Obturator Internus Muscle Entrapment in Posterior Wall Acetabular Fractures: A Rare Intraoperative Finding

Obturator Internus Muscle Entrapment in Posterior Wall Acetabular Fractures: A Rare Intraoperative Finding | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Obturator Internus Muscle Entrapment in Posterior Wall Acetabular Fractures: A Rare Intraoperative Finding Babu Mohammed Rafi Vaderi, Vijay Sharma, Siva Srivastava Garika, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5338947/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 Introduction: We report two cases of the rare presentation of obturator internus muscle entrapment in posterior wall fractures of the acetabulum. While piriformis muscle entrapment has been previously reported, there are no known cases of obturator internus entrapment associated with posterior wall fractures of the acetabulum. Case Presentation: Case 1: A 38-year-old male presented with right hip and knee pain following a road traffic accident. He was diagnosed with a posterior wall and posterior column fracture, accompanied by posterior dislocation of the knee. During surgery, the obturator internus muscle was found interposed between the fracture site and the displaced posterior wall fragment. Case 2: A 43-year-old male sustained blunt abdominal trauma and a Pipkin type 4 (femoral head fracture with posterior wall fracture) injury following a road traffic accident. After stabilization of his abdominal injury with laparoscopic mesenteric repair, the patient underwent open reduction and internal fixation of the posterior wall fracture, along with removal of intra-articular bony fragments from an infra-foveal femoral head fracture. Similarly, during the procedure, the obturator internus muscle was found interposed between the fracture site and the displaced posterior wall fragment. Both patients followed a standard post-operative rehabilitation protocol and recovery was uneventful. Conclusion: These cases highlight the importance of recognizing muscle entrapment as a potential cause of difficulty in reducing posterior acetabular wall fractures. Proper identification and management of such interpositions are crucial to ensure successful fracture reduction and fixation. Acetabulum Fractures Posterior wall Obturator internus Entrapment Kocher-Langenbeck Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Acetabular fractures present a significant challenge to orthopaedic surgeons due to the complex osseous and surgical anatomy( 1 ). Posterior wall fractures are the most common type of acetabular fractures, accounting for one-fourth to one-third of all acetabular fractures. Displaced posterior wall fractures are managed with anatomical reduction of the articular surface and rigid internal fixation followed by early mobilisation( 2 – 7 ). The Kocher-Langenbeck approach is commonly used for posterior wall fractures, providing direct access to the posterior wall and posterior column, and indirect access to the superior wall and quadrilateral surface. Proper visualization and isolation of the short external rotator muscles are crucial steps in KL approach for posterior wall fracture reduction and fixation( 8 ). This article presents two case reports of posterior wall fractures with obturator internus entrapment between the fractured fragments. Currently, no literature reports obturator internus interposition in posterior wall fractures, although piriformis muscle entrapment has been documented( 9 ). Case Report Case 1: A 38-year-old male presented to the emergency department with pain in the right hip and knee following a road traffic accident involving a collision between a four-wheeler and a truck. He was unable to bear weight on his right lower limb and presented with significant swelling and deformity of the right knee. On examination, there was tenderness around the right hip with painful movements. The patient also had a dislocated right knee, which was reduced in the emergency department under sedation, with no distal neurovascular deficits. Radiographic imaging revealed a displaced posterior acetabular wall fracture with a posterior column fracture. The displaced fracture fragment measured approximately 3.0 × 2.8 × 1.0 cm and was displaced by about 1 cm posteriorly. The patient was scheduled for surgical intervention the following day, after a pre-anesthesia checkup. The surgical procedure was performed with the patient in the left lateral decubitus position, using a standard Kocher-Langenbeck approach to access the hip. After identifying the piriformis, superior gemellus, and inferior gemellus, they were tagged and cut 1.5 cm from their attachment to the greater trochanter. However, the obturator internus was not visualized initially. Further exposure of the fracture site and freshening of the margins revealed that the obturator internus muscle was interposed between the fracture site and the displaced fragment (Fig. 2). This