Epidemiology
- Rare injury, posterior direction in most
- Under about 5 years low energy falls can dislocate the hip due to ligamentous laxity
- Older children need higher energy, often with associated fractures
Clinical Features
- Posterior dislocation holds the limb flexed, adducted and internally rotated
- Check sciatic nerve function before reduction
Investigations
- AP pelvis and lateral hip before reduction
- Look for proximal femoral physeal separation before any manoeuvre
Management
- Reduce urgently under GA with full relaxation, ideally within 6 hours
- Gentle reduction under fluoroscopy to avoid displacing the capital femoral epiphysis
- Check stability after reduction
- CT or MRI after reduction to confirm concentric reduction
- MRI shows cartilaginous fragments and labral entrapment better than CT
- Open reduction if irreducible, debris in joint or incongruent reduction
- Joint space widening over 2 mm compared with the other side suggests interposed tissue
- Open fixation of displaced acetabular fractures over 2 mm
- Spica cast in young children or protected weightbearing in older children for about 4 to 6 weeks
Complications
- Avascular necrosis, more likely with delayed reduction and older age
- Coxa magna
- Sciatic nerve palsy
- Recurrent dislocation, consider ligamentous laxity syndromes such as Down syndrome
- Transphyseal separation during reduction
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.