Patent Publication Number: US-2021177599-A1

Title: Implant with Porous Outer Cortical Layer

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Ser. No. 14/819,758, filed Aug. 6, 2015, titled “Implant with Porous Outer Cortical Layer,” which application claims the benefit of U.S. Provisional Application Ser. No. 62/034,014, filed Aug. 6, 2014, titled “Hollow Implant” and U.S. Provisional Application Ser. No. 62/042,085, filed Aug. 26, 2014, titled “Implant,” the entire contents of each of which are hereby incorporated by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     Embodiments of the present disclosure relate generally to an implant having an outer cortical layer that is porous. The porous outer cortical layer can help encourage tissue ingrowth into the implant. The porous outer cortical layer may be positioned around a core structure this is solid or that has a hollow interior. The core structure may be spherical or any other shape. 
     BACKGROUND 
     Craniofacial surgery generally includes restructuring a damaged portion of a patient&#39;s bone or other tissues. For example, ocular implants such as spheres can be used in connection with enucleation and evisceration procedures. In one example, the orbit is the boney socket in the skull that contains and houses the eye, along with the associated structures that support eye function, such as the eye muscles, nerves, and blood vessels. In some instances, a variety of problems can occur in the eye socket, ranging from inflammatory diseases or other diseases, tumors, infections, birth defects, or injuries from trauma. When these problems occur, it may become necessary to reconstruct various portions of the orbital socket, including implantation of ocular implants, such as orbital spheres. 
     In some instances, it is desirable for an implant to allow fibrovascular ingrowth such that it becomes integrated with the patient&#39;s own tissues. It is generally accepted that providing ocular implants made of biocompatible porous material can help encourage vascularization and tissue ingrowth. Various materials for orbital implants have included silicone, high density polyethylene, porous alumina, and hydroxyapatite. However, improvements to surgical implants and materials are desirable. 
     BRIEF SUMMARY 
     Embodiments of the present disclosure relate generally to an implant having an outer cortical layer that is porous. The porous outer cortical layer can help encourage tissue ingrowth into the implant. The porous outer cortical layer may be positioned around a core structure this is solid or that has a hollow interior. The core structure may be spherical or any other shape, such as elongated, plate-shaped, curved, or any other appropriate shape. The porous outer cortical layer and a supporting core (if provided) may be generally formed of the same or a similar material, such that they may be thermally bonded to one another. In one specific example, the core and cortex are sintered to one another. 
     For example, there may be provided an implant, comprising a core material comprising an outer surface that functions as a barrier to tissue ingrowth; a porous outer cortical layer sintered to and at least partially surrounding the core material, wherein the porous outer cortical layer allows tissue ingrowth. The core material may be formed as a hollow body or as a solid body. The core material and the porous outer cortical layer may be thermally processed via heat and compression. In use, fibrovascular ingrowth is allowed to occur into the porous outer cortical layer but is discouraged from extending past the barrier to tissue ingrowth. 
     Embodiments also provide a method of manufacturing an implant, comprising: forming a core material having a plurality of registering members extending therefrom; positioning the core material in a mold; applying a porous polymeric material around the core material in the mold, such that the porous polymeric material at least partially covers the core material; applying heat and pressure to sinter the porous polymeric material to the core material. 
     In another example, there is provided a method of manufacturing an implant, comprising: providing a plurality of individual articles having differing porosities, wherein the individual articles form a generally spherical implant; assembling the plurality of individual articles in a mold; applying heat and pressure to sinter the plurality of individual articles to one another. 
     In other embodiments, the implant is formed as a hollow body having an interior coating, such that outer surface of the hollow body allows tissue ingrowth and the interior coating prevents further ingrowth. In one example, the hollow body may be manufactured from two halves that are thermally processed together, the hollow body halves comprising an interior coating that prevents tissue ingrowth, and a porous outer surface that encourages tissue ingrowth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of an implant according to one embodiment described herein, cut in half to show a solid core material and an outer porous cortical layer. 
         FIG. 2  shows a perspective view of an implant according to an alternate embodiment, having an inner coating on the porous cortical layer. 
         FIG. 3  shows a perspective view of an implant cut in half to show a porous core material and an outer porous cortical layer. 
         FIG. 4  shows an exploded view of an implant made from two hollow half spheres of a solid material, with a cortical material applied thereto. 
