Abstract:
Disclosed is a prosthesis configuration and method for treating acquired flatfoot. The assembly includes a longitudinal piece extending into two foot bones. The piece is positioned such that a maximum force, in the piece, is a tension force when the foot is under a standing load. The piece may be a flexible cable, for example.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to medical devices and, more particularly, to an apparatus and method for treating acquired flatfoot. 
     2. Description of Related Art 
     Many adults develop a painful breakdown and deformity of the arch of the foot. Procedures to correct this deformity have required cutting and realigning or fusing bones in the foot. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an apparatus configuration and method for treating acquired flatfoot, while minimizing the need to fuse bones in the foot. 
     To achieve this object of the present invention, a prosthesis assembly comprises a longitudinal member configured to extend into a first foot bone and into a second foot bone, the longitudinal member defining a length between the first and second bones, the first and second foot bones being separated by a third foot bone, the longitudinal member being positioned and oriented such that a maximum force is a tension force when the foot is under a standing load, wherein the first bone has a first side, and a second side opposing the first side, the longitudinal member is configured to extend into the first bone from the first side, the longitudinal member defines a flange, and the prosthesis assembly further includes a plate on the second side, the plate being engaged with the flange, wherein the longitudinal member extends through the plate. 
     According to another aspect of the present invention, a prosthesis configuration comprises limiting means configured to extend into a first foot bone and into a second foot bone, the first and second foot bones being separated by a third foot bone, such that a maximum force is a tension force when the foot is under a standing load, wherein the first bone has a first side, and a second side opposing the first side, the limiting means is configured to extend into the first bone from the first side, the limiting means defines a flange, and the prosthesis assembly further includes a plate on the second side, the plate being engaged with the flange, wherein the limiting means extends through the plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of an apparatus for treating flatfoot in accordance with a first embodiment of the present invention. 
     FIG. 2 is a perspective, partial view corresponding to FIG.  1 . 
     FIG. 3 is a view of an element of the first preferred apparatus. 
     FIG. 4A is a view of another element of the first preferred apparatus. 
     FIG. 4B is a view taken along the line  4 B— 4 B in FIG.  4 A. 
     FIG. 5A is a view of yet another element of the first preferred apparatus. 
     FIG. 5B is a view taken along the line  5 B— 5 B in FIG.  5 A. 
     FIG. 6A is a view of yet another element of the first preferred apparatus. 
     FIG. 6B is a view taken along the line of  6 B— 6 B in FIG.  6 A. 
     FIG. 7A is a view of yet another element of the first preferred apparatus. 
     FIG. 7B is a view taken along the line  7 B— 7 B in FIG.  7 A. 
     FIG. 8 is a side view of an apparatus for treating flatfoot in accordance with a second embodiment of the present invention. 
    
    
     The accompanying drawings which are incorporated in and which constitute a part of this specification, illustrate embodiments of the invention and, together with the description, explain the principles of the invention, and additional advantages thereof. Throughout the drawings, corresponding parts are labeled with corresponding reference numbers. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 show prosthesis configuration  1  including anchor assembly  5  on first metatarsal bone  4 , anchor assembly  25  on heel bone  24 , and cable assembly  70  coupled between anchor assemblies  5  and  25 . Anchor assembly  5  includes backing plate  6  and tube  14  integrally connected with plate  6 . Tube  14  is located in bone through-hole  16  defined in first metatarsal bone  4 . Plate  6  defines a contour that fits a contour of bone  4 , to distribute load transmitted from flexible, metal cable  72  over the surface of bone. In this patent application, the term “cable” means a plurality of filaments or lines attach along the longitudinal dimension by twisting or braiding. 
     Plate  6  defines holes  7  and  8 . Bone screw  10  is screwed into bone  4  via hole  7 , and bone screw  12  is screwed into bone  4  via hole  8 . 
     FIGS. 1 and 2 also show fibula bone  50  and other bones  51 . 
     Anchor assembly  25  includes backing plate  26  and tube  34  integrally connected with plate  26 . Tube  34  is located in bone through-hole  17  defined in bone  24 . Plate  26  defines a contour that fits a contour of bone  24 , to distribute load transmitted from flexible, metal cable  76  over the surface of bone  24 . Plate  26  defines holes  27  and  28 . 
