Abstract：
OBJECTIVE: Femorotibial angle (FTA) is a convenient measure of coronal knee alignment that can be extracted from a short knee radiograph, avoiding the additional radiation exposure and specialist equipment required for full-leg radiographs. While intra- and inter-reader reproducibility from the same image has been reported, the full scan-rescan reproducibility across images, as calculated in this study, has not.
METHODS: In this study, 4589 FTA measurement pairs from 2586 subjects acquired a year apart were used to estimate FTA scan-rescan reproducibility using data from the Osteoarthritis Initiative. Subjects with radiographic progression of osteoarthritis or other conditions that may cause a change in coronal knee alignment were excluded. Measurement pairs were analysed using paired-samples t $t$ tests to detect differences and compared to symptomatic changes in Western Ontario and McMaster Universities Arthritis Index scores for joint pain, stiffness and physical function to detect correlations.
RESULTS: The 95% limit of agreement and the paired-samples correlation were calculated with high precision to be [-1.76°, +1.78°] and 0.938, considerably worse than the corresponding figures for intra- and inter-reader reproducibility, without relation to symptomatic or radiographic changes in knee condition. This error will weakly attenuate R 2 ${R}^{2}$ and r $r$ values from their true values in correlative studies involving FTA. The realistic maximum value for R 2 ${R}^{2}$ is 87% and for Pearson\'s r $r$ is 93%.
CONCLUSIONS: The scan-rescan reproducibility in FTA is almost double the intra- and inter-reader reliability from a single scan. At almost ±2° accuracy, FTA is inappropriate for surgical use, but it is sufficiently reproducible to produce good correlations in studies predicting disease incidence and progression.
METHODS: Level II, retrospective study.
METHODS: In this study, 4589 FTA measurement pairs from 2586 subjects acquired a year apart were used to estimate FTA scan-rescan reproducibility using data from the Osteoarthritis Initiative. Subjects with radiographic progression of osteoarthritis or other conditions that may cause a change in coronal knee alignment were excluded. Measurement pairs were analysed using paired-samples t $t$ tests to detect differences and compared to symptomatic changes in Western Ontario and McMaster Universities Arthritis Index scores for joint pain, stiffness and physical function to detect correlations.
RESULTS: The 95% limit of agreement and the paired-samples correlation were calculated with high precision to be [-1.76°, +1.78°] and 0.938, considerably worse than the corresponding figures for intra- and inter-reader reproducibility, without relation to symptomatic or radiographic changes in knee condition. This error will weakly attenuate R 2 ${R}^{2}$ and r $r$ values from their true values in correlative studies involving FTA. The realistic maximum value for R 2 ${R}^{2}$ is 87% and for Pearson\'s r $r$ is 93%.
CONCLUSIONS: The scan-rescan reproducibility in FTA is almost double the intra- and inter-reader reliability from a single scan. At almost ±2° accuracy, FTA is inappropriate for surgical use, but it is sufficiently reproducible to produce good correlations in studies predicting disease incidence and progression.
METHODS: Level II, retrospective study.
摘要：
目的：股腿角（FTA）是一种方便的冠状膝关节对齐方法，可以从短膝关节X光片中提取，避免额外的辐射暴露和全腿射线照片所需的专业设备。虽然已经报道了来自同一图像的阅读器内和阅读器间的再现性，跨图像的全扫描-重新扫描再现性，根据这项研究的计算，没有。
方法：在本研究中，使用来自骨关节炎倡议的数据，使用间隔一年获取的2586名受试者的4589个FTA测量对估计FTA扫描重新扫描的可重复性。排除了放射学上骨关节炎进展或其他可能导致冠状膝关节排列变化的受试者。使用配对样本t$t$测试分析测量对，以检测差异，并与西安大略省和麦克马斯特大学关节炎指数评分的症状变化进行比较，刚度和物理函数来检测相关性。
结果：95％的一致性极限和配对样本相关性以高精度计算为[-1.76°，+1.78°]和0.938，大大差于相应的数字内和读者间的再现性，与膝盖状况的症状或影像学变化无关。在涉及FTA的相关研究中，此误差将使R2${R}^{2}$和r$r$的真实值减弱。R2${R}^{2}$的实际最大值为87%，Pearson的r$r$的实际最大值为93%。
结论：FTA中的扫描-重新扫描再现性几乎是单次扫描的阅读器内和阅读器间可靠性的两倍。在接近±2°的精度下，FTA不适合手术使用，但它具有足够的可重复性，可以在预测疾病发病率和进展的研究中产生良好的相关性。
方法：二级，回顾性研究。
方法：在本研究中，使用来自骨关节炎倡议的数据，使用间隔一年获取的2586名受试者的4589个FTA测量对估计FTA扫描重新扫描的可重复性。排除了放射学上骨关节炎进展或其他可能导致冠状膝关节排列变化的受试者。使用配对样本t$t$测试分析测量对，以检测差异，并与西安大略省和麦克马斯特大学关节炎指数评分的症状变化进行比较，刚度和物理函数来检测相关性。
结果：95％的一致性极限和配对样本相关性以高精度计算为[-1.76°，+1.78°]和0.938，大大差于相应的数字内和读者间的再现性，与膝盖状况的症状或影像学变化无关。在涉及FTA的相关研究中，此误差将使R2${R}^{2}$和r$r$的真实值减弱。R2${R}^{2}$的实际最大值为87%，Pearson的r$r$的实际最大值为93%。
结论：FTA中的扫描-重新扫描再现性几乎是单次扫描的阅读器内和阅读器间可靠性的两倍。在接近±2°的精度下，FTA不适合手术使用，但它具有足够的可重复性，可以在预测疾病发病率和进展的研究中产生良好的相关性。
方法：二级，回顾性研究。
