**Core Concept**
The dermatome of the posterior thigh is a region of skin supplied by a specific spinal nerve. Dermatomes are areas of skin that correspond to the sensory distribution of a particular spinal nerve root. Understanding dermatomes is essential for diagnosing nerve root lesions and determining the level of spinal cord injury.

**Why the Correct Answer is Right**
The posterior thigh is innervated by the L2-L4 nerve roots, which are part of the lumbar plexus. The L2-L4 nerve roots give rise to the femoral nerve, which supplies the anterior thigh, and the obturator nerve, which supplies the medial thigh. However, the posterior thigh is primarily innervated by the L2-L4 nerve roots through their branches to the cutaneous nerves, including the superior and inferior cluneal nerves.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the anterior thigh is primarily innervated by the L2-L4 nerve roots through the femoral nerve, not the posterior thigh.
* **Option B:** This option is incorrect because the medial thigh is primarily innervated by the L2-L4 nerve roots through the obturator nerve, not the posterior thigh.
* **Option C:** This option is incorrect because the gluteal region is primarily innervated by the S1-S3 nerve roots through the inferior gluteal nerve, not the posterior thigh.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that dermatomes are not strictly anatomical boundaries, but rather areas of skin that correspond to the sensory distribution of a particular spinal nerve root. This knowledge is crucial for diagnosing nerve root lesions and determining the level of spinal cord injury.

**Correct Answer: L2-L4**, The dermatome of the posterior thigh is supplied by the L2-L4 nerve roots.