Does native posterior tibial slope restoration improve postoperative flexion and clinical outcomes after total knee arthroplasty? A systematic review and meta-analysis

Background Restoration of the native posterior tibial slope (PTS) has gained increasing attention in total knee arthroplasty (TKA), particularly with the adoption of personalized and functional alignment strategies. Although preservation of sagittal anatomy may theoretically improve knee kinematics and clinical outcomes, the clinical benefit of restoring native PTS remains unclear. This systematic review and meta-analysis aimed to evaluate the association between native PTS restoration and postoperative clinical outcomes after TKA. Methods A systematic review and meta-analysis was performed in accordance with the PRISMA guidelines. PubMed/MEDLINE, Embase, and Web of Science were searched for comparative studies evaluating postoperative outcomes according to the degree of deviation from native PTS after primary TKA. Study-specific PTS categories were harmonized into restored and non-restored groups according to the thresholds reported in each study, and continuous outcomes were pooled as mean differences (MDs) using random-effects models. An exploratory subgroup analysis restricted to cruciate-retaining (CR) TKA and sensitivity analyses according to restoration threshold and leave-one-out analyses were performed. Risk of bias was assessed using the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool, and certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Results Twelve studies were included in the systematic review, of which eight provided data suitable for quantitative synthesis. Pooled analyses demonstrated no significant differences between the restored and non-restored groups in FJS-12 (MD, 3.53; 95% CI, − 4.33 to 11.40; I² = 84.2%), KSS Function (MD, 1.16; 95% CI, − 3.69 to 6.02; I² = 65.1%), KSS Knee (MD, 0.48; 95% CI, − 1.29 to 2.25; I² = 27.4%), or postoperative ROM/flexion (MD, 0.35°; 95% CI, − 0.14° to 0.85°; I² = 0%). In the CR subgroup, no significant differences were observed in KSS Function, KSS Knee, or ROM/flexion (MD, 0.33°; 95% CI, − 0.23° to 0.90°). The findings were not altered by stratification according to restoration threshold or by leave-one-out analyses. Findings from studies not amenable to quantitative pooling were inconsistent. The certainty of evidence was low for FJS-12 and KSS Function and moderate for KSS Knee and ROM/flexion. Conclusions Current evidence does not demonstrate a clinical benefit of native PTS restoration after TKA in patient-reported outcomes or postoperative ROM/flexion, and this finding was consistent in CR TKA. Native PTS should therefore be considered within the broader context of patient-specific alignment rather than as an isolated surgical target. Level of evidence Level III, systematic review and metaanalysis of Level III studies. Clinical trial number Not applicable.