A cannula (10) for receiving surgical instruments for performing a surgical procedure on a body includes a tubular structure (12) defining a passage (16) through which the surgical instruments are inserted into the body. The tubular structure (12) includes an expandable portion (40) for enabling an increase...http://www.google.es/patents/US7766930?utm_source=gb-gplus-sharePatente US7766930 - Cannula for receiving surgical instruments
