What is the most appropriate initial intervention for a patient with severe hip pain and a suspected hip fracture or dislocation after a motor vehicle collision?

Initial Management of Posterior Hip Dislocation

The most appropriate initial intervention is immediate closed reduction of the hip dislocation under procedural sedation, ideally within 6 hours of injury to minimize the risk of avascular necrosis. 1, 2, 3

Clinical Recognition

The clinical presentation described—shortened, adducted, and internally rotated left lower extremity with a smaller-appearing femoral head on AP radiograph—is pathognomonic for posterior hip dislocation, the most common type of traumatic hip dislocation. 4, 2

• The smaller appearance of the femoral head on AP radiograph occurs because the posteriorly displaced femoral head is further from the X-ray plate, creating a magnification artifact that makes it appear smaller than the contralateral side 5
• This is a surgical emergency requiring urgent reduction, not just diagnostic imaging 6, 1, 3

Immediate Management Algorithm

Step 1: Pain Control and Immobilization (Do Not Delay Reduction)

• Administer immediate analgesia with acetaminophen 1000 mg IV and consider a fascia iliaca or femoral nerve block for superior pain control 7, 8
• Nerve blocks provide adequate analgesia for reduction procedures and may allow successful reduction with lighter sedation 8
• Immobilize the hip in the position found; do not attempt to manipulate before procedural sedation 6

Step 2: Confirm Diagnosis with Portable Radiography

• Obtain AP pelvis and cross-table lateral hip views in the trauma bay without moving the patient 5
• Critical pitfall: Do not delay reduction to obtain imaging if the clinical diagnosis is obvious—radiographic confirmation should not postpone treatment 6
• The cross-table lateral view is essential and preferred over frog-leg lateral due to risk of further displacement 5

Step 3: Emergent Closed Reduction

• Perform closed reduction under procedural sedation (or general anesthesia if needed) as soon as possible, ideally within 6 hours of injury 1, 2, 3
• For posterior dislocations: Apply longitudinal traction with the hip flexed to 90 degrees and gentle internal rotation while an assistant stabilizes the pelvis 2
• Reduction within 24 hours yields significantly better outcomes than delayed reduction, but earlier is always better 3
• Avoid multiple attempts at closed reduction—if initial attempts fail, proceed directly to open reduction 3

Step 4: Post-Reduction Imaging

• Obtain immediate post-reduction AP pelvis and cross-table lateral radiographs to confirm concentric reduction 6, 3
• Mandatory: Perform CT scan of the hip after reduction to assess for associated femoral head fractures, acetabular fractures, and to ensure concentric reduction 6, 2
• Any abnormality on post-reduction imaging or failure to achieve concentric reduction demands immediate hip arthrotomy 3

Critical Time-Dependent Complications

The risk of avascular necrosis increases dramatically with time to reduction:

• Reduction within 6 hours minimizes osteonecrosis risk 1
• Reduction within 24 hours is associated with better functional outcomes than delayed reduction 3
• Early reduction also reduces the risk of sciatic nerve injury progression 3

Common Pitfalls to Avoid

• Do not obtain CT or MRI before attempting reduction—these advanced imaging studies are for post-reduction assessment only 6, 2
• Do not perform multiple closed reduction attempts—this increases the risk of iatrogenic femoral head or acetabular fractures 3
• Do not use frog-leg lateral radiographs—the positioning required can cause fracture displacement 5
• Do not delay surgery for medical optimization in obvious hip dislocations—the dislocation itself is the emergency 5, 1

Post-Reduction Management

• Provide multimodal analgesia with scheduled acetaminophen and nerve blocks per American Academy of Orthopaedic Surgeons strong recommendation 7
• Initiate thromboembolic prophylaxis with low-molecular-weight heparin 4
• Administer prophylactic antibiotics if surgical intervention was required 6, 4
• Begin early mobilization as tolerated after confirming concentric reduction and ruling out associated fractures 6