Patent Description:
Orthopaedic implants are known that include one or more porous regions to facilitate and encourage tissue ingrowth to fixate the implant once implanted in a subject. Including such porous regions improves fixation of the implant to reduce the risk of the implant coming loose and failing. While such implants are effective, economically producing the implants with the porous regions is difficult due to the need to preserve the pores while also stably coupling the porous regions to, for example, a base that has a higher material strength and can endure the load exerted on the implant following implantation.

What is needed in the art is an economical way to produce an orthopaedic implant that includes one or more porous material regions.

Exemplary embodiments disclosed herein provide patellofemoral implants that have porous ingrowth material on one or more surfaces of the implant and methods to manufacture such implants.

One possible advantage that may be realized by exemplary embodiments disclosed herein is that the porous ingrowth material regions can be coupled to a molded base without filling some of the pores of the ingrowth material regions to provide pores for tissue ingrowth.

Another possible advantage that may be realized by exemplary embodiments disclosed herein is that the implants can be produced by, for example, compression molding in an economical fashion.

Yet another possible advantage that may be realized by exemplary embodiments disclosed herein is that the implants can be formed in a variety of shapes for use in different surgical techniques.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

Referring now to the drawings, and more particularly to <FIG>, an exemplary embodiment of a patellofemoral implant <NUM> is illustrated that generally includes a base <NUM>, a first porous ingrowth material region <NUM> coupled to the base <NUM>, and a second ingrowth material region <NUM> coupled to the base <NUM>. As illustrated in, for example, <FIG>, the base <NUM> comprises a molding material and may include a domed ring <NUM> with a recess <NUM> formed in a top surface <NUM> of the ring <NUM>. The recess <NUM> may have a planar bottom <NUM> with a stem <NUM> extending therefrom. In some embodiments, the stem <NUM> includes a cylindrical first portion <NUM> connected to the bottom <NUM> of the recess <NUM> and a conical second portion <NUM> connected to the first portion <NUM>. In some embodiments, the stem <NUM> is hollow so the stem <NUM> can be easily cut through during, for example, a revision surgery. The base <NUM> may also include a domed bottom <NUM> that is shaped to act as an articulating surface in, for example, a resected patella. In this sense, the size and shape of the base <NUM> may be adjusted as needed to fit to different anatomical geometries. In some embodiments, the base <NUM> comprises a porous biocompatible material that has relatively high strength in order to withstand high loads exerted on the base <NUM> by surrounding anatomical structures following implantation. Exemplary materials that may be used to form the base <NUM> include, but are not limited to: metals such as titanium, stainless steel, cobalt chrome, and/or tantalum; polymers such as ultra-high molecular weight polyethylene (UHMWPE), other forms of polyethylene, polyaryl ether ketone (PAEK) such as polyether ether ketone (PEEK), polylactic acid (PLA),and/or polyglycolic acid (PGA); and/or ceramics such as hydroxyapatite (HA), high-density alumina, so-called "Bioglass," and graphite.

The first porous ingrowth material region <NUM> is coupled to the base <NUM> to provide a region that encourages cell and tissue ingrowth, and thus fixation of the implant <NUM> at the implant site. Exemplary materials that may be used to form the material region <NUM> are similar to materials used to form the base <NUM> and include, but are not limited to, porous titanium, PEEK, or tantalum. The porosity of the material region <NUM> may be varied to alter tissue ingrowth characteristics into the material region <NUM>. The porosity of the material region <NUM> may be, for example, between <NUM>% and <NUM>% to encourage tissue ingrowth into the material region <NUM>. An exemplary material that may be used to form the material region <NUM> is commercially available under the tradename OSTEOSYNC ® from SITES MEDICAL ® of Columbia City, Indiana. It should be appreciated that a wide variety of porous, biocompatible materials may be used to form the material region <NUM> to encourage fixation of the implant <NUM>.

