Evaluation of use and durability of polypropylene trans-tibial prostheses.

Forty-three (43) trans-tibial prostheses with a mean period of use of 33 months were evaluated in terms of utilisation and durability. The majority of the prostheses (80%) were worn by amputees with demanding occupations, such as farmers, fishermen and tradesmen. The prostheses were in use approximately 9 hours per day. No major or frequent breakdowns of the polypropylene prosthetic components were found. The suspension belts were the parts most frequently affected; a total of 32 needed replacement after an average 11 months of use. Eleven (11) prostheses were completely replaced, more than half at least partly because of socket-fitting problems. In all, socket-fitting problems were found in 15 prostheses, causing pain and consequently limitation of use. While the prosthetic polypropylene components were satisfactory, the rubber foot was a major cause of early breakdown. A total of 40 feet were replaced; their mean period of use before breakdown was 9 months. In practice, parts were frequently replaced at a later stage than desirable, meaning that there was frequent "overuse" of prostheses with worn parts. Measures were taken to increase the life span of the prosthesis: change in the design of the foot; issuing a spare foot with the prosthesis; strengthening the suspension belt. Additional evaluations are necessary to confirm the degree to which the findings are representative.