Usefulness of false profile view for screening of ischiofemoral impingement

Abstract

Purpose: The ischiofemoral impingement is an easily overlooked disease due to its low incidence, which is mainly diagnosed by expensive magnetic resonance image (MRI). The purpose of this study was to evaluate the usefulness of false profile view as a screening test for ischiofemoral impingement. Materials and Methods: From June 2013 to July 2017, 58 patients diagnosed with ischiofemoral impingement were enrolled. 58 patients who matched age, gender and BMI in pairs using propensity score were included as a control group. We measured the ischiofemoral space (IFS) the shortest distance between the lateral cortex of the ischium and the medial cortex of lesser trochanter in weight bearing hip anteroposterior (AP) view and false profile view. The IFS and quadratus femoris space (QFS) were also measured with MRI. The receiver operating characteristics (ROC), area under the ROC curve (AUC) and cutoff point of the IFS were measured on false profile images, and the correlation between the IFS and QFS was analyzed in the MRI scans. Results: In the false profile view and hip AP view, IFS was significantly decreased in the ischiofemoral impingement (P < 0.01). In the false profile view, ROC AUC (0.967) was higher than in the hip AP view (0.841). Cutoff value for differential diagnosis of IFI in the false profile view was 10.3 mm (sensitivity 88.2%, specificity 88.4%). IFS was correlated with IFS (r=0.744) QFS (0.740) in MRI and IFS (0.621) in hip AP view (p < 0.01). Conclusion: False profile view of the hip is considered to be useful for the screening of ischiofemoral impingement before the MRI.