Taylor Carolyn E, Henninger Heath B, Bachus Kent N
Department of Orthopaedics, School of Medicine, University of Utah, Salt Lake City, UT, United States.
Department of Biomedical Engineering, College of Engineering, University of Utah, Salt Lake City, UT, United States.
Front Rehabil Sci. 2021 Nov 23;2. doi: 10.3389/fresc.2021.744674.
Cadaveric mechanical testing of a percutaneous osseointegration docking system (PODS) for osseointegration (OI) prosthetic limb attachment revealed that translation of the exact system from the humerus to the tibia may not be suitable. The PODS, designed specifically for the humerus achieved 1.4-4.8 times greater mechanical stability in the humerus than in the tibia despite morphology that indicated translational feasibility. To better understand this discrepancy, finite element analyses (FEAs) modeled the implantation of the PODS into the bones. Models from cadaveric humeri ( = 3) and tibia ( = 3) were constructed from CT scans, and virtual implantation preparation of an array of endoprosthesis sizes that made contact with the endosteal surface but did not penetrate the outer cortex was performed. Final impaction of the endoprosthesis was simulated using a displacement ramp function to press the endoprosthesis model into the bone. Impaction force and maximum first principal (circumferential) stress were recorded to estimate stability and assess fracture risk of the system. We hypothesized that the humerus and tibia would have different optimal PODS sizing criteria that maximized impaction force and minimized first principal stress. The optimal sizing for the humerus corresponded to implantation instructions, whereas for the tibia optimal sizing was three times larger than the guidelines indicated. This FEA examination of impaction force and stress distribution lead us to believe that the same endoprosthesis strategy for the humerus is not suitable for the tibia because of thin medial and lateral cortices that compromise implantation.
对用于骨整合（OI）假肢连接的经皮骨整合对接系统（PODS）进行尸体力学测试发现，将该精确系统从肱骨平移至胫骨可能并不合适。专门为肱骨设计的PODS在肱骨中的机械稳定性比在胫骨中高1.4至4.8倍，尽管其形态表明平移具有可行性。为了更好地理解这种差异，有限元分析（FEA）对PODS植入骨骼的过程进行了建模。从尸体肱骨（n = 3）和胫骨（n = 3）的CT扫描构建模型，并对一系列与骨内膜表面接触但未穿透外皮质的假体尺寸进行虚拟植入准备。使用位移斜坡函数模拟假体的最终压入，将假体模型压入骨骼。记录压入力和最大第一主（周向）应力，以估计系统的稳定性并评估骨折风险。我们假设肱骨和胫骨会有不同的最佳PODS尺寸标准，以最大化压入力并最小化第一主应力。肱骨的最佳尺寸符合植入说明，而胫骨的最佳尺寸比指南指示的大三倍。这种对压入力和应力分布的FEA检查使我们相信，由于内侧和外侧皮质较薄会影响植入，用于肱骨的相同假体策略不适用于胫骨。