         FIG. 5  shows the implant of  FIG. 4  cut in half. 
         FIG. 6  shows an exploded view of an implant made from two hollow half spheres of a porous material, with a cortical material applied thereto. 
         FIG. 7  shows a close-up view of a core having a porous outer cortical layer, illustrating one example of the layer thickness. 
         FIG. 8  shows a core with registering features, for use during one manufacturing method described herein. 
         FIG. 9  shows one embodiment of an implant outer surface. 
         FIG. 10  shows two hollow cortical layer halves to be applied to a solid material core. 
         FIG. 11  shows one manufacturing process for providing a plurality of half spheres to form a core. 
         FIG. 12  shows a plurality of individual articles having varying porosities that may be assembled to form an implant. 
         FIG. 13  shows a plurality of individual articles assembled, and prior to application of heat and compression. 
         FIG. 14  shows an implant having varying porosities on its porous outer cortical layer. 
         FIG. 15  shows a cross-sectional view of an implant having a porous outer cortical layer varying porosities, with a smaller pore size forming its outermost layer and a larger pore size forming a more inner layer. 
         FIG. 16  shows an example of an alternate shape of an implant with a porous outer cortical layer. 
     
    
    
     DETAILED DESCRIPTION 
     Specific embodiments of the present invention provide an implant having a porous outer cortical layer. The implant finds particular use in non-load bearing applications and reconstructions for the craniofacial skeleton and surrounding structures. As shown in  FIG. 1 , one embodiment of the implant  10  may have a core  12  surrounded or at least partially covered by a porous outer cortical layer  20 . The core  12  may be solid or hollow. As shown in  FIG. 2 , another embodiment may provide a hollow implant  50  having an outer porous cortex or (outer cortical layer)  20  (for promoting tissue ingrowth) and an interior coating or layer  52  that is non-porous for preventing further tissue ingrowth past the interior coating  52 . 
     Both embodiments allow fibrovascular ingrowth into the outer cortex  20  of the implant  10 ,  50 , but prevent the ingrowth from extending into a core or interior of the implant  10 ,  50 . While not wishing to be bound to any theory, it is believed that providing a porous external layer limits the depth of tissue integration into the implant without leaving a non-fully vascularized void in the center. It is believed that providing a generally thin cortical layer for ingrowth of tissue allows tissue ingrowth to occur more quickly. The ingrowth stops once it reaches the core  12  of implant  10 , or the coating/layer  52  of implant  50 . With quicker vascularization of the implant, a reduction of infection and related possible complications may be achieved. 
     Referring first to the core  12 /cortex  20  embodiment, the porous outer cortical layer  20  may be thermally bonded to the core  12 . In one example, the core  12  may be a solid core, as shown by  FIG. 1 . In another example, the core  12  may be a porous polymer sphere implant formed as a non-hollow body  14  (i.e., a body that has porous material throughout), as shown by  FIG. 3 . The body  14  may be generally porous with a non-porous surface  18 . In other examples, the core may be a hollow core. The hollow core may be a solid material, as shown by  FIGS. 4 and 5 . For example, the core  12  may be a silicone body. In another example, the hollow core may be a hollow porous polymer sphere implant formed as a hollow body  16 , as shown by  FIG. 5 . In a further example, the core  12  may have any other appropriate shape or material. Although in the examples shown, the core  12  is illustrated as having a spherical shape, it should be understood that the core  12  may have any appropriate shape for the desired implant. For example, it may be an elongated rod if designed for use along a longer bone, a curved form, a plate form, or any other appropriate shape. 
     In some examples, the implants described herein may be used to stabilize, support, and provide space maintenance for bone graft materials in the maxilla, mandible zygoma, and other craniomaxillofacial areas. In other examples, implants may be used in the vertebral space, within the space between vertebral bodies. Other examples of uses of embodiments of implants described herein include but are not limited to surgeries involving long bones or portions of appendages such as the legs and arms, or a rib or any other bone or cavity. 
     For purposes of illustration, a spherical implant  10 ,  50  is described for the remainder of this disclosure. Various methods for manufacturing a spherical core  12  are outlined further below. The core may be designed so that it is not susceptible to leakage to fluid migrating into the core. The core may be designed so that it will maintain its shape, delaying the need for replacement of the implant. 
