars to be safe, effective, and efficient in dealing with cervical, thoracic, lumbar degenerative diseases, and even revision surgery [ 8 – 11 ] . Although UBE technique provides a broader surgical field of view and more flexible surgical procedures, the accompanying more paraspinal muscle injuries and corresponding hidden blood loss also need to be given sufficient attention [ 12 , 13 ] . Is unilateral biportal endoscopic discectomy superior to percutaneous interlaminar endoscopic discectomy in the treatment of L5/S1 disc herniation? In this retrospective study, we compared the clinical efficacy and safety of PIED and UBED by assessing clinical outcome and complications among patients in the treatment of L5/S1 disc herniation. Material and methods Patients We evaluated retrospectively a series of consecutive patients who underwent surgery for L5/S1 disc herniation at a single institution between April 2021 and October 2022. Inclusion criteria were: (1) unilateral radicular pain, (2) central, paracentral, or prolapsed L5/S1 disc herniation, (3) failed of conservative therapies at least 6 months. Exclusion criteria were therefore defined: (1) intervertebral disc inflammation or tuberculosis, (2) recurrent disc herniation and multiple segments of disc herniation (3) lumbar instability, such as lumbar spondylolisthesis, (4) widely lumbar stenosis and far lateral lumbar disc herniation. Surgical Procedures All the surgical procedures were performed by the same senior surgeon for minimizing influence of surgical techniques. UBED The patient is placed in a prone position after general anesthesia, adjusting the operating table to cause mild lumbar flexion, increasing the intervertebral space, and causing tension in the ligamentum flavum. A standard lumbar lateral X-ray is used to determine whether the surgical level is perpendicular to the ground. If not, the operating table still needs to be adjusted until satisfactory. After referring to an anterior and posterior X-ray film and using a grid shaped metal marker and a pen to mark the surface projection of the surgical level, pedicles, and midline of the spinous process, disinfection and laying can begin. We made two small portals located along the medial pedicle line. The cranial portal about 5–6 mm was used for continuous irrigation and endoscopy, the caudal portal about 8–10 mm was used for outflow of normal saline and working the decompression instruments. In this step, intraoperative fluoroscopy is required to confirm the surgical level (Fig. 1 ). After muscle-bone separation using the electrical coagulator, the lower margin of the upper lamina and interlaminar ligament were identified. Lamina fenestration was performed using a high-speed microdrill and Kerrison punches. As the interlaminar window at L5/S1 is exactly facing the intervertebral space, minimal removal of the vertebral lamina is required, unless it is an upward free prolapsed nucleus pulposus herniation. A nerve probing hook is used to make a hole in the weak area of the ligamentum flavum before flavectomy by Kerrison punches. To ensure a clear surgical field of view, pre hemostasis of small blood vessels by radiofrequency electrode in the spinal canal should be taken seriously. As the nerve roots and dura are exposed, proper ipsilateral recess decompression is needed to provide greater space for shoulder manipulation. By pushing the nerve to the opposite side through the nerve hook, most of the protruding nucleus pulposus can be completely removed. The axillary area also needs to be explored to further ensure sufficient nerve root decompression (Fig. 2 ). PIED The previous studies [ 14 , 15 ] have introduced the PIED procedure in detail. PIED was performed in a prone position under general anesthesia. In preoperative fluoroscopy, the lower endplate of L5, the upper endplate of S1, the midline of the spinous process, and the lateral edge of the intervertebral space need to be marked on the skin. A dilator is inserted bluntly to the lateral edge of the interlaminar window. A working channel with an oblique angle opening towards inner side was introduced over the dilator and the final position was checked on the AP and lateral fluoroscopic images. The surgery was performed after introducing an endoscope (Joimax GmbH, Karlsruhe, Baden-Württemberg, Germany). Soft tissues and the paraspinal muscle were cleaned by radiofrequency electrode to expose the ligamentum flavum, into which a hole was punched. The working cannula was introduced into the epidural space through this hole, and the dura margin and nerve root were exposed. By rotating the working cannula, pushing the nerve root and dura to the opposite side. Once the nerve root was well protected, shoulder and axillary exploration and discectomy can begin. Clinical measurements General information included age, gender, height, weight, body-mass index (BMI) calculation, hypertension, diabetes, history of smoking, history of alcohol use, American Society of Anesthesiologists (ASA) classification, follow-up duration and disc location. Considering the difficulty in calculating the amount of intraoperative bleeding caused by the continuous flow of normal saline during endoscopic surgery. Hemoglobin (Hb) and hematocrit (Hct) were measured preoperatively and 1 day after operation. Total blood loss (TBL), operation time, hospital stay, complications and total hospitalization costs were collected and evaluated. The TBL was calculated according to the formula proposed by Gross JB [ 16 ] . TBL = PBV × (Hct pre - Hct post)/Hct ave; PBV = patient’s blood volume; Hct pre = patient’s pre-operative hematocrit; Hct post = patient’s post-operative hematocrit; Hct ave = (Hct pre + Hct post)/2; and PBV was calculated on the basis of the Nadler formula [ 17 ] . PBV (ml) = k1 × height (m) 3 + k2 × weight (kg) + k3, For men, k1 = 0.3669, k2 = 0.03219, and k3 = 0.6041, for women k1 = 0.3561, k2 = 0.03308, and k3 = 0.1833. Visual analog scale (VAS) back pain and leg pain were assessed by 2 experienced clinical researchers preoperatively, 1 day after operation and at last follow-up. The Oswestry Disability Index (ODI) score and the modified MacNab criteria were evaluated preoperatively and at last follow-up. Radiologic measurements The total soft-tissue thickness, subcutaneous layer thickness, and paraspinal muscle thickness at L5/S1 level were independently measured by two experienced spinal surgeons on lumbar sagittal MRI images (Fig. 3 ). Approach side percentage of facet joint preservation [ 18 ] measured on axial CT scans obtained pre-operation and post-operation (1 day after operation) (Fig. 4 ). Statistical analysis For statistical analysis, the SPSS 22.0 (SPSS Inc, Chicago, IL, USA) was used, and the P value less than 0.05 were considered significant. Measurement data are expressed as the mean ± standard deviation (x ± s). Comparisons between groups were performed by one-way analysis of variance and t-tests. Comparisons of the count data between the two groups, were performed using chi-square test. Result Patient population Ninety-six patients met the inclusion criteria. All patients had lumbar disc herniation at L5/S1. Forty-six patients underwent UBED, and fifty patients underwent PIED. The cohort study included 40 women and 56 men, and their mean age was 43.85 ± 11.41 years and 45.64 ± 13.60 years, respectively. The mean follow-up period was 14.07 ± 3.50 months in UBED group, and 14.52 ± 5.37 months in PIED group. Clinical outcome The total blood loss and the hospitalization cost was more in the UBED Group (394.16 ± 227.96ml, 37008.70 ± 3063.63 RMB) compared with PIED Group (273.83 ± 158.53 ml, 31244.12 ± 2202.45 RMB) (P < 0.05, P < 0.05) (Table 1 ). The operative time and hospital stay time in the UBED Group (80.98 ± 33.61 min, 5.54 ± 1.92 day) was similar with that in PIED Group (89.42 ± 32.16 min. 5.24 ± 1.89 day) (P = 0.212, P = 0.437) (Table 1 ). The postoperative VAS back, leg scores and ODI score were significantly improved compared with the preoperative scores in both two groups (P < 0.05, respectively). There was no significant difference in VAS back and leg scores between two groups at 1-day post-operation and final follow-up period (P = 0.172, P = 0.65, P = 0.372, P = 0.063, respectively). All patients of two groups had similar ODI scores at final follow-up period (P = 0.071) (Table 2 ). Table 1 Demographic and clinical characteristics for all the patients UBED PIED P-value No of cases 46 50 Age (years) 43.85±11.41 45.64±13.60 0.488 BMI (kg/㎡) 24.83±3.92 24.70±4.24 0.878 Male 29 27 0.369 Female 17 23 Hypertension (n) 10 10 0.834 Diabetes mellitus (n) 1 0 0.479 History of smoking 18 18 0.752 History of alcohol use 21 27 0.357 ASA classification (n) 0.452 I 11 17 II 33 31 III 2 1 Disc Location 0.916 Central 7 8 Paracentral 39 42 Soft tissue thickness (cm) 52.66±8.94 50.18±9.10 0.182 Paraspinal muscle thickness (cm) 33.51±4.98 31.86±5.20 0.116 Subcutaneous layer thickness (cm) 19.15±7.92 18.33±7.74 0.606 Operation time (min) 80.98±33.61 89.42±32.16 0.212 Hospital stay time (day) 5.54±1.92 5.24±1.89 0.437 Total cost (RMB) 37008.70±3063.63 31244.12±2202.45 <0.05 Follow up time (months) 14.07±3.50 14.52±5.37 0.622 Total blood loss (ml) 394.16±227.96 273.83±158.53 <0.05 Pre-op Hb (g/L) 145.80±17.94 144.94±16.43 0.806 Post-op Hb (g/L) 132.48±15.49 136.00±15.60 0.27 Hb loss, g/L (g/L) 13.33±8.35 8.94±6.72 <0.05 Pre-op Hct (%) 42.77±4.97 42.31±4.29 0.631 Post-op Hct (%) 39.10±5.10 39.792±4.07 0.464 Hct loss (%) 3.68±2.23 2.52±1.46 <0.05 Complications 2 2 Nerve root injury 0 1 Postopreative hematoma 1 1 Dural tear 1 0 Modified MacNab evaluation (excellent/good/fair/poor) 24/21/1/0 21/27/2/0 Excellent/good rate 97.80% 96% 0.607 Facet joint preservation 96.56 ± 9.11% 99.22 ± 1.52% <0.05 Table 2 Comparisons of clinical outcomes between the two groups UBED PIED P value VAS leg score Preoperation 7.87±0.34 7.78±0.55 0.333 1 day postoperation 1.67±0.52 1.84±0.65 0.172 Final follow-up 1.22±0.42 1.18±0.39 0.65 P value (pre-final) <0.05 <0.05 VAS lumbar score Preoperation 6.46±0.50 6.38±0.64 0.517 1 day postoperation 2.11±0.32 2.20±0.64 0.372 Final follow-up 1.37±0.49 1.56±0.50 0.063 P value (pre-final) <0.05 <0.05 ODI Preoperation 58.78±4.26 59.94±4.26 0.187 Final follow-up 16.78±2.68 18.00±3.80 0.071 P value (pre-final) <0.05 0.05). A patient with giant free nucleus pulposus in PIED group injured the nerve root resulting in postoperative pain hypersensitivity in the foot and a decrease in ankle flexor muscle strength. A patient in UBED group suffered damage to the dural sac due to local adhesion and developed cerebrospinal fluid leakage after surgery. They both recovered in subsequent treatment and did not experience any discomfort. One patient in both groups showed postoperative hematoma accompanied by gradually worsening pain symptoms in the buttocks and lower limbs. After two weeks, the lower limb symptoms gradually relieved and the hematoma was absorbed. Radiologic measurements The total soft-tissue, subcutaneous layer and paraspinal muscle thickness at L5/S1 level showed no significant difference between two groups (Table 1 ). 