Revision of a single type of large metal head metal-on-metal hip prosthesis.

Large-head metal-on-metal (MoM) total hip arthroplasties were introduced because of their purported advantages. Inflammatory pseudotumours occasionally occur after MoM hip arthroplasty and often lead to revision. The purpose of this study was to assess the outcome of revision of large-head MoM total hip arthroplasties after an extensive screening protocol for all MoM articulations with a minimum 2 year follow-up. We identified 50 hips that had undergone large-head MoM total hip arthoplasty and required revision at a mean of 44 months after index operation. Of these, 38 were revised for pseudotumours, 7 for loosening, 2 for infection and 3 for instability. There was bone loss in 44 hips. The majority were revised to a 28 mm metal or ceramic head on a polyethylene-cemented cup. In 12 patients there was a complication. There was a decrease of whole blood cobalt from 20.8 µg/L preoperatively to 1.8 µg/L 1 year after revision. We found 6 residual masses on routine postoperative CT scans. The indication for revision of this cohort is inevitable but the clinical outcome 2 years after revision for pseudotumour is disappointing. Revising a MoM hip arthroplasty to a conventional cemented polyethylene or dual-mobility cup with bone impaction grafting and a 28 mm head can adequately treat the high ion levels and probably the disease of ARMD.