In some embodiments, the material region <NUM> is formed as a composite region with a first ingrowth disc <NUM> coupled to a second ingrowth disc <NUM> by a substantially non-porous barrier layer <NUM> disposed between the discs <NUM>, <NUM>. As used herein, the barrier layer <NUM> may be "substantially non-porous" if the barrier layer <NUM> has a porosity of less than <NUM>% and/or a maximum pore size of the pores of the barrier layer <NUM> is less than <NUM>, such as between <NUM> and <NUM>. In some embodiments, the discs <NUM>, <NUM> and the barrier layer <NUM> are coupled to one another using diffusion bonding or another type of suitable bonding. Each of the discs <NUM>, <NUM> may comprise any of the previously described ingrowth materials and be formed as a domed disc. The second disc <NUM> may be formed with a shape that is complementary to the top surface <NUM> of the ring <NUM> of the base <NUM> and the first disc <NUM> may be formed with a shape that is complementary to the second disc <NUM>. The barrier layer <NUM> may be, for example, a non-porous metal this is diffusion bonded between the discs <NUM>, <NUM> or a polymer material that is molded between the discs <NUM>, <NUM> such that the barrier layer <NUM> prevents pores of the discs <NUM>, <NUM> from being infiltrated by flowing material. In this sense, the barrier layer <NUM> protects porous regions of the discs <NUM>, <NUM> from being filled, maintaining the porosity. In some embodiments, a thickness of the barrier layer <NUM> is relatively small, such as between about <NUM> and about <NUM>. The discs <NUM>, <NUM>, on the other hand, may each have a greater thickness than the barrier layer <NUM>, such as between about <NUM> and about <NUM>.

The discs <NUM>, <NUM> and barrier layer <NUM> may each have a respective stem opening formed therein, with the stem openings aligning to form a opening <NUM> (first illustrated in <FIG>) extending from a top <NUM> of the material region <NUM> to a bottom <NUM> of the material region <NUM>. The opening <NUM> may hold the stem <NUM> of the base <NUM> therein, as will be described further herein. The opening <NUM> may define an opening diameter that is greater than a stem diameter of the stem <NUM>.

The second porous ingrowth material region <NUM> is also coupled to the base <NUM> to provide a region that encourages cell and tissue ingrowth, and thus fixation of the implant <NUM> at the implant site. The material region <NUM> may comprise similar materials to the previously described material region <NUM>. In some embodiments, the material region <NUM> has a domed shape. In some embodiments, the material region <NUM> includes a cylindrical portion <NUM> that is placed adjacent to the material region <NUM> and a tapered portion <NUM> that is connected to the cylindrical portion <NUM>. An opening <NUM> may be formed through the material region <NUM> that extends from a top <NUM> of the material region <NUM> to a bottom <NUM> of the material region <NUM>. The opening <NUM> may have an opening diameter that is greater than the stem diameter of the stem <NUM>, similarly to the opening <NUM>. In some embodiments, the opening <NUM> and the opening <NUM> have the same diameter.

Referring specifically now to <FIG>, the implant <NUM> may further include at least one barrier insert <NUM> that protects pores of the first porous ingrowth material region <NUM> and the second porous ingrowth material region <NUM>. The barrier insert <NUM> may comprise, for example, a barrier material that is a non-porous metal or polymer material or a porous metal or polymer material. In some embodiments, the barrier material is porous and has pores with a maximum pore of no more than <NUM>, such as between <NUM> and <NUM>. In some embodiments, the barrier insert <NUM> is attached to a porous binding ring <NUM>. The stem <NUM> of the base <NUM> may be held in a stem <NUM>, which may also be referred to as a "barrier stem," of the barrier insert <NUM> and the binding ring <NUM> may be held in the recess <NUM> formed in the base <NUM>. In some embodiments, the binding ring <NUM> comprises a similar porous material to the material regions <NUM>, <NUM>. The binding ring <NUM> may be, for example, adhered to the base <NUM> by diffusion bonding or an adhesive or other material to promote binding of the barrier insert <NUM> to the base <NUM>, as will be described further herein. The stem <NUM> of the barrier insert <NUM> may be a hollow cylinder and partially exposed through the opening <NUM> of the material region <NUM>. In some embodiments, the stem <NUM> extends from a closed bottom <NUM> of the barrier insert <NUM> that is closed to prevent molding material of the base <NUM> to pass through the bottom <NUM> during molding.

