Association between posterior tibial slope and sagittal anteroposterior position of the tibial tunnel after primary anterior cruciate ligament reconstruction

Aims: In anterior cruciate ligament (ACL) reconstruction, sagittal tibial tunnel placement is an important determinant of surgical success. Posterior tibial slope (PTS) may influence anterior tibial translation and graft-loading. This study evaluated the relationship between the PTS and sagittal tibial tunnel position (AP%) after isolated primary ACL reconstruction. Methods: Eighty-seven patients were retrospectively reviewed in this study. On postoperative true lateral radiographs, PTS and tibial tunnel AP (%) were measured and normalized to the tibial plateau length: AP (%)=(tunnel distance/plateau A-P length)×100. True lateral quality was assessed using the posterior condylar superposition offset (PCSO), and radiographs with PCSO >5 mm were excluded. Reliability was assessed using the intraclass correlation coefficients (ICC). The association between PTS and AP (%) was tested using Spearman’s correlation and multiple linear regression [AP (%) dependent; PTS and PCSO predictors]. Results: The mean PTS was 13.70±3.05° (7.85-20.16). The sagittal anteroposterior length of the tibial plateau was 43.85±3.89 mm (35.57-54.45 mm), and the sagittal distance from the anterior edge to the center of the tibial tunnel was 12.82±3.58 mm (6.64-21.40 mm). The mean AP (%) was 29.23±7.76 (16.40-46.42). The measurement reliability was high for both PTS and AP (%). A moderate, statistically significant negative correlation was found between the PTS and AP (%) (ρ=-0.431; p<0.001; 95% bootstrap CI: -0.595 to -0.246). In the multiple regression analysis, PTS was independently and negatively associated with AP (%) (B=-1.154; p<0.001; ≈1.15-point lower AP (%) per 1° higher PTS), whereas PCSO was not significant (p=0.680). Conclusion: As the PTS increased, the tibial tunnel was positioned more anteriorly in the sagittal plane. PTS may influence the radiographic assessment of the tibial tunnel position and potentially intraoperative targeting. Prospective PTS-stratified studies incorporating 3D tunnel position analysis with functional and clinical outcomes are required.