interposition likely accounted for the difficulty in achieving complete reduction. The obturator internus muscle was released 1.5 cm away from its insertion in a traditional way, followed by the reduction of the posterior wall fragment onto the posterior column. It was provisionally stabilised using K-wires, and final fixation was achieved using a buttress plate. The short external rotators were reattached with No. 5 Ethibond (Ethicon W4846, USA) sutures, and the hip was checked through a range of motion to confirm stability. Rehabilitation began immediately post-operatively. At the six-month follow-up, radiographs were satisfactory, and the patient could ambulate freely without pain. Figure 1 A,B,C-Radiological images showing posterior wall and posterior column fracture of the right acetabulum D-Post-operative X-ray showing reduced fracture with implant insitu Figure 2 Intra-operative image demonstrating entrapped Obturator internus muscle between fracture fragments (Green arrow represents the obturator internus muscle) Case 2: A 43-year-old male presented to the trauma and emergency department with complaints of abdominal pain and right hip pain following a road traffic accident, in which a four-wheeler was hit head-on by another four-wheeler. He was stabilised as per the ATLS protocol and was diagnosed with a mesenteric injury with serosal tears, haemoperitoneum, right posterior hip dislocation, femoral head fracture, and posterior wall acetabular fracture. He underwent reduction of the right hip dislocation and emergency laparoscopic repair for the mesenteric injury and serosal tear. Further imaging revealed an infra-foveal femoral head fracture and a posterior wall fracture (Pipkin type 4), along with intra-articular fragments in the hip joint. Following stabilisation of the abdominal injuries, he was scheduled for acetabular fracture fixation. The Kocher-Langenbeck approach was used with the patient in the left lateral decubitus position. After developing the planes, the piriformis, superior gemellus, and inferior gemellus were identified, tagged, and released. The posterior wall fracture fragment was visualized before the visualization of the obturator internus. Lateral traction with a Steinmann pin to the femoral head was used for joint distraction. When the posterior wall fragment was elevated to inspect the joint, obturator internus interposition was noted between the fracture fragments (Figure:5). The obturator internus muscle was released away from the insertion, and the infra-foveal femoral head fragment and intra-articular bone fragments were removed. A thorough joint wash was performed. Complete reduction of the posterior wall fragment was achieved, and the fragment was fixed using an interfragmentary screw and buttressed with a plate.The short external rotators were reattached with No. 5 Ethibond (Ethicon W4846, USA) sutures, and the wound was closed in layers after confirming stability. Partial weight-bearing was initiated after suture removal at two weeks, and full weight-bearing was allowed after six weeks. Regular follow-up through clinical examination and X-ray was performed. Figure 3 : CT Coronal(A) ,Axial(B),3D reconstruction (C and D) section of pelvis demonstrating infrafoveal femoral head fracture and posterior wall fracture At the one-year follow-up, the patient was walking without limping or pain. Figure 5 Intra-operative image demonstrating entrapped Obturator internus muscle between fracture fragments (yellow arrow represents the obturator internus muscle) Figure 4 (A) X-ray pelvis with both hip shows dislocated right hip dislocation,posterior wall fracture and femoral head fracture ,(B)Post-operative X-ray pelvis with both hip showing reduced fracture with implant insitu Discussion The incidence of acetabular fractures has increased in recent years due to the rise in road traffic accidents ( 10 – 12 ). The hip joint is a major weight-bearing joint, playing a crucial role in mobility and daily activities ( 13 ). With the increasing awareness of the complexity of acetabular fractures and the importance of achieving good prognoses, more of these fractures are being surgically treated ( 14 – 16 ). Important goals in managing acetabular fractures include joint preservation, congruency, and stability with minimal disturbance to the blood supply. A sound knowledge of rare intraoperative findings plays a significant role in effectively managing these fractures. The interposition of soft tissue in posterior wall fractures is a rare occurrence. Soft tissue entrapments can impede anatomical reduction, leading to incongruency of the hip joint and subsequent poor outcomes. A comprehensive literature search was conducted using three online databases: PubMed, Cochrane, and Embase, with the keywords "obturator internus interposition/entrapment," "soft tissue interposition/entrapment in acetabular fractures," and "short external rotators