     In one example, the core  12  may be provided with an outer surface  18  that is smooth or otherwise non-porous. Such as outer surface  18  prevents, discourages, or limits vascular ingrowth or integration. The outer surface  18  forms what will eventually be an internal layer of solid (non-porous) material of the implant  10  that serves as a barrier to tissue/bone ingrowth. 
     Surrounding the core  12  may be a porous outer cortical layer  20 . The porous outer cortical layer  20  may have a porous structure that encourages fibrovascular ingrowth or integration into the porous outer cortical layer  20 . The porous outer cortical layer  20  may fully encapsulate the core. Alternatively, the porous outer cortical layer  20  may only at least partially encapsulate the core.  FIG. 7  illustrates a cross-sectional view of a portion of a core  12  with a non-porous outer surface  18  having a surrounding porous outer cortical layer  20 . In one example, the porous outer cortical layer  20  may be thermally bonded to the outer surface  18  of the core  12 . 
     In one embodiment, the core  12  may be provided with a plurality of registering features  22  that are designed to hold the core  12  in a center of a mold cavity.  FIG. 8  illustrates a core  12  having three generally equally spaced registering features  22 . It should be understood that more or fewer features  22  may be provided. The registering features  22  may be formed as extending pegs. They may be porous or non-porous. In use, the registering features  22  can help center the core  12  with respect to a mold cavity in order to allow space between the mold cavity and the outer surface  18  of the core  12 . The interior shape of the mold cavity may be spherical in order to properly form the core  12 . Beads, particles, or fines of the material that will form the porous outer cortical layer  20  may be delivered to the mold, such that they fill spaces around the core  12 . The material also fills spaces around the registering features  22 . Application of compression and heat via thermal processing may then cause sintering of the material to the core  12 . This creates an over molded porous cortical layer  20 . The heat and compression of the thermal process may cause the core  12  and the outer cortical layer  22  become sintered together, such that they are connected as a one-piece, integral implant. 
     As shown in  FIG. 7 , the layer  20  may be up to about two or three beads or particles thick. It is possible for the layer  20  to be thinner than three beads or particles thick. It is also possible for the layer  20  be thicker than three beads or particles thick. As an example only, it is possible for the porous outer cortical layer  20  to be between about 0.5 to about 1.5 mm thick. In a specific embodiment, the layer  20  may be about 0.8 to about 0.9 mm thick. (Of course, it is understood that the thickness of the layer  20  is dependent upon the diameter of the core. In these examples, the core is generally about 4-6 mm in diameter. Other core sizes may be provided, and it is understood that the thickness of the layer  20  may be adjusted accordingly.) In another embodiment, the core may be from about 1-10 mm in diameter, and the porous outer cortical layer  20  may be from about 2-5 mm thick. 
     In some embodiments, the implant may comprise a single sintered polymeric layer. In other embodiments, the implant may comprise a plurality of sintered polymeric layers. It is possible for each of the plurality of layers to be constructed independently of another layer. They may be provided by multiple thermal processes. As a result, it is possible to provide layers of an implant that demonstrate different polymers, pore sizes, or any other features. 
     The general goal is for the porous outer cortical layer  20  to have a thickness that allows tissue ingrowth. However, the thickness of the porous outer cortical layer  20  also limits the depth that the tissue integration may reach, due to its contact with the outer surface  18  of the core  12 , which does not support tissue integration any further into the implant  10 . In use, the porous outer cortical layer  20  limits the depth of tissue integration into the implant  10  without leaving a non-fully vascularized void in the center of the implant  10 . By contrast, in a thick porous implant that is porous completely throughout, the center of the implant generally does not achieve 100% vascularization, which can leave an area of the implant full of fluid which can possibly produce lead to infections. 
     It can be desirable for the porous outer cortical layer  20  to extend up to and generally along the length of the registering features  22 . In some examples, the registering features  22  may be about 0.5 to about 1.5 mm long. In other examples, the registering features  22  may be up to about 3 mm long.  FIG. 9  illustrates a formed implant  10  having a diameter D that is equal to that of the diameter of the core  12  plus the thickness of the layer  20 . This implant  10  is also shown having a slight registration mark  24  along the implant outer surface of  26 . The registration mark  24  is the tip of one of the registering features  22 . The registration mark  24  may have a diameter and/or shape that is generally equal to that of one to three particles in size, respective to the particle size of the material used. This results in a non-obvious registration mark  24  on the finished cortex article/implant  10 . 