     Flexible, metal cable  72  is engaged with assembly  5  through tube  14 . Flexible, metal cable  72  has stop  73  fixed to the end of cable  72 . Stop  73  acts as a type of flange to prevent cable  72  from slipping out of tube  14 . 
     Flexible, metal cable  72  is attached to flexible, metal cable  76  via compressible sleeve  78 . Flexible, metal cable  76  is engaged with anchor assembly  25  via tube  34 . 
     As shown in FIG. 3, Flexible, metal cable  76  has stop  77  fixed to the end of cable  76 , to prevent cable  76  from slipping out of tube  34 . Cable  76  includes metallic filament  84  and metallic filament  85 . The longitudinal dimension of filament  84  is attached to the longitudinal dimension filament  85 , by twisting. 
     As shown in FIG. 1, anchor assembly  55  is on navicular bone  22 , anchor assembly  35  is on tibia bone  23 , and cable assembly  90  is coupled between anchor assemblies  55  and  35 . Anchor assembly  55  includes backing plate  56  and curved tube  64  integrally connected with plate  56 . Plate  56  defines a contour that fits a contour of bone  22 , to distribute load transmitted from flexible, metal cable  92  over the surface of bone  22 . Plate  56  defines holes  57  and  58 . 
     Tube  64  is located in curved, bone through-hole  19  defined in navicular bone  22 . Tube  64  has a constant radius of curvature, allowing tube  64  to be guided through through-hole  19 . 
     Anchor assembly  35  includes backing plate  36  and curved tube  44  integrally connected with plate  36 . Tube  44  is located in bone through-hole  18  defined in tibia bone  23 . Plate  36  defines a contour that fits a contour of bone  23 , to distribute load transmitted from flexible, metal cable  96  over the surface of bone  23 . Plate  36  defines holes  37  and  38 . Bone screw  40  is screwed into bone  23  via hole  37 , and bone screw  42  is screwed into bone  23  via hole  38 . 
     Flexible, metal cable  92  is engaged with assembly  55  through tube  64 . Flexible, metal cables  92  and  82  share a common tube  64 . Flexible, metal cable  82  has stop  87  fixed to the end of flexible, metal cable  82 . Stop  87  acts as a type of flange to prevent flexible, metal cable  82  from slipping out of tube  64 . Flexible, metal cable  92  has a stop (not shown in FIG. 1) fixed to the end of cable  92 . The stop at the end of flexible, metal cable  92  acts as a type of flange to prevent cable  92  from slipping out of tube  64 . 
     Flexible, metal cable  92  is attached to flexible, metal cable  96  via compressible sleeve  98 . 
     Flexible, metal cable  96  and flexible, metal cable  102  share a common tube  44 . Flexible, metal cable  96  is engaged with anchor assembly  35  via tube  44 . Flexible, metal cable  96  has stop  97  fixed to the end of cable  96 . Stop  97  acts as a type of flange to prevent flexible, metal cable  96  from slipping out of tube  44 . Flexible, metal cable  102  has stop  103  fixed to the end of cable  102 . Stop  103  acts as a type of flange to prevent flexible, metal cable  102  from slipping out of tube  44 . 
     Each cable assembly in the prosthesis is inside of the body, under the skin. 
     Referring to FIG. 1, the foot is under a load F L  of 50 pounds or more as when, for example, the person is standing up. F L , which is a type of standing load, is delivered to the foot via tibia  23  and fibula  50 . Cable assembly  70  extends into metatarsal  4  and heel  24 . Cable assembly  70  defines a length between position  67  on assembly  70  and position  68  on assembly  70 . Cable assembly  70  is positioned and oriented such that a maximum force, on most of this length, is a tension force, meaning that the force is directed along the length of cable assembly  70 . Although pressure from body tissue or bone may cause a force F N  perpendicular to cable assembly  70 , on most of the length, F T  is greater then F N . 
     With the load F L , each cable assembly has a tension force that is the maximum force on most of the length of the cable assembly between the two anchor bones of the assembly, as described above in connection with assembly  70 . 
