Title: Hybrid Anteroposterior–Posteroanterior Headless Screw Fixation Improves Biomechanical Stability of Capitellar Coronal Shear Fractures: A Paired Cadaveric Study

Title: Hybrid Anteroposterior–Posteroanterior Headless Screw Fixation Improves Biomechanical Stability of Capitellar Coronal Shear Fractures: A Paired Cadaveric Study | 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 Title: Hybrid Anteroposterior–Posteroanterior Headless Screw Fixation Improves Biomechanical Stability of Capitellar Coronal Shear Fractures: A Paired Cadaveric Study Feras Qawasmi, Sonia Slusarczyk, Steven I. Grindel, Hamza Murad, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8584608/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract OBJECTIVE: To compare the biomechanical performance of a hybrid headless-screw construct (one anteroposterior [AP] and one posteroanterior [PA]) with a traditional PA-only (two PA screws) construct in a paired cadaveric model of capitellar coronal-shear fractures. Methods: Seven pairs of fresh-frozen cadaveric humeri were used. Simulated Bryan–Morrey type I coronal-shear capitellar fractures were created and fixed with Acutrak cannulated headless compression screws. Each pair received either hybrid fixation (one AP and one PA screw) or two PA screws. Constructs underwent cyclic loading followed by load-to-failure testing. Force and displacement were sampled at 100 Hz during selected cycles (cycles 1–10, 100–110 and 491–500). Data were analyzed using paired statistical tests; a p-value < 0.05 was considered significant. Results: Hybrid fixation showed greater initial stiffness than PA-only (277.8 ± 64.6 vs 166.6 ± 51.0 N/mm; p = 0.036). Although stiffness remained higher with hybrid after further cycling, later differences were not statistically significant. Load-to-failure was higher with hybrid (253.7 ± 75.8 vs 151.6 ± 29.9 N; p = 0.014). Failure displacement did not differ (1.21 ± 0.43 vs 1.06 ± 0.35 mm; p = 0.42). Overall, hybrid constructs demonstrated ≈67% greater initial stiffness and ≈67% greater failure load versus PA-only. Conclusion: In this paired cadaveric model of capitellar shear fractures, a hybrid AP–PA screw orientation improved early construct stiffness and increased failure tolerance compared with two PA screws. These biomechanical advantages may support early supervised motion while maintaining construct integrity, however, clinical correlation is required. LEVEL OF EVIDENCE: IV (cadaveric biomechanical study). Capitellar fracture Hybrid screw fixation Headless compression screw ORIF Screw orientation Elbow biomechanics Cadaveric study Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Capitellar fractures of the distal humerus are difficult to manage owing to their intra-articular nature and propensity to impair elbow function. Without appropriate treatment, sequelae include a restricted range of motion, persistent pain, and post-traumatic arthritis. Surgical options include open reduction and internal fixation (ORIF), arthroscopic techniques, and—selectively—fragment excision. Among these, ORIF is most commonly used because it permits anatomic reduction and stable fixation. Coronal shear fractures typically result from axial and valgus loading, such as a fall on an outstretched hand. Headless compression screws are widely used for fixation; however, the optimal screw direction remains debated [1–8] . Biomechanical data have suggested that PA screws may provide greater construct stability than AP screws, and small clinical series have reported favorable results with two PA screws. Nevertheless, AP screw placement can offer technical advantages, including easier access and less posterior soft-tissue dissection in minimally invasive approaches. To date, the biomechanics of a hybrid configuration (one AP and one PA screw) have not been evaluated in a paired model. Therefore, the present study compared hybrid AP–PA fixation with PA-only fixation in a paired cadaveric model of capitellar fractures. We hypothesized that hybrid fixation would demonstrate greater or at least non-inferior mechanical stability compared with two PA screws. Materials and Methods Design and setting A paired cadaveric biomechanical study was performed in a university biomechanics laboratory Specimens and allocation. Seven matched pairs of fresh-frozen cadaveric humeri (6 male, 1 female; mean age 60.4 years, range 51–65 years) were used. Within each pair, one side was randomized to hybrid fixation (one AP and one PA headless compression screw) and the contralateral side to PA-only fixation (two PA screws). Screening radiographs excluded gross osseous defects or previous surgical intervention. All soft tissues and musculature were removed from the humeri prior to testing. Fracture model and reduction: A standardized Bryan Morrey type I [9] coronal-shear osteotomy was created with a micro-saw using two osteotomies: (1) a coronal osteotomy at the posterior margin of the articular surface, and (2) a sagittal osteotomy along the lateral trochlear edge (Fig. 3). Fragments were anatomically reduced and held with a C-clamp before fixation. Guide Kirschner wires (K-wires, 1.6 mm) were used (Fig.4). Pilot drilling and screw insertion followed the manufacturer's recommendations for 4.0-mm headless compression screws (Acutrak® 2 Standard; Acumed, Hillsboro, OR, USA) (Fig.5). All osteotomies and screw fixations were performed by a single fellowship-trained shoulder-and-elbow surgeon to minimize inter-operator variability. Fixation techniques Hybrid (AP–PA): K-wires were placed anterolaterally on the capitellum and posteromedially on the fragment to guide screw paths. Both screws were inserted perpendicular to the osteotomy plane. The AP screw was inserted first to achieve AP compression, followed by PA fixation. PA-only: Medial and lateral K-wires were placed at the same level, perpendicular to