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

Purpose: A sheep model was used to evaluate the risk of growth disturbances of transphyseal drilling and anterior cruciate ligament (ACL) reconstruction. Methods: 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. Results: 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° (12° to 14°), and a flexion deformity of 8.6° (5° to 15°). 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. Conclusions: Despite consistent physeal damage, ACL reconstructions did not lead to clinically relevant growth disturbances. Clinical Relevance: The results suggest that transphyseal ACL reconstruction procedures might yield similar results in children with substantial growth remaining.