Effect of vertical cut on coronal coverage and rotation of tibial component in Oxford unicompartmental knee arthroplasty

OBJECTIVE: This study was performed to investigate the influence of a standard Oxford vertical cut on the coronal coverage and rotation of the tibial component and determine whether a relationship exists between coverage and rotation. METHODS: We retrospectively analyzed 71 patients with anteromedial osteoarthritis of the knee treated by Oxford unicompartmental knee arthroplasty in one center from October 2016 to October 2017. The distance of coronal coverage was measured on a postoperative anteroposterior view of the tibial component. Two different reference lines between the lateral wall of the tibial component were defined as rotation angle α and β, respectively, on a computed tomography scan. RESULTS: The mean distance was 0.3 ± 1.1 mm. The mean angle α and β were 5.7° ± 4.6° and 8.4° ± 4.6°, respectively. There were no significant differences in the distance according to the tibial component rotation or in the α and β angles according to the coronal coverage. No significant correlation was found between the α and β angles and the distance. CONCLUSION: A standard tibial vertical cut caused various changes in coronal coverage and rotation of the tibial component. The rotation of the tibial component did not affect coverage within a certain range.