• Yang Liu, Zhiyuan Ren, Huifeng Shao, Xueding Wang, Yongsheng Ma, Wenjie Song, Xiaogang Wu, Xiangyu Zhang, Pengcui Li, Yong He, Xiaochun Wei, and Wangping Duan.
• Department of Orthopaedics, Second Hospital of Shanxi Medical University, Shanxi Key Laboratory of Bone and Soft Tissue Injury Repair, Taiyuan, 030001, China.
• Injury. 2023 Aug 1; 54 (8): 110841110841.

BackgroundOur previous studies have demonstrated the mechanical effect of sclerosis around screw paths on the healing of femoral neck fractures (FNF) after internal fixation. Furthermore, we discussed the possibility of using bioceramic nails (BNs) to prevent sclerosis. However, all these studies were conducted under static conditions as the patient was standing on one leg, while the effect of the stress generated during movement is unknown. The purpose of this study was to evaluate the stress and displacement under dynamic stress loading conditions.MethodsTwo types of internal fixation, namely cannulated screws and bioceramic nails, were utilized in conjunction with various finite element models of the femur. These models included the femoral neck fracture healing model, the femoral neck fracture model, and the sclerosis around screws model. The resulting stress and displacement were analyzed by applying the contact forces associated with the most demanding activities during gait, including walking, standing, and knee bending. The present study establishes a comprehensive framework for investigating the biomechanical properties of internal fixation devices in the context of femoral fractures.ResultsThe stress at the top of the femoral head in the sclerotic model was increased by roughly 15 MPa during the knee bend and walking phases and by about 30 MPa during the standing phase compared to the healing model. The area of high stress at the top of the femoral head was increased during the sclerotic model's walking and standing phases. Additionally, the stress distribution throughout the dynamic gait cycle was comparable before and after the removal of internal fixations following the healing of the FNF. The overall stress distribution of the entire fractured femoral model was lower and more evenly distributed in all combinations of internal fixation. Furthermore, the internal fixation stress concentration was lower when more BNs were used. In the fractured model with three cannulated screws (CSs), however, the majority of the stress was concentrated around the ends of the fractures.The maximal stress in the healing model with one CS and two BNs was the highest at all stages of gait over three combinations of internal fixation, and the stress was mainly carried by CS.ConclusionsThe presence of sclerosis around screw paths increases the risk of femoral head necrosis. Removal of CS has little effect on the mechanics of the femur after healing of the FNF. BNs have several advantages over conventional CSs after FNF. Replacing all internal fixations with BNs after the healing of FNF may solve the problem of sclerosis formation around CSs to improve bone reconstruction owing to their bioactivity.Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.

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