PATHOPHYSIOLOGY

Fractures can have a variety of causes, including (1) a direct force applied to the bone; (2) an underlying pathologic condition, such as rickets, that leads to spontaneous fracturing; (3) abrupt, intense muscle contractions; and (4) an indirect force applied from a distance (e.g., being hit by a flying object). Other causes of fractures include child abuse, metastatic neuroblastoma, Ewing’s sarcoma, osteogenic sarcoma, osteogenesis imperfecta, copper deficiency, osteomyelitis, overuse injuries, and immobilization resulting in osteoporosis.

There are a variety of fractures, which can be categorized using the Salter-Harris classification system (Box 26-1). The most common type seen in children younger than 3 years of age is the greenstick fracture. This type is characterized by an incomplete break of the cortex, which occurs because the bone is softer and more pliable than the bones of older children. Other fractures (and their related sites) include upper epiphyseal and supracondylar fractures, lateral condylar humeral fractures, and medial epicondylar fractures (humerus); proximal radial physis and radial neck fractures, and nursemaid’s elbow (elbow); fractures of the shaft of the radius and ulna (forearm); and fractures of the femoral shaft and tibia (lower limb). Abuse should be considered in all children younger than 15 months of age with humeral fractures, including supracondylar and spiral fractures. In one study of 215 children, 60% of femur fractures in children younger than 1 year of age were due to abuse. Child abuse can also be suspected with rib and skull fractures.

Box 26-1 Salter-Harris Classification