     Prior to applying the porous outer cortical layer  20  to the core  12 , the core  12  may be manufactured using any appropriate manner. If the core  12  is provided as a hollow body  16 , it may be compression molded, injection molded, blow molded, rotational molded, or formed using any other appropriate manufacturing technique. If the core  12  is provided as a solid, non-hollow body  14 , it may be manufactured using any appropriate techniques, non-limiting examples of which are described further below. 
     The core  12  may be provided in any appropriate material. Non-limiting examples include porous polyethylene, polypropylene, medical grade silicone, or any combinations thereof. In one embodiment, implants comprise polyolefins, polymers, polyamides, polyesters, polyurethanes, polyimides, polyacrylonitriles, polycarbonate, poly methyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyketones, polysulfones, polyetherimides, or combinations or copolymers thereof. In some embodiments, a polyolefin may comprise polyethylene, polypropylene, or combinations or copolymers thereof. Polyethylene may comprise porous polyethylene, high density polyethylene (HDPE) or ultrahigh molecular weight polyethylene (UHMWPE). In some embodiments, polyketones may comprise polyether ketone (PEK), polyether ether ketone (PEEK), or combinations thereof. In some embodiments, polysulfones may comprise polyether sulfone (PES), polyphenol sulfone, or combinations or copolymers thereof. In some embodiments, polymers may comprise silicone. 
     It is generally desirable that the material be inert to tissue and resistant to degradation over time when in contact with surrounding tissue and fluids. The outer surface  18  of the core may have a texture that is non-porous but generally open enough (or rough enough) to allow the porous cortical layer  20  to mechanically bond to the surface. (This is generally upon application of compression and heat, but other attachment options are possible and considered within the scope of this disclosure.) The center of the core may a more flexible or rigid core. 
     For manufacturing a hollow implant, rotational molding is one method that may be used to provide a core with a hollow area. In this method, a small amount of material may be added to a mold cavity in the mold is continually rotated and heated. This may result in a porous hollow article. 
     In another example, the hollow body  16  may be manufactured by cutting a partially processed device in half, and removing the inner contents that are unprocessed and loose in order to form a hollow vessel. The cut halves may be re-assembled and returned to the mold in order to complete the bonding process of the material and rejoin the two halves. 
     In another embodiment, a blow molded polymer sphere may be provided with a connecting tube during molding that can allow inflation inside a mold cavity in order to produce a hollow sphere that is later sealed with internal pressure. 
     In another example, the hollow body  16  may be manufactured by manufacturing two hollow half spheres  28 . Examples are illustrated by  FIGS. 4-6 . In use, the hollow half spheres  28  may be secured to one another in order to provide a hollow body  16  that forms the core  12 . It is generally desired for the half spheres  28  to be sealed to one another in use to form the final implant  10 . This can help prevent fluid from accumulating within the core  12  and causing rejection or infection. In one example, they may be secured by thermal processing. In the embodiments shown in  FIGS. 4-5 , the hollow half spheres  28  may be made of generally solid material. In the embodiment shown in  FIG. 6 , the hollow half spheres  28  may be made of generally porous material. 
     In another example illustrated by  FIG. 10 , the core  12  may be formed as a solid, non-hollow sphere  14  (or as two solid half spheres, if desired). A solid core  14  may be a solid material, such as silicone sphere, a polymer sphere, or any other appropriate material. In other examples, the non-hollow sphere  14  may be made of a porous material, In either case, the non-hollow core may be manufactured by insert molding, injection molding, compression molding (being sintered in a mold), vacuumed molding, blow molding, or any other appropriate manufacturing technique or process. 
     If the core  12  is provided as solid half spheres  15  , the solid half spheres may be formed by blow molding, by insert molding, or by any other appropriate manufacturing technique. One example illustrating a manufacturing method for a plurality of half spheres  15  is shown by  FIG. 11 . In one embodiment, blow molding may create a sealable spherical shape. The internal pressure of the blow molding process may help overcome shrinkage forces to maintain a desired shape of the final article. The solid half spheres may be formed into a single solid spherical core  12 . The halves may be welded together by heat, ultra sonic welding, gamma waves, or any other appropriate technique. Providing half spheres may add to the manufacturability of the device. For some shapes, it may be easier to or necessary to produce two or more halves and reassemble these prior to processing together. 