the osteotomy plane, and two identical screws were inserted. Final screw lengths were measured with a depth gauge and recorded: AP screws mean 22 ± 3 mm (range 18–26 mm), PA screws: mean 24 ± 3 mm (range 20–28 mm. All screw heads were buried below the articular surface. Biomechanical testing. Mechanical testing was performed on a servo-hydraulic system (Landmark 370, MTS Systems, Eden Prairie, MN, USA). An investigator not involved in fixation performed testing. To apply loading, a proximal segment of a composite radius (Sawbones, Pacific Research Laboratories, Vashon, WA, USA) was secured to the actuator and articulated with the capitellum to simulate 20° of elbow flexion, the position associated with peak radiocapitellar contact forces [10] (Fig. 1). Constructs were cyclically loaded between 0–75 N at 1 Hz for 500 cycles. Force and displacement were sampled at 100 Hz during cycles 1–10, 100–110, and 491–500. Monotonic load-to-failure testing was then performed at a displacement rate of 0.5 mm/s. Failure was defined as a sudden drop in load during testing. Outcomes and statistical analysis Primary outcome variables were failure load and construct stiffness, evaluated at the beginning and end of cyclic loading. Data normality was assessed with the Shapiro–Wilk test. Paired comparisons were performed using a two-tailed paired Student’s t-test for normally distributed data for normally distributed data or the Wilcoxon signed-rank test for non-normally distributed data). A p -value of <0.05 was considered statistically significant. Results Stiffness during cyclic loading. Stiffness increased in both constructs across cycles (Fig. 2). At cycles 1–10, hybrid fixation demonstrated greater stiffness than PA-only (277.8 ± 64.6 vs 166.6 ± 51.0 N/mm; paired Δ = 111.2 N/mm; p = 0.036), representing a 67% increase. although stiffness remained greater for hybrid at cycles 100–110 and 491-500 (289.3 ± 61.8 vs 194.6 ± 58.2 N/mm and 337.1 ± 95.6 vs 229.2 ± 45.3 N/mm, respectively), these later differences did not reach statistical significance. Load to failure and failure displacement. Hybrid constructs withstood a higher failure load than PA-only constructs (253.7 ± 75.8 vs 151.6 ± 29.9 N; paired Δ = 102.1 N; p = 0.014), a 67% increase. Failure displacement did not differ significantly between groups (1.21 ± 0.43 vs 1.06 ± 0.35 mm; p = 0.42). Discussion Capitellar fractures are challenging to manage because of their complex intra-articular geometry, limited bone stock for purchase, and risk of complications. Headless compression screws are commonly used to resist shear and rotational displacement, yet the optimal screw orientation remains debated [11]. In this paired cadaveric biomechanical study, a hybrid construct one AP and one PA screw demonstrated greater early construct stiffness and a higher load to failure than two PA screws in simulated coronal-shear fractures. Drawbacks of two AP screws include traversal of the articular surface, which increases the risk of iatrogenic cartilage injury and may allow the fragment to collapse into the posterior cortex [12](Tarallo et al., 2021).In addition, access to the medial capitellum via an AP path is also limited by surrounding soft tissues, making precise placement demanding. Conversely, two PA screws fixation is constrained by a narrow posterior approach [2], and by the need to obtain secure purchase in fragments with scant subchondral bone while avoiding intra-articular penetration [3,12]. A hybrid configuration (one AP and one PA screw) facilitates effective compression across the fracture and offers more versatile trajectories. The hybrid construct showed significantly greater initial stiffness (p = 0.036) and a higher failure load (p = 0.014), supporting the biomechanical premise that opposing compressive vectors improve stability. Combining anteroposterior (AP) and posteroanterior (PA) trajectories may better resist multidirectional shear at the radiocapitellar joint, particularly early after fixation. This added stability could enable earlier range-of-motion exercises to limit postoperative stiffness while maintaining construct integrity until union. Prior biomechanical work suggested PA screws may confer greater stability than AP screws during cyclic loading, although some investigations reported trends without statistical significance [13]. In the present model, hybrid fixation sustained a 67% higher failure load ( p = 0.014) and exhibited 67% greater initial stiffness ( p = 0.036). With continued cycling, stiffness increased in both groups and the relative hybrid advantage narrowed, but a ~47% stiffness benefit persisted by the end of testing. These data suggest that a hybrid screw orientation confers greater early mechanical stability , which may limit interfragmentary micromotion and foster conditions favorable for osseous primary healing. The added stability could also permit earlier, supervised elbow mobilization — important because postoperative stiffness is a common complication after capitellar fracture fixation. Previous studies by Puloski et al. and Tarallo et al. have emphasized that immediate postoperative motion is essential in minimizing joint stiffness [12,14]. At the point of failure, the hybrid fixation configuration tolerated significantly higher loads compared to the PA-only fixation, highlighting its enhanced capacity to withstand physiologic stress and reducing the likelihood of construct failure under normal loading conditions. While headless compression screw fixation has generally demonstrated clinical success, previous studies have noted hardware failure as a potential drawback associated with these implants [3,13,15,16]. Our findings suggest that hybrid screw orientation offers improved resistance to catastrophic failure, which may translate into more durable fixation and reduced risk of hardware-related complications in clinical