Communicating cartilage canals of the physis of the distal part of the ulna of growing swine and their potential role in healing of metaphyseal dysplasia of osteochondrosis.

The distal parts of ulnae of 22 pigs ranging in age from 1 day to 6 months were studied histologically. Communicating cartilage canals passing from the epiphyseal vasculature through the physis and anastomosing with the metaphyseal vasculature were identified in neonatal pigs. In older pigs, the communicating cartilage canals had become smaller, as evidence by the presence of only capillaries. Eosinophilic matrical strekas and patches containing scattered elongated nuclei and centrally located accumulations of erythrocytes within the physis became more numerous in groups of old pigs. These streaks were considered to be compressed, nonpathologic extensions of the communicating physeal cartilage canals. In abnormally thick physeal cartilage of dysplastic 3-month-old-pigs, ossification was observed around hypertrophied communicating cartilage canals in the central portion of the lesion. Presumably, with reestablishment of endochondral ossification, the physis could return to its normal thickness and laminar pattern.