Evaluation of Partial Transection versus Synovial Debridement of the ACL as Novel Canine Models for Management of ACL Injuries

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A major hurdle in investigating important clinical questions in knee ligament treatment is a lack of valid translational animal models. This study characterizes the effects of partial transection versus synovial debridement of the anterior (cranial) cruciate ligament (ACL) in dogs. A total of 27 adult purpose-bred research hounds underwent surgery and were assessed over the following 8 weeks. Dogs were randomized into the following three ACL status groups: sham control (n = 9), intact ACL with synovial debridement (exposed ACL) (n = 9), and partial transection of the ACL (partial tear ACL) (n = 9). Dogs in the exposed ACL group and partial tear ACL group had significantly (p < 0.05) more severe lameness, pain, effusion, reduced function, and reduced comfortable range of motion compared with controls, with the partial tear ACL group being most severely affected. More severe ACL and whole-joint pathology, and radiographic scores for osteoarthritis were present in the partial tear ACL group compared with exposed and/or sham control group. On the basis of these findings, biologic components of ACL injury (exposed ACL) played a role in whole-joint inflammation, but the clinical and pathological effects were more severe when both biologic and biomechanical components were present (i.e., partial tear ACL). These novel canine models were successfully developed to evaluate partial transection versus synovial debridement of the ACL and these models will be used to evaluate treatment options for acute management of ACL injuries.