If the triradiate cartilage is open in your trauma patient, you are dealing with a pediatric pelvis. Compared to adults, the pediatric pelvic fracture patterns are different; internal fixation is rarely necessary, but the associated injuries are the major cause of morbidity and mortality. In the adult literature, the pelvis is often compared to the ring of a pretzel. A break in the ring in one location generally indicates a break in a second location (either through the ligaments, or through another part of the bony ring). In children, think of the pelvis as a soft Philadelphia-style pretzel. The ring can indent, or it can break in one place or in two or more places. The abdominal and pelvic contents are not as well protected in kids as in adults. The ligaments tend to be stronger than bone, so CT scans (to define ligamentous disruption) play a smaller role than in adults. Look for iliac wing fractures rather than sacroiliac joint disruption, and pubic rami fractures rather than pubic symphysis disruption. Most importantly, work with your trauma surgeon to rule out abdominal, urologic, chest, and head injuries (Fig. 9-1). For this reason, almost all children with a pelvic fracture are evaluated with an MRI.

Although most children with a pelvic fracture do well, leg length discrepancy, nerve palsies, heterotopic ossification, and triradiate cartilage growth arrests have been the most frequently reported problems. Sacral nerve root injuries have been reported after pediatric sacral fractures. There are also isolated reports of common sciatic nerve injury after pediatric pelvic fractures. A careful neurologic examination at presentation is essential. Heterotopic ossification occurs occasionally, but is rarely disabling. Therefore, counsel parents about the risk of persistent hip stiffness after a severe hip or pelvic fracture. Displaced acetabular fractures through the triradiate cartilage are rare injuries. Like any growth plate fracture, early anatomic alignment is recommended. Families should be counseled at the time of injury about triradiate cartilage growth arrest and the possibility of later acetabular dysplasia.

In summary, most children with a pelvic fracture recover well from their bone injuries. Their hospital course and rehabilitation is often dominated by associated injuries. On occasion, a child may have an adult-type injury or may present with hemodynamic instability. In these rare cases, adult principles of external fixation, possibly augmented by internal fixation, should be utilized to close and stabilize the pelvic ring.

Follow pelvic fractures for a year after injury to ensure there is no triradiate cartilage growth arrest, leg length inequality, heterotopic ossification, or other potential long-term problem.

Pediatric femoral neck fractures cause a lot of trouble. On your first encounter with the parents, you should counsel extensively about the long list of risks that have been so well described. These injuries often occur in children who fall from heights or are struck by vehicles. Search for other injuries before focusing on the femoral neck. Results reported since the advent of intraoperative fluoroscopic imaging and stable internal fixation are far superior to the old, classic series of reports of pinning (good for elbows, not for hips). Early anatomic reduction, stable internal fixation with screws, and 4 to 6 weeks in a spica cast (for the young child where the physis is not crossed by the screws) is the best way to stay out of trouble. Early capsular decompression may reduce the risk of femoral head necrosis, and there is little morbidity from adding this to the treatment plan. In teenagers, you can use the same principles as in adults and cross the growth plate with stable fixation (just as you would fix a slipped capital femoral epiphysis [SCFE]). This allows them to be partial weight bearing without cast immobilization.

Avascular necrosis (AVN) is the primary cause of poor results after a pediatric femoral neck fracture (Fig. 9-2). The risk of AVN is related to fracture type: the closer the fracture to the proximal femoral epiphysis, the more likely it will result in AVN. There is not yet convincing evidence to support the notion that AVN can be consistently prevented after a pediatric femoral neck fracture. However, prompt anatomic reduction and internal fixation, perhaps with capsulotomy or aspiration of the fracture hematoma, is the best the orthopaedic surgeon can offer the child with a femoral neck fracture. AVN may take 12 months or more to manifest itself. Good quality AP and frog-lateral radiographs up to 2 years after injury are recommended. An MRI may also delineate the AVN, although artifact from the screws can make its interpretation difficult as well.

Coxa vara has been reported in up to 30% of pediatric femoral neck series published over the last century (Fig. 9-3). Many believe that modern imaging and fixation have markedly reduced this complication. Probably the most important cause of coxa vara is malunion. AVN or damage to the physis in the proximal femur can also cause coxa vara. Many children will tolerate a neck shaft angle down to 120° and still function at a very high level. Especially in younger children, some improvement of the neck shaft angle over time may be noted. If an older child (>8 years old) has a persistent abductor lurch more than 2 years after injury and a neck shaft angle less than 110°, a valgus osteotomy may be helpful.

Premature physeal closure has been reported in up to 28% of pediatric femoral neck fractures (Fig. 9-4). In most cases, AVN is the culprit. Although an
abductor lurch and altered hip mechanics are common, functionally important leg length inequality is rarely seen, except when there is physeal arrest in very young children. In cases of leg length inequality, a contralateral epiphysiodesis can be performed.

The incidence of nonunion in pediatric femoral neck fractures is about 5% to 10% (Fig. 9-5). If there is persistent pain and no evidence of healing by 3 months after injury, a nonunion should be suspected. Operative treatment is recommended, with removal of initial internal fixation, repeat internal fixation and possibly a subtrochanteric valgus osteotomy.

Pediatric traumatic hip dislocations come in two varieties: toddlers/young children who have dislocation with trivial trauma; and older children/teens with hip dislocation, often with significant trauma. In younger children, closed reduction is generally easy, associated injuries are unusual, and AVN is rare. Traumatic hip dislocation in older children presents much more trouble (Fig. 9-6).

In older children, hip dislocations are usually seen in athletic injuries, or in pedestrian or motor vehicle accidents. Staying out of trouble requires recognizing that the injury has occurred (sometimes spontaneous reduction may be unrecognized), being sure the reduction is done early and produces an anatomic reconstitution of the joint, and using an MRI or CT scan, if necessary, to assure that there is no interposed tissue after reduction (Figs. 9-7 and 9-8).

Hip dislocation with spontaneous reduction is seen in football, soccer (Fig. 9-9), track, or any other running and jumping sport. Consider this possibility when presented with a teenage athlete who experienced sudden hip pain during sports and has persistent groin pain or other associated symptoms a few days later. Use a careful physical examination and good quality radiographs to be
certain that the hip is reduced, stable, and not affected by tissue interposed in the joint. If there is persistent pain or any sign of joint space widening, or possible fragments seen on the X-ray in the vicinity of the femoral epiphysis, an MRI is recommended. Sometimes a widened joint space without radiographic density is the only sign of an interposed capsule or labrum.