Dislocations of Hip

Aims of Treatment

• Primary Goal: Prevention of AVN and arthritis through emergent, congruent reduction.

Aetiology/Mechanism

• Posterior Dislocations: 9x more common than anterior dislocations.
• Mechanism:
  • Pure dislocations: Occur with more flexion and adduction.
  • Fracture-dislocations: Occur with lesser degrees of flexion.
• Increased Femoral Anteversion: Predisposes to fractures.
• Anterior Dislocations:
  • Caused by hyperabduction and external rotation.
  • Types: Obturator, iliac, or pubic, depending on the position of the femoral head.

Associated Injuries

• Knee, pelvis, femoral neck, femoral head, and acetabular (posterior wall).

Classification

Direction of Dislocation

• Posterior: Most common.
• Anterior: Subtypes include obturator, pubic, or iliac.

Pipkin Classification

• Management Notes:
  • Types 1 & 2: Non-operative if reduction is anatomical; lower threshold for surgery in Type 2.
  • Type 3: Worst prognosis. Perform urgent ORIF in young patients; arthroplasty in older patients.
  • Type 4: Management depends on acetabular fracture characteristics (position, size, stability).

Management

Examination

• Follow ATLS protocol.
• Assess leg position to determine the direction of dislocation.
• Evaluate neurovascular status.
• Screen for associated injuries.

Imaging

• X-rays: AP, Lateral, and Judet views.
• CT Scan: Essential for identifying associated fractures.

Reduction

• Advantages of ED Reduction:
  • Reduced time to reduction and immediate ability to proceed to CT if irreducible.
• Disadvantages:
  • Requires adequate relaxation to avoid failed attempts and cartilage damage.

Technique

• Apply in-line traction, exaggerate the deformity, and reverse the deformity.
• For posterior dislocations: Flexion, traction, and internal rotation.
• For anterior dislocations: Traction with external rotation.

Stability Testing

• Take AP, lateral, and Judet views to confirm congruency.
• Test stability under loading conditions.

Aims of Surgical Treatment

1. Achieve congruent reduction.
2. Ensure stability of the reduction.
3. Address associated fractures contributing to instability or incongruity.

Associated Femoral Neck Fractures

• Displaced: ORIF and open reduction of the hip.
• Undisplaced: Percutaneous pinning followed by closed reduction.

Post-Reduction Steps

• Confirm true congruency with fine-cut (2mm) CT scans.
• Remove loose bodies to prevent cartilage abrasion. This can be delayed.
• Open reduction and fixation required for displaced femoral head fractures (e.g., Pipkin 2).

Open Reduction

Indications

• Irreducible dislocations.
• Fixation of head or neck fractures.

Anterior Approaches

• Use Smith-Peterson (SP) or Watson-Jones (WJ) approach:
  • SP: Preferred for head fractures or removing incarcerated fragments.
  • WJ: Better for neck fractures.

Posterior Approach (Kocher-Langenbach)

• Indicated for posterior dislocations and posterior wall acetabular fractures.
• Protect the sciatic nerve by identifying it distally and keeping the hip extended with the knee flexed.

Trans-Trochanteric Approach (Ganz)

• Best for associated neck and head fractures.
• Involves surgical dislocation of the hip while preserving the medial femoral circumflex artery.

Outcomes and Complications

Prognostic Factors

• Time to Reduction: Early reduction reduces AVN risk.
• Associated Fractures: Increase complication rates.
• Repeated Reduction Attempts: Can damage the blood supply.
• Open Reduction: Risk of further violation and AVN.

AVN and OA Rates

• Simple Dislocations: AVN < 5%.
• Pipkin Types:
  • Type 1 & 2: Comparable to simple dislocations if fractures are anatomically reduced.
  • Type 4: AVN < 10%.
  • Type 3: Worst prognosis, AVN up to 50%.

Post-Traumatic OA

• More common in Pipkin 2 fractures (involves weight-bearing zone).