Nelitz M, Lippacher S, Reichel H, Dornacher D
Department of Orthopaedic Surgery, University of Ulm, Ulm, Germany,
Knee Surg Sports Traumatol Arthrosc. 2014 Jan;22(1):120-7. doi: 10.1007/s00167-012-2321-y. Epub 2012 Nov 30.
Trochlear dysplasia is considered to be one of the major factors causing patellofemoral instability (PFI). Dejour's classification is widely used to assess the severity of trochlear dysplasia. Additionally, in current literature, different quantitative parameters are recommended to distinguish between a normal trochlea and a dysplastic trochlea. In order to achieve a more objective evaluation of the trochlea, the aim of this study was to evaluate whether specific measurements of the femoral trochlea can be assigned to the qualitative classification system of Dejour.
Transverse MRI T2-weighted scans of 80 knees with symptomatic PFI and varying severity of trochlear dysplasia were classified according to Dejour (type A to D). For all MRI scans, quantitative measurements with parameters as described in the literature were applied. The values were then allocated to Dejour's classification. In addition to the four-grade analysis, two-grade analysis was also performed (Dejour type A against type BCD). Dependent on the cut-off values, specificity, sensitivity and Youden index for each parameter was defined.
The allocation resulted in the following distribution: type A trochlear dysplasia n = 25, type B n = 23, type C n = 18 and type D n = 14. In descriptive statistics, none of the measurements proposed in the literature could be assigned to the four-grade classification system of Dejour. For the two-grade analysis at the cut-off, sensitivity ranged from 75 to 86 % and specificity from 76 to 84 % for lateral trochlear inclination, trochlear facet asymmetry and depth of trochlear groove. All other measurements showed a poor sensitivity ranging from 49 to 67 % and specificity from 40 to 72 %. Interobserver and intraobserver repeatability for the measured parameters was fair to moderate (ICC values 0.34-0.58) in high-grade dysplasia (type BCD) and substantial to almost perfect (ICC values 0.71-0.88) in low-grade trochlear dysplasia (type A).
Quantitative measurements of the femoral trochlea have shown to be of limited value for the assessment of trochlear dysplasia. None of the quantitative measurements of the trochlea on transverse images could be assigned to the four-grade descriptive classification of trochlear dysplasia of Dejour. Additionally, measurements could not be reliably performed in high-grade trochlear dysplasia. However, trochlear inclination, trochlear facet asymmetry and depth of trochlear groove may help to distinguish between low-grade and high-grade dysplasia.
滑车发育异常被认为是导致髌股关节不稳定（PFI）的主要因素之一。Dejour分类法被广泛用于评估滑车发育异常的严重程度。此外，在当前文献中，推荐使用不同的定量参数来区分正常滑车和发育异常的滑车。为了更客观地评估滑车，本研究的目的是评估股骨滑车的特定测量值是否可以应用于Dejour的定性分类系统。
对80例有症状的PFI且滑车发育异常程度不同的膝关节进行横向MRI T2加权扫描，并根据Dejour法（A至D型）进行分类。对所有MRI扫描，应用文献中描述的参数进行定量测量。然后将这些值分配到Dejour分类中。除了四级分析外还进行了两级分析（Dejour A型与BCD型）。根据临界值，定义每个参数的特异性、敏感性和尤登指数。
分配结果如下分布：A型滑车发育异常n = 25，B型n = 23，C型n = 18，D型n = 14。在描述性统计中，文献中提出的测量值均不能应用于Dejour的四级分类系统。对于临界值处的两级分析，外侧滑车倾斜度、滑车小面不对称性和滑车沟深度的敏感性范围为75%至86%，特异性范围为76%至84%。所有其他测量显示敏感性较差，范围为49%至67%，特异性范围为40%至72%。在高级别发育异常（BCD型）中，测量参数的观察者间和观察者内重复性为中等至良好（ICC值0.34 - 0.58），在低级别滑车发育异常（A型）中为高至几乎完美（ICC值0.71 - 0.88）。
股骨滑车的定量测量对于评估滑车发育异常的价值有限。横向图像上滑车的定量测量值均不能应用于Dejour滑车发育异常的四级描述性分类。此外，在高级别滑车发育异常中无法可靠地进行测量。然而，滑车倾斜度、滑车小面不对称性和滑车沟深度可能有助于区分低级别和高级别发育异常。
