Biomechanical Evaluation of a Medial-Only Fixation Strategy for Takeuchi Type 2 Lateral Hinge Fractures in Medial Open Wedge High Tibial Osteotomy

Biomechanical Evaluation of a Medial-Only Fixation Strategy for Takeuchi Type 2 Lateral Hinge Fractures in Medial Open Wedge High Tibial Osteotomy | 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 Biomechanical Evaluation of a Medial-Only Fixation Strategy for Takeuchi Type 2 Lateral Hinge Fractures in Medial Open Wedge High Tibial Osteotomy Yoshiya Nibe, Tsuneari Takahashi, Tomohiro Matsumura, Kohei Watanabe, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9126445/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background Medial opening wedge high tibial osteotomy (MOWHTO) is a standard treatment for knee osteoarthritis. However, lateral hinge fractures occur in 19–25% of cases, with Type 2 fractures causing significant instability. While lateral plating is recommended, it requires an additional incision. This study investigated whether stabilizing the osteotomy gap using a 4.5 mm cortical screw in the Tomofix plate's oval hole via a medial-only approach could provide sufficient stability for Type 2 hinge fractures. Methods Twelve fresh pig knees underwent MOWHTO with a 6 mm opening. They were divided into two groups: Group I (intact lateral hinge) and Group F (induced Type 2 hinge fracture fixed with a medial 4.5 mm cortical screw in the Tomofix oval hole). Specimens were subjected to 2,000 cycles of axial loading (up to 800 N), representing early postoperative partial weight-bearing conditions. Displacement during cycling, and changes in the anterior gap (AG), posterior gap (PG), and posterior tibial slope (PTS) were measured. Results Group F exhibited significantly greater displacement during cyclic loading compared to Group I (p = 0.0029), indicating clinically relevant construct instability. There were no statistically significant differences between the groups regarding changes in AG (p = 0.15), PG (p = 0.53), or PTS (p = 0.22). Conclusions Fixation with a 4.5 mm cortical screw in the Tomofix oval hole is insufficient to restore stability in MOWHTO complicated by a Type 2 lateral hinge fracture. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Around knee osteotomy is a well-established surgical treatment for knee osteoarthritis. Among various techniques, medial opening wedge high tibial osteotomy (MOWHTO) is the most widely performed [1]. The primary advantages of MOWHTO include the ability to fine-tune alignment intraoperatively and the avoidance of fibular osteotomy, which eliminates the risk of neurological symptoms such as common peroneal nerve palsy [2–3]. The widespread adoption of MOWHTO as a standard procedure can be attributed to the advent of locking plates, exemplified by the Tomofix (Fig. 1 ). Tomofix utilizes a long plate fixed to the tibial shaft with locking screws to provide superior angular stability, leading to better clinical outcomes compared to the previously used Puddu plates [4–5]. Consequently, the use of locking plates with inherent angular stability has become the current gold standard for MOWHTO. A recognized complication of MOWHTO is a lateral hinge fracture, with a reported incidence of 19–25% [6–9]. Takeuchi et al. reported that hinge fractures significantly increase instability at the osteotomy gap [9]. These fractures are classified into Types 1 through 3; while Type 1 maintains relatively good stability at the gap, Types 2 and 3 are characterized by significant instability. Accordingly, it has been suggested that Type 2 fractures require additional lateral plating to enhance fixation [10]. However, from the perspective of soft tissue management, adding a lateral skin incision risks further tissue damage. This has led to a clinical question: is there a way to stabilize the osteotomy gap in the presence of a hinge fracture using only the primary medial approach? It is suggested that for the Tomofix plate, inserting a 4.5 mm cortical screw into the No. 1 oval hole—the compression hole in the shaft—can increase stability by compressing the plate against the tibia. However, we were unable to find clear literature evidence supporting this [11]. Based on this premise, we hypothesized that inserting a 4.5 mm cortical screw into the No. 1 oval hole of the Tomofix using a medial-only approach could provide sufficient stability at the osteotomy gap even in MOWHTO cases complicated by a Type 2 hinge fracture. Therefore, the purpose of this study was to determine whether this fixation method for Type 2 hinge fractures achieves stability comparable to that of a MOWHTO model without a hinge fracture. Methods Study design Animal experiments were performed in a biomechanics laboratory of our institution in accordance with the regulations of the Institution's Animal Care and Use Committee. Ethical approval by the Committee was waived due to the ex vivo nature of this study. Twelve fresh pig knees (age: 6 months; weight range: 180–200 kg, Tokyo Shibaura Zouki, Japan) were used. The experimental models were divided into the following two groups: Group I (n = 6): Standard MOWHTO models fixed with the Tomofix. Group F (n = 6): Models representing a Type 2 hinge fracture, which was intentionally induced and then fixed. In this group, a 4.5 mm cortical screw was inserted into the No. 1 oval hole of the plate shaft, while 5.0 mm locking screws were utilized for all other positions. The plate position was fixed to the medial tibia with a thread direction of the B hole at 10 degrees from the transverse diameter of the tibial plateau, according to a previous study [12–13] (Fig. 2 ). The specimens were thawed at room temperature for at least 24 h before use. MOWHTO surgical procedure All specimens underwent MOWHTO with a 6 mm opening wedge, following the standard surgical protocol [14]. First, a 1.6 mm K-wire was advanced from a point 45 mm distal to the medial joint line toward the fibular head. The wire was driven into the contralateral cortex, with its orientation confirmed by its proximity to the fibular tip. The osteotomy was then performed along the K-wire using an oscillating saw, extending from the posteromedial to the anteromedial tibia. To preserve a lateral hinge, the osteotomy was stopped 5 mm medial to the lateral tibial cortex. Additionally, a biplanar osteotomy was performed by creating a coronal cut through the anterior third of the tibia, including the tibial tubercle, at a 110 degrees angle to the axial plane. The osteotomy was carefully opened using three chisels while applying a distracting force to the distal segment. Once a parallel 6 mm gap was confirmed, a Tomofix plate (DePuy Synthes, Zurich, Switzerland) was positioned to the medial aspect of the proximal tibia. In Group F, a type 2 hinge fracture was intentionally induced before plate