Modern metal on metal articulation for total hip replacements.

Between 1991 and 1994, 70 patients received total hip replacements with metal on metal articulation. The results of 54 of these patients with 54 hips who have a 2- to 4-year (2.7-year average) followup are reported. Patients were prospectively evaluated using the Harris hip score, a patient self assessment form, and radiographs. Hip aspiration was performed preoperatively and 6 to 24 months postoperatively in 24 hips with metal on metal articulations. Implant retrieval was obtained from 2 patients. Harris hip score averages increased from 49 to 93. No patient had revision surgery for loosening, but 1 had revision surgery for dislocation. Patient self assessment forms showed 51 of 54 patients scored their results as good or excellent. Serial radiographs did not show loosening or osteolysis. Wear could not be measured radiographically. Synovial fluid samples had metal particles of 1 to 10 microm in 10 hips. Twenty patients had bilateral total hip replacements with 1 hip metal on polyethylene articulation, and patients could not determine any difference between the hips. Compared with historic results of previous metal on metal prostheses, the modern metal on metal articulation investigated in this study did not have early acetabular loosening or clinical symptoms of component impaction. Retrieval implants and synovial fluid analysis suggest early wear was minimal.