| 摘要 |
A cannula (10) for fixation within a portal to provide access to a surgical worksite by a surgical instrument, comprises an elongate tubular body (12) defining a passage (14) for receiving a surgical instrument, the tubular body having an upper end (16) and a lower end (18), a sealing assembly (20) located at the upper end for sealingly receiving a surgical instrument, and a generally cylindrical sleeve (22) surrounding and extending along at least part of the tubular body. The sleeve has a lower end (24) which is secured to the tubular body, an upper end (26) and an external screw thread (28) and is of a flexible material so that stretching the sleeve in the direction (29) of the upper end of the tubular body by displacing the tubular body and sleeve relative to each other increases the pitch (32) and reduces the depth (34) of the thread and relative displacement in the opposite direction reduces the pitch and increases the depth of the thread. |
