Changes in young rat radius following excision of the perichondrial ring.

The distal growth plate of the radius was exposed in young rats and the perichondrial ring and fibrous covers were removed at the exposed surface. In addition, a small portion of either the adjacent epiphysis or of the adjacent metaphysis was removed also. In the following days, important alterations in bone structure were observed at the level of the removed perichondrial ring. The most relevant changes were an enlargement of the growth plate at the exposed surface that grew in an abnormal direction, proliferation of bone trabeculae at the level of the excised perichondrial ring, and bending of the bone. No regeneration of the perichondrial ring occurred. These changes support both the role of the perichondrial ring in the mechanical constraint of the growth plate, and the induction of bone formation by the hypertrophic cartilage at the level of the absent perichondrial ring.