Preoperative Trajectory Planning for Minimally Invasive Removal of Sacroiliac Screws: A Retrospective Cohort Study

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Although robot-assisted techniques can improve accuracy, they are associated with high costs. This study aimed to evaluate the feasibility of a "preoperative trajectory planning method" based on preoperative imaging and trigonometric calculation for the removal of sacroiliac screws. Methods: We conducted a retrospective cohort study of 36 patients who underwent sacroiliac screw removal between January 2018 and December 2024. The patients were divided into three groups: a modified group (n=14, using the new method), a traditional group (n=13, relying on intraoperative fluoroscopy for freehand exploration), and a robot-assisted group (n=9, using the TiRobot orthopedic robot). The reasons for screw removal were analyzed, and the operative time, number of intraoperative fluoroscopies, and hospitalization costs were compared among the three groups. Results: All screws were successfully removed. The mean operative time in the modified group (18.6 ± 12.9 minutes) was significantly shorter than that in both the traditional group (25.8 ± 8.8 minutes) and the robot-assisted group (31.1 ± 8.9 minutes) (all P < 0.05). The mean number of fluoroscopies in the modified group (5.9 ± 2.5) showed no significant difference from the robot-assisted group (5.0 ± 2.9), but both were significantly lower than the traditional group (13.2 ± 5.4, P < 0.01). The hospitalization cost in the robot-assisted group (11480.94 ± 472.63 CNY) was significantly higher than that in both the modified and traditional groups (P < 0.01). Conclusion: The "preoperative trajectory planning method" enables precise and efficient removal of sacroiliac screws without reliance on expensive robotic equipment. This method features a short learning curve, reduces operative time and intraoperative radiation exposure, and does not impose an additional financial burden on patients, demonstrating good potential for broad clinical application. Figures Figure 1 Figure 2 Introduction Pelvic fractures occur in 8%-16% of trauma patients, with their incidence increasing annually alongside the rapid development of transportation and construction industries [ 1 , 2 ] . Surgical treatment has become the consensus for unstable posterior pelvic ring injuries. Percutaneous sacroiliac screw fixation is currently one of the most commonly used techniques for managing posterior pelvic ring injuries, favored by many clinicians due to its minimally invasive nature, biomechanical stability, short operative time, and low infection risk [ 3 – 6 ] . However, controversy persists regarding the necessity of removing sacroiliac screws after fracture healing [ 7 – 9 ] . Due to the deep location of the screws and substantial overlying soft tissue coverage, minimally invasive removal is challenging. Intraoperative repeated fluoroscopy is often required, and removal time can even exceed the initial implantation time, causing significant trauma to the patient [ 10 , 11 ] . With the application of robotic navigation technology, we have also employed robot-assisted removal in clinical practice, but this imposes high costs on patients. We believe the primary difficulty in sacroiliac screw removal lies in the intraoperative uncertainty of the screw's spatial trajectory. Therefore, we proposed a novel hypothesis: by utilizing the patient's preoperative imaging combined with an arcsine function formula, the inclination angles of the sacroiliac screw in the transverse and coronal planes can be measured. Subsequently, combined with intraoperative lateral fluoroscopy to locate the screw tail, this would allow for faster and more accurate screw removal. We compared this "Preoperative Trajectory Planning Method" with traditional and robot-assisted methods to validate its feasibility and advantages. Patients and Methods This is a retrospective cohort study. The study protocol adhered to the principles of the Declaration of Helsinki and was approved by our hospital's ethics committee (Number: BYYFY-2022KY027). Informed consent for the surgical procedure was obtained from all patients or their families prior to surgery. A total of 36 patients meeting the criteria who underwent sacroiliac screw removal at our hospital between January 2018 and December 2024 were ultimately included. All surgeries were performed by the same experienced trauma surgeon specializing in pelvic fractures to control for operator variability. Inclusion criteria (1) Underwent sacroiliac screw removal at our hospital; (2) No breakage of the sacroiliac screw. Exclusion criteria (1) Comorbid severe cardiac, pulmonary, hepatic, or renal insufficiency precluding tolerance for surgery; (2) History of sacroiliac joint infection or tumor; (3) Follow-up time less than 6 months. The choice of surgical technique was based on institutional trends over different periods: Before November 2021: The team had not introduced robotic navigation, thus the traditional method was used. From November 2021 (when our hospital introduced the TiRobot) to October 2022, we used robot-assisted removal. After October 2022, the team proposed the "Preoperative Trajectory Planning Method," and this technique has been used since. Based on the actual intraoperative method, the 36 patients were divided into three groups: the "Modified Group" using the Preoperative Trajectory Planning Method, the "Traditional Group" using the conventional method, and the "Robot-assisted Group" using robot assistance. Surgical Technique Modified Group: Through preoperative AP and lateral pelvic radiographs, we obtain the screw's inclination angle in the coronal plane (coronal angle, θ) and the inclination angle in the transverse plane (transverse angle, α): From the AP view, we measure the angle formed by the extended line of the screw trajectory and the line connecting both anterior superior iliac spines (ASIS), which is θ. From the lateral view, we obtain the distance (H) between the screw head and tail in the sagittal plane. Combined with the screw length (L) and the arcsine function formula α = arcsin (opposite/hypotenuse), where the opposite side is H and the hypotenuse is L, we calculate the transverse angle α = arcsin(H/L) (Fig. 1 ). After satisfactory anesthesia, the patient is placed supine on a radiolucent carbon fiber operating table. The coronal plane angle θ is marked on the skin surface. The original incision is opened, and a 2.5mm Kirschner wire (K-wire) is inserted. Under lateral pelvic fluoroscopy, the tip of the K-wire is placed at the screw tail. While adjusting the K-wire along the marked coronal angle θ, the insertion direction is fine-tuned by referencing the calculated transverse angle α. This allows the K-wire to be smoothly inserted into the cannulated screw. After dilating the pathway with forceps, the screwdriver is used to remove the sacroiliac screw. Traditional Group: After satisfactory anesthesia, the patient is placed supine on a radiolucent carbon fiber operating table. The original incision is opened, and a 2.5mm K-wire is inserted. The K-wire trajectory is continuously adjusted using intraoperative fluoroscopy of the pelvic inlet and outlet views, and lateral fluoroscopy is used to locate the screw tail. Once positioned, a guidewire is inserted. After dilating the pathway with forceps, the screwdriver is used to remove the sacroiliac screw. Robot-assisted Group: After satisfactory anesthesia, the patient is placed supine on a radiolucent carbon fiber operating table. A patient tracker is fixed to the contralateral ASIS. Fluoroscopic images of the pelvic inlet, lateral, and outlet views are acquired and uploaded to the main control computer. The screw trajectory is then planned according to the existing sacroiliac screw path (Fig. 2 ). After planning, the robotic arm is maneuvered to the designated position. The original incision is opened, and the guidewire is