What is the pathophysiology of nerve damage that leads to foot drop?

Updated: Mar 23, 2020
  • Author: James W Pritchett, MD; Chief Editor: Vinod K Panchbhavi, MD, FACS  more...
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Answer

The pathophysiology of nerve damage that commonly causes foot drop is as follows. The functional integrity of an axon and its target depends on the continued supply of trophic substances synthesized in the neuronal perikaryon and transported down the axon (axoplasmic flow). A laceration interrupts axoplasmic flow; a crush injury may compromise it as well. A double-crush phenomenon occurs when a proximal insult in a nerve root diminishes axoplasmic flow, making it more susceptible to injury.

A distal lesion further compromises axoplasmic flow, and clinical palsy results. This is the phenomenon thought to be responsible for the increased risk of foot drop after hip replacement in a patient with preexisting spinal stenosis. The spinal stenosis causes the proximal compromise, and intraoperative stretch of the sciatic nerve provides the distal insult.


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