Slight varus malalignment has no influence on clinical function in patients with femoral lateral bowing after total knee replacement

Abstract

Objective To investigate the effect of residual slight varus malalignment after total knee arthroplasty (TKA) on the function in patients with femoral lateral bowing and medial osteoarthritis of the knee (MOA). Methods A retrospective cohort study was performed on 152 patients suffering from femoral lateral bowing and MOA and undergoing TKA in our hospital from January to December 2015. After a mean follow-up period of 4.3 years, the patients were stratified into mild varus (>3°~6°, group A, n=45), severe varus (>6°, group B, n=26), and neutral (-3°~3°, group C, n=81) groups based upon their post-operative alignment. The International Knee Society Score (KSS) and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) scores were compared among the groups. Results No implant was revised during the follow-up period. The patients in the group A were averagely corrected from (9.8±3.2)° pre-operatively to (4.3±0.6)° post-operatively, those in the group B from (10.8±1.6)° to (7.1±1.2)°, and those in the group C from (8.8±3.5)° to (0.6±1.3)°. KSS scores were increased following TKA for all the groups. The group A scored significantly better in the total KSS score (167.5±26.1) as compared with the group C (157.0±29.4, P=0.02) and group B (150.9±32.3, P=0.01). In the functional sub-scores, a significantly better score was obtained in the group A when compared with the group B and group C (P=0.04, 0.01). The knee sub-score of the group A was significantly better than those of the group B (P=0.03), but was similar to that of the group C. With regard to the WOMAC score, the group A scored significantly lower than the group C in the total score (P=0.02) and in 2 of the sub-scores (Activities of daily living: P=0.02; stiffness: P=0.03). WOMAC scores were similar between the group B and C. Conclusion Our study indicates that mild varus malalignment (>3°~6°) didn't influence the effect of TKA for patients with femoral lateral bowing and MOA at the short-term follow-up period.

Keywords

• osteoarthritis
• total knee arthroplasty
• femora lateral bowing
• varus knees