11 patients received partial excision of the facet joint in UBED group and 13 patients in PIED group. The percentage of facet joint preservation is 96.56 ± 9.11% in UBED group, which is significantly less than in PIED group with 99.22 ± 1.52%. Discussion Minimally invasive spinal surgery (MISS) has developed rapidly in recent years, and more and more spinal degenerative diseases can be effectively treated through MISS [ 19 ] . For patients undergoing general anesthesia surgery, it is necessary to have a correct understanding of the amount of bleeding during endoscopic surgery, which is crucial for ensuring patient safety. Due to the continuous flushing of normal saline during surgery, it has always been difficult to calculate the amount of bleeding during endoscopic surgery. In addition, surgeons often ignore the presence of hidden blood loss after endoscopic surgery. By referring to the published literature [ 20 – 22 ] , we only calculated the total bleeding volume based on the changes in hematocrit before and after surgery. On the premise that there is no significant difference in baseline data before surgery and operation time. The total bleeding volume in UBED group is greater than that in PIED group, which is statistically significant. This result may be caused by several reasons and requires our attention. While muscle-bone separation using the electrical coagulator on the surface of the vertebral lamina, UBED requires a larger range of muscle and soft tissue dissection to obtain greater operating space. Wang L et al [ 23 ] indicated the serum CPK level and change rate of lean multifidus cross-sectional area (LMCSA) for UBED was obviously higher than PIED at postoperative 1st day. Unlike PIED surgical instruments only used in work channel, various surgical instruments repeatedly enter and exit the surgical area through skin incisions during the operation of UBED, which can easily damage intermuscular blood vessels and cause bleeding. More vertebral lamina bone needs to be drilled to obtain a better range of vertebral canal fenestration in UBED compared with PIED. This usually means more oozing from trabecular bone, especially after continuous saline flushing stops. Sometimes, although the field of vision is very clear under continuous infusion of saline, bleeding is occurring outside the field of vision and is not detected. Perioperative blood pressure control also has a significant impact on the amount of bleeding during water-based endoscopic surgery in prone position. Surgeons often hope that anesthesiologists can control the patient's blood pressure at low level during surgery, thereby reducing bleeding in the endoscopic surgical field and ensuring clear and efficient surgery. However, Putowski Z et al [ 24 ] found that extending durations of low mean arterial pressure were associated with the development of either acute kidney injury, myocardial infarction or stroke. Perioperative blood pressure management that is too high, too low, or fluctuates significantly can pose a threat to the patient's safety. A meta-analysis [ 25 ] involving 1191 patients confirmed that application of antifibrinolytic agents were able to effectively reduce perioperative blood loss and transfusion requirements in spine surgery. Lotan R et al [ 26 ] reported that a routine administration of preoperative weight-independent 1 g intravenous topical tranexamic acid protocol is efficacious and safe in reducing perioperative blood loss for lumbar multilevel laminectomies. Based on a retrospective study [ 27 ] included 112 patients receiving lumbar fusion surgery, intra- and postoperative blood loss and need for transfusion were significantly lower in the tranexamic acid group. To avoid other potential risks associated with excessive blood pressure regulation, perioperative use of hemostatic drugs seems to be a good way to reduce bleeding during endoscopic surgery. Generally speaking, the efficacy of endoscopic surgery is immediately apparent after anesthesia and wakefulness, and is highly valued. According to the MacNab criteria, the excellence/good rates in the PIED group and UBED group are similar. In our study, we observed significant improvements in the leg scores and ODI score at one day post-operation and the final follow-up time. And, there were no significant differences in the improvements of lower limb symptom and function between two groups, showing that the two procedures were equally effective in the decompression for LDH in L5/S1. Adequate decompression range usually represents effective nerve relaxation and indicates better improvement in lower limb symptoms. Based on Pao JL et al’ s study [ 28 ] , the measured cross-sectional dural area at the most stenotic axial image on MRI was significantly enlarged from 71.4 ± 36.5 to 177.3 ± 59.2 mm 2 after UBE decompression. Kim HS et al [ 29 ] confirmed that there was no significant difference in dura expansion (329.71 ± 54.21 vs. 315.20 ± 62.79) between UBED and Conventional Microscopic ULBD. Usually, such extensive decompression is not necessary to cope with lumbar disc herniation, which is characterized by a high incidence of unilateral lower limb symptoms. For those who habitually use UBE technology to treat spinal stenosis, treating lumbar disc herniation is simpler and more feasible. In our study, VAS back scores did not show significant differences due to differences in the extent of injury to the paravertebral muscles. Chang H et al [ 30 ] indicated that UBED enables comparable result to conventional microdiscectomy regarding perioperative parameters and clinical outcomes. People who underwent UBED complains less back pain in the immediate postoperative period. Similarly, Kim SK et al [ 31 ] confirmed that back VAS score in the UBED group showed significantly more improvement than that in the microdiscectomy group at one-week post-operation. More laminectomy and muscle dissection during UBED surgery did not significantly improve postoperative VAS back pain scores, which established confidence in our extensive minimally invasive surgery in the later stage. In our study, the operation time of UBED and PIED group is 80.98 ± 33.61 min and 89.42 ± 32.16 min. Although there is a difference between the two group, it is not statistically significant. The indicator of operation time varies greatly in each independent study, which is closely related to the surgeon's own level of technical proficiency. As the learning curve progresses and proficiency improves, surgical time decreases. Xu J et al [ 32 ] investigated that the operation time of UBED in learning phase, practicing phase and mastery phase is 152.92 ± 26.33 min, 124.45 ± 37.07 min and 117.36 ± 17.06 min, respectively. Similarly, Chen L et al [ 33 ] found that the operation time of late 73 cases is 90.5 ± 27.8 min, which is significantly shorter than the early 24 cases (120.3 ± 43.8 min). The type of lumbar disc herniation is also an important factor affecting operation time. For giant herniated and prolapsed intervertebral disc herniation, the surgical time will also be correspondingly extended. In order to ensure that the nerve is not subjected to excessive traction when removing the nucleus pulposus, a larger dorsal space needs to be opened and reserved. This means extensive bone and ligamentum flavum tissue decompression on the dorsal side. In terms of hospitalization time, there was no significant difference between the two groups of surgical patients, possibly because both surgical methods used the same anesthesia method, which resulted in little difference in postoperative observation time for patients. Although there have been recent literatures [ 34 , 35 ] report on a considerable number of cases of PIED surgery under local anesthesia, the use of local anesthesia in UBE surgery has not yet been attempted due to frequent bony decompression and adjacent nerve tissue procedure. Shortening the surgical time as much as possible and reducing the use of general anesthesia drugs is an effective plan to further shorten hospital stay. The application of postoperative drainage tubes may also prolong postoperative hospital stay. In our experience, patients with simple nucleus pulposus removal in both groups do not place drainage, which requires strict hemostasis during surgery. Efforts should be made to reduce the occurrence of surgical complications, which can also effectively shorten hospital stay. One patient in both groups showed postoperative hematoma accompanied by gradually worsening pain symptoms in the buttocks and lower limbs. Due to the lack of significant impact on the muscle strength and sensation of the lower limbs, the hematoma removal surgery was not immediately performed, but instead continued observation. After two weeks, the lower limb symptoms gradually relieved and the hematoma was absorbed. Ahn DK et al [ 36 ] confirmed that high systolic blood pressure at extubation (≥ 170 mmHg) can influence the development of postoperative spinal epidural hematomas (PSEH) in biportal endoscopic spine surgery based on a retrospective study including 352 patients. And Fujiwara Y et al [ 37 ] demonstrated that the pre-operative high blood pressure value was the most essential risk factor for PSEH. Although asymptomatic hematoma after spinal surgery is a common phenomenon and often does not require surgical treatment, it can greatly reduce the patient's experience and satisfaction, and should be