     In another example, the implant  10  may be formed from a plurality of individual articles  32  assembled together. The individual articles  32  may have varying porosities. One example of variously shaped articles  32  is shown in  FIG. 12 . In this example, there may be provided cap components  34 , upper components  36 , and equatorial components  38 . More or fewer components may be provided. In one example, a center exterior portion/equatorial component  38  of the sphere may have smaller pores than one or more of the other portions. For example, a posterior portion of the implant could be made to be more porous in order to facilitate faster tissue integration. An anterior portion of the implant may have a lower porosity, be smoother, or even be formed to be non-porous. This may help is insertion of the implant  10  into the implant site. Manufacturing an implant  10  using this design can help control locations of desired pore sizes. In fact, some of the individual articles  32  may be solid/non-porous. 
       FIG. 13  illustrates an assembly of the individual articles  32  prior to being inserted in a mold and thermally processed. Thermal processing results in a one piece composite unit having varying pore sizes. One example of an implant having varying pore sizes on its face is illustrated by  FIG. 14 . It is possible for the secondary molding operation (referred to as “secondary molding” because the individual articles may be formed by a first molding step) to cause the surface pores to become more compressed together, producing a smoother outer surface  62  with larger internal pores  60  for improved tissue ingrowth. One cross-sectional view of this varying pore size embodiment is illustrated by  FIG. 15 . 
     Because it has been found generally desirable for the outer surface  18  of the core  12  to be non-porous to prevent tissue ingrowth, it is possible for the core  12  to be formed in a way that provides a non-porous outer surface  18 . For example, the material may be selected so that the pores of the material are so small that they discourage tissue ingrowth. In another example, the material may be selected so that the entire core is non-porous (e.g., the solid or hollow core may be manufactured out of a non-porous material). In another example, it is also possible to secure, bond, adhere, or thermally compress a thin solid membrane to the outer surface of the core, before application of the porous outer cortical layer  20 . 
     The porous outer cortical layer  20  may be formed as two separate components  30  and thermally bonded to the core  12 . Examples of this option are illustrated by FIGS.  4 - 6  and  10 . In these examples, the core may be mechanically entrapped within the layer  20 . In other embodiments, the porous outer cortical layer  20  may be applied as described above (i.e., as a sintered coating applied around via beads or fines positioned around a core in a mold and exposed to compression and heat). In further embodiments, the porous outer cortical layer  20  may be sprayed, painted, powder coated, or applied to the core  12  using any other appropriate technique. In a further embodiment, the porous outer cortical layer  20  may be applied to core using static charged particles with a grounded mandrel tool to which the particles are attracted to. The implant is then thermally processed in order to produce the desired shape. 
     The porous outer cortical layer  20  may be provided in any appropriate material. It may comprise polyolefins, polymers, polyamides, polyesters, polyurethanes, polyimides, polyacrylonitriles, polycarbonate, poly methyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyketones, polysulfones, polyetherimides, or combinations or copolymers thereof. In some embodiments, a polyolefin may comprise polyethylene, polypropylene, or combinations or copolymers thereof. Polyethylene may comprise porous polyethylene, high density polyethylene (HDPE) or ultrahigh molecular weight polyethylene (UHMWPE). 
     Other examples include polyetherether ketone (PEEK), polyethylene terephthalate (PETE), nylon, polypropylene, or any polymer of aliphatic hydrocarbons containing one or more double bonds, or composites of any of these materials. In some embodiments, polyketones may comprise polyether ketone (PEK), polyether ether ketone (PEEK), or combinations thereof. In some embodiments, polysulfones may comprise polyether sulfone (PES), polyphenol sulfone, or combinations or copolymers thereof. In some embodiments, polymers may comprise silicone. This list is not intended to be limiting, and it should be understood that the porous outer cortical layer may be made from any other appropriate material that can be formed to encapsulate or otherwise cover the core  12  and allow the implant  10  to be at least partially pliable, while also imparting the desired porosity. 