inserted. At this point, the guidewire is successfully inserted into the cannulated sacroiliac screw. After dilating the pathway with forceps, the screwdriver is used to remove the screw. Postoperative Management Postoperative management included analgesic and supportive care. Patients were encouraged to perform hip and knee joint functional exercises during bed rest. Ambulation was initiated within one week postoperatively based on recovery progress. All patients completed at least 6 months of follow-up (mean follow-up: 13.5 ± 5.4 months). Follow-up data for all enrolled patients was complete, with no lost cases. Outcome Measures Primary outcome measures Mean operative time per sacroiliac screw removed and mean number of intraoperative fluoroscopies per screw. Secondary outcome measures Patient baseline data (age, gender), number of screws removed, main reason for removal request, total hospitalization cost, and pain relief at the sacroiliac joint region at 6 months postoperatively [For all patients who underwent removal due to pain, Visual Analog Scale (VAS) scores preoperatively and at 6 months postoperatively were compared. The overall pain relief rate (percentage of patients with a VAS reduction ≥ 2 points) was calculated]. Statistical Analysis Statistical analysis was performed using SPSS 22.0 (SPSS, Chicago, IL). Continuous variables, after confirmation of normal distribution by Shapiro-Wilk test and homogeneity of variance by Levene's test, are presented as mean ± standard deviation (x̄ ± s). Comparisons among the three groups were performed using one-way ANOVA, and if a significant difference was found, post-hoc pairwise comparisons were conducted using the Least Significant Difference (LSD) method. Categorical variables are presented as frequency and percentage [n (%)], with comparisons among groups performed using the chi-square test or Fisher's exact test. A P-value < 0.05 was considered statistically significant. Results A total of 36 patients were included in the final analysis: 14 in the Modified Group, 13 in the Traditional Group, and 9 in the Robot-assisted Group. All sacroiliac screws were successfully removed without residual hardware. There were no statistically significant differences among the three groups in terms of age, gender distribution, total number of screws removed, or the main reason for removal request (P > 0.05), indicating balanced baseline characteristics and comparability (Table 1 ). Among the 36 patients, 15 requested removal due to fertility planning; 10 due to psychological factors (inability to accept retained hardware); 10 due to significant sacroiliac joint pain/discomfort; and 1 due to postoperative lower limb neurological symptoms (which gradually resolved after timely screw removal). Regarding primary outcomes, the mean operative time per screw in the Modified Group was 18.6 ± 12.9 min, significantly shorter than both the Traditional Group (25.8 ± 8.8 min) and the Robot-assisted Group (31.1 ± 8.9 min) (P < 0.05). No significant difference was found between the Traditional and Robot-assisted Groups. The mean number of intraoperative fluoroscopies per screw in the Modified Group was 5.9 ± 2.5, showing no significant difference from the Robot-assisted Group (5.0 ± 2.9) (P > 0.05), but both were significantly lower than the Traditional Group (13.2 ± 5.4) (P < 0.01). Regarding cost, the mean total hospitalization cost in the Modified Group was 5281.75 ± 473.92 CNY, and 5614.07 ± 643.73 CNY in the Traditional Group, with no significant difference between these two groups (P > 0.05). The mean total hospitalization cost in the Robot-assisted Group was significantly higher at 11480.94 ± 472.63 CNY, significantly exceeding both the Modified and Traditional Groups (P < 0.01). A summary analysis of the 10 patients who underwent removal due to pain showed the mean VAS score significantly decreased from 6.5 ± 1.3 preoperatively to 2.4 ± 1.1 at 6 months postoperatively (mean ΔVAS: 4.1 ± 1.2, p < 0.001). The overall pain relief rate was 80% (8/10) (Table 2 ). Table 1 Baseline Patient Characteristics and Reasons for Removal Characteristic Modified Group (n = 14) Traditional Group (n = 13) Robot-assisted Group (n = 9) P-value Age (years, x̄ ± s) 30.7 ± 18.8 33.2 ± 15.2 33.0 ± 14.8 0.905 Gender [n (%)] 0.838 Male 3 (21.4%) 3 (23.1%) 2 (22.2%) Female 11 (78.6%) 10 (76.9%) 7 (77.8%) Main Reason for Removal [n (%)] Fertility Planning 7 (50.0%) 5 (38.5%) 3 (33.3%) Psychological Factors 4 (28.6%) 3 (23.1%) 3 (33.3%) Sacroiliac Joint Pain 3 (21.4%) 4 (30.8%) 3 (33.3%) Lower Limb Neurological Sx. 0 (0.0%) 1 (7.7%) 0 (0.0%) Table 2 Comparison of Surgical Outcomes Outcome Measure Modified Group (n = 14) Traditional Group (n = 13) Robot-assisted Group (n = 9) Overall P Value Pairwise Comparison P Value (LSD test) Operative time (min) 18.6 ± 12.9 25.8 ± 8.8 31.1 ± 8.9 0.023 Modified vs. Traditional: 0.042 Modified vs. Robot: 0.011 Traditional vs. Robot: 0.185 Intraoperative fluoroscopy (times) 5.9 ± 2.5 13.2 ± 5.4 5.0 ± 2.9 < 0.001 Modified vs. Traditional: <0.001 Modified vs. Robot: 0.463 Traditional vs. Robot: <0.001 Total hospital cost (CNY) 5281.75 ± 473.92 5614.07 ± 643.73 11480.94 ± 472.63 < 0.001 Modified vs. Traditional: 0.782 Modified vs. Robot: <0.001 Traditional vs. Robot: <0.001 Preop VAS score† 6.5 ± 1.3 N/A — VAS score at 6 months postop† 2.4 ± 1.1 N/A — Overall pain relief rate [n/N (%)]† 8/10 (80.0) N/A — Discussion Sacroiliac screws are one of the most common treatments for unstable posterior pelvic ring injuries, but the literature remains divided on the necessity of their removal [ 7 ] . Studies indicate that pregnancy primarily involves widening of the pubic symphysis, but research also shows significant increases in sacroiliac joint width from late pregnancy to postpartum [ 1 , 2 ] . In this study, 15 patients underwent removal for fertility planning. We believe that for young women with childbearing plans, removal before pregnancy is often recommended to avoid potential impact from the hardware. Despite the maturity of percutaneous sacroiliac screw fixation, due to factors like sacral dysplasia, the safe bony corridor is narrow. Malposition rates range from 2% to 18%, with risks of nerve, vascular, or visceral injury up to 3.0%-7.9% [ 13 – 15 ] . Some patients develop long-term lower limb neurological symptoms from screw malposition. In this study, one patient developed ankle plantar flexion weakness and sole numbness postoperatively. CT revealed partial screw intrusion into the sacral foramen, prompting timely screw removal and subsequent open reduction and plate fixation. The patient's neurological symptoms gradually resolved. Studies also indicate that even with well-positioned screws, loosening rates can reach 10%-18% [ 2 ] , and over one-tenth of patients may still experience sacroiliac joint pain six months postoperatively, affecting quality of life [ 16 ] . A prevailing theory suggests pain may be related to the rigid fixation of the sacroiliac joint by the screw, persisting after primary injury healing [ 8 ] . Additionally, as a slightly mobile joint absorbing load from the spine to the pelvic ring, the sacroiliac joint retains physiological function, leading some authors to oppose permanent fixation. Reza et al. studied 25 patients who underwent screw removal for pain and found 22 (88%) were satisfied and would repeat the procedure [ 17 ] . In our study, 10 patients requested removal for posterior pelvic pain, with 8 reporting significant improvement afterward. Furthermore, for the 10 patients in this study requesting removal due to psychological aversion to retained hardware, we believe removal is necessary and beneficial. The deep location and surrounding soft tissue envelope of sacroiliac screws make minimally invasive removal difficult. The traditional method relies on repeated intraoperative multi-angle fluoroscopy (inlet, outlet, lateral) to "blindly probe" the screw trajectory. This not only prolongs operative time and