Abstract
Calcification and fractures of costal cartilages were investigated in beagle dogs of both sexes aged from 3 months to 15 3/4 years. By soft x-ray radiography, calcification and minute fractures of costal cartilages were already observed at 6 months of age regardless of sexes, with a subsequent development with age. Complete fractures were frequently observed in dogs aged more than 11 years. By the analysis of four costal cartilages (1st, 5th, 9th, 12th or 13th), it was demonstrated that after 6 months of age the water content decreased rapidly together with marked increase in the organic matrix, ash, calcium and phosphorus contents. Histological examination of undecalcified specimens revealed that the matrix in the central zones was already calcified and minute fractures therein occurred at 6 months of age. These changes gradually expanded from the central to the peripheral zone with age. At 9 months of age, the calcified cartilage altered to an osseous tissue similar to that of trabecular bones, showing a normal histomorphological dynamics thereafter. It is concluded that the observed sequence of calcification and fracture of costal cartilage is a normal and age-related change which occurs after 6 months of age.
