Abstract:
A tibia implant for tightening the patella tendons, has a vertical cross section which in mounted position tapers downward, an essentially vertically arranged base plate which carries a sponge structure, wherein the sponge structure on both sides rests against a respective vertical cut surface of a vertical knee proximal incision of the tibia.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of prior filed U.S. provisional Application No. 61/511,577, filed Jul. 26, 2011, pursuant to 35 U.S.C. 119(e), the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a tibia implant for tightening the patella tendons 
         [0003]    The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention. 
         [0004]    From US 2010/0076564 an implant has become known with which in particular in the veterinary medicine the tendons of a knee can be tightened again. For this, the tibia is split from above in the knee proximal region so that a wedge shaped incision is created. However, the tibia section must not be cleaved off completely. The implant is inserted into the incision so that the tibia section is braced toward the front. The implant is a wire frame which is constructed in the manner of a conductor path structure and is flexible with regard to the wedge angle. After inserting the implant into the tibia incision the implant is bent upwards until the side surfaces of the implant rest against the cut surfaces of the incision. Bending of fastening loops out of the plane of the cut surfaces in the direction of the outer surface of the tibia and the tibia section can now allows fastening the implant to the tibia by means of screws. 
         [0005]    However, it has proven disadvantageous in this case that the implant is much too filigree and incapable of absorbing forces and deforms very rapidly. In addition, the implant is only poorly connected or anchored to the bone. 
         [0006]    DE 10 2005 037 141 A1 discloses an implant which has an open-pore metal sponge as thermoset bone substitute. DE 32 24 265 A1 mentions a method for producing an implant in which a model from continuous open-pore material is used wherein a model material with a three dimensional grid or net structure is used. 
         [0007]    It would therefore be desirable and advantageous to provide an improved tibia implant which is more dimensionally stable and which better grows together with the bone 
       SUMMARY OF THE INVENTION 
       [0008]    According to one aspect of the present invention, a tibia implant for tightening patella tendons, includes a sponge structure and a base plate which carries the sponge structure, wherein at least parts of the sponge structure have a lattice structure, wherein the implant has a tapered vertical cross section and is insertable into a knee proximate incision of a tibia so that two sides of the sponge structure are in one to one abutting relationship with two cut surfaces of the incision. 
         [0009]    The implant according to the invention has the significant advantage that due to the sponge structure which can have any desired pore size and is in particular open-pore, it is very dimensionally stable and can therefore absorb and support very great forces. The sponge structure preferably has a net like, in particular regular structure. 
         [0010]    According to another advantageous feature of the present invention, the base can form a part of the circumferential support frame which encloses the sponge structure. On one hand, the circumferential support frame supports the sponge structure; on the other hand the support frame serves as stable spacer for the tibia section and holds the latter in the desired braced position so that the tendons retain their newly created tightening. 
         [0011]    In a preferred exemplary embodiment the sponge structure has a three dimensional structure. This ensures that the support forces are conducted into the inside of the implant without causing damage to the sponge structure. 
         [0012]    The lattice structure extends over multiple parallel planes. Even when the lattice structure has an imperfection in one plane, the stiffness and rigidity is retained because the support is supported and ensured by the further planes. 
         [0013]    In a preferred embodiment of the tibia implant according to the invention two parallel lattice structure plane are offset by half a lattice width in the x and/or in the y axis. The lattice sections are bent between the lattice points in the direction of the lattice structure plane which is parallel to the lattice sections, so that they contact one another in their bending points. The bent lattice sections do not only define the lattice structure plane but also stiffen the latter relative to the parallel plane. A detailed description is given further below where reference is made to the drawing. 
         [0014]    In order to fasten the implant to the bone as fast and simple as possible at least one vertical side surface of the support frame is provided with at least two projecting fastening loops. These fastening loops are configured flat so that they can support great forces in the loop plane. The fastening loops extend toward the tibia and toward the partially severed tibia section. An optimal fitting is achieved in that the fastening loops project from the support frame horizontally and/or inclined toward the horizontal. In addition, the fastening loops can have one or multiple receiving openings for fastening means such as screws or the like. A hooking engagement is also possible. A fast individual fitting of the implant to the respective bone shape is achieved in that the fastening loops protrude bendable and adjustable from the support frame. 
         [0015]    Preferably the tibia implant according to the invention is made of metal for example stainless steel or titanium, or from plastic, for example PEEK. Alloys of the metal materials or mixtures of the plastics, also material additives such as glass fiber or carbon fiber are conceivable. 
         [0016]    In order to facilitate the anchoring of the implant in the bone, the tibia implant has a coating which supports the attachment of bone mass by growth, for example hydroxyapatite. In addition the spikes protrude over the sponge structure 
         [0017]    These spikes penetrate into the bone surface and prevent a shifting of the tibia implant on the bone. The spikes are smaller in the region of the wedge cut and and/or protrude less out of the sponge structure than on the opposing wider end. Very high forces can be absorbed preferably in that the spikes extend from a sponge structure through the implant and its internal space to the other sponge structure and protrude outwardly over the latter so that the forces can be transferred from the tibia section directly to the tibia. 
         [0018]    A fast growing in of the tibia implant is advantageously facilitated in that the support frame has openings. Bone mass can be introduced into the implant through the openings so that the internal space which is located between the sponge structures overgrows quickly. 
