Descriptive Epidemiology of Complete ACL Tears in the Skeletally Immature Population: A Multicenter Investigation of the Pluto Study

BACKGROUND: ACL injuries are being seen with increased frequency in pediatric and adolescent patients. Understanding patient and injury characteristics as well as treatment strategies are important to help guide future surgical decisions in the care of these young patients. HYPOTHESIS/PURPOSE: To report the demographic characteristics and descriptive epidemiology of a large cohort of skeletally immature patients with complete ACL tears through a prospective, multicenter study. METHODS: At 10 geographically diverse institutions in the United States, consecutive skeletally immature patients diagnosed with complete ACL tears between January 2016 and April 2020 were enrolled. Treatment was provided by one of 23 participating orthopedic surgeons. Patient demographics, including chronological and skeletal age, sex, race, ethnicity, as well as anthropometric measures, mechanism of injury, and ACL treatment type were collected. RESULTS: 748 skeletally immature patients were included in the final cohort; the mean chronological age was 12.3 years, and 62.3% were male. Mean skeletal age (13.2 years) was on average 0.9 years higher than mean chronological age (p<0.001). The median BMI percentile for the cohort was 71(st) (IQR, 45-88), and 10.8% were classified as obese (≥95(th) percentile). 5.3% reported a previous ipsilateral knee injury, and 32.5% had a family history of ACL injuries. Sport was the predominant mechanism of injury (89.4%), with non-contact injuries the most common (61.5%). When stratified by sex, non-contact injury was significantly higher in females (68.3%) than males (57.4%) (p=0.005). The most common sport resulting in an ACL tear among males was football (41.2%) and among females was soccer (44.2%) (p<0.001). 99.9% percent of skeletally immature patients were treated surgically by one of four reconstruction techniques: transphyseal (52.7%), partial transphyseal (7.1%), all-epiphyseal (13.1%), and the physeal sparing iliotibial band (ITB) technique (27.0%). One patient underwent non-operative treatment. The most common surgical techniques for patients with a bone age younger than 13 years were physeal sparing with ITB (56.7%) and all-epiphyseal (21.8%), while in patients with a bone age of 13 years and older, transphyseal (71.1%) and physeal sparing with ITB (11.9%) were most common (p<0.001). CONCLUSION: This multicenter, prospective study is the first to describe the characteristics of an exclusively skeletally immature cohort with complete ACL tears. Almost all patients were injured during sports, surgical treatment was overwhelmingly the treatment of choice, and preferred surgical techniques varied based on skeletal age.