Return to Sport and Re-Operation Rates in Athletes Under the Age of 20 Following Primary Anterior Cruciate Ligament Reconstruction: Risk Profile Comparing Three Patient Groups Predicated Upon Skeletal Age

OBJECTIVES: ACL injury in the skeletally immature athlete has become an increasingly significant clinical problem in recent years. The high-risk population of athletes less than 20 years of age has the lowest return to sport (RTS) rates and highest second surgery rates following ACL reconstruction (ACLR). The purpose of this prospective study is to evaluate the 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. We hypothesize that the youngest (Group 1) and oldest (Group 3) cohorts will have lower revision ACL rates and higher RTS rates compared to the middle (Group 2) cohort of athletes. METHODS: 306 patients less than 20 years of age underwent primary ACLR in the senior authors’ practice. Group 1 had 3-6 years of growth remaining and was comprised of lower and middle school athletes through 7th grade. Group 1 athletes received an all-epiphyseal (AE) hamstring autograft ACLR. Group 2 had 2-3 years of growth remaining and included predominantly 8th and 9th grade athletes. Group 2 was treated with either a partial transphyseal (PTP) or complete transphyseal (CT) hamstring autograft ACLR. Group 3 included skeletally mature high school & collegiate athletes treated with a CT ACLR using a bone-tendon-bone (BTB) autograft. 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 three cohorts included 47 athletes (15%) in Group 1 (mean age: 12.0 + 1.5y), 64 athletes (21%) in Group 2 (mean age: 14.3 + 1.3y), and 195 athletes (64%) in Group 3 (mean age: 16.2 + 1.8y). The rate of revision ACL was higher in Group 2 at 20% (13/64 athletes) as compared to Group 1 at 6% (3/47 athletes) and Group 3 at 6% (11/195 athletes) (p= 0.001). Group 2 athletes had a significantly lower RTS at 86% as compared to Groups 1 and 3 at 100% and 94% respectively (p=0.009). Group 2 athletes also had a significantly lower RTS at the same level 75% as compared to Groups 1 and 3 at 96% and 82% respectively (p=0.017). Using multivariate logistic regression, Group 2 athletes were nearly 5 times more likely to have a Revision ACLR compared to Group 3 BTB athletes (OR: 4.92, 95% CI: 1.19 - 20.34, p=0.028). Females were nearly 3 times more likely to have a contralateral ACLR as compared to males (OR: 2.83, 95% CI: 1.09 - 7.34, p=0.033). CONCLUSION: As we hypothesized, the rate of revision ACLR and overall incidence of second surgery was higher and the RTS rate lower in Group 2 athletes compared to Groups 1 and 3 athletes. Group 2 athletes may be at higher risk because upon completion of their rehabilitation and RTS clearance process they are joining a cohort of competitive, now skeletally mature high school athletes who have not lost a year of athletic competition and development of sport-specific skills. Ultimately, the athlete’s skeletal age determined the choice of surgical technique, but the grade levels noted above demarcated the three surgical cohorts with only a few outliers. We believe grade level is important as this will most often dictate the level of competition that the athlete in question is exposed to after recovery and return to sport. This age and school grade risk profile is useful to counsel athletes and parents preoperatively regarding the expectations of surgery with regard to RTS and the risk of second surgery.