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.