Summary

Acetabular fractures are intra-articular fractures of the hip socket. Unlike pelvic ring fractures (which bleed), acetabular fractures destroy the cartilage surface, leading to rapid Post-Traumatic Arthritis. The treatment goal is anatomical reconstruction of the joint surface (<2mm step-off). The anatomy is complex, described by the Column Concept (Letournel). They are often associated with hip dislocations (Posterior Wall fracture is commonest). [1,2,3]

Key Facts

• The Inverted Y: The acetabulum is formed by an inverted Y-shape intersection of the Anterior Column and Posterior Column.
• Judet Views: Standard AP pelvis is insufficient. You need 45-degree oblique views (Obturator and Iliac) to see the columns.
• Sciatic Nerve: Runs directly behind the posterior column. Injured in 20% of posterior wall fractures/dislocations. Always document foot dorsiflexion (EHL) and sensation.
• Roof Arc Angle: Used to decide if surgery is needed. If the fracture is in the "Roof" (top weight-bearing 45 degrees), it MUST be fixed. If low down, it may be left.

Clinical Pearls

"The Spur Sign": Seen on the Obturator Oblique view. It represents a part of the iliac wing that has remained attached to the sacroiliac joint while the rest of the acetabulum has disconnected. It is pathognomonic for a Both Column Fracture (the floating acetabulum).

"The Gull Wing Sign": Seen on the superior acetabular dome. Indicates impaction of the roof. Poor prognostic sign (cartilage crushed).

"Native Hip vs THR": In the elderly, fixing an acetabulum is difficult (porous bone). Acute Total Hip Replacement (THR) with a cage/cup is increasingly favoured ("Fix and Replace").

              ACETABULAR FRACTURE
                       ↓
              HIP DISLOCATED?
              ┌───────┴───────┐
             YES             NO
              ↓              ↓
       URGENT REDUCTION    CT SCAN
       (Under Sedation)       ↓
              ↓           CONGRUENT?
       POST-REDUCTION CT  (Head centered)
              ↓           ┌───┴────┐
        INCARCERATED    YES       NO
         FRAGMENT?       ↓      (Traction /
        ┌─────┴─────┐  ROOF ARC   Surgery)
       YES         NO  >45 deg?
        ↓           ↓     ↓
     SURGICAL    STABLE?  └─→ NO: SURGERY
     REMOVAL    ┌───┴───┐     YES: CONSERVATIVE
              YES       NO
             (Wall    (Huge wall
             <20%)    defect)
               ↓         ↓
          MOBILISE    SURGERY

1. Conservative (Non-Operative)

• Indications:
  • Non-displaced fractures (<2mm).
  • Roof Arc Angle >45 degrees: The fracture exits outside the main weight bearing dome (measured on CT).
  • Secondary Congruence: The head and fragments have moved but match each other perfectly (rare).
  • Patient too unfit.
• Protocol: Touch weight bearing (crutches) for 6-12 weeks.

2. Surgical Fixation (ORIF)

• Indications:
  • Displacement >2mm in roof.
  • Hip Instability (Posterior wall >20-40% broken).
  • Incarcerated loose body in joint (grinds cartilage).
• Approaches:
  • Kocher-Langenbeck (Posterior): Gold standard for Posterior Wall/Column fractures. Prone position. Risk to Sciatic Nerve.
  • Ilioinguinal (Anterior): Old standard for Anterior fractures. Access via abdomen. Protective of vessels.
  • Stoppa (Modified Anterior): Window behind the rectus muscle. Great view of quadrilateral plate. New standard.

3. Acute Arthroplasty (Fix and Replace)

• Indication: Elderly (>70) with comminuted fracture and impaction (Gull Wing).
• Rationale: Fixation will fail/lead to arthritis in 1 year anyway. Do the replacement now. Use a cage to bridge the gap.

Letournel's Principles

• Anatomic reduction is paramount. "Perfect" reduction = 90% good result. "Imperfect" reduction = 20% good result.

STIFF Trial (Usually for Pelvic Ring, but relevant concepts)

• Early movement preferred.

BOAST Guidelines

• Refer to specialist centre (Pelvic Reconstruction Unit).
• Surgery within 5-10 days (before callus forms).

The Injury

You have broken the "socket" of the hip joint. It is like shattering a teacup. The ball is now grinding on rough edges.

The Plan

• The Goal: We need to put the teacup back together perfectly smooth so the ball can glide.
• Surgery: It is a big operation. We use metal plates and screws to rebuild the socket.
• Outcome: Even with perfect surgery, there is a risk of arthritis (wear and tear) in the future because the cartilage (lining) was damaged at the moment of impact. You might need a hip replacement in 5-10 years.

Q1: Describe the Judet Views and what they show. A: Two 45-degree oblique X-rays.

1. Obturator Oblique: Patient rolled 45 degrees AWAY. The beam looks through the obturator foramen perpendicularly. Shows the Anterior Column and the Posterior Wall.
2. Iliac Oblique: Patient rolled 45 degrees TOWARDS. The beam looks flat onto the Iliac wing. Shows the Posterior Column and the Anterior Wall.

Q2: What is the "Spur Sign"? A: A pathognomonic radiological sign seen on the Obturator Oblique view in Both Column fractures. It represents the lowest part of the intact ilium (the spur) appearing superior and posterior to the detached articular segment (the dome). It confirms the acetabulum has completely detached from the axial skeleton.

Q3: What determines if a Posterior Wall fracture needs fixing? A: Stability.

1. Size: If the fragment is >20-40% of the wall.
2. Examination: Examination Under Anaesthesia (EUA). If the hip dislocates when flexed and adducted, it is unstable and must be fixed.

(End of Topic)