Hip dislocation

Background

Trauma is primary mechanism. In adults, requires substantial force vectors (MVC, fall from a height)

Because of force required, 50% will have other fractures or significant injuries

Epidemiology

90% posterior (10% central or anterior)

Posterior = force applied to flexed knee and hip (e.g. dashboard)

Anterior = direct blow to posterior hip or posterior force to abducted leg

Central = direct impact to lateral aspect.

Mortality primarily due to associated injuries

Head, thorax & pelvis

Diagnosis

Shortened, adducted & internally rotated. Hip and knee in slight flexion

NB: not true if there is associated femoral fx

Look for:

1. Loss of sensat posterior leg/foot (sciatic nerve)
2. Loss of dorsiflexion (peroneal branch) or plantar flexion (tibial branch)
3. LE pale / cool to touch (femoral art)

Workup

Usually obvious, but can be subtle on single AP view

Typically femoral head is seen lateral and superior to acetabulum

CT very accurate, and helps especially in delineating acetabular injury (where plain films are notoriously poor)

Treatment

Reduction

Multiple techniques described (Allis/Stimson)

All involve longitudinal traction to unlock the femoral head, with gentle internal/external rotation to seat it in the acetabulum

ED success rate for native hip dislocation/reduction unclear

(10% reported, but not a pure series)

Prognosis

1. Other injuries/life threats
2. Avascular necrosis (AVN)
   1. Occurs in 10-20% of cases
   2. Time-dependant phenomenon
   3. 6-hours is the cut-off
3. Sciatic Nerve injury: 10-15%
   1. Usually neuropraxia with eventual recovery expected
   2. Incidence of this 2.5X with delay > 6 hours for reduction
   3. Osteoarthritis: 10%-35% 30-70% after open-reduction

Source

ACEP ('09)