Abstract:
A tibial tuberosity advancement implant and method includes a spacer body made of biocompatible, biodegradable material and having a main section with at least one bony growth orifice therethrough and at least one fin extending from the main section by at least one connector. A metal clip is engageable with of the spacer body main section and includes spaced screw holes for securing the spacer body to the advanced tibial tuberosity and the tibia when the implant is placed in the space between the advanced tibial tuberosity and the tibia.

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 14/293,128 filed Jun. 2, 2014, which hereby claims the benefit of and priority thereto under 35 U.S.C. §§119, 120, 363, 365, and 37 C.F.R. §§1.55 and 1.78, which is a divisional of U.S. patent application Ser. No. 13/559,103 filed Jul. 26, 2012 now U.S. Pat. No. 8,790,410, the benefit of and priority thereto claimed under 35 U.S.C. §§119, 120, 363, 365, and 37 C.F.R. §1.55 and §1.78, and both are incorporated herein by this reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to tibial tuberosity advancement procedures in canines. 
     BACKGROUND OF THE INVENTION 
     During the tibial tuberosity advancement procedures in canines, the tibia is cut just behind the tibial tuberosity and the tibial tuberosity is advanced to achieve a perpendicular relationship between the tibial plateau slope and the patella tendon. A titanium or stainless steel implant (also called a cage or spacer) is placed between the advanced tibial tuberosity and the tibia and a plate is used to secure the tibial tuberosity to the tibia. 
     Over time, bony growth forms in and around the spacer. In the case of an infection or other problem, it can be very difficult to remove the spacer. As many as one in ten tibial tuberosity advancement procedures result in infection or rejection of the spacer implant. 
     Biocompatible and biodegradable materials are known for use in implants but an implant made of a plastic biodegradable material and designed like prior art metal implants may not be strong enough to maintain the tibial tuberosity in the advanced state as the canine recovers and becomes active. Injection molding limitations also prevent manufacturing a plastic implant designed like the prior art metal tibial tuberosity implant. 
     SUMMARY OF THE INVENTION 
     In one or more aspects of a preferred embodiment of the invention, a trimable tibial tuberosity advancement implant is molded using a biocompatible, biodegradable material so that in case of infection or the like only the metal clip portion of the implant need be removed (using, for example, minimal invasive surgery techniques). And yet, the implant spacer body is structurally sound until decomposition and bony ingrowth occurs between the advanced tibial tuberosity and the tibia. 
     Featured is a tibial tuberosity advancement implant comprising a spacer body made of biocompatible, biodegradable material. A main section has at least one bony growth orifice therethrough. At least one fin extends from the main section by at least one connector. A clip is engageable with the main section and includes spaced screw holes for securing the spacer body to the advanced tibial tuberosity and the tibia when the spacer body is implanted. 
     The clip is usually made of stainless steel or titanium. It preferably includes spaced ears each having a screw hole and upper and lower spaced spring arms interconnecting the spaced ears. Each spring arm then includes an outwardly curved portion including a central cut out and the spacer body main section slot includes spaced upper and lower tabs each received in a cut out of the clip. 
     The typical biocompatible, biodegradable material used includes polyglycolic acid and/or polylactic acid. Preferably, the spacer body main section includes at lease two spaced bony growth orifices, the spacer body main section has an isosceles trapezoid cross sectional shape, the fins are angled inwardly rendering the top of the implant longer and wider than the bottom and there is a top and a bottom cuttable connector for each fin to customize the length of the implant. 
     One example of a tibial tuberosity advancement implant in accordance with the invention includes a spacer body made of biocompatible, biodegradable material and including a main section having an isosceles trapezoid cross sectional shape with at least one bony growth orifice therethrough and a proximal slot. Inwardly angled fins extend from the main section rendering the top of the implant longer than the bottom. A clip is slideable into the proximal slot of the main section and includes spaced screw holes for securing the spacer body to the advanced tibial tuberosity and the tibia. 
     Another tibial tuberosity advancement implant made of biodegradable material includes a proximal face, a slot behind the proximal face for a metal clip, distal spaced cuttable fins, and bony growth orifices in a main body section between the proximal face and the distal fins. Typically, the implant is longer and wider at the top than at the bottom and the body section is configured as an approximation of a concrete block. 
     This invention also features a method comprising advancing the tibial tuberosity of a canine, implanting a biodegradable spacer to retain the tibial tuberosity in an advanced position, fixing the implant using a metal non-biodegradable clip connected to the spacer, promoting bony in-growth and degradation of the biodegradable spacer, and removing the metal non-biodegradable clip in the case of an infection or other problem. 