settings, particularly in active or load-bearing patients. Limitations This study has several limitations. First, all specimens came from older donors; although capitellar fractures are common in the elderly, these cadavers may not reflect the bone quality or healing potential of younger patients. Second, our testing used simplified loading that does not reproduce the elbow’s complex, multidirectional forces during daily activities. Third, we modeled a Bryan–Morrey type I coronal-shear pattern, so the findings may not generalize to fractures with greater displacement, comminution, or trochlear extension. Finally, while hybrid fixation demonstrated superior early mechanics, we did not evaluate clinical endpoints (union, function, or complications), clinical studies are therefore necessary to confirm the relevance of these biomechanical results. Conclusion In this paired cadaveric model, hybrid AP–PA fixation demonstrated significantly greater early stiffness and higher failure load than two PA screws. These findings support a biomechanical advantage of opposing screw vectors for coronal capitellar fractures; further clinical studies are required to validate translation to patient outcomes. Declarations Ethics Approval and Consent to Participate: Cadaveric specimens were obtained from de-identified donated bodies through institutional donation programs. Institutional review board approval was not required according to local regulations and institutional policy. Consent to publish Not applicable. Availability of Data and Materials: The datasets generated and/or analyzed 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: No external funding or grants were used for the completion of this study. Acknowledgments: We acknowledge Logan M. Andryk for assistance in the laboratory and Fadi Shweiki for creating the illustration. Author Contributions: Feras Qawasmi, MD: Conceptualization of the study, supervision of cadaveric experiments, manuscript drafting, and final approval of submitted version. Sonia Slusarczyk, MSc: Biomechanical testing, data collection, and data analysis. Steven I. Grindel, PhD: Statistical analysis, data interpretation, and critical manuscript review. Hamza Murad, MD: Assistance in specimen preparation and fracture modeling. Mei Wang, PhD: Data validation, review of biomechanical methods, and manuscript editing. Mustafa Yassin, MD: Support in fixation procedures and methodological guidance Level of Evidence: IV Potential Conflicts of Interest and Funding Sources: No outside funding or grants were used for the completion of this study. None are declared. Acknowledgments: We acknowledge Logan M. Andryk for help in the laboratory and Fadi Shweiki for creating the illustration. Ethics approval and consent to participate This study was conducted on human cadaveric specimens. According to national regulations and institutional policies, ethical approval and Institutional Review Board (IRB) review were not required, as the study did not involve living participants or identifiable human data. All cadaveric specimens were obtained through a legally authorized body donation program, with written informed consent provided prior to death for research and educational purposes. The study was conducted in accordance with the principles of the Declaration of Helsinki. References Ballesteros-Betancourt JR, García-Tarriño R, García-Elvira R, Muñoz-Mahamud E, Fernández-Valencia JA, Llusá-Pérez M, Combalia-Aleu A. The anterior limited approach of the elbow for the treatment of capitellum and trochlea fractures: Surgical technique and clinical experience in eight cases. Injury. 2020 Apr;51 Suppl 1:S103–11. BAYDAR M, AYKUT S, MERT M, KESKINBIÇKI MV, AKDENIZ HE, ÖZTÜRK K. ISOLATED CAPITELLAR FRACTURE FIXATION WITH HEADLESS SCREWS IN DIFFERENT CONFIGURATIONS. Acta Ortop Bras. 2022;30(1). Bellato E, Giai Via R, Bachman D, Zorzolo I, Marmotti A, Castoldi F. Coronal Shear Fractures of the Distal Humerus. J Funct Morphol Kinesiol. 2022 Jan 6;7(1):7. Bilsel K, Atalar AC, Erdil M, Elmadag M, Sen C, Demirhan M. Coronal plane fractures of the distal humerus involving the capitellum and trochlea treated with open reduction internal fixation. Arch Orthop Trauma Surg. 2013 Jun 15;133(6):797–804. Borbas P, Vetter M, Loucas R, Hofstede S, Wieser K, Ernstbrunner L. Biomechanical stability of simple coronal shear fracture fixation of the capitellum. J Shoulder Elbow Surg. 2021 Aug;30(8):1768–73. Elkowitz SJ, Polatsch DB, Egol KA, Kummer FJ, Koval KJ. Capitellum Fractures: A Biomechanical Evaluation of Three Fixation Methods. J Orthop Trauma. 2002 Aug;16(7):503–6. Kurtulmus T, Saglam N, Saka G, Avci CC, Kucukdurmaz F, Akpinar F. Posterior fixation of type IV humeral capitellum fractures with fully threaded screws in adolescents. European Journal of Trauma and Emergency Surgery. 2014 Jun 26;40(3):379–85. Yu T, Tao H, Xu F, Hu Y, Zhang C, Zhou G. Comparison of lateral approach versus anterolateral approach with Herbert screw fixation for isolated coronal shear fractures of humeral capitellum. J Orthop Surg Res. 2019 Dec 22;14(1):230. Jupiter JB, Mehne DK. FRACTURES OF THE DISTAL HUMERUS. Orthopedics. 1992 Jul;15(7):825–33. Kurtulmus T, Saglam N, Saka G, Avci CC, Kucukdurmaz F, Akpinar F. Posterior fixation of type IV humeral capitellum fractures with fully threaded screws in adolescents. European Journal of Trauma and Emergency Surgery. 2014 Jun 26;40(3):379–85. Borbas P, Loucas R, Loucas M, Vetter M, Hofstede S, Ernstbrunner L, Wieser K. Biomechanical stability of complex coronal plane fracture fixation of the capitellum. Arch Orthop Trauma Surg. 2021 Aug 23;142(11):3239–46. Tarallo L, Novi M, Porcellini G, Giorgini A, Micheloni G, Catani F. Surgical tips and tricks for coronal shear fractures of the elbow. Arch Orthop Trauma Surg. 2021 Feb 3;141(2):261–70. Elkowitz SJ, Kubiak EN, Polatsch D, Cooper J, Kummer FJ, Koval KJ. Comparison of two headless screw designs for fixation of capitellum fractures. Bull Hosp Jt Dis. 2003;61(3–4):123–6. Puloski S, Kemp K, Sheps D, Hildebrand K, Donaghy J. Closed Reduction and Early Mobilization in Fractures of the Humeral Capitellum. J Orthop Trauma. 