Center for Musculoskeletal Surgery, Charité, University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.
Center for Musculoskeletal Surgery, Charité, University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
Knee Surg Sports Traumatol Arthrosc. 2019 May;27(5):1470-1476. doi: 10.1007/s00167-018-5056-6. Epub 2018 Jul 10.
The mechanical axis of the lower limb has shown to vary between different weight-bearing conditions and change after total knee arthroplasty (TKA). The purpose of this study was to investigate the correlation between mechanical axis alignment in standing long-leg radiographs and limb loading after TKA.
Mechanical axis of the lower limb and limb loading have been prospectively evaluated in 115 patients 10 days and 3 months after TKA. By the moment of standing long-leg radiography for analysis of the mechanical leg axis, two digital scales separately captured the load of each limb.
Mechanical axis changed from an initial - 1° ± 2° valgus alignment to a varus axis of + 1° ± 2° (p < 0.01). This change in alignment was associated with an increase of limb loading from 89.9 ± 10.7 to 93.0 ± 7.0% (p < 0.01). The mechanical axis strongly correlated with relative limb loading at the first and second measurements (r = 0.804, p < 0.001, respectively, r = 0.562, p < 0.001). A significant change in the rate of outliers was registered within the observation period. These alterations and distinctions were much more pronounced in patients with postoperative incomplete extension (n = 15).
The postoperative mechanical axis correlates with limb loading. A clinical relevant change in frontal alignment of the lower limb is associated with increased limb loading after TKA. The actual mechanical axis can only be assessed at physiological limb loading in long-leg radiographs with complete extension at full weight bearing.
Diagnostic study, Level II.
下肢力学轴在不同负重条件下存在差异，全膝关节置换术（TKA）后也会发生改变。本研究旨在探讨 TKA 后站立位全长下肢正位片的力学轴对线与肢体负重之间的相关性。
前瞻性评估 115 例 TKA 后 10 天和 3 个月的下肢力学轴和肢体负重。在进行站立位全长下肢正位片分析力学下肢轴时，使用两个电子秤分别测量每条腿的负重。
下肢力学轴从初始的-1°±2°外翻对线变为+1°±2°的内翻轴（p<0.01）。这种对线的改变与肢体负重从 89.9%±10.7%增加到 93.0%±7.0%相关（p<0.01）。力学轴与第一次和第二次测量时的相对肢体负重呈强相关（r=0.804，p<0.001，r=0.562，p<0.001）。在观察期间，记录到离群值的比率有显著变化。在术后存在不完全伸展的患者中（n=15），这些改变和差异更为明显。
术后的力学轴与肢体负重相关。TKA 后下肢冠状面对线的临床相关改变与肢体负重增加相关。只有在完全负重、完全伸展的站立位全长下肢正位片上才能评估实际的力学轴。
诊断研究，II 级。
