Pediatric Hip Injuries
These are very uncommon in children occurring less than 1 percent as often as is seen in adults. The femur begins to ossify in utero and completes itself at the age of 4 years. The proximal epiphyseal plate fuses by 18 years of age. Some fractures of the proximal femur can cause a lack of circulation to the head of the femur.
A hip fracture in kids is usually the result of a severe and direct trauma such as is seen in a motor vehicle accident. This is the case in up to 80 percent of cases with the remainder occurring from fractures through bone cysts of the femur. Stress fractures can happen but are very unusual.
When the hip is fractured, the leg looks shorter than the other side and is externally rotated. The range of motion of the hip is limited and the doctor may feel crepitus in the area. There can be bruising or tenderness over the hip area. During the evaluation, a careful neurovascular examination should be undertaken.
X-rays of the front and sides of the hip can show the fracture. Comparison to the opposite hip is a good idea in some cases. CT scan can show undisplaced fractures. A radioisotope scan done 48 hours after the injury can also show occult fractures. MRI scans within 24 hours of injury can also show the presence of an occult fracture.
Treatment of a pediatric hip fracture can involve closed reduction with fixation using pins. If the fracture cannot be reduced externally, then surgery is necessary. An abduction spica cast can be used or pinning can be attempted. Without these treatments, nonunion can happen. Displaced fractures require traction in order to lengthen the fractured extremity. If the fracture is unstable, then open reduction and internal fixation may be necessary.
Complications include osteonecrosis, which can happen in up to 40 percent of hip fractures in kids. Nonunion can always happen and the epiphyseal plate may prematurely close, contributing to leg length discrepancy.
Traumatic Hip Dislocations
These occur between the ages of 2 and 5 and in those between 11 and 15. In the latter case, the dislocation is related to participation in sports. Some hip dislocations can happen because of motor vehicle accidents. Posterior dislocations happen at a rate ten times that of anterior dislocations. In younger kids, a dislocation can happen because of a fall from a standing height, while older kids dislocate their hip because of a motor vehicle accident or sports accident.
The child with a posterior hip dislocation usually has the hip flexed, adducted, and internally rotated. Anterior hip dislocations look different, with the hip in extension, with abduction and external rotation of the hip. The function of the sciatic nerve needs to be evaluated as this can be damaged in a dislocation. In anterior dislocations, the femoral nerve can be damaged. Before manipulating the hip, it should be evaluated for fractures of the femur, which are common in this type of injury.
X-ray of the front and side of the hip can show the dislocation. The x-ray should include the entire femur because of a risk of fracture to this bone. X-rays should be repeated after relocating the hip because small fractures are more easily visible when the bone is in proper alignment. CT scanning can be done after hip relocation to see if there is any femoral head or acetabular fracture.
Treatment includes closed reduction under conscious sedation as long as the reduction is done within 12 hours of injury. If the hip dislocation has been neglected, traction may be used to lengthen the leg. Reduction using this method can take 3-6 days. Traction should be continued for a total of 2-3 weeks.
Surgery may be necessary if the dislocation is more than 12 hours old. If the sciatic nerve is involved, open surgery is necessary to explore the damage to the nerve. If there is a fracture and a dislocation, the dislocation should be treated first under general anesthesia, followed by open or closed reduction of the fractured femur. After surgery, traction is necessary for up to 4-6 weeks or a hip spica cast needs to be applied.
Complications include an 8-10 percent incidence of osteonecrosis, epiphyseal plate separation, recurrent dislocation, degenerative joint disease, and nerve injury, primarily to the sciatic nerve.