After an intramuscular injection into the upper outer quadrant of the buttock in an infant, the pelvis drops on the opposite side when the child stands on the injected limb. The injected limb's hip also fails to abduct against resistance. Which nerve is affected?

• A Sciatic nerve
• B Inferior gluteal nerve
• C Nerve to obturator internus
• D Superior gluteal nerve ✓

Explanation

D positive Trendelenburg sign with failure of hip abduction points to the superior gluteal nerve (L4 to S1), which supplies gluteus medius, gluteus minimus and tensor fasciae latae. It leaves the greater sciatic foramen above piriformis and crosses close to the iliac crest region targeted by misplaced injections. The inferior gluteal nerve supplies gluteus maximus, whose main action is extension, not stabilisation during single-leg stance.

Reference: Maheshwari and Mhaskar, Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.