increases radiation exposure for patients and staff but also expands trauma and surgical risk through repeated soft tissue probing. In this study, the Traditional Group's operative time and fluoroscopy frequency were significantly higher than the other groups, primarily due to trajectory uncertainty requiring repeated fluoroscopy for guidewire placement. With the advancement of precision medicine and enhanced recovery concepts, orthopedic robotic navigation systems have been widely applied, achieving excellent results in minimally invasive pelvic fracture treatment [ 18 , 19 ] . Long Tao et al. safely removed multiple sacroiliac screws using the TiRobot, greatly reducing intraoperative fluoroscopy [ 20 ] . In our study, 9 patients underwent robot-assisted removal. By uploading acquired pelvic images to the main computer and planning the existing screw trajectory, the robotic arm was positioned, and screws were removed successfully. Fluoroscopy counts were significantly lower than the Traditional Group (5.0 ± 2.9 vs. 13.2 ± 5.4, p < 0.05). However, our results show the Robot-assisted Group's operative time was even longer than the Traditional Group (31.1 ± 8.9 vs. 25.8 ± 8.8, p = 0.185). While not statistically significant, we attribute this to the additional time required for robot setup and potential need for re-imaging due to relative movement of references, prolonging surgery and potentially adding fluoroscopy. Robot use also requires an additional incision for tracker placement, increasing trauma, and incurs high costs, as evidenced by significantly higher hospitalization expenses compared to the other groups, limiting widespread adoption. Michael et al. proposed using endoscopic techniques to identify the screw tail, insert a guidewire, and remove the screw and washer. While reducing fluoroscopy, this method still increases cost, does not shorten operative time, and has a steep learning curve, hence it was not adopted in this study [ 11 ] . We posit the main challenge in sacroiliac screw removal is intraoperative uncertainty of the screw's spatial trajectory. Therefore, we proposed using routine preoperative AP and lateral pelvic radiographs combined with the arcsine function formula to precisely calculate the coronal (θ) and transverse (α) angles of the screw trajectory. Intraoperatively, after locating the screw tail via lateral fluoroscopy, the guidewire can be inserted smoothly following these angles. This method is simple and easy to learn. Our results validate its superiority: the Modified Group's mean operative time (18.6 min) was significantly lower than both other groups. Furthermore, its mean fluoroscopy count was comparable to the Robot-assisted Group and significantly lower than the Traditional Group. This indicates the method helps achieve faster, more accurate, lower-radiation screw removal without reliance on expensive equipment. However, this study has limitations: First, it is a retrospective study with a relatively small sample size. Removal difficulty may vary with different screw orientations, warranting further sample expansion. Second, while the coronal plane angle can be preoperatively marked, the transverse plane angle is difficult to mark precisely. Intraoperatively, the transverse angle adjustment is approximate based on the fixed coronal angle, limiting absolute precision. Third, the grouping was based on the chronological order of technique adoption at our institution rather than random allocation. This sequential design (traditional method first, followed by robot-assisted, and then the modified method) inherently introduces a potential temporal bias. Conclusion In summary, we believe sacroiliac screw removal is safe and effective for patients with clear indications, improving pain symptoms in some and meeting their psychological and physiological needs. The proposed "Preoperative Trajectory Planning Method" simplifies the complex spatial localization problem into a preoperatively calculable angular problem. With a short learning curve, it significantly reduces operative time and drastically lowers intraoperative radiation exposure while ensuring removal success and clinical outcomes. Our results demonstrate the preliminary superiority of the method, but future larger-scale prospective studies are needed to promote its broader clinical application. Abbreviations AP: Anteroposterior (radiograph) ASIS: Anterior superior iliac spine CNY: Chinese Yuan CT: Computed tomography K-wire: Kirschner wire LSD: Least significant difference Postop: Postoperative Preop: Preoperative VAS: Visual Analog Scale Declarations Ethics approval and consent to participate This study was performed according to the Helsinki declaration and the study was approved by the ethics committee of Bengal Medical College (Number: BYYFY-2022KY027), and informed consent was obtained from all subjects and from their legal guardian(s) as participants below age 16 are involved in the study. Consent for publication Written informed consent for publication of their clinical details andclinical images was obtained from the patient. A copy of the consent form is available for review by the Editor of this journal. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding This work was supported by the Anhui Provincial Department of Education (Grant No. AHWJ2023A10086) and Anhui Provincial Medical Association Appropriate Technology Promotion Project (Grant No. 2025yxhsy js10) Authors' contributions Min Wu and Renjie Li designed the study. Peishuai Zhao, Yongsheng Wang, Xiaopan Wang and Xiaotian Chen collected and analyzed the patient data. Min Wu and Jianzhong Guan performed the operation. Min Wu, Renjie Li and Jiaqiang Chen analyzed the results and prepared the manuscript. All authors read and approved the final manuscript. Acknowledgements Not applicable. Statements All methods were performed in accordance with the relevant guidelines and regulations. Clinical trial number Not applicable. Author information Renjie Li and Jiaqiang Chen contributed equally to this work and share first authorship. Affiliations Department of Orthopaedics, The First Affiliated Hospital of Bengbu Medical College, Bengbu, China. Corresponding Author Correspondence to Min Wu References Jonas H, Holtenius P, Peyman S, et al. The pelvic fracture—Indicator of injury severity or lethal fracture? [J]. Injury, 2018 Aug;49(8):1568-1571. Eckardt H, Egger A, Hasler RM, et al. Good functional outcome in patients suffering fragility fractures of the pelvis treated with percutaneous screw stabilisation: Assessment of complications and factors influencing failure [J]. Injury-International Journal of the Care of the Injured, 2017 Dec;48(12):2717-2723. Lee CH, Hsu CC, Huang PY. Biomechanical study of different fixation techniques for the treatment of sacroiliac joint injuries using finite element analyses and biomechanical tests [J]. Computers in Biology & Medicine, 2017 Aug 1;87:250-257. Haveman R, van de Wall BJ, Haefeli P, et al. 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TiRobot-assisted versus conventional fluoroscopy-assisted percutaneous sacroiliac screw fixation for pelvic ring injuries: a meta-analysis [J]. Journal of Orthopaedic Surgery and Research, 2022 Dec 5;17(1):525. Long T, Chen G, Mu JS, et al. TiRobot orthopedic surgical robot-assisted sacroiliac screw removal failure: a case report [J]. Chinese Journal of Bone and Joint Injury, 2023, 38(1):99-101. 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. 