Anterior Hip Dislocation

Hip dislocations after trauma are frequently encountered in the emergency setting. A significant force is generally required to dislocate a hip as this ball and socket joint is quite stable due to its bony structure and the associated muscular and ligamentous attachments. Due to the required force, hip dislocations often are associated with other significant injuries; for example, fractures are found in over 50% of these patients. The majority of all hip dislocations are due to motor vehicle accidents. Posterior hip dislocations are the most common type, with anterior occurring only about 10% of the time. These injuries are true orthopedic emergencies and should be reduced expediently. The majority will resolve with a closed reduction in the emergency department. Anatomy The hip joint is a synovial ball-and-socket structure with stability related to both its bony and ligamentous arrangement. The acetabulum covers approximately 40% of the femoral head during all maneuvers, and the labrum serves to deepen this joint and adds additional stability. Furthermore, the hip joint capsule is composed of dense fibers that preclude extreme hip extension. The main blood supply to the femoral head arises from the medial and lateral femoral circumflex arteries, which are branches of the profunda femoral artery. Branches off of this supply enter the bone just inferior to the femoral head after ascending along the femoral neck. This arrangement allows for a plentiful but tenuous blood supply to the femoral neck, especially when considering a traumatic hip injury to the femoral head. The sciatic nerve exits the pelvis at the greater sciatic notch and lays just infero-posterior to the hip joint. The femoral nerve lies just anterior to the hip joint.