RESIDUAL DEFORMITY AFTER BILATERAL KNEE ARTHROPLASTY: IMPACT ON SHORT TERM OUTCOMES

Abstract

Purpose— to evaluate the impact of frontal positioning of prosthesis components after bilateral Tka on short term functional outcomes. Material and Methods. The authors performed a retrospective analysis of teleroentgenograms of 466 patients after bilateral Tka with initial varus deformity. Functional and roentgenological outcomes were evaluated at average in 16,4±2,9 months postoperatively. Mean preoperative varus deformity was 10° (from 5 to 25°), initial angle between the anatomical and mechanical femoral axis (FVa) was 6,7±2° (from 3 to 12°). The neutral axis of both lower limbs (Hka = 180±0,5°) was obtained in 99 (21,2%) out of 466 patients. Residual deformity in one of the limbs above 3° with the neutral alignment of the contralateral limb was observed in 44 (9,4%) patients, bilateral residual deformity – in 32 (6,9%) patients. Other 291 patients demonstrated the deviation from mechanical axis in the range from 1 to 3° (±0,5°). all patients were divided into three groups: first group consisted of 10 patients with neutral axis of one limb and varus deformity of the other limb above 3°; second group — 10 patients with bilateral residual varus deformity above 3°; third group — 12 patients with neutral axis of both limbs (Hka = 180°). The angle of residual deformity averaged 3,7° (from 3,2 to 5,1°).Results.No statistically significant differences between the groups were observed for dynamometric parameters and SF-36 scores, as well as for functional kSS scores (p>0,05). However, the authors reported in patients of the first group a stance phase on the side of residual varus deformity longer at 15% (p<0,05) and transfer phase shorter at 17% (p<0,05) as compared to contralateral limb (with neutral alignment, Hka = 180°), which is indicative of load asymmetry and can have a negative impact at a later stage.Conclusion. Symmetrical residual varus deformity of lower limbs in the rage of 3,2–5,1° has no negative impact of short term clinical and functional outcomes of Tka. Muscular function and gait properties in patients with neutral axis of the lower limbs and in patients with symmetrical residual varus deformity after Tka were similar 16,4±2,9 months postoperatively.