HYBRID METAL ON METAL SURFACE ARTHROPLASTY: FIRST 300 HIPS WITH 2.5–5.9 YEARS OF FOLLOW UP

Abstract

To review short to medium term results of a metalon-metal (M/M) hybrid surface arthroplasty (SA) for a young and active patient population.

The first 300 hips (of 564) in 263 patients underwent M/M hybrid surface arthroplasty (cementless acetabular and cemented femoral components). Demographics: mean age 48.4; 75% males, 25% females; 141 Charnley Class A; 109 Class B and 13 Class C. Diagnosis at surgery: OA 67%, DDH 10.3%, ON 8.3%, Post-traumatic 6.7%, Inflammatory arthritis and Rheumatoid Disease 4%, SCFE and LCP 3.4%, Melorheostosis 0.3%.

Mean follow-up 3.6 years (2.5–5.9). Average UCLA hip scores post-op: pain 9.4, walking 9.5, function 9.4 and activity 7.7. Average Harris Hip Score was 92.8. The SF-12 physical and mental components were respectively, 31.4 and 47.2 pre-op and 49.9 and 52.9 post-op. DEXA data suggests preservation or restoration of neck BMD.

The experience with SA of all cemented metal/ UHMWPE bearing demonstrated failure rates of 15%–33% at 3 years. At longer follow-up, the preliminary experience is encouraging (3.6% failure rate) and eventual conversions to THR are facilitated with unipolar heads. The technique preserves femoral and ace-tabular bone, dislocation is rare, and acetabular fixation secure. Initial femoral fixation is critical as the fixation area is small, especially with osteopenia and cystic degeneration. The percent of potentially adverse radiographic changes was much greater in the first 100 cases, during the time of development of instrumentation, technique, and bearing optimisation.