MSK Laboratory, Imperial College London, Charing Cross Hospital, London, UK.
Skeletal Radiol. 2013 Mar;42(3):329-33. doi: 10.1007/s00256-012-1459-5. Epub 2012 Jun 8.
Cam hips are commonly quantified using the two-dimensional α angle. The accuracy of this measurement may be affected by patient position and the technician's experience. In this paper, we describe a method of measurement that provides a quantitative definition of cam hips based upon three-dimensional computed tomography (CT) images.
CT scans of 47 (24 cam, 23 normal) femurs were segmented. A sphere was fitted to the articulating surface of the femoral head, the radius (r) recorded, and the femoral neck axis obtained. The cross sectional area at four locations spanning the head neck junction (r/4, r/2, 3r/4 and r), perpendicular to the neck axis, was measured. The ratios (Neck/Head) between the areas at each cut relative to the surface area at the head centre were calculated and aggregated.
Normal and cam hips were significantly different: the sum of the head-neck ratios (HNRs) of the cam hips were always smaller than normal hips (p < 0.01). A cut off point of 2.55 with no overlap was found between the two groups, with HNRs larger than this being cam hips, and smaller being normal ones.
Owing to its sensitivity and repeatability, the method could be used to confirm or refute the clinical diagnosis of a cam hip. Furthermore it can be used as a tool to measure the outcome of cam surgery.
通常使用二维 α 角来量化凸轮髋。该测量方法的准确性可能会受到患者体位和技术人员经验的影响。在本文中，我们描述了一种基于三维计算机断层扫描（CT）图像的凸轮髋定量定义的测量方法。
对 47 个（24 个凸轮，23 个正常）股骨的 CT 扫描进行了分割。将球体拟合到头状关节表面，记录半径（r），并获得股骨颈轴。在垂直于颈部轴的四个位置（r/4、r/2、3r/4 和 r）测量跨越头颈交界处的横截面积。相对于头中心点的表面积，计算并汇总每个切割处的面积（Neck/Head）之间的比值。
正常和凸轮髋有明显差异：凸轮髋的总头颈比（HNRs）始终小于正常髋（p < 0.01）。在两组之间发现了一个没有重叠的 2.55 的截止点，大于此值的 HNRs 为凸轮髋，小于此值的为正常髋。
由于其敏感性和可重复性，该方法可用于确认或反驳凸轮髋的临床诊断。此外，它可以用作测量凸轮手术结果的工具。
