Anatomy and Physiology of Pediatric Bone CLINICAL PEARLS AND PITFALLS During periods of growth, the regions of the pediatric skeleton undergoing rapid metabolic activity are more susceptible to fracture Fracture remodeling in pediatric patients is robust and allows for more acceptable angulation at the time of casting, and less frequent operative repair than adult fractures Current Evidence Unique elements of the bony architecture in children include a thick and active periosteum, a physis (growth plate), and an epiphysis (secondary ossification center) ( Fig 111.1 ) Structurally, the bones of a child are much more porous and pliable than those of an adult As a result, overall bony strength is less, and the incidence of fractures is greater in children than in adults Moreover, ligaments have greater strength than the physes; thus, a child is more likely to suffer a fracture from an injury that, in a skeletally mature individual, would result in a sprain, ligamentous injury, or dislocation Unlike in adults, remodeling and anatomic fracture union for pediatric fractures is the expectation rather than the exception In general, significant remodeling can be anticipated both in younger children and when the fracture occurs in the metaphysis of growing bones The greatest degree of remodeling is anticipated with bony injuries occurring in the plane of motion of the adjacent joint In contrast, the injuries least likely to correct without intervention include those that occur in the diaphysis of long bones in adolescents, those with bowing greater than 10 degrees, and fractures with rotational malalignment In general, the goal is to obtain as near an anatomic reduction of the fracture fragments as possible in all age groups and not to rely on remodeling to align angulated fractures; however, relative guidelines for acceptable angulation by age are provided Physeal Fractures Salter–Harris type I injuries are frequently diagnosed clinically by point tenderness at the physis and may not be evident radiographically Selective use of radiographs of the contralateral extremity may help with diagnosing physeal injury An important complication of physeal fractures is growth disturbance, which may result in angular deformity, limb length discrepancy, and/or epiphyseal distortion Orthopedic referral is an important component of management and follow up for these injuries FIGURE 111.1 Diagrammatic representation of the femur in late childhood In assessing young children with musculoskeletal trauma, the clinician must be attuned to the possibility of fractures occurring at the physis (growth plate), which may not be readily apparent on plain film These relatively common injuries generally occur through the zone of provisional calcification, a relatively weak area of the germinal growth plate that becomes even more susceptible to injury during periods of growth in adolescence (peak incidence at 11 to 12 years old) Most growth plate injuries occur in the upper limb, particularly in the radius and ulna Several classification systems have been described for physeal fractures The most widely used is that of Salter and Harris, who described five types of growth plate fractures, each having specific prognostic and treatment implications ( Fig 111.2 ) Salter –Harris type I fracture This fracture type is a separation of the metaphysis from the epiphysis through the zone of provisional calcification resulting in a widening of the physeal space Diagnosis may be challenging if displacement is minimal Radiographs may only show associated soft tissue swelling Type I fractures are generally benign, and growth disturbance is uncommon if near-anatomic reduction is achieved Exceptions include type I injuries of the proximal and distal femur and the proximal tibia, which are subject to premature physeal closure and posttraumatic growth arrest In general, when radiographic studies are negative, but physical examination findings are suggestive of a Salter–Harris type I injury (e.g., point tenderness over a growth plate), immobilization and a follow-up examination are essential Imaging showing periosteal reaction along the physis to 10 days after possible Salter– Harris fractures may help diagnose the occult injury FIGURE 111.2 The Salter–Harris classification for physeal fractures The prognosis for growth disturbance worsens from type I through type V Salter –Harris type II fracture Type II fractures are the most common type of pediatric physeal fracture These fractures extend through both the physis and the metaphysis Like the type I injuries, these fractures generally carry a good prognosis and rarely cause functional deformity Salter –Harris type III and IV fractures Type III and IV injuries are growth plate injuries that involve the intra-articular surface In type III fractures, the fracture line typically extends from the epiphysis into the physis, resulting in a separation of the epiphysis and its associated growth plate from the rest of the epiphysis The fracture line in type IV injuries crosses through all three regions of the bone (epiphysis, physis, and metaphysis) Anatomic position must be reestablished to restore normal joint mechanics and prevent growth disturbance Because of these risks, which may result in functional disability, orthopedic consultation should be obtained while the patient is in the ED for all but the most minor type III and IV injuries Salter –Harris type V fracture Type V fractures are the least common physeal fracture, and most commonly occur at the knee and ankle These fractures are a crushing injury of the growth plate as a result of axial compression It is often difficult to diagnose these injuries during the ED presentation, but a high index of ... I through type V Salter –Harris type II fracture Type II fractures are the most common type of pediatric physeal fracture These fractures extend through both the physis and the metaphysis Like