interposition/entrapment." This search yielded only one relevant case report by Beyer et al., who documented a case of a 12-year-old child with piriformis entrapment in a posterior wall fracture ( 9 ). Notably, our literature search did not reveal any previous studies on obturator internus interposition. To our knowledge, this case report represents the first documented instance of this specific entrapment. This case report demonstrates the rare but significant occurrence of obturator internus muscle entrapment in posterior wall acetabular fractures. It highlights the importance of recognizing that any shortened external rotators, including the obturator internus, can become entrapped and potentially prevent the anatomical reduction of the posterior wall of the acetabulum during the surgery. Vigilantly recognizing these rare possibilities is crucial for surgeons to effectively manage such complex situations. Further documentation of similar cases will help broaden the understanding of this rare presentation and guide future surgical strategies in managing complex acetabular fractures. Conclusion This case highlights the importance of recognizing potential soft tissue interpositions, such as obturator internus entrapment, in posterior acetabular wall fractures. Proper surgical planning and meticulous intraoperative management are crucial to ensure successful fracture reduction and fixation. Awareness of such unusual presentations can help optimize outcomes in complex trauma cases. Declarations Funding No funding was received to assist with the preparation of this manuscript. Ethics Approval Ethics approval was not required for this case report. Consent to Participate and Consent to Publish Written informed consent was obtained from both patients for participation and publication of this case report and any accompanying images. Authors’ Contributions The first draft of the manuscript was written by Dr. Babu Mohammed Rafi V., who also led manuscript drafting. Prof. Vijay Sharma was responsible for manuscript revision, patient management, and patient follow-up. All authors contributed to the study conception and design, reviewed, and approved the final manuscript. Acknowledgments The authors wish to thank the patients and their relatives for their support. Conflict of Interest Summary Statement The authors declare no conflicts of interest related to this work. References Kim HT, Ahn JM, Hur JO, Lee JS, Cheon SJ. Reconstruction of acetabular posterior wall fractures. Clin Orthop Surg. 2011;3(2):114–20. https://doi.org/10.4055/cios.2011.3.2.114 Firoozabadi R, Yu Chen E, Elhaddad M, Tornetta Iii P. Isolated Buttress Plating of Posterior Wall Acetabular Fractures: Is it Sufficient? Arch Bone Jt Surg. 2020;8(4):511–8.https://doi.org/10.22038%2Fabjs.2020.42128.2167 Giannoudis PV, Nikolaou VS. Surgical techniques—How do I do it?: Open reduction and internal fixation of posterior wall fractures of the acetabulum. Injury. 2008;39(10):1113–8. https://doi.org/10.1016/j.injury.2008.06.019 Letournel E. Acetabulum fractures: classification and management. Clin Orthop Relat Res. 1980;(151):81–106. Wittenberg S, Rau D, Paraskevaidis M, Jaecker V, Stöckle U, Märdian S. Treatment Trends and Epidemiologic Changes in Acetabular Fracture Management over the Course of 10 Years: An Analysis Based on 2853 Patients as Treated by the German Pelvic Multicenter Study Group. J Clin Med. 2024;13(16):4601. https://doi.org/10.3390%2Fjcm13164601 Ahmed M, Abuodeh Y, Alhammoud A, Salameh M, Hasan K, Ahmed G. Epidemiology of acetabular fractures in Qatar. Int Orthop. 2018;42(9):2211–7. https://doi.org/10.1007/s00264-018-3824-z AlRousan FM, Almigdad AK, Jwinate MN, Aolymate MA, Alsarhan FY, Al-Qudah OM. A review of acetabular fracture patterns, etiologies, and management in Jordan. Saudi Med J. 2023;44(6):607–12. https://doi.org/10.15537%2Fsmj.2023.44.6.20220931 Tosounidis TH, Giannoudis VP, Kanakaris NK, Giannoudis PV. The Kocher-Langenbeck Approach: State of the Art. JBJS Essent Surg Tech. 2018;8(2):e18. https://doi.org/10.2106/jbjs.st.16.00102 Case Report: Pediatric Posterior Wall Acetabulum with Piriformis Entrapment | Case Reports in Orthopedic Research | Karger Publishers [Internet]. [cited 2024 Sep 23]. Available from: https://karger.com/cio/article/5/1/38/827691 /Case-Report-Pediatric-Posterior-Wall-Acetabulum. https://doi.org/10.1159/000522215 Trikha V, V G, Cabrera D, Bansal H, Mittal S, Sharma V. Epidemiological assessment of acetabular fractures in a level one trauma centre: A 7-Year observational study. J Clin Orthop Trauma. 2020;11(6):1104–9. https://doi.org/10.1159/000522215 Albrektsson M, Möller M, Wolf O, Wennergren D, Sundfeldt M. Acetabular fractures: Epidemiology and mortality based on 2,132 fractures from the Swedish Fracture Register. Bone Jt Open. 2023;4(9):652–8. https://doi.org/10.1159/000522215 Park KT, Park EK, Lee DH, An JH, Won J, Kim SH, et al. The Current Incidence and Future Projection of Acetabular Fractures in Korea. Journal of Korean Medical Science [Internet]. 