The Risk of Growth Changes During Transphyseal Drilling in Sheep With Open Physes

Abstract

A sheep model was used to evaluate the risk of growth disturbances of transphyseal drilling and anterior cruciate ligament (ACL) reconstruction. In group A, comprised of six 4-month-old Merino sheep, the ACL was resected and 5-mm tunnels were drilled and left empty. Unilateral ACL reconstruction using an autologous Achilles tendon graft, extracortical fixation, and tunnel diameters of 5 mm was performed in group B. A single-stranded graft with a diameter of 5 mm was used in group B-1 (N = 6) and a 3-mm double-stranded graft in group B-2 (N = 6). Six months after the procedure, the animals were euthanized. Growth changes were evaluated macroscopically, by magnetic resonance imaging, and by histology. Central growth plate lesions on the tibia did not induce growth abnormalities. On the peripheral femur, posterolateral growth plate injuries with empty tunnels led to a shortening of the lateral femur of 8 mm (7 to 10 mm), a valgus deformity of 12.8 degrees (12 degrees to 14 degrees ), and a flexion deformity of 8.6 degrees (5 degrees to 15 degrees ). Histology revealed a strong bone bridge over the physis and an injury to the perichondral structures. Transphyseal ACL replacements did not cause growth disturbances on either the tibia or the femur, even if a drilling injury of the perichondral structures occurred. Despite consistent physeal damage, ACL reconstructions did not lead to clinically relevant growth disturbances. The results suggest that transphyseal ACL reconstruction procedures might yield similar results in children with substantial growth remaining.