Stretching of the brachial plexus in rabbits.

The brachial plexus of rabbits was stretched until mechanical failure. The level and site of rupture varied according to the direction of the stretching force. Upward and lateral traction of the forelimbs caused spinal nerve-root avulsions combined with nerve-trunk ruptures distal to the dorsal root ganglions. In such tractions the C5 nerves consistently exhibited postganglionic nerve-trunk rupture. The C6, C7, and C8 nerves had root avulsions. The T1 nerve was avulsed from the spinal cord in 7 cases out of 10; the other 3 cases had postganglionic nerve-trunk rupture. Downward traction of the forelimbs caused nerve avulsions from the scapulohumeral muscles innervated by the terminal branches of the brachial plexus and peripheral nerve ruptures in the course of the arm. The force producing trunk rupture of the C6 nerve was twice as great as that for root avulsion. The required stain was similar for nerve trunk rupture and root avulsion.