Paediatric Hip and Pelvic Trauma

Abstract

Fractures of the proximal femur and pelvis are rare in children but are associated with a high incidence of clinically significant complications which may present only after many years. These injuries are the result of high energy, blunt trauma although apophyseal avulsions are low energy sporting injuries.

Pelvic injuries are classified according to Torode and Zeig (Holden et al. J Am Acad Orthop Surg 15:172–7, 2007) although the ideal classification for paediatric injuries does not exist. The classification of proximal femoral fractures according to Delbet and cited by Colonna is prognostic by predicting the risk of avascular necrosis (AVN).

The anatomical differences of the developing hip and pelvis account for the different patterns of injury and unique complications seen in children. The pelvis is more malleable and greater energy is required to result in fracture than in the adult. The presence of the physis and large proportion of cartilage in the proximal femur renders it susceptible to growth arrest. Damage to the tri-radiate cartilage can lead to acetabular dysplasia. Until physeal closure, reliance of the proximal femoral epiphysis on end-arteries makes it susceptible to ischaemia with resultant AVN following injury.

Life-threatening haemorrhage is less common in children and mortality results from associated injuries sustained at the time of high energy trauma. After stabilisation of the patient as per trauma guidelines, injuries must be accurately assessed.

Plain radiography will reveal gross injuries although additional views, CT and MRI, may be required to detect more subtle changes, especially where fracture lines pass through unossified bone.

Fracture–dislocations of the proximal femur, displaced fractures or those with the potential to displace require operative management. Pelvic fractures were historically treated non-operatively due to perceived low morbidity and high remodelling potential in the younger patient. However, remodelling may be incomplete and a poor outcome relates to residual pelvic asymmetry. The treatment of pelvic injuries has therefore become more aggressive with a greater number of patients managed operatively. The indications for operative treatment of acetabular fractures are similar to those for adult patients.

The principles of management of hip fractures are anatomical reduction and stable fixation combined with capsular decompression. Closed reduction may be attempted but must not be accepted if imperfect. Open reduction is recommended via an anterior or anterolateral approach.

Internal fixation must be stable and more proximal fractures require threaded transphyseal devices at the expense of a potential growth arrest. However, smooth pins may suffice in the very young. Larger patients and more distal fractures may require a pin and side-plate system. Capsular decompression reduces the risk of AVN and is performed by open capsulotomy or large-bore needle aspiration.

Management of pelvic fractures is tailored to the age of the patient, the pattern and stability of the fracture. Fracture reduction can be achieved via closed manipulation, skeletal traction or open methods. Fixation methods are various and may involve combined internal and external fixation. Selective arterial embolisation may also be required to restore haemodynamic stability.

Post-operative care depends on the individual injury pattern, the quality of reduction, the stability of fixation and patient cooperation. Although AVN is usually detectable within 1 year of injury, patients must be followed up until skeletal maturity as the effects of growth disturbance and joint degeneration may only become apparent after many years.

Complications of proximal femoral fractures include AVN, coxa vara, growth arrest and leg-length discrepancy. The risk of AVN correlates with more proximal fractures, wide displacement and older patients in whom there is lower potential for re-vascularization and remodeling. A satisfactory outcome is difficult to achieve once AVN is established.

Pelvic injuries are associated with chronic pain, nerve injuries, urological problems, heterotopic ossification and pycho-social issues. Damage to the tri-radiate cartilage may cause acetabular dysplasia, incongruence and secondary joint degeneration.

Paediatric hip and pelvic fractures are challenging injuries that require a thorough understanding of the developing hip and pelvis to maximise future function.