fixation. The type 2 hinge fracture was created using an oscillating saw distal to the hinge point according to the Takeuchi classification. The screw insertion sequence for Group F was strictly defined as follows: 5.0 mm locking screws were first inserted into the proximal holes (A, B, and C). A 4.5 mm cortical screw was then inserted distally into the No. 1 oval hole of the plate shaft to achieve compression between the plate and the bone. A 5.0 mm locking screw was inserted into hole D. Finally, the remaining holes (No. 2, 3, and 4) were filled with 5.0 mm locking screws. In both groups, all screws were inserted using drill sleeves to ensure consistent alignment, and no bone graft or substitute was used to fill the osteotomy gap (Fig. 3 ). Biomechanical testing Cyclic loading tests were conducted to evaluate the displacement patterns of the two fixation constructs. Testing was performed along the simulated postoperative mechanical axis of the tibia using a universal testing machine (Tensilon RTG 1310, Orientec Co. Ltd., Tokyo, Japan) equipped with custom-designed grips, following previously established protocols [15–17]. The distal 10 cm of each tibia was removed, and the remaining distal 4 cm was secured using a custom-made jig. Since the medial tibial plateau angle following MOWHTO was approximately 90°, the proximal tibial articular surface was aligned perpendicular to the loading axis macroscopically (Fig. 4 ). Load-displacement curves were recorded using specialized software (Tensilon Advanced Controller for Testing, Orientec Co., Japan) (Fig. 5 a, 5 b). Based on the protocol described by Takeuchi et al. [12], specimens were subjected to 2,000 cycles of axial loading up to 800 N at a frequency of 0.5 Hz. Actuator displacement was recorded at the 10th, 100th, 500th, 1,000th, 1,500th, and 2,000th cycles. No significant macroscopic alterations in specimen alignment were observed after completion of the cyclic loading. To evaluate changes in the sagittal plane, the anterior gap (AG) and posterior gap (PG) at the osteotomy site were measured using a precision caliper (0.1 mm accuracy). To ensure intra- and inter-rater reliability, measurements were taken by two independent researchers and averaged over three trials. The change in the posterior tibial slope (PTS) was calculated based on the difference between the PG and AG, using the average anteroposterior diameter of the proximal tibia (50 mm). Statistical analysis The primary endpoint was the displacement measured during the cyclic loading test. Secondary endpoints included changes in the AG and PG, and the increase in the PTS after the cyclic loading test. All data are presented as mean ± standard deviation. To compare the displacement patterns between the two groups throughout the test, a repeated-measures analysis of variance (ANOVA) followed by Bonferroni post-hoc analysis was employed. For the assessment of changes in the AG, PG, and PTS between the groups, unpaired t-tests were utilized. For all analyses, a p-value of < 0.05 was considered statistically significant. An a priori power analysis was conducted to determine the required sample size. With the significance level (α) set at 0.05, power (1-β) at 0.80, and an effect size of 1.6 based on a pilot study, the minimum required sample size was calculated using G*Power 3.1 (Franz Faul, Kiel University, Kiel, Germany) [18]. All statistical analyses were performed using EZR software [19]. Results Displacement during cyclic loading Repeated-measures ANOVA revealed a significant difference in displacement between the two groups (p = 0.0029). Specifically, Group F exhibited greater displacement compared to Group I throughout the testing cycles. There was also a significant interaction between group and time (p = 0.0011), indicating that the displacement patterns over time differed between the groups (Fig. 6 , Table 1 ). Table 1 The displacement between the two groups Parameters Group I (n = 6) Group F (n = 6) 10th (mm)* 0.79 (0.11) 2.06 (1.10) 100th (mm)* 0.73 (0.054) 2.27 (1.02) 500th (mm)* 0.72 (0.051) 2.38 (0.99) 1000th (mm)* 0.72 (0.051) 2.42 (0.99) 1500th (mm)* 0.73 (0.056) 2.43 (0.98) 2000th (mm)* 0.72 (0.062) 2.42 (0.97) *Data are expressed as mean (standard deviation). **Comparison between Groups by use of repeated-measures analysis of variance. Changes in osteotomy gap and posterior tibial slope Regarding the secondary endpoints, there were no statistically significant differences between the two groups in terms of sagittal plane stability. The mean change in AG was 0.050 ± 0.57 mm in Group F and 0.47 ± 0.33 mm in Group I, with no significant difference between the groups (p = 0.15) (Fig. 7 a). The mean change in PG was 0.22 ± 0.12 mm in Group F and 0.017 ± 0.87 mm in Group I (p = 0.53) (Fig. 7 b). The calculated increase in PTS was 0.19 ± 0.64° in Group F and − 0.55 ± 1.24° in Group I, showing no statistically significant difference (p = 0.22) (Fig. 7 c, Table 2 ). Table 2 The anterior and posterior gap changes and the posterior tibial slope changes between the two groups Parameters Group I (n = 6) Group F (n = 6) P value** The anterior gap changes* 0.47 (0.33) 0.050 (0.57) 0.15 The posterior gap changes* 0.017 (0.87) 0.22 (0.12) 0.53 The posterior tibial slope changes* -0.55 (1.24) 0.19 (0.64) 0.22 *Data are expressed as mean (standard deviation). **Comparison between Groups by use of unpaired t-tests. Discussion Principal findings and clinical implications In this study, we investigated whether using a 4.5 mm cortical screw in the Tomofix plate's oval hole could stabilize a Type 2 lateral hinge fracture during MOWHTO using only a medial approach. Our results showed that while AG, PG, and PTS changes did not differ significantly between groups, Group F exhibited significantly greater displacement during cyclic loading than the intact group. This suggests that medial cortical screw fixation alone is insufficient to restore the stability of a Type 2 hinge fracture to the level of an intact lateral hinge. The lack of significant change in the osteotomy gap and PTS might be attributed to the high structural stiffness of the Tomofix plate, which allows the construct to return to its original position after transient loading. Chen et al. previously reported no significant difference in structural stiffness between hinge fracture types under loads below 800 N [20]. However, the increased displacement observed in our fracture model indicates a lack of osteotomy site stability, which leads to increased subsidence. Continuous loading on such an unstable construct may result in metal fatigue and eventual plate failure. Therefore, additional stabilization is required for Type 2 hinge fractures. Previous literature recommends additional lateral anatomical plating or Cannulated Cancellous Screws when an intraoperative lateral