An animal model to study ACL reconstruction during growth.

Controversy exists in the literature regarding the most appropriate treatment for anterior cruciate ligament (ACL) ruptures in the skeletally immature patient. To study the histological and biomechanical stages following ACL reconstruction during growth, it is necessary to establish an equivalent model to replicate the situation of an immature skeleton. In the present study we evaluated a large animal model of ACL reconstruction during growth using skeletally immature sheep. In contrast to existing models we did not intend to provoke growth disturbances. Instead, we identified those criteria known to be essential to prevent growth disturbances in the human situation and transformed them into an animal model. Applying those criteria to skeletally immature sheep at an age of four months, we performed a fully transphyseal ACL reconstruction of their right knee. The contralateral knee served as a control. The sheep were then sacrificed 3, 6, 12 and 24 weeks after surgery. This animal model is described in detail in the present manuscript. Basic science data are presented in order to 1) make it easier for other research groups to study ACL reconstruction during growth using our model and 2) to improve this model by modifying the one or other detail of the proposed technique. Using this model, remaining open questions concerning ACL reconstruction during growth can be addressed in future studies.