Abstract:
The present invention discloses an implant for use with a joint defining bone having a three dimensional shape and including a first exposed and joint surface defining layer and an inner most and bone mounting layer. The body further has at least one intermediate layer exhibiting a hardness less than either of the exposed layer and the inner most layer such that, upon mounting the body to a conditioned end of a joint defining bone, it provides the dual features of dynamic cushioning support and external wear resistance.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/244,203 filed Sep. 21, 2009. 
    
    
     FIELD OF THE INVENTION 
     The present invention discloses an end secured (or fused) implant device for use with various knee, elbow, hip, shoulder or other joint applications. More particularly, the present invention teaches a multi-layer joint surface implant for use with such as existing bones and which exhibits a softer plastic layer encased between outer hardened plastic layers, this in order to enhance both cushioning and wear resistance. Additional variants also contemplate constructing the implant of various metal or poly/metal composites and which maximize the durability and wear resistant aspects of the design. 
     DESCRIPTION OF THE BACKGROUND ART 
     The prior art is well documented with examples of knee, elbow, hip, shoulder and other joint applications such as associated with medical implants. An objective associated with such implants is the ability to provide a functional and durable joint which replaces a natural joint which may have become damaged over time. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention discloses an implant for use with a joint defining bone, including a body having a three dimensional shape and including a first exposed and joint surface defining layer and an inner most and bone mounting layer. The body further has at least one intermediate layer exhibiting a hardness less than either of the exposed layer and the inner most layer such that, upon mounting the body to a conditioned end of a joint defining bone, it provides the dual features of dynamic cushioning support and external wear resistance. 
     Additional features include the body being constructed of at least one of a metal, plastic or composite material. The inner mounting layer further includes an inner marrow contacting portion configured as a perimeter enclosing and inserting portion which engages an opposing and inner facing wall surfaces of the bone. The inner most surfaces of the marrow contacting portions exhibit roughened portions which facilitate bonding of the plug to a previously sectioned/reconditioned bone end. 
     The exposed and joint defining surface layer further include a contoured profile, with the intermediate layer further having a perimeter edge extending and inner concave profile facilitating dynamic cushioning movement and support of the exposed and joint surface defining layer. The intermediate layer may further include at least one of an undulating and a planar extending width. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to the attached drawings, when read in combination with the following detailed description, wherein like reference numerals refer to like parts throughout the several views, and in which: 
         FIG. 1  is a cutaway illustration of a knee joint application and illustrating first and second opposing and respective end surface affixed multi-layered wear and cushioning plugs mounted to reconditioned and opposing ends of first and second joint defining bones; 
         FIG. 1A  is an enlarged inset view of a portion of a lower selected wear plug and illustrating the compressive aspect of the outer hardened layers relative to the softer inner sandwiched layer; 
         FIGS. 2A and 2B  are a pair of lineal cutaway views illustrating the multi layer and inner compressible nature of the joint implantable wear plug; and 
         FIG. 3  is a further cutaway illustration of a further version of implantable end surface plugs illustrating substantially planar width extending inner cushioning layers, each of which are sandwiched between an inner-most hardened and bone mounting base and an opposite, outer facing and likewise hardened plastic which can further exhibit a contoured exterior surface for facilitating seating engagement of an opposing plug end surface. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As previously described, the present invention discloses an end secured (this also including fused) implant device for use with various knee, elbow, hip, shoulder or other joint applications. More particularly, the present invention teaches a multi-layer joint surface implant for use with such as existing bones and which in one non-limiting application exhibits a softer plastic layer encased between outer (upper and lower) hardened plastic layers in order to enhance both cushioning and wear resistance. Additional variants also contemplate constructing the implant of various metal or poly/metal composites and which maximize the durability and wear resistant aspects of the design. 
     Prior to providing a detailed description of joint applications illustrated herein in cutaway, it is understood that they do not include the illustration of such additional components as ligaments, tendons and the like which complete a given joint application and which are understood to be both provided and installed according to known methods and techniques associated with the relevant art. That said, the present invention contemplates the provision of any suitable natural or synthetic ligaments and tendons, and which can further include both existing structure as well as that which can be retrofit designed and/or installed. 
     Referring again to  FIG. 1 , as well as to  FIG. 1A , a first selected knee joint application is illustrated and in which first and second opposing and respective end surface affixed multi-layered wear and cushioning plugs, or three dimensional shaped bodies, are generally shown by upper plug  10  and lower plug  12  respectively, and which are mounted to reconditioned and opposing ends of first/upper  2  and second/lower  4  joint defining bones. The present invention contemplates surgical reconditioning of existing joint defining bones, however it is also envisioned that one or more of the joint plug designs of the present invention can also be integrated into an artificial bone incorporated into the overall implant. 
