CT常用测量指标对儿童髌股关节不稳的诊断价值

目的探讨CT常用测量指标对儿童髌股关节不稳的诊断价值。方法对病例组髌股关节不稳30名患者(共32例膝关节)及对照组25名患者(共27例膝关节)在伸膝位行CT扫描。分别测量股骨滑车面对称性、股骨外侧滑车倾斜度、股骨滑车深度、髌骨倾斜角、髌骨外移度、股骨滑车与胫骨结节水平距离(TTTG)及髌腱长度与髌骨最大对角线长度比值(IS指数)7个指标。对比各指标在病例组和对照组间比较差异是否具有统计学意义,并计算各指标的受试者工作特征曲线下面积,确定诊断界值。结果在病例组中,股骨滑车面对称性、股骨外侧滑车倾斜度、股骨滑车深度均显著减少(P<0.01),髌骨倾斜角、髌骨外移度、TTTG值、IS指数均明显增大(P<0.01)。股骨滑车深度、髌骨倾斜角、和髌骨外移度的曲线下面积均>0.900,其诊断界值分别为<4mm、>23°及>3mm。股骨滑车面对称性、股骨外侧滑车倾斜度和IS指数的曲线下面积均>0.800,其诊断界值分别为<35%<15°及>1.0。TTTG的曲线下面积为0.795,其诊断界值为>20mm。结论伸膝状态下,髌骨倾斜角、股骨滑车深度、髌骨外移度、股骨滑车面对称性、股骨外侧滑车倾斜度、IS指数及TTTG对髌股关节不稳依次具有一定的诊断价值。

Value of Measurements Parameters with CT Images in the Diagnosis of Pediatric Patellofemoral Instability

Objective To explore the value of commonly-used measurements based on CT images to the diagnosis of pediatric patients with patellofemoral instability. Methods Knee CT scan was performed in 32 knees of 30 patients with patellofemoral instability and 27 knees of 25 asymptomatic patients at full extension of the knee.Trochlear facet asymmetry, lateral trochlear inclination, trochlear depth, patellar tilt angle, lateral patellar displacement, tibial tuberosity-trochlear groove distance (TTTG),and Insall-Salvati index(IS index)of patients and control group were measured in CT reconstruction images. Independent sample t test was used to compare the differences of these measurements. Receiver operating characteristic (ROC) was used to calculate the area under curve (AUC) and to define the diagnostic thresholds of each measurement. Results Trochlear facet asymmetry, lateral trochlear inclination, and trochlear depth in patients were significantly lower than those in control group (P<0.01), whereas patellar tilt angle,lateral patellar displacement,TTTG,and IS index were significantly higher (P<0.01). AUC of trochlear depth, patellar tilt angle, and lateral patellar displacement were all greater than 0.900, and the recommended diagnostic thresholds for these measurements were less than 4 mm, greater than 23°, and greater than 3mm, respectively. AUC of trochlear facet asymmetry, lateral trochlear inclination, and IS index were all greater than 0.800, and the recommended diagnostic thresholds for these measurements were less than 35%, less than 15°and greater than 1.0, respectively. AUC of TTTG was 0.795, and its threshold was greater than 20mm. Conclusion At full extension of the knee, patellar tilt angle,trochlear depth, lateral patellar displacement, trochlear facet asymmetry, lateral trochlear inclination, IS index and TTTG, in turn, have certain diagnostic value.