骨水泥型长短柄假体置换治疗高龄偏髓I型转子间骨折的有限元分析

Finite element analysis of cemented long-and short-stem prosthetic replacement in elderly patients with partial marrow type I intertrochanteric fracturesand the maximum value was also lower than the fatigue strength of bone cement. No significant stress con- centration zones were found in the femoral calcar reconstructed using bone cement. Conclusions Ce- mented long- or short-stem prosthetic replacement achieves no significant alteration in stress distribution of the femur. Loosening probability of the cemented long- or short-stem prosthesis is almost the same, but the latter has advantages of shorter surgery time, minor trauma, and fewer complications and may be more suitable for treatment of the elderly patients with a partial marrow type I intertrochanteric fractures.

目的探讨高龄偏髓I型转子间骨折行骨水泥型股骨假体置换术后的股骨应力分布，并对比分析长、短假体柄置换后的应力分布差异。方法利用螺旋CT对志愿者的右侧股骨进行断层扫描获取图像数据，将图像数据经Mimics软件和建模软件处理后重建股骨三维模型。在此基础上，建立偏髓I型转子间骨折、长、短柄股骨假体及骨水泥套的三维实体模型，最后利用有限元分析软件建立长、短柄股骨假体治疗转子间骨折的三维有限元模型，并对该模型进行生物力学分析。结果长、短柄假体置换后股骨的应力分布没有发生明显改变，依然是由近端向远端逐渐增加，至内外侧中下1／3交界处达到峰值，再向末端又减小。短柄假体骨水泥一假体柄界面在末端内外侧虽形成应力集中区，且外侧峰值为15．3MPa，但未超过骨水泥疲劳强度；而长柄假体在骨水泥一假体柄界面远端内外侧及内侧中段形成应力集中区，其峰值也均低于骨水泥疲劳强度。骨水泥重建的股骨距部位未见明显的应力集中区。结论骨水泥型长、短柄假体置换治疗高龄偏髓I型转子间骨折不会引起股骨应力分布的明显改变。长柄假体的松动概率与短柄假体基本相当，但后者由于其手术时间短、创伤小、并发症少，可能更适合治疗高龄偏髓I型转子间骨折。

Objective To investigate the stress distribution in a cemented femoral component in elderly patients with a partial marrow type I intertrochanteric fractures and to compare differences in the stress distribution after a longand short-stem prosthetic replacement. Methods Spiral CT images of right femur of the volunteer were obtained and processed with Mimics software and modeling software to reconstruct a three-dimensional model of the femur. Based on this, a three-dimensional physical model for partial marrow type I intertrochanteric fractures, long- and short-stem femoral prostheses, and cement mantle was established. Subsequently, a three-dimensional finite element model of long- and short-stem prosthetic replacement for intertrochanteric fractures was established using the finite element analysis software, and biomechanical analysis was implemented for the model. Results No significant changes in stress distribution of the femur occurred after longor short-stem prosthetic replacement. Stress on the femur still presented a gradual increase from the proximal end to the distal end, peaked at the lower 1/3 of the medial and lateral junction and then decreased at the end. A stress concentration zone formed in the medial and lateral end of cement-stem interface in short-stem prosthetic replacement. Besides, the maximum value of stress in the lateral interface reached 15.3 MPa, but without surpassing the fatigue strength of the bone cement. Whereas, a stress concentration zone formed in the distal medial and lateral part of cement-stem interface and the medial middle part of the interface in long-stem prosthetic replacement