Division of Orthopaedics, University of Ottawa Faculty of Medicine, Ottawa, ON, Canada.
J Bone Joint Surg Am. 2011 Jan 5;93(1):73-80. doi: 10.2106/JBJS.I.01689.
Patellar height is evaluated with ratios that have been derived from measurements made on lateral radiographs of the knee. The importance of using a ratio is that magnification, physical size, and flexion angle are eliminated as factors that affect the values. The Insall-Salvati index was the first ratio to be described. It remains the most popular, possibly because normal values are easy to remember. As all of the currently accepted methods are cumbersome to use because they require two measurements as well as a calculation, a single angular measurement was devised (the plateau-patella angle) to offer a simpler alternative. The purpose of this study was to introduce the new method and to assess its validity by comparing it with three classic, commonly used ratios.
In two groups of patients, after exclusions, 269 lateral radiographs of the knee were evaluated. All measurements required for the Insall-Salvati, the Blackburne-Peel, and the Caton-Deschamps indices plus the plateau-patella angle were recorded, along with basic demographics. For validation, the new method was compared with the established methods, and interobserver and intraobserver reliability were computed.
There was excellent correlation between the proposed angle and the three selected indices, especially with the Blackburne-Peel index. Interobserver and intraobserver reliability was high and compared favorably with that reported in the literature for the three classic ratios. The calculated ratios were in line with those described in the literature. The mean plateau-patella angle was 25°. Ninety percent of the measurements fell between 20° and 30°, and one standard deviation above and below was 21° to 29°.
The plateau-patella angle, a new method of evaluating patellar height, can be measured rapidly with use of either a goniometer or digital software. Its range is easy to remember, it is reliably reproduced, and it correlates well with traditional methods. It is thus a valid and easy alternative method for the evaluation of patellar height.
髌骨高度通过从膝关节侧位 X 光片上测量得出的比值来评估。使用比值的重要性在于消除了放大率、物理尺寸和弯曲角度等影响数值的因素。Insall-Salvati 指数是第一个被描述的比值，它仍然是最受欢迎的，可能是因为正常数值易于记忆。由于目前所有公认的方法都很繁琐，因为它们需要进行两次测量和一次计算，所以设计了一种单一的角度测量方法（平台-髌骨角），以提供更简单的替代方法。本研究的目的是介绍新方法，并通过与三种常用的经典比值进行比较来评估其有效性。
在两组患者中，排除后评估了 269 例膝关节侧位 X 光片。记录了 Insall-Salvati、Blackburne-Peel 和 Caton-Deschamps 指数以及平台-髌骨角所需的所有测量值，以及基本人口统计学数据。为了验证，将新方法与已建立的方法进行比较，并计算了观察者间和观察者内的可靠性。
提出的角度与三个选定的指数之间存在极好的相关性，特别是与 Blackburne-Peel 指数。观察者间和观察者内的可靠性都很高，并且与文献中报道的三种经典比值相当。计算出的比值与文献中描述的一致。平台-髌骨角的平均值为 25°。90%的测量值在 20°至 30°之间，一个标准差上下的范围为 21°至 29°。
平台-髌骨角是一种新的评估髌骨高度的方法，可以使用量角器或数字软件快速测量。其范围易于记忆，重复性好，与传统方法相关性好。因此，它是一种有效且易于使用的评估髌骨高度的替代方法。
