The accuracy assessment of ultrasound for the diagnosis of ischiofemoral space - A Validation Study.

To investigate and evaluate the accuracy of ultrasound (US) imaging for measurement of ischiofemoral space (IFS) compared with magnetic resonance imaging (MRI). Twenty-five hips of 16 patients with hip pain and ipsilateral quadratus femoris muscle (QFM) edema were recruited to the IFI group, and 19 hips of 19 patients without hip pain and QFM edema were recruited as the control group. IFS of both groups was measured by US and MRI. The correlations and differences between US and MRI measurements were then assessed. Last, the receiver operating characteristic (ROC) data analysis was performed. The US results revealed a decreased IFS in IFI hips compared with controls (P < 0.001), suggesting that US were valuable in identifying IFI. IFS measured by US and MRI showed positive correlations in both the IFI group (r = 0.409, P = 0.042) and control group (r = 0.575, P = 0.01). There were no statistically significant differences between IFS measured by US and MRI in the control group (P = 0.657), while IFS measurements in the IFI group performed with US were significantly greater than those with MRI (P < 0.001). ROC curve analysis revealed that the cutoff value of IFS measured with US was 2.14 cm, with a sensitivity of 92.0% and specificity of 68.4%, while measured by MRI was 1.87 cm, with a sensitivity of 96.0% and specificity of 84.2%. IFS measurements obtained with US are very similar to those obtained with MRI. Therefore, US provides a low-cost and easy-to-operate alternative imaging modality to measure IFS.