Weight-bearing line at the ankle joint level shifted laterally after total knee arthroplasty for varus knee osteoarthritis: Evaluation of the hip-to-calcaneus line

Orthop Traumatol Surg Res. 2024 Apr;110(2):103690. doi: 10.1016/j.otsr.2023.103690. Epub 2023 Sep 21.

Abstract

Background: Few studies have comprehensively examined how alignment beyond the ankle joint changes after Total knee arthroplasty (TKA). This retrospective study aimed to answer the questions: (1) do the radiological parameters beyond the ankle joint, including the weight-bearing line at the ankle joint level, change after TKA in varus knee osteoarthritis? (2) Does the lower extremity alignment correlate with alignment beyond the ankle joint?

Hypothesis: Our hypothesis was that TKA altered the radiological parameters beyond the ankle, which correlated with the lower extremity alignment.

Patients and methods: This retrospective study included 67 patients who underwent mechanically aligned TKA for varus knee osteoarthritis. The hip-knee-ankle angle (HKA), tibial plafond inclination angle (TPIA), hindfoot alignment angle (HA), talar tilt (TT), and weight-bearing line at the ankle joint level (mechanical ankle joint axis point [MAJAP]) were measured using radiographs taken before and 6 months after TKA; each parameter was compared between the two time points. The correlations between HKA and other parameters were examined preoperatively and postoperatively.

Results: The mean HKA, TPIA, HA, TT, and MAJAP changed significantly after TKA from 15.0±6.1̊ to 2.6̊±3.5̊, from 10.8̊±5.7̊ to 4.7̊±3.9̊, from 2.3̊±5.5̊ to -2.5̊±4.5̊, from 0.2̊±1.3̊ to -0.5̊±1.4̊, and from 29.3±23.3 to 54.3±20.6, respectively. Correlations were noted between the preoperative HKA and the preoperative TPIA (r=0.58), HA (r=0.36), and MAJAP (r=-0.59), and between the postoperative HKA and the postoperative TPIA (r=0.54) and MAJAP (r=-0.38).

Discussion: TKA for varus knee osteoarthritis altered radiological parameters beyond the ankle, with the weight-bearing line at the ankle joint level passing more laterally. The weight-bearing line at the ankle joint level was correlated with lower extremity alignment both preoperatively and postoperatively.

Level of evidence: IV; single-centre retrospective observational study.

Keywords: Ankle joint; Coronal alignment; Hip-to-calcaneus line; Radiological parameters; Total knee arthroplasty.

Publication types

  • Observational Study

MeSH terms

  • Ankle Joint / diagnostic imaging
  • Ankle Joint / surgery
  • Arthroplasty, Replacement, Knee*
  • Calcaneus* / surgery
  • Humans
  • Knee Joint / surgery
  • Lower Extremity / surgery
  • Osteoarthritis, Knee* / diagnostic imaging
  • Osteoarthritis, Knee* / surgery
  • Retrospective Studies
  • Tibia / surgery
  • Weight-Bearing