Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, NIHR Biomedical Research Unit, University of Oxford, and Nuffield Orthopaedic Centre NHS Trust, Headington, Oxford, UK.
Acta Orthop. 2010 Feb;81(1):134-41. doi: 10.3109/17453671003619011.
Most patients with femoroacetabular impingement (FAI) have a cam deformity, which may be quantified by measuring the alpha angle and anterior offset ratio (AOR). Knowledge of what constitutes a "normal" alpha angle and AOR is limited. We defined the reference intervals of these measurements from normal hips in the general population.
157 individuals from the general population were reviewed clinically and radiographically. 74 individuals with clinical evidence of hip disease or radiographic evidence of osteoarthritis (OA) were excluded, leaving a study group of 83 individuals (mean age 46 (22-69) years, 44 females) with normal hips. The alpha angles and AORs were measured from cross-table lateral radiographs taken in 15 degrees internal rotation. A validation study consisting of a cadaver study and a measurement reliability study was also performed.
The mean alpha angle was 48 degrees in men and 47 degrees in women. The mean AOR was 0.19, the same in men and women. Thus, sexes were combined to derive 95% confidence intervals for the population mean alpha angle (46-49 degrees ) and AOR (0.18-0.20). The 95% reference interval for the alpha angle was 32-62 degrees degrees, and for the AOR it was 0.14-0.24. The validation study confirmed that these measurements were resistant to a reasonable degree of variation in positioning and that the repeatability and reproducibility of the measurements was good.
These reference intervals indicate that clinically and radiographically normal hips may have alpha angles and AORs that have previously been considered "abnormal". The thresholds provided by this study will aid classification of individuals involved in longitudinal studies of FAI and OA, and may be of use to the practicing clinician in evaluating the young adult with hip pain.
大多数患有股骨髋臼撞击症（FAI）的患者存在凸轮畸形，可通过测量阿尔法角和前向偏移比（AOR）来量化。关于什么构成“正常”的阿尔法角和 AOR 的知识有限。我们从普通人群中的正常髋关节中定义了这些测量值的参考区间。
对 157 名普通人群进行了临床和影像学检查。排除了 74 名有髋关节疾病临床证据或影像学证据的骨关节炎（OA）患者，留下了 83 名（平均年龄 46（22-69）岁，44 名女性）正常髋关节的研究组。阿尔法角和 AOR 是从 15 度内旋的交叉桌侧位片上测量的。还进行了一项验证研究，包括尸体研究和测量可靠性研究。
男性的平均阿尔法角为 48 度，女性为 47 度。男性和女性的平均 AOR 均为 0.19。因此，为了得出人群平均阿尔法角（46-49 度）和 AOR（0.18-0.20）的 95%置信区间，将男女合并。阿尔法角的 95%参考区间为 32-62 度，AOR 的参考区间为 0.14-0.24。验证研究证实，这些测量值在一定程度上能够抵抗定位的变化，并且这些测量值的重复性和再现性良好。
这些参考区间表明，临床上和影像学上正常的髋关节可能具有先前被认为“异常”的阿尔法角和 AOR。本研究提供的阈值将有助于对参与 FAI 和 OA 纵向研究的个体进行分类，并且对于评估年轻的髋关节疼痛患者的临床医生可能有用。