     The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Other objects, features, and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which: 
         FIG. 1  is a schematic three dimensional side view of an implant between an advanced tibial tuberosity and the tibia of a canine; 
         FIG. 2  is a schematic three dimensional side view of an example of a preferred version of a biodegradable implant in accordance with the invention; 
         FIG. 3  is a schematic bottom view of the implant shown in  FIG. 2 ; 
         FIG. 4  is a schematic front view of an example of the clip portion of an implant in accordance with the invention; 
         FIG. 5  is a schematic front view of the implant of  FIGS. 2-3  with the clip of  FIG. 4  inserted therein. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows implant  10  used in a tibial tuberosity advancement procedure in accordance with the invention along with plate  12 . Implant  10  is preferably injection molded using a biocompatible, biodegradable plastic material such as polyglycolic acid and/or polylactic acid. It may also include bone growth proteins and the like. Initially, implant  10  is structurally sound and correctly spaces the advanced tibial tuberosity  14  from the tibia  16  while the canine is recuperating and thereafter active. The implant has features which promote bony growth between the advanced tibial tuberosity and the tibia which over time fills space  18 . Thereafter, the implant degrades and dissolves. 
     Thus, in the case of infection, rejection, or some other problems requiring removal of the implant, all that need be removed are the two screws and the metal clip portion of the implant. Minimally invasive surgical techniques can be used. In the prior art, as explained in the Background section above, the titanium or stainless steel implant was secured in the space  18  by bony growth and was very difficult to remove. Minimally invasive surgical techniques could not be used. 
     One preferred version of the implant is shown in  FIGS. 2-5 . Structurally strong spacer body  20 ,  FIGS. 2-3 , is made of biocompatible, biodegradable material and includes main section  22  and distal fins  24   a  and  24   b . Main section  22  has proximal slot  26  for clip  28 ,  FIG. 4 . Main section  22  also has bony growth orifices  30   a  and  30   b  therethrough designed to promote bone growth therein and around the implant. Section  22  somewhat mimics the configuration of a concrete block. Spaced fins  24   a  and  24   b  are also designed to promote bony growth in the space between main section  22  and fin  24   a  and in the space between fin  24   a  and fin  24   b . Also, top and bottom connectors  32   a  and  32   b  (connecting fin  24   a  to main section  22 ) and top and bottom connectors  32   c  and  32   d  (connecting fin  24   b  to fin  24   a ) can be cut, as desired, to shorten the length of the implant for different size canines. 
     With both fins intact, the implant is 27 mm long; with fin  24   b  cut off, the implant is 24 mm long; and with both fins  24   a  and  24   b  cut oft the implant is 21 mm long. In this way, one mold is effectively able to produce three different length implants. Other sizes are possible. Different width cages are possible. 
     Fins  24   a  and  24   b  as well as distal wall  36  of main section  22  are angled inwardly at 25° with respect to vertical resulting in an implant with a shorter bottom surface  40   a  and a longer top surface  40   b ,  FIGS. 3 and 5 . Spacer body main section  22  also has an isosceles trapezoid cross sectional shape as does proximal face  50  (see  FIG. 5 ) and fins  24   a  and  24   b . As a result, the top of the implant is wider and longer than the bottom. The implant thus conforms to the shape of the space between the tibia and the advanced tibial tuberosity. 
     In one example, the implant was 27 mm long at the top, 22 mm long at the bottom, 9 mm wide at the top, and 7 mm wide at the bottom. Fin connectors  32  were 2.1 by 6 by 1.2 mm. Slot  26  behind proximal face  50  was 1.2 mm wide. 
     Preferably, stainless steel or titanium 1 mm thick clip  28 ,  FIG. 4  has spaced ears  70   a  and  70   b  each with a screw hole  72   b  and  72   b , respectively. Curved upper  74   a  and lower  74   b  spring arms interconnect the ears  70 . Each spring arm  74  includes central cut out  76   a ,  76   b  that receive therein centered tabs connecting proximal face  50 ,  FIGS. 2-3  to main section  22 . Bottom tab  78   a  is shown in  FIG. 3  and top tab  78   b  is shown in  FIG. 2 . The clip spring arm cutouts are wider than the thickness of the tabs so clip  28  can be rotated slightly with respect to the spacer body. When clip  28  is inserted into spacer body slot  26 , spring arms  74   a  and  74   b  are compressed towards each other. After insertion, the upper and lower tabs retained in the cutouts retain the clip in the spacer body. 
     Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. 
     In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant can not be expected to describe certain insubstantial substitutes for any claim element amended. 
     Other embodiments will occur to those skilled in the art and are within the following claims.