Question

A 30-year-old man presents to the emergency department after being involved in a head-on motor vehicle crash. He is complaining of severe pain in his right hip. On exam, his right leg appears to be shortened and is held slightly flexed, internally rotated, and adducted. Range of motion is severely limited due to pain. An anterior-posterior plain radiograph is negative for fractures, but the right femoral head appears smaller than the uninjured side. Which of the following is the most likely diagnosis?

A) Anterior hip dislocation
B) Avascular necrosis of the femoral head
C) Posterior hip dislocation
D) Slipped capital femoral epiphysis

Answer 1

The most likely diagnosis for the patient's symptoms and radiograph findings is a Posterior hip dislocation, consistent with the clinical presentation and mechanism of injury.

Step-by-step explanation:

The most likely diagnosis for the 30-year-old man with severe pain in the right hip, showing a shortened and internally rotated leg, with an anterior-posterior plain radiograph negative for fractures but with a smaller appearance of the right femoral head than the uninjured side, is Posterior hip dislocation (C).

Hip dislocations are generally caused by significant trauma, such as a motor vehicle crash, and the described clinical presentation of the leg being shortened, internally rotated, and adducted is characteristic of a posterior hip dislocation. The symptomatic limitation in the range of motion due to severe pain also aligns with this diagnosis. Although an X-ray image might not show a visible fracture, the dislocation could cause the femoral head to appear smaller on the X-ray due to its posterior displacement.