given sufficient attention. According to reports of Xie TH et al [ 38 ] , the incidence of nerve root injury in PIED surgery is 0.4% (2/479). A patient with giant free nucleus pulposus in PIED group injured the nerve root while rotating the sleeve and pulling the nerve root, resulting in postoperative pain hypersensitivity in the foot and a decrease in ankle flexor muscle strength. Under single channel endoscopy, it is usually necessary to rotate the sleeve to act as a hook to protect the nerve root and perform decompression. When dealing with giant free nucleus pulposus and highly migrated nucleus pulposus, excessive traction often causes damage to the nerves. UBED can quickly and efficiently open the dorsal space of the cranial and caudal ends to achieve pre decompression, providing protection for the next step of exposing the nucleus pulposus. A patient in UBED group suffered damage to the dural sac due to local adhesion during the removal of the ligamentum flavum, and developed cerebrospinal fluid leakage after surgery. Fortunately, they both recovered in subsequent treatment and did not experience any discomfort. The pursuit of sufficient decompression while maximizing the protection of the facet joint to avoid postoperative spinal instability has always been a concern for spinal surgeons. According to a finite element analysis, Erbulut et al [ 39 ] confirmed that when one sided facet joint resection > 50%, the range of motion increased significantly in extension and axial rotation. And the incidence of iatrogenic instability is only 0.16% reported in a meta-analysis [ 40 ] which 42 papers were reviewed and 3673 cases were identified. In PIED group, 13 patients received partial excision of the facet joint to obtain more operating space and the facet joint preservation is 99.22 ± 1.52%. In UBED group, almost all patients require partial lamina fenestration. However, only 11 patients received partial excision of the facet joint and its preservation is 96.56 ± 9.11%. Although there is a significant difference between the two sets of data, both surgical methods have little effect on spinal stability. The cost of hospitalization is also an aspect that patients and surgeons need to carefully consider, especially for people with different medical insurances. Due to the using for two different types of radiofrequency electrocoagulation devices with different energies to operate inside and outside the spinal canal, the cost of UBED is significantly higher than that of PIED. We have reason to believe that with the widespread development of this technology, more and better medical insurance policies can be incorporated, thereby reducing costs. PIED and UBED are both minimally invasive methods of traditional lumbar posterior interlaminar approach surgery, and the additional channels facilitate the surgeon's operation to a certain extent. However, UBED technique is not limited to the interlaminar approach, it can personalize surgical incisions and approaches based on the type of intervertebral disc herniation and location of nerve root compression, especially in cases of far-lateral lumbar disc herniation [ 41 ] , lateral recess stenosis and same-level foraminal stenosis [ 42 ] . Limitations We acknowledge some limitations of this study. It was retrospective in design and analyzed only short-term outcomes sample size in a single center. Therefore, larger samples and longer follow-up periods research involving multi-centers is needed. In addition, this study lacks long-term imaging follow-up on surgical segment range of motion to determine the impact of surgical methods on lumbar stability. Conclusion UBED indicates similar clinical effect compared with PIED for treating L5/S1 disc herniation, and there was no significant increase in surgical time or hospital stay. However, more facet joint damage, total blood loss and hospitalization cost may be the disadvantages of UBED technique and need to be taken seriously. Abbreviations LDH: Lumbar disc herniation; PIED: Percutaneous interlaminar endoscopic discectomy; UBED: Unilateral biportal endoscopic discectomy; ULBD: Unilateral laminotomy for bilateral decompression; MISS: Minimally invasive spine surgery; ODI: Oswestry Disability Index; VAS: Visual Analog Scale; CT: Computed tomography; MRI: magnetic resonance imaging; ASA: American Society of Anesthesiologists; Hb: hemoglobin; Hct: hematocrit; PSEH: postoperative spinal epidural hematomas; LMCSA: lean multifidus cross-sectional area; IRB: Institutional Review Board; Declarations Acknowledgement Not applicable. Authors’ Contributions LMN: Conception and design of the study, and final approval of the version to be published. JJY and TM: Acquisition of data, analysis and interpretation of data. GMG and QC: Drafting and revising the article. All authors have read and approved the manuscript. Funding This study was supported by General project of Jiangsu Provincial Department of health (H2019025); Changzhou High-level Medical Talents Training Project; Six Talent Peaks Project, Jiangsu Provincial Finance Department (WSW-186); Jiangsu Provincial Social Development Project (BE2020650); Availability of data and materials The datasets supporting the conclusions of this article are included within the article. The raw data can be requested from the corresponding author upon reasonable request. Ethics approval and consent to participate This study was approved by The Affiliated Changzhou No.2 People's Hospital with Nanjing Medical University Institutional Review Board (IRB), and due to the retrospective nature of the study, informed consent is waived by institute review board under ethics approval and consent to participate section. All procedures performed in this study were in accordance with the ethical standards of the national research committee. 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Surgical treatment for lumbar lateral recess stenosis with the full-endoscopic interlaminar approach versus conventional microsurgical technique: a prospective, randomized, controlled study. J Neurosurg Spine . 2009; 10(5): 476-485. Nie H, Zeng J, Song Y, et al. Percutaneous Endoscopic Lumbar Discectomy for L5-S1 Disc Herniation Via an Interlaminar Approach Versus a Transforaminal Approach: A Prospective Randomized Controlled Study With 2-Year Follow Up. Spine (Phila Pa 1976) . 2016; 41 Suppl 19: B30-B37. Gross JB. Estimating allowable blood loss: corrected for dilution. Anesthesiology . 1983; 58(3): 277-280. Nadler SB, Hidalgo JH, Bloch T. Prediction of blood volume in normal human adults. Surgery . 1962; 51(2): 224-232. Dohzono S, Matsumura A, Terai H, Toyoda H, Suzuki A, Nakamura H. Radiographic evaluation of postoperative bone regrowth after microscopic bilateral decompression via a unilateral approach for degenerative lumbar spondylolisthesis. J Neurosurg Spine. 2013; 18 (5): 472-478. Momin AA, Steinmetz MP. Evolution of Minimally Invasive Lumbar Spine Surgery. World Neurosurg . 2020; 140: 622-626. Zhang H, Chen ZX, Sun ZM, et al. Comparison of the Total and Hidden Blood Loss in Patients Undergoing Open and Minimally Invasive Transforaminal Lumbar Interbody Fusion. World Neurosurg . 2017; 107: 739-743. Wang H, Wang K, Lv B, et al. Analysis of risk factors for perioperative hidden blood loss in unilateral biportal endoscopic spine surgery: a retrospective multicenter study. J Orthop Surg Res . 2021; 16(1): 559. Jiang HW, Chen CD, Zhan BS, Wang YL, Tang P, Jiang XS. Unilateral biportal endoscopic discectomy versus percutaneous endoscopic lumbar discectomy in the treatment of lumbar disc herniation: a retrospective study. J Orthop Surg Res . 2022; 17(1): 30. Wang L, Li C, Han K, Chen Y, Qi L, Liu X. Comparison of Clinical Outcomes and Muscle Invasiveness between Unilateral Biportal Endoscopic Discectomy and Percutaneous Endoscopic Interlaminar Discectomy for Lumbar Disc Herniation at L5/S1 Level. Orthop Surg . 2023; 15(3): 695-703. Putowski Z, Czajka S, Krzych ŁJ. Association between Intraoperative Blood Pressure Drop and Clinically Significant Hypoperfusion in Abdominal Surgery: A Cohort Study. J Clin Med . 2021; 10(21): 5010. Li G, Sun TW, Luo G, Zhang C. Efficacy of antifibrinolytic agents on surgical bleeding and transfusion requirements in spine surgery: a meta-analysis. Eur Spine J . 2017; 26(1): 140-154. Lotan R, Lengenova S, Rijini N, Hershkovich O. Intravenous Tranexamic Acid Reduces Blood Loss in Multilevel Spine Surgeries. J Am Acad Orthop Surg . 2023; 31(4): e226-e230. Erdogan U, Sari S, Akbas A. The Efficiency of Simultaneous Systemic and Topical Use of Tranexamic Acid in Spinal Fusion Surgery. J Neurol Surg A Cent Eur Neurosurg . 2022;83(1): 46-51. Pao JL, Lin SM, Chen WC, Chang CH. Unilateral biportal endoscopic decompression for degenerative lumbar canal stenosis. J Spine Surg . 2020; 6(2): 438-446. Kim HS, Choi SH, Shim DM, Lee IS, Oh YK, Woo YH. Advantages of New Endoscopic Unilateral Laminectomy for Bilateral Decompression (ULBD) over Conventional Microscopic ULBD. Clin Orthop Surg . 2020; 12(3): 330-336. Chang H, Xu J, Yang D, Sun J, Gao X, Ding W. Comparison of full-endoscopic foraminoplasty and lumbar discectomy (FEFLD), unilateral biportal endoscopic (UBE) discectomy, and microdiscectomy (MD) for symptomatic lumbar disc herniation. Eur Spine J . 2023; 32(2): 542-554. Kim SK, Kang SS, Hong YH, Park SW, Lee SC. Clinical comparison of unilateral biportal endoscopic technique versus open microdiscectomy for single-level lumbar discectomy: a multicenter, retrospective analysis. J Orthop Surg Res . 2018; 13(1): 22. Published 2018 Jan 31. Xu J, Wang D, Liu J, et al. Learning Curve and Complications of Unilateral Biportal Endoscopy: Cumulative Sum and Risk-Adjusted Cumulative Sum Analysis. Neurospine . 2022; 19(3): 792-804. Chen L, Zhu B, Zhong HZ, et al. The Learning Curve of Unilateral Biportal Endoscopic (UBE) Spinal Surgery by CUSUM Analysis. Front Surg . 2022; 9: 873691. Kong M, Gao C, Cong W, Li G, Zhou C, Ma X. Percutaneous Endoscopic Interlaminar Discectomy with Modified Sensation-Motion Separation Anesthesia for Beginning Surgeons in the Treatment of L5-S1 Disc Herniation. J Pain Res . 2021; 14: 2039-2048. Han L, Yin J, Jiang X, Nong L. Local Anesthesia Versus General Anesthesia in Percutaneous Interlaminar Endoscopic Discectomy: A Meta-analysis. Clin J Pain . 