Non-invasive assessment of sciatic nerve stiffness during human ankle motion using ultrasound shear wave elastography

Abstract

Peripheral nerves are exposed to mechanical stress during movement. However the in vivo mechanical properties of nerves remain largely unexplored. The primary aim of this study was to characterize the effect of passive dorsiflexion on sciatic nerve shear wave velocity (an index of stiffness) when the knee was in 90° flexion (knee 90°) or extended (knee 180°). The secondary aim was to determine the effect of five repeated dorsiflexions on the nerve shear wave velocity. Nine healthy participants were tested. The repeatability of sciatic nerve shear wave velocity was good for both knee 90° and knee 180° (ICCs ≥ 0.92, CVs ≤ 8.1%). The shear wave velocity of the sciatic nerve significantly increased (p<0.0001) during dorsiflexion when the knee was extended (knee 180°), but no changes were observed when the knee was flexed (90°). The shear wave velocity-angle relationship displayed a hysteresis for knee 180°. Although there was a tendency for the nerve shear wave velocity to decrease throughout the repetition of the five ankle dorsiflexions, the level of significance was not reached (p=0.055). These results demonstrate that the sciatic nerve stiffness can be non-invasively assessed during passive movements. In addition, the results highlight the importance of considering both the knee and the ankle position for clinical and biomechanical assessment of the sciatic nerve. This non-invasive technique offers new perspectives to provide new insights into nerve mechanics in both healthy and clinical populations (e.g., specific peripheral neuropathies).

Shear-Wave Elastography: Basic Physics and Musculoskeletal Applications

“…Promising results have been published in the recent literature on the utility of SWE in the evaluation of several traumatic and pathologic conditions of various musculoskeletal soft tissues, including tendons (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), muscles (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29), nerves (30)(31)(32), and ligaments (33)(34)(35).…”

Nerve stiffness - a challenge for ultrasound elastography

“…In our investigation strain elastrography have shown high and very usefull operating characteristics by ROC analysis (1,7). This can be explained by shortening of sciatic nerve diameter during the flexion.…”

“…The specificity was representative. The fibrous bands with nerve entrapment in patients with deep gluteal syndrome significantly decreased the diameter of sciatic nerve in extension, and sciatic nerve flexion movement, as the result of nerve tightening (1,4,5). It was observerd that movement resulted in the increased nerve stiffness (with increased strain ratio).…”

“…The radiographs and the MRI image of the lumbar spine and pelvis showed no pertinent findings, by Martin and Michel (12,13 Authors Andrade, Greening (2016Greening ( ,2017, Santos, Ellis (2015), Neto and Dikici reffered that elastography was applied (1,3,4,5,6,7,15 and 17) to develop diagnostic possibilities and improve therapeutic modalities. The full testing of sciatic nerve during limb movements have not been examined in detail, but Andrade and Ellis noticed sciatic nerve tightening with ankle and knee movements (1,5).…”

“…The full testing of sciatic nerve during limb movements have not been examined in detail, but Andrade and Ellis noticed sciatic nerve tightening with ankle and knee movements (1,5).…”