Department of Mechanical Engineering, University of Colorado Denver, Denver, CO, United States of America.
Department of Orthopedics, University of Colorado School of Medicine, Aurora, CO, United States of America.
Bone. 2023 Jul;172:116752. doi: 10.1016/j.bone.2023.116752. Epub 2023 Mar 31.
Patients with transfemoral amputation (TFA) are up to six times more likely to develop hip osteoarthritis (OA) in either or both the intact and residual limb, which is primarily attributed to habitually altered joint loading due to compensatory movement patterns. However, joint loading patterns differ between limbs, which confounds the understanding of loading-induced OA etiology across limbs. It remains unknown if altered loading due to amputation results in bony shape changes at the hip, which is a known etiological factor in the development of hip OA. Retrospective computed tomography images were collected of the residual limb for 31 patients with unilateral TFA (13F/18M; age: 51.7 ± 9.9 y/o; time since amputation: 13.7 ± 12.4 years) and proximal femur for a control group of 29 patients (13F/16M; age: 42.0 ± 12.27 years) and used to create 3D geometries of the proximal femur. Femoral 3D geometric variation was quantified using statistical shape modeling (SSM), a computational tool which placed 2048 corresponding particles on each geometry. Independent modes of variation were created using principal component analysis. 2D radiographic measures of the proximal femur, including common measures such as α-angle, head neck offset, and neck shaft angle, were quantified on digitally reconstructed radiographs (DRRs). SSM results were then compared to 2D measures using Pearson correlation coefficients (r). Two-sample t-tests were used to determine if there were significant differences between the TFA and control group means of 2D radiographic measurements (p < 0.05). Patients with TFA had greater femoral head asphericity within the SSM, which was moderately correlated to head-neck offset (r = -0.54) and α-angle (r = 0.63), as well as greater trochanteric torsion, which was strongly correlated to the novel radiographic measure of trochanteric torsion (r = -0.78), compared to controls. For 2D measures, the neck-shaft angle was smaller in the TFA group compared to the control group (p = 0.01) while greater trochanter height was larger in the TFA group compared to the control group (p = 0.04). These results indicate altered loading from transfemoral prosthesis use changes proximal femur bony morphology, including femoral head asphericity and greater trochanter changes. Greater trochanter morphologic changes, though not a known factor to OA, affect moment arm and line of action of the primary hip abductors, the major muscles which contribute to joint loading and hip stability. Thus, chronic altered loading of the amputated limb hip, whether under- or overloading, results in bony changes to the proximal femur which may contribute to the etiological progression and development of OA.
接受股骨截肢术（TFA）的患者在未截肢侧或截肢侧发生髋关节骨关节炎（OA）的可能性高达未截肢患者的 6 倍，这主要归因于习惯性代偿运动模式导致的关节负荷改变。然而，肢体间的关节负荷模式存在差异，这使得理解肢体间的负荷诱导性 OA 病因变得复杂。目前尚不清楚截肢引起的负荷改变是否会导致髋关节的骨形状发生变化，而髋关节的骨形状变化是髋关节 OA 发展的一个已知病因因素。收集了 31 名单侧 TFA 患者（13 名女性/18 名男性；年龄：51.7±9.9 岁/岁；截肢后时间：13.7±12.4 年）的残肢和 29 名对照组患者（13 名女性/16 名男性；年龄：42.0±12.27 岁）的股骨近端的回顾性 CT 图像，并用于创建股骨近端的 3D 几何图形。使用统计形状建模（SSM）对股骨 3D 几何形状变化进行量化，这是一种将 2048 个对应粒子放置在每个几何图形上的计算工具。使用主成分分析创建独立的变化模式。使用数字重建射线照相术（DRR）量化股骨近端的 2D 射线照相测量值，包括常见的测量值，如α角、头颈偏移和颈干角。然后使用 Pearson 相关系数（r）将 SSM 结果与 2D 测量值进行比较。使用双样本 t 检验确定 TFA 组和对照组的 2D 射线照相测量值平均值之间是否存在显著差异（p<0.05）。与对照组相比，TFA 患者的股骨头在 SSM 中具有更大的非球度，这与头颈偏移（r=-0.54）和α角（r=0.63）中度相关，以及更大的转子扭转，这与转子扭转的新射线照相测量值高度相关（r=-0.78）。对于 2D 测量值，TFA 组的颈干角比对照组小（p=0.01），而 TFA 组的大转子高度比对照组大（p=0.04）。这些结果表明，股骨假体使用引起的负荷改变会改变股骨近端的骨骼形态，包括股骨头非球度和大转子变化。虽然大转子形态的变化不是 OA 的已知因素，但会影响主要髋关节外展肌的力臂和作用线，这些肌肉是导致关节负荷和髋关节稳定性的主要肌肉。因此，截肢肢体髋关节的慢性负荷改变，无论是过度负荷还是负荷不足，都会导致股骨近端发生骨骼变化，这可能是 OA 病因进展和发展的原因之一。
