Combined Root and Body Lateral Meniscus Tears in the Adolescent Population: An Underrecognized and Underreported Tear Pattern

Abstract

Background:

A distinct tear pattern of the lateral meniscus involving 2 separate tears—one involving the posterior root and the other involving a radial tear of the body of the meniscus—has been anecdotally observed in patients undergoing anterior cruciate ligament (ACL) reconstruction, but has not been well described in the literature.

Purpose:

To describe the incidence and associations of combined root and body (CRAB) tears in adolescent patients undergoing ACL surgery.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

A retrospective chart review for all patients who underwent primary ACL reconstruction from January 2021 to December 2022 by a single fellowship-trained pediatric sports orthopaedic surgeon at a large metropolitan children's hospital was performed. Operative reports and images among patients undergoing ACL reconstruction were retrospectively reviewed to determine the incidence of CRAB tears. Demographic, injury, and imaging findings were then analyzed with respect to the presence of a lateral meniscus CRAB tear.

Results:

Of the 227 primary ACL reconstructions, 122 (54%) had a tear involving the lateral meniscus. A total of 38 (17%) tears involved the posterior root, and 23 CRAB tears were identified, which represented 10.1% (23/227) of all ACL tears and 60.5% (23/38) of all lateral meniscus posterior root tears. The mean age of patients with CRAB tears was 16.0 ± 1.3 years, with 78% (18/23) being male. The majority, 65% (15/23), had a noncontact injury mechanism. Associated findings included a nonclassic bone bruise pattern (T2 hyperintensities on preoperative magnetic resonance imaging divergent from the classic posterolateral tibial plateau or central one-third of the lateral femoral condyle) in 43% (10/23), a deep medial collateral ligament injury in 57% (13/23), a medial meniscus tear in 43% (10/23), and lateral meniscus extrusion in 22% (5/23). Patients with CRAB tears were 3.7 times more likely to have nonclassic bone bruising (43% vs 17%; P = .039) and a higher body mass index (BMI) (26.6 ± 5.8 vs 23.9 ± 4.9; P = .048) than patients with ACL tears without CRAB tears. Of note, 74% (17/23) of the CRAB tears were missed by the radiologist.

Conclusion:

CRAB tears are underdiagnosed preoperatively and are relatively common injury patterns, especially in the setting of adolescent patients undergoing primary ACL reconstruction with higher BMI and nonclassic bone bruising. If a radial tear of the meniscal body is identified arthroscopically, the surgeon should carefully evaluate the posterior root of the meniscus to ensure there is not a second tear that could otherwise be potentially missed.