The effect of anatomical tibia vara on the coronal alignment of tibial component in total knee arthroplasty: A radiographic analysis

Abstract

Survivorship in total knee arthroplasty depends on the restoration of the coronal alignment of its components. Failure to restore this may decrease the longevity of TKR. The prevalence of tibia vara in patients with osteoarthritis of the knee undergoing TKA is quite high. We wanted to assess the effect of the varus angulation in the proximal metaphysis of the tibia on tibial component malposition in the coronal plane in patients undergoing total knee replacement. Patients who underwent TKA for primary osteoarthritis of the knee and with more than two years of follow-up were included. The extra-articular tibial deformity was assessed by measuring the angle between the anatomical and mechanical axis of the tibia. The coronal alignment of the femoral and tibial components was measured using lateral distal femoral angle and medial proximal tibial angle.Preoperatively,73 (90.12%) patients were having a neutral tibial anatomical axis and 8(9.9%) patients were having varus angulation in the proximal tibia.Postoperatively,18(22.2%) patients had a neutral mechanical axis. There were 14(17.2%) patients with more than 3 degrees of varus mechanical axis and 41(50.6%) patients had less than 3 degrees of varus mechanical axis alignment. 2 (2.5%) patients had more than 3-degree valgus mechanical axis and 6 (7.4%) had less than 3 degrees valgus mechanical axis. Postoperatively, out of 8 patients with pre-operative tibia vara, only 2(25%) patients had neutral placement of the tibial component. 6 (75%) had both tibial and femoral component malalignment. Out of the 73 patients with pre-operatively neutral tibial axis, 40(54.7%) patients had both tibial and femoral component malalignment. 8 (11%) patients had only tibial and 9(12.3%) patients had only femoral component malalignment. In 16 (19.1%) patients, there was no malalignment of both. There was no significant relationship between the tibial anatomical axis malalignment and the tibial component alignment in patients undergoing TKA for primary osteoarthritis.