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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-9047124","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":610746311,"identity":"82cc9605-4451-4c81-9556-bf79d8a4b234","order_by":0,"name":"Renjie Li","email":"","orcid":"","institution":"The First Affiliated Hospital of Bengbu Medical College","correspondingAuthor":false,"prefix":"","firstName":"Renjie","middleName":"","lastName":"Li","suffix":""},{"id":610746314,"identity":"9dbf8b78-371e-4476-a483-8f6b874c584e","order_by":1,"name":"Jiaqiang Chen","email":"","orcid":"","institution":"The First Affiliated Hospital of Bengbu Medical College","correspondingAuthor":false,"prefix":"","firstName":"Jiaqiang","middleName":"","lastName":"Chen","suffix":""},{"id":610746316,"identity":"0962047f-d7ec-449c-a796-46f9e9589603","order_by":2,"name":"Yongsheng Wang","email":"","orcid":"","institution":"The First Affiliated Hospital of Bengbu Medical College","correspondingAuthor":false,"prefix":"","firstName":"Yongsheng","middleName":"","lastName":"Wang","suffix":""},{"id":610746317,"identity":"21e4ffd7-c872-48d8-9a13-8938ae9d5fd5","order_by":3,"name":"Peishuai Zhao","email":"","orcid":"","institution":"The First Affiliated Hospital of Bengbu Medical College","correspondingAuthor":false,"prefix":"","firstName":"Peishuai","middleName":"","lastName":"Zhao","suffix":""},{"id":610746318,"identity":"e16863c8-f6fb-43cd-b711-297dd0cc0e17","order_by":4,"name":"Jianzhong Guan","email":"","orcid":"","institution":"The First Affiliated Hospital of Bengbu Medical College","correspondingAuthor":false,"prefix":"","firstName":"Jianzhong","middleName":"","lastName":"Guan","suffix":""},{"id":610746319,"identity":"48b230e4-33b9-455f-9b92-44c4c1b9713a","order_by":5,"name":"Xiaopan Wang","email":"","orcid":"","institution":"The First Affiliated Hospital of Bengbu Medical College","correspondingAuthor":false,"prefix":"","firstName":"Xiaopan","middleName":"","lastName":"Wang","suffix":""},{"id":610746320,"identity":"2439710f-c9d7-4162-9566-8d7aaf6172db","order_by":6,"name":"Xiaotian Chen","email":"","orcid":"","institution":"The First Affiliated Hospital of Bengbu Medical College","correspondingAuthor":false,"prefix":"","firstName":"Xiaotian","middleName":"","lastName":"Chen","suffix":""},{"id":610746321,"identity":"3e14366a-d9c4-4f73-97b8-4fe6980ad59b","order_by":7,"name":"Min Wu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyElEQVRIiWNgGAWjYJCCAwwGNvVtzIyNDxIqaojVUpDG2M/OfNjgwZljxNrz4TDjzH62NMmHLcyEFRvcyE48XGBwmNngMI9ZRWIDGwN/e3cCAS25Gw7PMEhnA2m5kbhDhkHizNkNeLWYgbTwGFjzQLScYWMwkMglSguzBEhLQWIbM9FanA0km9nSGIjSYn/mLUhLWgI/M/NhiYQzx3gI+kWyPXfzZ54/Ngls/AcbP/6oqJHjb+/FrwUD8JCmfBSMglEwCkYBVgAAnkZLog6ny+sAAAAASUVORK5CYII=","orcid":"","institution":"The First Affiliated Hospital of Bengbu Medical College","correspondingAuthor":true,"prefix":"","firstName":"Min","middleName":"","lastName":"Wu","suffix":""}],"badges":[],"createdAt":"2026-03-06 07:08:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9047124/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9047124/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105352130,"identity":"eef3fecf-44dc-4b9f-a599-7bcb7b759c57","added_by":"auto","created_at":"2026-03-25 06:04:14","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":353414,"visible":true,"origin":"","legend":"\u003cp\u003ea. On the preoperative anteroposterior pelvic radiograph, angle θ is formed between the extended line of the screw trajectory and the line connecting both anterior superior iliac spines (ASIS). b. On the preoperative lateral pelvic radiograph, distance H is measured between the screw head and tail. c. The transverse angle α is calculated using the formula α = arcsin(H/L). d. A trigonometric calculator is used to obtain the value of angle α.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9047124/v1/dbd4c2384214977c8da47155.png"},{"id":105565424,"identity":"144f5dc6-8d43-4941-b110-472fa5efd49a","added_by":"auto","created_at":"2026-03-27 12:53:13","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":242290,"visible":true,"origin":"","legend":"\u003cp\u003eIntraoperatively, the robotic system acquires images of the pelvic inlet, lateral, and outlet views. The trajectory is then planned according to the path of the existing sacroiliac screw.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9047124/v1/b29fabaef77d8b2a6c5e42c7.png"},{"id":106414394,"identity":"1b19a7d3-3b1e-49d7-8a72-50c2796a8479","added_by":"auto","created_at":"2026-04-08 10:07:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1543743,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9047124/v1/f4c88803-47cc-40eb-a8fe-6628dde6491d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Preoperative Trajectory Planning for Minimally Invasive Removal of Sacroiliac Screws: A Retrospective Cohort Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePelvic fractures occur in 8%-16% of trauma patients, with their incidence increasing annually alongside the rapid development of transportation and construction industries\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. Surgical treatment has become the consensus for unstable posterior pelvic ring injuries. Percutaneous sacroiliac screw fixation is currently one of the most commonly used techniques for managing posterior pelvic ring injuries, favored by many clinicians due to its minimally invasive nature, biomechanical stability, short operative time, and low infection risk\u003csup\u003e[\u003cspan additionalcitationids=\"CR4 CR5\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHowever, controversy persists regarding the necessity of removing sacroiliac screws after fracture healing\u003csup\u003e[\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. Due to the deep location of the screws and substantial overlying soft tissue coverage, minimally invasive removal is challenging. Intraoperative repeated fluoroscopy is often required, and removal time can even exceed the initial implantation time, causing significant trauma to the patient\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. With the application of robotic navigation technology, we have also employed robot-assisted removal in clinical practice, but this imposes high costs on patients.\u003c/p\u003e \u003cp\u003eWe believe the primary difficulty in sacroiliac screw removal lies in the intraoperative uncertainty of the screw's spatial trajectory. Therefore, we proposed a novel hypothesis: by utilizing the patient's preoperative imaging combined with an arcsine function formula, the inclination angles of the sacroiliac screw in the transverse and coronal planes can be measured. Subsequently, combined with intraoperative lateral fluoroscopy to locate the screw tail, this would allow for faster and more accurate screw removal. We compared this \"Preoperative Trajectory Planning Method\" with traditional and robot-assisted methods to validate its feasibility and advantages.\u003c/p\u003e"},{"header":"Patients and Methods","content":"\u003cp\u003eThis is a retrospective cohort study. The study protocol adhered to the principles of the Declaration of Helsinki and was approved by our hospital's ethics committee (Number: BYYFY-2022KY027). Informed consent for the surgical procedure was obtained from all patients or their families prior to surgery.\u003c/p\u003e \u003cp\u003eA total of 36 patients meeting the criteria who underwent sacroiliac screw removal at our hospital between January 2018 and December 2024 were ultimately included. All surgeries were performed by the same experienced trauma surgeon specializing in pelvic fractures to control for operator variability.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eInclusion criteria\u003c/strong\u003e \u003cp\u003e(1) Underwent sacroiliac screw removal at our hospital; (2) No breakage of the sacroiliac screw.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eExclusion criteria\u003c/strong\u003e \u003cp\u003e(1) Comorbid severe cardiac, pulmonary, hepatic, or renal insufficiency precluding tolerance for surgery; (2) History of sacroiliac joint infection or tumor; (3) Follow-up time less than 6 months.\u003c/p\u003e \u003c/p\u003e \u003cp\u003eThe choice of surgical technique was based on institutional trends over different periods: Before November 2021: The team had not introduced robotic navigation, thus the traditional method was used. From November 2021 (when our hospital introduced the TiRobot) to October 2022, we used robot-assisted removal. After October 2022, the team proposed the \"Preoperative Trajectory Planning Method,\" and this technique has been used since.