Using ultrasound elastography to quantify sciatic nerve displacement

As the body moves, peripheral nerves are constantly being exposed to mechanical forces and stress from the surrounding tissues that they come into contact with. These surrounding tissues, otherwise known as the “mechanical interface,” are varied. For nerves to maintain optimal impulse conduction, intraneural blood flow, and axoplasmic flow, they must be able to independently move in response to these interfacing tissues to dissipate mechanical forces. An important mechanical interface for the sciatic nerve is that of the hamstring muscles.

The study of Ellis et al. (2018) showed that ultrasound (US) elastography was seen to be a reliable method for calculating sciatic nerve–hamstring muscle interface shear strain and sciatic nerve displacement. Both active and passive knee extension resulted in substantial shear strain. Displacement and shear strain measurement was more reliable for the flexion exercise condition. An examination in clinical populations may provide a deeper understanding of etiologic factors in conditions such as entrapment neuropathies and, furthermore, for the design of therapeutic exercises to influence nerve mechanics.