Active cannulas

Abstract

An active cannula which does more than merely maintain a passage is usable to create and/or enlarge a passage, to position a scope or instrument, to move or locate tissue, etc. The cannula can vary in size or shape as needed, intraoperatively. Because a cannula of the present invention is expandable, the surgeon can make a relatively small incision, stretch the tissue with the expandable cannula, contract the cannula and remove it, allowing the skin to come back to its unstretched condition. Thus, a smaller incision can be made to fit the same size instrument. The cannulas can assume such a non-circular shape, to fit into a natural skin opening and cause less trauma. The devices can be used to seal off a space, expand an existing space or a potential space for working or visualization, move tissue (for example, to stretch an incision), or protect tissue.

I claim:  
     
         1 . A balloon dissection device comprising: 
 a support member having a longitudinal axis, a proximal portion, a central portion, a distal portion, and a lumen, wherein the central portion has a smaller diameter than a diameter of the proximal and distal portions; and    an inflatable balloon mounted on the support member and having an inner surface, an outer surface, a proximal end, a distal end, and an inflatable portion therebetween, the support member extending at least the entire length of the inflatable balloon when fully inflated such that the inflatable portion expands between the proximal and distal portions of the support member, the inflatable balloon comprised of a thin layer of uniform material wherein the thickness of the material is increased intermittently to form elongate ribs oriented along the inner surface of the balloon, the ribs having a longitudinal axis substantially parallel to the longitudinal axis of the support member.