A spinal anulus cutter for cutting a multisided flap in an encapsulating ligament, such as an anulus of a human intervertebral disc, to provide access to an interior space or material surrounded by the ligament. The spinal anulus cutter is characterized by a knife blade comprised of a plurality of walls...http://www.google.es/patents/US5649945?utm_source=gb-gplus-sharePatente US5649945 - Spinal anulus cutter