\u003c/p\u003e \u003cp\u003eBased on the actual intraoperative method, the 36 patients were divided into three groups: the \"Modified Group\" using the Preoperative Trajectory Planning Method, the \"Traditional Group\" using the conventional method, and the \"Robot-assisted Group\" using robot assistance.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSurgical Technique\u003c/h2\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003eModified Group:\u003c/h2\u003e \u003cp\u003eThrough preoperative AP and lateral pelvic radiographs, we obtain the screw's inclination angle in the coronal plane (coronal angle, θ) and the inclination angle in the transverse plane (transverse angle, α): From the AP view, we measure the angle formed by the extended line of the screw trajectory and the line connecting both anterior superior iliac spines (ASIS), which is θ. From the lateral view, we obtain the distance (H) between the screw head and tail in the sagittal plane. Combined with the screw length (L) and the arcsine function formula α\u0026thinsp;=\u0026thinsp;arcsin (opposite/hypotenuse), where the opposite side is H and the hypotenuse is L, we calculate the transverse angle α\u0026thinsp;=\u0026thinsp;arcsin(H/L) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAfter satisfactory anesthesia, the patient is placed supine on a radiolucent carbon fiber operating table. The coronal plane angle θ is marked on the skin surface. The original incision is opened, and a 2.5mm Kirschner wire (K-wire) is inserted. Under lateral pelvic fluoroscopy, the tip of the K-wire is placed at the screw tail. While adjusting the K-wire along the marked coronal angle θ, the insertion direction is fine-tuned by referencing the calculated transverse angle α. This allows the K-wire to be smoothly inserted into the cannulated screw. After dilating the pathway with forceps, the screwdriver is used to remove the sacroiliac screw.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e\n\u003ch3\u003eTraditional Group:\u003c/h3\u003e\n\u003cp\u003eAfter satisfactory anesthesia, the patient is placed supine on a radiolucent carbon fiber operating table. The original incision is opened, and a 2.5mm K-wire is inserted. The K-wire trajectory is continuously adjusted using intraoperative fluoroscopy of the pelvic inlet and outlet views, and lateral fluoroscopy is used to locate the screw tail. Once positioned, a guidewire is inserted. After dilating the pathway with forceps, the screwdriver is used to remove the sacroiliac screw.\u003c/p\u003e\n\u003ch3\u003eRobot-assisted Group:\u003c/h3\u003e\n\u003cp\u003eAfter satisfactory anesthesia, the patient is placed supine on a radiolucent carbon fiber operating table. A patient tracker is fixed to the contralateral ASIS. Fluoroscopic images of the pelvic inlet, lateral, and outlet views are acquired and uploaded to the main control computer. The screw trajectory is then planned according to the existing sacroiliac screw path (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). After planning, the robotic arm is maneuvered to the designated position. The original incision is opened, and the guidewire is inserted. At this point, the guidewire is successfully inserted into the cannulated sacroiliac screw. After dilating the pathway with forceps, the screwdriver is used to remove the screw.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003ePostoperative Management\u003c/h3\u003e\n\u003cp\u003ePostoperative management included analgesic and supportive care. Patients were encouraged to perform hip and knee joint functional exercises during bed rest. Ambulation was initiated within one week postoperatively based on recovery progress.\u003c/p\u003e \u003cp\u003eAll patients completed at least 6 months of follow-up (mean follow-up: 13.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4 months). Follow-up data for all enrolled patients was complete, with no lost cases.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eOutcome Measures\u003c/h2\u003e \u003cp\u003e \u003cstrong\u003ePrimary outcome measures\u003c/strong\u003e \u003cp\u003eMean operative time per sacroiliac screw removed and mean number of intraoperative fluoroscopies per screw.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eSecondary outcome measures\u003c/strong\u003e \u003cp\u003ePatient baseline data (age, gender), number of screws removed, main reason for removal request, total hospitalization cost, and pain relief at the sacroiliac joint region at 6 months postoperatively [For all patients who underwent removal due to pain, Visual Analog Scale (VAS) scores preoperatively and at 6 months postoperatively were compared. The overall pain relief rate (percentage of patients with a VAS reduction\u0026thinsp;\u0026ge;\u0026thinsp;2 points) was calculated].\u003c/p\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed using SPSS 22.0 (SPSS, Chicago, IL). Continuous variables, after confirmation of normal distribution by Shapiro-Wilk test and homogeneity of variance by Levene's test, are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (x̄ \u0026plusmn; s). Comparisons among the three groups were performed using one-way ANOVA, and if a significant difference was found, post-hoc pairwise comparisons were conducted using the Least Significant Difference (LSD) method. Categorical variables are presented as frequency and percentage [n (%)], with comparisons among groups performed using the chi-square test or Fisher's exact test. A P-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 36 patients were included in the final analysis: 14 in the Modified Group, 13 in the Traditional Group, and 9 in the Robot-assisted Group. All sacroiliac screws were successfully removed without residual hardware. There were no statistically significant differences among the three groups in terms of age, gender distribution, total number of screws removed, or the main reason for removal request (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), indicating balanced baseline characteristics and comparability (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAmong the 36 patients, 15 requested removal due to fertility planning; 10 due to psychological factors (inability to accept retained hardware); 10 due to significant sacroiliac joint pain/discomfort; and 1 due to postoperative lower limb neurological symptoms (which gradually resolved after timely screw removal).\u003c/p\u003e \u003cp\u003eRegarding primary outcomes, the mean operative time per screw in the Modified Group was 18.6\u0026thinsp;\u0026plusmn;\u0026thinsp;12.9 min, significantly shorter than both the Traditional Group (25.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.8 min) and the Robot-assisted Group (31.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8.9 min) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). No significant difference was found between the Traditional and Robot-assisted Groups. The mean number of intraoperative fluoroscopies per screw in the Modified Group was 5.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5, showing no significant difference from the Robot-assisted Group (5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9) (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), but both were significantly lower than the Traditional Group (13.2\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e \u003cp\u003eRegarding cost, the mean total hospitalization cost in the Modified Group was 5281.75\u0026thinsp;\u0026plusmn;\u0026thinsp;473.92 CNY, and 5614.07\u0026thinsp;\u0026plusmn;\u0026thinsp;643.73 CNY in the Traditional Group, with no significant difference between these two groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The mean total hospitalization cost in the Robot-assisted Group was significantly higher at 11480.94\u0026thinsp;\u0026plusmn;\u0026thinsp;472.63 CNY, significantly exceeding both the Modified and Traditional Groups (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e \u003cp\u003eA summary analysis of the 10 patients who underwent removal due to pain showed the mean VAS score significantly decreased from 6.