Condylar cartilage in the muscular dystrophic mouse

The adaptability of condylar cartilage has been demonstrated previously after experimentally created functional alteration. This study was undertaken to examine the morphology of condylar cartilage in animals affected with a progressive muscular disease. Muscular dystrophic male mice (genotype: dy/dy, dy/+ x dy/+, Jackson Laboratory, Maine) and corresponding unaffected control mice were decapitated at ages 3, 6, 9, and 12 weeks, and their heads processed for histology. The cellular morphology of the condylar cartilage in the youngest age group was similar in dystrophic and control mice: the cartilage was a hypertrophic type. At ages 6 and 9 weeks, the maturational progression toward the nonhypertrophic form was observed in the dystrophic and control groups, the latter having flatter condylar heads. Differences were still evident at age 12 weeks. These observations were supported by measurements of the ratios of the mean cartilage thickness to condylar width (c/w), mean condylar height to width (h/w), and mean cartilage thickness to condylar height (c/h). This study supports the hypothesis that the adaptive nature of condylar cartilage may be regulated by the force levels to which the condyle is subjected.