Cosmetic effect of knee joint in a knee disarticulation prosthesis.

Despite numerous advantages, knee disarticulations (KDs) are rarely performed because of the anticipated KD prosthesis fitting problems that include the positioning of the knee joint distally from the KD socket. This results in lengthening of the thigh and subsequent shortening of the shank. The objective of this study was to assess the cosmetic effect of the knee joint in a KD prosthesis by determining the extent of the lengthening of the thigh and the shortening of the shank. This lengthening and shortening were measured through an experimental setup using laser techniques. These measurements were made of 18 knee joints used in KD prostheses. Lengthening of the thigh varied between 23 and 92 mm, and shortening of the shank varied between 3 and 50 mm. The polycentric knees Medi KH6 and Medi KHF1 showed the least lengthening of the thigh, and the polycentric knees Teh Lin Prosthetic & Orthotic Co. Ltd Graph-Lite and Medi KP5 showed the least shortening of the shank.