Objective: The purpose of this study is to correlate the MRI finding of quadratus femoris edema in children with established measures of ischiofemoral impingement in adults and to determine their clinical significance.
Materials and methods: A case-control retrospective review was performed of MR images of 12 hips of nine children (mean age, 10 years) that showed abnormal signal intensity in the quadratus femoris muscle. The findings were compared with those for 13 hips in 13 control subjects (mean age, 9.8 years). Two musculoskeletal radiologists independently measured the ischiofemoral space, quadratus femoris space, inclination angle, and hamstring tendon area. Quadratus femoris muscle edema, tears, or fatty replacement were assessed visually. Statistical analysis determined inter- and intraobserver variability and statistical differences between the two subject groups.
Results: Subjects with abnormal signal in the quadratus femoris muscle had a statistically significantly narrower ischiofemoral space (mean, 11.5 vs 20.7 mm; p < 0.05) and quadratus femoris space (mean, 7.2 vs 14.3 mm, p < 0.05) compared with control subjects. Inclination angles were statistically significantly larger in affected subjects (145.5° vs 138.7°; p < 0.05). No statistically significant difference was found in hamstring tendon area. Four of 12 patient hips had no symptoms or symptoms unrelated to the abnormality. Inter- and intraobserver variability scores were strong for all continuous variables.
Conclusion: Ischiofemoral impingement is a cause of hip pain in children and should be considered with the combination of quadratus femoris muscle edema and narrowing of ischiofemoral space and quadratus femoris space. Coxa valga may contribute to narrowing of these parameters and predispose to ischiofemoral impingement. The MRI features of ischiofemoral impingement, however, are nonspecific and may be seen in patients with pain localized to that hip or in patients with symptoms unrelated to the abnormality.
Keywords: ischiofemoral impingement; ischiofemoral space; quadratus femoris edema.