MRI Findings in Patients with Unexplained Pain Following Metal-On-Metal Total Hip Arthroplasty and Hip Resurfacing Arthroplasty

Catherine L. Hayter¹, Matthew F. Koff¹, Stephanie L. Gold¹, Giorgio Perino², Kevin M. Koch³, Hollis G. Potter¹

Metal on metal (MOM) prostheses may be complicated by aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL), which can manifest as synovitis or osteolysis. The purposes of this study were to review patterns of synovitis and osteolysis in subjects with pain following MOM hip resurfacing arthroplasty (RSA) and MOM total hip arthroplasty (THA) and correlate the MRI findings with results at revision surgery. Synovitis was present in 77% of RSA and 86% of THA hips. Mean synovial volume was higher in the THA group; however, this did not reach significance (p=0.18). There was no difference in the incidence of osteolysis (p=0.17), synovitis (p=0.51) or extracapsular disease (p=0.67) between the two groups. 20 subjects underwent revision surgery, of which 12 were diagnosed with ALVAL. Subjects with ALVAL had a significantly higher mean volume of synovitis (p=0.04) compared to those without ALVAL. Extracapsular disease and muscle edema were only detected in subjects with ALVAL. MRI is a useful assessment tool in patients with pain following MOM hip arthroplasty. MRI can detect synovitis, extracapsular disease and osteolysis, which may indicate ALVAL at revision surgery. Early results suggest that the most reliable MRI signs of ALVAL are extracapsular disease, high volumes of synovitis and intramuscular edema.