role of tibial slope in ACL rerupture: when and how to correct it

Background: Anterior cruciate ligament (ACL) reconstruction failure remains a clinical challenge, with annual surgical volumes increasing significantly. While extrinsic factors such as surgical technique and rehabilitation are well-documented, intrinsic anatomical risk factors, specifically an increased posterior tibial slope (PTS), are increasingly recognized as primary drivers of graft failure and persistent sagittal instability.

Objective: This article evaluates the biomechanical influence of PTS on knee stability, details standardized radiographic measurement methodologies, and describes the surgical technique and clinical outcomes of tibial deflexion osteotomy (TDO) in the management of ACL insufficiency.

Key Points: An increased PTS correlates with elevated static anterior tibial translation and increased sagittal forces on the ACL, often leading to fatigue-related graft failure. Measurement reliability is highest using the Tibial Proximal Anatomical Axis (TPAA) on true lateral radiographs. Surgical correction via a one-stage anterior closing wedge TDO, often performed during revision ACL reconstruction, aims to reduce the PTS to a target value of 2° to 5°. Clinical data indicate that TDO combined with ACL revision significantly improves functional scores, such as the IKDC and Lysholm scales, while effectively preventing subsequent graft rupture. Furthermore, maintaining medial meniscal integrity is critical, as meniscal loss exacerbates the destabilizing effects of a steep PTS.

Conclusion: Tibial deflexion osteotomy is an effective procedure for addressing pathological posterior tibial slope in patients with recurrent ACL instability. The technique provides durable graft protection and favorable functional outcomes, particularly when the PTS exceeds 12° or is associated with significant static anterior tibial subluxation.