Snapshot A 27-year-old woman presents to the emergency room with severe hip pain after being a passenger in a head-on motor vehicle accident. On physical exam, she has significant pain and deformity in her left hip. Her left hip is adducted, flexed, and internally rotated. Introduction Clinical definition condition in which the femoral head is pushed out of the acetabulum in adults, almost always occurs in the setting of significant trauma Epidemiology incidence rare injury most common mechanism of injury is motor vehicle accident 90% of dislocations are posterior 10% of dislocations are anterior demographics 4:1 male-to-female ratio most commonly affects adolescents and adults aged 16-40 risk factors significant trauma Etiology traumatic developmental developmental dysplasia of the hip neuromuscular cerebral palsy Pathoanatomy normal anatomy hip joint is inherently stable due to bony ball-and-socket architecture soft tissue constraints labrum, joint capsule, and hip musculature significant trauma is therefore required to overcome the inherent stability of the joint mechanism axial loading on adducted femur predisposes to posterior dislocation dashboard injury axial loading on abducted and externally rotated femur predisposes to anterior dislocation Associated conditions 95% incidence of concomitant injuries to other areas of the body acetabular and femoral head or neck fractures knee ligamentous and meniscal injuries closed head injuries Prognosis favorable anterior dislocations simple dislocations (no associated fractures) Presentation Symptoms severe pain and immobilty in the affected hip may also complain of lower back, thigh, knee, or lower leg pain Physical exam hip position posterior dislocation hip will be flexed, adducted, and internally rotated anterior dislocation hip will be flexed, abducted, and externally rotated pain with passive or active movement thorough head-to-toe examination following Advanced Trauma Life Support (ATLS) protocols must be performed given high incidence of concomitant head and extremity injuries Imaging Radiographs indication anteroposterior (AP) pelvis radiograph always indicated when hip dislocation is suspected finding posterior hip dislocation femoral head smaller than contralateral side and superior to acetabulum femur appears adducted internal rotation of femur noted as lesser trochanter will be poorly visualized anterior hip dislocation femoral head appears larger than contralateral side and inferior to acetabulum femur appears abducted external rotation of femur noted as lesser trochanter will be in full profile Computerized tomography (CT) scan indication high suspicion for associated fractures finding associated fractures to acetabulum, femoral head, and femoral neck Differential Femoral neck fracture hip will remain in acetabulum on AP pelvis radiograph Acetabular fracture hip will remain in acetabulum on AP pelvis radiograph Treatment Conservative closed reduction under conscious sedation indication closed reduction should be attempted in all traumatically dislocated hips Operative open reduction indication failure of closed reduction Complications Avascular necrosis of femoral head Sciatic nerve injury Post-traumatic osteoarthritis