         [0019]    An advantageous manufacturing method provides that the tibia implant is produced by means of a rapid manufacturing method. The implant can be produced in multiple sizes without major constructive changes. 
         [0020]    Further advantages features and details of the invention follow from the sub claims and the following description in which a particularly preferred embodiment is described in detail with reference to the drawing. The features which are shown in the drawing or are mentioned in the description and/or in the claims can be relevant individually or in any combination. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0021]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0022]      FIG. 1  shows a front view on the front side of a knee with an implant which is located in the tibia; 
           [0023]      FIG. 2  shows a side view of a knee taken in the direction of the arrow II according to  FIG. 1 ; 
           [0024]      FIG. 3  shows a first perspective view of the tibia implant; 
           [0025]      FIG. 4  shows a schematic representation of the sponge structure; 
           [0026]      FIG. 5  shows a perspective view of the tibia implant; 
           [0027]      FIG. 6  shows a view taken in the direction of the arrow VI according to  FIG. 1  on the cut of the tibia implant; 
           [0028]      FIG. 7   a  shows a lattice element in perspective view; and 
           [0029]      FIG. 7   b  shows a net constructed from multiple lattice elements 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0030]    Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the drawings are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0031]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown a front view onto a front side of a knee  10 , in particular the lower end of the femur  12 . The anterior cruciate ligament  14  and the posterior cruciate ligament  16  as well as the menisci  18  and the collateral ligament  20  are shown schematically. Beside the tibia  22 , the fibula  24  can be seen. A tibia implant  26  which has an approximately trapeze shaped cross section with a concavely shaped side can be seen in the knee proximal region of the tibia  22 . This tibia implant  26  is located in an incision  28  of the tibia  22  which, as can be seen in  FIG. 2 , is introduced into the tibia  22  essentially vertically from above so that a tibia section  30  is formed whose lower end is still connected to the tibia  22 . The tibia implant  26  is inserted into this V-shaped incision  28  from the side. By bracing the tibia section  30  the anterior ligament  32  is tightened. 
         [0032]      FIG. 3  shows a perspective view of the tibia implant  26  which has a circumferential support frame  34  and a sponge structure  36  located there between. The tibia implant  26  is configured wedge shaped and has a wedge edge  38 . The opposing side  40  does not only have a greater width B but also a greater length L. The tibia implant  26  thus has a trapeze shape, wherein the base plate  44  which has multiple fastening loops  42  is configured even and the opposing side  46  is configured concave. In addition, it can be seen that this concave side  46  is provided with two through openings  48  through which bone material can be inserted into the inside of the tibia implant  26 . In an alternative embodiment, the base plate  44  can be configured concave. 
         [0033]    The sponge structure  36  extends over at least two planes  50  and  52  which is clearly shown in  FIG. 4 . The plane  50  in  FIG. 4  is arranged on top and the plane  52  there underneath. In addition the lattice is shifted in the plane  50  by one lattice width in the x-direction and in the y direction. The lattice sections  56  which extend between the lattice points  54  are bent in the direction of the sponge structure which is parallel to the lattice sections i.e in the direction of the plane  52 . Correspondingly the lattice sections which extend between the lattice points  58  are angled toward the sponge structure which is parallel to the lattice sections  60 , i.e. in the direction of the plane  50 . The lattice sections  56  and  60  contact one another in the bending sites  62 . The sponge structure  36  is thus formed by a three dimensional network which has a multitude of openings, into which the bone can grow. 
         [0034]      FIG. 7   a  shows a single lattice element, which is built between  3  planes. Four lattice rods  54  protrude at equal angular distances from the lattice point  54  towards the next parallel plane. The lattice element is formed by twelve equal lattice rods  55 . In all lattice rods  55  the neutral fiber is the same.  FIG. 7   b  shows a net which is constructed from multiple lattice elements, and which extends in the x-y plane at an angle of 90°. It is shifted in the z-plane by 45°. 
         [0035]      FIG. 5  also shows a perspective view onto the tibia implant  26 , wherein the fastening loops  42  can be clearly recognized. They protrude from the support frame  34  in the plane of the base plate  44  and each have a receiving opening  64  for a not shown fastening screw (bone screw), which is configured as oblong hole which extends transverse to the longitudinal axis  66  of the tibia implant  26 . The base plate  44  is also provided with through openings  68  so that bone material can also be filled into the inside of the tibia implant through the base plate  44 . 
         [0036]      FIG. 6  shows the tibia implant  26  in the direction of the arrow VI according to  FIG. 1  so that the through opening  70  in the wedge edge  38  can be seen clearly. This through opening  70  also serves for filling bone material into the inside of the tibia implant  26 . However, spikes  72  which project out of the sponge structure  36  can also be seen which protrude over the outer contour of the tibia implant  26 . These spikes  72  traverse the entire tibia implant  26  so that the forces which are introduced from the tibia section  30  are directly transferred to the tibia  22 . The tibia implant  26  and in particular the sponge structure  36  is not or only minimally subjected to stress. The spikes  72  are not only shorter in the region of the wedge edge  38  but also have a smaller diameter which facilitates the insertion of the tibia implant  26  into the incision  28 . 
         [0037]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. 
         [0038]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: