Shih Kao-Shang, Tseng Ching-Shiow, Lee Chia-Ching, Lin Shang-Chih
Division of Orthopedic Surgery, Department of Surgery, Far Eastern Memorial Hospital, Taipei, Taiwan.
Clin Biomech (Bristol). 2008 Jan;23(1):38-44. doi: 10.1016/j.clinbiomech.2007.08.020. Epub 2007 Oct 22.
In the literature, the commonly assumed loading conditions on the proximal femur are hip compression and/or gluteus contractions. However, no study has discussed the influence of muscle forces on failure of distal nail holes and locking screws.
This finite-element study analyzed the influence of muscular contractions on stress analysis of distal nail holes and locking screws. Three loading conditions were used for comparison, comprised of either hip compression alone or with muscle contractions. The head displacement of intact and fractured femur, the nail and screw stresses vs. fixation depth, and the stress distribution at the distal nail-screw interfaces were chosen as the comparison indices.
The addition of trochanteric and diaphysial muscles showed the more physiologically reasonable displacement of the femoral head. However, all loading conditions consistently showed the hole and screw stresses increase as the nail was inserted deeper. The stress distribution at the distal nail-screw interfaces was remarkably different under the condition of with or without the muscular contractions. The exertion of muscles predicted the fatigue cracking originated at the edge of the nail holes on the medial rather than lateral side.
Only hip compression and/or gluteus contraction generated a characteristic bending stress pattern and medially deflected nail curvature. Comparatively, the trochanteric and diaphysial muscles stabilized the femoral head and resulted in the higher stress concentration at the distally medial nail-screw interfaces. However, further experimental and clinical studies, focusing on the failure sites of the distal femoral hardware, should be undertaken to validate such findings.
在文献中,通常假定股骨近端的负荷条件为髋关节压缩和/或臀肌收缩。然而,尚无研究讨论肌肉力量对远端钉孔和锁定螺钉失效的影响。
本有限元研究分析了肌肉收缩对远端钉孔和锁定螺钉应力分析的影响。使用三种负荷条件进行比较,包括单独的髋关节压缩或伴有肌肉收缩。选择完整和骨折股骨的头部位移、钉和螺钉应力与固定深度的关系以及远端钉-螺钉界面处的应力分布作为比较指标。
增加转子肌和骨干肌显示股骨头的位移在生理上更合理。然而,所有负荷条件均一致显示,随着钉插入更深,孔和螺钉的应力增加。在有或没有肌肉收缩的情况下,远端钉-螺钉界面处的应力分布明显不同。肌肉的作用预示着疲劳裂纹起源于内侧而非外侧的钉孔边缘。
仅髋关节压缩和/或臀肌收缩会产生特征性的弯曲应力模式和钉向内偏转的曲率。相比之下,转子肌和骨干肌稳定了股骨头,并导致远端内侧钉-螺钉界面处的应力集中更高。然而,应进行进一步的实验和临床研究,重点关注股骨远端内固定装置的失效部位,以验证这些发现。