hinge fracture is identified [11, 21]. Biomechanically, lateral plating has been shown to effectively stabilize the osteotomy site in Type 2 fractures. A weakness of MOWHTO is medial instability at the osteotomy site, which can be addressed by filling the medial side with artificial bone and fixating with a long locking plate. However, if a lateral hinge fracture occurs, both the medial and lateral sides become unstable, making it difficult to address with a standard medial plate alone. Therefore, it makes sense that if a lateral hinge fracture is present, the addition of a lateral plate can also address lateral instability. However, from the perspective of soft tissue management, adding a lateral incision is undesirable due to the risk of increased surgical trauma. While this study was born from a clinical question seeking a medial-only solution, our findings suggest that lateral fixation remains necessary for Type 2 hinge fractures at this time. Although we were unable to demonstrate the feasibility of a medial-only approach for these cases, we believe this outcome represents valuable evidence for clinical decision-making rather than merely negative data. Limitations This study has several limitations. First, we used porcine bone models, which may not fully replicate human bone properties, although they are established models for biomechanical MOWHTO studies [13,22,23]. Second, we did not fill the osteotomy gap with artificial bone. This was intended to simulate a "worst-case scenario" characterized by significant medial instability, thereby allowing for a rigorous evaluation of the hardware’s fixation strength alone. Third, we evaluated only structural properties; biological healing processes were not considered. Fourth, displacement was measured only in the axial direction; thus, coronal plane changes such as varus collapse were not quantitatively assessed, although no macroscopic worsening of varus was observed. Finally, the cyclic loading was limited to 2,000 cycles due to mechanical constraints. We expect that further loading would likely lead to construct failure in the hinge fracture models. Conclusions Fixation with a 4.5 mm cortical screw in the Tomofix oval hole failed to provide sufficient stability for Type 2 lateral hinge fractures during MOWHTO. Although sagittal alignment was maintained, the increased displacement suggests a high risk of long-term instability. For Type 2 hinge fractures, additional lateral stabilization is recommended to prevent mechanical complications. Abbreviations AG anterior gap ANOVA analysis of variance MOWHTO medial open wedge high tibial osteotomy PG posterior gap PTS posterior tibial slope Declarations Ethics approval and consent to participate As this study did not involve human participants, human data, or human tissue, the requirements for institutional review board (IRB) approval and informed consent were not applicable. All animal-derived materials used in this study were isolated porcine tibiae obtained from a commercial abattoir (food industry by-products). Ethical approval for the use of these cadaveric specimens was waived by the Medical Ethics Review Committee of Jichi Medical University, in accordance with institutional and national regulations regarding ex vivo research. Consent for publication Not applicable. No identifying information or images of individual participants are included in the manuscript. Availability of data and materials The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare no competing interests. Funding This work was supported by the J&J Medical Research Grant [grant numbers AS2022A000070909]. Authors contributions TT conceived the study idea and supervised the project. YN and TT designed the study. YN and KW collected and curated the data, performed all statistical analyses, prepared the tables and figures, and drafted the manuscript. TM and KT contributed to the interpretation of the data and critically revised the manuscript for important intellectual content. All authors read and approved the final version of the manuscript. Acknowledgements Not applicable. References Rodner CM, Adams DJ, Diaz-Doran V, Tate JP, Santangelo SA, Mazzocca AD, et al. 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Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 06 May, 2026 Reviews received at journal 29 Apr, 2026 Reviews received at journal 23 Apr, 2026 Reviewers agreed at journal 16 Apr, 2026 Reviewers agreed at journal 05 Apr, 2026 Reviewers invited by journal 28 Mar, 2026 Editor assigned by journal 24 Mar, 2026 Submission checks completed at journal 21 Mar, 2026 First submitted to journal 21 Mar, 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. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9126445","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":613781976,"identity":"6d6c1710-5496-4fc2-922d-e81c11337fa7","order_by":0,"name":"Yoshiya Nibe","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9klEQVRIie3SMWrDMBTG8c8InOUVrwoZeoKCTCAE0pKrWAScrQS6F5VAuhiy6hiBQmeZB86SA3R0KXQuZMmQoU7TrLLHQvWfJMEP6YGAUOgvJpIvPh6ABKURUD9nmZ/0TFpfFUDfdCbkhopiQLnmxk7vurFZLiXx/bDkp/1igevE4LP2kdFbVkk15oeRK5cDq5Bah7nyE72SGbF+deVKkEK0AXLpJ7NYupj1izmTaTvZVSI1DdngTHQ72RbRR1TMtT3NQkrOLLfNwgTGYaLXdvu+p+Pt3fq5yGsf+W0JSHdaNE8SlHcQeGx+jLlselUXEgqFQv+nb3oOTkqYRe6hAAAAAElFTkSuQmCC","orcid":"","institution":"Jichi Medical University","correspondingAuthor":true,"prefix":"","firstName":"Yoshiya","middleName":"","lastName":"Nibe","suffix":""},{"id":613781981,"identity":"835ad806-608f-4cd2-9286-25a38805bd27","order_by":1,"name":"Tsuneari Takahashi","email":"","orcid":"","institution":"Jichi Medical University","correspondingAuthor":false,"prefix":"","firstName":"Tsuneari","middleName":"","lastName":"Takahashi","suffix":""},{"id":613781982,"identity":"61e6c9a0-35eb-4033-a3e7-90386ac0e080","order_by":2,"name":"Tomohiro Matsumura","email":"","orcid":"","institution":"Jichi Medical University","correspondingAuthor":false,"prefix":"","firstName":"Tomohiro","middleName":"","lastName":"Matsumura","suffix":""},{"id":613781987,"identity":"acb594fe-938d-43f9-82e3-d78804d1aa1d","order_by":3,"name":"Kohei Watanabe","email":"","orcid":"","institution":"Jichi Medical University","correspondingAuthor":false,"prefix":"","firstName":"Kohei","middleName":"","lastName":"Watanabe","suffix":""},{"id":613781991,"identity":"4b55f8eb-0994-4636-adcf-b79894507e39","order_by":4,"name":"Katsushi Takeshita","email":"","orcid":"","institution":"Jichi Medical University","correspondingAuthor":false,"prefix":"","firstName":"Katsushi","middleName":"","lastName":"Takeshita","suffix":""}],"badges":[],"createdAt":"2026-03-15 05:53:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9126445/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9126445/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106071882,"identity":"9efd09a8-73df-478c-9016-b68a099edbef","added_by":"auto","created_at":"2026-04-03 