     Prosthesis configuration  1  is assembled to restore the arch and prevent its future collapse. More specifically, to assemble prosthesis  1 , first make bone through-holes  16 ,  19 ,  17 , and  18  in metatarsal bone  4 , navicular bone  22 , heel bone  24 , and tibia bone  23 , respectively. Next, attach assembly  5  to bone  4  by placing tube  14  in through-hole  16 , screwing screw  10  into bone  4  via hole  7 , and screwing screw  12  into bone  4  via hole  8 . Attach assembly  25  to bone  24  by placing tube  34  in through-hole  17 , screwing a screw (not shown) into bone  24  via hole  27 , and screwing a screw (not shown) into bone  24  via hole  28 . Attach assembly  55  to bone  22  by placing tube  64  in through-hole  19 , screwing screw  60  into bone  22  via hole  57 , and screwing screw  61  into bone  22  via hole  58 . Attach assembly  35  to bone  23  by placing tube  44  in through-hole  18 , screwing screw  40  into bone  23  via hole  37 , and screwing screw  42  into bone  23  via hole  38 . 
     Next, pass distal end  75  of flexible, metal cable  72  through tube  14  and pass distal end  79  of flexible, metal cable  76  through tube  34 . Align distal end  75  with distal end  79  and surround distal ends  75  and  79  with compressible sleeve  78 . Compress compressible sleeve  78  to fix the movement of distal end  75  relative to distal end  79 , thereby setting the length of cable assembly  70 . In setting the length of cable assembly  70 , tension cable assembly  70  appropriately to correct the deformity, by pulling the forefoot and heel into a slightly over arched position, such that, when the foot bears load, the proper longitudinal arch is established. Thus, cable assembly  70  extends from heel bone  24  to metatarsal bone  4 , under cuboid bone  20 , navicular bone  22  and talus bone  21 . 
     In other words, assembly  70  extends into bone  4  and extends into bone  24 . Bones  4  and  24  are separated by bone  20 . Bones  4  and  24  are also separated by bone  22 . Bones  4  and  24  are also separated by bone  21 . Assembly  70  is positioned and oriented such that, in loaded tension, a maximum force is a tension force when the foot is under a standing load. 
     Pass distal end  99  of flexible, metal cable  92  through tube  64  and pass distal end  93  of flexible, metal cable  96  through tube  44 . Align distal end  99  with distal end  93  and surround distal ends  99  and  93  with compressible sleeve  98 . Compress compressible sleeve  98  to fix the movement of distal end  99  relative to distal end  93 , thereby setting the length of cable assembly  90 . In setting the length of cable assembly  90 , tension cable assembly  90  to correct forefoot abduction. Thus, cable assembly  90  extends from tibia bone  23  to navicular bone  22  on the inboard side of talus bone  21 . 
     Pass distal end  104  of flexible, metal cable  102  through tube  44  and pass distal end  109  of flexible, metal cable  106  through tube  34 . Align distal end  104  with distal end  109  and surround distal ends  104  and  109  with compressible sleeve  108 . Compress compressible sleeve  108  to fix the movement of distal end  104  relative to distal end  109 , thereby setting the length of cable assembly  100 . In setting the length of cable assembly  100 , tension cable assembly  100  to correct hind foot valgus, to restore heel  24  to neutral alignment. Thus, cable assembly  100  extends from tibia bone  23  to heel bone  24  on the inboard side of talus bone  21 . 
     Pass distal end  83  of flexible, metal cable  82  through tube  64  and pass distal end  89  of flexible, metal cable  86  through tube  34 . Align distal end  83  with distal end  89  and surround distal ends  83  and  89  with compressible sleeve  88 . Compress compressible sleeve  88  to fix the movement of distal end  83  relative to distal end  89 , thereby setting the length of cable assembly  80 . In setting the length of cable assembly  80 , tension cable assembly  80  to correct forefoot valgus, restoring neutral alignment of the forefoot. Thus, cable assembly  80  extends from navicular bone  22  to heel bone  24  under talus bone  21 . 
     Thus, flexible, metal cables  76 ,  86 , and  106  share tube  34 . 
     FIG. 4A shows a front view of anchor assembly  5 , and FIG. 4B shows a cross-sectional view corresponding to the line  4 B— 4 B in FIG.  4 A. 
     FIG. 5A shows a front view of anchor assembly  35 , and FIG. 5B shows a cross-sectional view corresponding to the line  5 B— 5 B in FIG.  5 A. 
