Brunner A, Hamers A T, Fitze M, Herzog R F
Department of Orthopaedic Surgery, The Cantonal Hospitals Lucerne, Eichenweg, 6010 Wolhusen, Switzerland.
J Bone Joint Surg Br. 2010 Sep;92(9):1203-8. doi: 10.1302/0301-620X.92B9.24410.
The beta-angle is a radiological tool for measuring the distance between the pathological head-neck junction and the acetabular rim with the hip in 90 degrees of flexion in patients with femoroacetabular impingement. Initially it was measured using an open-chamber MRI. We have developed a technique to measure this angle on plain radiographs. Correlation analysis was undertaken to determine the relationship between the range of movement and the beta-angle in 50 patients with femoroacetabular impingement and 50 asymptomatic control subjects. Inter- and intra-observer reliability of the beta-angle was also evaluated. Patients with femoroacetabular impingement had a significantly smaller (p < 0.001) mean beta-angle (15.6 degrees, 95% confidence interval (CI) 13.3 to 17.7) compared with the asymptomatic group (38.7 degrees, 95% CI 36.5 to 41.0). Correlation between internal rotation and the beta-angle was high in the impingement group and moderate in the asymptomatic group. The beta-angle had excellent inter- and intra-observer reliability in both groups. Our findings suggest that the measurement of the beta-angle on plain radiography may represent a valid, reproducible and cost-effective alternative to open MRI in the assessment of the pathological bony anatomy in patients with cam, pincer and mixed femoroacetabular impingement.
β角是一种放射学工具，用于测量股骨髋臼撞击症患者髋关节屈曲90度时病理性头颈交界处与髋臼边缘之间的距离。最初是使用开放式磁共振成像（MRI）进行测量的。我们已经开发出一种在普通X线片上测量该角度的技术。对50例股骨髋臼撞击症患者和50例无症状对照者进行了相关性分析，以确定活动范围与β角之间的关系。还评估了β角在观察者间和观察者内的可靠性。与无症状组（38.7度，95%置信区间（CI）36.5至41.0）相比，股骨髋臼撞击症患者的平均β角明显更小（p < 0.001）（15.6度，95%CI 13.3至17.7）。撞击组内旋与β角之间的相关性较高，无症状组则为中度相关。β角在两组中均具有出色的观察者间和观察者内可靠性。我们的研究结果表明，在评估凸轮型、钳夹型和混合型股骨髋臼撞击症患者的病理性骨解剖结构时，普通X线片上β角的测量可能是一种有效、可重复且经济高效的替代开放式MRI的方法。