2024 Jun 10 [cited 2024 Sep 23];39(27). Available from: https://doi.org/10.3346/jkms.2024.39.e204 Hall M, van der Esch M, Hinman RS, Peat G, de Zwart A, Quicke JG, et al. How does hip osteoarthritis differ from knee osteoarthritis? Osteoarthritis Cartilage. 2022;30(1):32–41. https://doi.org/10.1016/j.joca.2021.09.010 Audretsch C, Trulson A, Höch A, Herath SC, Histing T, Küper MA. Evaluation of decision-making in the treatment of acetabular fractures. EFORT Open Rev. 2022;7(1):84–94. https://doi.org/10.1530/eor-20-0149 Matta JM. Fractures of the acetabulum: Accuracy of reduction and clinical results in patients managed operatively within three weeks after the injury. Journal of Bone and Joint Surgery. 1996;78(11):1632–45. Matta JM, Mehne DK, Roffi R. Fractures of the acetabulum. Early results of a prospective study. Clinical Orthopaedics and Related Research. 1986;NO. 205:241–50. 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-5338947","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":373554638,"identity":"917c1338-8de1-4529-9b5e-f6ee5770ed2c","order_by":0,"name":"Babu Mohammed Rafi Vaderi","email":"","orcid":"","institution":"All India Institute of Medical Sciences(AIIMS),New Delhi,India","correspondingAuthor":false,"prefix":"","firstName":"Babu","middleName":"Mohammed Rafi","lastName":"Vaderi","suffix":""},{"id":373554639,"identity":"d1db3595-58d3-4401-8a36-a9df0e5b55de","order_by":1,"name":"Vijay 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1","display":"","copyAsset":false,"role":"figure","size":525152,"visible":true,"origin":"","legend":"\u003cp\u003eA,B,C-Radiological images showing posterior wall and posterior column fracture of the right acetabulum D-Post-operative X-ray showing reduced fracture with implant insitu\u003c/p\u003e","description":"","filename":"FIGURE1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5338947/v1/1ad3ba046ce2f2758d7254fb.jpg"},{"id":69421745,"identity":"f44e25a1-8574-446f-b1ed-ffbb9b92cf9e","added_by":"auto","created_at":"2024-11-20 07:53:53","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":774958,"visible":true,"origin":"","legend":"\u003cp\u003eIntra-operative image demonstrating entrapped Obturator internus muscle between fracture fragments (Green arrow represents the obturator internus muscle)\u003c/p\u003e","description":"","filename":"FIGURE2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5338947/v1/bf8d1674a63707ef90d0a836.jpg"},{"id":69420875,"identity":"a3c7a058-b7d4-4ab7-a402-fbca2f200514","added_by":"auto","created_at":"2024-11-20 07:45:53","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":377833,"visible":true,"origin":"","legend":"\u003cp\u003eCT Coronal(A) ,Axial(B),3D reconstruction (C and D) section of pelvis demonstrating infrafoveal femoral head fracture and posterior wall fracture\u003c/p\u003e","description":"","filename":"FIGURE3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5338947/v1/d9180c352d1edee5647d738e.jpg"},{"id":69421746,"identity":"75ecfcc1-206b-43f4-9388-3773eb709408","added_by":"auto","created_at":"2024-11-20 07:53:53","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":375042,"visible":true,"origin":"","legend":"\u003cp\u003e(A) X-ray pelvis with both hip shows dislocated right hip dislocation,posterior wall fracture and femoral head fracture ,(B)Post-operative X-ray pelvis with both hip showing reduced fracture with implant insitu\u003c/p\u003e","description":"","filename":"FIGURE4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5338947/v1/843d85f8817f2caa1eb91d80.jpg"},{"id":69420876,"identity":"b8824c0d-d8f9-4a94-85c4-1c241d40bec8","added_by":"auto","created_at":"2024-11-20 07:45:53","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":861627,"visible":true,"origin":"","legend":"\u003cp\u003eIntra-operative image demonstrating entrapped Obturator internus muscle between fracture fragments (yellow arrow represents the obturator internus muscle)\u003c/p\u003e","description":"","filename":"FIGURE5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5338947/v1/93fad64b4e7c8ec621c6899f.jpg"},{"id":100418827,"identity":"776abde9-464d-4ca3-be45-5bf3d9a3f21a","added_by":"auto","created_at":"2026-01-16 13:26:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3286749,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5338947/v1/3e9c360d-7262-425e-a7b9-9a5b7f3d45d1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Obturator Internus Muscle Entrapment in Posterior Wall Acetabular Fractures: A Rare Intraoperative Finding","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAcetabular fractures present a significant challenge to orthopaedic surgeons due to the complex osseous and surgical anatomy(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). Posterior wall fractures are the most common type of acetabular fractures, accounting for one-fourth to one-third of all