Remaining mild varus limb alignment leads to better clinical outcome in total knee arthroplasty for varus osteoarthritis.

PURPOSE: Postoperative neutral limb alignment [femorotibial mechanical axis (FTMA) 180° ± 3°] is generally considered to be one of the prerequisites for successful total knee arthroplasty (TKA). However, the influence of residual malalignment on clinical and functional outcomes after TKA is unknown. Therefore, the purpose of this study was to investigate the relationship between postoperative limb alignment and clinical outcomes in Asian patients who underwent primary TKA.

METHODS: The study included 220 knees with a mean age of 73.5 years who underwent primary TKA for varus-type osteoarthritis; the mean follow-up period was 3.6 years. Patients were divided into four groups based on postoperative FTMA: severe varus (FTMA < 174°, n = 15), mild varus (FTMA >177°and ≤174°, n = 61), neutral (FTMA 180° ± 3°, n = 128), and valgus (FTMA > 183°, n = 16). Knee Society Knee Score (KSKS) and Knee Society Functional Score (KSFS) were compared among the 4 groups.

RESULTS: KSKS and KSFS showed significant improvement in all groups. There were no statistically significant differences for postoperative KSKS among the four groups. For KSFS, however, the severe varus and valgus groups exhibited significantly lower values compared with the mild varus and neutral groups.

CONCLUSION: Postoperative mild varus alignment as well as neutral mechanical alignment of the lower limb led to excellent functional outcomes. For the clinical relevance, postoperative mild varus alignment of the lower limb is acceptable following TKA for varus-type osteoarthritis.

LEVEL OF EVIDENCE: IV.