Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, De Pintelaan 185, 9000, Ghent, Belgium.
Skeletal Radiol. 2011 Jul;40(7):921-7. doi: 10.1007/s00256-010-1021-2. Epub 2010 Aug 18.
The description of femoral head sphericity and related risk for femoroacetabularimpingement is currently limited to an angular estimate-the alpha angle-whose relevance and accuracy have been challenged. We developed a three-dimensional approach for both automated digital measurement of the alpha angle and the detection of camdeformities. Accuracy and diagnostic relevance of the alpha angle estimated by means of the oblique axial and multiple radial plane protocol were compared with the computed results.
Using subject-specific statistical information of the femur head and mid-neck region, a method was developed to accurately compute the maximum alpha angle and to define aspherical eccentric areas at the femoral head-neck junction. The method was evaluated on 102 dry cadaver femur specimens.
Average detection limit for bony prominences at the head-neck transition was 0.98 mm. Pixel size of the investigated CT data was 0.79 mm. Mean maximum computed alpha angle of the femurs with cam-type morphology as identified by the morphological method was 67.72° (range 53.04-88.02°). Mean maximum computed alpha angle of the femurs without cam deformity was 47.65° (range 38.67-59.81°). Alpha angle estimates obtained by means of the multiple radial plane protocol correlated better (R = 0.88) and showed higher diagnostic agreement (phi = 0.77) with the 3D computational analysis compared to the oblique axial protocol (R = 0.60; phi = 0.67).
The alpha angle seems to be a relevant screening tool when obtained by 3D computed analysis or when estimated according to the multiple radial plane protocol. Estimates obtained by means of the oblique axial protocol have insufficient diagnostic and measurement accuracy.
目前，对于股骨头球形度的描述以及相关的股骨髋臼撞击症风险仅限于角度估计——α角，但其相关性和准确性受到了挑战。我们开发了一种三维方法，用于自动数字化测量α角和检测凸轮畸形。比较了通过斜轴位和多个放射状平面方案估计的α角的准确性和诊断相关性与计算结果。
利用股骨头部和中颈区域的特定于个体的统计信息，开发了一种方法来准确计算最大α角，并定义股骨头颈交界处的非球形偏心区域。该方法在 102 个干尸股骨标本上进行了评估。
骨突起在头颈交界处的平均检测极限为 0.98mm。研究 CT 数据的像素大小为 0.79mm。通过形态学方法识别的凸轮型形态股骨的计算最大α角平均值为 67.72°（范围 53.04-88.02°）。无凸轮畸形股骨的计算最大α角平均值为 47.65°（范围 38.67-59.81°）。与斜轴位方案相比，通过多个放射状平面方案获得的α角估计相关性更好（R=0.88），诊断一致性更高（phi=0.77），与三维计算分析相比（R=0.60；phi=0.67）。
通过三维计算分析或根据多个放射状平面方案获得的α角似乎是一种相关的筛选工具。通过斜轴位方案获得的估计值的诊断和测量准确性不足。
