An instrument for the penetration of tissue, including a backstop assembly having a shaft and a backstop; and a penetration member slidingly engaged with the backstop shaft, and configured for penetrating tissue. The backstop assembly and the penetration member are configured such that the backstop may...http://www.google.ca/patents/US6030402?utm_source=gb-gplus-sharePatent US6030402 - Apparatus and methods for the penetration of tissue, and the creation of an opening therein
