Department of Orthopedic Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wang Lang Road, Bangkok Noi, Bangkok, 10700, Thailand.
Department of Orthopedic Surgery, Saraburi Hospital, Saraburi, Thailand.
Eur J Orthop Surg Traumatol. 2022 Jan;32(1):175-181. doi: 10.1007/s00590-021-02890-9. Epub 2021 Mar 26.
Currently, the best and simplest way that used to select the distal femoral valgus cut (DFVC) angle in total knee arthroplasty (TKA) is standing long leg radiograph. However, this kind of film is still not available in all hospitals. The purpose of this study is to compare the accuracy of different empirical DFVC angles in the restoration of the neutral mechanical alignment of the femoral component after TKA.
125 patients who diagnosed primary osteoarthritic knee and underwent unilateral TKA were randomly assigned into three groups: A, B, and C, according to the use of an intramedullary guide with the DFVC angle of 4°, 5°, and 6°, respectively. At three months after surgery, anteroposterior hip-to-ankle computed tomography (CT) scanograms were evaluated. Mechanical axis angle (MAA), mechanical lateral distal femoral angle (LDFA), femoral bowing, femoral neck-shaft angle (FNSA), and outliers of femoral component position were measured and compared among three groups. Independent influencing factors for the outliers > ±3° were determined using binary logistic regression analysis.
Group B was older than group A. There were no significant differences of postoperative MAA, LDFA, femoral bowing, and FNSA among three groups. Outliers > ±3° of femoral component position in each group were 14.6%, 19.0%, and 16.7%, respectively (p = 0.865). When considering the outliers > ±2°, group C (35.7%) had a trend to have fewer outliers than groups A and B (41.5 and 42.9%). However, this finding was not reached the statistical significance (p = 0.778). Femoral bowing was only significantly influencing factors that related to the outliers > ±3° (p = 0.003).
This study demonstrates that there are no significant differences in coronal femoral component alignment among using the DFVC angle of 4°, 5°, and 6°. The use of the DFVC angle of 6° had a trend to reduce the outliers. Nevertheless, femoral bowing is the crucial influencing factor for selecting the degree of DFVC angle.
目前，在全膝关节置换术（TKA）中选择股骨远端外翻角（DFVC）的最佳且最简单的方法是站立位长腿 X 线片。然而，并非所有医院都能提供这种 X 线片。本研究的目的是比较不同经验性 DFVC 角度在 TKA 后恢复股骨假体中性机械对线中的准确性。
根据使用髓内导针的 DFVC 角度为 4°、5°和 6°，将 125 例诊断为原发性膝骨关节炎并接受单侧 TKA 的患者随机分为三组：A、B 和 C 组。术后 3 个月，评估前后位髋关节 - 踝关节计算机断层扫描（CT）扫描图。测量并比较三组间机械轴角度（MAA）、机械外侧股骨远端角（LDFA）、股骨弯曲、股骨颈干角（FNSA）和股骨假体位置的离群值。使用二元逻辑回归分析确定离群值>±3°的独立影响因素。
B 组患者年龄大于 A 组。三组患者术后 MAA、LDFA、股骨弯曲和 FNSA 无显著差异。每组股骨假体位置离群值>±3°的比例分别为 14.6%、19.0%和 16.7%（p=0.865）。当考虑离群值>±2°时，C 组（35.7%）的离群值比例有低于 A 组和 B 组（41.5%和 42.9%）的趋势，但差异无统计学意义（p=0.778）。股骨弯曲是与离群值>±3°相关的唯一显著影响因素（p=0.003）。
本研究表明，使用 4°、5°和 6°DFVC 角度时，股骨假体冠状面对线无显著差异。使用 6°DFVC 角度有降低离群值的趋势。然而，股骨弯曲是选择 DFVC 角度的关键影响因素。
