University of Pennsylvania, Philadelphia, PA, United States of America.
University of Pennsylvania, Philadelphia, PA, United States of America.
Bone. 2019 May;122:209-217. doi: 10.1016/j.bone.2019.03.005. Epub 2019 Mar 7.
Currently, clinical determination of pathologic fracture risk in the hip is conducted using measures of defect size and shape in the stance loading condition. However, these measures often do not consider how changing lesion locations or how various loading conditions impact bone strength. The goal of this study was to determine the impact of defect location on bone strength parameters in both the sideways fall and stance-loading conditions. We recruited 20 female subjects aged 48-77 years for this study and performed MRI of the proximal femur. Using these images, we simulated 10-mm pathologic defects in greater trochanter, superior, middle, and inferior femoral head, superior, middle, and inferior femoral neck, and lateral, middle, and medial proximal diaphysis to determine the effect of defect location on change in bone strength by performing finite element analysis. We compared the effect of each osteolytic lesion on bone stiffness, strength, resilience, and toughness. For the sideways fall loading, defects in the inferior femoral head (12.21%) and in the greater trochanter (6.43%) resulted in the greatest overall reduction in bone strength. For the stance loading, defects in the mid femoral head (-7.91%) and superior femoral head (-7.82%) resulted in the greatest overall reduction in bone strength. Changes in stiffness, yield force, ultimate force, resilience, and toughness were not found to be significantly correlated between the sideways fall and stance-loading for the majority of defect locations, suggesting that calculations based on the stance-loading condition are not predictive of the change in bone strength experienced in the sideways fall condition. While stiffness was significantly related to yield force (R > 0.82), overall force (R > 0.59), and resilience (R > 0.55), in both, the stance-loading and sideways fall conditions for most defect locations, stiffness was not significantly related to toughness. Therefore, structure-dependent measure such as stiffness may not fully explain the post-yield measures, which depend on material failure properties. The data showed that MRI-based models have the sensitivity to determine the effect of pathologic lesions on bone strength.
目前，髋关节病理性骨折风险的临床评估是通过站立位负荷条件下的缺陷大小和形状来进行的。然而，这些方法通常不考虑病变位置的变化或各种负荷条件如何影响骨强度。本研究的目的是确定缺陷位置在侧方跌倒和站立位负荷两种情况下对骨强度参数的影响。我们招募了 20 名年龄在 48-77 岁的女性受试者参与本研究，并对其进行了股骨近端 MRI 检查。使用这些图像，我们模拟了大转子、股骨头上部、中部和下部、股骨颈上部、中部和下部以及股骨近端骨干外侧、中部和内侧 10mm 的病理性缺陷，通过有限元分析来确定缺陷位置对骨强度变化的影响。我们比较了每个溶骨性病变对骨刚度、强度、弹性和韧性的影响。对于侧方跌倒负荷，股骨头下部（12.21%）和大转子（6.43%）的缺陷导致骨强度总体下降最大。对于站立位负荷，股骨头中部（-7.91%）和股骨头上部（-7.82%）的缺陷导致骨强度总体下降最大。对于大多数缺陷位置，侧方跌倒和站立位负荷条件下的刚度、屈服力、极限力、弹性和韧性变化之间没有发现显著相关性，这表明基于站立位负荷条件的计算不能预测侧方跌倒条件下骨强度的变化。在大多数缺陷位置，站立位和侧方跌倒两种负荷条件下，刚度与屈服力（R>0.82）、总力（R>0.59）和弹性（R>0.55）显著相关，但与韧性无关。因此，像刚度这样的结构依赖性指标可能不能完全解释依赖于材料失效特性的屈服后指标。数据表明，基于 MRI 的模型具有确定病理性病变对骨强度影响的敏感性。
