Patent Application
20210177614
The present disclosure relates generally to an implantable orthopaedic knee prosthesis, and more particularly to an implantable patella component of an orthopaedic knee prosthesis.
During the lifetime of a patient, it may be necessary to perform a joint replacement procedure on the patient as a result of, for example, disease or trauma. The joint replacement procedure may involve the use of a prosthesis which is implanted into one or more of the patient's bones. In the case of a patella replacement procedure, an orthopaedic prosthesis is implanted into the patient's patella. Specifically, a prosthetic patella component is secured to the patient's natural patella such that its posterior surface articulates with a femoral component during extension and flexion of the knee.
A conventional dome patella component is embodied as a dome-shaped polymer bearing. Other types of patella components include conforming or anatomic bearings which are designed to conform with the bearing surfaces of the femur. Dome patella components allow for greater movement between the patella component and the femoral component of the knee prosthesis, whereas anatomic patella components are more constrained relative to the femoral component. Both types of patella components have clinical benefits to fit the needs of a given surgical procedure.
According to an aspect of the disclosure, an orthopaedic implant includes a patella component. The patella component has a solid-metal base that includes a posterior base surface having a number of pockets formed therein. Each of the pockets has an undercut formed therein. The solid-metal base also has an anterior base surface with a number of pegs extending outwardly therefrom. A porous-metal coating is disposed on the anterior base surface and the pegs of the solid-metal base. A polymer bearing is molded to the posterior base surface of the solid-metal base. The polymer bearing has a posterior bearing surface configured to articulate with a pair of femoral condyles of a femoral component.
In an embodiment, the polymer bearing is molded into the pockets of the solid-metal base.
Illustratively, a posterior end of each of the pockets is defined by an opening formed in the posterior base surface, with an anterior end of each of the pockets being defined by a base wall that is spaced apart anteriorly from the opening. The medial and lateral sides of the pockets are defined by a pair of sidewalls that extend from the opening to the base wall. The sidewalls have the undercuts formed therein.
In an embodiment, the surfaces of the sidewalls defining the undercut have rounded surfaces.
Illustratively, a number of adjacent pockets of the solid-metal base open into one another.
In an embodiment, the solid-metal base further includes a perimeter sidewall extending between the posterior base surface and the anterior base surface. The perimeter sidewall has a number of pockets formed therein, and each of the pockets formed in the perimeter sidewall has the porous-metal coating disposed therein.
Illustratively, the patella component may be embodied as a dome patella component or an anatomic patella component.
According to another aspect, an orthopaedic implant includes a patella component. The patella component includes a solid-metal base that has a posterior base surface having a number of pockets formed therein, and an anterior base surface that has a number of pegs extending outwardly therefrom. A posterior end of each of the pockets is defined by an opening formed in the posterior base surface, with an anterior end of each of the pockets being defined by base wall that is spaced apart anteriorly from the opening. The medial and lateral sides of the pockets are defined by a pair of sidewalls that extend from the opening to the base wall. A number of adjacent pockets open into one another. A porous-metal coating is disposed on the anterior base surface and the pegs of the solid-metal base. A polymer bearing is molded to the posterior base surface of the solid-metal base. The polymer bearing has a posterior bearing surface configured to articulate with a pair of femoral condyles of a femoral component.
In an embodiment, the polymer bearing is molded into the pockets of the solid-metal base.
In an embodiment, the surfaces of the sidewalls defining the undercut have rounded surfaces.
In an embodiment, the solid-metal base further includes a perimeter sidewall extending between the posterior base surface and the anterior base surface. The perimeter sidewall has a number of pockets formed therein, and each of the pockets formed in the perimeter sidewall has the porous-metal coating disposed therein.
Illustratively, the patella component may be embodied as a dome patella component or an anatomic patella component.
According to yet another aspect of the disclosure, a method of making a patella component includes disposing a porous-metal coating onto an anterior surface and a number of pegs of a solid-metal base. A polymer bearing is molded onto a posterior surface of the solid-metal base such that a portion of an anterior surface of the polymer bearing is disposed within a number of pockets formed in the posterior surface of the solid-metal base. A posterior surface of the polymer bearing forms a patella bearing surface that is configured to articulate with a pair of femoral condyles of a femoral component.
Illustratively, the porous-metal coating and the solid-metal base is 3D-printed as a monolithic metal component.
In an embodiment, a number of sidewalls defining the pockets of the solid-metal base have undercuts formed therein. The polymer bearing is molded onto the posterior surface of the solid-metal base such that a portion of the anterior surface of the polymer bearing is molded to the sidewalls defining the undercuts of the pockets.
