Background: Clinically, understanding how the soft tissue envelope adapts to various forms of hip dysfunction could enhance both surgical and nonsurgical management. Very few studies have looked at soft tissue structures as preoperative discriminators between varying underlying etiologies of hip conditions.
Purpose: To demonstrate that the magnetic resonance arthrography assessment of soft tissue structures of the hip will preoperatively differ in patients with different underlying hip joint diseases.
Methods: Fifty-seven patients who underwent preoperative magnetic resonance arthrography and corrective hip surgery were retrospectively identified yielding 3 groups: 17 with developmental dysplasia of the hip (DDH) (11 F, 6 M; mean age 35.1 years, range 19.6-53.6); 20 with isolated labral tears (LTs) (17 F, 3 M; mean age 38.4 years, range 15.2-62.1), and 20 with cam-type femoroacetabular impingement (FAI) (11 F, 9 M; mean age 38.8 years, range 18.9-51.2). Measurements of the hip labral length, capsule thickness, and psoas, rectus femoris, and gluteal muscle dimensions were performed, with normalization of the values for statistical analysis.
Results: The superior labral length was significantly greater in the DDH group [normalized value (NV): 0.30] compared with the FAI group (NV: 0.25, P < 0.05). In addition, the superior (12 o'clock) capsular thickness (NV: 0.24) was significantly greater compared with the LT group (NV: 0.15, P < 0.05) and the FAI group (NV: 0.16, P < 0.05). The DDH group also had a significantly greater anterior (3 o'clock) capsular thickness (NV: 0.18) compared with the LT group (NV: 0.13, P < 0.05). The transverse dimension of the rectus femoris was larger in the DDH group (NV: 1.39) compared with the FAI group (NV: 1.14, P < 0.05).
Conclusion: An enlarged rectus femoris and thicker hip capsule as well as an enlarged labrum are characteristic findings in hip dysplasia.
Level of evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.