Ultrasound strain elastography for peripheral nerves localization for regional anesthesia A prospective observational pilot study.

Ultrasound Elastography (UE) tends to improve the ultrasound diagnosis accuracy. The Strain Elastography (SE) depicts the pathological tissue loss of elasticity in response to an external pressure applied by the operator. It is now recommended for benign/malignant parenchymal process differentiation and for muscle and nervous rigidness assessment and follow-up. The SE was able to differentiate the normal nerves from their muscular-vascular environment based on their own elasticity using a colorimetric scale (CS)0.30 healthy adult patients were included into this prospective observational study. The femoral nerve (FN) and the popliteal sciatic nerve (PSN) were studied using 2D black and white sonography (S) and SE. About the SE, firstly, CS goes from red (stiffer) to blue (softer) differentiating 6 main colors at the visual assessment. Secondly, the CS was transformed into a 3 points tissues classification related to FN and PSN elasticity for easier reading. Results are presented as percentages.FN and PSN in sonography were normal in all patients confirming the different morphology of each kind of nerve with a high level of patient-to-patient reproducibility. SE detected as "stiff" the FN and PSN in respectively 87 and 83% of the patients. Finally, a superposition between sonogram and elastogram greater than 50% was observed in 54 and 70% of the patients.SE represents a promising technique that may complement S to try to improve the quality of nerve localization. Further and larger studies are needed for a better understanding the subject in real clinical conditions.