Posterior cord
Cords · C5 C6 C7 C8 T1
Carries fibres from all five roots. Its branches are remembered as ULTRA: Upper subscapular, Lower subscapular, Thoracodorsal, Radial, Axillary — a memory word, not the order of origin, which runs upper subscapular, then thoracodorsal, then lower subscapular, with axillary and radial as the terminal branches.
Traced from the start
Detail
- Motor
- The whole extensor compartment of the arm and forearm, plus deltoid and latissimus dorsi
- Sensory
- Posterior arm and forearm, and the dorsum of the radial side of the hand
When it goes wrong
Anterior dislocation of the shoulder, or a penetrating axillary wound
Wrist drop with weak elbow extension and weak abduction, with loss of the regimental badge patch — a combined radial and axillary picture, since both arise here. Crutch pressure in the axilla catches the radial nerve alone: wrist drop with weak triceps, but the deltoid is spared, because the axillary nerve has already left through the quadrangular space.
Practise this structure
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