Hip dislocation

Thompson–Epstein · Pipkin

Posterior, anterior, with wall or head fracture

See it in 3D on the real bones, displace and reduce it, with simulated X-ray and CT — free, in your browser.

A high-energy injury: it takes a lot to push the femoral head out of its deep socket. Most dislocations are posterior, often with a posterior wall or femoral head fracture. It is an emergency: the longer the head stays out, the higher the risk of avascular necrosis.

Posterior hip dislocation, AP pelvis. The left femoral head lies superolateral to an empty acetabulum and the femur is adducted and internally rotated. — Hellerhoff, CC BY-SA 3.0, via Wikimedia Commons.

Mechanism

Posterior: dashboard injury, force along the femur with the hip and knee flexed. Anterior: forced abduction and external rotation.

Clinical findings

ATLS first (associated injuries are the rule).
Posterior: leg short, flexed, adducted and internally rotated. Anterior: abducted and externally rotated.
Sciatic nerve (mainly fibular division: foot dorsiflexion) before and after reduction; examine the knee (patella, PCL).

Imaging

AP pelvis: the femoral heads should look equal in size; Shenton line broken. CT after reduction for loose fragments in the joint, wall and head fractures.

Classification

Thompson–Epstein (posterior): I simple or minor fragment, II large posterior wall, III comminuted wall, IV acetabular floor, V femoral head.
Pipkin (femoral head): I below the fovea, II above the fovea, III with neck fracture, IV with acetabular fracture.
Epstein (anterior): Superior (pubic) or inferior (obturator) type.

Types shown in 3D

Posterior: About 90%. Dashboard injury: force along the femur with the hip flexed and adducted. The leg is short, flexed, adducted and internally rotated. Reduce within 6 hours to protect the head’s blood supply.
Posterior + posterior wall: Thompson–Epstein II–III: the head breaks off the posterior wall of the acetabulum. A large or comminuted wall fragment leaves the hip unstable after reduction: fixation (Kocher–Langenbeck).
Pipkin (femoral head): A shear fragment of the femoral head stays in the acetabulum while the rest dislocates. Pipkin I below the fovea (outside weight bearing), II above it, III with a neck fracture, IV with an acetabular fracture.
Anterior: About 10%: forced abduction and external rotation. The head lies over the obturator foramen (inferior) or the pubis (superior); the leg is abducted and externally rotated. Watch the femoral vessels and nerve.

Treatment

Emergency reduction: Within 6 hours, under sedation or general anaesthesia with relaxation (Allis or Bigelow technique). Never force it: a neck fracture must be excluded first.
After reduction: CT. Stable concentric hip without fragments: mobilise with protected weight bearing. Incarcerated fragments, unstable posterior wall or displaced head fracture: open reduction and fixation (Kocher–Langenbeck or surgical hip dislocation).

Aftercare

Protected weight bearing 4–6 weeks; MRI at about 3 months if pain suggests avascular necrosis.

Complications

Avascular necrosis of the femoral head
Post-traumatic arthritis
Sciatic nerve palsy
Recurrent dislocation (rare)
Heterotopic ossification