     In one example, the porous outer cortical layer  20  may have a porous structure with an interconnecting porosity. The pores of this layer may range from about 10 μm to about 1 mm. In a specific embodiment, the average pore size may range from about 100 μm to about 400 μm, from about 150 μm to about 300 μm, from about 200 μm to about 250 μm, from about 300 μm to about 400 μm, or from about 400 μm to about 600 μm. In some embodiments, the average pore size may be at least 20 μm. In another embodiment, the average pore size may be at least 50 μm. In another embodiment, the average pore size may be greater than about 10 μm. In another embodiment, the average pore size may be less than about 1 mm. The pores may be multidirectional interconnected pores. 
     The materials are generally formed to have an interconnected porous structure (generally referred to as “porous”). The cortical layer  20  may cover greater than 50% of the core, greater than 60%, greater than 70%, greater than 80%, greater than 90%, or greater than 99% of the surface of the core. 
     In some embodiments, the layer  20  has a porosity ranging from about 20% to about 60%, from about 30% to about 50%, from about 35% to about 40%, or from about 50% to about 60%. In another embodiment, the layer  20  may have a porosity of about 20% or greater. In another embodiment, the layer may have a porosity less than about 60%. 
     In embodiments in which the core  12  and/or the porous outer cortical layer  20  is polyethylene, it is generally desired that the melt flow index value of the materials be such that the polyethylene sinters upon thermal processing, but does not melt and begin to flow. For example, the melt flow index (MFI) values provided in Table 1 determined at 10 minutes under a 2.16 kg load at 190° C. as detailed in ASTM 1238-65. MFI values of polyethylene may be less than 100 g, less than 50 g, less than 30 g, less than 15 g, less than 10 g, less than 5 g, less than 2 g, or less than 1 g. 
     In embodiments in which the core  12  and/or the porous outer cortical layer  20  is polypropylene, it is generally desired that the MFI value of the materials be such that the polyethylene sinters upon thermal processing, but does not melt and begin to flow. For example, the MFI values provided in Table 2 were determined at 10 minutes under a 2.16 kg load at 230° C. as detailed in ASTM 1238-65. MFI values of polypropylene may be less than 100 g, less than 50 g, less than 30 g, less than 15 g, less than 10 g, less than 5 g, or less than 2 g. 
     In embodiments in which the core  12  and/or the porous outer cortical layer  20  is polyetheretherketone (PEEK), it is generally desired that the MFI value of the materials be such that the PEEK sinters upon thermal processing, but does not melt and begin to flow. For example, the MFI values provided in Table 3 were determined at 10 minutes under a 5 kg load at 379° C. as detailed in ISO 1133. MFI values of PEEK may be less than 100 cm 3 , less than 50 cm 3 , less than 30 cm 3 , less than 15 cm 3 , less than 10 cm 3 , less than 5 cm 3 , or less than 2 cm 3 . 
     In some examples, it is possible to provide the core  12  and the layer  20  as a being manufactured of the same materials. For example, it is possible to provide an implant  10  having a core  12  with a solid polymer outer surface, and a cortical layer  20  of a porous polymer. In one example, both parts are made of a biocompatible polyethylene. 
     In another example, the core may be a medical grade silicone with a porous polyethylene cortical layer flexibly molded over the core. 
     In another example, the core may be silicone and the porous cortical layer may be polyethylene. In one specific example, the core may be silicone with an outer surface having a texture, and the porous cortical layer may be porous polyethylene. 
     In another example, the core may be polyethylene and the porous cortical layer may be polyethylene. In one specific example, the core may be solid polyethylene and the porous cortical layer may be porous polyethylene. 
       FIG. 1  illustrates an outer cortical layer  20  of porous polyethylene that is flexibly molded over an inner core material  12 . In this example, the inner core material is silicone. In this figure, the silicone core  12  has a molded outer surface texture that allows the porous polyethylene to mechanically bond to the surface of the center core  12 . 
     In another example, the porous outer cortical layer  20  may be formed as two separate components  30 . In  FIG. 10 , the components  30  are shown as hollow half spheres. The components  30  may then be thermally bonded to the core  12 . In this example, the core  12  is mechanically entrapped within the two components  30 , which form the outer layer  20 . 
