Zavaleta-Ruiz Jose L, Major Matthew J, Pankaj Pankaj
School of Engineering, The University of Edinburgh, Edinburgh, UK.
Department of Physical Medicine & Rehabilitation, Department of Biomedical Engineering, Northwestern University, Jesse Brown VA Medical Center, Chicago, Illinois, USA.
Int J Numer Method Biomed Eng. 2025 Feb;41(2):e70014. doi: 10.1002/cnm.70014.
There is a five-decade recorded history indicating that persons with transfemoral amputation experience bone loss in their amputated femur at levels seen in bedridden and post-menopausal individuals, irrespective of age or mobility levels. We used computer simulation to recreate the mechanical environment created by the mechanical design of a prosthetic device in the surviving femur of individuals with transfemoral amputations. Finite element models of gait instances were developed from the hip joint computerized tomography scan of a subject along with a coupled ischial containment prosthetic socket fitted as per standard clinical guidelines. Accompanying mirror models, assembled similarly but without the prosthetic socket were used for stimulus comparison. Simulation showed that more than 90% of the trabecular bone volume in the amputated femur with an ischial containment socket registered compressive strain magnitudes below 300με. These strain magnitudes are below the threshold for bone maintenance as per mechanotransduction theory (i.e., they lie within the disuse window). Only 50% of the bone was in the disuse window for the mirror model for the gait instances considered. These results are consistent with reported in vivo evidence which shows that transfemoral prosthesis users may lose bone mass irrespective of age or mobility levels when using traditional socket designs. Clinically, this study shows that prosthetic sockets that support load through the ischium alter the kinetic chain and preclude application of mechanical stimulus that sustains healthy levels of bone mass in the proximal femur. The study also shows that femur length, prosthetic alignment and tissue tone influence this stimulus.
有长达五十年的记录历史表明，经股截肢者的截肢股骨会出现骨质流失，其程度与卧床不起和绝经后的个体相当，与年龄或活动水平无关。我们使用计算机模拟来重现经股截肢者残存活骨中假体装置机械设计所创造的机械环境。步态实例的有限元模型是根据一名受试者的髋关节计算机断层扫描以及按照标准临床指南安装的坐骨包容式假体承窝开发的。配套的镜像模型同样进行组装，但没有假体承窝，用于刺激比较。模拟显示，使用坐骨包容式承窝的截肢股骨中，超过90%的小梁骨体积记录的压缩应变幅度低于300με。根据机械转导理论，这些应变幅度低于维持骨骼的阈值（即它们处于废用范围内）。在所考虑的步态实例的镜像模型中，只有50%的骨骼处于废用范围内。这些结果与已报道的体内证据一致，该证据表明，经股假肢使用者在使用传统承窝设计时，无论年龄或活动水平如何，都可能会骨质流失。临床上，这项研究表明，通过坐骨支撑负荷的假体承窝会改变动力链，并排除对维持股骨近端健康骨量水平的机械刺激的应用。该研究还表明，股骨长度、假体对线和组织张力会影响这种刺激。