06:44:28","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":379794,"visible":true,"origin":"","legend":"\u003cp\u003eTOMOFIX (DePuySynthes, Zuchwil, Switzerland)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9126445/v1/2df0e84519aa52711c077ce4.png"},{"id":106094809,"identity":"e9a1c2c9-92ba-4b95-a276-3a3f8e55ceb5","added_by":"auto","created_at":"2026-04-03 11:43:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":370452,"visible":true,"origin":"","legend":"\u003cp\u003ePlate position (right tibia). Medial plate position (white arrow) is 10° from the transverse diameter of the tibial plateau (dotted line)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9126445/v1/d068b676e8ca085f4979465b.png"},{"id":106094404,"identity":"5fcfa864-3cac-4f33-8cc1-c22ef128f11f","added_by":"auto","created_at":"2026-04-03 11:42:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":821260,"visible":true,"origin":"","legend":"\u003cp\u003eSpecimen preparation of MOWHTO hinge model (left knee). a: medial side, b: lateral side\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9126445/v1/150cb0d23377b797e3414d2d.png"},{"id":106071888,"identity":"44a2b2b7-9fa5-48ba-8a2c-4ba71256fc14","added_by":"auto","created_at":"2026-04-03 06:44:28","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":627616,"visible":true,"origin":"","legend":"\u003cp\u003eSpecimen preparation of hinge fracture model (left knee). The specimen after the MOWHTO hinge model was mounted into the special testing machine. The axial load was applied to the tibia of the medial component. The axial load was 800 N, and 2000 cycles were applied\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9126445/v1/185fafb96031023825adc0f5.png"},{"id":106071885,"identity":"ce6a68d5-2004-4bdb-9675-6d23e54d8bfc","added_by":"auto","created_at":"2026-04-03 06:44:28","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":262598,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic image of the load-displacement curve generated during cyclic testing with this software. a: The load-displacement curve of MOWHTO generated during cyclic testing with this software. b: The load-displacement curve of MOWHTO hinge fracture model generated during cyclic testing with this software. MOWHTO: medial open wedge high tibial osteotomy\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9126445/v1/b854dc21b138f2e1646abc2a.png"},{"id":106094522,"identity":"31e9f8d3-1d4a-48a0-adb8-fbf0f4a1e1ef","added_by":"auto","created_at":"2026-04-03 11:42:49","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":40496,"visible":true,"origin":"","legend":"\u003cp\u003eResult of the displacement between Group I and Group F\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-9126445/v1/63edd7db14d7d79b50ae4d29.png"},{"id":106071887,"identity":"f1e5c561-e9af-43c4-84d4-3cbdb6e2843a","added_by":"auto","created_at":"2026-04-03 06:44:28","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":49115,"visible":true,"origin":"","legend":"\u003cp\u003eResults of anterior and posterior gap changes, and increased posterior tibial slope between Group I and Group F. a: Anterior gap changes, b: Posterior gap changes, c: Increased posterior tibial slope\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-9126445/v1/98323d46f168a4237e71c349.png"},{"id":106402086,"identity":"01fb82c6-d9ae-4918-b1d5-0bb26dcb684d","added_by":"auto","created_at":"2026-04-08 09:10:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3870782,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9126445/v1/b7862880-276c-4ca7-a61a-d9d7a43e1475.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Biomechanical Evaluation of a Medial-Only Fixation Strategy for Takeuchi Type 2 Lateral Hinge Fractures in Medial Open Wedge High Tibial Osteotomy","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAround knee osteotomy is a well-established surgical treatment for knee osteoarthritis. Among various techniques, medial opening wedge high tibial osteotomy (MOWHTO) is the most widely performed [1]. The primary advantages of MOWHTO include the ability to fine-tune alignment intraoperatively and the avoidance of fibular osteotomy, which eliminates the risk of neurological symptoms such as common peroneal nerve palsy [2\u0026ndash;3]. The widespread adoption of MOWHTO as a standard procedure can be attributed to the advent of locking plates, exemplified by the Tomofix (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Tomofix utilizes a long plate fixed to the tibial shaft with locking screws to provide superior angular stability, leading to better clinical outcomes compared to the previously used Puddu plates [4\u0026ndash;5]. Consequently, the use of locking plates with inherent angular stability has become the current gold standard for MOWHTO. A recognized complication of MOWHTO is a lateral hinge fracture, with a reported incidence of 19\u0026ndash;25% [6\u0026ndash;9]. Takeuchi et al. reported that hinge fractures significantly increase instability at the osteotomy gap [9]. These fractures are classified into Types 1 through 3; while Type 1 maintains relatively good stability at the gap, Types 2 and 3 are characterized by significant instability. Accordingly, it has been suggested that Type 2 fractures require additional lateral plating to enhance fixation [10]. However, from the perspective of soft tissue management, adding a lateral skin incision risks further tissue damage. This has led to a clinical question: is there a way to stabilize the osteotomy gap in the presence of a hinge fracture using only the primary medial approach? It is suggested that for the Tomofix plate, inserting a 4.5 mm cortical screw into the No. 1 oval hole\u0026mdash;the compression hole in the shaft\u0026mdash;can increase stability by compressing the plate against the tibia. However, we were unable to find clear literature evidence supporting this [11]. Based on this premise, we hypothesized that inserting a 4.5 mm cortical screw into the No. 1 oval hole of the Tomofix using a medial-only approach could provide sufficient stability at the osteotomy gap even in MOWHTO cases complicated by a Type 2 hinge fracture. Therefore, the purpose of this study was to determine whether this fixation method for Type 2 hinge fractures achieves stability comparable to that of a MOWHTO model without a hinge fracture.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design\u003c/h2\u003e \u003cp\u003eAnimal experiments were performed in a biomechanics laboratory of our institution in accordance with the regulations of the Institution's Animal Care and Use Committee. Ethical approval by the Committee was waived due to the ex vivo nature of this study. Twelve fresh pig knees (age: 6 months; weight range: 180\u0026ndash;200 kg, Tokyo Shibaura Zouki, Japan) were used. The experimental models were divided into the following two groups:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eGroup I (n\u0026thinsp;=\u0026thinsp;6): Standard MOWHTO models fixed with the Tomofix.