Abstract
Introduction
Metal on metal hip bearings (MoM) are under scrutiny. Short and mid-term complications attributed to metal wear debris have been reported. Distinctions between MoM prostheses exist. Thus, generalizing findings from one design to another is questionable. This study reports minimum 5 yr. Pinnacle™ modular MoM results.
Methods
Between September 2001 and October 2004, 95 consecutive MoM THAs were performed by one surgeon in a prospective cohort design. Mean age was 53 yrs (range 34-70); 57 were male. Mean BMI was 29 (range 20-46). OA was noted in 87 patients. Head size was 28mm in 3 and 36mm in 92. Surgical approach was postero-lateral in all patients. Harris Hip Score (HHS), WOMAC, ROM and radiographs were evaluated preoperatively, at 6-months, and yearly thereafter.
Results
Mean follow-up was 6 yrs (SD 1.7). Mean radiographic follow-up was 5.2 yrs (SD 1.2). Radiographs were available for 83 hips. Mean HHS improved from 43 preoperative (range 15–68) to 98 (range 86-100, p < 0.0001). Mean WOMAC score improved from 56 (range 15-94) to 12 (range 0-63, p < 0.0001). Flexion improved from 95° (range 50-115) to 102° (range 90-120, p < 0.0001). Complications included trochanteric fx (6 mo) without component removal, traumatic femoral Fx (40 days) with stem replacement, and one dislocation. No other device related adverse events were reported. No peri-acetabular osteolysis was observed. Six year survival was 100% for the acetabular shell/modular metal liner combination.
Conclusion
Excellent mid-term results were obtained in a young, active cohort treated with modular MoM THA. No AVAL, pseudotumor, unexplained pain or other complication attributable to wear debris or the MoM articulation was observed. These findings indicate that THA with the Pinnacle(tm) modular MoM bearing performs well in a high demand population at mid term follow-up.
