Purpose: The postoperative alignment was compared according to the severity of preoperative varus deformity in computer-assisted and conventional total knee arthroplasty (CAS-TKA).
Methods: The study reviewed 127 consecutive CAS-TKA and 236 conventional TKA, retrospectively. In CAS-TKA, 77 knees with a varus deformity ≤15.0° were classified in group CAS-A and 50 knees with a varus deformity >15.0° were classified in group CAS-B. In conventional groups, 204 knees with a varus deformity ≤15.0 were classified in group Conventional-A and 32 knees with a varus deformity >15.0° were classified in group Conventional-B. The postoperative mechanical axis (MA) was compared among groups CAS-A, CAS-B, Conventional-A and Conventional-B.
Results: The average postoperative MA was 0.7° varus in group CAS-A, 2.8° varus in group CAS-B, 1.1° varus in group Conventional-A and 3.2° varus in group Conventional-B (p < 0.001). The postoperative MA was within 3° in 81.8, 62.0, 58.8 and 37.5 % of group CAS-A, CAS-B, Conventional-A and Conventional-B, respectively.
Conclusions: The severity of preoperative varus deformity influences postoperative alignment despite using CAS. More careful correction of the alignment is required, especially in TKA performed on patients with a greater varus deformity.
Level of evidence: III.