acetabular fractures. Displaced posterior wall fractures are managed with anatomical reduction of the articular surface and rigid internal fixation followed by early mobilisation(\u003cspan additionalcitationids=\"CR3 CR4 CR5 CR6\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). The Kocher-Langenbeck approach is commonly used for posterior wall fractures, providing direct access to the posterior wall and posterior column, and indirect access to the superior wall and quadrilateral surface. Proper visualization and isolation of the short external rotator muscles are crucial steps in KL approach for posterior wall fracture reduction and fixation(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis article presents two case reports of posterior wall fractures with obturator internus entrapment between the fractured fragments. Currently, no literature reports obturator internus interposition in posterior wall fractures, although piriformis muscle entrapment has been documented(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e"},{"header":"Case Report","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eCase 1:\u003c/h2\u003e \u003cp\u003eA 38-year-old male presented to the emergency department with pain in the right hip and knee following a road traffic accident involving a collision between a four-wheeler and a truck. He was unable to bear weight on his right lower limb and presented with significant swelling and deformity of the right knee.\u003c/p\u003e \u003cp\u003eOn examination, there was tenderness around the right hip with painful movements. The patient also had a dislocated right knee, which was reduced in the emergency department under sedation, with no distal neurovascular deficits. Radiographic imaging revealed a displaced posterior acetabular wall fracture with a posterior column fracture. The displaced fracture fragment measured approximately 3.0 \u0026times; 2.8 \u0026times; 1.0 cm and was displaced by about 1 cm posteriorly.\u003c/p\u003e \u003cp\u003eThe patient was scheduled for surgical intervention the following day, after a pre-anesthesia checkup. The surgical procedure was performed with the patient in the left lateral decubitus position, using a standard Kocher-Langenbeck approach to access the hip. After identifying the piriformis, superior gemellus, and inferior gemellus, they were tagged and cut 1.5 cm from their attachment to the greater trochanter. However, the obturator internus was not visualized initially. Further exposure of the fracture site and freshening of the margins revealed that the obturator internus muscle was interposed between the fracture site and the displaced fragment (Fig.\u0026nbsp;2). This interposition likely accounted for the difficulty in achieving complete reduction. The obturator internus muscle was released 1.5 cm away from its insertion in a traditional way, followed by the reduction of the posterior wall fragment onto the posterior column. It was provisionally stabilised using K-wires, and final fixation was achieved using a buttress plate. The short external rotators were reattached with No. 5 Ethibond (Ethicon W4846, USA) sutures, and the hip was checked through a range of motion to confirm stability. Rehabilitation began immediately post-operatively. At the six-month follow-up, radiographs were satisfactory, and the patient could ambulate freely without pain.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eFigure 1\u003c/strong\u003e \u003cp\u003eA,B,C-Radiological images showing posterior wall and posterior column fracture of the right acetabulum D-Post-operative X-ray showing reduced fracture with implant insitu\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eFigure 2\u003c/strong\u003e \u003cp\u003eIntra-operative image demonstrating entrapped Obturator internus muscle between fracture fragments (Green arrow represents the obturator internus muscle)\u003c/p\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCase 2:\u003c/h3\u003e\n\u003cp\u003eA 43-year-old male presented to the trauma and emergency department with complaints of abdominal pain and right hip pain following a road traffic accident, in which a four-wheeler was hit head-on by another four-wheeler.\u003c/p\u003e \u003cp\u003eHe was stabilised as per the ATLS protocol and was diagnosed with a mesenteric injury with serosal tears, haemoperitoneum, right posterior hip dislocation, femoral head fracture, and posterior wall acetabular fracture. He underwent reduction of the right hip dislocation and emergency laparoscopic repair for the mesenteric injury and serosal tear.