Dynamic hip screw fixation of subtrochanteric femoral fractures.

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Abstract

[Indexed for MEDLINE] Conflict of interest statement: The authors declare that they have no conflict of interest. The authors have no relevant financial or non-financial interests to disclose. 20. Orthop Surg. 2025 Sep;17(9):2726-2734. doi: 10.1111/os.70137. Epub 2025 Jul 31. Establishment of Subtrochanteric Fracture in Pre-Clinical Animal Model. Palanisamy P(1), Chow SK(2)(3), Li S(1), Li MM(2), Cheung WH(2), Qin L(2), Zheng YP(1)(4). Author information: (1)Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, SAR, China. (2)Musculoskeletal Research Laboratory, Department of Orthopaedics and Traumatology, Hong Kong Special Administrative Region, The Chinese University of Hong Kong, Hong Kong, SAR, China. (3)Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA. (4)Research Institute for Smart Ageing, The Hong Kong Polytechnic University, Hong Kong, SAR, China. OBJECTIVE: About 7%-34% of the femur fracture contributes to subtrochanteric fracture, and only very little research is available about these fractures when compared to common hip fractures. Hence, the aim of this study was to develop a clinically relevant and reproducible open fracture model in rabbits at the subtrochanteric region to understand the fracture healing mechanism at this site and to explore treatment effects of biophysical intervention in future studies. METHODS: An open osteotomy was created in 32 adult New Zealand white rabbits at the subtrochanteric region, followed by customized titanium internal fixations. The internal fixator consists of a 3D printed titanium compression plate with cortical screws for locking. The fracture healing was monitored for 6 weeks, and the corresponding radiography, MicroCT, and histomorphometry analysis were performed at regular intervals. RESULTS: Four rabbits were excluded due to complications (4/32), including bone dislocation one week post-surgery (3/32). Fracture healing progression was observed in radiographic images. MicroCT analysis showed increased callus volume after 42 days. Histomorphometry revealed remodeled bone area with a higher number of osteocyte cells. CONCLUSION: The rabbit fracture model of an open femoral osteotomy at the subtrochanteric region has been successfully established, with the facilitation of an internal fixator consisting of a 3D printed titanium compression plate with cortical screws for locking. Applications of this model are being investigated, including different biophysical stimulation methods for accelerating fracture healing. © 2025 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd. DOI: 10.1111/os.70137 PMCID: PMC12404857