University of Pennsylvania, Philadelphia, PA, USA.
Clin Orthop Relat Res. 2013 Aug;471(8):2484-91. doi: 10.1007/s11999-013-2809-x.
Incomplete correction of femoral offset and sphericity remains the leading cause for revision surgery for symptomatic femoroacetabular impingement (FAI). Because arthroscopic exploration is technically difficult, a detailed preoperative understanding of morphology is of paramount importance for preoperative decision-making.
QUESTIONS/PURPOSES: The purposes of this study were to (1) characterize the size and location of peak cam deformity with a prototype CT-based software program; (2) compare software alpha angles with those obtained by plain radiograph and CT images; and (3) assess whether differences can be explained by variable measurement locations.
We retrospectively reviewed the preoperative plain radiographs and CT scans of 100 symptomatic cam lesions treated by arthroscopy; recorded alpha angle and clockface measurement location with a novel prototype CT-based software program, CT, and Dunn lateral plain radiographs; and used ordinary least squares regressions to assess the relationship between alpha angle and measurement location.
The software determined a mean alpha angle of 70.8° at 1:23 o'clock and identified 60% of maximum alpha angles between 12:45 and 1:45. The CT and plain radiographs underestimated by 5.7° and 8.2°, respectively. The software-based location was anterosuperior to the mean CT and plain radiograph measurement locations by 41 and 97 minutes, respectively. Regression analysis confirmed a correlation between alpha angle differences and variable measurement locations.
Software-based three-dimensional (3-D) imaging generated alpha angles larger than those found by plain radiograph and CT, and these differences were the result of location of measurement. An automated 3-D assessment that accurately describes the location and topography of FAI may be needed to adequately characterize preoperative deformity.
股骨偏心距和球形度的不完全矫正仍然是髋关节撞击综合征（FAI）症状性翻修手术的主要原因。由于关节镜检查在技术上具有挑战性，因此术前详细了解形态对于术前决策至关重要。
问题/目的：本研究的目的是：（1）使用基于 CT 的原型软件程序描述凸轮畸形的大小和位置；（2）比较软件 α 角与普通 X 线片和 CT 图像获得的 α 角；（3）评估测量位置的差异是否可以解释。
我们回顾性地分析了 100 例接受关节镜治疗的有症状凸轮病变患者的术前普通 X 线片和 CT 扫描；使用新型基于 CT 的原型软件程序、CT 和 Dunn 侧位普通 X 线片记录 α 角和时钟面测量位置；并使用普通最小二乘法回归评估 α 角与测量位置之间的关系。
软件确定的平均 α 角为 1 点 23 分，最大 α 角的 60%在 12 点 45 分至 1 点 45 分之间。CT 和普通 X 线片分别低估了 5.7°和 8.2°。基于软件的位置比 CT 和普通 X 线片的平均测量位置分别在前上方向上靠前 41 分钟和 97 分钟。回归分析证实了 α 角差异与可变测量位置之间的相关性。
基于软件的三维（3-D）成像生成的 α 角大于普通 X 线片和 CT 发现的 α 角，这些差异是由于测量位置的不同。可能需要一种自动的 3-D 评估来准确描述 FAI 的位置和形态，以充分描述术前畸形。