     FIG. 6A is a front view anchor assembly  55 , and FIG. 6B shows a cross-sectional view corresponding to the line  6 B— 6 B in FIG.  6 A. 
     FIG. 7A shows a front view of anchor assembly  25 , and FIG. 7B shows a cross-sectional view corresponding to the line  7 B— 7 B in FIG.  7 A. 
     Each of flexible, metal cables  72 ,  76 ,  92 ,  96 ,  82 ,  86 ,  102 , and  106  is 7×19 stainless cable. These cables may also be another flexible material, such as braided Spectra or Kevlar. 
     In summary, the preferred prosthesis includes flexible cables with end stops already swaged (permanently affixed) in place, anchor assemblies of appropriate shape and fitted with a rigidly fixed (e.g. welded) tube shaped variously for different bones, and compressible metal sleeves. Appropriate bones are drilled to accommodate the tubular portion of the backing plate. The assembly plates are applied to these bones. A flexible cable with end stop has then been passed through each plate and the appropriate cables are connected together with a compressible sleeve under appropriate tension. 
     With the cables pulled in appropriate tension, a more appropriate anatomic relationship of the foot is established. The patient may be able to bear weight soon after surgery since the device does not depend on healing for its stability. 
     The backing plates may also include a porous coating on the undersurface of the plate to allow bone ingrowth to the plate. 
     FIG. 8 shows prosthesis configuration  1 ′ in accordance with a second embodiment of the present invention. Prosthesis configuration  1 ′ including anchor assembly  5 ′ on first metatarsal bone  4 , anchor assembly  25 ′ on heel bone  24 , and cable assembly  70 ′ coupled between anchor assemblies  5 ′ and  25 ′. Anchor assembly  5 ′ includes backing plate  6 ′ and tube  14 ′ integrally connected with plate  6 ′. Tube  14 ′ is located in bone through-hole  16 ′ defined in first metatarsal bone  4 . Plate  6  defines a contour that fits a contour of bone  4 , to distribute load transmitted from flexible, metal cable  72  over the surface of bone  4 . 
     Anchor assembly  25 ′ includes backing plate  26 ′ and tube  34 ′ integrally connected with plate  26 ′. Tube  34 ′ is located in bone through-hole  17 ′ defined in bone  24 . Plate  26 ′ defines a contour that fits a contour of bone  24 , to distribute load transmitted from flexible, metal cable  76  over the surface of bone  24 . Plate  26 ′ defines holes  27 ′ and  28 ′. 
     Flexible, metal cable  72  is engaged with assembly  5 ′ through tube  14 ′. Flexible, metal cable  72  has stop  73 ′ fixed to the end of cable  72 . Stop  73 ′ acts as a type of flange to prevent cable  72  from slipping out of tube  14 ′. 
     Flexible, metal cable  72  is attached to flexible, metal cable  76  via block  115 . More specifically, block  115  defines holes  112  and  114 . Cable  72  is passed hole  112  and engaged with hole  112  via a mechanism such as a screw, for example. Cable  76  is engaged with hole  114  to adjust the tension of cable assembly  70 ′. 
     Flexible, metal cable  76  is engaged with anchor assembly  25 ′ via tube  34 ′. 
     Anchor assembly  55 ′ is on navicular bone  22 . Anchor assembly  55 ′ includes backing plate  56 ′ and curved tube  64 ′ integrally connected with plate  56 ′. 
     Flexible, metal cable  82  is engaged with assembly  55 ′ through tube  64 ′. Flexible, metal cable  82  has stop  83 ′ fixed to the end of cable  82 . Stop  83 ′ acts as a type of flange to prevent cable  82  from slipping out of tube  64 ′. 
     Flexible, metal cable  82  is attached to flexible, metal cable  86  via block  117 . Block  117  defines holes  116  and  118 . Cable  82  is passed hole  116  and engaged with hole  116  via a mechanism such as a screw, for example. Cable  86  is engaged with hole  118  to adjust the tension of cable assembly  80 ′. 
     Flexible, metal cable  86  is engaged with anchor assembly  25 ′ via tube  34 ′. 
     Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or the scope of Applicants&#39; general inventive concept. The invention is defined in the following claims.