Description

• Displacement of the femoral head from the acetabulum
• ~5% of all traumatic joint dislocations (1)[A]
• True orthopedic emergency

Epidemiology

• Highest rates occur in males than females and in ages 16 to 40 years; most commonly from motor vehicle collisions (2)[B]
• 70–100% of posterior hip dislocations occur secondary to motor vehicle collisions (2)[B]; there is also a higher incidence of right hip dislocations (2)[B].

Etiology and Pathophysiology

• Protective factors: depth of acetabulum, surrounding labrum, thick joint capsule, and strong muscular support
• Caused by high-velocity mechanisms—most commonly “dashboard” leg injuries in motor vehicle collisions and falls from a height (1,3)[A]
• Posterior dislocations represent 85–90% of traumatic dislocations; anterior dislocations 10–15% (1,2)[B]
• Posterior dislocations occur when the knee is flexed and the hip is adducted and flexed.
• Anterior dislocations occur when the hip is abducted and externally rotated.
• Anterior dislocations can occur in sporting activities such as American football, rugby, skiing, bicycling, basketball, and gymnastics (4)[C].

Pediatric Considerations

• The force required to cause a dislocation increases with age. Minor trauma may produce dislocation before age 10 years. Higher energy trauma is typical after age 12 years (5)[C].
• The femoral epiphysis may be injured during dislocation, complicating long-term prognosis. Surgical reduction is necessary (5)[C].
• Immobilization postreduction in a spica cast or bed rest for 3 to 4 weeks is recommended for children age <10 years (5)[C].
• Up to 25% of pediatric hip dislocations have a labral injury or loose osteochondral fragment (5)[C].

Commonly Associated Conditions

• Acetabular fractures
• 25% have ipsilateral knee injuries (2)[B].
• Sciatic nerve damage (10–14% of posterior dislocations) (1,2)[B]
• Exclude closed head injuries, thoracic injuries, and abdominal and pelvic injuries in high-velocity injuries.