Paper 01: Clinical Outcomes Following ACL Reconstruction with Slope Reducing High-Tibial Osteotomy: A Matched Case-Control Study
Authors: Lowe Walter , Mansour Alfred , Reyes Griffin , Higbie Steven , Kleihege Jacquelyn , Eastman Maddie , Suarez David , Bailey Lane 
Published: August 2024

Objectives: Despite recent efforts, the reinjury rate following anterior cruciate ligament (ACL) reconstruction remains high, with documented reports of up to 30%. According to retrospective evidence, high posterior tibial slope (≥12°) has been identified as an anatomic risk factor contributing increased graft reinjury rates. Surgeons are therefore exploring the effectiveness of slope reducing high tibial osteotomy (SRO) as a means of modifying this potential risk factor. While cadaveric models suggest that this surgical procedure decreases the forces across the ACL graft, there are few clinical trials examining its’ safety and clinical effectiveness in patient samples. Therefore, the purpose of this study is to compare functional performance and graft reinjury rates between patients undergoing ACL reconstruction surgery with SRO versus matched controls undergoing isolated ACL reconstruction. We hypothesized that patients undergoing ACL reconstruction with SRO would exhibit similar performance outcomes with a low failure rate when compared to their matched counterparts. Methods: A retrospective matched-case control study was conducted in accordance with the ‘Strengthening the Reporting of Observational Studies in Epidemiology’ guidelines for patients undergoing ACL reconstruction (Figure 1), utilizing a single surgeon database (n=1978). The experimental group (ACL+SRO) consisted of patients ages 18-50 years old that were at least 24-months out of ACL reconstruction with a concomitant SRO. Patients were age, sex, and revision-matched to a cohort of individuals undergoing isolated ACL reconstruction. Exclusion criteria consisted of contralateral knee injury (<24 months prior to surgery), isolated coronal-plane high tibial osteotomy, and multiligamentous knee injury. Patient demographics and surgical data were obtained, including pre/postoperative posterior tibial slope (o) for the ACL+SRO group and presurgery activity levels. Data were gathered at return to sports and included knee range of motion, single-leg balance, single-leg hop testing, and self-reported International Knee Documentation Committee and ACL-Return to Sports After Injury (ACL-RSI) scores. 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 two-years. Secondary outcomes included return to sport rate and level of participation, and postoperative complications (infection, loss of motion, deep vein thrombosis, etc). Generalized Linear Models and chi-square analyses were conducted using SPSS (IBM, Chicago IL) to compare groups with an a-priori alpha level of .05. Results: Of the 1978 patients in the ACL registry, 48 met the study criteria and were included in the analyses (ACL+SRO group, n=24; Isolated ACL group, n=24). Baseline comparisons revealed that the ACL+SRO group had a higher bodyweight (200.9 ±35.1 vs 179.7 ±33.9, P <.001) and subsequent higher body mass index (29.7 ±4.6 vs 26.7 ±5.0, P = .044), Table 1. Additional baseline differences included ACL graft type, and staged procedures ( P < .05, Table 2). The mean preoperative posterior tibial slope was 17.0° ±2.7° and 7.0° ±2.2° following SRO (mean diff: -10.0°, P <.001). Table 3 depicts the comparisons at return to sport, with the ACL+SRO group demonstrating longer time to return ( P < .001) and lower ACL-RSI scores ( P = .027). At 2 years, there were no statistical differences in SANE score (85.3 ±7.3 vs 88.2 ±9.7, P = .349), graft reinjury rate (0.0% vs 0.0%, P = 1.000), rate of return to sports (85.7% vs 91.7%, P = .844), or level of return to sports between groups with 45.8% (n=11) of the ACL+SRO group returning to a level I or II cutting and pivoting sport versus 54.2% (n=13) in the Isolated ACL group ( P = .656). There were no reported postoperative infections or deep vein thromboses in either group (P > .05). Conclusions: The current study suggests that SRO in the setting of ACL reconstruction for large posterior tibial slope deformities is effective at correcting malalignment, restoring objective and self-reported function, 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 examining the return to sports and 2-year outcomes of this population to a matched isolated ACL cohort. While these data do provide evidence for ongoing investigation, we recommend the performance of larger clinical trials to confirm these results. [Figure: see text][Figure: see text][Figure: see text][Figure: see text]