In situ strain and stress of nerve conduction blocking in the brachial plexus.

The objective of the present study was to determine the in situ strain and stress of nerve conduction blocking in the brachial plexus. The measurement of the in situ tension stress inducing functional failure of the brachial plexus consisted of two steps. Step I (in vivo): The brachial plexus of the rabbit was stretched laterally until electrophysiological conduction blocking occurred. The distance between two dye marks placed on the lower trunk was simultaneously recorded using a video dimensional analyzer system. Step II (in vitro): The lower trunk that was removed was loaded again, and the nerve tension was recorded. The load at complete conduction blocking was determined by a load-elongation curve. The results showed that when the in situ nerve strain reached 8.1 +/- 0.5%, the compound muscle action potential was not evoked. The in situ load and stress were 2.5 +/- 0.4 N and 0.89 +/- 0.14 MPa, respectively, at complete conduction blocking. These findings should be helpful in understanding the mechanism of brachial plexus traction injury.