Static radiographic measurements accurately reflect dynamic knee alignment in medial compartment osteoarthritis.

Abstract

To investigate the relationship between static hip-knee-ankle angle (sHKA) measured by standing long-leg radiographs and dynamic hip-knee-ankle angle (dHKA) assessed via motion capture in patients with medial compartment knee osteoarthritis (OA). It was hypothesised that (H1) sHKA is comparable to dHKA, and (H2) the presence of varus thrust (VT) is significantly associated with larger static and dynamic knee alignment angles. This prospective cohort study enrolled patients diagnosed with medial compartment knee OA scheduled for high tibial osteotomy. Patients with medial compartment knee osteoarthritis suitable for surgery were included. Exclusion criteria encompassed inflammatory arthritis, previous knee surgery, ACL instability, lateral or patellofemoral osteoarthritis requiring surgery and neuromuscular gait disorders. Static alignment was assessed via radiographs, and dynamic alignment and VT were recorded using a Vicon motion capture system. Differences between sHKA and dHKA were examined using univariate analysis, Bland-Altman analysis and correlations. The association between VT and knee alignment was analysed using t-tests. One hundred patients were analysed (mean age 53 years, body-mass index 27 kg/m²), resulting in a mean sHKA of 5.1° and a mean dHKA of 4.8°, with no significant difference between the two measurements (p = 0.08). A moderate correlation was found between sHKA and dHKA (r = 0.42, p < 0.01). Presence of VT was significantly associated with greater dynamic varus alignment (p = 0.01). Static radiographic alignment closely corresponds with dynamic alignment during gait in patients with medial compartment knee OA. Additionally, VT was found to have a significant influence on dynamic knee alignment. These results suggest that, while static radiographs offer a reliable preoperative alignment assessment, VT should also be considered in surgical planning. Further research is needed to evaluate the long-term impact of VT on surgical outcomes. Level II, diagnostic: This prospective cohort study, which investigates the relationship between static and dynamic knee alignment, is considered Level II evidence as a diagnostic study. It aims to develop a better understanding of diagnostic criteria by comparing different measurement methods in a consecutive series of patients.