Tibial component with flexible rim

A tibial prosthesis including an articulating component and a tray component with a rim that extends proximally to support the articulating component, the tray component enabling flexion of the rim relative to a bone-contacting surface of the tray component.

BACKGROUND

1. Field of the Invention

The present invention relates to the field of orthopedics. More particularly, the present invention relates to a tibial prosthesis, and to a method for using the same.

2. Description of the Related Art

Orthopedic prostheses are commonly used to repair and replace damaged bone and tissue in the human body. For example, to repair damaged bone of the knee joint and to recreate the natural, anatomical articulation of the knee joint, a tibial prosthesis may be implanted in the proximal tibia and/or a femoral prosthesis may be implanted in the distal femur.

The tibial prosthesis may include a first, articulating component having a concave articulating surface configured for articulation against a natural femur or a femoral prosthesis. The tibial prosthesis may also include a second, tray component having a bone-contacting surface configured for securing the tibial prosthesis to the bone stock of a resected proximal tibia. The articulating component may be made from a polymer to facilitate articulation with the adjacent femoral prosthesis, while the tray component may be made from a metal to provide additional strength and rigidity to the tibial prosthesis.

SUMMARY

The present invention provides a tibial prosthesis a tibial prosthesis including an articulating component and a tray component with a lip that extends proximally to support the articulating component, the tray component enabling flexion of the lip relative to a bone-contacting surface of the tray component.

According to an embodiment of the present invention, a tibial prosthesis is provided that is configured for securement to a patient's tibia and for articulation with an adjacent femoral component. The tibial prosthesis includes an articulating component and a tray component. The articulating component includes a concave articulating surface to facilitate articulation with the femoral component. The tray component includes a proximal, receiving surface that receives the articulating component, a distal, bone-contacting surface opposite the receiving surface that is configured for securement to the patient's tibia, and an outer surface that extends proximally from the bone-contacting surface and beyond the receiving surface to define a rim for supporting the articulating component, the outer surface of the tray component defining a notch positioned to permit flexion of the rim relative to the bone-contacting surface of the tray component.

According to another embodiment of the present invention, a tibial prosthesis is provided that is configured for securement to a patient's tibia and for articulation with an adjacent femoral component. The tibial prosthesis includes an articulating component and a tray component. The articulating component has a concave articulating surface to facilitate articulation with the femoral component. The tray component has a proximal, receiving surface that receives the articulating component and a distal, bone-contacting surface opposite the receiving surface that is configured for securement to the patient's tibia, the tray component including a rim that extends proximally beyond the receiving surface to support the articulating component, the rim defining a notch that extends into the rim until reaching an inflection point, the inflection point located along an arcuate surface of the rim to permit flexion of the rim relative to the bone-contacting surface of the tray component at the inflection point.

According to yet another embodiment of the present invention, a method is provided for implanting a tibial prosthesis onto a patient's tibia. The method includes the steps of: providing the tibial prosthesis including an articulating component and a tray component, the tray component having a proximal, receiving surface that receives the articulating component, a bone-contacting surface, and a peripheral rim that supports the articulating component, the peripheral rim having an inner surface that faces the articulating component and an outer surface that defines a notch; and securing the tibial prosthesis to the patient's tibia with the bone-contacting surface of the tibial prosthesis facing the patient's tibia, the notch permitting flexion of the rim relative to the patient's tibia.

DETAILED DESCRIPTION

Referring toFIG. 1, an exemplary tibial prosthesis10is shown implanted onto a resected proximal tibia T. Tibial prosthesis10includes a first, articulating component20mounted atop a second, tray component30. Tibia T includes a longitudinal axis A.

