A newborn delivered after difficult labour holds the upper limb internally rotated at the shoulder, extended at the elbow, pronated at the forearm, with the wrist flexed. The root values and typical mechanism of this deformity are:

• A C5, C6 excessive separation of the head and shoulder during vertex delivery ✓
• B C8, T1 traction during breech delivery with arm abducted overhead
• C C5 to T1 complete avulsion from the spinal cord
• D C7 isolated stretch during shoulder dystocia

Explanation

This is Erb-Duchenne paralysis of C5 and C6 roots from excessive lateral traction separating the head from the shoulder during vertex delivery, producing the classic waiter's tip posture. Option B describes the mechanism of Klumpke's paralysis, which gives a claw hand and possible Horner's syndrome. Complete avulsion would produce a flail insensate limb, not a stereotyped posture, and isolated C7 injury does not produce waiter's tip.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.