A 17-year-old boy was stabbed during a gang fight, resulting in the transection of the obturator nerve. Which of the following muscles is completely paralyzed?
**Core Concept**
The obturator nerve is a branch of the lumbar plexus, responsible for innervating the adductor muscles of the thigh. Transection of the obturator nerve would lead to paralysis of the muscles it supplies, primarily affecting thigh adduction.
**Why the Correct Answer is Right**
The obturator nerve innervates the adductor longus, adductor brevis, adductor magnus (adductor part), and the gracilis muscle. These muscles work together to facilitate adduction of the thigh. With the obturator nerve transected, these muscles would be paralyzed, leading to a significant impairment in thigh adduction. This would result in a weakened or absent ability to bring the thigh towards the midline of the body.
**Why Each Wrong Option is Incorrect**
* **Option A:** The quadriceps femoris muscle is primarily innervated by the femoral nerve, not the obturator nerve. Therefore, transection of the obturator nerve would not affect the quadriceps femoris muscle.
* **Option B:** The hamstrings are primarily innervated by the tibial nerve (L5-S2), which is a different nerve from the obturator nerve. Therefore, transection of the obturator nerve would not affect the hamstrings.
* **Option C:** The tensor fasciae latae muscle is primarily innervated by the superior gluteal nerve, not the obturator nerve. Therefore, transection of the obturator nerve would not affect the tensor fasciae latae muscle.
**Clinical Pearl / High-Yield Fact**
The obturator nerve is at risk during surgery involving the hip and pelvic areas, such as hip arthroplasty or pelvic fractures. Damage to this nerve can lead to significant morbidity and impairment in thigh function.
**Correct Answer:** C.