Does tibial slope modification influence early recovery in mechanically aligned robotic-assisted total knee arthroplasty? A retrospective cohort study

Purpose Tibial slope influences posterior cruciate ligament tension, flexion-gap mechanics, and mid-flexion stability in cruciate-retaining total knee arthroplasty (TKA). Robotic assistance enables precise slope adjustment, yet the clinical relevance of intentional slope modification for early postoperative recovery remains unclear. This study evaluated whether tibial slope modification during mechanically aligned robotic-assisted CR-TKA affects early functional outcomes. Methods A retrospective cohort of 55 consecutive mechanically aligned robotic-assisted CR-TKAs performed using the VELYS™ system with ATTUNE® implants (January–July 2024) was analyzed. Patients were stratified by tibial slope change relative to baseline: Decreased (n = 42), Neutral (±0.5°; n = 5), and Increased (n = 8). Early recovery endpoints included postoperative day-1 (POD1) ambulation, POD1 pain score, length of stay, and postoperative knee range of motion. Inter-group differences were assessed using one-way ANOVA with non-parametric sensitivity testing, and linear regression evaluated slope change (Δ°) as a continuous variable. Results No significant differences were observed between groups in POD1 ambulation (p = 0.78), POD1 pain (p = 0.87), length of stay (p = 0.58), postoperative flexion (p = 0.69), or extension (p = 0.27). Findings were consistent on non-parametric analysis. Regression demonstrated no meaningful association between slope change and early outcomes (all p > 0.05; R 2 < 0.03), with a near-flat slope–ambulation relationship (β = 0.49, p = 0.28). Conclusion Within a mechanically aligned robotic CR-TKA workflow, tibial slope modification was not associated with early postoperative recovery. Individualized slope adjustment may have limited impact on short-term functional outcomes. Larger prospective studies incorporating PROMs and long-term follow-up are warranted.