Return to sport and reoperation rates in patients under the age of 20 following primary anterior cruciate ligament reconstruction: risk profile comparing three patient groups predicated upon skeletal age

Background: With sports specialization and level of competition on the rise, anterior cruciate ligament reconstruction (ACLR) in skeletally immature athletes has increased significantly in recent years. Reports have demonstrated that the revision ACLR rate is higher and return to sport (RTS) rate is lower in this high-risk population. The purpose of this study is to evaluate two year clinical outcomes of three groups of primary ACLR in pediatric and adolescent athletes under the age of 20 based on skeletal age, school grade distribution, and ACLR technique with a focus on RTS and incidence of second surgery. Methods: This is a prospective evaluation of 324 athletes under 20 years of age following ACLR with minimum 2-year follow-up. The surgical technique was selected predicated upon skeletal age which includes the all-epiphyseal (AE) technique with hamstring autograft in the youngest cohort in lower and middle school (Group 1), the partial transphyseal (PTP) and complete transphyseal (CT) with hamstring autograft performed for athletes in the middle cohort (Group 2), and bone tendon bone autograft (BTB) in the skeletally mature high school athletes (Group 3). Preoperative demographics, sport, mechanism of injury, intraoperative findings, RTS, and second surgery data were collected. Athletes were followed for a minimum of 24 months with serial clinic visits. Results: The mean chronological age of the entire cohort was 15 years (range 8 to 19 years) with 55% males. The mean post-operative duration of follow-up was 3.25 years (range 2-7 years). The three cohorts included 49 patients (15%) in Group 1 (mean age: 12y), 66 (20%) in Group 2 (mean age: 14.3y), and 209 (65%) in Group 3 (mean age: 16.2y). Group 2 athletes had a significantly higher revision ACLR rate (20%) compared to Groups 1 (6%) and 3 (6%) (Table 1). When separated based on gender, there was a significantly higher rate of revision ACLR for males between groups. Post-hoc analysis revealed a significantly higher rate of revision ACLR for the males in Group 2 (24%) compared to Groups 1 (8%) and Group 3 (5%). Group 2 athletes also had significantly lower RTS rates (85%) compared to Groups 1 (100%) and 3 (94%). Multi-variate logistic regression analyses demonstrated that Group 2 athletes were more than 4 times more likely to have a revision ACLR compared to Group 3 (OR: 4.21, 95% CI: 1.09 – 16.3, p=0.037). With regard to gender, females were nearly three times more likely to have a contralateral ACLR compared to males (OR: 2.80, 95% CI: 1.11 – 7.06, p=0.029). Conclusions/Significance: The rate of revision ACLR was significantly higher and the RTS rates significantly lower in Group 2 compared to Groups 1 and 3. This age-related risk profile may be used to counsel athletes and parents preoperatively regarding the expectations of surgery with respect to revision ACLR and RTS rates. This study is unique in that it describes a particularly high-risk group of skeletally immature athletes within what is already considered to be a high-risk population of athletes less than 20 years of age. We believe this is the first report to identify a skeletally immature cohort of athletes bridging middle school and high school with higher revision ACLR and lower RTS rates compared to a younger cohort of skeletally immature lower and middle school athletes and an older group of skeletally mature high school and college adolescents. This study also reports relatively low rates of revision ACLR and high rates of RTS in the youngest cohort of skeletally immature athletes. [Table: see text]