Introduction
Increased posterior tibial slope (PTS) and static anterior tibial translation (SATT) are independent risk factors for anterior cruciate ligament (ACL) graft failure. Previous studies have demonstrated a three-fold increase in graft rupture risk with PTS ≥12° and a similar increase in risk with SATT ≥5 mm. Consequently, slope-reducing osteotomy has largely been reserved for revision ACL reconstruction, with elevated SATT frequently used as an indication for surgery. However, it remains unclear whether correcting PTS to a lower postoperative target can restore tibiofemoral alignment and normalise SATT in both primary and revision ACL-deficient knees. The purpose of this study was to evaluate the radiographic effect of supratubercle deflexion osteotomy on PTS and SATT in a consecutive series of primary, revision and second-revision ACL reconstructions.
Methods
A retrospective review was performed of all consecutive supratubercle anterior closing-wedge (deflexion) osteotomies performed by a single or combined surgeon over a 2.5-year period. Patients undergoing primary, revision and second-revision ACL reconstruction were included. Radiographic measurements included posterior tibial slope and static anterior tibial translation obtained preoperatively and at a minimum of 3 months postoperatively. Patients with greater than 12 months postoperative MRI follow-up underwent assessment of graft ligamentisation; these findings will be reported in an updated abstract by the time of the meeting.
Results
Forty-two patients were included comprising 24 primary, 10 revision and 8 second-revision ACL reconstructions.
In the primary cohort, mean PTS decreased from 14.2° to 6.9° (Δ 7.3°), while mean SATT improved from 7.8 mm to 1.5 mm (Δ 6.3 mm).
In revision cases, mean PTS decreased from 15.0° to 5.7° (Δ 9.4°), while mean SATT improved from 13.5 mm to 3.8 mm (Δ 9.7 mm).
In second-revision cases, mean PTS decreased from 15.5° to 5.4° (Δ 10.1°), while mean SATT improved from 13.2 mm to 3.2 mm (Δ 10.0 mm).
Within the revision cohort, patients with post operative PTS of 3-6° corrected SATT to 2.73mm, where as PTS 6-9°, resulted in a SATT 4.84mm.
Conclusion
Supratubercle deflexion osteotomy reliably reduced posterior tibial slope and substantially improved static anterior tibial translation across primary, revision and second-revision ACL reconstruction populations. Correction of PTS to a postoperative target of approximately 6–7° resulted in near normalisation of SATT in primary cases and marked reduction in chronic anterior tibial subluxation in revision settings. However slope of >6 degrees in the revision setting resulting in higher SATT, suggesting there should be different targets for the revision and primary setting. Further follow-up is required to determine whether restoration of tibiofemoral alignment translates into improved graft maturation and survivorship.