\u003c/p\u003e \u003cp\u003eFurther imaging revealed an infra-foveal femoral head fracture and a posterior wall fracture (Pipkin type 4), along with intra-articular fragments in the hip joint. Following stabilisation of the abdominal injuries, he was scheduled for acetabular fracture fixation. The Kocher-Langenbeck approach was used with the patient in the left lateral decubitus position. After developing the planes, the piriformis, superior gemellus, and inferior gemellus were identified, tagged, and released. The posterior wall fracture fragment was visualized before the visualization of the obturator internus. Lateral traction with a Steinmann pin to the femoral head was used for joint distraction. When the posterior wall fragment was elevated to inspect the joint, obturator internus interposition was noted between the fracture fragments (Figure:5). The obturator internus muscle was released away from the insertion, and the infra-foveal femoral head fragment and intra-articular bone fragments were removed. A thorough joint wash was performed. Complete reduction of the posterior wall fragment was achieved, and the fragment was fixed using an interfragmentary screw and buttressed with a plate.The short external rotators were reattached with No. 5 Ethibond (Ethicon W4846, USA) sutures, and the wound was closed in layers after confirming stability.\u003c/p\u003e \u003cp\u003ePartial weight-bearing was initiated after suture removal at two weeks, and full weight-bearing was allowed after six weeks. Regular follow-up through clinical examination and X-ray was performed. Figure\u0026nbsp;3 : CT Coronal(A) ,Axial(B),3D reconstruction (C and D) section of pelvis demonstrating infrafoveal femoral head fracture and posterior wall fracture\u003c/p\u003e \u003cp\u003eAt the one-year follow-up, the patient was walking without limping or pain.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eFigure 5\u003c/strong\u003e \u003cp\u003eIntra-operative image demonstrating entrapped Obturator internus muscle between fracture fragments (yellow arrow represents the obturator internus muscle)\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eFigure 4\u003c/strong\u003e \u003cp\u003e(A) X-ray pelvis with both hip shows dislocated right hip dislocation,posterior wall fracture and femoral head fracture ,(B)Post-operative X-ray pelvis with both hip showing reduced fracture with implant insitu\u003c/p\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe incidence of acetabular fractures has increased in recent years due to the rise in road traffic accidents (\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). The hip joint is a major weight-bearing joint, playing a crucial role in mobility and daily activities (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). With the increasing awareness of the complexity of acetabular fractures and the importance of achieving good prognoses, more of these fractures are being surgically treated (\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Important goals in managing acetabular fractures include joint preservation, congruency, and stability with minimal disturbance to the blood supply. A sound knowledge of rare intraoperative findings plays a significant role in effectively managing these fractures.\u003c/p\u003e \u003cp\u003eThe interposition of soft tissue in posterior wall fractures is a rare occurrence. Soft tissue entrapments can impede anatomical reduction, leading to incongruency of the hip joint and subsequent poor outcomes. A comprehensive literature search was conducted using three online databases: PubMed, Cochrane, and Embase, with the keywords \"obturator internus interposition/entrapment,\" \"soft tissue interposition/entrapment in acetabular fractures,\" and \"short external rotators interposition/entrapment.\" This search yielded only one relevant case report by Beyer et al., who documented a case of a 12-year-old child with piriformis entrapment in a posterior wall fracture (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Notably, our literature search did not reveal any previous studies on obturator internus interposition. To our knowledge, this case report represents the first documented instance of this specific entrapment.\u003c/p\u003e \u003cp\u003eThis case report demonstrates the rare but significant occurrence of obturator internus muscle entrapment in posterior wall acetabular fractures. It highlights the importance of recognizing that any shortened external rotators, including the obturator internus, can become entrapped and potentially prevent the anatomical reduction of the posterior wall of the acetabulum during the surgery. Vigilantly recognizing these rare possibilities is crucial for surgeons to effectively manage such complex situations.\u003c/p\u003e \u003cp\u003eFurther documentation of similar cases will help broaden the understanding of this rare presentation and guide future surgical strategies in managing complex acetabular fractures.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis case highlights the importance of recognizing potential soft tissue interpositions, such as obturator internus entrapment, in posterior acetabular wall fractures. Proper surgical planning and meticulous intraoperative management are crucial to ensure successful fracture reduction and fixation. Awareness of such unusual presentations can help optimize outcomes in complex trauma cases.