The association between restoration of tibial slope and total knee arthroplasty outcomes

Background: The proximal tibia has a characteristic posterior slope, varying between individuals and implicated in biomechanical function. This study evaluated whether restoring the native posterior tibial slope during primary total knee arthroplasty (TKA) improves postoperative functional outcomes. Methods: A retrospective review of 9569 TKA patients from 1998 to 2022 was conducted using a single-centre arthroplasty database. Patients were categorized based on changes in tibial slope: decreased (Group 1, Δ slope <3°), re-created (Group 2, Δ slope -3 to +3°), or increased (Group 3, Δ slope >3°). Preoperative and postoperative anterior and posterior femoral offset ratios were also calculated and analyzed as covariates. Postoperative functional outcomes and range of motion (ROM) were assessed using analyses of covariance (ANCOVAS) and post-hoc pairwise comparisons. Results: Among 609 included patients, tibial slope was decreased in 278 patients (46%, Group 1), re-created in 253 (42%, Group 2), and increased in 78 (13%, Group 3). Group 2 exhibited a 4.8-point higher Knee Society Score at six weeks postoperatively compared to Group 1 (p = 0.004), though scores at other time points and Oxford Knee Scores across all time points showed no significant differences between groups (p > 0.05). Maximal flexion did not differ significantly across groups. These findings were consistent after adjusting for femoral offset ratio changes. Conclusion: Recreation of native tibial slope was associated with a statistically significant but clinically minor improvement in postoperative functional outcome scores. Increasing tibial slope was not associated with improvements in maximal flexion, although this may be confounded by variations in implants utilized. Loe: III (Retrospective cohort study).