The Retrieval Study of the Rough Blasted Surface Finish Cement Stem in Metal on Metal Total Hip Arthroplasty

ABSTRACT

PURPOSE: This study investigated the possible etiologic role of stem loosening and osteolysis by examining the surface of a rough blast retrieval cement stem and physical activity in second generation metal-on-metal (MOM) total hip arthroplasty (THA) MATERIALS AND METHODS: Forty one patients (43 hips) were analyzed retrospectively from Jan. 1996 to Dec.1998. Of the femoral stem, a rough blasted (Ra=1.6 um) cement stem and a cementless Ti-alloy stem was used in 18 and 25 hips, respectively. The mean follow-up duration was 10.15 years. Each patient was evaluated clinically by the HSS and radiographically by Engh's method. Scanning electron microscopy was used to observe the retrieved femoral stem and histology studies were performed. RESULTS: The mean Harris hip score improved from 56.2 points before surgery to 92.6 points after surgery. All the cementless stems and cups showed excellent results at the last follow-up. Eight of the rough blast cement stems were revised. Seven showed loosening and one was a recurrent dislocation. Cross-validation evaluation revealed osteolysis to be associated with a rough surface cement stem of metal on metal THAs (p=0.001). In addition, patients who underwent strenuous activity had a higher incidence of osteolysis (p=0.031). CONCLUSION: These findings suggest that a rough blast surface cement stem is associated with early osteolysis and loosening in patients with a metal-on-metal hip replacement. A prospective study with a large group of patients and multiple diagnostic methods will be needed to determine if there is a causal relationship between metal hypersensitivity and osteolysis. These results suggest that a cement stem with a rough blasted surface should be considered in metal-on-metal total hip arthroplasty.