This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper limb, Subject name: Anatomy
Winging of scapula is due to which of these conditions? 
Select and explain. 
A. Long thoracic nerve palsy, B. Thoraco-dorsal nerve palsy, C. Erb's palsy, D. Klumpke's palsy
A: Long thoracic nerve palsy
Answer: A: Long thoracic nerve palsy 
Explanation: Winging of scapula is due to the paralysis of Serratus anterior muscle which is supplied by long thoracic nerve . Long thoraic nerve damage causes paralysis of Serratus muscle. FEATURES: 1)Medial border of the bone becomes unduly prominent 2)Arm cannot be abducted 90 degrees. REF:B D Chaurasia 7th edition Page no: 45. Figure :3.9,page no:38-Vishram Singh - upper limb& thorax, 2nd edition