Surgical trephine

Details Surgical trephine Surgical trephine

1999-10-13

2001-03-13

Buiz, Michael (Department: 3731)

Surgery

Instruments

Orthopedic instrumentation

Reexamination Certificate

active

06200319

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a surgical trephine adapted for boring an opening in tamped bone chips.
2. Description of the Prior Art
Modern surgical techniques, especially as applied to hip prostheses, sometimes require a prosthetic device with an elongated stem. These devices are used when not only are there problems with the hip joint but where there is also the possibility of fracturing in the length of the femur. The addition of a standard length prosthesis stem into such a femur can sometimes create further problems and for this reason a stem of much longer length is employed. The distal portion of such stems is usually parallel because of the extended length and the narrowing of the femur and its intramedullary canal.
In modern techniques bone chips can be employed to line the intramedullary canal and these chips are first tamped into position, for example as described and shown in the Applicants U.S. Pat. No. 5,788,704. This patent shows a method and apparatus for implanting a prosthesis in which a bone cavity is filled with bone chips which are compressed.
When such a technique is used for long prosthesis stems there are difficulties in shaping the distal end of the cavity due, not only to the long length, but also to the possibilities of causing further compression of the bone chips and thus tending to expand the filling and create fractures in the bone structure.
The present invention is intended to provide an instrument which can be used for cutting the required cavity into the bone chips in operations of the kind described above, although it can be used for any cavity in which bone chips are used and a substantially parallel cavity is required.
SUMMARY OF THE INVENTION
According to the present invention a surgical trephine adapted for boring an opening in tamped bone chips includes a hollow elongate body portion having an internal bore and the distal end of which has an annular cutting rim, a piston located in the bore with a piston surface facing towards said cutting rim and means for moving the piston in the bore.
With this device an elongate cavity can be cut in the bone chip, with the debris from the cutting entering the distal end of the internal bore and slowly pushing the piston up the bore away from the distal end. When the body portion is withdrawn from the cavity, the chips can then be easily dislodged from the bore by displacing the piston.
The body portion may include an aperture in the wall passing into the bore at a point spaced away from the distal end of the instrument to facilitate cleaning after operation. The action of the instrument when used by the surgeon can be back and forth or with a continuous rotation or with an up and down motion in the form of a pile driver.
Preferably an extension or extended portion of the piston projects beyond the proximal end of the body portion and a stop can be provided for limiting the movement of the piston up said bore and away from the distal end to a position adjacent the proximal end of the aperture.
Preferably the annular cutting rim is provided with cutting teeth although, in certain circumstances, merely a sharpened edge may be required.
The proximal end of the extended portion of the piston or an extension thereof can be provided with a removable stop to limit the movement of the piston in a distal direction. This stop can be removed so that the device can be completely dismantled for cleaning but when it is in position it locates the piston in the bore and prevents the piston dropping through the main body.
Preferably the hollow elongate body portion is provided with an operating handle which can be in the form of a T-piece.
The hollow elongate body portion can also be provided with a depth gauge and means such as a reference mark can be provided on the extended portion of the piston, or extension thereof, to provide a position indicator.
If desired the proximal end of the extended portion of the piston, or an extension thereof, can be provided with a coupling for attaching a power source so that the device can be operated by a power device.
The piston can be provided with a cannulation to accept a guide wire so that the trephine can be used as one of a series of operations when carrying out the preparation of the bone for implantation.


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