As shown inFIG. 1, articulating component20of tibial prosthesis10includes at least one concave articulating surface22configured for articulation against a natural femur (not shown) or a femoral prosthesis (not shown). To facilitate articulation with an adjacent femoral component, articulating component20of tibial prosthesis10may be constructed of a smooth, abrasion-resistant material. Also, to provide cushioning to the knee joint, articulating component20of tibial prosthesis10may be constructed of a resilient, deformable material. For example, articulating component20may be constructed of a biocompatible polymer, including, but not limited to, a hydrogel, poly ether ether ketone, fiber reinforced poly ether ether ketone, ultrahigh molecular weight polyethylene, crosslinked ultrahigh molecular weight polyethylene, or polyether ketone ether ether ketone. It is also within the scope of the present invention that articulating component20may be constructed of a more rigid material like a biocompatible ceramic. Suitable ceramics include oxide ceramics, such as alumina or zirconia, and non-oxide ceramics, such as silicon nitride or silicon carbide.

To provide strength and rigidity to tibial prosthesis10, tray component30may be constructed of a rigid biocompatible ceramic or metal. For example, tray component30may be constructed of titanium, a titanium alloy, a zirconium alloy, tantalum, cobalt chromium, cobalt chromium molybdenum, porous tantalum, or a highly porous biomaterial. A highly porous biomaterial is useful as a bone substitute and as cell and tissue receptive material. An example of such a material is produced using Trabecular Metal™ technology generally available from Zimmer, Inc., of Warsaw, Ind. Trabecular Metal™ is a trademark of Zimmer, Inc. Such a material may be formed from a reticulated vitreous carbon foam substrate which is infiltrated and coated with a biocompatible metal, such as tantalum, by a chemical vapor deposition (“CVD”) process in the manner disclosed in detail in U.S. Pat. No. 5,282,861, the disclosure of which is expressly incorporated herein by reference.

As shown inFIG. 2, receiving surface32of tray component30is configured to receive and mate with articulating component20(FIG. 1). Peripheral wall36of tray component30extends proximally beyond receiving surface32to define an outer rim or lip38. Receiving surface32and rim38of tray component30cooperate to define chamber40. According to an exemplary embodiment of the present invention, when articulating component20is received within chamber40of tray component30, as shown inFIG. 1, articulating component20rests against receiving surface32of tray component30and is supported externally by rim38of tray component30.

Articulating component20may be attached to tray component30via an interference fit, with a mechanical fastener, or with an adhesive, for example. Also, some or all portions of rim38may include flange39that projects inwardly into chamber40. In this embodiment, and as shown inFIG. 3, articulating component20may include groove24that is sized to receive flange39of rim38in a tongue and groove arrangement to prevent articulating component20from lifting off of tray component30.

Bone-contacting surface34of tray component30is configured for attachment to the bone stock of a resected proximal tibia T. An exemplary attachment method involves using a layer of adhesive44, such as bone cement, which may not only provide a secure connection between tray component30and tibia T, but may also strengthen tibia T. Adhesive layer44may include any known medical grade adhesive having sufficient strength to secure tray component30to tibia T, including, but not limited to, light curable acrylic adhesives, acrylic adhesives, cyanoacrylate adhesives, silicone adhesives, urethane adhesives, epoxy adhesives, and bone cement.

To stabilize tray component30and to prevent rotation of tray component30, tray component30may include at least one anchor (not shown), such as a stem or a keel, that extends distally from bone-contacting surface34and into the intramedullary canal of tibia T. The intramedullary canal of tibia T may be filled with adhesive to hold the anchor in place. Also, tray component30may include pockets (not shown) recessed into bone-contacting surface34for receiving adhesive layer44between tray component30and tibia T.

According to an exemplary embodiment of the present invention, rim38of tray component30includes notch50. As shown inFIG. 3, notch50extends radially inwardly into peripheral wall36to narrow tray component30along notch50. In an exemplary embodiment, notch50extends inwardly through a majority of the width of rim38. Notch50may extend entirely or substantially entirely about peripheral wall36of tray component30. Notch50may extend into peripheral wall36of tray component30proximally beyond receiving surface32, such that notch50extends into rim38of tray component30. Also, notch50may extend into peripheral wall36of tray component30between receiving surface32and bone-contacting surface34, such that notch50extends beneath rim38of tray component30. In an exemplary embodiment, notch50spans a majority of the height of tray component30. In use, notch50of tray component30may remain open and unfilled.