To form the implant <NUM>, a sheet of material, which may comprise titanium, is prepared. The sheet may be formed as a composite including two or more layers, such as the material of the discs <NUM>, <NUM> with material of the barrier layer <NUM> diffusion bonded or otherwise disposed therebetween. A disc approximating the shape of the material region <NUM> is removed, such as laser cut, from the formed sheet and formed into the domed shape by, for example, pressing the cut shape against a domed block to form the material region <NUM> with a domed shape. The opening <NUM> may also be formed in the material of the formed sheet before, during, or after removal. The barrier insert <NUM> may be machined from, for example, a non-porous material, such as titanium, separately from the material region <NUM>. The material region <NUM> may also be formed by machining a porous material into the desired shape. The binding ring <NUM> may be formed by, for example, cutting the shape of the binding ring <NUM> from a porous material, such as porous titanium.

The barrier insert <NUM> and the binding ring <NUM> are attached to one another. The binding ring <NUM> may, for example, be diffusion bonded to the bottom of the barrier insert <NUM> to form an intermediate assembly. The ingrowth material regions <NUM>, <NUM> are positioned such that they fit over the stem <NUM> of the barrier insert <NUM> of the intermediate assembly. The ingrowth material regions <NUM> and <NUM> may then be diffusion bonded with the intermediate assembly. Before or after diffusion bonding of the ingrowth material regions <NUM>, <NUM> with the intermediate assembly, an opening may be drilled or otherwise formed into the stem <NUM> of the barrier insert <NUM> so the stem <NUM> is a hollow stem.

The diffusion bonded ingrowth material regions <NUM>, <NUM> and intermediate assembly may then be placed in a mold. Melted molding material, which may be a polymer such as UHMWPE, is introduced into the mold and flows through the opening formed in the stem <NUM> to form the base <NUM> and bond the components of the implant <NUM> together. The melted molding material may be introduced by, for example, compression molding. The barrier insert <NUM>, owing to the nature of the barrier material forming the barrier insert <NUM>, protects some of the pores of the material regions <NUM>, <NUM> from filling with molding material as the melted material is introduced, leaving some porous regions of the material regions <NUM>, <NUM> open to tissue ingrowth. In other words, the barrier material is configured to prevent introduction of the molding material of the base <NUM> into some pores of the first porous ingrowth material region <NUM> and some pores of the second porous ingrowth material region <NUM> during molding of the base <NUM>. Other portions of the implant <NUM>, such as the disc <NUM>, the binding ring <NUM>, and the hollow stem <NUM>, fill with the introduced molding material, which cools to bond the components of the implant <NUM> together and form the final implant <NUM>.

From the foregoing, it should be appreciated that the implant <NUM> may be formed in a rapid fashion that securely binds the porous ingrowth material regions <NUM>, <NUM> together with the molded base <NUM>. By protecting pores of various elements of the implant <NUM> with the barrier insert <NUM>, secure bonding can be achieved while also maintaining high porosity for tissue ingrowth. Further, the shapes of the barrier insert <NUM> and the material regions <NUM>, <NUM>, as well as the base <NUM> formed during molding, allow the components to be properly oriented relative to one another in a relatively simple and quick manner. It should thus be appreciated that the present disclosure provides an implant <NUM> that may be rapidly and easily manufactured, which may reduce cost.

In some embodiments, the base <NUM> is pre-formed and is not formed by molding while introducing melted material into the stem <NUM>. In such embodiments, the base <NUM> may be attached to the other components of the implant <NUM> by, for example, diffusion bonding or mechanical attachment.