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3 preoperatively to 2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1 at 6 months postoperatively (mean ΔVAS: 4.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The overall pain relief rate was 80% (8/10) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBaseline Patient Characteristics and Reasons for Removal\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCharacteristic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eModified Group (n\u0026thinsp;=\u0026thinsp;14)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTraditional Group (n\u0026thinsp;=\u0026thinsp;13)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRobot-assisted Group (n\u0026thinsp;=\u0026thinsp;9)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge (years, x̄ \u0026plusmn; s)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.7\u0026thinsp;\u0026plusmn;\u0026thinsp;18.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.2\u0026thinsp;\u0026plusmn;\u0026thinsp;15.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e33.0\u0026thinsp;\u0026plusmn;\u0026thinsp;14.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.905\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eGender [n (%)]\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.838\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (21.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (23.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (22.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (78.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (76.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7 (77.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMain Reason for Removal [n (%)]\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFertility Planning\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7 (50.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (38.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3 (33.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePsychological Factors\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (28.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (23.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3 (33.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSacroiliac Joint Pain\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (21.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 (30.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3 (33.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLower Limb Neurological Sx.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (7.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0 (0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of Surgical Outcomes\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOutcome Measure\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eModified Group (n\u0026thinsp;=\u0026thinsp;14)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTraditional Group (n\u0026thinsp;=\u0026thinsp;13)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRobot-assisted Group (n\u0026thinsp;=\u0026thinsp;9)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOverall P Value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePairwise Comparison P Value (LSD test)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOperative time (min)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18.6\u0026thinsp;\u0026plusmn;\u0026thinsp;12.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eModified vs. Traditional: 0.042\u003c/p\u003e \u003cp\u003eModified vs. Robot: 0.011\u003c/p\u003e \u003cp\u003eTraditional vs. Robot: 0.185\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIntraoperative fluoroscopy (times)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.2\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eModified vs. Traditional: \u0026lt;0.001\u003c/p\u003e \u003cp\u003eModified vs. Robot: 0.463\u003c/p\u003e \u003cp\u003eTraditional vs. Robot: \u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal hospital cost (CNY)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5281.75\u0026thinsp;\u0026plusmn;\u0026thinsp;473.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5614.07\u0026thinsp;\u0026plusmn;\u0026thinsp;643.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11480.94\u0026thinsp;\u0026plusmn;\u0026thinsp;472.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eModified vs. Traditional: 0.782\u003c/p\u003e \u003cp\u003eModified vs. Robot: \u0026lt;0.001\u003c/p\u003e \u003cp\u003eTraditional vs. Robot: \u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePreop VAS score\u0026dagger;\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003e6.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eN/A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVAS score at 6 months postop\u0026dagger;\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003e2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eN/A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOverall pain relief rate [n/N (%)]\u0026dagger;\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003e8/10 (80.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eN/A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eSacroiliac screws are one of the most common treatments for unstable posterior pelvic ring injuries, but the literature remains divided on the necessity of their removal\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eStudies indicate that pregnancy primarily involves widening of the pubic symphysis, but research also shows significant increases in sacroiliac joint width from late pregnancy to postpartum\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. In this study, 15 patients underwent removal for fertility planning. We believe that for young women with childbearing plans, removal before pregnancy is often recommended to avoid potential impact from the hardware.\u003c/p\u003e \u003cp\u003eDespite the maturity of percutaneous sacroiliac screw fixation, due to factors like sacral dysplasia, the safe bony corridor is narrow. Malposition rates range from 2% to 18%, with risks of nerve, vascular, or visceral injury up to 3.0%-7.9%\u003csup\u003e[\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. Some patients develop long-term lower limb neurological symptoms from screw malposition. In this study, one patient developed ankle plantar flexion weakness and sole numbness postoperatively. CT revealed partial screw intrusion into the sacral foramen, prompting timely screw removal and subsequent open reduction and plate fixation. The patient's neurological symptoms gradually resolved.\u003c/p\u003e \u003cp\u003eStudies also indicate that even with well-positioned screws, loosening rates can reach 10%-18%\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e, and over one-tenth of patients may still experience sacroiliac joint pain six months postoperatively, affecting quality of life\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. A prevailing theory suggests pain may be related to the rigid fixation of the sacroiliac joint by the screw, persisting after primary injury healing\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Additionally, as a slightly mobile joint absorbing load from the spine to the pelvic ring, the sacroiliac joint retains physiological function, leading some authors to oppose permanent fixation. Reza et al. studied 25 patients who underwent screw removal for pain and found 22 (88%) were satisfied and would repeat the procedure\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. In our study, 10 patients requested removal for posterior pelvic pain, with 8 reporting significant improvement afterward.