2012 Jan;26(1):62–5. Cheung E V. Fractures of the Capitellum. Hand Clin. 2007 Nov;23(4):481–6. Elkowitz SJ, Polatsch DB, Egol KA, Kummer FJ, Koval KJ. Capitellum Fractures: A Biomechanical Evaluation of Three Fixation Methods. J Orthop Trauma. 2002 Aug;16(7):503–6. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 27 Apr, 2026 Editor assigned by journal 02 Feb, 2026 Submission checks completed at journal 31 Jan, 2026 First submitted to journal 28 Jan, 2026 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-8584608","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":633933651,"identity":"7f8fac49-2840-4df2-8812-e0705bf3d24f","order_by":0,"name":"Feras Qawasmi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyUlEQVRIiWNgGAWjYBAC9gYkFjNRWngOwBhAFqlaJBKI1cLe+/Djzx02+faSbww/F1TYMPC3dyfg18Jz3Fia90yaZY90jrH0jDNpDBJnzm7Aq8VeIo1BmrHtsAGPdI6BNG/bYQYDiVz8WnjknzH//AnSInnG+DdxWiTY2CR4QVokeMyItIUnjc0a6BcDnjNpZdZAgoegX3jYjzHfBIaYAXv74c23eSps5Pjbe/FrAQPGBhDJYQA2g7ByhBb2B8SpHgWjYBSMghEHAN2APb0SJHSnAAAAAElFTkSuQmCC","orcid":"","institution":"Tel Aviv University","correspondingAuthor":true,"prefix":"","firstName":"Feras","middleName":"","lastName":"Qawasmi","suffix":""},{"id":633933652,"identity":"9f2cf0ae-8bcd-40c0-b2da-0fc47dfb1376","order_by":1,"name":"Sonia Slusarczyk","email":"","orcid":"","institution":"Medical College of Wisconsin","correspondingAuthor":false,"prefix":"","firstName":"Sonia","middleName":"","lastName":"Slusarczyk","suffix":""},{"id":633933653,"identity":"813db847-92da-4728-9421-da3f534b6816","order_by":2,"name":"Steven I. Grindel","email":"","orcid":"","institution":"Medical College of Wisconsin","correspondingAuthor":false,"prefix":"","firstName":"Steven","middleName":"I.","lastName":"Grindel","suffix":""},{"id":633933654,"identity":"98d766b3-f4f9-485e-8ee0-24e372180473","order_by":3,"name":"Hamza Murad","email":"","orcid":"","institution":"Tel Aviv University","correspondingAuthor":false,"prefix":"","firstName":"Hamza","middleName":"","lastName":"Murad","suffix":""},{"id":633933655,"identity":"44506ef6-edca-41be-9f37-3beb5b9451a9","order_by":4,"name":"Mei Wang","email":"","orcid":"","institution":"Marquette University","correspondingAuthor":false,"prefix":"","firstName":"Mei","middleName":"","lastName":"Wang","suffix":""},{"id":633933656,"identity":"3164949f-634d-4c24-b504-ae14e980e932","order_by":5,"name":"Mustafa Yassin","email":"","orcid":"","institution":"Tel Aviv University","correspondingAuthor":false,"prefix":"","firstName":"Mustafa","middleName":"","lastName":"Yassin","suffix":""}],"badges":[],"createdAt":"2026-01-12 18:23:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8584608/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8584608/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108584169,"identity":"b497a3a3-aaad-4221-a7c9-655c00adf007","added_by":"auto","created_at":"2026-05-06 08:36:04","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":268952,"visible":true,"origin":"","legend":"\u003cp\u003eTesting setup.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8584608/v1/98e4e99597bc1bf77e62e1cb.png"},{"id":108805473,"identity":"bbc5f7a1-40a9-4328-b34a-a6a9ab9caf53","added_by":"auto","created_at":"2026-05-08 15:26:04","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":112556,"visible":true,"origin":"","legend":"\u003cp\u003eConstruct stiffness at 10\u003csup\u003eth\u003c/sup\u003e, 110\u003csup\u003eth\u003c/sup\u003e, and 500\u003csup\u003eth\u003c/sup\u003e cycles.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8584608/v1/fa1362399fe3aa71ec881dd0.png"},{"id":108584172,"identity":"8d8fda08-8b8a-4e09-a364-bbc1ee915fbb","added_by":"auto","created_at":"2026-05-06 08:36:04","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":322052,"visible":true,"origin":"","legend":"\u003cp\u003eThe osteotomy is held with a pickup; the yellow outline delineates the osteotomy bed.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8584608/v1/fc124c03c33bd6f38b1a7bff.png"},{"id":108584170,"identity":"04bb6db0-d971-42ac-8388-359f393ab236","added_by":"auto","created_at":"2026-05-06 08:36:04","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":262677,"visible":true,"origin":"","legend":"\u003cp\u003eReduction of the capitellar fracture with provisional K-wire fixation, just prior to drilling.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8584608/v1/0a502f030420e73600b5ae26.png"},{"id":108805302,"identity":"de8b9d40-1728-46ea-8c00-02973980b5fe","added_by":"auto","created_at":"2026-05-08 15:25:32","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":231219,"visible":true,"origin":"","legend":"\u003cp\u003eHybrid AP/PA screw construct (left) versus two PA screws (right)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8584608/v1/8032fcbbb717e44dbd6f136e.png"},{"id":108809663,"identity":"2c265c28-4fef-4dd5-bd59-f74fdd0d382e","added_by":"auto","created_at":"2026-05-08 15:54:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1602056,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8584608/v1/f34abbf4-4271-403e-869d-1b066e14d22a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Title: Hybrid Anteroposterior–Posteroanterior Headless Screw Fixation Improves Biomechanical Stability of Capitellar Coronal Shear Fractures: A Paired Cadaveric Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCapitellar fractures of the distal humerus are difficult to manage owing to their intra-articular nature and propensity to impair elbow function. Without appropriate treatment, sequelae include a restricted range of motion, persistent pain, and post-traumatic arthritis. Surgical options include open reduction and internal fixation (ORIF), arthroscopic techniques, and\u0026mdash;selectively\u0026mdash;fragment excision. Among these, ORIF is most commonly used because it permits anatomic reduction and stable fixation.