**Question:** A 45-year-old driver is involved in a motor vehicle collision and sustains a posterior dislocation of the left hip. What is the most likely concomitant injury?

**Correct Answer:** D. Femoral neck fracture

**Core Concept:**
Posterior dislocation of the hip is a severe injury that occurs when the posterior aspect of the femoral head is pushed out of its acetabulum. This type of dislocation is often associated with significant trauma and can lead to concomitant injuries, such as fractures around the hip joint.

**Why the Correct Answer is Right:**
In the context of a posterior dislocation of the left hip, the most likely concomitant injury is a femoral neck fracture. This is because the posterior region of the femoral neck is particularly vulnerable due to its anatomical position and the force required to dislocate the hip. When a high-energy trauma occurs, such as in a motor vehicle collision, the force generated can result in both the dislocation and fracture simultaneously.

**Why Each Wrong Option is Incorrect:**

A. Anterolateral dislocation (Option A) typically involves the front of the hip and is less likely to result in a femoral neck fracture due to the different anatomy and force direction involved.
B. Anteroinferior dislocation (Option B) also involves the front of the hip but is less likely to cause a femoral neck fracture compared to the posterior dislocation.
C. Anterosuperior dislocation (Option C) involves the front of the hip, similar to Option A, making it less likely for a femoral neck fracture to occur.
D. As explained, the correct answer (Option D) is a femoral neck fracture due to the vulnerable anatomy and force direction during a posterior dislocation.

**Clinical Pearl:**
It is crucial for healthcare professionals to consider concomitant injuries when assessing patients with severe hip injuries, such as posterior dislocation. In the context of motor vehicle collisions, this helps in prompt and appropriate management, ensuring the patient receives timely and accurate treatment to avoid complications and improve prognosis.