No association between different in tibial resection level and clinical outcomes six months after Oxford unicompartmental knee arthroplasty: a prospective cohort study

Localized tibial strain is one of the hypotheses to explain residual pain after Oxford UKA. We evaluate whether the depth of the vertical cut during tibial resection correlates with medial knee pain. We aimed to investigate the association between the depth of tibial resection and medial knee pain after OUKA. This prospective cohort study enrolled 85 patients (mean age: 64.5 ± 7.7 years) who underwent cemented OUKA at our institute during October 2018-June 2019. The depth of tibial resection was measured intraoperatively as the thickness of the anterior, middle, and posterior parts. The greatest of the three thicknesses was recorded. Medial knee pain was assessed at 6 weeks and followed to 6 months. Patients were divided into the pain (P) and no pain (NP) groups. Preoperative and postoperative radiographic findings and OKS were compared between groups. We used logistic regression to analyze the independent association. The mean preoperative Oxford Knee Score (OKS) was 27.2 ± 7.6. The incidence of medial knee pain was 23.5% at 6 weeks after OUKA. The P group had a significantly lower OKS at 6 weeks compared to the NP group (28.9 ± 9.7 vs 33.7 ± 6.5, p = 0.049). There was no significant difference in the depth of tibial resection between groups. Medial knee pain had resolved by 6 months in all patients, and the 6-month OKS was similar between groups. Medial knee pain was found to be common in the early postoperative period after OUKA, but this pain spontaneously resolved by 6 months. As a range of tibial resection level, post-operative pain is not associated with tibial resection thickness in this study. Level II. The study was approved by the Institutional review board of Siriraj Hospital, Mahidol university. [SIRB 691/2560(EC4)].