The polymer bearing may be molded to include either a dome patella bearing surface or an anatomic patella bearing surface, both of which are configured to articulate with the pair of femoral condyles of the femoral component.
The detailed description particularly refers to the following figures, in which:
While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etcetera, may be used throughout the specification in reference to the orthopaedic implants or prostheses and surgical instruments described herein as well as in reference to the patient's natural anatomy. Such terms have well-understood meanings in both the study of anatomy and the field of orthopaedics. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well-understood meanings unless noted otherwise.
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The polymer bearing 12 of the dome patella component 10 is embodied as a monolithic polymer body constructed with a material that allows for smooth articulation between the patella component 10 and the femoral component (which is generally constructed with a biocompatible metal, such as a cobalt chrome alloy, although other materials, such as ceramics, may also be used). One such polymeric material is polyethylene such as ultrahigh molecular weight polyethylene (UHMWPE).
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In one example, the porous-metal coating 60 may be made of a porous material 62 as described in U.S. patent application Ser. No. 16/365,557, which was filed Mar. 26, 2019 and is assigned to the same assignee as the present disclosure, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein. Additive manufacturing processes can include, by way of example, powder bed fusion printing, such as melting and sintering, cold spray 3D printing, wire feed 3D printing, fused deposition 3D printing, extrusion 3D printing, liquid metal 3D printing, stereolithography 3D printing, binder jetting 3D printing, material jetting 3D printing, and the like.
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The porous material 62 is formed from a metal powder. Illustratively, the metal powders may include, but are not limited to, titanium, titanium alloys, stainless steel, cobalt chrome alloys, tantalum, or niobium powders. The porous-metal coating 60 has a porosity suitable to facilitate bony ingrowth into the dome patella component 10 when the anterior surface 22 and the pegs 24 of the solid-metal base 14 are implanted into the surgically-prepared posterior surface of the patient's patella.
In the illustrative embodiment described herein, the porous-metal coating 60 is additively manufactured directly onto the anterior surface 22 and the pegs 24, and into wall pockets 50, of the solid-metal base 14. In such an embodiment, the two structures—i.e., the solid-metal base 14 and the porous-metal coating 60—may be manufactured contemporaneously during a common additive manufacturing process. For example, the two structures may be manufactured contemporaneously in a single 3D printing operation that yields a common, monolithic metallic component including both structures. Alternatively, the porous-metal coating 60 could be manufactured as a separate component that is secured to the solid-metal base 14.
The polymer bearing 12 may be assembled to the solid-metal base 14 by use of a number of different techniques. One exemplary manner for doing so is by use of compression molding techniques. For example, the solid-metal base 14 and the material from which the polymer bearing 12 is to be made (e.g., UHMWPE) may be placed in a mold with one another. Thereafter, the components are compression molded to one another under process parameters which cause the material from which the polymer bearing 12 is made (e.g., UHMWPE) to be molten and mechanically secured to the solid-metal base 14 by the compression molding process. As described above, the molten polymer bearing 12 interdigitates with the pockets 30, 52 of the solid-metal base 14 when molded thereto. It should also be appreciated that the mold may be configured to not only mold the components to one another, but also form the posterior bearing surface 16 into the polymer bearing 12.
The starting materials (e.g., polymers such as polyethylene) for use in the molding process may be provided in a number of different forms. For example, each of the starting materials may be provided as a preform. What is meant herein by the term “preform” is an article that has been consolidated, such as by ram extrusion or compression molding of polymer resin particles, into rods, sheets, blocks, slabs, or the like. The term “preform” also includes a preform “puck” which may be prepared by intermediate machining of a commercially available preform. Polymer preforms such as polyethylene preforms may be provided in a number of different pre-treated or preconditioned variations. For example, crosslinked or non-crosslinked (e.g., irradiated or non-irradiated) preforms may be utilized. Such preforms may be treated to eliminate (e.g., re-melting or quenching) or stabilize (e.g., the addition of vitamin E as an antioxidant) any free radicals present therein. Alternatively, the preforms may not be treated in such a manner.
The starting materials (e.g., polymers and copolymers) may also be provided as powders. What is meant herein by the term “powder” is resin particles. Similarly to as described above in regard to preforms, powders may be provided in a number of different pre-treated or preconditioned variations. For example, crosslinked or non-crosslinked (e.g., irradiated or non-irradiated) powders may be utilized.
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While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.
There are a plurality of advantages of the present disclosure arising from the various features of the method, apparatus, and system described herein. It will be noted that alternative embodiments of the method, apparatus, and system of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the method, apparatus, and system that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present disclosure as defined by the appended claims.
