Nonepiphyseal ossification and pseudoepiphysis formation.

Direct ossification extending from the metaphysis into the epiphysis preceded and continued to be more mature than formation and expansion of the typical epiphyseal ossification center at the opposite end of each longitudinal bone of the hand and foot. Direct metaphyseal to epiphyseal ossification usually started centrally and expanded hemispherically, replacing both physeal and epiphyseal cartilage simultaneously. When remnants of the "physis" were retained, however, while juxtaposed epiphyseal cartilage was replaced, a pseudoepiphysis formed. Three basic patterns of pseudoepiphysis formation were evident: (a) a central osseous bridge, (b) a peripheral osseous bridge, and (c) multiple bridging. In each condition, the remnant of the "physis" lacked typical cell columns capable of contributing to the postnatal longitudinal growth of the involved bone. Pseudoepiphyses were well formed by 4-5 years and coalesced with the rest of the bone months to years before skeletal maturation was attained at the opposite epiphyseal end.