Background: Correct alignment of the knee is considered to be one of the most influential factors in determining the long-term outcomes after Total Knee Arthroplasty (TKA), and is believed to decrease both the mechanical and shear stresses placed on the bearing surfaces, as well as the bone/prosthesis interfaces. Compensatory malalignment of ankle and hindfoot is a recognized cause for ankle disability and deformity in long-standing osteoarthritic patients with varus deformity. This study aims to assess changes in ipsilateral ankle and hindfoot if any, pre- and post-operative TKA.
Methods: 65 knees of 54 patients of osteoarthritis knee were evaluated for alignment in knee, ankle and hindfoot pre- and post-TKA. Pre- and post-operative scanogram were evaluated for knee and ankle alignment. Hindfoot alignment view was used to calculate hindfoot alignment angle. All parameters were compared before TKA and after 10 weeks TKA and Wilcoxon signed rank test was used to test the significance of the values.
Results: Mean age of the patients was 62.9 years (49-80 years). Mean varus before surgery was 14.49 which changed to 4.01 and mean hindfoot angle valgus reduced from 9.23 to 6.62, both of which was found significant. Significant changes were also observed between pre- and post-op measurements of knee society scores, AOFAS, with improved functional outcomes both in knee and ankle.
Conclusion: This study reveals the radiological and functional changes occurring in the ankle and hindfoot after acute correction of long-standing varus deformity of the knee using total knee arthroplasty. Hindfoot valgus alignment in varus knees decreased significantly post-TKA without any intervention at ankle level. In cases undergoing knee arthroplasty, effect of the acute change in the alignment of the knee on the ankle and hindfoot should be taken into consideration and the amount of correction of knee alignment can be a predictor of correction of ankle and hindfoot malalignment too. The lateral benefit of improvement in ankle pain after TKA is a significant gain in this study.
Keywords: Hindfoot alignment; Knee arthroplasty; Mechanical axis; Varus knee.
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