2023; 39(6): 297-304. Ahn DK, Kim YH, Ko YR, Jang SJ, Jung JS. The Influence of Systolic Blood Pressure at the Time of Extubation on the Development of Postoperative Spinal Epidural Hematoma. Clin Orthop Surg . 2023; 15(2): 265-271. Fujiwara Y, Manabe H, Izumi B, et al. The impact of hypertension on the occurrence of postoperative spinal epidural hematoma following single level microscopic posterior lumbar decompression surgery in a single institute. Eur Spine J . 2017; 26 (10): 2606-2615. Xie TH, Zeng JC, Li ZH, et al. Complications of Lumbar Disc Herniation Following Full-endoscopic Interlaminar Lumbar Discectomy: A Large, Single-Center, Retrospective Study. Pain Physician . 2017; 20(3): E379-E387. Erbulut DU. Biomechanical effect of graded facetectomy on asymmetrical finite element model of the lumbar spine. Turk Neurosurg. 2014; 24(6): 923-928. Park DY, Upfill-Brown A, Curtin N, et al. Clinical outcomes and complications after biportal endoscopic spine surgery: a comprehensive systematic review and meta-analysis of 3673 cases. Eur Spine J. 2023; 32(8): 2637-2646. Park JH, Jung JT, Lee SJ. How I do It: L5/S1 foraminal stenosis and far-lateral lumbar disc herniation with unilateral bi-portal endoscopy. Acta Neurochir (Wien) . 2018; 160(10): 1899-1903. Tian D, Zhu B, Liu J, et al. Contralateral inclinatory approach for decompression of the lateral recess and same-level foraminal lesions using unilateral biportal endoscopy: A technical report. Front Surg . 2022; 9: 959390. Published 2022 Oct 31. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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-3965547","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":280880592,"identity":"b05a3dd6-28eb-4a25-b7fb-50ef9240c1bf","order_by":0,"name":"Jianjian YIN","email":"","orcid":"","institution":"Changzhou No.2 People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jianjian","middleName":"","lastName":"YIN","suffix":""},{"id":280880593,"identity":"722abc61-194b-4734-88ec-14f1c9b2b5e9","order_by":1,"name":"Tao MA","email":"","orcid":"","institution":"Changzhou No.2 People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Tao","middleName":"","lastName":"MA","suffix":""},{"id":280880594,"identity":"cd542601-398c-4e19-ad46-e7b7fa7b82fb","order_by":2,"name":"Gongming GAO","email":"","orcid":"","institution":"Changzhou No.2 People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Gongming","middleName":"","lastName":"GAO","suffix":""},{"id":280880595,"identity":"04b7de6d-7bba-4de7-9579-1d46ff1e34f2","order_by":3,"name":"Qi CHEN","email":"","orcid":"","institution":"Changzhou No.2 People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Qi","middleName":"","lastName":"CHEN","suffix":""},{"id":280880596,"identity":"9c8ee436-f0ca-4a6c-9b60-7dbdd3f9064f","order_by":4,"name":"Luming NONG","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAtUlEQVRIiWNgGAWjYDACdgaGAx8qbOTY2JsPEKmFmYHx4IwzacZ8PMcSiNbCfJi37XDiPIkcBeJ0mDNzJxyc2cac3saQw8Dwo2IbYS2WzbwbDnw4x5bbxnD2AGPPmduEtRgc5t1wcEYZT24bY18CM2MbkVoO87BJpLMx8xiQoqXNIIGNjRQtwEBOMGzjYUs4SJxfjvdu/vCh4r+8/PzHBx/8qCBCCwo4QKL6UTAKRsEoGAW4AABrrD9kXAV7tQAAAABJRU5ErkJggg==","orcid":"","institution":"Changzhou No.2 People's Hospital","correspondingAuthor":true,"prefix":"","firstName":"Luming","middleName":"","lastName":"NONG","suffix":""}],"badges":[],"createdAt":"2024-02-18 01:49:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3965547/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3965547/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":53014579,"identity":"b15fc398-3c19-4e81-8537-47e40c9133a6","added_by":"auto","created_at":"2024-03-19 15:52:25","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":272409,"visible":true,"origin":"","legend":"\u003cp\u003eSurgical preparation and precautions. (a) A Kirschner needle in lumbar lateral X-ray is used to make sure the surgical level is perpendicular to the ground.; (b) Anterior and posterior X-ray film with a grid shaped metal marker; (c) Mark the surface projection of the surgical level, pedicles, and midline of the spinous process; (d and e) Reconfirming the surgical level through fluoroscopy after skin incision and puncture; (f) Simultaneously operating the endoscope and electrical coagulator with both hands for surgery.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3965547/v1/30674607dc19df939ed4b09c.png"},{"id":53014581,"identity":"54ce76d8-3f30-4050-9b6f-bfa535ba8377","added_by":"auto","created_at":"2024-03-19 15:52:25","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":427292,"visible":true,"origin":"","legend":"\u003cp\u003eUBED for L5/S1 disc herniation. (a) Muscle-bone separation using the electrical coagulator; (b) Ipsilateral laminotomy resection were performed using a high-speed microdrill; (c) Expose and remove the ligamentum flavum; (d) Ipsilateral recess decompression; (e) Expose the herniated nucleus pulposus in the axillary position (arrow marked); (f) Remove the herniated nucleus pulposus; (g) Arrow marked as disc annulus fibrosus rupture; (h) Relaxation of nerve roots and dural sac indicates sufficient decompression;\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3965547/v1/96ab6ba99d4a206cfab07c76.png"},{"id":53014580,"identity":"dfcd0643-5a97-453f-acd2-93fa08d576c6","added_by":"auto","created_at":"2024-03-19 15:52:25","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":395347,"visible":true,"origin":"","legend":"\u003cp\u003eThe diagram illustrates the method of measuring the thickness of total soft tissue (a, red line), paraspinal muscles (b, yellow line), and subcutaneous layer (c, green line) at the L5/S1 intervertebral level through T2 weighted MRI sagittal view.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3965547/v1/868a94fa0af43bd2cf6fc138.png"},{"id":53014582,"identity":"e56af558-af45-4c37-8af3-053f825538fe","added_by":"auto","created_at":"2024-03-19 15:52:25","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":353891,"visible":true,"origin":"","legend":"\u003cp\u003ePercentage of facet joint preservation measured on axial CT scans obtained pre-operation and post-operation (1 day after surgery). Percentage of facet joint preservation = (a/b)×100%.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3965547/v1/34748a0ceaca55f118bc17ba.png"},{"id":64461460,"identity":"86107542-8f5f-44ae-a3f3-d4a857434c7f","added_by":"auto","created_at":"2024-09-13 12:53:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2026619,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3965547/v1/84c3a39e-a171-4078-aa1e-593647b48437.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Is unilateral biportal endoscopic discectomy superior to percutaneous interlaminar endoscopic discectomy in the treatment of L5/S1 disc herniation? A retrospective study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSince percutaneous interlaminar endoscopic discectomy (PIED) was firstly introduced by Ruetten in 2008 \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. This minimally invasive spine surgery (MISS) has been widely performed and proved to be a safe and effective treatment for lumbar disc herniation with its less paraspinal muscle damage, clear surgical vision and efficient nerve decompression, especially for L5/S1 segment \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. In previous experience \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e, uniportal full-endoscopic technique has been excellent enough in handling pure lumbar disc herniation (LDH). However, restricted by its single working channel and limited endoscopic surgical instruments. PIED can be clinically challenging in dealing with central type or highly migrated disc herniation \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e, and even cause nerve root damage when seeking sufficient decompression.\u003c/p\u003e \u003cp\u003eDifferent from the limitation of uniportal full-endoscopic vision and control space, the unilateral biportal endoscopic (UBE) technique enables surgeons to control surgical instruments more flexibly through observation and working channels to complete a wider range of decompression procedures \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. From the introduction of UBE technique to its widespread and flexible application, it has been proven by many scholars to be safe, effective, and efficient in dealing with cervical, thoracic, lumbar degenerative diseases, and even revision surgery \u003csup\u003e[\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. Although UBE technique provides a broader surgical field of view and more flexible surgical procedures, the accompanying more paraspinal muscle injuries and corresponding hidden blood loss also need to be given sufficient attention \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIs unilateral biportal endoscopic discectomy superior to percutaneous interlaminar endoscopic discectomy in the treatment of L5/S1 disc herniation? In this retrospective study, we compared the clinical efficacy and safety of PIED and UBED by assessing clinical outcome and complications among patients in the treatment of L5/S1 disc herniation.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatients\u003c/h2\u003e \u003cp\u003eWe evaluated retrospectively a series of consecutive patients who underwent surgery for L5/S1 disc herniation at a single institution between April 2021 and October 2022.\u003c/p\u003e \u003cp\u003eInclusion criteria were: (1) unilateral radicular pain, (2) central, paracentral, or prolapsed L5/S1 disc herniation, (3) failed of conservative therapies at least 6 months.\u003c/p\u003e \u003cp\u003eExclusion criteria were therefore defined: (1) intervertebral disc inflammation or tuberculosis, (2) recurrent disc herniation and multiple segments of disc herniation (3) lumbar instability, such as lumbar spondylolisthesis, (4) widely lumbar stenosis and far lateral lumbar disc herniation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eSurgical Procedures\u003c/h2\u003e \u003cp\u003eAll the surgical procedures were performed by the same senior surgeon for minimizing influence of surgical techniques.