\u003c/p\u003e\n\u003cp\u003eCoronal shear fractures typically result from axial and valgus loading, such as a fall on an outstretched hand. Headless compression screws are widely used for fixation; however, the optimal screw direction remains debated\u0026nbsp;[1\u0026ndash;8]\u0026nbsp;. Biomechanical data have suggested that PA screws may provide greater construct stability than AP screws, and small clinical series have reported favorable results with two PA screws. Nevertheless, AP screw placement can offer technical advantages, including easier access and less posterior soft-tissue dissection in minimally invasive approaches.\u003c/p\u003e\n\u003cp\u003eTo date, the biomechanics of a hybrid configuration (one AP and one PA screw) have not been evaluated in a paired model. Therefore, the present study compared hybrid AP\u0026ndash;PA fixation with PA-only fixation in a paired cadaveric model of capitellar fractures. We hypothesized that hybrid fixation would demonstrate greater or at least non-inferior mechanical stability compared with two PA screws.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003e\u003cstrong\u003eDesign and setting\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA paired cadaveric biomechanical study was performed in a university biomechanics laboratory\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSpecimens and allocation.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSeven matched pairs of fresh-frozen cadaveric humeri (6 male, 1 female; mean age 60.4 years, range 51\u0026ndash;65 years) were used. Within each pair, one side was randomized to hybrid fixation (one AP and one PA headless compression screw) and the contralateral side to PA-only fixation (two PA screws).\u0026nbsp;Screening radiographs excluded gross osseous defects or previous surgical intervention. All soft tissues and musculature were removed from the humeri prior to testing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFracture model and reduction:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA standardized Bryan Morrey type I [9] coronal-shear osteotomy was created with a micro-saw using two osteotomies: (1) a coronal osteotomy at the posterior margin of the articular surface, and (2) a sagittal osteotomy along the lateral trochlear edge (Fig. 3). Fragments were anatomically reduced and held with a C-clamp before fixation. Guide Kirschner wires (K-wires, 1.6 mm) were used (Fig.4). Pilot drilling\u0026nbsp;and screw insertion followed the manufacturer\u0026apos;s recommendations for 4.0-mm headless compression screws\u0026nbsp;(Acutrak\u0026reg; 2 Standard; Acumed, Hillsboro, OR, USA) (Fig.5). All osteotomies and screw fixations were performed by a single fellowship-trained shoulder-and-elbow surgeon to minimize inter-operator variability.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFixation techniques\u003c/strong\u003e\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eHybrid (AP\u0026ndash;PA): K-wires were placed anterolaterally on the capitellum and posteromedially on the fragment to guide screw paths. Both screws were inserted perpendicular to the osteotomy plane. The AP screw was inserted first to achieve AP compression, followed by PA fixation.\u003c/li\u003e\n \u003cli\u003ePA-only: Medial and lateral K-wires were placed at the same level, perpendicular to the osteotomy plane, and two identical screws were inserted. Final screw lengths were measured with a depth gauge and recorded: AP screws mean 22 \u0026plusmn; 3 mm (range 18\u0026ndash;26 mm), PA screws: mean 24 \u0026plusmn; 3 mm (range 20\u0026ndash;28 mm. All screw heads were buried below the articular surface.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eBiomechanical testing.\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMechanical testing was performed on a servo-hydraulic system (Landmark 370, MTS Systems, Eden Prairie, MN, USA).\u0026nbsp;An investigator not involved in fixation performed testing. To apply loading, a proximal segment of a composite radius\u0026nbsp;(Sawbones, Pacific Research Laboratories, Vashon, WA, USA) was secured to the actuator and articulated with the capitellum to simulate 20\u0026deg; of elbow flexion, the position associated with peak radiocapitellar contact forces\u0026nbsp;[10]\u0026nbsp;(Fig. 1). Constructs were cyclically loaded between 0\u0026ndash;75 N at 1 Hz for 500 cycles. Force and displacement were sampled at 100 Hz during cycles 1\u0026ndash;10, 100\u0026ndash;110, and 491\u0026ndash;500.\u0026nbsp;Monotonic load-to-failure testing was then performed at a displacement rate of 0.5 mm/s. Failure was defined as a sudden drop in load during testing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOutcomes and statistical analysis\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePrimary outcome variables were failure load and construct stiffness, evaluated at the beginning and end of cyclic loading. Data normality was assessed with the Shapiro\u0026ndash;Wilk test. \u0026nbsp;Paired comparisons were performed using a two-tailed paired Student\u0026rsquo;s t-test for normally distributed data for normally distributed data or the Wilcoxon signed-rank test for non-normally distributed data). A\u0026nbsp;\u003cem\u003ep\u003c/em\u003e-value of \u0026lt;0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eStiffness during cyclic loading.