Contact Pressure at the Limb/Prosthesis Interface
It is estimated that there are at least three million amputees in the world. Amputation can be caused by vascular diseases, infection, cancer, and traumatic accidents. Prosthetic replacement is one of the most significant rehabilitation programs. A good lower-limb prosthesis can restore locomotive function and improve the self body-image as well as general health of an amputee. A prosthesis replaces some of the important functions lost due to amputation, and should do so without causing discomfort, pain, or damage to the soft tissue of the residual limb. An external prosthesis is composed of a prosthetic socket and a prosthetic foot, which are interconnected by a shank and possibly some prosthetic joints. A socket is a part of a prosthesis that connects to the residual limb. A good understanding of the mechanical interaction between the socket and the residual limb is required to provide comfort and prevent skin breakdown around the residual limb. The shape of the socket is not exactly a replica of the residual limb, but should be modified so that the load is transferred to the residual limb efficiently. This addresses the nonuniform thickness of soft tissue around the residual limb and the difference in load-tolerant abilities over residual limb regions. A socket is designed to support the body weight of an amputee by applying a reasonable pressure to the residual limb. A number of factors, such as socket design, residual limb length, and alignment, may influence the socket-limb interface pressure. Here we will apply classic mechanics to analyze the interaction between the prosthetic socket and the residual limb. The focus will be on prostheses for amputations at transtibial levels, due to the large percentage of amputees at this level.