Radiologic Correlation Between the Ischiofemoral Space and Morphologic Characteristics of the Hip in Hips With Symptoms of Dysplasia.

OBJECTIVE: The purpose of this study was to investigate radiologic correlation between the ischiofemoral space and morphologic findings in the hip in patients with symptomatic developmental dysplasia of the hip (DDH), borderline DDH, and femoroacetabular impingement (FAI).

MATERIALS AND METHODS: In 84 patients undergoing hip arthroscopic surgery, 108 hips were divided into three groups according to lateral center-edge angle (LCEA): DDH group (LCEA < 20°; 18 hips), borderline DDH group (20° ≤ LCEA < 25°; 26 hips), and FAI group (LCEA ≥ 25°; 64 hips). Ischiofemoral distance was evaluated by radiography and ischiofemoral space and quadratus femoris space by MRI. Software was used to measure the radiographic parameters LCEA, femoral neck-shaft angle, and femoral neck anteversion on preoperative CT scans.

RESULTS: Ischiofemoral distance, ischiofemoral space, and quadratus femoris space were significantly smaller in the DDH and borderline DDH groups than in the FAI group. The prevalence of hips with ischiofemoral space < 17 mm was significantly higher in the DDH (10 of 18 patients [56%]) and borderline DDH (8 of 26 patients [31%]) groups than in the FAI group (4 of 64 patients [6%]). In addition, the prevalence of hips with a quadratus femoris space < 8 mm was significantly higher in the DDH (2 of 18 patients [11%]) and borderline DDH (3 of 26 patients [12%]) groups than in the FAI (0 of 64 patients [0%]) group. Femoral neck-shaft angle and femoral neck anteversion were significantly greater in the DDH group than in the FAI group.

CONCLUSION: Ischiofemoral impingement syndromes can be considered more likely in patients with DDH than in those with FAI.