Developmental dysplasia of the hip (DDH) and femoroacetabular impingement (FAI) are common hip pathologies and important risk factors for osteoarthritis, yet the disease mechanisms differ. DDH involves deficient femoral head coverage and a shortened abductor moment arm, so this study hypothesized that the cross-sectional area (CSA) of the gluteus medius/minimus muscle complex and the stabilizing iliocapsularis muscle would be larger in DDH versus FAI, without increased fatty infiltration. A longitudinal cohort identified prearthritic patients with DDH or FAI who underwent imaging before surgery. Patients with DDH and FAI (Cam, Pincer, or Mixed) were 1:1 matched based on age, sex, and body mass index. Magnetic resonance imaging was used to measure the gluteus medius/minimus complex and iliocapsularis in two transverse planes. Amira software was used to quantify muscle and noncontractile tissue. Paired samples t-tests were performed to compare muscle size and composition (p < 0.05). There were no differences in the iliocapsularis muscle. Patients with DDH had significantly larger CSA of the gluteus medius/minimus complex at both transverse planes, and the noncontractile tissue proportion did not differ. The mean difference in overall muscle CSA at the anterior inferior iliac spine was 4.07 ± 7.4 cm² (p = 0.005), with an average difference of 12.1%, and at the femoral head this was 2.40 ± 4.37 cm² (p = 0.004), with an average difference of 20.2%. This study reports a larger CSA of the gluteus medius/minimus muscle complex in DDH compared to FAI, without a difference in noncontractile tissue, indicating increased healthy muscle in DDH.

中文翻译：

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髋关节发育不良与股骨髋臼撞击的关节炎前期患者的髋关节外展肌尺寸更大

发育性髋关节发育不良 (DDH) 和股骨髋臼撞击 (FAI) 是常见的髋关节病变和骨关节炎的重要危险因素，但疾病机制不同。DDH 涉及股骨头覆盖不足和外展肌力臂缩短，因此本研究假设 DDH 与 FAI 相比，臀中肌/臀小肌复合体和稳定髂关节囊肌的横截面积 (CSA) 会更大，而不会增加脂肪浸润。一项纵向队列确定了患有 DDH 或 FAI 的关节炎前期患者，他们在手术前接受了影像学检查。DDH 和 FAI（Cam、Pincer 或混合）患者根据年龄、性别和体重指数进行 1:1 匹配。磁共振成像用于测量两个横向平面中的臀中肌/臀小肌复合体和髂关节囊肌。Amira 软件用于量化肌肉和非收缩组织。配对样本进行t检验以比较肌肉大小和成分 ( p  < 0.05)。髂关节囊肌没有差异。DDH 患者在两个横向平面上的臀中肌/臀小肌复合体的 CSA 明显更大，非收缩组织比例没有差异。髂前下棘整体肌肉 CSA 的平均差异为 4.07 ± 7.4 cm ² ( p  = 0.005)，平均差异为 12.1%，在股骨头处为 2.40 ± 4.37 cm ² ( p = 0.004)，平均差异为 20.2%。这项研究报告了与 FAI 相比，DDH 中臀中肌/臀小肌复合体的 CSA 更大，非收缩组织没有差异，表明 DDH 中健康肌肉增加。