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eGroup F (n\u0026thinsp;=\u0026thinsp;6): Models representing a Type 2 hinge fracture, which was intentionally induced and then fixed. In this group, a 4.5 mm cortical screw was inserted into the No. 1 oval hole of the plate shaft, while 5.0 mm locking screws were utilized for all other positions.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThe plate position was fixed to the medial tibia with a thread direction of the B hole at 10 degrees from the transverse diameter of the tibial plateau, according to a previous study [12\u0026ndash;13] (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The specimens were thawed at room temperature for at least 24 h before use.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMOWHTO surgical procedure\u003c/h3\u003e\n\u003cp\u003eAll specimens underwent MOWHTO with a 6 mm opening wedge, following the standard surgical protocol [14]. First, a 1.6 mm K-wire was advanced from a point 45 mm distal to the medial joint line toward the fibular head. The wire was driven into the contralateral cortex, with its orientation confirmed by its proximity to the fibular tip. The osteotomy was then performed along the K-wire using an oscillating saw, extending from the posteromedial to the anteromedial tibia. To preserve a lateral hinge, the osteotomy was stopped 5 mm medial to the lateral tibial cortex. Additionally, a biplanar osteotomy was performed by creating a coronal cut through the anterior third of the tibia, including the tibial tubercle, at a 110 degrees angle to the axial plane. The osteotomy was carefully opened using three chisels while applying a distracting force to the distal segment. Once a parallel 6 mm gap was confirmed, a Tomofix plate (DePuy Synthes, Zurich, Switzerland) was positioned to the medial aspect of the proximal tibia.\u003c/p\u003e \u003cp\u003eIn Group F, a type 2 hinge fracture was intentionally induced before plate fixation. The type 2 hinge fracture was created using an oscillating saw distal to the hinge point according to the Takeuchi classification. The screw insertion sequence for Group F was strictly defined as follows:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e5.0 mm locking screws were first inserted into the proximal holes (A, B, and C).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eA 4.5 mm cortical screw was then inserted distally into the No. 1 oval hole of the plate shaft to achieve compression between the plate and the bone.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eA 5.0 mm locking screw was inserted into hole D.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eFinally, the remaining holes (No. 2, 3, and 4) were filled with 5.0 mm locking screws.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eIn both groups, all screws were inserted using drill sleeves to ensure consistent alignment, and no bone graft or substitute was used to fill the osteotomy gap (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eBiomechanical testing\u003c/h3\u003e\n\u003cp\u003eCyclic loading tests were conducted to evaluate the displacement patterns of the two fixation constructs. Testing was performed along the simulated postoperative mechanical axis of the tibia using a universal testing machine (Tensilon RTG 1310, Orientec Co. Ltd., Tokyo, Japan) equipped with custom-designed grips, following previously established protocols [15\u0026ndash;17]. The distal 10 cm of each tibia was removed, and the remaining distal 4 cm was secured using a custom-made jig. Since the medial tibial plateau angle following MOWHTO was approximately 90\u0026deg;, the proximal tibial articular surface was aligned perpendicular to the loading axis macroscopically (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Load-displacement curves were recorded using specialized software (Tensilon Advanced Controller for Testing, Orientec Co., Japan) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). Based on the protocol described by Takeuchi et al. [12], specimens were subjected to 2,000 cycles of axial loading up to 800 N at a frequency of 0.5 Hz. Actuator displacement was recorded at the 10th, 100th, 500th, 1,000th, 1,500th, and 2,000th cycles. No significant macroscopic alterations in specimen alignment were observed after completion of the cyclic loading. To evaluate changes in the sagittal plane, the anterior gap (AG) and posterior gap (PG) at the osteotomy site were measured using a precision caliper (0.1 mm accuracy). To ensure intra- and inter-rater reliability, measurements were taken by two independent researchers and averaged over three trials. The change in the posterior tibial slope (PTS) was calculated based on the difference between the PG and AG, using the average anteroposterior diameter of the proximal tibia (50 mm).\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eThe primary endpoint was the displacement measured during the cyclic loading test. Secondary endpoints included changes in the AG and PG, and the increase in the PTS after the cyclic loading test. All data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. To compare the displacement patterns between the two groups throughout the test, a repeated-measures analysis of variance (ANOVA) followed by Bonferroni post-hoc analysis was employed. For the assessment of changes in the AG, PG, and PTS between the groups, unpaired t-tests were utilized. For all analyses, a p-value of \u0026lt;\u0026thinsp;0.05 was considered statistically significant. An a priori power analysis was conducted to determine the required sample size. With the significance level (α) set at 0.05, power (1-β) at 0.80, and an effect size of 1.6 based on a pilot study, the minimum required sample size was calculated using G*Power 3.1 (Franz Faul, Kiel University, Kiel, Germany) [18]. All statistical analyses were performed using EZR software [19].