Acetabular Fracture

Acetabular fractures result from force transmitted through the femoral head into the pelvis.

They are typically seen after high energy trauma (motor vehicle collisions, falls from height) in younger patients, and, in a growing group, as low energy fragility fractures in elderly patients (anterior column with quadrilateral plate displacement).

Associated injuries are common: hip dislocation (especially with posterior wall fractures), femoral head or neck fractures, pelvic ring fractures, sciatic nerve injury, knee and femoral shaft injuries, and thoracic and abdominal trauma.

The acetabulum is conceptualised as two columns forming an inverted Y: the anterior column (iliac crest to pubic symphysis, including the anterior wall) and the posterior column (greater sciatic notch to ischial tuberosity, including the posterior wall and the ischial spine), with the quadrilateral surface medially and the roof (dome) as the weight bearing portion.

Judet and Letournel classification:

• Elementary (simple) patterns: posterior wall, posterior column, anterior wall, anterior column, transverse

• Associated patterns: posterior column plus posterior wall, transverse plus posterior wall, T-shaped, anterior column or wall plus posterior hemitransverse, associated both column (all articular segments detached from the intact ilium, with the "spur sign" on the obturator oblique view)

Posterior wall fractures are the commonest single pattern (about 25 to 30%). Both column fractures are about 20 to 25%.

Presentation is pain in the groin, hip or buttock, inability to bear weight, and a limb that may be shortened and rotated (posterior dislocation: flexed, adducted, internally rotated; central dislocation: shortening without a classic position).

High energy cases show associated injuries, so conduct a full trauma assessment. Look for:

• Neurovascular status: sciatic nerve (foot drop, sensory loss) in posterior dislocations or posterior wall and column fractures, with injury in 10 to 20%; superior gluteal vessel injury and retroperitoneal haemorrhage in pelvic ring disruption

• Morel-Lavallée lesion (closed degloving over the greater trochanter), which increases infection risk for later surgery

• Skin condition, ipsilateral knee injury ("dashboard" injury with patellar fracture or posterior cruciate ligament injury), and femoral head damage

• Haemodynamic instability, which implies associated pelvic ring or vascular injury

• Radiographs: AP pelvis, and Judet views (iliac oblique and obturator oblique at 45 degrees). Six radiographic landmarks on the AP pelvis: iliopectineal line (anterior column), ilioischial line (posterior column), roof, teardrop, anterior wall rim and posterior wall rim. Disruption of each landmark identifies the involved column or wall.
• CT with 2D reformats and 3D reconstruction is mandatory for planning, and assesses: marginal impaction, intra articular fragments, femoral head injury, roof arc angles (medial 45 degrees, anterior 45 degrees, posterior 45 degrees roof arc measurements, with roof arc under 45 degrees on all views suggesting that the fracture affects the weight bearing dome), the posterior wall fragment size (above 50% of the posterior wall on CT suggests instability, and under 20% stability, with 20 to 50% intermediate), and incarcerated fragments. CT angiography if vascular injury is suspected.
• Examination under anaesthesia and stress fluoroscopy may determine posterior wall stability in the intermediate group.

Initial care. Resuscitate according to trauma protocols. Reduce a dislocated hip urgently, within 6 hours to reduce the risk of avascular necrosis, with closed reduction under sedation or general anaesthetic; if irreducible or if there is an incarcerated fragment, open reduction. After reduction, repeat neurovascular examination and CT.

Apply skeletal traction (distal femoral pin, 10 to 15% of body weight, up to 15 to 20 lb) to maintain reduction and unload the joint while awaiting definitive surgery. Thromboprophylaxis: enoxaparin 40 mg subcutaneously once daily (or 30 mg twice daily in high risk trauma), starting within 24 hours once bleeding is controlled, continued for at least 4 to 6 weeks (some use up to 35 days), with mechanical prophylaxis until then. Analgesia, including regional blocks.

Non-operative treatment. Indicated for:

• displacement under 2 mm
• minimally displaced fractures
• secondary congruence in both column fractures (the femoral head remains congruent with the displaced fragments on all three views)
• low posterior wall fractures (under 20% of the wall) that are stable
• fractures not involving the weight bearing dome (roof arc angle above 45 degrees on all views)
• patients unfit for surgery

Protocol: protected weight bearing (toe touch, about 10 to 15 kg) for 6 to 12 weeks, serial radiographs, early mobilisation of hip and knee.

Operative treatment. Indicated for displacement above 2 to 3 mm in the weight bearing dome, femoral head subluxation or instability, intra articular fragments, incarcerated fragments after reduction, and posterior wall fractures over 50%. Ideal timing is within 5 to 10 days, once the patient is stable, since surgery after 3 weeks becomes harder because of callus. Approach choice depends on pattern:

• Kocher-Langenbeck (posterior) for posterior wall and posterior column, transverse with posterior wall
• Ilioinguinal or modified Stoppa (anterior intrapelvic) for anterior wall, anterior column, anterior column plus posterior hemitransverse, and many both column fractures
• Extended iliofemoral, combined or sequential approaches for complex both column and T-type fractures
• Percutaneous screw fixation for selected minimally displaced fractures

Fixation uses pelvic reconstruction plates and lag screws, spring plates for posterior wall fragments, and primary hip arthroplasty (combined hip procedure: ORIF plus total hip replacement) in older patients with osteoporotic bone, significant femoral head or roof impaction, or neck fractures. Acute total hip arthroplasty with cage or acetabular reconstruction in the elderly reduces re-operation rates compared with fixation alone.

Postoperative care. Protected weight bearing (toe touch to partial) for 8 to 12 weeks; early passive and active range of motion; gradual progression to full weight bearing; hip precautions after arthroplasty. Heterotopic ossification prophylaxis for extensile or posterior approaches: indomethacin 25 mg three times daily for 6 weeks, or single dose radiotherapy (700 cGy) within 72 hours. Antibiotics: cefazolin 2 g IV (3 g if over 120 kg) within 60 minutes of incision and for 24 hours after.

Complications.

• Post-traumatic osteoarthritis (about 20 to 30% with anatomic reduction, more with imperfect reduction; the quality of articular reduction is the strongest predictor)
• avascular necrosis of the femoral head (about 5 to 18%, higher with dislocation)
• sciatic nerve palsy (iatrogenic or injury related)
• heterotopic ossification (up to 25 to 60% in extensile approaches without prophylaxis)
• venous thromboembolism
• surgical site infection (about 5%)
• femoral nerve and lateral femoral cutaneous nerve injury with anterior approaches
• malunion
• chondrolysis

Conversion to total hip arthroplasty occurs in about 10 to 20% at 10 years.

Prognosis. Roughly 70% have a good or excellent outcome with anatomic reduction. Age, comminution, marginal impaction, femoral head damage, and delayed reduction predict poor results.