Rabbits as preclinical animal models of cam morphology: proof of concept.

BACKGROUND: Cam morphology is associated with acetabular cartilage lesions and early-onset osteoarthritis in patients with femoroacetabular impingement syndrome. Here, we propose a novel iterative rabbit model of cam morphology to characterize the pathophysiology of femoroacetabular impingement-related cartilage lesions. METHODS: We described a repeatable method for establishing a New Zealand white rabbit model of cam morphology by interfering with the epiphyseal tubercle and evaluated the histological outcomes of acetabular cartilage lesions. Cam morphology and subchondral bone were evaluated by micro-CT scanning. The expression of anabolic and catabolic biomarkers of acetabular cartilage was investigated via western blotting and immunohistochemical staining. Chondrocyte apoptosis was detected via TUNEL staining. Kinematics of the hip joint in the sagittal plane were evaluated by a passive optical motion capture system. RESULTS: There were remarkable pathological similarities between this model and human diseases. The cam morphology rabbit model exhibited early cartilage degeneration and subsequent phenotypes of hip osteoarthritis, and this pathological process is not affected by surgical trauma. Hip motion in the cam morphology models resembled that in the healthy controls, and had only a slightly lower joint angle at all phases of the half-bounding gait cycle. This model preserved the natural and predictable movement pattern. CONCLUSIONS: This rabbit model of cam morphology replicates the disease phenotype and allows for scientifically sound evaluation of disease mechanisms. It can be employed to study human cam-type femoroacetabular impingement syndrome.