Computer-assisted surgery does not improve the rotational alignment of the femoral component in total knee arthroplasty for severe genu varus deformity

Abstract

Background: Accurate femoral rotational alignment is critical for successful total knee arthroplasty (TKA). Debates exist about whether computer-assisted surgery-TKA (CAS-TKA) improves the accuracy of femoral rotational alignment. We hypothesize that it is related to the severity of the preoperative genu varus deformity and that CAS-TKA is beneficial under certain circumstances. Methods: Patients who had osteoarthritis with genu varus deformity and underwent conventional TKA or CAS-TKA between January 2007 and July 2013 at our hospital were enrolled. Based on the degree of preoperative deviation from the mechanical axis (MA), the patients were divided into three subgroups at 5-degree intervals: (1) varus deformity of ＜ 10 degrees, (2) 10–14.9 degrees, and (3) ≥ 15 degrees. Computed tomography was used to determine whether CAS-TKA provided better femoral rotational alignment than did conventional TKA. Component and limb alignment were also radiographically compared. Results: One hundred seventy-three knees on 128 patients met the inclusion criteria. For patients in the ＜ 10 degrees and 10–14.9 degrees groups, the component alignments and postoperative mechanical axes were not significantly different between conventional and CSA-TKA. For patients in the ≥ 15 degrees group, however, the femoral flexion angle was significantly (p ＜ 0.001) better for CSA-TKA, but not for the femoral valgus, tibial valgus, tibial flexion, or femoral rotational angles. Conclusions: CAS-TKA does not improve the accuracy of rotational alignment of the femoral component in patients with genu varus deformity. Level of Evidence: Therapeutic Level III.