A newborn is delivered after shoulder dystocia. The right arm lies adducted and internally rotated, with the elbow extended, forearm pronated, and wrist flexed. Which roots are injured?
- A C8 and T1
- B C5 and C6 ✓
- C C7 alone
- D T1 and T2
Correct answer: B. C5 and C6
Explanation
The posture described is the classic waiter's tip deformity of Erb's palsy, caused by traction on the upper trunk during shoulder dystocia. C5 and C6 supply the deltoid, supraspinatus, infraspinatus, biceps and brachioradialis, so abduction, external rotation, elbow flexion and supination are lost. C8 and T1 correspond to Klumpke's palsy, which produces a claw hand rather than a waiter's tip position.
Reference: Gray's Anatomy for Students, 4th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.