The Locations of Anterior Cruciate Ligament Tears in Pediatric and Adolescent Patients: A Magnetic Resonance Study.

BACKGROUND: Recently, a resurgence of interest has been noted in anterior cruciate ligament (ACL) preservation in pediatric and adolescent patients. Different tear types, defined by their tear location, require different preservation techniques: proximal and distal avulsion tears can be treated with arthroscopic primary repair, whereas primary repair with biological scaffold has been proposed for midsubstance tears. The goal of this study was to assess the distribution of different tear types in pediatric and adolescent patients, as these are currently unknown.

METHODS: A retrospective search in an institutional radiographic database was performed for patients under 18.0 years undergoing knee magnetic resonance imaging (MRI) for ACL tears between June 2005 and June 2016. Patients with reports of chronic tears, partial tears, and multiligamentous injuries were excluded.Tear locations were graded using MRI as: proximal avulsion (distal remnant length >90% of total length; type I), proximal (75% to 90%; type II), midsubstance (25% to 75%; type III), distal (10% to 25%; type IV), and distal avulsion (<10%; type V).

RESULTS: A total of 274 patients (59% girls; mean±SD age, 15.1±2.1 y; range, 6.9 to 18.0 y) were included. Frequency of type I tears was 15%, type II 23%, type III 52%, type IV 1%, and type V 8% (of which 7% had bony avulsion).Prevalence of tear types varied with age. At age 6 to 10 years, 93% were type V (bony) avulsion tears. At age 11 to 13 years, 32% were type I, 16% type II, 32% type III, and 16% type V. At age 14 to 17 years, type III tears were more common (57%) than type I (14%), type II (25%) and type V (2%) tears.

CONCLUSIONS: It was noted that the ACL was torn at different locations depending on the patients' age. These data provide more information on the potential application for ACL preservation in pediatric and adolescent patients. Future studies correlating these findings with arthroscopy are needed before using MRI for preoperative planning of ACL preservation surgery.

LEVEL OF EVIDENCE: Diagnostic level III.