PREDICTION OF SERVICE LIFETIME AND PERFORMANCE OF A PROSTHETIC THERMOPLASTIC

The service lifetime and performance for a prosthetic and orthotic the rmoplastic, Subortholen(TM), was measured using correlations between a rtificial and natural weathering degradation data of (1) the accumulat ed carbonyl compound concentration at the polymer surface, (2) changes in thickness of the surface reaction zone, and (3) changes in hardnes s and tensile properties. An empirical, mathematical relationship betw een artificial and natural weathering exposures is presented. Results show that the hardness degradation is a useful parameter to estimate t he different stages in clinical performance of Subortholen. Corroborat ing hardness, tensile properties, and weathering exposure time, the se rvice lifetime for Subortholen was determined to be 4-6 years. This fi nding indicates that the correlation between artificial and natural we athering degradation may provide an effective way to calculate the mos t appropriate time to replace a worn prosthetic or orthotic device bef ore the device passes into a dangerous stage. (C) 1995 John Wiley & So ns, Inc.