The growth plates are composed of cartilage and appear radiographically as radiolucent lines. These are the areas where bone length is added. During active ossification, the cartilage cells proliferate, line up in columns, mature, hypertrophy, calcify, and disintegrate, leaving a straight strip or core of noncellular calcified cartilage matrix on which new bone is deposited by the osteoblasts
...Many physeal plate problems can lead to deformity of the forelimb. The severity of the deviation and the technique used to correct the problem depend on the specific epiphyseal plate injury and the age of the animal when injured. When the cause of deformity is recognized in an immature animal, the plan of treatment will probably be prophylactic, that is, minimizing subsequent deformity as the animal grows to maturity. This may require multiple surgeries as the animal continues to grow. To wait for the animal to grow to maturity without any correction may allow for formation of deviation beyond correction and may allow subluxation or luxation of the elbow or carpus to develop. Successful reconstructive surgery at that point is impossible. Conversely, the older animal, close to growth plate closure or beyond, can be corrected completely when the problem is recognized and toward an end point.
...Most distal ulnar growth plate problems originate as a result of trauma ...Trauma, usually automobile or crush injuries, to the forelimb may result in premature closure. The trauma may be directly to the growth plate in the form of a severe bruise or may result in fracture. Such direct trauma is not always needed, however, to result in closure. Any trauma to the forelimb of an immature dog sufficient to cause radial and ulnar fracture may also result in growth plate closure. Owners of immature dogs with radial and ulnar fracture should be warned of the possibility of distal ulnar growth plate closure.