Safety trocar instrument having a retractable point actuated by a trigger sleeve

摘要

A safety trocar instrument, for piercing the wall of an anatomical cavity to provide communication with the inside of the cavity, includes a tubular cannula and an elongate trocar having a sharp piercing point. The trocar is mounted for axial reciprocal movement within the cannula between a withdrawn rest position in which the point is received within and shielded by the distal end of the cannula and a projecting position in which said point is exposed beyond the distal end of the cannula. A retraction spring biases the trocar to its withdrawn position. A latch latches the trocar in the projecting position in opposition to the retraction spring, and a trip member can trip the latch to unlatch the trocar and thereby permit the trocar to be moved to its withdrawn rest position by the retraction spring. A mechanical trigger in the form of a trigger sleeve is mounted within the instrument. Its distal end is locatable between the extreme of said trocar point and the distal end of the cannula to sense counterforce exerted by the cavity wall after it has begun to be pierced by the trocar point and to sense relief of such counterforce when that distal end has cleared the cavity wall. The trigger sleeve is mechanically coupleable to the trip member to cause it to trip the latch in response to sensing relief of such counterforce.