Acetabulum Fractures: Anatomy, Classification, and Management

Anatomy

1. Anterior (iliopubic) column - anterior half of the iliac crest + iliac spines + anterior half of the acetabulum + pubis
2. Posterior (ilioischial) column - ischium + ischial spine + rear half of acetabulum + dense bone of sciatic notches
3. Anterior wall
4. Posterior wall (larger, more prone to isolated fracture due to flexed hip position during injury)
5. Acetabular dome/roof - the weight-bearing articular surface; anatomic restoration here is the primary goal of treatment
6. Medial wall (quadrilateral plate) - the flat bone forming the lateral border of the true pelvis

• Campbell's Operative Orthopaedics, 15th Ed 2026
• Rockwood and Green's Fractures in Adults, 10th Ed 2025

Mechanisms of Injury

• Position of the hip at time of impact
• Direction and magnitude of applied force

• High-energy mechanisms (MVCs) produce most fractures in younger patients, often with polytrauma
• Low-energy mechanisms (fall on greater trochanter) in elderly patients with osteopenic bone produce severely comminuted fractures with articular impaction

Clinical Presentation

• Dashboard injury pattern: posterior dislocation + knee/tibia injuries + possible aortic transection
• Central displacement pattern: ipsilateral chest wall + visceral organ injuries

• Pain, inability to bear weight, shortened/rotated limb
• Neurovascular exam - sciatic nerve injury is common, particularly in fractures with posterior displacement (seen in ~20% of posterior wall/column fractures)
• Morel-Lavallee lesion: closed degloving injury around the hip from shearing of skin from fascia; look for skin hypermobility or fluid wave. Increases wound and infection complications. Small lesions (<50 mL) can be aspirated; larger ones require formal debridement and may mandate delayed fracture fixation.

Imaging

Plain Radiographs - Standard Views

1. AP pelvis - assess all six Letournel radiographic landmarks
2. Iliac oblique (Judet view) - beam perpendicular to iliac wing; shows posterior column and anterior wall
3. Obturator oblique (Judet view) - beam perpendicular to obturator foramen; shows anterior column and posterior wall

Six Letournel Radiographic Landmarks

1. Iliopubic (iliopectineal) line - medial cortex of anterior column; disrupted in anterior column fractures
2. Ilioischial line - medial cortex of posterior column; disrupted in posterior column fractures
3. "Teardrop" (radiographic U) - inferior/anterior acetabular fossa + anterior quadrilateral plate
4. Sourcil (roof arc) - acetabular roof/weight-bearing dome
5. Anterior lip - most lateral aspect of anterior wall
6. Posterior lip - most lateral aspect of posterior wall

CT Scan

• Essential for fracture characterization, identification of comminution, marginal impaction, intra-articular bone fragments, and femoral head impaction injuries
• 3D CT useful for preoperative planning; fracture orientation on 2D CT:
  • Transverse fractures and anterior/posterior wall fractures run sagittally (parallel to quadrilateral plate on axial cuts)
  • Anterior and posterior column fractures run coronally, extending through obturator foramen

Roof Arc Measurements (Matta et al.)

Dynamic Stress Examination

Classification: Letournel and Judet System

Elementary (Simple) Types

Associated (Complex) Types

Management

General Principles

• Management of acetabular fractures is among the most complex in orthopaedic trauma
• Significant learning curve: one study showed a 50% decrease in reoperation rate at 2.4 years into practice
• Goal: anatomic restoration of the dome with concentric reduction of the femoral head

Non-Operative Management

Indications

• Fracture displacement <2 mm through the weight-bearing dome
• All three roof arcs >45°
• Both-column fracture with secondary congruence (all articular fragments remodel around the femoral head) - monitored closely, especially when THA is a reasonable backup
• Elderly patients with nondisplaced/minimally displaced fractures (<2 mm step-off on obturator oblique)
• Non-displaced fractures in any age group: only 7% will displace significantly; 94% retain native hip at 10 years

Protocol

• Mobilization with toe-touch/partial weight bearing (<10 kg) for younger patients; weight bearing as tolerated with walker in elderly
• Bed rest avoided (increases deconditioning, decubiti, pulmonary complications)
• Serial AP + oblique radiographs weekly for first 4 weeks
• Full weight bearing at 6-12 weeks when healing is adequate
• VTE prophylaxis: SCDs + Lovenox 40 mg nightly (perioperative); discharge on Eliquis 2.5 mg PO BID x 4 weeks