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eUBED\u003c/h2\u003e \u003cp\u003eThe patient is placed in a prone position after general anesthesia, adjusting the operating table to cause mild lumbar flexion, increasing the intervertebral space, and causing tension in the ligamentum flavum. A standard lumbar lateral X-ray is used to determine whether the surgical level is perpendicular to the ground. If not, the operating table still needs to be adjusted until satisfactory. After referring to an anterior and posterior X-ray film and using a grid shaped metal marker and a pen to mark the surface projection of the surgical level, pedicles, and midline of the spinous process, disinfection and laying can begin. We made two small portals located along the medial pedicle line. The cranial portal about 5\u0026ndash;6 mm was used for continuous irrigation and endoscopy, the caudal portal about 8\u0026ndash;10 mm was used for outflow of normal saline and working the decompression instruments. In this step, intraoperative fluoroscopy is required to confirm the surgical level (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e). After muscle-bone separation using the electrical coagulator, the lower margin of the upper lamina and interlaminar ligament were identified. Lamina fenestration was performed using a high-speed microdrill and Kerrison punches. As the interlaminar window at L5/S1 is exactly facing the intervertebral space, minimal removal of the vertebral lamina is required, unless it is an upward free prolapsed nucleus pulposus herniation. A nerve probing hook is used to make a hole in the weak area of the ligamentum flavum before flavectomy by Kerrison punches. To ensure a clear surgical field of view, pre hemostasis of small blood vessels by radiofrequency electrode in the spinal canal should be taken seriously. As the nerve roots and dura are exposed, proper ipsilateral recess decompression is needed to provide greater space for shoulder manipulation. By pushing the nerve to the opposite side through the nerve hook, most of the protruding nucleus pulposus can be completely removed. The axillary area also needs to be explored to further ensure sufficient nerve root decompression (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003ePIED\u003c/h2\u003e \u003cp\u003eThe previous studies \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e have introduced the PIED procedure in detail. PIED was performed in a prone position under general anesthesia. In preoperative fluoroscopy, the lower endplate of L5, the upper endplate of S1, the midline of the spinous process, and the lateral edge of the intervertebral space need to be marked on the skin. A dilator is inserted bluntly to the lateral edge of the interlaminar window. A working channel with an oblique angle opening towards inner side was introduced over the dilator and the final position was checked on the AP and lateral fluoroscopic images. The surgery was performed after introducing an endoscope (Joimax GmbH, Karlsruhe, Baden-W\u0026uuml;rttemberg, Germany). Soft tissues and the paraspinal muscle were cleaned by radiofrequency electrode to expose the ligamentum flavum, into which a hole was punched.\u003c/p\u003e \u003cp\u003eThe working cannula was introduced into the epidural space through this hole, and the dura margin and nerve root were exposed. By rotating the working cannula, pushing the nerve root and dura to the opposite side. Once the nerve root was well protected, shoulder and axillary exploration and discectomy can begin.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eClinical measurements\u003c/h2\u003e \u003cp\u003eGeneral information included age, gender, height, weight, body-mass index (BMI) calculation, hypertension, diabetes, history of smoking, history of alcohol use, American Society of Anesthesiologists (ASA) classification, follow-up duration and disc location.\u003c/p\u003e \u003cp\u003eConsidering the difficulty in calculating the amount of intraoperative bleeding caused by the continuous flow of normal saline during endoscopic surgery. Hemoglobin (Hb) and hematocrit (Hct) were measured preoperatively and 1 day after operation. Total blood loss (TBL), operation time, hospital stay, complications and total hospitalization costs were collected and evaluated.\u003c/p\u003e \u003cp\u003eThe TBL was calculated according to the formula proposed by Gross JB \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTBL\u0026thinsp;=\u0026thinsp;PBV \u0026times; (Hct pre - Hct post)/Hct ave;\u003c/p\u003e \u003cp\u003ePBV\u0026thinsp;=\u0026thinsp;patient\u0026rsquo;s blood volume; Hct pre\u0026thinsp;=\u0026thinsp;patient\u0026rsquo;s pre-operative hematocrit; Hct post\u0026thinsp;=\u0026thinsp;patient\u0026rsquo;s post-operative hematocrit; Hct ave = (Hct pre\u0026thinsp;+\u0026thinsp;Hct post)/2; and PBV was calculated on the basis of the Nadler formula \u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003ePBV (ml)\u0026thinsp;=\u0026thinsp;k1 \u0026times; height (m) \u003csup\u003e3\u003c/sup\u003e+ k2 \u0026times; weight (kg)\u0026thinsp;+\u0026thinsp;k3, For men, k1\u0026thinsp;=\u0026thinsp;0.3669, k2\u0026thinsp;=\u0026thinsp;0.03219, and k3\u0026thinsp;=\u0026thinsp;0.6041, for women k1\u0026thinsp;=\u0026thinsp;0.3561, k2\u0026thinsp;=\u0026thinsp;0.03308, and k3\u0026thinsp;=\u0026thinsp;0.1833.\u003c/p\u003e \u003cp\u003eVisual analog scale (VAS) back pain and leg pain were assessed by 2 experienced clinical researchers preoperatively, 1 day after operation and at last follow-up. The Oswestry Disability Index (ODI) score and the modified MacNab criteria were evaluated preoperatively and at last follow-up.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eRadiologic measurements\u003c/h2\u003e \u003cp\u003eThe total soft-tissue thickness, subcutaneous layer thickness, and paraspinal muscle thickness at L5/S1 level were independently measured by two experienced spinal surgeons on lumbar sagittal MRI images (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Approach side percentage of facet joint preservation \u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e measured on axial CT scans obtained pre-operation and post-operation (1 day after operation) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eFor statistical analysis, the SPSS 22.0 (SPSS Inc, Chicago, IL, USA) was used, and the P value less than 0.05 were considered significant. Measurement data are expressed as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (x\u0026thinsp;\u0026plusmn;\u0026thinsp;s). Comparisons between groups were performed by one-way analysis of variance and t-tests. Comparisons of the count data between the two groups, were performed using chi-square test.\u003c/p\u003e \u003c/div\u003e"},{"header":"Result","content":"\u003cdiv id=\"Sec11\"\u003e\n \u003ch2\u003ePatient population\u003c/h2\u003e\n \u003cp\u003eNinety-six patients met the inclusion criteria. All patients had lumbar disc herniation at L5/S1. Forty-six patients underwent UBED, and fifty patients underwent PIED. The cohort study included 40 women and 56 men, and their mean age was 43.85\u0026thinsp;\u0026plusmn;\u0026thinsp;11.41 years and 45.64\u0026thinsp;\u0026plusmn;\u0026thinsp;13.60 years, respectively. The mean follow-up period was 14.07\u0026thinsp;\u0026plusmn;\u0026thinsp;3.50 months in UBED group, and 14.52\u0026thinsp;\u0026plusmn;\u0026thinsp;5.37 months in PIED group.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\"\u003e\n \u003ch2\u003eClinical outcome\u003c/h2\u003e\n \u003cp\u003eThe total blood loss and the hospitalization cost was more in the UBED Group (394.16\u0026thinsp;\u0026plusmn;\u0026thinsp;227.96ml, 37008.70\u0026thinsp;\u0026plusmn;\u0026thinsp;3063.63 RMB) compared with PIED Group (273.83\u0026thinsp;\u0026plusmn;\u0026thinsp;158.53 ml, 31244.12\u0026thinsp;\u0026plusmn;\u0026thinsp;2202.45 RMB) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, P\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table \u003cspan\u003e1\u003c/span\u003e). The operative time and hospital stay time in the UBED Group (80.98\u0026thinsp;\u0026plusmn;\u0026thinsp;33.61 min, 5.54\u0026thinsp;\u0026plusmn;\u0026thinsp;1.92 day) was similar with that in PIED Group (89.42\u0026thinsp;\u0026plusmn;\u0026thinsp;32.16 min. 5.24\u0026thinsp;\u0026plusmn;\u0026thinsp;1.89 day) (P\u0026thinsp;=\u0026thinsp;0.212, P\u0026thinsp;=\u0026thinsp;0.437) (Table \u003cspan\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\u003c/table\u003e\n \u003cp\u003eThe postoperative VAS back, leg scores and ODI score were significantly improved compared with the preoperative scores in both two groups (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, respectively). There was no significant difference in VAS back and leg scores between two groups at 1-day post-operation and final follow-up period (P\u0026thinsp;=\u0026thinsp;0.172, P\u0026thinsp;=\u0026thinsp;0.65, P\u0026thinsp;=\u0026thinsp;0.372, P\u0026thinsp;=\u0026thinsp;0.063, respectively). All patients of two groups had similar ODI scores at final follow-up period (P\u0026thinsp;=\u0026thinsp;0.071) (Table \u003cspan\u003e2\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eTable 1 \u0026nbsp; Demographic and clinical characteristics for all the patients\u003c/strong\u003e\u003c/p\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"733\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003eUBED\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003ePIED\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003eP-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eNo of cases\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eAge (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e43.85\u0026plusmn;11.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e45.64\u0026plusmn;13.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.488\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eBMI (kg/㎡)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e24.83\u0026plusmn;3.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e24.70\u0026plusmn;4.