Surgery – Instruments – Orthopedic instrumentation
Utility Patent
1999-08-20
2001-01-02
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S08600R, C623S022210
Utility Patent
active
06168600
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to acetabular reamer backing plates. In particular, the present invention relates to the design and use of backing plates for acetabular reamers that allow for the attachment of a driver and openings for allowing the surgeon to observe the bone cuttings within the cutting cup and make cleaning of the bone cuttings from the cup easier.
2. Description of the Prior Art
Acetabular reamers are surgical cutting tools used primarily to cut into bone for the implantation of joint prostheses. The most common use of an acetabular reamer is to replace the hip joint, wherein the greater trochanter of a femur and the acetabulum are replaced with a ball and socket-type of protheses, respectively. In order to perform such operations as to replace the hip joint, the surgeon must ream a portion of the bone and other tissue from the acetabulum to allow placement of the prosthetic socket. The reaming of the bone is accomplished by use of an acetabular reamer assembly.
The acetabular reamer assembly is composed of a cutting cup and a backing plate. A driver is then inserted into the backing plate to turn the cutting cup. The driver is in turn mounted in the chuck of a portable drill or flexible powered shaft. The tissue in the joint to be replaced is cut by rotating the cutting cup within the joint. A plurality of cutting edges are located along the outside surface of the cutting cup. Typically, the cutting edges extend through the cup and allow for cut tissue to fall and collect within the interior of the cup. Several prior art patents disclose methods of making acetabular cutting cups, including U.S. Pat. Nos. 5,709,688, 5,302,234, 5,116,165, and 5,100,267.
One problem with presently used acetabular reamers is the design of the backing plates. The backing plate is used to form the mechanical coupling between the reamer driver, which is typically a shaft that extends to an electric drill at one end and the cutting cup at the other. Once the plate is in place on the cutting cup and the driver is inserted into a hole in the plate, a closed cavity is typically formed wherein no spaces are left for bone and tissue fragments to escape. Thus, in most acetabular reamers, in order for the surgeon to judge the cutting progress and to remove excess tissue, the driver must be removed from the cutting tool, and often the backing itself. Removing the driver typically means that the surgeon must stop the procedure. This is a disadvantage in surgical procedures as it adds time and the possibility of imprecision.
At the same time, it is critical that the backing plate fit the driver snugly. This is important because acetabular reamers must be capable of producing cavities with very close tolerances. The cutting cups have precise dimensions and are light in weight and must fit on an appropriate tool driver with a minimum of free play and must be quick and easy to install and remove without tools. Although one backing plate has been shown in U.S. Pat. No. 5,709,688 to have small debris openings, these have the drawback of being relatively small and thus do not allow for easy removal of debris from within the cup interior. Further, this prior art backing plate has a number of independent openings, each requiring a separate starting hole in the machining process to form the backing plate. Thus, there is a need for a backing plate on an acetabular reamer cup with an opening or openings which allow greater physical and visual access to the interior of the cup while simplifying the machining operation in the manufacture of the plate. The present invention is directed towards such a need.
SUMMARY OF THE INVENTION
The present invention is an improvement in acetabular reamer assemblies, and in particular discloses an improved backing plate that allows for high tolerances in cutting, while also allowing the surgeon to visually inspect the bone fragments being cut, and to allow for easy removal of bone fragments without having to remove the driver.
The present invention is a backing plate for an acetabular reamer assembly that allows for the attachment of a reamer driver. The acetabular reamer assembly comprises a cutting cup and backing plate, the cutting cup having an external surface with cutting teeth formed therein and having an internal surface, the cutting cup terminating in a peripheral edge. The rigid backing plate has a planar surface which terminates in an outer circumferential edge, the outer circumferential edge being coupled to the peripheral bottom edge of the cutting cup, the rigid plate also having an internal edge profile. The internal edge profile of the rigid backing plate has at least two finger elements protruding from the outer circumferential edge thereof towards a central vertical axis drawn perpendicular to the planar surface of the plate. Further, the finger elements of the backing plate form a holding opening for a reamer driver.
The internal edge profile of the backing plate forms at least one observation opening in addition to the holding opening to allow bone fragments forming within the acetabular reamer to be visually inspected while the reamer is in use. The finger elements terminate to form a contact surface to make firm contact with the driver when inserted in the holding opening. The contact surface can be simple or complex. Further, the internal edge profile is continuous so that the machining process for the backing plate is simplified.
Thus, one object of the present invention is to provide a backing plate that allows the medical practitioner more control in reaming bone and other tissue from a patient's joint.
Another object of the present invention is to provide the medical practitioner an improved observation opening for visually inspecting the progress of the reaming procedure.
Yet another object of the present invention is to provide a backing plate that can be machined in fewer steps, thus simplifying the machining of the backing plate and making it less expensive.
Yet another object of the present invention is to provide a backing plate that allows for easy removal of bone fragments within the cavity of the cutting cup.
Yet another object of the present invention is to provide a backing plate that reduces the compaction of bone fragments and other tissues within the cavity formed by the reamer cup and backing plate, thus improving the cutting ability of the cutting edges of the cup.
The features and elements of the present invention will accomplish these objects. Additional objects, features and advantages will be apparent in the written description which follows.
REFERENCES:
patent: 4296822 (1981-10-01), Ormsbuy
patent: 5100267 (1992-03-01), Salyer
patent: 5116165 (1992-05-01), Salyer
patent: 5171243 (1992-12-01), Kashuba et al.
patent: 5302234 (1994-04-01), Grace et al.
patent: 5462548 (1995-10-01), Pappas et al.
patent: 5658290 (1997-08-01), Lechot
patent: 5709688 (1998-01-01), Salyer
Duerr Dan
Grace Jeff
Grace Richard L.
Faulkner Kevin M.
Grace Manufacturing Inc.
Gunter, Jr. Charles D.
Philogene Pedro
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