Surgical tool

DETAILED DESCRIPTION A surgical tool according to the present invention includes a hollow cylindrical housing open at one end and having a reduced diameter bore through an end wall at the opposite end of the housing.
Within the housing, a piston-like plunger is slidably received and formed with an integral elongate rod projecting outwardly from the housing through the bore in the housing end wall.
A compression spring is engaged between the plunger and housing end wall biassing the plunger in a direction tending to retract the projecting rod into the housing.
The plunger is normally maintained at an inward end limit of movement within the housing by a plug member which projects into the open end of the housing.
A locking pin extending through aligned diametrically extending bores in the housing sidewall and plug member releasably locks the plug member in a seated position which maintains the plunger at its inward end limit of movement relative to the housing with the plunger engaging spring at a maximum compression.
A hollow cylindrical cutter or trephine, sharpened at one edge to form a circular cutting edge of a specific diameter, has a relatively thick bottom wall at its opposite end formed with a central internally threaded bore by means of which the cutter may be threaded onto threads cut at the end of the plunger rod to attach the cutter to the rod with its cutting edge facing the end wall of the cylindrical housing.
In use, the cutter is detached from the rod and inserted into a pocket beneath the patient's skin with the cutting edge facing the skin.
The threaded end of the rod is then inserted through a relatively small hole punched through the skin and threaded into the cutter which is held during this procedure, as by a hemostat or tweezers.
After the cutter has been threaded onto the rod, the locking pin is withdrawn and the plunger is driven by the spring to retract the rod until the cutting edge engages the end wall of the housing.
A washer-like seat may be mounted on the outside of the end wall of the housing to form a shearing edge cooperable with the cutting edge of the cutting element