Operative Management

Indications

• 2 mm displacement of the weight-bearing dome

• Hip joint instability (dynamic stress test positive)
• Roof arc <45° in any projection
• Intra-articular bone fragments blocking reduction
• Irreducible hip dislocation
• Open fracture
• Morel-Lavallee lesion (may require staged approach)

Timing

• Ideal: surgery within 2-5 days of injury after resuscitation and planning
• Hip dislocation requires urgent closed reduction (within 6 hours) to reduce risk of avascular necrosis of the femoral head

Surgical Approaches

1. Kocher-Langenbeck (K-L) approach
   • Most commonly used for posterior wall and posterior column fractures
   • Patient prone or lateral decubitus
   • Extensile modification possible (trochanteric flip osteotomy)
   • Risk: superior gluteal neurovascular injury, sciatic nerve injury
2. Gibson approach - variant of posterior exposure

1. Ilioinguinal approach (Letournel)
   • Standard anterior approach
   • Three "windows": lateral (iliac fossa to SI joint), middle (pelvic brim to pectineal eminence + quadrilateral surface), medial (space of Retzius + symphysis)
   • Patient supine, incision from posterior to gluteus medius tubercle, along iliac crest to ASIS then to midline 2 fingerbreadths above pubic symphysis
   • Access to anterior column, anterior wall, both-column fractures
   • Risk: injury to lateral femoral cutaneous nerve, femoral nerve, external iliac vessels, spermatic cord/round ligament
2. Anterior Intrapelvic (AIP) / Modified Stoppa approach
   • Supine approach working through space of Retzius
   • Good access to quadrilateral plate and medial wall
   • Increasingly used for anterior column and anterior + posterior hemitransverse fractures

1. Extended iliofemoral approach
   • For very complex fractures (T-type, both-column) when other approaches fail
   • High wound complication and heterotopic ossification rates; less commonly used
   • Associated with 3-5% risk of superior gluteal nerve injury
2. Simultaneous anterior + posterior approaches (repositioning required)

Surgical Positioning

• Prone (flat radiolucent table with chest rolls): posterior approaches - allows knee flexion for sciatic nerve protection
• Supine: anterior approaches
• Distal femoral or proximal tibial traction pin routinely used (start at 10% body weight, up to 20-25 lb max)
• Intraoperative fluoroscopy (three standard views) mandatory; newer 3D intraoperative imaging emerging

Management in the Elderly

• Prevalence of acetabular fractures in patients >60 years increased 2.4-fold between 1980 and 2007
• Predominant fracture pattern: anterior column, anterior column + posterior hemitransverse, both-column
• Key complicating factors: osteoporosis, comminution, dome impaction ("gull sign"), quadrilateral plate involvement

1. Non-operative (if indications met, as above)
2. ORIF - 15-31% of patients >55 years require conversion to THA at 2.5-5 years. 85% still have WOMAC/SF-8 scores consistent with a normal hip
3. Acute THA - gaining acceptance for elderly patients with:
   • Fractures meeting operative criteria but with severe comminution not amenable to ORIF
   • Pre-existing hip osteoarthritis
   • "Dome impaction" / "gull sign" (poor prognostic factor)
4. ORIF + acute THA (combined procedure) - increasingly performed in selected elderly patients
5. Percutaneous fixation - limited role; generally for minimally displaced fractures in poor surgical candidates

Complications

Outcomes and Prognosis

• Anatomic reduction of the weight-bearing dome (most important)
• Young patient age
• No marginal impaction
• No femoral head cartilage injury
• Surgeon experience

• Dome impaction / "gull wing" sign
• Marginal impaction
• Femoral head chondral injury
• Comminution of the weight-bearing surface
• Associated femoral head fracture (Pipkin classification)
• Delayed treatment

Key Teaching Points Summary

• Campbell's Operative Orthopaedics, 15th Ed 2026, Chapter 61 (Acetabular Fractures)
• Rockwood and Green's Fractures in Adults, 10th Ed 2025, Chapter 51 (Acetabulum Fractures)
• Sabiston Textbook of Surgery (VTE prophylaxis protocol)