LONG-TERM ANALYSIS OF COMPLICATIONS IN 1771 SINGLE-COMPARTMENT KNEE PROSTHESIS

Abstract

Purpose: We analysed complications observed after 1771 implantations of single-compartment knee prostheses performed since 1974.

Material and methods: Sterilised all polyethylene Marmor implants were used from 1974 to 1984. Metal-backed tibial implants with or without cement and condyle resurfacing were added after 1984.

Results: Mean survival of the 207 Marmor cemented prostheses implanted from 1974 to 1984 was 93% at 12 years. There were nine significant complications: seven loosenings, three with infection, and two deteriorations of the other compartment. There were five minor complications: two instabilities, one patellar and one anterior laxity; two stiff joints; one meniscal lesion in the other compartment and one hamstring tendinitis. A non-adjustable cobalt-chromium metal backed insert was added to the polyethylene lining in 1984. For the 790 implants using this prosthesis, 48 had to be revised (6%) four to eight years after implantation for polyethylene wear due to an insufficient thickness for size 7.5 mm and gamma sterilisation.

These observations led us to use, since 1991, two new polyethylene inserts sterilised with ethylene oxide: an adjustable titanium metal-back support with cement in 329 cases and without cement in 171 with hydroxyapatite surfacing, and a modified Marmor with complete thickness (min 9 mm) peripheral cortical support used in 274 cases. Fourteen revisions were required for: screwing problems in three cases early in our experience, three loosenings, three inappropriate indications, two patellar problems, one deterioration of the other compartment, one knee instability on an oblique plateau and unexplained residual knee pain. There was no evidence of significant polyethylene wear, even for the oldest cases in our series.

Conclusion: This long-term analysis of single-compartment knee prostheses has shown that at the tibial level the essential elements are the minimal thickness of the polyethylene, the type of sterilisation, and the type of metal back. Resurfaced condyles have demonstrated their superiority over those requiring a resection since only one femoral loosening was observed. Revision for total knee arthroplasty is not different from first intention replacements.