应用负重CT在三维空间测量后足力线的研究

Assessment of the hindfoot alignment in three-dimensional space by weightbearing CT

目的通过比较FAO与传统X线片的对后足力线的评价结果,了解其临床相关性,并进一步确定该方法的可重复性。方法本文采用前瞻性队列研究的方法,对2017年12月～2018年3月于我中心门诊就诊患者的后足力线进行分析,入组患者经查体被分为三组:正常组(组1),外翻组(组2)及内翻组(组3)。入组的连续病例140足(71人),均进一步行双足负重CT(ped CAT,Curvebeam,美国)检查并测量FAO。此外,在数字重建放射图像(digitally reconstructed radiograph,DDR)中测量跟骨外翻角。分别计算FAO及跟骨外翻角的组内相关系数(intraclass correlation coefficients,ICC),并对两者关系进行回归分析。结果 FAO及跟骨外翻角在正常组中,分别为(1.69±2.58)%和(4.13±2.67)°;外翻组中,为(7.46±3.18)%/(9.00±3.43)°;内翻组为(-6.11±4.55)%/(-7.49±6.06)°。而FAO的观察者内/间信度分别为0.991/0.992,跟骨外翻角的观察者内/间信度为0.976/0.976。FAO与跟骨外翻角间有良好的线性关系(R2=0.779),回归直线斜率为1.083。结论通过负重CT在三维空间下可准确客观评价后足力线。FAO与临床查体,传统X线间有良好的相关性,同时具备优秀的可重复性。

Objective The objective is to assess the clinical relevance and reproducibility of the FAO value for hindfoot alignment by comparing it with plain films. Methods As a prospective cohort study, A continuous series of 140 feet （71 patients） were includeed from December 2017 to March 2018, clinically examined and divided into 3 groups： normal alignment （Group 1）, valgus （Group 2）, varus （ Group 3）. All patients had a bilateral weightbearing CT （pedCAT, Curvebeam, USA）, and the FAO value was recorded. The long axial view angle （LAV） was measured on Digitally Reconstructed Radiographs （DRR）. The reproducibility of FAO and LAV were calculated using intraclass correlation coefficients（ICCs）,regression analysis was conducted to study the correlation between the two methods. Results In Group 1, the mean value for FAO/HAct was （1.69±2.58） %/（4.13±2.67） °, in Group 2, the FAO/HAct was （7.46±3.18） %/（9.00±3.43） °; in Group 3, the values were （-6.11±4.55） %/（-7.49±6.06） °. The intra-/interobserver reliability was 0.991/0.992 for FAO, and 0.976/0.976 for HAct. There was a good linear correlation between HAct and FAO （R2=0.779）, and the regression slope was 1.083. Conclusion The use of weightbearing CT can help characterize hindfoot alignment objectively. FAO has excellent repeatability, and it correlates well with clinical examination, X-ray findings and previous literature. The FAO is a clinically relevant and reproducible method for measuring hindfoot alignment.