MRI of aseptic lymphocytic vasculitis-associated lesions in metal-on-metal hip replacements.

OBJECTIVE: The aim of this review is to describe the clinical, histopathologic, and MRI features of aseptic lymphocytic vasculitis-associated lesions in total hip replacements. CONCLUSION: The introduction of modern metal-on-metal hip arthroplasty has been accompanied by a newly described disease, aseptic lymphocytic vasculitis-associated lesions, which is characterized histologically by bland necrosis and dense perivascular lymphocytic infiltrates. Conventional radiographic findings are often normal, but the typical MRI findings include periprosthetic fluid collections, soft-tissue masses, gluteal tendon avulsion, bone loss, periosteal stripping, neurovascular involvement, and periprosthetic fractures. The severity of the histologic and MRI appearances can be graded according to defined published criteria.

Grading the severity of soft tissue changes associated with metal-on-metal hip replacements: reliability of an MR grading system.

INTRODUCTION: Metal-on-metal (MoM) soft tissue reactions or aseptic lymphocytic vasculitis-associated lesions (ALVAL) are being recognised using metal artefact reduction (MAR) MR with increasing frequency following the advent of second generation metal-on-metal bearings, but there is no standardised technique for reporting of MR appearances in this disease. The aim of this study was to measure the reliability of a grading system designed for scoring the severity of MoM disease on MRI. MATERIALS AND METHODS: MRI examinations of 73 hips in 59 patients were retrospectively selected and then anonymised, randomised and reviewed by three independent observers (musculoskeletal radiologists). Each MR examination was scored as either A: normal, B: infection, C1: mild MoM disease, C2: moderate MoM disease or C3: severe MoM disease according to pre-defined criteria. Kappa correlation statistics were used to compare the observations. RESULTS: There was substantial agreement among all three observers; the correlation coefficient between the two most experienced observers was κ = 0.78 [95% confidence intervals (CI): 0.68-0.88] and when compared with the least experienced observer coefficients were κ = 0.69 (95% CI: 0.57-0.80) and κ = 0.66 (95% CI: 0.54-0.78). The strongest correlation occurred for grades A, C2 and C3. The weakest correlations occurred for grades B and C1. CONCLUSION: The grading system described in this study is reliable for evaluating ALVAL in MoM prostheses using MR but is limited in differentiating mild disease from infection.