PEDIATRIC FRACTURE PATHOPHYSIOLOGY

The physiology of pediatric fractures is important for guiding treatment, recognizing syndromes that first present with a fracture, and revealing differences in complications. Bone is composed of three parts: the epiphysis, metaphysis, and diaphysis. The effect on the growth rate and direction of bones varies according to the anatomical position of the epiphyses. Differences in secondary ossification cen-ters must be taken into consideration when evaluating traumas at different ages. As skeletal maturity is completed, elasticity decreases in these secondary ossification centers, and it is one of the factors responsible for causing different injuries in different age groups. Metaphysis is the expansion region located at the ends of the diaphysis. During growth, primary spongy bone first forms through endo-chondral ossification, and it is later transformed into mature secondary spongy bone via osteoclastic and osteoblastic activity. Therefore, bone turnover is considerably high in the metaphyseal region. The diaphysis constitutes the shaft of long bones and is composed of bone that develops through remod-eling from the metaphysis. Mature lamellar bone is the main characteristic of the diaphysis. Fracture healing can occur via primary or secondary mechanisms. In primary healing, union occurs at the frac-ture site without callus formation; it is generally seen in fractures under compressive forces following surgical rigid fixation. In secondary healing, an immature, irregular callus tissue forms at the fracture site. During the bone repair process, cells undergo stages of differentiation similar to those in fetal bone development. The potential for spontaneous and complete recovery is higher the younger the child is, the closer the fracture is to the physis, and if there is angular alignment in the joint’s natural plane of motion. The physis can be injured by many different mechanisms. The most common form of injury is fractures involving the physis that occur after direct trauma. Physeal arrest can develop due to many different causes such as infection, tumors, repetitive stress, or radiation damage. Following physeal injuries, growth disturbance, angular deformities, limb shortening, and in some cases, lengthening of the affected extremity may be observed. This impairment can develop even in the absence of direct damage to the physis. After physeal fractures, angular deformity, limb length discrepancy, epiphyseal distortion, or various combinations thereof may occur. The radiographic indicator of physeal growth disturbance is the loss of the normal physeal contour and the disappearance of the distinct radiolucent line between the epiphysis and metaphysis. In the event of physeal arrest, sclerosis is usually observed at the arrest site. If asymmetric growth has occurred, narrowing at the arrest line, angular deformity, epiphyseal distortion, or shortening may be seen.