Acetabular Fractures

Epidemiology

• Demographics:
  • Common in young males, similar to pelvic fractures.
• Mechanism:
  • High-speed motor vehicle accidents (MVA) and falls from height.
  • Injury pattern depends on the position of the femoral head at the time of impact.
  • Dashboard injury is the most common.
• Associated Injuries:
  • High-energy mechanism; follow ATLS protocol.
  • Specific injuries include:
    • Ipsilateral knee soft tissue injury.
    • Sciatic nerve injury in posterior wall fractures.

Classification

Letournel Classification

• Reliability:
  • High inter- and intra-observer reliability.
  • Useful for determining the surgical approach.
• Types:
  • Elementary (5 types):
    1. Posterior wall
    2. Posterior column
    3. Anterior wall
    4. Anterior column
    5. Transverse
  • Associated (5 types):
    1. Posterior wall – Posterior column
    2. Anterior column – Posterior hemitransverse
    3. Both column
    4. Transverse – Posterior wall
    5. T-type
• Order of Frequency:
  • Posterior wall > Both column > Transverse & Posterior hemitransverse > Transverse > T-Type
  • Anterior wall, anterior column, and posterior wall & column are uncommon.

Anatomy

• Structure:
  • Formed by the confluence of the pubis, ischium, and ileum.
  • Supported by two columns in an inverted Y-shape:
    • Anterior column:
      • Anterior half of the ileum, including the pelvic brim and anterior half of the acetabular surface.
    • Posterior column:
      • Extends from the greater sciatic notch to the ischial tuberosity and includes the posterior half of the acetabular surface.
  • Quadrilateral Plate: Thin medial wall.
  • Weight-Bearing Dome:
    • Superior one-third of the acetabulum on X-ray.
    • Superior 10 mm on axial CT slices (most critical cartilage).

Imaging

• Plain Radiographs:

  • Views: AP, Iliac oblique, and Obturator oblique.
  • Best Uses:
    • Iliac oblique: Anterior wall and posterior column.
    • Obturator oblique: Posterior wall and anterior column.

• CT Scan:

  • Almost mandatory.
  • Helps visualize fracture morphology and displacement.

Key Radiographic Landmarks

AP View

1. Iliopectineal line.
2. Ilioischial line.
3. Teardrop.
4. Acetabular roof.
5. Anterior rim of the acetabulum.
6. Posterior rim of the acetabulum.

Iliac Oblique

• Best for anterior wall and posterior column fractures.

Obturator Oblique

• Best for posterior wall and anterior column fractures.

Specifics of Fracture Types

Posterior Wall Fractures

• Most common type.
• Often comminuted, with 50% involving marginal impaction.

Posterior Column Fractures

• Uncommon in isolation.
• Fracture extends from the greater sciatic notch to the ischial ramus.
• Grossly unstable; often requires skeletal traction.

Anterior Wall and Column Fractures

• Rare in isolation.
• Usually involves the quadrilateral plate.

Transverse Fractures

• Only elementary type to involve both columns.
• Fracture divides into infratectal, transtectal, or juxtatectal based on its position relative to the articular surface.

T-Type Fractures

• Combination of transverse fracture with vertical split through the ischiopubic ramus.
• Worst prognosis among acetabular fractures.

Both Column Fractures

• Most common associated type (25%).
• No articular surface remains in continuity with the ileum.
• Spur Sign: Pathognomonic on obturator oblique view.

Management Principles

Preferred Surgical Approach

• Posterior wall/column fractures: Kocher-Langenbach.
• Anterior wall/column fractures: Ilioinguinal.
• Both column fractures: Extended iliofemoral, ilioinguinal, or combined approaches.
• Transverse fractures: Approach depends on displacement and fracture level.

Non-Surgical Treatment

• Criteria for Non-Operative Management:
  • Stable with articular congruity.
  • Secondary congruency in some both-column fractures.
  • Roof arc angle > 45° on all views.
  • No fracture lines within the superior 10 mm of axial CT cuts.
• Roof Arc Angle:
  • Formed by a vertical line through the femoral head and a line to the articular fracture.

  • 45° indicates fracture outside the weight-bearing dome.

Surgical Treatment

• Indications:
  • Hip instability or loss of joint congruence.
  • Articular displacement > 2 mm.
  • Incarcerated intra-articular fragments.
  • Roof arc angle < 45°.
• Goals:
  • Restore articular congruity and hip stability.

Primary Hip Arthroplasty

• Indicated for unreconstructable articular comminution or elderly osteoporotic bone.

Complications

• Avascular Necrosis (AVN): Especially with posterior dislocation; reduce ASAP.
• Post-Traumatic Arthrosis.
• Neurologic Injury: From fracture or iatrogenic causes.
• Thromboembolism:
  • DVT: 20–50%.
  • Fatal PE: 2%.
• Heterotopic Ossification.

Best Surgical Outcomes

• Good bone quality.
• Early surgery.
• Minimal comminution and marginal impaction.
• Accurate joint reduction.