     However, it is also possible for the components  30  themselves to form implant  50 . One example of this embodiment is illustrated by  FIG. 2 . In this example, there is not an interior core provided, but instead, the two hollow components  30  may be internally coated or sealed with an internal layer  52  that prevents tissue ingrowth past the coating layer  52 . In this implant  50 , the two hollow components actually form the porous outer cortical layer  20  on their own. 
     Additive materials may be included in or on the implant, such as biological or inorganic materials. Exemplary additive materials include but are not limited to bone graft materials, bone or tissue growth promoting substance/osteogenic materials, pharmaceuticals, morphogenetic proteins, silver additives to provide an anti-infection benefit, other transition metals (such as titanium, silver, gold, surgical grade stainless steel, steel coated with titanium, titanium nitride, titanium alloyed with other metals, or mixtures thereof), ceramic/zeolite, calcium phosphates, barium sulfate, imaging contrast agents, materials used to make the implant radiopaque such as beryllium, an inorganic material such as hydroxyapatite or glass, or any combinations thereof. Exemplary osteogenic/bone growth promoting substances include but are not limited to autograft, allograft, xenograft, demineralized bone, synthetic and/or natural bone graft substitutes such as bio ceramics and polymers, osteoinductive factors, or combinations thereof. If the additive material is glass, a representative glass may have a composition comprising by weight 45% SiO 2 , 24.5% Na 2 O, 24.5% CaO, and 6% P 2 O 5 . Another exemplary glass may be Bioglass, commercially available from NovaBone products, LLC of Alachua, Fla. If the additive material is a calcium phosphate, it may have a calcium to phosphorus atomic ratio ranging from about 0.5 to about 2.0. Non-limiting examples of calcium phosphates include but are not limited to amorphous calcium phosphate, monocalcium phosphate monohydrate (MCPM), monocalcium phosphate anhydrous (MCPA), dicalcium phosphate dehydrate (DCPD), dicalcium phosphate anhydrous (DCPA), octacalcium phosphate (OCP), alpha-dicalcium phosphate, beta-try calcium phosphate, hydroxyapatite, poorly crystalline hydroxyapatite, tetracalcium phosphate (TTCP), heptacalcium decaphosphate, calcium metaphosphate, calcium pyrophosphate dehydrate, calcium pyrophosphate, carbonated calcium phosphate, or combinations thereof. 
     Such additives may be included in an amount ranging from up to about 30 wt %. In some examples, additives may be added from about 5 wt % to about 20 wt %, or from about 10 wt % to about 15 wt %. It is possible to include additives in an amount that is greater than about 1 wt %, or in an amount that is less than about 30 wt %. 
     Such additive materials may be combined with the porous outer cortical layer  20 , such that they form a part of the periphery of the implant. Additionally or alternatively, such additive materials may be provided (e.g., packed or injected) within the interior of the implant  10 . Materials they be dispersed throughout the matrix of the implant. 
     The implant may further include openings (foramina), grooves, and/or channels that are intended to permit the transmission of a nerve (such as the optic nerve, ophthalmic nerve, trochlear nerve, a duct such as the nasolacrimal duct, or one or more blood vessels). A channel may also be used to drain a site of excess fluid, such as blood or sample fluid, for analysis. Such openings or channels provided in specific locations may allow the implant to be used over or adjacent to a nerve without causing any impingement or crushing of the nerve when the implant is secured in place. 
     Although embodiments of this disclosure have been described with particular reference to ocular implants, it should be understood that the concepts described herein may be used with other surgical implants. For example, it is possible to provide a core material coated with a porous outer cortical layer for other types of implants. Examples include but are not limited to ear reconstruction implants, joint implants, chin and other facial implants, spinal implants, or any other type of implant for which vascular ingrowth is desirable. One example of a potential configuration for one or more of these implants is illustrated by  FIG. 16 . In this example, the porous outer cortical layer is positioned on a core that is shaped as an ear implant. 
     In order to manufacture any of the embodiments described herein, the sintering and/or compression temperature may be between about 280° F. to about 360° F. The sintering ad/or compression time may be between 5 minutes up to about 120 minutes. These examples are provided for illustrative purposes only, and are not intended to be limiting in any way. 
     Changes and modifications, additions and deletions may be made to the structures and methods recited above and shown in the drawings without departing from the scope or spirit of the disclosure or the following claims.