Abstract
Purpose: Exposure to polyethylene debris and bearing wear is a common feature of total hip prosthesis inserted with or without cement. Osteolysis depends on the number of particles involved and their size. This continuous series of total hip arthroplasties using a Corail prosthesis with 12 years follow-up was studied to assess the course of osteolysis around the prosthesis and the resistance of hydroxyapatite coated implants to the aggression of wear debris.
Material and methods: One hundred fifteen patients underwent total hip arthroplasty in 1989 with a Corail prosthesis implanted by the same operator with a metal backed cup and a polyethylene insert. Mean age at implantation was 65 years. Review radiograms were available for 80 patients (38 women and 42 men). Twenty-seven patients had died, five answered a phone interview and three were lost to follow-up. The follow-up was 12 years and analysis was performed on the population with review data and x-rays.
Results: There was no case with a loosened stem and none of the patients underwent revision. Twelve cups were however revised for loosening with granuloma. Polyethylene insert wear was seen in 62% of the cases. There was a relationship between the amount of wear debris and the extent of the gramulomas on the femur. These granulomas were basically observed in zones I and VII. Bone defects were curetted and filled with grafts for the 12 cup revisions. The cup bearing was changed in young patients. Good bone healing was a constant finding on follow-up x-rays.
Discussion: Hydroxyapatite coated prostheses exhibit good long-term resistance to wear debris which causes osteolysis since none of the Corail femoral stems were destabilised. The granulomas remain localised in the proximal zone and do not descend along the stem or the cement as seen in cemented prostheses. The intimate contact between the recipient bone and the implant appears to form a barrier against migration of wear debris. It thus appears important to achieve good contact all along the stem and to use a totally hydroxyapatite coated implant.
Conclusion: Total hip arthroplasty without cement is spared the problem of polyethylene wear debris, but debris must be limited to prevent osteolysis. This observation questions the long-term appropriateness of metal-backed cups with polyethylene inserts and suggests that low friction arthroplasty or use of a hard bearing couple (Cr-Co-Cr-Co or alumina-alumina) should be preferred.
The abstracts were prepared by Docteur Jean Barthas. Correspondence should be addressed to him at Secrétariat de la Société S.O.F.C.O.T., 56 rue Boissonade, 75014 Paris.
