Magnetic Resonance Imaging Findings of Ischiofemoral Impingement in Patients With Inflammatory Myositis: An Observational Study.

OBJECTIVE: To determine the frequency of magnetic resonance imaging (MRI) findings of ischiofemoral impingement (IFI) in patients with inflammatory myositis (IM) and associated factors.

METHODS: Pelvis and thigh MRI studies of 314 consecutive patients (57% women; mean age, 55.5 years; range, 18-85) with suspected muscle disease were reviewed.

RESULTS: Ischiofemoral impingement at MRI was present in 11% of patients with a final diagnosis of IM and in 2% of patients with an alternative diagnosis (P = 0.008). In multiple logistic regression analysis, IM, but not age or sex, was independently associated with IFI at MRI (odds ratio, 5.18; 95% confidence interval, 1.19-22.6; P = 0.028). Fatty atrophy of hip stabilizing muscles was independently associated with IFI at MRI (odds ratio per unit increase of fatty atrophy score, 1.03; 95% confidence interval, 1.01-1.05; P = 0.0007).

CONCLUSIONS: Magnetic resonance imaging findings of IFI are present in 11% of IM patients and are independently associated with fatty atrophy of hip stabilizing muscles.