Abstract
Wear of ultra-high molecular weight polyethylene (UHMWP) acetabular cups is a well-known cause of osteolysis and loosening of the components. Improvement of the wear resistance of UHMWP could extend the clinical life of total hip arthroplasty (THA). Chemical cross-linking in acetylene with gamma radiation is a cheap and effective way of increasing wear resistance of UHMWP.
This study is a report on 263 patients (123 males and 140 females) on whom Dr Weber performed THA between 1977 and 1984, using the Pretoria (Grobbelaar) monobloc stainless steel hip with 30-mm metal head. There were 96 patients (107 prostheses) available for follow-up at a mean of 18.3 years, with 89 surviving prosthesis in 79 patients (83.2%).
We collected complete sets of radiographs of 54 patients (mean age 71.4 years) for a radiological survey in 1999. In 41 patients (76%) we found no wear. The mean age of these patients was 72 years. Wear was noted in the other 13 patients (24%), whose mean age was 75 years. The mean follow-up time was 16 years (8 to 23). The mean magnification in the radiological study was 18%. Mean wear for the total group was 1.29 mm and mean annual wear 0.17 mm.
A similar analysis performed on a group of 64 of Dr Grobbelaar’s patients at 15.5 year mean follow-up shows remarkable similarity, with mean wear of 0.172 mm for a group of 64 patients and annual wear 0.11 mm. Dr Oonishi of Japan, who has conducted the only other long-term follow-up, found similarly promising results.
The abstracts were prepared by Professor M. B. E. Sweet. Correspondence should be addressed to him at The Department of Orthopaedic Surgery, Medical School, University of Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193 South Africa
