Specimen-specific modeling of hip fracture pattern and repair

Hip fracture remains a major health problem for the elderly. Clinical studies have assessed fracture risk based on bone quality in the aging population and cadaveric testing has quantified bone strength and fracture loads. Prior modeling has primarily focused on quantifying the strain distribution in bone as an indicator of fracture risk. Recent advances in the extended finite element method (XFEM) enable prediction of the initiation and propagation of cracks without requiring a priori knowledge of the crack path. Accordingly, the objectives of this study were to predict femoral fracture in specimen-specific models using the XFEM approach, to perform one-to-one comparisons of predicted and in vitro fracture patterns, and to develop a framework to assess the mechanics and load transfer in the fractured femur when it is repaired with an osteosynthesis implant. Five specimen-specific femur models were developed from in vitro experiments under a simulated stance loading condition. Predicted fracture patterns closely matched the in vitro patterns; however, predictions of fracture load differed by approximately 50% due to sensitivity to local material properties. Specimen-specific intertrochanteric fractures were induced by subjecting the femur models to a sideways fall and repaired with a contemporary implant. Under a post-surgical stance loading, model-predicted load sharing between the implant and bone across the fracture surface varied from 59%:41% to 89%:11%, underscoring the importance of considering anatomic and fracture variability in the evaluation of implants. XFEM modeling shows potential as a macro-level analysis enabling fracture investigations of clinical cohorts, including at-risk groups, and the design of robust implants.     

锁定加压钢板接骨术治疗胫骨Pilon 骨折

目的:评估锁定加压钢板接骨术治疗胫骨Pilon骨折的应用价值。方法:2006年4月-2010年12月,对48例胫骨Pilon骨折患者,采用锁定加压钢板(LCP)治疗的结果进行总结。手术前后运用AOFAS(美国足与踝关节协会)踝与后足功能评分(Ankl-e-Hindfoot Scale)系统进行治疗效果的评估。结果:本组按AOFAS踝与后足功能评分系统:术前平均为(67.6±7.4)分,可18例,差30例;术后评分改善到平均为(90.9±7.2)分,优19例,良21例,可5例,差3例,踝与后足功能评分术前与术后比较,差异有统计学意义(P<0.05)。结论:用锁定加压钢板接骨术治疗胫骨Pilon骨折,有利于踝关节功能恢复,疗效确切,适应症广泛,较其他内固定器而言,锁定加压钢板在临床上更适用。