Postnatal morphogenesis of the anconeal process of the ulna of swine.

The proximal ulnae of 79 swine ranging in age from 1 day to 2 years were radiographed and those of 46 of the swine were studied histologically. The anconeal process was a hyaline cartilaginous model at birth but ossified by 6 months of age. Endochondral ossification began at the base of the anconeal process and progressed in a pyramidal manner toward its apex. Secondary center of ossification was not observed in porcine anconeal processes examined. A lesion in the anconeal process of a 2-year-old animal was interpreted as a fracture of the anconeal process, and not a fracture of an anconeal physis. Implications of the development of the anconeal process as related to osteochondrosis in swine were discussed.