Abstract
We studied the below-knee prostheses of 111 injured workers and retirees over a period of four years (1979-1982). We noted signs of wear and damage, including break sites and break frequency, and examined the causes of damage. The typical prosthesis was PTB type with a SACH foot; this mechanically sophisticated arrangement suited the wearers well because most of them were involved in light labor. The average endurable life of a socket or parts was much shorter for Syme and PTES prostheses than for PTB and KBM prostheses. This tendency was especially notable in unilateral below-knee amputees, for whom type of prosthesis and intensity of daily activity were more strongly related to damage than length of the stump. Among bilateral amputees, intensity of daily activity was not closely related to extent of damage of the prosthesis, rather frequent breakage was attributable to unstable gait and movement. Among bilateral amputees with a BK on one side and an AK on the other, low frequency of breakage was attributable to a relatively low intensity of daily activity.
Frequently damaged sites of the socket varied according to type of prosthesis. One site frequently damaged in all types was the hamstring channel, i. e., the region in contact with the medial hamstrings. This site was structurally weak because of forces contiunally acting to widen the channel, and reactive forces during knee flexion in gait further aggravated this region. Greater precision in distributing intrasocket pressure evenly may thus be valuable in improving the shape and quality of prosthetic sockets.
