Influence of the post-operative axis on the clinical results of total knee replacement for severe varus deformities: does a slight residual varus improve the results?

PurposeSome recent articles have suggested that in the case of large varus deformity, it may be advantageous to leave some residual post-operative varus as a means of improving functional outcome.The objective of this study is to compare the results of total knee replacement (TKR) performed for significant varus deformity (HKA<170 degrees) where there is a residual post-operative varus (HKA<180 degrees) to the results of TKR for significant varus deformity with either neutral post-operative (HKA=180 degrees) or mild valgus post-operative alignment (HKA>180 degrees).MethodsThis series was made up of 208 knees. The mean pre-operative HKA angle was 1663 degrees (154-169 degrees), of which 150 were followed up for a mean 8.5years (58 lost to follow-up). Based on post-operative radiographs, two groups were formed: group 1 (88 knees) in which post-operative alignment was 177.81 degrees (175-179 degrees) and group 2 (62 knees) in which post-operative alignment was 181 +/- 1 degrees (180-184 degrees).Results The mean international knee society (IKS) score for group 1 was 178.8 +/- 22 points (113-200) and 181.7 +/- 22 points (95-200) for group 2. Oxford knee score was 20.4 +/- 9 points (12-45) in group 1 and 19.2 +/- 9 (12-50) in group 2. The results were slightly better in group 2 (in slight valgus) but this difference was not statistically significant (p=0.44 and 0.4).Conclusion The results of knee replacement performed for severe varus deformity are not adversely affected by post-operative valgus alignment. There is in fact a trend towards superior results for neutral or valgus alignment than slight residual varus, but this difference was not statistically significant.