Metal-on-Metal Total Hip Arthroplasty at Five to Twelve Years Follow-Up: A Concise Follow-Up of a Previous Report.

BACKGROUND:Concern has arisen regarding potential complications with modular metal-on-metal (MoM) acetabular components in total hip arthroplasty. The purpose of this study was to analyze longitudinally the longer term results of a previously reported cohort of patients utilizing a cementless modular acetabular component with a MoM bearing. METHODS:One hundred sixty-nine consecutive but selected total hip arthroplasties were performed in 148 patients at 2 institutions using a modular acetabular MoM component. One hundred thirty-nine patients (158 hips) were living at minimum 5 years, 1 patient (1 hip) was lost to follow-up and 8 patients (10 hips) were deceased. Patients were evaluated clinically in terms of revision as well as radiographically. Additional testing (metal ion levels, advanced imaging) was performed when concerns for adverse local tissue reaction (ALTR) arose. RESULTS:There were 6 (3.8%) additional hips revised since the prior report for a total of 7 hips (4.4%) revised at 5-12 year follow-up. All newly revised hips (3.8%) demonstrated ALTR. There were 7 (4.7%) additional cases of radiographically detected acetabular osteolysis and 7 (4.7%) cases of femoral osteolysis. CONCLUSION:Longitudinal evaluation of a modular MoM bearing surface acetabular component demonstrated increased rates of ALTR and osteolysis at longer duration follow-up. Although greater than 95% of hips in this study performed well at 5-12 years, when comparing the results to metal-on-polyethylene bearings using the same acetabular component, the results were inferior. Longitudinal surveillance is warranted with this design and this bearing surface couple as cases of ALTR and osteolysis increased with longer follow-up.