Classic history and presentation: The patient typically presents with an inability to bear weight on the affected lower extremity along with severe groin and/or buttock pain. If the dislocation is posteriorly directed (90%-95% of cases), the affected extremity will appear shortened, slightly flexed, adducted, and internally rotated. If the dislocation is anteriorly directed, the affected extremity will appear extended, abducted, and externally rotated. If the dislocation is inferiorly directed, the affected extremity will appear hyperflexed or abducted. An associated traumatic event with the affected lower extremity is almost always present.
Prevalence: THDs in the pediatric population are rare and make up approximately 5% of all pediatric dislocations. 90%-95% of these dislocations are directed posteriorly.
- Sex / gender – This condition can occur in either sex but is more common 4:1 in males.
- In patients aged older than 10 years, high-energy trauma such as a motor vehicle accident (MVA).
- In patients aged younger than 10 years, low-energy trauma such as a sports injury or fall.
Classification system: Hip dislocations can be classified by their direction and further described by the head-acetabulum relationship and presence or absence of associated fractures. These classifications are traditionally used for adult THDs but may be referenced in the pediatric and adolescent populations.
Posterior hip dislocations (Thompson and Epstein classification)
- Type 1 – Simple dislocation with no or minor fracture
- Type 2 – Dislocation with a single large fracture of posterior acetabular rim
- Type 3 – Dislocation with a comminuted acetabular rim
- Type 4 – Dislocation with a fracture of the acetabular floor
- Type 5 – Dislocation with a fracture of the femoral head
- Type 1 – Superior dislocations (pubic and subspinous)
- Type 1A – No associated fractures
- Type 1B – Associated fracture or impaction of femoral head
- Type 1C – Associated fracture of acetabulum
- Type 2 – Inferior dislocations (obturator and perineal)
- Type 2A – No associated fractures
- Type 2B – Associated fracture or impaction of femoral head
- Type 2C – Associated fracture of acetabulum