Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-11-15
2002-11-05
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C404S054000, C404S062000
Reexamination Certificate
active
06475221
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to surgical devices, and more particularly concerns a rotatable surgical cutting tool for shaping a joint socket in preparation for receiving a joint prosthetic device.
BACKGROUND
It is now common practice in the treatment of severe cases of arthritic and other forms of degenerative joint diseases, especially the hip, to shape the hip joint socket by removing diseased and eroded bone and cartilage to conform with the shape of a prosthetic device to be implanted. Prior to installing a hip joint prosthesis, for example, articular cartilage and bone is commonly removed from the socket to reshape the acetabulum to accurately match the dimensions of the prosthetic device to be implanted. In the past, the tissue and debris removed from the hip socket was discarded; however, more recently, it has become important to capture the debris for preservation and use later in the procedure.
It is generally desirable for milling devices and reamers used in preparing a joint socket for a prosthesis to have cutting edges that can cut through a wide variety of tissue, such as joint cartilage and bone tissue, ranging in density from the soft or porous tissue to the denser bone. The surgical tools with hollow cutting heads are more widely used than other more open designs, because hollow head devices allow tissue and other debris to be captured within the cutting head.
Two distinct types of hollow dome cutting tools are currently available that capture the debris. One type employs a slotted dome with adjacent blades that are shaped to generate a socket, when rotated, conforming to the shape and dimensions of the prosthesis to be implanted. The debris cut by the blades falls through slots in the dome.
In another type of surgical milling tool, commonly called a “grater” reamer, the milling cutters are formed on the body by upsetting the body around openings in the body, and sharpening selected edges of the upset portions of the body. The surgical milling tool has a body with a hemispherically-shaped outer surface, an internal cavity, and milling cutters formed out of the perforations in the body at spaced-apart locations on the outer surface. The tool can be rotated in a joint socket to mill the tissues of the joint socket, such as for preparation of the joint socket for a prosthesis. The perforations in the body communicate with the internal cavity which receives the debris. The milling cutters of the milling tool are formed as cup-shaped projections extending above the perforations that face in a direction of rotation, and are arranged in a series of arcs extending circumferentially around the body. The outer wall of the milling tool forming the cup-shaped cutting edge projections is relatively thin, resulting in reduced cutting accuracy. The milling tool and cutting edge projections are formed of sheet steel, which can become dull relatively rapidly during use. Typically, if the cutting surfaces are formed integrally with the shell, such as with raised cutting edges formed directly in the shell, the manufacturing of the devices becomes very costly. In addition, once the projections forming the cutting edges of the milling tool are dull, the entire milling tool is typically discarded.
An example of a grater type of reamer is shown in U.S. Pat. No. 5,658,290 to Lechot, which further provides radial rods on the underside of the reamer cap that join up at the center of the cap and are integral. A reamer spindle has a shank with a head equipped with a bayonet having a locking mechanism for securing the reamer. The center of the bayonet is recessed to receive the radial rods and serve as a cavity for debris.
It would be desirable to provide a reaming tool fabricated from heat treated machined metal components to provide greater cutting accuracy, and at lower manufacturing costs than conventional surgical cutters. In this regard it would be desirable to form the cutters of a hardened cutting material to provide superior cutting edges. In addition, it would be desirable to provide a reaming tool with replaceable cutting edges, so that once the cutting edges become dull, they can be removed, resharpened, and replaced, for improved economy of use and maintenance. The present invention meets these needs.
It would be further desirable to provide a reaming tool that not only captures debris passing through the teeth, but one that also allows easier removal and use of the debris collected within the tool, versus currently available tools. The present invention is also an improved means for meeting this need.
SUMMARY OF THE INVENTION
Briefly, and in general terms, the present invention provides for an improved reaming tool that is fabricated from machined metal components to provide greater cutting accuracy, and at lower manufacturing costs than conventional cutters. The reaming tool has a multiplicity of cutters that can be formed of heat treated tool steel, to provide superior cutting edges. In addition, once the individual cutters become dull, they can readily be removed, replaced, and can even be resharpened and used again, for improved economy of use and maintenance.
The present invention accordingly provides for a rotary surgical reamer for removing bone and tissue from a joint to facilitate the installation of a prosthetic device. The rotary surgical reamer comprises a hollow reamer body, the hollow reamer body having a base portion, a wall with a surface defining a central cavity and a plurality of spaced apart apertures through the wall at a plurality of spaced apart locations on the wall defining cutting sites. Means are provided for connecting the hollow reamer body to a source of rotary power, and a plurality of teeth are removably disposed in the apertures. Each of the teeth have a tooth body having a base portion and a raised cutting edge, and the tooth body includes means for holding the tooth in a fixed position at one of the cutting sites. The tooth body also has a surface defining a passageway communicating between the external surface of the wall and the central cavity for passage of removed bone and tissue through the wall into the central cavity. In a currently preferred embodiment, the tooth body includes a flange for spacing the cutting edge a desired distance beyond the external surface of the wall of the reamer body. In one presently preferred embodiment, the teeth have a generally tubular shape.
The hollow reamer body preferably has a shape with a central axis of rotation about which perpendicular cross-sectional cutting patterns are generated during rotation of the hollow reamer body, allowing the hollow reamer body to be rotated without wobbling. In one presently preferred embodiment, the external surface of the hollow reamer body has a three-dimensional contour that is generally hemispherical, although the hollow reamer body may also have a three-dimensional contour selected from the group consisting of generally spherical, oblate spheroid, generally cylindrical, generally polygonal, or combinations thereof. Means for connecting the hollow reamer body to a source of rotary power is carried on the base portion of the hollow reamer body.
In one presently preferred embodiment, the external surface of the hollow reamer body has a three-dimensional contour having an apex, and the plurality of cutting sites are spaced apart in an arcuate array extending from a site adjacent the apex toward the base portion of the hollow reamer body, forming a helical pattern. In another presently preferred embodiment, the cutting sites are arranged in a plurality of arcs extending from a site adjacent to an apex of the hollow reamer body to the base portion.
In another preferred aspect of the invention, the rotary surgical reamer includes closure means adapted to be secured to the base portion of the hollow reamer body. In a presently preferred embodiment, the closure means comprises a base plate removably disposed on the base portion of the hollow reamer body and means for securing the base plate to the base portion of the hollow reamer body for closure o
Fishbein Meyer
White Patrick M.
Chiatalas John L.
Philogene Pedro
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