Acetabular fracture

Acetabular fractures are a type of pelvic fracture, which may also involve the ilium, ischium or pubis depending on fracture configuration.

Epidemiology

Acetabular fractures are uncommon. The reported incidence is approximately 3 per 100,000 per year. This study reported a 63% to 37% male to female ratio ¹.

Pathology

Mechanism

• high-energy trauma: axial loading of the femur
  • fall from height
  • motor vehicle collision
  • crush injury
• low-energy trauma with abnormal bone: insufficiency fracture

Classification

The Judet and Letournel system for acetabular fractures is the most widely used classification system in clinical practice. It classifies fracture based on oblique pelvic view on plain radiographs.

Additional classification systems include:

• Orthopedic Trauma Association classification (primarily for research) ³ 
• Harris system (CT imaging based) ^4,5

Radiographic features

Plain radiograph

The initial assessment is often with a portable AP radiograph of the pelvis in the emergency department.

Assess the following lines:

1. anterior acetabular wall
2. posterior acetabular wall
3. acetabular roof
4. iliopectineal line: disrupted in fractures involving the anterior column
5. ilioischial line: disrupted in fractures involving the posterior column
6. radiographic U (teardrop)

After diagnosis, oblique pelvic views (Judet views) may be used for follow up. These include:

1. iliac oblique view for the posterior pelvic column and anterior acetabular wall
2. obturator oblique view for the anterior pelvic column and posterior acetabular wall

CT

CT has revolutionised the diagnosis, enabling precise delineation of the fracture configuration and assessment of any articular surface disruption.

Many patients with high-energy trauma will have a whole body CT, allowing initial assessment of the femoroacetabular joint as well as any other injuries that are likely to be present, given the typically high energy mechanism of injury ².

For those patients with pelvic insufficiency fractures involving the acetabulum, a standard CT with a bony algorithm may be useful, especially if operative management is under consideration.

A repeat CT after traction is sometimes used to assess response to treatment.

Treatment and prognosis

Treatment

Treatment is dependent on several factors taking into account both patient factors and fracture characteristics. Treatment, whether operative or non-operative will typically be followed by a period of non-weight bearing on the affected side (or both). Close radiographic follow-up is required. 

Initial treatment will include analgesia and venous thromboembolism prophylaxis.

Traction (either skin or skeletal traction) is usually a temporary solution when surgery is required. Skeletal traction may not be required if the fracture pattern is stable and the fracture is outside the weight bearing zone. 

Non-operative management ⁶ may be indicated in the setting of minimally displaced fracture. It is more common in developing countries. Indications for non-operative management include:

• patient factors
  • delayed presentation (> 3 weeks)
  • high operative risk
• fracture characteristics
  • minimally displaced fracture <2 mm
  • posterior wall fractures involving <20° 
  • out of traction congruency between femoral head and weight bearing roof
  • displaced fracture with roof arcs > 45° in AP and Judet views or >10 mm on axial CT cuts

Operative treatment may consist of open reduction and internal fixation (ORIF) ⁷ or total hip arthroplasty. 

Indications for ORIF: 

• articular incongruence/displaced fracture (>2 mm)
• significantly distorted acetabular roof arc
• entrapped intra-articular fragment/loose bodies
• irreducible fracture-dislocation
• unstable fracture pattern (e.g. posterior wall fracture >45-50%)

Indications for arthroplasty:

• elderly patients with significant osteopenia/comminution or pre-existing arthritis
• post-traumatic arthritis in any age group

Complications

• deep vein thrombosis
• post-traumatic osteoarthritis
• heterotopic ossification ⁸
• hip dislocation

Related articles

• acetabulum
• femoroacetabular joint
• pelvic fracture
• oblique pelvic views