An expandable cannula having a plurality of wall surfaces, the wall surfaces being foldable together one over another such that the cannula assumes a first cross sectional area, and the wall surfaces being unfoldable such that the cannula assumes a second cross sectional area, wherein the first cross...http://www.google.fr/patents/US6312443?utm_source=gb-gplus-shareBrevet US6312443 - Expandable cannula
