Poster 350: Outcomes of Anterior Closing Wedge High Tibial Osteotomy in Patients Undergoing Revision ACL Reconstruction

OBJECTIVES: Graft failure rates following anterior cruciate ligament (ACL) reconstruction have been reported up to 30%. According to the literature, one anatomic variant linked to graft reinjury is a high posterior tibial slope. As a result, surgeons are exploring the effectiveness of slope reducing high tibial osteotomy (HTO) to reduce the subsequent reinjury risk. While cadaveric models indicate that this procedure decreases the forces across the ACL graft, there is limited evidence demonstrating its efficacy in clinical trials. Therefore, the purpose of this study was to compare self-reported patient outcomes between patients undergoing ACL revision surgery with a slope reducing high tibial osteotomy and matched controls undergoing revision ACL reconstruction without slope reducing HTO. We hypothesized that patients undergoing ACL+HTO would exhibit similar outcomes with a low failure rate when compared to their matched counterparts. METHODS: A retrospective matched-case control study was conducted for patients undergoing ACL revision reconstruction from 2018 to 2021, utilizing a single surgeon database (n = 1,781). Patients in the HTO group were included if they were at least one year out from surgical ACL reconstruction and slope reducing osteotomy. Patients were excluded if they were undergoing primary ACL reconstruction or no concomitant ACL reconstruction. Patients in the ACL+HTO group were age, gender, and setting-matched to a control group of patients undergoing revision ACL reconstruction. Descriptive patient demographic and surgical data were obtained, including pre/postoperative posterior tibial slope((o)) for the HTO group. Complications and injury surveillance was conducted throughout the postoperative follow-up period. Primary outcome measures included the Single Assessment Numeric Scale (SANE), and graft failure rates at 24 months. Secondary outcomes included return to sport rate/level and postoperative complications (infection, loss of motion, deep vein thrombosis, etc). Generalized linear models were conducted using parametric and nonparametric equivalents to compare baseline and outcome measures between groups with an a-priori alpha level of .05. RESULTS: From a group of 364 revision ACL reconstructions, 9 patients met the inclusion criteria for the ACL+HTO group (Table 1). This group was age, gender and revision matched to 30 patients in the control group. Baseline comparisons revealed that the ACL control group weighed more than the experimental group (198.2 ±26.4 vs 183.7 ±21.7, P <.001), however all other comparisons were not statistically different. The mean pre operative posterior tibial slope was 19.2(o) ±4.1(o) and 7.7(o) ±2.3(o) following HTO (mean diff: -11.5(o), P <.001). Mean time to follow-up was 1.82 ±0.3 years. At follow-up, there were no statistical differences in self-reported knee function (SANE score), graft reinjury rate, rate of return-to- sport, or level of return to sport between groups (Table 3). There were no graft reinjuries reported in the ACL+HTO group and approximately 85.8% returned to some level of sporting activity with 42% returning to a level I or II cutting and pivoting sport. CONCLUSIONS: Preliminary evidence provided in the current study suggests that slope reducing HTO in the setting of revision ACL reconstruction for large posterior tibial slope deformities is effective at correcting malalignment and avoiding graft failure out to 2 years. This procedure also holds promise to allow a majority of patients to return to various levels of sporting activities. To our knowledge, this is the first comparative study comparing the intermediate outcomes of this subpopulation to a matched revision ACL cohort. While these data do provide evidence for ongoing investigation, it is important to note that this pilot study is underpowered and we strongly recommend the performance of larger clinical trials to confirm these results.