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.878\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.369\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eFemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eHypertension (n)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.834\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eDiabetes mellitus (n)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.479\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eHistory of smoking\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.752\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eHistory of alcohol use\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.357\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eASA classification (n)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.452\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eII\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eIII\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eDisc Location\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.916\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eCentral\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eParacentral\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eSoft tissue thickness (cm) \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e52.66\u0026plusmn;8.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e50.18\u0026plusmn;9.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.182\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eParaspinal muscle thickness (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e33.51\u0026plusmn;4.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e31.86\u0026plusmn;5.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.116\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eSubcutaneous layer thickness (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e19.15\u0026plusmn;7.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e18.33\u0026plusmn;7.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.606\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eOperation time (min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e80.98\u0026plusmn;33.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e89.42\u0026plusmn;32.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.212\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eHospital stay time (day)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e5.54\u0026plusmn;1.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e5.24\u0026plusmn;1.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.437\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eTotal cost (RMB)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e37008.70\u0026plusmn;3063.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e31244.12\u0026plusmn;2202.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eFollow up time (months)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e14.07\u0026plusmn;3.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e14.52\u0026plusmn;5.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.622\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eTotal blood loss (ml)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e394.16\u0026plusmn;227.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e273.83\u0026plusmn;158.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003ePre-op Hb (g/L)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e145.80\u0026plusmn;17.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e144.94\u0026plusmn;16.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.806\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003ePost-op Hb (g/L)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e132.48\u0026plusmn;15.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e136.00\u0026plusmn;15.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eHb loss, g/L (g/L)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e13.33\u0026plusmn;8.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e8.94\u0026plusmn;6.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003ePre-op Hct (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e42.77\u0026plusmn;4.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e42.31\u0026plusmn;4.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.631\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003ePost-op Hct (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e39.10\u0026plusmn;5.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e39.792\u0026plusmn;4.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.464\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eHct loss (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e3.68\u0026plusmn;2.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e2.52\u0026plusmn;1.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eComplications\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eNerve root injury\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003ePostopreative hematoma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eDural tear\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eModified MacNab evaluation (excellent/good/fair/poor)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e24/21/1/0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e21/27/2/0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eExcellent/good rate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e97.80%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e96%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.607\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"55.7980900409277%\" valign=\"bottom\"\u003e\n \u003cp\u003eFacet joint preservation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e96.56 \u0026plusmn; 9.11%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.281036834924965%\" valign=\"bottom\"\u003e\n \u003cp\u003e99.22 \u0026plusmn; 1.52%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.639836289222374%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cdiv\u003e\n \u003cdiv align=\"left\"\u003e\u003cstrong\u003eTable 2 \u0026nbsp; Comparisons of clinical outcomes between the two groups\u003c/strong\u003e\u003c/div\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"576\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003eUBED\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003ePIED\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003eP value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eVAS leg score\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003ePreoperation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e7.87\u0026plusmn;0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e7.78\u0026plusmn;0.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.333\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 day postoperation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.67\u0026plusmn;0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.84\u0026plusmn;0.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.172\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eFinal follow-up\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.22\u0026plusmn;0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.18\u0026plusmn;0.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eP value (pre-final)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eVAS lumbar score\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003ePreoperation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e6.46\u0026plusmn;0.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e6.38\u0026plusmn;0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.517\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 day postoperation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e2.11\u0026plusmn;0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e2.20\u0026plusmn;0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.372\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eFinal follow-up\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.37\u0026plusmn;0.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.56\u0026plusmn;0.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.063\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eP value (pre-final)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eODI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003ePreoperation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e58.78\u0026plusmn;4.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e59.94\u0026plusmn;4.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.187\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eFinal follow-up\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e16.78\u0026plusmn;2.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e18.00\u0026plusmn;3.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.0625%\" valign=\"bottom\"\u003e\n \u003cp\u003eP value (pre-final)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.916666666666668%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.104166666666666%\" valign=\"bottom\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv\u003e\n \u003c/div\u003e\n \u003cp\u003ePatient satisfaction rates were 97.8% and 96% in UBED group and PIED group based on MacNab criteria, and there was no significant difference in patient satisfaction rates between two groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n \u003cp\u003eA patient with giant free nucleus pulposus in PIED group injured the nerve root resulting in postoperative pain hypersensitivity in the foot and a decrease in ankle flexor muscle strength. A patient in UBED group suffered damage to the dural sac due to local adhesion and developed cerebrospinal fluid leakage after surgery. They both recovered in subsequent treatment and did not experience any discomfort. One patient in both groups showed postoperative hematoma accompanied by gradually worsening pain symptoms in the buttocks and lower limbs. After two weeks, the lower limb symptoms gradually relieved and the hematoma was absorbed.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\"\u003e\n \u003ch2\u003eRadiologic measurements\u003c/h2\u003e\n \u003cp\u003eThe total soft-tissue, subcutaneous layer and paraspinal muscle thickness at L5/S1 level showed no significant difference between two groups (Table \u003cspan\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e11 patients received partial excision of the facet joint in UBED group and 13 patients in PIED group. The percentage of facet joint preservation is 96.56\u0026thinsp;\u0026plusmn;\u0026thinsp;9.11% in UBED group, which is significantly less than in PIED group with 99.22\u0026thinsp;\u0026plusmn;\u0026thinsp;1.52%.