Dynamic testing of below-knee prosthesis: assembly and components

Prosthetic assemblies for lower limb amputees are highly engineered and consist of several components each with its own failure mechanism. This paper describes the dynamic testing of HDPE rotational moulded sockets in a specially designed machine which mimics normal gait. Thus the components are subjected to all main loadings occurring during a stride such as axial loading and A-P bending about the knee and ankle. Machine details as well as the other components of the system are described. SACH feet appear to be vulnerable by rapid wear and structural component failures at less than 100,000 cycles were observed. The sockets are much less vulnerable and stand up to simulated loading of 1350 N for approximately 400,000 cycles. Metal components such as the foot bolt may also fail in fatigue if not properly tightened. References to proposed ISO standards are also included.