\u003c/p\u003e \u003cp\u003eFurthermore, for the 10 patients in this study requesting removal due to psychological aversion to retained hardware, we believe removal is necessary and beneficial.\u003c/p\u003e \u003cp\u003eThe deep location and surrounding soft tissue envelope of sacroiliac screws make minimally invasive removal difficult. The traditional method relies on repeated intraoperative multi-angle fluoroscopy (inlet, outlet, lateral) to \"blindly probe\" the screw trajectory. This not only prolongs operative time and increases radiation exposure for patients and staff but also expands trauma and surgical risk through repeated soft tissue probing. In this study, the Traditional Group's operative time and fluoroscopy frequency were significantly higher than the other groups, primarily due to trajectory uncertainty requiring repeated fluoroscopy for guidewire placement.\u003c/p\u003e \u003cp\u003eWith the advancement of precision medicine and enhanced recovery concepts, orthopedic robotic navigation systems have been widely applied, achieving excellent results in minimally invasive pelvic fracture treatment\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. Long Tao et al. safely removed multiple sacroiliac screws using the TiRobot, greatly reducing intraoperative fluoroscopy\u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. In our study, 9 patients underwent robot-assisted removal. By uploading acquired pelvic images to the main computer and planning the existing screw trajectory, the robotic arm was positioned, and screws were removed successfully. Fluoroscopy counts were significantly lower than the Traditional Group (5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9 vs. 13.2\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). However, our results show the Robot-assisted Group's operative time was even longer than the Traditional Group (31.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8.9 vs. 25.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.8, p\u0026thinsp;=\u0026thinsp;0.185). While not statistically significant, we attribute this to the additional time required for robot setup and potential need for re-imaging due to relative movement of references, prolonging surgery and potentially adding fluoroscopy. Robot use also requires an additional incision for tracker placement, increasing trauma, and incurs high costs, as evidenced by significantly higher hospitalization expenses compared to the other groups, limiting widespread adoption. Michael et al. proposed using endoscopic techniques to identify the screw tail, insert a guidewire, and remove the screw and washer. While reducing fluoroscopy, this method still increases cost, does not shorten operative time, and has a steep learning curve, hence it was not adopted in this study\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eWe posit the main challenge in sacroiliac screw removal is intraoperative uncertainty of the screw's spatial trajectory. Therefore, we proposed using routine preoperative AP and lateral pelvic radiographs combined with the arcsine function formula to precisely calculate the coronal (θ) and transverse (α) angles of the screw trajectory. Intraoperatively, after locating the screw tail via lateral fluoroscopy, the guidewire can be inserted smoothly following these angles. This method is simple and easy to learn. Our results validate its superiority: the Modified Group's mean operative time (18.6 min) was significantly lower than both other groups. Furthermore, its mean fluoroscopy count was comparable to the Robot-assisted Group and significantly lower than the Traditional Group. This indicates the method helps achieve faster, more accurate, lower-radiation screw removal without reliance on expensive equipment.\u003c/p\u003e \u003cp\u003eHowever, this study has limitations: First, it is a retrospective study with a relatively small sample size. Removal difficulty may vary with different screw orientations, warranting further sample expansion. Second, while the coronal plane angle can be preoperatively marked, the transverse plane angle is difficult to mark precisely. Intraoperatively, the transverse angle adjustment is approximate based on the fixed coronal angle, limiting absolute precision. Third, the grouping was based on the chronological order of technique adoption at our institution rather than random allocation. This sequential design (traditional method first, followed by robot-assisted, and then the modified method) inherently introduces a potential temporal bias.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, we believe sacroiliac screw removal is safe and effective for patients with clear indications, improving pain symptoms in some and meeting their psychological and physiological needs. The proposed \"Preoperative Trajectory Planning Method\" simplifies the complex spatial localization problem into a preoperatively calculable angular problem. With a short learning curve, it significantly reduces operative time and drastically lowers intraoperative radiation exposure while ensuring removal success and clinical outcomes. Our results demonstrate the preliminary superiority of the method, but future larger-scale prospective studies are needed to promote its broader clinical application.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003eAP: Anteroposterior (radiograph)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eASIS: Anterior superior iliac spine\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCNY: Chinese Yuan\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCT: Computed tomography\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eK-wire: Kirschner wire\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLSD: Least significant difference\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePostop: Postoperative\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePreop: Preoperative\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eVAS: Visual Analog Scale\u003c/strong\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003eThis study was performed according to the Helsinki declaration and the study was approved by the ethics committee of Bengal Medical College (Number: BYYFY-2022KY027), and informed consent was obtained from all subjects and from their legal guardian(s) as participants below age 16 are involved in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e Written informed consent for publication of their clinical details andclinical images was obtained from the patient. A copy of the consent form is available for review by the Editor of this journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e This work was supported by the Anhui Provincial Department of Education (Grant No. AHWJ2023A10086) and Anhui Provincial Medical Association Appropriate Technology Promotion Project (Grant No. 2025yxhsy js10)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e Min Wu and Renjie Li designed the study. Peishuai Zhao, Yongsheng Wang, Xiaopan Wang and Xiaotian Chen collected and analyzed the patient data. Min Wu and Jianzhong Guan performed the operation. Min Wu, Renjie Li and Jiaqiang Chen analyzed the results and prepared the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatements\u0026nbsp;\u003c/strong\u003eAll methods were performed in accordance with the relevant guidelines and regulations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRenjie Li\u0026nbsp;and Jiaqiang Chen contributed equally to this work and share first authorship.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAffiliations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDepartment of Orthopaedics, The First Affiliated Hospital of Bengbu Medical College, Bengbu, China.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorresponding Author\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCorrespondence to Min Wu\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eJonas H, Holtenius P, Peyman S, et al. The pelvic fracture\u0026mdash;Indicator of injury severity or lethal fracture? [J]. Injury, 2018 Aug;49(8):1568-1571.