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;No funding was received to assist with the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Approval\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Ethics approval was not required for this case report.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate and Consent to Publish\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Written informed consent was obtained from both patients for participation and publication of this case report and any accompanying images.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contributions\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The first draft of the manuscript was written by Dr. Babu Mohammed Rafi V., who also led manuscript drafting. Prof. Vijay Sharma was responsible for manuscript revision, patient management, and patient follow-up. All authors contributed to the study conception and design, reviewed, and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The authors wish to thank the patients and their relatives for their support.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest Summary Statement\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The authors declare no conflicts of interest related to this work.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKim HT, Ahn JM, Hur JO, Lee JS, Cheon SJ. Reconstruction of acetabular posterior wall fractures. 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Fractures of the acetabulum: Accuracy of reduction and clinical results in patients managed operatively within three weeks after the injury. Journal of Bone and Joint Surgery. 1996;78(11):1632\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatta JM, Mehne DK, Roffi R. Fractures of the acetabulum. Early results of a prospective study. Clinical Orthopaedics and Related Research. 1986;NO. 205:241\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e\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":"Acetabulum, Fractures, Posterior wall, Obturator internus, Entrapment, Kocher-Langenbeck","lastPublishedDoi":"10.21203/rs.3.rs-5338947/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5338947/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIntroduction:\u003c/p\u003e \u003cp\u003eWe report two cases of the rare presentation of obturator internus muscle entrapment in posterior wall fractures of the acetabulum. While piriformis muscle entrapment has been previously reported, there are no known cases of obturator internus entrapment associated with posterior wall fractures of the acetabulum.\u003c/p\u003e \u003cp\u003eCase Presentation:\u003c/p\u003e \u003cp\u003eCase 1: A 38-year-old male presented with right hip and knee pain following a road traffic accident. He was diagnosed with a posterior wall and posterior column fracture, accompanied by posterior dislocation of the knee. During surgery, the obturator internus muscle was found interposed between the fracture site and the displaced posterior wall fragment.\u003c/p\u003e \u003cp\u003eCase 2: A 43-year-old male sustained blunt abdominal trauma and a Pipkin type 4 (femoral head fracture with posterior wall fracture) injury following a road traffic accident. After stabilization of his abdominal injury with laparoscopic mesenteric repair, the patient underwent open reduction and internal fixation of the posterior wall fracture, along with removal of intra-articular bony fragments from an infra-foveal femoral head fracture. Similarly, during the procedure, the obturator internus muscle was found interposed between the fracture site and the displaced posterior wall fragment.\u003c/p\u003e \u003cp\u003eBoth patients followed a standard post-operative rehabilitation protocol and recovery was uneventful.\u003c/p\u003e \u003cp\u003eConclusion:\u003c/p\u003e \u003cp\u003eThese cases highlight the importance of recognizing muscle entrapment as a potential cause of difficulty in reducing posterior acetabular wall fractures. Proper identification and management of such interpositions are crucial to ensure successful fracture reduction and fixation.\u003c/p\u003e","manuscriptTitle":"Obturator Internus Muscle Entrapment in Posterior Wall Acetabular Fractures: A Rare Intraoperative Finding","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-20 07:45:48","doi":"10.21203/rs.3.rs-5338947/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":"10cda291-f750-4b14-9ded-3bcb7e8f5e62","owner":[],"postedDate":"November 20th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-16T13:06:17+00:00","versionOfRecord":[],"versionCreatedAt":"2024-11-20 07:45:48","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5338947","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5338947","identity":"rs-5338947","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}