A cannula has a hub formed with a hollow upward projection on its top which communicates with a lumen having a bore in the hub and the cannula itself. On one side of the hub is a vane having converging sides and a rounded end. The vane has a horizontal opening extending inward and the portion above the...http://www.google.co.uk/patents/US4511356?utm_source=gb-gplus-sharePatent US4511356 - Cannula, obturator, stylet and needle hub connectors for lumbar disc puncture
