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The Relationship of Anterior Cruciate Ligament Insertion Sites to the Distal Femoral Growth Centers: an MRI study

      Introduction

      Anterior cruciate ligament (ACL) injury and reconstruction have become increasingly common in the pediatric and adolescent populations. The ACL is close to the distal femoral physis and posterior epiphysis, a growth center for the distal femur. We sought to explore the changes in the anatomic relationship of the two bundles of the ACL in order to provide guidelines for surgical reconstruction.

      Methods

      We reviewed knee MRIs in patients ages 6-18 (IRB approved), excluding patients with cruciate injury. Standardized measurements of anterior-medial (AM) and posterior-lateral (PL) bundle area, distance from physis and posterior epiphysis to edge and center of each bundle were evaluated for each MRI.

      Results

      154 studies were included. The footprints of each bundle increase predictably with age. The PL bundle footprint is larger than the AM bundle in both genders (16.2±5.3 vs. 12.0±4.1 mm2, p<0.001). The average distance across all groups from the center and edge of the AM bundle to the physis was 8.2±1.9 mm and 7.0±1.8 mm respectively (figure). The average distance of the PL bundle center and edge to the posterior epiphysis was 5.6±1.9 mm and 4.4±1.8 mm respectively. Patients had an increase in the average distance from the AM bundle to the physis with age, which was <10 mm in skeletally immature patients. Males had consistent increase in distance of the PL bundle to the physis. Minimum distance increased gradually with age.

      Conclusion

      We demonstrated increase in area of each bundle footprint with age, with the PL bundle footprint being larger. We found that the AM bundle inserted <10 mm from the distal femoral physis in patients under age 15, closer than previously recognized, while the PL bundle is adjacent to the posterior epiphysis. This should provide better guidelines for surgical reconstruction in the pediatric patient to avoid growth disturbance.