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eMinimally invasive spinal surgery (MISS) has developed rapidly in recent years, and more and more spinal degenerative diseases can be effectively treated through MISS \u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. For patients undergoing general anesthesia surgery, it is necessary to have a correct understanding of the amount of bleeding during endoscopic surgery, which is crucial for ensuring patient safety. Due to the continuous flushing of normal saline during surgery, it has always been difficult to calculate the amount of bleeding during endoscopic surgery. In addition, surgeons often ignore the presence of hidden blood loss after endoscopic surgery. By referring to the published literature \u003csup\u003e[\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e, we only calculated the total bleeding volume based on the changes in hematocrit before and after surgery. On the premise that there is no significant difference in baseline data before surgery and operation time. The total bleeding volume in UBED group is greater than that in PIED group, which is statistically significant. This result may be caused by several reasons and requires our attention. While muscle-bone separation using the electrical coagulator on the surface of the vertebral lamina, UBED requires a larger range of muscle and soft tissue dissection to obtain greater operating space. Wang L et al \u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e indicated the serum CPK level and change rate of lean multifidus cross-sectional area (LMCSA) for UBED was obviously higher than PIED at postoperative 1st day. Unlike PIED surgical instruments only used in work channel, various surgical instruments repeatedly enter and exit the surgical area through skin incisions during the operation of UBED, which can easily damage intermuscular blood vessels and cause bleeding. More vertebral lamina bone needs to be drilled to obtain a better range of vertebral canal fenestration in UBED compared with PIED. This usually means more oozing from trabecular bone, especially after continuous saline flushing stops. Sometimes, although the field of vision is very clear under continuous infusion of saline, bleeding is occurring outside the field of vision and is not detected.\u003c/p\u003e \u003cp\u003ePerioperative blood pressure control also has a significant impact on the amount of bleeding during water-based endoscopic surgery in prone position. Surgeons often hope that anesthesiologists can control the patient's blood pressure at low level during surgery, thereby reducing bleeding in the endoscopic surgical field and ensuring clear and efficient surgery. However, Putowski Z et al \u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e found that extending durations of low mean arterial pressure were associated with the development of either acute kidney injury, myocardial infarction or stroke. Perioperative blood pressure management that is too high, too low, or fluctuates significantly can pose a threat to the patient's safety.\u003c/p\u003e \u003cp\u003eA meta-analysis \u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e involving 1191 patients confirmed that application of antifibrinolytic agents were able to effectively reduce perioperative blood loss and transfusion requirements in spine surgery. Lotan R et al \u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e reported that a routine administration of preoperative weight-independent 1 g intravenous topical tranexamic acid protocol is efficacious and safe in reducing perioperative blood loss for lumbar multilevel laminectomies. Based on a retrospective study \u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e included 112 patients receiving lumbar fusion surgery, intra- and postoperative blood loss and need for transfusion were significantly lower in the tranexamic acid group. To avoid other potential risks associated with excessive blood pressure regulation, perioperative use of hemostatic drugs seems to be a good way to reduce bleeding during endoscopic surgery.\u003c/p\u003e \u003cp\u003eGenerally speaking, the efficacy of endoscopic surgery is immediately apparent after anesthesia and wakefulness, and is highly valued. According to the MacNab criteria, the excellence/good rates in the PIED group and UBED group are similar. In our study, we observed significant improvements in the leg scores and ODI score at one day post-operation and the final follow-up time. And, there were no significant differences in the improvements of lower limb symptom and function between two groups, showing that the two procedures were equally effective in the decompression for LDH in L5/S1. Adequate decompression range usually represents effective nerve relaxation and indicates better improvement in lower limb symptoms. Based on Pao JL et al\u0026rsquo; s study \u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e, the measured cross-sectional dural area at the most stenotic axial image on MRI was significantly enlarged from 71.4\u0026thinsp;\u0026plusmn;\u0026thinsp;36.5 to 177.3\u0026thinsp;\u0026plusmn;\u0026thinsp;59.2 mm\u003csup\u003e2\u003c/sup\u003e after UBE decompression. Kim HS et al \u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e confirmed that there was no significant difference in dura expansion (329.71\u0026thinsp;\u0026plusmn;\u0026thinsp;54.21 vs. 315.20\u0026thinsp;\u0026plusmn;\u0026thinsp;62.79) between UBED and Conventional Microscopic ULBD. Usually, such extensive decompression is not necessary to cope with lumbar disc herniation, which is characterized by a high incidence of unilateral lower limb symptoms. For those who habitually use UBE technology to treat spinal stenosis, treating lumbar disc herniation is simpler and more feasible.\u003c/p\u003e \u003cp\u003eIn our study, VAS back scores did not show significant differences due to differences in the extent of injury to the paravertebral muscles. Chang H et al \u003csup\u003e[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e indicated that UBED enables comparable result to conventional microdiscectomy regarding perioperative parameters and clinical outcomes. People who underwent UBED complains less back pain in the immediate postoperative period. Similarly, Kim SK et al \u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e confirmed that back VAS score in the UBED group showed significantly more improvement than that in the microdiscectomy group at one-week post-operation. More laminectomy and muscle dissection during UBED surgery did not significantly improve postoperative VAS back pain scores, which established confidence in our extensive minimally invasive surgery in the later stage.\u003c/p\u003e \u003cp\u003eIn our study, the operation time of UBED and PIED group is 80.98\u0026thinsp;\u0026plusmn;\u0026thinsp;33.61 min and 89.42\u0026thinsp;\u0026plusmn;\u0026thinsp;32.16 min. Although there is a difference between the two group, it is not statistically significant. The indicator of operation time varies greatly in each independent study, which is closely related to the surgeon's own level of technical proficiency. As the learning curve progresses and proficiency improves, surgical time decreases. Xu J et al \u003csup\u003e[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e investigated that the operation time of UBED in learning phase, practicing phase and mastery phase is 152.92\u0026thinsp;\u0026plusmn;\u0026thinsp;26.33 min, 124.45\u0026thinsp;\u0026plusmn;\u0026thinsp;37.07 min and 117.36\u0026thinsp;\u0026plusmn;\u0026thinsp;17.06 min, respectively. Similarly, Chen L et al \u003csup\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e found that the operation time of late 73 cases is 90.5\u0026thinsp;\u0026plusmn;\u0026thinsp;27.8 min, which is significantly shorter than the early 24 cases (120.3\u0026thinsp;\u0026plusmn;\u0026thinsp;43.8 min). The type of lumbar disc herniation is also an important factor affecting operation time. For giant herniated and prolapsed intervertebral disc herniation, the surgical time will also be correspondingly extended. In order to ensure that the nerve is not subjected to excessive traction when removing the nucleus pulposus, a larger dorsal space needs to be opened and reserved. This means extensive bone and ligamentum flavum tissue decompression on the dorsal side.\u003c/p\u003e \u003cp\u003eIn terms of hospitalization time, there was no significant difference between the two groups of surgical patients, possibly because both surgical methods used the same anesthesia method, which resulted in little difference in postoperative observation time for patients. Although there have been recent literatures \u003csup\u003e[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e report on a considerable number of cases of PIED surgery under local anesthesia, the use of local anesthesia in UBE surgery has not yet been attempted due to frequent bony decompression and adjacent nerve tissue procedure. Shortening the surgical time as much as possible and reducing the use of general anesthesia drugs is an effective plan to further shorten hospital stay. The application of postoperative drainage tubes may also prolong postoperative hospital stay. In our experience, patients with simple nucleus pulposus removal in both groups do not place drainage, which requires strict hemostasis during surgery.