Failed anterior cruciate ligament reconstructions have both increased posterior tibial slope and increased posterior tibial plateau offset

ABSTRACT Purpose This study introduces the posterior tibial plateau offset (PTO). It was hypothesised that (1) the PTO is reliably quantifiable and (2) correlates with the posterior tibial slope (PTS). Methods The study involved lateral radiographs of patients who sustained an anterior cruciate ligament (ACL) graft failure and a control group. Exclusion criteria were skeletal immaturity, osteoarthritis (Kellgren and Lawrence grade > I), lateral radiographs with <15 cm of tibial shaft, or malrotated radiographs. The PTS was measured in both groups. The PTO was defined as the relative distance from the posterior tibial plateau to the tibial shaft axis in relation to the sagittal diameter of the tibial plateau (in%). Linear correlation assessed the PTS to PTO association. Results A total of 146 patients (ACL graft failure, n = 103; control group, n = 43; 45% female, 60% left knees) were included. Mean overall PTO was 82% ± 7% (1%–35%), and mean PTS was 12° ± 3 (7–20). The PTS and PTO showed a moderate positive correlation in the overall collective ( r = 0.5; p < 0.001), ACL graft failure group ( r = 0.49; p < 0.001), and control group ( r = 0.69; p < 0.001), indicating a higher slope corresponded to a greater PTO. There was no statistical difference in PTO between the ACL failure and the control group (82% vs. 83%, p < 0.05). ICC between three raters was (0.8–0.9; p < 0.05). Conclusion The PTO is a simple and repeatable measurement. A higher PTS is associated with a greater PTO, and the variability of the PTO across the patients with ACL graft failure and the control group was high. When planning osteotomy levels in the highly sloped proximal tibia, the PTO may be considered to optimise individualised planning for patients with failed ACL reconstruction. Level of Evidence Level V.