Raji Yazdan, Pierre Kinsley J, Wagle Sagar, Pham Nicole S, Boutin Robert D, Safran Marc R
Department of Orthopaedic Surgery, Stanford University School of Medicine, Redwood City, California, USA.
Department of Radiology, Stanford University School of Medicine, Stanford, California, USA.
Am J Sports Med. 2025 Jul;53(9):2181-2188. doi: 10.1177/03635465251344600. Epub 2025 Jun 12.
Iliocapsularis (IC) muscle hypertrophy in borderline developmental dysplasia of the hip (BDDH) and developmental dysplasia of the hip (DDH) suggests a possible role as a dynamic hip stabilizer. However, its significance in hip microinstability (MI) without acetabular undercoverage remains unclear.
To compare IC muscle dimensions and fatty infiltration between patients with MI, BDDH, and mixed-type femoroacetabular impingement (mFAI), and assess the association between IC muscle morphology and hip pathology.
Case-control study; Level of evidence, 4.
A retrospective analysis was conducted on patients undergoing arthroscopic surgery for hip pathology between January 2014 and December 2022. Patients were categorized based on lateral center-edge angle (LCEA) into BDDH (18° to <25°), MI (25° to 39°), and mFAI (>39°) groups. Preoperative radiographs and magnetic resonance imaging (MRI) scans were reviewed, and IC muscle dimensions, including width, depth, cross-sectional area (CSA), IC fatty infiltration, and combined IC and iliopsoas (IP) (IC+IP) CSA, were measured by 3 independent observers. A priori power analysis was performed. Statistical analyses included parametric and nonparametric comparative tests, interobserver correlation coefficients, and receiver operating characteristic analysis.
A total of 95 hips were included in this study. IC depth, width, and CSA and IC+IP CSA were significantly smaller in the MI group ( < .05 for all). Interobserver agreement was good to excellent for IC width (IRC, 0.87), IC CSA (IRC, 0.87), and IC+IP CSA (IRC, 0.96), but poor for IC depth (IRC, 0.26). The alpha angle did not significantly differ among groups ( = .093). The MI group had a higher proportion of female patients ( = .003). No significant differences were noted in radiographic markers, including the ischial spine sign ( = .083), crossover sign ( = .130), and posterior wall sign ( = .41).
No detectable IC hypertrophy was observed in the MI group compared with the BDDH and mFAI groups, with patients with MI showing smaller IC width, depth, and CSA. The study offers a reproducible measurement technique with good interobserver agreement. IC muscle mass has limited prognostic value in predicting hip MI.
在髋关节临界发育不良（BDDH）和发育性髋关节发育不良（DDH）中，髂关节囊肌（IC）肥大表明其可能作为髋关节动态稳定器发挥作用。然而，其在髋臼覆盖正常的髋关节微不稳定（MI）中的意义仍不明确。
比较MI、BDDH和混合型股骨髋臼撞击症（mFAI）患者的IC肌尺寸和脂肪浸润情况，并评估IC肌形态与髋关节病理之间的关联。
病例对照研究；证据等级，4级。
对2014年1月至2022年12月期间因髋关节疾病接受关节镜手术的患者进行回顾性分析。根据外侧中心边缘角（LCEA）将患者分为BDDH组（18°至<25°）、MI组（25°至39°）和mFAI组（>39°）。回顾术前X线片和磁共振成像（MRI）扫描，由3名独立观察者测量IC肌尺寸，包括宽度、深度、横截面积（CSA）、IC肌脂肪浸润以及IC肌与髂腰肌（IP）联合横截面积（IC+IP CSA）。进行了先验功效分析。统计分析包括参数和非参数比较检验、观察者间相关系数以及受试者工作特征分析。
本研究共纳入95个髋关节。MI组的IC肌深度、宽度、CSA以及IC+IP CSA均显著更小（均P<0.05）。观察者间对IC肌宽度（组内相关系数[IRC]，0.8）、IC肌CSA（IRC，0.87）和IC+IP CSA（IRC，0.96）的一致性良好至优秀，但对IC肌深度的一致性较差（IRC，0.26）。各组间α角无显著差异（P=0.093）。MI组女性患者比例更高（P=0.003）。在坐骨棘征（P=0.083）、交叉征（P=0.130）和后壁征（P=0.41）等影像学指标上未观察到显著差异。
与BDDH组和mFAI组相比，MI组未观察到明显的IC肌肥大，MI组患者的IC肌宽度、深度和CSA更小。本研究提供了一种具有良好观察者间一致性的可重复测量技术。IC肌质量在预测髋关节MI方面的预后价值有限。
