Abstract
Introduction: The results of metal-on-metal hip resurfacing (MOMHR) from inventing centres show excellent function with low revision rates in the short to intermediate term. This study investigated whether similar results could be achieved in an independent unit.
Methods: All cases of MOMHR were identified since its introduction in our centre in 1999, and cases with less than 18 months follow-up excluded. Outcome was assessed by Oxford Hip Score (OHS), and UCLA activity score. Complications and further surgery was recorded. Pre-, post-op and follow-up radiographs were reviewed.
Results: 358 resurfacings in 315 patients (238 Birmingham hip resurfacings and 120 Cormet 2000, 8 surgeons). 13 (3.6%) revisions: 4 early fractures, 6 osteonecrosis, 1 aseptic femoral loosening, 1 infection, 1 isolated cup revision. 2 died, 16 (4.7%) were lost to follow-up. Outcome was assessed in the remaining 327 hips at a mean 39 months (18–79). Median OHS 13, median UCLA score 8. 89% employed in moderately heavy or heavy occupational work pre-operatively were similarly employed at follow-up.
2 cups had migrated and 6 had lucent lines. 8 femoral components had migrated. 6 had focal osteolysis. 66% of hips had ‘pedestal’ signs around the stem of the femoral component (classification proposed).
Discussion: The functional outcomes achieved in this series match those from inventing centres, but the revision rate was higher. This is partly explained by early fractures which may be associated with poor case selection or technical errors early in a surgeon’s learning curve. Later failures, of which osteonecrosis is of particular interest, also occurred at a higher rate. Migration of the femoral component may represent impending failure and further work is required to define the aetiology and consequences of the pedestal signs noted.
Correspondence should be addressed to The Secretary, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
