A newborn delivered after shoulder dystocia holds the upper limb adducted and internally rotated, with the forearm pronated and the wrist flexed. The biceps reflex is absent on that side. Which roots are injured?

• A T1 and T2
• B C8 and T1
• C C7 and C8
• D C5 and C6 ✓

Explanation

The waiter's tip posture results from upper trunk (C5, C6) injury, classically Erb-Duchenne palsy caused by traction during shoulder dystocia. C5 supplies supraspinatus, deltoid and biceps, so abduction, external rotation and elbow flexion are lost while the intact lower trunk keeps the wrist flexors working. C8 and T1 injury produces the opposite picture, a Klumpke palsy with clawing and intrinsic muscle weakness.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.