\u003c/p\u003e \u003cp\u003eEfforts should be made to reduce the occurrence of surgical complications, which can also effectively shorten hospital stay. One patient in both groups showed postoperative hematoma accompanied by gradually worsening pain symptoms in the buttocks and lower limbs. Due to the lack of significant impact on the muscle strength and sensation of the lower limbs, the hematoma removal surgery was not immediately performed, but instead continued observation. After two weeks, the lower limb symptoms gradually relieved and the hematoma was absorbed. Ahn DK et al \u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e confirmed that high systolic blood pressure at extubation (\u0026ge;\u0026thinsp;170 mmHg) can influence the development of postoperative spinal epidural hematomas (PSEH) in biportal endoscopic spine surgery based on a retrospective study including 352 patients. And Fujiwara Y et al \u003csup\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e demonstrated that the pre-operative high blood pressure value was the most essential risk factor for PSEH. Although asymptomatic hematoma after spinal surgery is a common phenomenon and often does not require surgical treatment, it can greatly reduce the patient's experience and satisfaction, and should be given sufficient attention.\u003c/p\u003e \u003cp\u003eAccording to reports of Xie TH et al \u003csup\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e, the incidence of nerve root injury in PIED surgery is 0.4% (2/479). A patient with giant free nucleus pulposus in PIED group injured the nerve root while rotating the sleeve and pulling the nerve root, resulting in postoperative pain hypersensitivity in the foot and a decrease in ankle flexor muscle strength. Under single channel endoscopy, it is usually necessary to rotate the sleeve to act as a hook to protect the nerve root and perform decompression. When dealing with giant free nucleus pulposus and highly migrated nucleus pulposus, excessive traction often causes damage to the nerves. UBED can quickly and efficiently open the dorsal space of the cranial and caudal ends to achieve pre decompression, providing protection for the next step of exposing the nucleus pulposus. A patient in UBED group suffered damage to the dural sac due to local adhesion during the removal of the ligamentum flavum, and developed cerebrospinal fluid leakage after surgery. Fortunately, they both recovered in subsequent treatment and did not experience any discomfort.\u003c/p\u003e \u003cp\u003eThe pursuit of sufficient decompression while maximizing the protection of the facet joint to avoid postoperative spinal instability has always been a concern for spinal surgeons. According to a finite element analysis, Erbulut et al \u003csup\u003e[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/sup\u003e confirmed that when one sided facet joint resection\u0026thinsp;\u0026gt;\u0026thinsp;50%, the range of motion increased significantly in extension and axial rotation. And the incidence of iatrogenic instability is only 0.16% reported in a meta-analysis \u003csup\u003e[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/sup\u003e which 42 papers were reviewed and 3673 cases were identified. In PIED group, 13 patients received partial excision of the facet joint to obtain more operating space and the facet joint preservation is 99.22\u0026thinsp;\u0026plusmn;\u0026thinsp;1.52%. In UBED group, almost all patients require partial lamina fenestration. However, only 11 patients received partial excision of the facet joint and its preservation is 96.56\u0026thinsp;\u0026plusmn;\u0026thinsp;9.11%. Although there is a significant difference between the two sets of data, both surgical methods have little effect on spinal stability.\u003c/p\u003e \u003cp\u003eThe cost of hospitalization is also an aspect that patients and surgeons need to carefully consider, especially for people with different medical insurances. Due to the using for two different types of radiofrequency electrocoagulation devices with different energies to operate inside and outside the spinal canal, the cost of UBED is significantly higher than that of PIED. We have reason to believe that with the widespread development of this technology, more and better medical insurance policies can be incorporated, thereby reducing costs.\u003c/p\u003e \u003cp\u003ePIED and UBED are both minimally invasive methods of traditional lumbar posterior interlaminar approach surgery, and the additional channels facilitate the surgeon's operation to a certain extent.\u003c/p\u003e \u003cp\u003eHowever, UBED technique is not limited to the interlaminar approach, it can personalize surgical incisions and approaches based on the type of intervertebral disc herniation and location of nerve root compression, especially in cases of far-lateral lumbar disc herniation \u003csup\u003e[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/sup\u003e, lateral recess stenosis and same-level foraminal stenosis \u003csup\u003e[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eWe acknowledge some limitations of this study. It was retrospective in design and analyzed only short-term outcomes sample size in a single center. Therefore, larger samples and longer follow-up periods research involving multi-centers is needed. In addition, this study lacks long-term imaging follow-up on surgical segment range of motion to determine the impact of surgical methods on lumbar stability.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eUBED indicates similar clinical effect compared with PIED for treating L5/S1 disc herniation, and there was no significant increase in surgical time or hospital stay. However, more facet joint damage, total blood loss and hospitalization cost may be the disadvantages of UBED technique and need to be taken seriously.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eLDH: Lumbar disc herniation; PIED: Percutaneous interlaminar endoscopic discectomy; UBED: Unilateral biportal endoscopic discectomy; ULBD: Unilateral laminotomy for bilateral decompression; MISS: Minimally invasive spine surgery; ODI: Oswestry Disability Index; VAS: Visual Analog Scale; CT: Computed tomography; MRI: magnetic resonance imaging; ASA: American Society of Anesthesiologists; Hb: hemoglobin; Hct: hematocrit; PSEH: postoperative spinal epidural hematomas; LMCSA: lean multifidus cross-sectional area; IRB: Institutional Review Board;\u003c/p\u003e\n"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLMN: Conception and design of the study, and final approval of the version to be published. JJY and TM: Acquisition of data, analysis and interpretation of data. GMG and QC: Drafting and revising the article. All authors have read and approved the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by General project of Jiangsu Provincial Department of health (H2019025); Changzhou High-level Medical Talents Training Project; Six Talent Peaks Project, Jiangsu Provincial Finance Department (WSW-186); Jiangsu Provincial Social Development Project (BE2020650);\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets supporting the conclusions of this article are included within the article. The raw data can be requested from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by The Affiliated Changzhou No.2 People\u0026apos;s Hospital with Nanjing Medical University Institutional Review Board (IRB), and due to the retrospective nature of the study, informed consent is waived by institute review board under ethics approval and consent to participate section. All procedures performed in this study were in accordance with the ethical standards of the national research committee.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have declared that no competing interests exist.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRuetten S, Komp M, Merk H, Godolias G. 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Published 2022 Oct 31.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"lumbar disc herniation, unilateral biportal endoscopic discectomy, percutaneous interlaminar endoscopic discectomy, total blood loss, facet joint preservation","lastPublishedDoi":"10.21203/rs.3.rs-3965547/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3965547/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e \u003cp\u003eTo compare the clinical outcomes of unilateral biportal endoscopic discectomy (UBED) and percutaneous interlaminar endoscopic discectomy (PIED) for treating L5/S1 disc herniation.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003ePatients with L5/S1 disc herniation treated with UBED (n\u0026thinsp;=\u0026thinsp;46) and PIED (n\u0026thinsp;=\u0026thinsp;50) in our hospital during the same period were retrospectively reviewed. Total blood loss (TBL), operation time, hospital stay, complications, total hospitalization costs, clinical efficacy and modified MacNab criteria were collected and evaluated. Percentage of facet joint preservation measured on axial CT scans obtained pre-operation and post-operation.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe mean follow-up period was 14.07\u0026thinsp;\u0026plusmn;\u0026thinsp;3.50 months in UBED group, and 14.52\u0026thinsp;\u0026plusmn;\u0026thinsp;5.37 months in PIED group. The total blood loss and hospitalization cost was more in the UBED Group. The operative time and hospital stay time in the UBED Group was similar with that in PIED Group. The postoperative VAS back, leg scores and ODI score were significantly improved compared with the preoperative scores in both two groups. There was no significant difference in VAS back and leg scores between two groups at 1-day post-operation and final follow-up period. All patients of two groups had similar ODI scores at final follow-up period. The percentage of facet joint preservation is 96.56\u0026thinsp;\u0026plusmn;\u0026thinsp;9.11% in UBED group, which is significantly less than in PIED group with 99.22\u0026thinsp;\u0026plusmn;\u0026thinsp;1.52%. One patient in both groups showed postoperative hematoma. A dural tear occurred in UBED group and a never root injury occurred in PIED group. There was no significant difference in patient satisfaction rates between two groups.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eUBED indicates similar clinical effect compared with PIED for treating L5/S1 disc herniation, and there was no significant increase in surgical time or hospital stay. However, more facet joint damage, total blood loss and hospitalization cost may be the disadvantages of UBED technique and need to be taken seriously.\u003c/p\u003e","manuscriptTitle":"Is unilateral biportal endoscopic discectomy superior to percutaneous interlaminar endoscopic discectomy in the treatment of L5/S1 disc herniation? 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