Summary

Slope-reducing high tibial osteotomy improves midterm outcomes, reduces graft failure risk, and disrupts the cycle of ACL graft rerupture in patients with increased tibial slope undergoing revision ACL reconstruction.

Abstract

Background

Increased tibial slope is associated with greater tibial translation and higher failure rates in ACL reconstruction. Cadaveric studies have demonstrated that slope-reducing high tibial osteotomy (SR HTO) can decrease ACL graft forces and anterior tibial translation under axial loads. However, the impact of SR HTO on the midterm outcomes of ACL revision surgery has not been thoroughly evaluated.

Purpose

To assess the midterm functional outcomes following slope-reducing osteotomy in patients undergoing revision ACL reconstruction.
Study Design: Prospective cohort study; Level of evidence, 2.

Methods

This single-center study included patients scheduled for revision ACL reconstruction between 2016 and 2022 who had an increased tibial slope of ≥15 degrees. Exclusion criteria were BMI > 35 Kg/m2 and multi ligament injuries Tibial slope was measured using full-length standing lateral radiographs relative to the tibial mechanical axis. The revision procedure was staged in two phases. First, the SR HTO was performed using an anterior closing wedge technique with tibial tubercle osteotomy for access. A 3D-printed, patient-specific cutting jig guided the slope osteotomy while maintaining or correcting coronal plane alignment. The targeted postoperative tibial slope was between 6 and 8 degrees. Fixation was achieved with either staples or a locking plate, and bone grafting of tibial tunnels was completed. Four months later, the ACL graft was reimplanted. Patients were followed at 6 months and then annually. Outcome measures included the ACL-RSI, IKDC, KOOS, return to sports and graft failure. Adverse events were predefined and recorded.

Results

A total of 42 patients were included, with a mean preoperative tibial slope of 18.6±2.7 degrees and a mean postoperative slope of 7.2±2.7 degrees. The mean age was 25.1±6.7 years, with a male-to-female ratio of 1.4, and a mean BMI of 24.4±4.4 kg/m². SR HTO was performed for first-time ACL revision in 74% of cases, second revision in 21%, and third revision in 5%. Cartilage lesions (Outerbridge grade ≥2) were present in 79% of patients, with the medial compartment involved in two-thirds of these cases. The mean follow-up period was 5±2.1 years, with no patients lost to follow-up. There were no cases of ACL graft failure recurrence. Significant improvements were observed in the ACL-RSI (46.9±20.4 to 55.3±17.6, p=0.01), IKDC (60.1±14.9 to 69.4±11.6, p<0.001), and KOOS sport subscale (42.8±25.9 to 64.8±27.9, p<0.001). Adverse events occurred in 9.7% of patients, including secondary displacement and varus collapse (2/41), deep infection (1/41), and delayed union (1/41). No cases of secondary knee hyperextension were observed at the final clinical evaluation. Return to sport was achieved in 70.7% of patients, with half participating in level I sports according to Hefti et al.'s classification.

Conclusion

Slope-reducing high tibial osteotomy effectively reduces the risk of ACL graft re-tear in patients with increased tibial slope ≥15 degrees, leading to improved functional outcomes and high rates of return to sport. The procedure demonstrates strong midterm safety and efficacy, making it a valuable strategy in revision ACL reconstruction.