US Patent 8246646 Endoscopic balloon tissue dissector and retractor

In endoscopic surgery, a retractor having independently spreadable retractor blades mounted at the distal end of a tube is introduced percutaneously. A balloon dissector is passed through the tube and expanded. Following dissection by expansion of the balloon, the balloon is contracted, the tube is advanced, and the dissected tissue is spread by moving the blades apart from each other. The balloon dissector is withdrawn and another instrument is then introduced to carry out surgery on the anatomical structure exposed by the dissection and spreading steps.