\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eDisplacement during cyclic loading\u003c/h2\u003e \u003cp\u003eRepeated-measures ANOVA revealed a significant difference in displacement between the two groups (p\u0026thinsp;=\u0026thinsp;0.0029). Specifically, Group F exhibited greater displacement compared to Group I throughout the testing cycles. There was also a significant interaction between group and time (p\u0026thinsp;=\u0026thinsp;0.0011), indicating that the displacement patterns over time differed between the groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe displacement between the two groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroup I\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;6)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGroup F\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;6)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003e10th (mm)*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.79 (0.11)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.06 (1.10)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003e100th (mm)*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.73 (0.054)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.27 (1.02)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003e500th (mm)*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.72 (0.051)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.38 (0.99)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003e1000th (mm)*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.72 (0.051)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.42 (0.99)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003e1500th (mm)*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.73 (0.056)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.43 (0.98)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e2000th (mm)*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.72 (0.062)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.42 (0.97)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c5\" namest=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e*Data are expressed as mean (standard deviation).\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e**Comparison between Groups by use of repeated-measures analysis of variance.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eChanges in osteotomy gap and posterior tibial slope\u003c/h3\u003e\n\u003cp\u003eRegarding the secondary endpoints, there were no statistically significant differences between the two groups in terms of sagittal plane stability. The mean change in AG was 0.050\u0026thinsp;\u0026plusmn;\u0026thinsp;0.57 mm in Group F and 0.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.33 mm in Group I, with no significant difference between the groups (p\u0026thinsp;=\u0026thinsp;0.15) (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ea). The mean change in PG was 0.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 mm in Group F and 0.017\u0026thinsp;\u0026plusmn;\u0026thinsp;0.87 mm in Group I (p\u0026thinsp;=\u0026thinsp;0.53) (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). The calculated increase in PTS was 0.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64\u0026deg; in Group F and \u0026minus;\u0026thinsp;0.55\u0026thinsp;\u0026plusmn;\u0026thinsp;1.24\u0026deg; in Group I, showing no statistically significant difference (p\u0026thinsp;=\u0026thinsp;0.22) (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ec, Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe anterior and posterior gap changes and the posterior tibial slope changes between the two groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup I\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;6)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroup F\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;6)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value**\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eThe anterior gap changes*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.47 (0.33)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.050 (0.57)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eThe posterior gap changes*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.017 (0.87)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.22 (0.12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eThe posterior tibial slope changes*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.55 (1.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.19 (0.64)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e*Data are expressed as mean (standard deviation).\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e**Comparison between Groups by use of unpaired t-tests.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003ePrincipal findings and clinical implications\u003c/h2\u003e \u003cp\u003eIn this study, we investigated whether using a 4.5 mm cortical screw in the Tomofix plate's oval hole could stabilize a Type 2 lateral hinge fracture during MOWHTO using only a medial approach. Our results showed that while AG, PG, and PTS changes did not differ significantly between groups, Group F exhibited significantly greater displacement during cyclic loading than the intact group. This suggests that medial cortical screw fixation alone is insufficient to restore the stability of a Type 2 hinge fracture to the level of an intact lateral hinge.\u003c/p\u003e \u003cp\u003eThe lack of significant change in the osteotomy gap and PTS might be attributed to the high structural stiffness of the Tomofix plate, which allows the construct to return to its original position after transient loading. Chen et al. previously reported no significant difference in structural stiffness between hinge fracture types under loads below 800 N [20]. However, the increased displacement observed in our fracture model indicates a lack of osteotomy site stability, which leads to increased subsidence. Continuous loading on such an unstable construct may result in metal fatigue and eventual plate failure. Therefore, additional stabilization is required for Type 2 hinge fractures.\u003c/p\u003e \u003cp\u003ePrevious literature recommends additional lateral anatomical plating or Cannulated Cancellous Screws when an intraoperative lateral hinge fracture is identified [11, 21]. Biomechanically, lateral plating has been shown to effectively stabilize the osteotomy site in Type 2 fractures. A weakness of MOWHTO is medial instability at the osteotomy site, which can be addressed by filling the medial side with artificial bone and fixating with a long locking plate. However, if a lateral hinge fracture occurs, both the medial and lateral sides become unstable, making it difficult to address with a standard medial plate alone. Therefore, it makes sense that if a lateral hinge fracture is present, the addition of a lateral plate can also address lateral instability. However, from the perspective of soft tissue management, adding a lateral incision is undesirable due to the risk of increased surgical trauma. While this study was born from a clinical question seeking a medial-only solution, our findings suggest that lateral fixation remains necessary for Type 2 hinge fractures at this time. Although we were unable to demonstrate the feasibility of a medial-only approach for these cases, we believe this outcome represents valuable evidence for clinical decision-making rather than merely negative data.