Department of Mechanical Engineering, Biomechanics Group, Imperial College London, London, UK.
MSk Lab, Department of Surgery and Cancer, Imperial College London, London, UK.
Knee Surg Sports Traumatol Arthrosc. 2024 Dec;32(12):3133-3140. doi: 10.1002/ksa.12352. Epub 2024 Jul 10.
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.
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 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.
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 and values from their true values in correlative studies involving FTA. The realistic maximum value for is 87% and for Pearson's is 93%.
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.
Level II, retrospective study.
股胫角（FTA）是一种方便的冠状膝关节对线测量方法，可从短膝关节射线照相术中提取，避免了全腿射线照相术所需的额外辐射暴露和专业设备。虽然已经报道了来自同一图像的同内和同间读者的可重复性，但正如本研究中计算的那样，跨图像的全扫描-重扫描可重复性尚未报道。
在这项研究中，使用来自 Osteoarthritis Initiative 的数据，从 2586 名患者中获得了一年相隔的 4589 对 FTA 测量值对，以估计 FTA 扫描-重扫描的可重复性。排除有骨关节炎放射学进展或其他可能导致冠状膝关节对线改变的疾病的患者。使用配对样本检验分析测量对，以检测差异，并与 Western Ontario 和 McMaster 大学关节炎指数评分的关节疼痛、僵硬和身体功能的症状变化进行比较，以检测相关性。
使用高精度计算出 95%的一致性界限和配对样本相关性为[-1.76°，+1.78°]和 0.938，明显差于同内和同间读者的可重复性，与膝关节状况的症状或放射学变化无关。在涉及 FTA 的相关性研究中，这种误差将弱衰减与真实值相关的 和 值。涉及 FTA 的相关性研究中，实际的 最大值为 87%，Pearson's 最大值为 93%。
FTA 的扫描-重扫描可重复性几乎是单次扫描的同内和同间读者可靠性的两倍。在几乎±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和进展的研究中产生良好的相关性。
II 级，回顾性研究。
