GROWTH PROFILES AND ARTICULAR-CARTILAGE CHARACTERIZATION IN A GOAT MODEL OF LEGG-CALVE-PERTHES DISEASE

Numerous animal species, including the goat, have been evaluated as po tential models for human Legg-Calve-Perthes disease (LCPD). These mode ls disrupt the vasculature of the femoral head, causing it to collapse , and therefore do not mimic all the clinical patterns of the human di sease. Baseline data regarding the weight and femoral length in the gr owing goat are not available. This study characterized the goat's norm al growth for comparison with that of humans. The growth aberrations i n the proximal femur created by surgically ablating the capital physis were described and compared with the aberrations observed in human LC PD cases. Age, weight, and femoral length (test and control) data were obtained for goats approximately 1 to 14 months of age. At 4 months o f age, a craniolateral surgical approach was used to expose the crania l lateral capital physis so that it could be cauterized. Postoperative radiographs were evaluated by graphic analysis to assess the resultan t changes in the morphology of the proximal femur. The articular carti lage of the femoral head and acetabulum was evaluated mechanically, us ing indentation testing, to determine the apparent modulus of elastici ty, and histopathologically regarding its thickness and proteoglycan c ontent. The proximal femurs of goats and humans exhibits similar morph ology and growth patterns. There was a positive correlation between ag e, weight, and femoral length in the goat. The surgical procedure was effective in ablating the capital femoral physis as indicated by short er femoral lengths and fragmented, flattened, and mushroomed femoral h eads. The histopathological data revealed that the articular cartilage was significantly thicker in the operated hip joints at the ventocaud al and cranial acetabula and the dorsal and ventral femoral heads. The test cartilage exhibited significantly less positive staining for pro teoglycans in the dorsocaudal and the cranial acetabula as well as the central femoral head. The apparent modulus of elasticity, of the test cartilage was significantly lower than the control value at the dorso caudal acetabulum. These data show that the surgical procedure produce d morphological changes that mimic those in human LCPD. The increased thickness of the articular cartilage of the LCPD femoral head may acco unt for the articular degeneration observed in older patients with LCP D, as increased cartilage thickness is associated with decreased tissu e quality.