Long Jason P, Santner Thomas J, Bartel Donald L
University of Michigan, Ann Arbor, Michigan, USA.
J Orthop Res. 2009 Oct;27(10):1319-25. doi: 10.1002/jor.20884.
Short-term femoral neck fracture is a primary complication associated with contemporary hip resurfacing. Some fractures are associated with neck notching, while others occur in the absence of notching. These unexplained fractures may be due to large magnitude strains near the implant rim, which could cause bone damage accumulation and eventual neck fracture. We used statistically augmented finite element analysis to identify design and environmental variables that increase bone strains near the implant rim after resurfacing, and lead to strain magnitudes sufficient for rapid damage accumulation. After resurfacing, the compressive strains in the inferior, peripheral neck increased by approximately 25%, particularly when the implant shell was bonded. While the tensile strains in the peripheral neck were low in magnitude in the immediate postoperative models, they increased substantially following compressive damage accumulation. Low bone modulus, within the range of normal bone, and high head load contributed the most to large magnitude strains. Therefore, in some cases, hip resurfacing may cause a region of compressive bone damage to develop rapidly, which in turn leads to large tensile strains and potential neck fracture. Our study suggests that indications for surgery should account for bone material quality, and that rehabilitation protocols should avoid high-load activities.
短期股骨颈骨折是当代髋关节表面置换术的一种主要并发症。一些骨折与颈部开槽有关，而另一些则在无开槽的情况下发生。这些不明原因的骨折可能是由于植入物边缘附近的大应变，这可能导致骨损伤积累并最终导致颈部骨折。我们使用统计增强有限元分析来确定设计和环境变量，这些变量会增加表面置换术后植入物边缘附近的骨应变，并导致足以快速积累损伤的应变大小。表面置换术后，下颈部外周的压缩应变增加了约25%，特别是当植入物外壳粘结时。虽然术后即刻模型中外周颈部的拉伸应变大小较低，但在压缩损伤积累后它们大幅增加。在正常骨范围内的低骨模量和高头部负荷对大应变的影响最大。因此，在某些情况下，髋关节表面置换术可能会导致压缩性骨损伤区域迅速发展，进而导致大的拉伸应变和潜在的颈部骨折。我们的研究表明，手术指征应考虑骨材料质量，康复方案应避免高负荷活动。
