An expandable tip cannula system, comprising: a hollow cannula shaft having a proximal end and a distal end; and an expandable tip mounted at the distal end of the hollow cannula shaft, the expandable tip comprising a plurality of generally-triangular shaped petals held together in a radially-inwardly...http://www.google.ca/patents/US8165653?utm_source=gb-gplus-sharePatent US8165653 - Surgical access and nerve surveillance