Referring now to <FIG>, another exemplary embodiment of an implant <NUM> is illustrated that includes a barrier insert <NUM> with molding grooves <NUM> formed therein. The molding grooves <NUM> may be formed, for example, in a barrier stem <NUM> of the barrier insert <NUM>. The molding grooves <NUM> allow material infiltration of molding material of a base <NUM> formed during molding to produce a base stem <NUM> with locking protrusions <NUM>, which securely couple the barrier insert <NUM> to the base <NUM>. In other respects, the implant <NUM> may be structured and formed similarly to the implant <NUM> illustrated in <FIG>, such as including porous ingrowth material regions <NUM> and <NUM>, so further description is omitted for the sake of brevity.

Referring now to <FIG>, another exemplary embodiment of an implant <NUM> is illustrated that includes a base <NUM> with a substantially cylindrical stem <NUM>. The implant <NUM> includes a first porous ingrowth material region <NUM> and a second porous ingrowth material region <NUM> bonded to the base <NUM> with pores protected by a barrier insert <NUM>. It should thus be appreciated that, other than having a base <NUM> with a cylindrical stem <NUM>, the implant <NUM> may be structured and formed similarly to the previously described implants <NUM>, <NUM>, so further description is omitted for the sake of brevity.

Referring now to <FIG>, another exemplary embodiment of an implant <NUM> is illustrated that includes a base <NUM> formed without a recess. The implant <NUM> further includes a first porous ingrowth material region <NUM> and a second porous ingrowth material region <NUM> coupled to the base <NUM> with pores protected by a barrier insert <NUM>, which may bind to a binding ring <NUM>. The material region <NUM> may be formed as a flat ring, i.e., non-domed, and resemble the shape of a washer. The binding ring <NUM> may be formed similarly to the material region <NUM> and bonded to a flat top surface <NUM> of the base <NUM> during molding. The material regions <NUM>, <NUM> are fit over a molding stem <NUM> of the barrier insert <NUM> and melted material introduced to bond the material regions <NUM>, <NUM> together and form the base <NUM>. The barrier insert <NUM> protects some pores of the material regions <NUM>, <NUM>. Thus, the material regions <NUM>, <NUM> securely bond to each other (and the formed base <NUM>) and form the implant <NUM> without a significant filling of some or all of the pores of the material regions <NUM>, <NUM>, similarly to the previously described implants <NUM>, <NUM>, <NUM>. In other respects, the implant <NUM> may be structured and formed similarly to the previously described implants <NUM>, <NUM>, <NUM>, so further description is omitted for the sake of brevity.

Referring now to <FIG>, another exemplary embodiment of an implant <NUM> is illustrated that includes a base <NUM> including three spaced-apart stems 815A, 815B, 815C. The implant <NUM> also includes a first porous ingrowth material region <NUM> and a plurality of second porous ingrowth material regions, illustrated as three material regions 830A, 830B, 830C, coupled to the base <NUM>. The material region <NUM> may be formed as a substantially flat ring with a plurality of openings 824A, 824B, 824C formed therein. The material regions 830A, 830B, 830C may each be formed as a cylinder with a respective opening 833A, 833B, 833C. In some embodiments, the openings 824A, 824B, 824C of the material region <NUM> each define a respective opening diameter that is larger than a region diameter of a corresponding material region 830A, 830B, 830C so each of the material regions 830A, 830B, 830C fits within a respective opening 824A, 824B, 824C. A plurality of barrier inserts 840A, 840B, 840C may protect pores of the material regions <NUM>, 830A, 830B, 830C during molding of the base <NUM>. A binding ring <NUM> may bind to a top surface <NUM> of the base <NUM>. The binding ring <NUM> may be formed of a similar material as the material regions <NUM>, 830A, 830B, 830C and have a plurality of openings 842A, 842B, 842C and, in some embodiments, a non-porous top surface <NUM>.

To form the implant <NUM>, a sheet of material, which may comprise titanium, is prepared. The material region <NUM> may be separated from the sheet and the openings 824A, 824B, 824C formed in the material region <NUM> by, for example, laser cutting. The material regions 830A, 830B, 830C may be formed by, for example, machining. The barrier inserts 840A, 840B, 840C may also be formed by machining. Each of the barrier inserts 840A, 840B, 840C may be formed with a respective stem 845A, 845B, 845C and abut against at least one adjacent barrier insert 840A, 840B, 840C.

