In vivo evaluation of intra-articular protection in a novel model of canine cranial cruciate ligament mid-substance elongation injury.

Objectives: To evaluate the effects of intra-articular protection (IAP) on the canine cranial cruciate ligament (CrCL) and stifle in a CrCL midsubstance elongation injury model.

Study Design: Experimental longitudinal cohort study.

Animals: Skeletally mature female mixed breed hounds (n=12; mean+/-SEM weight, 25.6+/-0.7 kg).

Methods: After CrCL elongation in 1 stifle of each dog, IAP was applied in 6 joints. In vivo assessment included radiographs, cranial-caudal joint translation, gait analysis, and synovial fluid levels of 3B3(-) (proteoglycan epitope) and C2C (collagen II neoepitope) up to 12 weeks after surgery. Joint translation and rotation were quantified at necropsy. CrCL midsubstance length was determined before and after elongation and at necropsy. CrCLs were subjectively assessed with light microscopy. Comparisons were made between stifles containing elongated CrCLs with and without IAP and unoperated controls.

Results: Four weeks after surgery, ground reaction forces were significantly decreased in operated limbs. Absolute C2C levels were significantly elevated in operated stifles 4 weeks post-surgery. C2C and 3B3(-) levels normalized to total protein were significantly elevated in IAP+ stifles 8 weeks after surgery. Protected CrCLs appeared to have decreased granulation tissue and better collagen fiber alignment.

Conclusions: IAP has negligible effects on the canine stifle based on the response variables evaluated in this 12-week study. Protection of elongated CrCLs may promote reduced, organized scar formation.

Clinical Relevance: These results support the healing capacity of the canine CrCL midsubstance following elongation injury and IAP application to potentially reduce cicatrix formation in elongated CrCLs.