Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1998-03-30
2001-01-09
Isabella, David J. (Department: 3308)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S020340, C623S020320
Reexamination Certificate
active
06171342
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to joint prostheses, and more particularly to modular knee joint prostheses employed during knee arthroplasty procedures.
BACKGROUND OF THE INVENTION
Knee arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural knee joint is replaced by a prosthetic knee joint. Typical knee prostheses include a tibial component, a femoral component, and a patellar component. The femoral component generally includes a pair of spaced apart condylar portions, the superior surfaces of which articulate with a portion of the tibial component. A femoral stem assembly, used to provide lateral stability to the replaced knee joint, seats within the medullary canal of a distal portion of a femur, and is typically coupled to the femoral component by specialized coupling devices, such as a collar and bolt. Some prosthetic knee joints include a structure known as a Morse taper post that extends from the inferior surface of the femoral component to mate with a femoral sleeve that is securable to the femoral stem assembly.
The femoral sleeve, which helps to fill spaces at the opening of the medullary canal, can also provide for a modular assembly allowing a surgeon to select the most appropriate femoral stem from a selection of stems having different lengths and diameters for attachment to one of a selection of femoral components. This modular configuration significantly reduces the number of individual components that must be purchased, stocked, and used during a surgical procedure. Although the femoral stem, whatever its dimensions, is usually angled laterally with respect to the inferior surface of the femoral component and either off-set anteriorially/posterially or at a central location, it is sometimes desirable to orient the femoral stem perpendicularly with respect to the inferior surface. For example, depending on particular patient requirements, the femoral stem may need to be offset fore or aft with respect to the front of the femoral component. Similarly, the femoral stem may need to be angled varying degrees to the left or right with respect to the front of the femoral component. The Morse taper post, however, is integrally cast as a unitary and indivisible portion of the femoral component. Furthermore, there is a requirement for a range of sizes of the overall femoral component. Therefore, in order to accommodate all of the possible combinations of overall femoral component size, fore
eutral/aft positioning of the Morse taper post, and left/perpendicular/right angling of the Morse taper post, a doctor or hospital is required to maintain an undesirably substantial stock of knee prosthesis components.
Despite the existence of knee joint prostheses having modular components, there remains a need for a modular knee joint prosthesis that has greater versatility to accommodate differing patient anatomy and joint conditions. It is thus an object of the invention to provide a modular knee prosthesis having greater versatility to accommodate different patient anatomy and joint conditions while maintaining a relatively low component count. It is another object of the invention to provide a modular knee prosthesis having components that are physiologically and geometrically compatible with different anatomical conditions. Still another object of the invention is to provide a modular knee prosthesis that is suitable for use in both right and left knee procedures. Other general and more specific objects of the invention will in part be apparent from the drawings and description that follow.
SUMMARY OF THE INVENTION
The present invention relates to a versatile modular knee joint prosthesis system that offers numerous options for femoral component fixation and stability while reducing the overall component count. Components of the modular prosthesis of the invention are able to be used with both right and left side prostheses to provide angled, non-angled, offset and non-offset orientation of femoral stem components. Moreover, the system of the invention provides various options for attaching prosthesis components, such as metaphyseal augments and femoral stems, to the femoral prosthesis component.
In an exemplary embodiment of the invention, a modular knee prosthesis includes a femoral component, a bolt, and a Morse taper post. The femoral component has a superior surface, an inferior surface, and an aperture extending therebetween. The bolt includes a head portion engagable with the superior surface of the femoral component to inhibit movement of the bolt through the femoral component, and an elongate shaft portion that extends from the head portion of the bolt. The elongate shaft portion has a length sufficient to protrude through the aperture beyond the inferior surface of the femoral component. The Morse taper post is engagable with the elongate shaft portion of the bolt to retain the Morse taper post in a fixed position with respect to the femoral component and the distal end of the Morse taper post is introducible within a femoral sleeve.
The modular knee prosthesis can further include a collar interposable between the Morse taper post and the inferior surface of the femoral component. The collar can position the elongate shaft portion of the bolt or the Morse taper post orthogonally or at an angle, in the medial or lateral directions, with respect to the inferior surface of the femoral component.
Additionally, the aperture of the femoral component can be configured to allow the shaft portion of the bolt to be extended through the aperture at a predetermined angle with respect to the inferior surface of the femoral component and be held at the predetermined angle by a collar. The aperture and the bolt are cooperatively configured to position the Morse taper post fore and aft with respect to a central reference location.
In another embodiment of the invention, a modular knee fastening system for a modular knee prosthesis includes a washer engagable with a bolt and a femoral component so that a portion of the bolt shaft protrudes through an aperture in the washer and an aperture in the femoral component. The washer can include an aperture that is in the center of the washer, off-center, or lobed to permit selective placement of the bolt with respect to the femoral component.
In yet another embodiment of the invention, a medical fastening system for a modular knee prosthesis includes a femoral component having an aperture. A washer having an aperture alignable with at least a portion of the aperture in the femoral component engages the femoral component to inhibit movement of the washer through the aperture in the femoral component. A bolt engages the washer and an elongate shaft portion of the bolt protrudes from the femoral component through the aperture in the washer and the aperture in the femoral component to engage a Morse taper post or femoral stem. The configuration of the washer aperture, its location in the washer, and the orientation of the washer within the femoral component determine the fore and aft positioning of the Morse taper post or femoral stem. The Morse taper post or femoral stem can be provided with a canted base to angle the post or stem with respect to the femoral component.
In a further embodiment, the knee prosthesis system of the invention includes a first prosthesis component (e.g., a femoral component of a knee joint prosthesis), which has a first surface, a second surface, and an aperture extending between the two surfaces. A modular adapter element has a first end that is mountable adjacent the first surface of the first prosthesis component and a second, mating end that is engagable with a second prosthesis component. The first end of the modular adapter element includes a bore that extends therein. The system also includes a first bolt having a head portion engagable with the second surface of the prosthesis component to prevent the bolt from passing through the first prosthesis component. An elongate shaft, which has a length sufficient to protrude through the aperture and into the bore of
Birla Amit
Cipolletti George B.
Colleran Dennis P.
Gabriel Stefan M.
Jones Richard E.
DePuy Orthopaedics, Inc.
Isabella David J.
Nutter & McClennen & Fish LLP
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