\u003c/p\u003e\n\u003cp\u003eStiffness increased in both constructs across cycles (Fig. 2). At cycles 1\u0026ndash;10, hybrid fixation demonstrated greater stiffness than PA-only (277.8 \u0026plusmn; 64.6 vs 166.6 \u0026plusmn; 51.0 N/mm; paired \u0026Delta; = 111.2 N/mm; p = 0.036), representing a 67% increase. although stiffness remained greater for hybrid at cycles 100\u0026ndash;110 and 491-500\u0026nbsp;(289.3 \u0026plusmn; 61.8 vs 194.6 \u0026plusmn; 58.2 N/mm and 337.1 \u0026plusmn; 95.6 vs 229.2 \u0026plusmn; 45.3 N/mm, respectively), these later differences did not reach statistical significance.\u003c/p\u003e\n\u003cp\u003eLoad to failure and failure displacement.\u003c/p\u003e\n\u003cp\u003eHybrid constructs withstood a higher failure load than PA-only constructs (253.7 \u0026plusmn; 75.8 vs 151.6 \u0026plusmn; 29.9 N; paired \u0026Delta; = 102.1 N; p = 0.014), a 67% increase. Failure displacement did not differ significantly between groups (1.21 \u0026plusmn; 0.43 vs 1.06 \u0026plusmn; 0.35 mm; p = 0.42).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eCapitellar fractures are challenging to manage because of their complex intra-articular geometry, limited bone stock for purchase, and risk of complications. Headless compression screws are commonly used to resist shear and rotational displacement, yet the optimal screw orientation remains debated\u0026nbsp;[11]. In this paired cadaveric biomechanical study, a hybrid construct one AP and one PA screw demonstrated greater early construct stiffness and a higher load to failure than two PA screws in simulated coronal-shear fractures.\u003c/p\u003e\n\u003cp\u003eDrawbacks of two\u0026nbsp;\u003cstrong\u003eAP\u0026nbsp;\u003c/strong\u003escrews include traversal of the articular surface, which increases the risk of iatrogenic cartilage injury and may allow the fragment to collapse into the posterior cortex [12](Tarallo et al., 2021).In addition, access to the medial capitellum via an AP path is also limited by surrounding soft tissues, making precise placement demanding. Conversely, two\u003cstrong\u003e\u0026nbsp;PA\u003c/strong\u003e screws fixation is constrained by a narrow posterior approach [2], and by the need to obtain secure purchase in fragments with scant subchondral bone while avoiding intra-articular penetration [3,12]. A\u0026nbsp;\u003cstrong\u003ehybrid\u003c/strong\u003e configuration (one AP and one PA screw) facilitates effective compression across the fracture and offers more versatile trajectories.\u003c/p\u003e\n\u003cp\u003eThe hybrid construct showed significantly greater initial stiffness (p = 0.036) and a higher failure load (p = 0.014), supporting the biomechanical premise that opposing compressive vectors improve stability. Combining anteroposterior (AP) and posteroanterior (PA) trajectories may better resist multidirectional shear at the radiocapitellar joint, particularly early after fixation. This added stability could enable earlier range-of-motion exercises to limit postoperative stiffness while maintaining construct integrity until union.\u003c/p\u003e\n\u003cp\u003ePrior biomechanical work suggested PA screws may confer greater stability than AP screws during cyclic loading, although some investigations reported trends without statistical significance [13]. In the present model, hybrid fixation sustained a\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e67% higher failure load\u003c/strong\u003e (\u003cem\u003ep\u003c/em\u003e = 0.014) and exhibited\u0026nbsp;\u003cstrong\u003e67% greater initial stiffness\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e(\u003cem\u003ep\u003c/em\u003e\u003cem\u003e\u0026nbsp;=\u003c/em\u003e 0.036). With continued cycling, stiffness increased in both groups and the\u0026nbsp;\u003cstrong\u003erelative\u003c/strong\u003e hybrid advantage narrowed, but a\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e~47%\u003c/strong\u003e stiffness benefit persisted by the end of testing.\u003c/p\u003e\n\u003cp\u003eThese data suggest that a hybrid screw orientation confers greater \u003cstrong\u003eearly mechanical stability\u003c/strong\u003e, which may limit interfragmentary micromotion and foster conditions favorable for osseous primary healing. The added stability could also permit\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eearlier, supervised elbow mobilization\u003c/strong\u003e\u003cstrong\u003e\u0026mdash;\u003c/strong\u003eimportant because postoperative stiffness is a common complication after capitellar fracture fixation. Previous studies by Puloski et al. and Tarallo et al. have emphasized that immediate postoperative motion is essential in minimizing joint stiffness [12,14].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; At the point of failure, the hybrid fixation configuration tolerated significantly higher loads compared to the PA-only fixation, highlighting its enhanced capacity to withstand physiologic stress and reducing the likelihood of construct failure under normal loading conditions. While headless compression screw fixation has generally demonstrated clinical success, previous studies have noted hardware failure as a potential drawback associated with these implants [3,13,15,16]. Our findings suggest that hybrid screw orientation offers improved resistance to catastrophic failure, which may translate into more durable fixation and reduced risk of hardware-related complications in clinical settings, particularly in active or load-bearing patients.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLimitations\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study has several limitations. First, all specimens came from older donors; although capitellar fractures are common in the elderly, these cadavers may not reflect the bone quality or healing potential of younger patients. Second, our testing used simplified loading that does not reproduce the elbow\u0026rsquo;s complex, multidirectional forces during daily activities. Third, we modeled a Bryan\u0026ndash;Morrey type I coronal-shear pattern, so the findings may not generalize to fractures with greater displacement, comminution, or trochlear extension. Finally, while hybrid fixation demonstrated superior early mechanics, we did not evaluate clinical endpoints (union, function, or complications), clinical studies are therefore necessary to confirm the relevance of these biomechanical results.