PURPOSE OF THE STUDY To document and compare the functional outcome of neutral alignment and under-correction after total knee arthroplasty (TKA) in severe varus knees of more than 15° at three and 12 months post-surgery. MATERIALS AND METHODS One hundred twenty-four consecutive patients (163 TKAs) of an average age of 61.9 years (52-79) with a pre-operative varus more than 15° were managed with jig-based TKA. Based on the post-operative mechanical femorotibial alignment (FTMA), they were categorised into three groups, namely neutral (180 + 3°), mild varus (173° to 176°) and severe varus (172° and below). The outcomes of these three groups were assessed at three and 12 months by the Oxford knee score and the WOMAC score were calculated and co-related to the extent of correction. RESULTS At three months, knees in the mild varus group (n = 88) had the best results with an Oxford knee score of 41.76 + 1.44 and a WOMAC score of 19.29 + 2.93 compared to the severe varus group and the neutral alignment group which had Oxford knee scores (OKS) of 37.43 + 2.51 and 31.91 + 3.51 and WOMAC scores of 22.57 + 1.51 and 24.46 + 4.15 respectively. However at 12 months, knees in all the groups (neutral, mild varus, severe varus) had similar good functional outcomes with OKS of 39.08 + 1.68, 39.24 + 1.88, 39.29 + 1.11 and WOMAC scores of 17.42 + 2.15, 16.48 + 2.11, 16.14 + 1.21 respectively. A scatter plot done for post-operative FTMA and the functional outcome score for both scores showed a bell curve with the best outcome corresponding to a FTMA of 175° at 3 months and equal distribution for both scores at 12 months. CONCLUSION The results of our study showed that minimal under-correction gave superior functional outcomes at three months. But this advantage was temporary and both, under-correction and neutral alignment achieved equally good outcomes at one year. Considering the increased prosthesis longevity associated with neutral alignment, we propose that neutral alignment must be aimed for during TKA for knees with severe varus. STUDY DESIGN Prospective study.

中文翻译：

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严重的内翻全膝关节置换术后，最小的矫正不足会产生更好的结果，神话或现实？分析了162个内翻大于15度的膝盖。

研究目的记录和比较在术后三个月和十二个月内，全膝关节置换术（TKA）在大于15°的重度内翻膝盖中进行中性对准和矫正不足的功能结果。材料与方法采用夹具型TKA治疗了124例平均年龄61.9岁（52-79）的连续患者（163 TKA），术前内翻超过15°。根据术后股骨机械对准（FTMA），将它们分为三组，即中性（180 + 3°），轻度内翻（173°至176°）和重度内翻（172°及以下）。通过牛津膝关节评分在三个月和十二个月评估这三组的结局，并计算WOMAC评分并将其与矫正程度相关联。结果三个月后，轻度内翻组（n = 88）的膝关节表现最佳，牛津膝关节评分为41.76 + 1.44，WOMAC评分为19.29 + 2.93，而重度内翻组和中立对齐组的牛津膝关节评分为（OKS） ）分别为37.43 + 2.51和31.91 + 3.51，WOMAC分数分别为22.57 + 1.51和24.46 + 4.15。然而，在12个月时，所有组（中性，轻度内翻，重度内翻）的膝关节都有相似的良好功能预后，OKS为39.08 + 1.68、39.24 + 1.88、39.29 + 1.11，WOMAC评分为17.42 + 2.15、16.48 + 2.11，分别为16.14 + 1.21。术后FTMA的散点图和两个评分的功能结局评分均显示出钟形曲线，其最佳结局对应于3个月时FTMA为175°且12个月时两个评分均等分布。结论我们的研究结果表明，最小的矫正不足可使三个月的功能恢复更好。但是，这种优势是暂时的，并且校正不足和中性对准在一年中都取得了同样好的效果。考虑到与中性对齐相关的假体寿命的延长，我们建议在TKA期间必须针对严重内翻的膝关节进行中性对齐。研究设计前瞻性研究。