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eThis study has several limitations. First, we used porcine bone models, which may not fully replicate human bone properties, although they are established models for biomechanical MOWHTO studies [13,22,23]. Second, we did not fill the osteotomy gap with artificial bone. This was intended to simulate a \"worst-case scenario\" characterized by significant medial instability, thereby allowing for a rigorous evaluation of the hardware\u0026rsquo;s fixation strength alone. Third, we evaluated only structural properties; biological healing processes were not considered. Fourth, displacement was measured only in the axial direction; thus, coronal plane changes such as varus collapse were not quantitatively assessed, although no macroscopic worsening of varus was observed. Finally, the cyclic loading was limited to 2,000 cycles due to mechanical constraints. We expect that further loading would likely lead to construct failure in the hinge fracture models.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eFixation with a 4.5 mm cortical screw in the Tomofix oval hole failed to provide sufficient stability for Type 2 lateral hinge fractures during MOWHTO. Although sagittal alignment was maintained, the increased displacement suggests a high risk of long-term instability. For Type 2 hinge fractures, additional lateral stabilization is recommended to prevent mechanical complications.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eAG\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eanterior gap\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eANOVA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eanalysis of variance\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMOWHTO\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003emedial open wedge high tibial osteotomy\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePG\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eposterior gap\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePTS\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eposterior tibial slope\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs this study did not involve human participants, human data, or human tissue, the requirements for institutional review board (IRB) approval and informed consent were not applicable. All animal-derived materials used in this study were isolated porcine tibiae obtained from a commercial abattoir (food industry by-products). Ethical approval for the use of these cadaveric specimens was waived by the Medical Ethics Review Committee of Jichi Medical University, in accordance with institutional and national regulations regarding ex vivo research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable. No identifying information or images of individual participants are included in the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the J\u0026amp;J Medical Research Grant [grant numbers AS2022A000070909].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTT conceived the study idea and supervised the project. YN and TT designed the study. YN and KW collected and curated the data, performed all statistical analyses, prepared the tables and figures, and drafted the manuscript. TM and KT contributed to the interpretation of the data and critically revised the manuscript for important intellectual content. All authors read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eRodner CM, Adams DJ, Diaz-Doran V, Tate JP, Santangelo SA, Mazzocca AD, et al. Medial opening wedge tibial osteotomy and the sagittal plane: the effect of increasing tibial slope on tibiofemoral contact pressure. \u003cem\u003eAm J Sports Med. 2006,\u003c/em\u003e 34(9):1431-41.\u003c/li\u003e\n \u003cli\u003eMaas S, Diffo Kaze A, Dueck K, Pape D. Static and dynamic differences in fixation stability between a spacer plate and a small stature plate fixator used for high tibial osteotomies: A biomechanical bone composite study. \u003cem\u003eISRN Orthop\u003c/em\u003e. 2013, 387620.\u003c/li\u003e\n \u003cli\u003eSmith JO, Wilson AJ, Thomas NP. Osteotomy around the knee: evolution, principles and results. \u003cem\u003eKnee Surg Sports Traumatol Arthrosc\u003c/em\u003e. 2013, 21(1):3-22.\u003c/li\u003e\n \u003cli\u003eStoffel K, Stachowiak G, Kuster M. Open wedge high tibial osteotomy: biomechanical investigation of the modified Arthrex osteotomy plate (Puddu Plate) and the TomoFix plate. \u003cem\u003eClin Biomech (Bristol). 2004,19(9):\u003c/em\u003e944\u0026ndash;50.\u003c/li\u003e\n \u003cli\u003eZhim F, Laflamme GY, Viens H, Laflamme GH, Yahia L. Biomechanical Stability of a Retrotubercle Opening-Wedge High Tibial Osteotomy. \u003cem\u003eJ Knee Surg.\u003c/em\u003e 2006,19(1):28\u0026ndash;32.\u003c/li\u003e\n \u003cli\u003eNakamura R, Komatsu N, Murao T, Okamot Y, Nakamura S, Fujita K, et al. The validity of the classification for lateral hinge fractures in open wedge high tibial osteotomy. \u003cem\u003eBone Joint J\u003c/em\u003e. 2015,97-B(9):1226\u0026ndash;31.\u003c/li\u003e\n \u003cli\u003eNakamura R, Komatsu N, Fujita K, Kuroda K, Takahashi M, Omi R, et al. Appropriate hinge position for prevention of unstable lateral hinge fracture in open wedge high tibial osteotomy. \u003cem\u003eBone Joint J\u003c/em\u003e. 2017,99-B(10):1313\u0026ndash;18.\u003c/li\u003e\n \u003cli\u003eGoshima K, Sawaguchi T, Shigemoto K, Iwai S, Nakanishi A, Inoue D, et al. Large opening gaps, unstable hinge fractures, and osteotomy line below the safe zone cause delayed bone healing after open-wedge high tibial osteotomy. \u003cem\u003eKnee Surg Sports Traumatol Arthrosc.\u003c/em\u003e 2019,27(4):1291\u0026ndash;98.\u003c/li\u003e\n \u003cli\u003eTakeuchi R, Ishikawa H, Kumagai K, Yamaguchi Y, Chiba N, Akamatsu Y, et al. Fractures around the lateral cortical hinge after a medial opening-wedge high tibial osteotomy: A new classification of lateral hinge fracture. \u003cem\u003eArthroscopy.\u003c/em\u003e 2012,28(1):85\u0026ndash;94.\u003c/li\u003e\n \u003cli\u003ePeez C, Deichsel A, Zderic I, Richards RG, Drenchev L, Skulev HK, et al. Fixation of Takeuchi type II/III lateral hinge fractures provides favourable stability of a medial open wedge high tibial osteotomy\u0026mdash;A biomechanical study」. \u003cem\u003eKnee Surg Sports Traumatol Arthrosc.\u003c/em\u003e 2025,33(4):1428\u0026ndash;42.\u003c/li\u003e\n \u003cli\u003eFranulic N, Mu\u0026ntilde;oz JT, Figueroa F, Innocenti P, Gaggero N. Lateral Hinge Fracture in Medial Opening Wedge High Tibial Osteotomy: A Narrative Review. \u003cem\u003eEFORT Open Rev. 2023,8(7)\u003c/em\u003e:572\u0026ndash;580.\u003c/li\u003e\n \u003cli\u003eTakeuchi R, Woon-Hwa J, Ishikawa H, Yamaguchi Y, Osawa K, Akamatsu Y, et al. Primary stability of different plate positions and the role of bone substitute in open wedge high tibial osteotomy. \u003cem\u003eKnee.