Malposition of the tibial components is a well-known complication of unicompartmental knee arthroplasty. In this study, we aimed to ascertain the relationship between the tibial component position and clinical outcomes of unicompartmental knee arthroplasty. We focused on the tibial component height and obliquity in the coronal plane.
Patients with anteromedial osteoarthritis who underwent Oxford mobile-bearing unicompartmental knee arthroplasty (n = 45) were included, and their Oxford knee score was assessed prior to and 1 and 2 years following surgery. We also assessed the postoperative tibial component position in the coronal plane using radiography, measuring the tibial component height and obliquity. We analyzed the sequential change in both clinical scores using repeated measures analysis of variance (p < 0.05). The effects of tibial component position on the clinical outcomes were analyzed using linear regression analysis (p < 0.05).
The Oxford knee score significantly improved 1 year after surgery. The tibial component height and obliquity had a significantly negative correlation with the 2-year postoperative Oxford knee score. They were also correlated significantly with Oxford knee score recovery after unicompartmental knee arthroplasty.
The 2-year postoperative outcomes of Oxford unicompartmental knee arthroplasty depended on the tibial component position. We observed poorer outcomes when the tibial component was placed at a lower level relative to the lateral compartment and when there was an excessive valgus angle relative to the lower limb axis.