US Patent 8939963 Surgical instruments with sheathed tendons

A flexible surgical instrument employs sheaths around tendons that actuate an end effector or other mechanisms in a distal tip of the instrument. A liquid lubricant can be introduced in the sheaths to reduce friction, and the sheaths can be porous or non-porous. The lubricant can be confined, for example, with an o-ring or a bellow seal, to keep lubricant from leaking where the tendons extend out of the sheaths. More generally, the distal end of the instrument is sealed to prevent leakage of lubricant into a patient. To further reduce risks, a non-toxic water-based lubricant can be used.