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this paired cadaveric model, hybrid AP\u0026ndash;PA fixation demonstrated significantly greater early stiffness and higher failure load than two PA screws. These findings support a biomechanical advantage of opposing screw vectors for coronal capitellar fractures; further clinical studies are required to validate translation to patient outcomes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics Approval and Consent to Participate:\u0026nbsp;\u003cbr\u003e\u003c/strong\u003eCadaveric specimens were obtained from de-identified donated bodies through institutional donation programs. Institutional review board approval was not required according to local regulations and institutional policy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of Data and Materials:\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests:\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;No external funding or grants were used for the completion of this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;We acknowledge Logan M. Andryk for assistance in the laboratory and Fadi Shweiki for creating the illustration.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFeras Qawasmi, MD:\u003c/strong\u003e Conceptualization of the study, supervision of cadaveric experiments, manuscript drafting, and final approval of submitted version.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSonia Slusarczyk, MSc:\u003c/strong\u003e Biomechanical testing, data collection, and data analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSteven I. Grindel, PhD:\u003c/strong\u003e Statistical analysis, data interpretation, and critical manuscript review.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHamza Murad, MD:\u003c/strong\u003e Assistance in specimen preparation and fracture modeling.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMei Wang, PhD:\u003c/strong\u003e Data validation, review of biomechanical methods, and manuscript editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMustafa Yassin, MD:\u003c/strong\u003e Support in fixation procedures and methodological guidance\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eLevel of Evidence:\u003c/strong\u003e IV\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePotential Conflicts of Interest and Funding Sources:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo outside funding or grants were used for the completion of this study. None are declared.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003cbr\u003e\u003c/strong\u003eWe acknowledge Logan M. Andryk for help in the laboratory and Fadi Shweiki for creating the illustration.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was conducted on human cadaveric specimens. According to national regulations and institutional policies, ethical approval and Institutional Review Board (IRB) review were not required, as the study did not involve living participants or identifiable human data. All cadaveric specimens were obtained through a legally authorized body donation program, with written informed consent provided prior to death for research and educational purposes. The study was conducted in accordance with the principles of the Declaration of Helsinki.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBallesteros-Betancourt JR, Garc\u0026iacute;a-Tarri\u0026ntilde;o R, Garc\u0026iacute;a-Elvira R, Mu\u0026ntilde;oz-Mahamud E, Fern\u0026aacute;ndez-Valencia JA, Llus\u0026aacute;-P\u0026eacute;rez M, Combalia-Aleu A. The anterior limited approach of the elbow for the treatment of capitellum and trochlea fractures: Surgical technique and clinical experience in eight cases. Injury. 2020 Apr;51 Suppl 1:S103\u0026ndash;11. \u003c/li\u003e\n\u003cli\u003eBAYDAR M, AYKUT S, MERT M, KESKINBI\u0026Ccedil;KI MV, AKDENIZ HE, \u0026Ouml;ZT\u0026Uuml;RK K. ISOLATED CAPITELLAR FRACTURE FIXATION WITH HEADLESS SCREWS IN DIFFERENT CONFIGURATIONS. Acta Ortop Bras. 2022;30(1). \u003c/li\u003e\n\u003cli\u003eBellato E, Giai Via R, Bachman D, Zorzolo I, Marmotti A, Castoldi F. Coronal Shear Fractures of the Distal Humerus. J Funct Morphol Kinesiol. 2022 Jan 6;7(1):7. \u003c/li\u003e\n\u003cli\u003eBilsel K, Atalar AC, Erdil M, Elmadag M, Sen C, Demirhan M. Coronal plane fractures of the distal humerus involving the capitellum and trochlea treated with open reduction internal fixation. Arch Orthop Trauma Surg. 2013 Jun 15;133(6):797\u0026ndash;804. \u003c/li\u003e\n\u003cli\u003eBorbas P, Vetter M, Loucas R, Hofstede S, Wieser K, Ernstbrunner L. Biomechanical stability of simple coronal shear fracture fixation of the capitellum. J Shoulder Elbow Surg. 2021 Aug;30(8):1768\u0026ndash;73. \u003c/li\u003e\n\u003cli\u003eElkowitz SJ, Polatsch DB, Egol KA, Kummer FJ, Koval KJ. Capitellum Fractures: A Biomechanical Evaluation of Three Fixation Methods. J Orthop Trauma. 2002 Aug;16(7):503\u0026ndash;6. \u003c/li\u003e\n\u003cli\u003eKurtulmus T, Saglam N, Saka G, Avci CC, Kucukdurmaz F, Akpinar F. Posterior fixation of type IV humeral capitellum fractures with fully threaded screws in adolescents. European Journal of Trauma and Emergency Surgery. 2014 Jun 26;40(3):379\u0026ndash;85. \u003c/li\u003e\n\u003cli\u003eYu T, Tao H, Xu F, Hu Y, Zhang C, Zhou G. Comparison of lateral approach versus anterolateral approach with Herbert screw fixation for isolated coronal shear fractures of humeral capitellum. J Orthop Surg Res. 2019 Dec 22;14(1):230. \u003c/li\u003e\n\u003cli\u003eJupiter JB, Mehne DK. FRACTURES OF THE DISTAL HUMERUS. Orthopedics. 