\u003c/li\u003e\n\u003cli\u003eEckardt H, Egger A, Hasler RM, et al. Good functional outcome in patients suffering fragility fractures of the pelvis treated with percutaneous screw stabilisation: Assessment of complications and factors influencing failure [J]. Injury-International Journal of the Care of the Injured, 2017 Dec;48(12):2717-2723.\u003c/li\u003e\n\u003cli\u003eLee CH, Hsu CC, Huang PY. Biomechanical study of different fixation techniques for the treatment of sacroiliac joint injuries using finite element analyses and biomechanical tests [J]. Computers in Biology \u0026amp; Medicine, 2017 Aug 1;87:250-257.\u003c/li\u003e\n\u003cli\u003eHaveman R, van de Wall BJ, Haefeli P, et al. Accuracy in navigated percutaneous sacroiliac screw fixation: A systematic review and meta-analysis [J]. British Journal of Surgery, 2025 Mar 5;25(1):89.\u003c/li\u003e\n\u003cli\u003eLink BC, Haveman RA, van de Wall BJM, et al. Percutaneous sacroiliac screw fixation with a 3D robot-assisted image-guided navigation system [J]. Operative Orthop\u0026auml;die und Traumatologie, 2024, 37(1):3\u0026ndash;13.\u003c/li\u003e\n\u003cli\u003eIorio JA, Jakoi AM, Rehman S. Percutaneous sacroiliac screw fixation of the posterior pelvic ring [J]. Orthopedic Clinics of North America, 2015, 46(4):511\u0026ndash;521.\u003c/li\u003e\n\u003cli\u003eStuby FM, Gonser CE, Baron HC, et al. Implantatentfernung nach Beckenringfraktur [J]. Der Unfallchirurg, 2012, 115(4):330\u0026ndash;338.\u003c/li\u003e\n\u003cli\u003eY\u0026uuml;cel N, Lefering R, Tjardes T, et al. [Is implant removal after percutaneous iliosacral screw fixation of unstable posterior pelvic ring disruptions indicated?] [J]. Der Unfallchirurg, 2004 Jun;107(6):468-474.\u003c/li\u003e\n\u003cli\u003eOsterhoff G, Noser J, Sprengel K, et al. Rate of intraoperative problems during sacroiliac screw removal: Expect the unexpected [J]. BMC Surgery, 2019 Apr 15;19(1):39.\u003c/li\u003e\n\u003cli\u003eLangfitt MK, Best BJ, Carroll EA. A useful tool for retained washer retrieval when removing iliosacral screws [J]. Journal of Surgical Orthopaedic Advances, 2013, 22(4):330\u0026ndash;332.\u003c/li\u003e\n\u003cli\u003eOberst M, Konrad G, Herget GW, et al. Novel endoscopic sacroiliac screw removal technique: reduction of intraoperative radiation exposure [J]. Archives of Orthopaedic \u0026amp; Trauma Surgery, 2014, 134(11):1557\u0026ndash;1560.\u003c/li\u003e\n\u003cli\u003eHermann KGA, Halle H, Reisshauer A, et al. [Peripartum changes of the pelvic ring: usefulness of magnetic resonance imaging] [J]. R\u0026ouml;Fo - Fortschritte auf dem Gebiet der R\u0026ouml;ntgenstrahlen und der bildgebenden Verfahren, 2007, 179(12):1243\u0026ndash;1250.\u003c/li\u003e\n\u003cli\u003eKrappinger D, Lindtner RA, Benedikt S. Preoperative planning and safe intraoperative placement of iliosacral screws under fluoroscopic control [J]. Operative Orthop\u0026auml;die und Traumatologie, 2019, 31(6):465\u0026ndash;473.\u003c/li\u003e\n\u003cli\u003eVentura E, De Vivo L, Manfredi L, et al. Chronic sacroiliac joint dysfunction and CT-guided percutaneous fixation: a 6-year experience [J]. Neuroradiology, 2023, 65(10):1527\u0026ndash;1534.\u003c/li\u003e\n\u003cli\u003eLi XS, Huang LB, Kong Y, et al. Modified percutaneous iliosacral screw and anterior internal fixator technique for treating unstable pelvic fractures: a retrospective study [J]. BMC Musculoskeletal Disorders, 2022 Dec 6;23(1):1068.\u003c/li\u003e\n\u003cli\u003ePohlemann T, Angst M, et al. Fixation of transforaminal sacrum fractures [J]. Journal of Orthopaedic Trauma, 1993, 7(2):107\u0026ndash;117.\u003c/li\u003e\n\u003cli\u003eFiroozabadi R, Kovalenko B, Toogood P. Does implant removal across the sacroiliac joint improve pain and outcomes? [J]. Journal of Orthopaedic Trauma, 2020, 34(6):307\u0026ndash;309.\u003c/li\u003e\n\u003cli\u003eLi N, Zhu Z, Xiao C, et al. The efficacy of \u0026ldquo;TiRobot\u0026rdquo; orthopaedic robot-assisted versus conventional fluoroscopic percutaneous screw fixation of the sacroiliac joint [J]. International Orthopaedics, 2022, 47(2):351\u0026ndash;358.\u003c/li\u003e\n\u003cli\u003eZhao C, Zhu G, Wang Y, et al. TiRobot-assisted versus conventional fluoroscopy-assisted percutaneous sacroiliac screw fixation for pelvic ring injuries: a meta-analysis [J]. Journal of Orthopaedic Surgery and Research, 2022 Dec 5;17(1):525.\u003c/li\u003e\n\u003cli\u003eLong T, Chen G, Mu JS, et al. TiRobot orthopedic surgical robot-assisted sacroiliac screw removal failure: a case report [J]. Chinese Journal of Bone and Joint Injury, 2023, 38(1):99-101.\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":"","lastPublishedDoi":"10.21203/rs.3.rs-9047124/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9047124/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBackground: Minimally invasive removal of sacroiliac screws is often challenging due to intraoperative uncertainty regarding the screw trajectory, leading to prolonged operative time and increased radiation exposure. Although robot-assisted techniques can improve accuracy, they are associated with high costs. This study aimed to evaluate the feasibility of a \"preoperative trajectory planning method\" based on preoperative imaging and trigonometric calculation for the removal of sacroiliac screws.\u003c/p\u003e\n\u003cp\u003eMethods:\u0026nbsp;We conducted a retrospective cohort study of 36 patients who underwent sacroiliac screw removal between January 2018 and December 2024. The patients were divided into three groups: a modified group (n=14, using the new method), a traditional group (n=13, relying on intraoperative fluoroscopy for freehand exploration), and a robot-assisted group (n=9, using the TiRobot orthopedic robot). The reasons for screw removal were analyzed, and the operative time, number of intraoperative fluoroscopies, and hospitalization costs were compared among the three groups.\u003c/p\u003e\n\u003cp\u003eResults:\u0026nbsp;All screws were successfully removed. The mean operative time in the modified group (18.6 ± 12.9 minutes) was significantly shorter than that in both the traditional group (25.8 ± 8.8 minutes) and the robot-assisted group (31.1 ± 8.9 minutes) (all P \u0026lt; 0.05). The mean number of fluoroscopies in the modified group (5.9 ± 2.5) showed no significant difference from the robot-assisted group (5.0 ± 2.9), but both were significantly lower than the traditional group (13.2 ± 5.4, P \u0026lt; 0.01). The hospitalization cost in the robot-assisted group (11480.94 ± 472.63 CNY) was significantly higher than that in both the modified and traditional groups (P \u0026lt; 0.01).\u003c/p\u003e\n\u003cp\u003eConclusion: The \"preoperative trajectory planning method\" enables precise and efficient removal of sacroiliac screws without reliance on expensive robotic equipment. This method features a short learning curve, reduces operative time and intraoperative radiation exposure, and does not impose an additional financial burden on patients, demonstrating good potential for broad clinical application.\u003c/p\u003e","manuscriptTitle":"Preoperative Trajectory Planning for Minimally Invasive Removal of Sacroiliac Screws: A Retrospective Cohort Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-25 06:04:10","doi":"10.21203/rs.3.rs-9047124/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","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}}],"origin":"","ownerIdentity":"97fbd326-1209-4dbc-81f0-62d06749d819","owner":[],"postedDate":"March 25th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-08T10:05:10+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-25 06:04:10","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9047124","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9047124","identity":"rs-9047124","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}