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.
- Pure dislocations: Occur with more flexion and adduction.
- 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.
- Caused by hyperabduction and external rotation.
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
| Type | Features | AVN Rate |
|---|---|---|
| 1 | Dislocation with fracture inferior to fovea (non-weight-bearing zone). | <5% |
| 2 | Dislocation with fracture superior to fovea (weight-bearing zone). | <5% |
| 3 | Type 1 or 2 with associated femoral neck fracture. | 50% |
| 4 | Type 1 or 2 with associated acetabular fracture. | 10% |
- 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).
- Types 1 & 2: Non-operative if reduction is anatomical; lower threshold for surgery in Type 2.
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.
- 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
- Achieve congruent reduction.
- Ensure stability of the reduction.
- 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.
- SP: Preferred for head fractures or removing incarcerated fragments.
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%.
- Type 1 & 2: Comparable to simple dislocations if fractures are anatomically reduced.
Post-Traumatic OA
- More common in Pipkin 2 fractures (involves weight-bearing zone).