     As is also shown in the cutaway views of  FIGS. 2A and 2B  each plug is constructed as a multi-layer composite and three dimensional shaped article exhibiting a generally planar and typically non-linear pattern having a specified thickness and including a central softer material layer  14  for plug  10  and  15  for plug  12  (such as exhibiting an undulating or non-linear configuration which matches that of an exterior most facing joint defining surface, this further shown at  23  and  25  respectively for plug bodies  10  and  12 ). Arranged on opposite sides of the central layers  14  and  15  are inner and outer hardened material layers shown at  16  and  18  for plug  10  and at  17  and  19  for plug  12 , respectively. 
     As further shown in  FIG. 1 , the construction of the inner mounting layers  16  of each plug  10  and  12  can include inwardly perimeter extending and inner marrow contacting portions  20  and  22  extending from the inner layers  16  and  17  and such as likewise shown in cutaway in contact with each of upper  2  and lower  4  bones. The contacting portions  20  and  22  may be configured as perimeter enclosing and inserting portions which engage both the inner facing wall surfaces of the bones  2  and  4  (proximate the sectioned end locations  3  and  5  of the bones  2  and  4 ) as well as inner marrow supporting portions  6  and  8 . 
     Inner facing surfaces of the inner layers  16  and  17 , in combination with the associated and perimeter edge defining marrow contacting portions  20  and  22 , each exhibit roughened portions, further depicted at  24  and  26 , and which facilitate bonding of the plug shaped bodies  10  and  12  to their respective sectioned bone ends  2  and  4 . It is also envisioned that a suitable mechanical fastener or chemical adhesive can be employed to secure inwardly facing and annular edge surfaces of the plugs  10  and  12  to the sectioned annular locations  3  and  5 . As previously described, the outer facing hardened plastic (or metal/plastic composite) layers  18  each further exhibit a contoured and joint defining surface profile (see again at  23  for upper plug  10  and at  25  for opposing lower plug  12 ) these generally defining the preferred surface mating contours of each joint defining body which mimics that of the natural joint being replaced. 
     As previously described, the construction of the plugs  10  and  12  (as well as any of those falling within the disclosure of the present invention) can include any of plastic, metal or composite materials which are produced in multi-layer fashion as shown. As further illustrated, the provision of the central softer layers  14  and  15  of material embedded within each wear plug  10  and  12  results in a degree of cushioning/inner compressive dynamic performance, this contributing to increased cushioning response and durability when installed in a dynamic in situ joint application. This is further represented by the directional arrows  27  shown in the inset view of  FIG. 1A  (as well as the compressed position of  FIG. 2A ) and by which each of the inner softer layers  14  and  15  dynamically respond to the exertions of the outer hardened layers  16  &amp;  17  and  18  &amp;  19 , and without sacrificing wear resistance in particular in the opposing and abrading wear zone established between the opposing joint defining surfaces  23  and  25 , as well as to a lesser extent along the bone securing and affixing zone established by the inner hardened layers  16  and  17 . 
     Referring finally to  FIG. 3 , a further cutaway illustration is shown of a further version of implantable end surface plugs, respectively illustrated by upper and lower plugs at  28  and  30 . Each of the plugs are again depicted in cutaway and are understood to each include a substantially planar extending and inner cushioning layer, at  32  and  34  respectively, each of which is sandwiched between an inner-most hardened and bone mounting base layer  36  and  38  and an opposite, outer facing and likewise hardened plastic layer  40  and  42 , this further exhibiting a contoured exterior surface profile, at  44  and  46  (and as compared to  23  and  25  in  FIG. 1 ), for facilitating seating engagement of an opposing plug end surface. 
     The arrangement of  FIG. 3  further illustrates an inner edge concave profile or perimeter contour (see at  48  and  50 ), this further facilitating dynamic cushioning movement and support of the exterior configured hardened plastic layers  40  and  42  relative to the inner and bone/marrow mounted base layers  36  and  38 . It is further understood that the dynamic properties of the plugs can be modified, such as by adjusting the hardness/cushion-ability of the inner and/or outer layers. 
     Although not shown, it is also envisioned that the plugs disclosed herein can be redesigned so as to include multiple alternating layers of hardened/softer material. It is additionally envisioned that the arrangement and pattern of each hard/soft/hard layer interface incorporated into a three dimensional plug design can be modified so as to provide varying dynamic responsiveness to given joint application, and while achieving the dual objectives of maintaining long term durability and wear resistance while at the same time achieving a degree of desired cushioning support within the joint zone. It is further understood that a single plug implant body can be incorporated into a reconditioned and previously damaged bone, this in use with an existing opposing bone exhibiting a natural joint defined surface. 
     Having described my invention, other and additional preferred embodiments will become apparent to those skilled in the art to which it pertains, and without deviating from the scope of the appended claims.