An experimental study on the "double crush" hypothesis.

An experimental study investigated the vulnerability of peripheral nerves in the "double crush" situation. Canine sciatic nerves were studied by means of electrophysiologic and histologic examination. Compression was applied by the KEIO compression clamp, with compression force of 15 g (approximately, 27.6 mm Hg). An incomplete conduction block and mild axonal degeneration were induced by a single compression. However, a complete conduction block and severe axonal degeneration could be induced in half of the cases by the double compression. In these cases, the loss of nerve function after a double lesion was greater than the sum of the deficits after each separate lesion. A good therapeutic effect was obtained by removing all compression, but the effect was incomplete when either compression was retained. It is concluded that proximal compression of a nerve could lessen its ability to withstand further compression more distally.