In the illustrated embodiment ofFIG. 3, notch50is bordered distally by first chamfered portion52of peripheral wall36and is bordered proximally by second chamfered portion54of peripheral wall36. Between first chamfered portion52and second chamfered portion54, peripheral wall36includes an inner-most inflection point56. According to an exemplary embodiment of the present invention, peripheral wall36is arcuate in shape along inflection point56. It is within the scope of the present invention that first chamfered portion52and second chamfered portion54of peripheral wall36may be linear or arcuate in shape.

With bone-contacting surface34of tray component30seated against the resected proximal tibia T, first chamfered portion52of peripheral wall36extends inwardly toward longitudinal axis A at first acute angle α, and second chamfered portion54of peripheral wall36extends inwardly toward longitudinal axis A at second acute angle β. First acute angle α and second acute angle β may equal approximately 20°, 30°, 40°, 50°, 60°, or 70°, for example. First acute angle α and second acute angle β may be substantially the same, or first acute angle α may differ from second acute angle β.

As shown inFIG. 3, first chamfer portion52of peripheral wall36terminates distally upon reaching outer edge42of bone-contacting surface34. However, it is within the scope of the present invention that first chamfer portion52of peripheral wall36may terminate distally before reaching outer edge42of bone-contacting surface34, with peripheral wall36continuing distally in a vertical direction to meet outer edge42of bone-contacting surface34. Also, second chamfer portion54of peripheral wall36is shown terminating proximally before reaching top end37of rim38, with peripheral wall36continuing proximally in a vertical direction to meet top end37of rim38. However, it is within the scope of the present invention that second chamfer portion54of peripheral wall36may terminate proximally upon reaching top end37of rim38.

By providing notch50, tray component30may be constructed of less material than a solid tray component30lacking notch50. Advantageously, this material reduction may be achieved without reducing the surface area of receiving surface32, the surface area of bone-contacting surface34, the thickness of tray component30from receiving surface32to bone-contacting surface34, and/or the height of rim38. For example, as shown inFIG. 3, the location of notch50does not interfere with the surface area of bone-contacting surface34, so outer edge42of bone-contacting surface34defines an outer-most perimeter of tray component30that fully spans across the patient's tibia T.

As a result of this material reduction, tray component30may be more flexible along notch50than a solid tray component30lacking notch50, such that tray component30is able to bend or flex along notch50. For example, rim38of tray component30may be able to bend or flex along notch50relative to bone-contacting surface34of tray component30. By providing notch50with an arcuate peripheral wall36along inflection point56, flexion may be encouraged at inflection point56while limiting stress concentrations at inflection point56. Advantageously, this flexibility may be achieved without altering the rigidity of tray component30itself. For example, tray component30may still be constructed of a rigid metal such as titanium, a titanium alloy, a zirconium alloy, tantalum, cobalt chromium, or cobalt chromium molybdenum to provide strength and rigidity to tibial prosthesis10while achieving flexibility along notch50.

The present inventors have recognized that traction forces and pulsing forces on tibial prosthesis10reach a maximum level along peripheral wall36and rim38of tray component30. Due to these high forces along peripheral wall36and rim38of tray component30, the present inventors have observed from X-rays that implanted tray components30begin detaching from the bone stock of tibia T and adhesive layer44along the adjacent outer edge42of bone-contacting surface34. By providing tray component30having notch50, these anatomical forces may tend to flex tray component30along notch50. For example, these anatomical forces may tend to flex rim38of tray component30along notch50. When acting on a more rigid rim38without notch50, these anatomical forces would be focused between tray component30and adhesive layer44, especially along outer edge42of bone-contacting surface34of tray component30. Thus, by providing notch50in tray component30, the anatomical forces on outer edge42of bone-contacting surface34may be diminished to prevent tray component30from separating from tibia T.