The barrier inserts 840A, 840B, 840C are attached to the binding ring <NUM> by, for example, diffusion bonding to form an intermediate assembly. The material region <NUM> is positioned so each stem 845A, 845B, 845C of the barrier inserts 840A, 840B, 840C extends through a respective opening 824A, 824B, 824C and the material regions 830A, 830B, 830C are placed over a respective one of the stems 845A, 845B, 845C. The material regions <NUM>, 830A, 830B, 830C and intermediate assembly may then be attached together, such as by diffusion bonding, and openings may be formed in each of the stems 845A, 845B, 845C so the stems 845A, 845B, 845C are each hollow.

The diffusion bonded material regions <NUM>, 830A, 830B, 830C and intermediate assembly may then be placed in a mold. Melted material, which may be a polymer such as UHMWPE, is introduced into the mold and flows through the openings formed in the stems 845A, 845B, 845C to form the base <NUM> and bond the components of the implant <NUM> together. The melted material may be introduced by, for example, compression molding. The barrier inserts 840A, 840B, 840C, owing to their non-porous nature, protect some of the pores of the material regions <NUM>, 830A, 830B, 830C from filling with material as the melted material is introduced, leaving some porous regions of the material regions <NUM>, 830A, 830B, 830C open to tissue ingrowth. Other portions of the implant <NUM>, such as a bottom of the binding ring <NUM>, and the hollow stems 845A, 845B, 845C of the barrier inserts 840A, 840B, 840C, fill with the introduced material, which cools to bond the components of the implant <NUM> together and form the final implant <NUM>. From the foregoing, it should be appreciated that the implant <NUM> may be formed similarly to the previously described implants <NUM>, <NUM>, <NUM>, <NUM>, but include more than one stem. Additional stems may be useful when, for example, a larger implant size is needed to repair a defect in a bone. Thus, it should be further appreciated that implants may be formed in accordance with the present disclosure that include multiple stems and have different sizes to meet different surgical requirements.

Referring now to <FIG>, another exemplary embodiment of an implant <NUM> is illustrated that includes three barrier inserts <NUM> with hollow stems, similarly to the implant <NUM>, that each have molding grooves <NUM>. The molding grooves <NUM> fill with material during molding to form corresponding molded stems <NUM> of a base <NUM>. The stems <NUM> of the base <NUM> have molding protrusions <NUM> that fill the molding grooves <NUM> to securely lock the barrier inserts <NUM> and the base <NUM> together. In other respects, the implant <NUM> may be structured and formed similarly to the implant <NUM> illustrated in <FIG>, so further description is omitted for the sake of brevity.

Claim 1:
An orthopaedic implant (<NUM>), comprising:
a base (<NUM>) comprising a molding material;
a first porous ingrowth material region (<NUM>) coupled to the base (<NUM>);
a second porous ingrowth material region (<NUM>) coupled to the base (<NUM>); and
at least one barrier insert coupled to the base (<NUM>), the barrier insert comprising a barrier material that is configured to prevent introduction of the molding material of the base (<NUM>) into some pores of the first porous ingrowth material region (<NUM>) and some pores of the second porous ingrowth material region (<NUM>) during molding of the base (<NUM>);
characterised in that
the base (<NUM>) further comprises a hollow stem(<NUM>) ; and/or
the first porous ingrowth material region (<NUM>) comprises a first ingrowth disc (<NUM>), a second ingrowth disc (<NUM>), and a barrier layer (<NUM>) coupled to the first ingrowth disc (<NUM>) and the second ingrowth disc (<NUM>); and/or
the at least one barrier insert (<NUM>) comprises a plurality of barrier inserts and each of the barrier inserts abuts against at least one adjacent barrier insert and/or each of the barrier inserts comprises a respective barrier stem (<NUM>).