1992 Jul;15(7):825\u0026ndash;33. \u003c/li\u003e\n\u003cli\u003eKurtulmus T, Saglam N, Saka G, Avci CC, Kucukdurmaz F, Akpinar F. Posterior fixation of type IV humeral capitellum fractures with fully threaded screws in adolescents. European Journal of Trauma and Emergency Surgery. 2014 Jun 26;40(3):379\u0026ndash;85. \u003c/li\u003e\n\u003cli\u003eBorbas P, Loucas R, Loucas M, Vetter M, Hofstede S, Ernstbrunner L, Wieser K. Biomechanical stability of complex coronal plane fracture fixation of the capitellum. Arch Orthop Trauma Surg. 2021 Aug 23;142(11):3239\u0026ndash;46. \u003c/li\u003e\n\u003cli\u003eTarallo L, Novi M, Porcellini G, Giorgini A, Micheloni G, Catani F. Surgical tips and tricks for coronal shear fractures of the elbow. Arch Orthop Trauma Surg. 2021 Feb 3;141(2):261\u0026ndash;70. \u003c/li\u003e\n\u003cli\u003eElkowitz SJ, Kubiak EN, Polatsch D, Cooper J, Kummer FJ, Koval KJ. Comparison of two headless screw designs for fixation of capitellum fractures. Bull Hosp Jt Dis. 2003;61(3\u0026ndash;4):123\u0026ndash;6. \u003c/li\u003e\n\u003cli\u003ePuloski S, Kemp K, Sheps D, Hildebrand K, Donaghy J. Closed Reduction and Early Mobilization in Fractures of the Humeral Capitellum. J Orthop Trauma. 2012 Jan;26(1):62\u0026ndash;5. \u003c/li\u003e\n\u003cli\u003eCheung E V. Fractures of the Capitellum. Hand Clin. 2007 Nov;23(4):481\u0026ndash;6. \u003c/li\u003e\n\u003cli\u003eElkowitz SJ, Polatsch DB, Egol KA, Kummer FJ, Koval KJ. Capitellum Fractures: A Biomechanical Evaluation of Three Fixation Methods. J Orthop Trauma. 2002 Aug;16(7):503\u0026ndash;6. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-orthopaedic-surgery-and-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"josr","sideBox":"Learn more about [Journal of Orthopaedic Surgery and Research](http://josr-online.biomedcentral.com)","snPcode":"13018","submissionUrl":"https://submission.nature.com/new-submission/13018/3","title":"Journal of Orthopaedic Surgery and Research","twitterHandle":"@MSKmedBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Capitellar fracture, Hybrid screw fixation, Headless compression screw, ORIF, Screw orientation, Elbow biomechanics, Cadaveric study","lastPublishedDoi":"10.21203/rs.3.rs-8584608/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8584608/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eOBJECTIVE:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo compare the biomechanical performance of a hybrid headless-screw construct (one anteroposterior [AP] and one posteroanterior [PA]) with a traditional PA-only (two PA screws) construct in a paired cadaveric model of capitellar coronal-shear fractures.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSeven pairs of fresh-frozen cadaveric humeri were used. Simulated Bryan–Morrey type I coronal-shear capitellar fractures were created and fixed with Acutrak cannulated headless compression screws. Each pair received either hybrid fixation (one AP and one PA screw) or two PA screws. Constructs underwent cyclic loading followed by load-to-failure testing. Force and displacement were sampled at 100 Hz during selected cycles (cycles 1–10, 100–110 and 491–500). Data were analyzed using paired statistical tests; a p-value \u0026lt; 0.05 was considered significant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHybrid fixation showed greater initial stiffness than PA-only (277.8 ± 64.6 vs 166.6 ± 51.0 N/mm; \u003cem\u003ep\u003c/em\u003e = 0.036). Although stiffness remained higher with hybrid after further cycling, later differences were not statistically significant. Load-to-failure was higher with hybrid (253.7 ± 75.8 vs 151.6 ± 29.9 N; \u003cem\u003ep\u003c/em\u003e= 0.014). Failure displacement did not differ (1.21 ± 0.43 vs 1.06 ± 0.35 mm; \u003cem\u003ep\u003c/em\u003e= 0.42). Overall, hybrid constructs demonstrated ≈67% greater initial stiffness and ≈67% greater failure load versus PA-only.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this paired cadaveric model of capitellar shear fractures, a hybrid AP–PA screw orientation improved early construct stiffness and increased failure tolerance compared with two PA screws. These biomechanical advantages may support early supervised motion while maintaining construct integrity, however, clinical correlation is required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLEVEL OF EVIDENCE:\u003c/strong\u003e \u003cstrong\u003eIV (cadaveric biomechanical study).\u003c/strong\u003e\u003c/p\u003e","manuscriptTitle":"Title: Hybrid Anteroposterior–Posteroanterior Headless Screw Fixation Improves Biomechanical Stability of Capitellar Coronal Shear Fractures: A Paired Cadaveric Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-06 08:35:56","doi":"10.21203/rs.3.rs-8584608/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2026-04-27T05:40:41+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-02T06:32:47+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-31T05:18:52+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Orthopaedic Surgery and Research","date":"2026-01-28T16:22:49+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-orthopaedic-surgery-and-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"josr","sideBox":"Learn more about [Journal of Orthopaedic Surgery and Research](http://josr-online.biomedcentral.com)","snPcode":"13018","submissionUrl":"https://submission.nature.com/new-submission/13018/3","title":"Journal of Orthopaedic Surgery and Research","twitterHandle":"@MSKmedBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"04b03d2a-44cc-43d8-afdf-2a4e35f907e2","owner":[],"postedDate":"May 6th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-06T08:35:56+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-06 08:35:56","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8584608","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8584608","identity":"rs-8584608","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}