Okay, let's tackle this question about the Trendelenburg test and nerve injury. First, I need to recall what the Trendelenburg test is used for. From what I remember, it's a clinical test to assess the function of the hip abductors, specifically the gluteus medius and minimus muscles. The test is positive when there's weakness in these muscles, leading to a drop in the pelvis on the opposite side when standing on one leg.

Now, the question is asking which nerve injury would lead to a positive Trendelenburg test. The nerves that supply the hip abductors are important here. The gluteus medius and minimus are primarily innervated by the superior gluteal nerve. So if there's an injury to this nerve, those muscles wouldn't function properly, causing the Trendelenburg sign.

Wait, let me make sure. The superior gluteal nerve comes from the sacral plexus, specifically from the L4, L5, and S1 nerve roots. It innervates the gluteus medius, gluteus minimus, and tensor fasciae latae. If this nerve is damaged, those muscles can't abduct the hip, leading to the Trendelenburg sign. So the correct answer would be injury to the superior gluteal nerve.

Now, looking at the options (even though they aren't listed here), the distractors might include other nerves like the inferior gluteal nerve, which innervates the gluteus maximus. The gluteus maximus is more involved in hip extension, so an injury here wouldn't affect the Trendelenburg test. Another possible distractor could be the sciatic nerve, which affects the hamstrings and other muscles, but not the hip abductors. The femoral nerve innervates the quadriceps, so that's not relevant here either. The obturator nerve affects adductor muscles, so that's not it either.

The clinical pearl here is to remember that the Trendelenburg test is about hip abduction strength, so the key nerve is the superior gluteal nerve. A high-yield fact is that superior gluteal nerve injury can occur from trauma, childbirth, or pelvic surgery, leading to a positive Trendelenburg sign. Students should note that the inferior gluteal nerve is for the gluteus maximus and not involved in this test. Also, the test is positive when the patient can't maintain a level pelvis when standing on one leg, indicating weakness in the hip abductors.

**Core Concept**
The Trendelenburg test assesses the function of the hip abductor muscles (gluteus medius and minimus), which are innervated by the **superior gluteal nerve**. A positive test indicates weakness in these muscles, commonly due to nerve injury or neuromuscular disease.

**Why the Correct Answer is Right**
The **superior gluteal nerve** (L4–S1) innervates the gluteus medius, gluteus minimus, and tensor fasciae latae. Injury to this nerve impairs hip abduction, leading to a positive Trendelenburg test (pelvic drop on the contralateral side when standing on one leg). This occurs because the affected hip cannot stabilize the pelvis during single-leg stance.

**Why Each Wrong Option

✓ Correct Answer: B. Superior gluteal nerve