Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-06-21
2001-05-08
Smith, Jeffrey A. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S022350, C623S022240
Reexamination Certificate
active
06228121
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable.
FIELD OF THE INVENTION
The present invention relates generally to prosthetic components, and more particularly, to prosthetic joints.
BACKGROUND OF THE INVENTION
Joint arthroplasty is a well known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. Joint arthroplasty is commonly performed for hips, knees, elbows, and other joints. The health and condition of the joint to be replaced dictate the type of prosthesis necessary to replace the natural joint. For example, in a total hip arthroplasty an acetabular cup may be implanted in the pelvis to replace the natural acetabulum.
To implant an acetabular cup, an acetabular cavity is reamed in the acetabulum. The reamed cavity generally conforms to an outer surface of the acetabular cup. The acetabular cup is then inserted into the formed cavity and is then further secured by mechanical means, such as one or more fixation screws. The acetabular cup is positioned in the pelvis at a relatively fixed orientation with respect to patient anatomy and should remain stable.
FIGS. 1-4
show one type of prior art acetabular cup
10
implanted in a patient's acetabulum
12
. The cup
10
includes a hemispherical outer member
14
for interfacing to bone and a mating inner member
16
for providing an articulation surface for the ball
18
of a femoral component
20
. The inner member
16
is formed from polyethylene, for example, to provide a durable, low friction interface for allowing the femoral component to move freely. Apertures
22
are formed in the outer member
14
of the cup to provide passageways for fixation screws
24
that secure the acetabular cup
10
to the bone.
While the apertures allow the fixation screws to penetrate bone, the screws must be inserted at locations corresponding to the apertures. In addition, the fixations screws must be introduced into the bone within a limited angular range to allow proper seating of the screw head in the aperture.
Further, while the implanted cup may initially be secured in position, movement of the implanted acetabular cup over time can contribute to erosion of the surrounding bone. One effect of such bone erosion is the loosening of the acetabular cup, allowing it to shift in position. More particularly, the implanted cup tends to subside into the surrounding bone so as to adversely affect conditions in the prosthetic joint. Typically, an implanted acetabular cup will subside several millimeters within a few years after implantation, which can result in one or more fixation screw impinging on the cup liner. Screw/liner contact can cause fretting of the liner and possibly catastrophic failure of the liner.
For example, as shown in the prior art prosthetic hip joint of
FIG. 4
, as the cup
10
subsides into the surrounding bone a head
26
of the fixation screw
24
begins to impinge upon the polyethylene inner cup member
16
. The action of the screw
24
against the polyethylene inner member
16
as the joint is subjected to loads may cause wear debris to develop, which can ultimately result in osteolysis within the joint. In extreme cases, the screw
24
can fracture the inner member
16
causing catastrophic failure of the joint.
It would, therefore, be desirable to provide an implantable prosthesis system having features to optimize the positioning of fixation screws into bone, to minimize the effects of implant subsidence into the surrounding bone, and to increase safety margins.
SUMMARY OF THE INVENTION
The present invention provides a prosthetic joint system that enhances the long term fixation properties of the implant by providing a structure to allow fixation screws to be inserted at a range of angles and to accommodate subsidence of the prosthesis into bone. Although, the invention is primarily shown and described as an acetabular cup implantation system, it is understood that the invention has other applications as well, such as for use with prosthetic knee systems.
In one embodiment, an implantable prosthesis system includes an acetabular cup having a convex outer component for interfacing with bone and an inner component that is matable with the outer component to provide an articulation surface for a corresponding femoral component. The acetabular cup includes at least one aperture to provide a passageway for a fixation element, such as a screw, to secure the cup to bone. A plurality of sleeve components are provided to mate with the apertures formed in the outer component. Each sleeve is of a substantially elongate shape having an outer surface and a longitudinal bore extending therethrough from a proximal opening to a distal opening in the sleeve. The longitudinal bore is adapted to receive a fixation element, e.g., a bone screw, such that a head of the screw seats within the sleeve adjacent the distal opening of the sleeve. Each sleeve is adapted to mate with one of the apertures such that the distal opening of the sleeve is spaced away from an outer surface of the acetabular cup.
The sleeve component can be positioned at a range of angles with respect a central axis of an aperture of the acetabular cup with which it is mated, thus allowing the fixation screws to be inserted into a desired region of bone. In addition, the sleeve compensates for subsidence of the implanted acetabular cup by providing a region to accommodate longitudinal movement of the fixation screw to prevent the screw head from contacting, and thereby possible damaging, the inner cup component.
To implant the acetabular cup system, an acetabular cavity is formed in the patient's acetabulum and the prosthetic cup component is inserted into the formed cavity. The surgeon then drills one or more holes in the bone via the apertures in the cup outer surface at predetermined angles to optimize fixation of the cup to bone by way of the screws. The formed holes are then used to align a larger diameter drill for enlarging a portion of the holes to receive the sleeve components. The sleeve components are engaged with respective fixation screws, which are then rotated into the holes formed in the bone to secure the acetabular cup to the acetabulum.
REFERENCES:
patent: 4840632 (1989-06-01), Kampner
patent: 4881532 (1989-11-01), Borig et al.
patent: 4888022 (1989-12-01), Huebsch
patent: 4892550 (1990-01-01), Huebsch
patent: 5002578 (1991-03-01), Luman
patent: 5021062 (1991-06-01), Adrey et al.
patent: 5211666 (1993-05-01), Fetto
patent: 5259249 (1993-11-01), Fetto
patent: 5417696 (1995-05-01), Kashuba et al.
patent: 5534032 (1996-07-01), Hodorek
patent: 5540697 (1996-07-01), Rehmann et al.
patent: 5571193 (1996-11-01), Kampner
patent: 5580352 (1996-12-01), Sekel
patent: 5584837 (1996-12-01), Petersen
patent: 5725588 (1998-03-01), Errico et al.
patent: 5733338 (1998-03-01), Kampner
patent: 5791899 (1998-08-01), Sachdeva et al.
patent: 0341199 (1989-11-01), None
patent: 2685192 (1993-06-01), None
Depuy Othopedics, Inc.
Nutter & McClennen & Fish LLP
Smith Jeffrey A.
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