Orthopaedic and Rehabilitation Engineering Center (OREC), Marquette University/Medical College of Wisconsin, Milwaukee, WI 53201-1881, USA.
Med Eng Phys. 2009 Nov;31(9):1043-8. doi: 10.1016/j.medengphy.2009.06.010. Epub 2009 Aug 15.
Osteogenesis imperfecta (OI) is a heritable bone fragility disorder characterized by skeletal deformities and increased bone fragility. There is currently no established clinical method for quantifying fracture risk in OI patients. This study begins the development of a patient-specific model for femur fracture risk assessment and prediction based on individuals' gait analysis data, bone geometry from imaging and material properties from nanoindentation (Young's modulus=19 GPa, Poisson's ratio=0.3). Finite element models of the femur were developed to assess fracture risk of the femur in a pediatric patient with OI type I. Kinetic data from clinical gait analysis was used to prescribe loading conditions on the femoral head and condyles along with muscle forces on the bone's surface. von Mises stresses were analyzed against a fracture strength of 115 MPa. The patient with OI whose femur was modeled showed no risk of femoral fracture during normal gait. The highest stress levels occurred during the mid-stance and loading responses phases of gait. The location of high stress migrated throughout the femoral diaphysis across the gait cycle. Maximum femoral stress levels occurred during the gait cycle phases associated with the highest loading. The fracture risk (fracture strength/von Mises stress), however, was low. This study provides a relevant method for combining functional activity, material property and analytical methods to improve patient monitoring.
成骨不全症（OI）是一种遗传性骨骼脆弱疾病，其特征为骨骼畸形和增加的骨骼脆弱。目前，尚未建立用于量化 OI 患者骨折风险的既定临床方法。本研究开始开发一种基于个体步态分析数据、影像学骨骼几何形状和纳米压痕材料特性（杨氏模量=19GPa，泊松比=0.3）的股骨骨折风险评估和预测的患者特异性模型。为评估 I 型 OI 患儿的股骨骨折风险，开发了股骨的有限元模型。使用临床步态分析的动力学数据来规定股骨头和股骨髁的加载条件以及骨骼表面的肌肉力。分析了 von Mises 应力与 115MPa 的骨折强度相比。所建模的 OI 患者在正常步态中没有股骨骨折的风险。在步态的中间站立和加载响应阶段，最高的应力水平出现。高应力的位置在整个股骨骨干中随步态周期发生迁移。最大的股骨应力水平出现在与最高负荷相关的步态周期阶段。然而，骨折风险（骨折强度/von Mises 应力）较低。本研究提供了一种相关方法，用于结合功能活动、材料特性和分析方法来改善患者监测。
