[Perichondrial changes in the evolutionary course of traumatic lesions of the epiphysis in growth].

The authors conducted an experimental study aimed at defining the response of the perichondrium to traumatic stimuli. Thirty rabbits were used, subdivided into two groups: in the first group, the perichondrium was submitted to indirect trauma (fracture of the growth nucleus); in the other, to direct trauma (decortication of th perichondrium). We observed that the lesions constitute a stimulus for cellular proliferation with successive differentiation depending on various procedures. The mesenchymal cells of the deeper layer of the perichondrium reveal a tendency towards differentiation in a chondroblastic sense; the portion of these cells which face the metaphysis are generally differentiated to constitute typical cytotypes of the periosteum, giving way to membranous ossification phenomena. The more external layer reveals proliferation of its fibrovascular component. This experimental model allowed us to emphasise the proliferative tendency of so-called perichondrial cells (those of the deep layer). Thus, their role in providing the growth cartilage of new chondrocytes was confirmed, contributing to the transverse development of the metaphysis.