Department of Radiology, Charité, Medical School, Humboldt-Universität zu Berlin, Germany.
Eur J Radiol. 2012 May;81(5):928-33. doi: 10.1016/j.ejrad.2011.01.113. Epub 2011 Feb 26.
Magnetic resonance imaging (MRI) is one of the most widely used noninvasive diagnostic modalities for musculoskeletal evaluation. We conducted a retrospective study to determine whether MRI of the hip joint abductor and external rotator muscles yields reproducible findings in patients after total hip arthroplasty (THA).
MR images were obtained 12 months after THA in 10 patients and were analyzed by two independent, blinded observers. The images were analyzed on workstations with three-dimensional analysis capabilities. The readers evaluated the gluteus medius, gluteus minimus, and obturator externus muscles on the nonoperated side (NOS) and the THA side. For each of the three muscles, the readers analyzed the cross-sectional area, cross-sectional signal intensity, intensity in a region of interest (ROI), and volume on both sides.
Unlike intraobserver variability, interobserver variability showed significant differences between the measurements for some abductor and external rotator muscles, especially for volume (p<0.001-0.02) and cross-sectional area (p<0.001-0.05) analysis of the gluteus medius and minimus muscles on the THA side but also on the NOS. There were no differences in signal intensity in the ROI (p=0.29-0.83). The coefficients of variation (CoV) of all 4 parameters quantified were lower on the NOS (average, 5.9%) than on the THA side (average, 7.3%). Analysis of the gluteus minimus muscle volume showed both higher intraobserver (18.8%) and interobserver (13.9%) variability on the THA side.
MRI is an accurate and reliable test for evaluation of soft tissue structures in patients who have undergone THA. MRI evaluation of abductor muscles yields reproducible results on the THA side and on the NOS. Prosthesis artifacts limit evaluation of the gluteus minimus muscle on the THA side and cannot be recommended. Since interobserver variability was always higher than intraobserver variability, follow-up examinations should ideally be performed by the same reader in order to obtain clinically meaningful results.
磁共振成像（MRI）是用于评估肌肉骨骼系统的最广泛使用的非侵入性诊断方法之一。我们进行了一项回顾性研究，以确定髋关节外展肌和外旋肌的 MRI 是否能在全髋关节置换术（THA）后患者中产生可重复的结果。
在 10 例患者 THA 后 12 个月获取 MRI 图像，并由两位独立的、盲目的观察者进行分析。图像在具有三维分析功能的工作站上进行分析。读者评估了对侧（NOS）和 THA 侧的臀中肌、臀小肌和外旋肌。对于这三个肌肉，读者分析了双侧的横截面积、横截面积信号强度、感兴趣区域（ROI）的强度和体积。
与观察者内变异性不同，观察者间变异性显示，对于一些外展肌和外旋肌，特别是臀中肌和臀小肌的 THA 侧和 NOS 的体积（p<0.001-0.02）和横截面积（p<0.001-0.05）分析，存在显著差异。在 ROI 中的信号强度没有差异（p=0.29-0.83）。所有 4 个参数的变异系数（CoV）在 NOS 侧（平均 5.9%）均低于 THA 侧（平均 7.3%）。臀小肌体积分析显示，THA 侧的观察者内（18.8%）和观察者间（13.9%）变异性均较高。
MRI 是一种准确可靠的测试方法，可用于评估接受 THA 的患者的软组织结构。对髋关节外展肌的 MRI 评估在 THA 侧和 NOS 侧均可产生可重复的结果。假体伪影限制了 THA 侧臀小肌的评估，因此不建议使用。由于观察者间变异性始终高于观察者内变异性，为了获得有临床意义的结果，理想情况下应由同一位读者进行随访检查。
