US Patent 9089363 Arthroscopic cannula dams for fluid control

A cannula with a tri-slot dam assembly including two primary dams as the main fluid seal and an adjacent outer “baffle-like dam” that prevents fluid pressure build-up and allows the fluid to leak out and not squirt out of the cannula. The baffle-like dam has a body formed of a low profile material and is provided with a plurality of small through holes or perforations to allow fluid to gently leak out. Fluid that enters the outer chamber leaks out of the through holes so that the fluid pressure between the baffle and the primary dams is very low. A spacer is optionally provided between the two primary dams and the outer dam to prevent the dams from interfering with each other and allow them to remain open.