Anaesthesia
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Despite widespread use of ultrasound imaging to guide needle placement, the incidence of transient and permanent nerve damage as a complication of regional anaesthesia has not changed over the last decade. In view of the controversy surrounding intraneural injection there is a need to understand the structural changes caused by subepineural and subperineural needle penetration. Clinical ultrasound machines do not provide adequate anatomical resolution, and anaesthetists have difficulty judging the precise location of the needle tip relative to the epineurium. ⋯ A regional block needle was inserted into three median nerves. We identified fascicles > 0.4 mm in width using micro-ultrasound. Subepineural needle placement was associated with denting, rotation and elastic deformation of fascicles, whereas subperineural needle insertion split fascicles permanently.