Paediatric Hip Dislocation
Hip dislocation in children is rare. It is generally a result of significant trauma.
Hip dislocations can be described by the direction of the dislocation. The femoral head can be dislocated posteriorly (most common), anteriorly or very rarely inferiorly.
Hip dislocations can also be described by the presence of associated injuries: Dislocation without fracture (most common) and dislocation with fracture, e.g. acetabular, femoral head or femoral neck fracture.
In older children, they usually result from significant trauma. In younger children (<5 years) hip dislocation can occur after minor trauma.
The patient will be uncomfortable and not want to move the affected leg.
The affected leg will appear shorter than the non-injured side.
With an anterior dislocation, the leg is usually abducted and externally rotated.
With a posterior dislocation, the leg is usually adducted and internally rotated with the hip in a flexed position.
The key to clinical diagnosis is the abnormal position of the limb, which would not occur with a fractured femur.
All fractures should be assessed using the Advanced Trauma Life Support (ATLS) principles to ensure associated and potentially significant injuries are identified.
Anteroposterior (AP) pelvis x-ray should be obtained.
A post-reduction CT can be ordered if there are any concerns for a non-congruent reduction or bone fragments in the joint.
All hip dislocations need prompt reduction. This is ideally performed in the operating theatre, to allow for careful and controlled relocation.
Post reduction of the hip, the limb is immobilized by a hip spica in children less than 6years and older children’s skin traction is prescribed.
Emphasis should be placed on the elevation of the limb (elbow above the heart) for the first 48 hours and active toe mobilization.
Hip spica care as explained to parents or skin traction in older children to be continued at home.
The need for regular follow up is explained to parents, to assess the recovery and pick up potential AVN at the earliest.
Avascular necrosis (AVN) of the femoral head is the most common complication.
This can occur due to disruption of the blood supply to the femoral head as a result of the injury.
The risk is reported between 3-15%.
The risk has been shown to be significant if the hip is not reduced within 6 hours post-injury.
Other complications are less common but include nerve injury (2-10%), femoral head overgrowth (coxa magna), osteoarthritis (those injuries with acetabular fractures), recurrent dislocation and growth arrest.