\u003c/em\u003e 2017,24(6):1299\u0026ndash;306.\u003c/li\u003e\n \u003cli\u003eNibe Y, Takahashi T, Kubo T, Matsumura T, Takeshita K. Effect of plate position on tibial displacement and posterior tibial slope after cyclic loading in medial open wedge high tibial osteotomy: A biomechanical study using porcine tibia. \u003cem\u003eClin Biomech\u003c/em\u003e (Bristol). 2023,109:106076.\u003c/li\u003e\n \u003cli\u003eTakahashi T, Handa M, Kimura Y, Takeshita K. Intraoperative laximetry-based selective transtibial anterior cruciate ligament reconstruction concomitant with medial open wedge high tibial osteotomy for treating varus knee osteoarthritis with anterior cruciate ligament deficiency. \u003cem\u003eArthrosc Tech.\u003c/em\u003e 2022,11(6): e959\u0026ndash;63.\u003c/li\u003e\n \u003cli\u003eMatsumura T, Takahashi T, Ae R, Takeshita K. Biomechanical comparisons of trochanteric hip fracture fixation using short-, mid-, and long-length proximal femoral nails. \u003cem\u003eGeriatr Orthop Surg Rehabil.\u003c/em\u003e 2022,13:21514593221111350.\u003c/li\u003e\n \u003cli\u003eAndo J, Takahashi T, Matsumura T, Nibe Y, Takeshita K. Biomechanical comparisons of plate placement for medial tibial plateau fractures (Schatzker type IV): A biomechanical study using porcine tibias. \u003cem\u003eInjury.\u003c/em\u003e 2024,55(6):111158.\u003c/li\u003e\n \u003cli\u003eHiyama S, Takahashi T, Ando J, Nibe Y, Matsumura T, Takeshita K. Impact of screw reinsertion on osteosynthesis stability in Schatzker IV tibial plateau fractures: A biomechanical study. \u003cem\u003eSICOT-J.\u003c/em\u003e 2025,11:11.\u003c/li\u003e\n \u003cli\u003eFaul F, Erdfelder E, Lang AG, Buchner A. G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences. \u003cem\u003eBehav Res Methods.\u003c/em\u003e 2007,39(2):175-91.\u003c/li\u003e\n \u003cli\u003eKanda Y. Investigation of the freely available easy-to-use software \u0026lsquo;EZR\u0026rsquo; for medical statistics. \u003cem\u003eBone Marrow Transplan.\u003c/em\u003e 2013,48(3):452\u0026ndash;58.\u003c/li\u003e\n \u003cli\u003eChen P, Zhan Y, Zhan S, Li R, Luo C, Xie X. Biomechanical evaluation of different types of lateral hinge fractures in medial opening wedge high tibial osteotomy. \u003cem\u003eClin Biomech (Bristol).\u003c/em\u003e 2021: 105295.\u003c/li\u003e\n \u003cli\u003eChen YN, Chuang CH, Yang TH, Chang CW, Li CT, Chang CJ, et al. Computational comparison of different plating strategies in medial open-wedge high tibial osteotomy with lateral hinge fractures. \u003cem\u003eJ Orthop Surg Res.\u003c/em\u003e 2020,15(1):409.\u003c/li\u003e\n \u003cli\u003eNibe Y, Takahashi T, Matsumura T, Kubo T, Takeshita K. Effect of plate design on maintenance of anterior and posterior gaps and posterior tibial slope after cyclic loading in medial open‐wedge high tibial osteotomy: A biomechanical study using porcine\u0026rsquo;s tibia. \u003cem\u003eJ Exp Orthop.\u003c/em\u003e 2024,11(3):e12036.\u003c/li\u003e\n \u003cli\u003eNibe Y, Takahashi T, Hai H, Matsumura T, Takeshita K. Comparative biomechanical analysis of tibial posterior slope in medial open wedge high tibial osteotomy vs. distal tuberosity osteotomy with and without anterior-posterior screw: a study using porcine tibia. \u003cem\u003eSICOT J.\u003c/em\u003e 2024,10:41.\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":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9126445/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9126445/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eMedial opening wedge high tibial osteotomy (MOWHTO) is a standard treatment for knee osteoarthritis. However, lateral hinge fractures occur in 19\u0026ndash;25% of cases, with Type 2 fractures causing significant instability. While lateral plating is recommended, it requires an additional incision. This study investigated whether stabilizing the osteotomy gap using a 4.5 mm cortical screw in the Tomofix plate's oval hole via a medial-only approach could provide sufficient stability for Type 2 hinge fractures.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eTwelve fresh pig knees underwent MOWHTO with a 6 mm opening. They were divided into two groups: Group I (intact lateral hinge) and Group F (induced Type 2 hinge fracture fixed with a medial 4.5 mm cortical screw in the Tomofix oval hole). Specimens were subjected to 2,000 cycles of axial loading (up to 800 N), representing early postoperative partial weight-bearing conditions. Displacement during cycling, and changes in the anterior gap (AG), posterior gap (PG), and posterior tibial slope (PTS) were measured.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eGroup F exhibited significantly greater displacement during cyclic loading compared to Group I (p\u0026thinsp;=\u0026thinsp;0.0029), indicating clinically relevant construct instability. There were no statistically significant differences between the groups regarding changes in AG (p\u0026thinsp;=\u0026thinsp;0.15), PG (p\u0026thinsp;=\u0026thinsp;0.53), or PTS (p\u0026thinsp;=\u0026thinsp;0.22).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eFixation with a 4.5 mm cortical screw in the Tomofix oval hole is insufficient to restore stability in MOWHTO complicated by a Type 2 lateral hinge fracture.\u003c/p\u003e","manuscriptTitle":"Biomechanical Evaluation of a Medial-Only Fixation Strategy for Takeuchi Type 2 Lateral Hinge Fractures in Medial Open Wedge High Tibial Osteotomy","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-03 06:44:20","doi":"10.21203/rs.3.rs-9126445/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-06T10:51:34+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-29T12:44:22+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-23T08:32:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"61154734390009112705956335496589094989","date":"2026-04-16T12:49:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"172552665167491989463533904179223266142","date":"2026-04-05T21:43:41+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-28T13:49:11+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-24T15:27:25+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-21T13:07:13+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2026-03-21T13:03:02+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e722f88d-a1be-4fa7-9ac7-d84821591012","owner":[],"postedDate":"April 3rd, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-06T10:51:34+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-13T10:26:28+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-03 06:44:20","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9126445","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9126445","identity":"rs-9126445","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}