Abstract:
A wrist arthroplasty system comprising a carpal implant for resurfacing carpal bones that is at least substantially arcuate in shape from a first end to a second end. The carpal implant includes a first carpal engaging surface, a second carpal engaging surface, a first carpal articulating surface, and a second carpal articulating surface. The first carpal engaging surface has an arcuate concave shape that at least substantially corresponds to a natural shape of a scaphoid bone. The second carpal engaging surface at least substantially corresponds to a natural shape of a lunate bone. The first carpal articulating surface is opposite to the first carpal engaging surface. The first carpal articulating surface has an arcuate convex shape. The second carpal articulating surface is opposite to the second carpal engaging surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/749,766, filed on Jan. 24, 2006. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure generally relates to orthopedic implants. In particular, the present disclosure relates to a wrist arthroplasty system. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Current total joint replacement implants for the wrist require removing large sections of bone and soft tissues due to the large size of the implants. Current implants also require bone purchase or bone cement for stability. Further, implantation of current wrist implants requires making large incisions in the patient to provide the surgeon with the access required to ensure proper alignment of the implants. 
     Consequently, patients can experience long operating room times, lengthy recovery, and reduced mobility. Revision surgeries are challenging because substantial bone has been removed, and there may not be a salvage procedure other than fusion of the joint. Partial wrist replacements still require bone removal and soft tissue damage during surgery, leading to joint instability and few revision options. 
     Thus, there is a need for an implant system that treats all or a portion of the joint surface with minimal damage to bone or soft tissues, yet is mechanically stable and secure to the bone. 
     SUMMARY 
     The present disclosure provides for a wrist arthroplasty system comprising a carpal implant for resurfacing carpal bones that is at least substantially arcuate in shape from a first end to a second end. The carpal implant includes a first carpal engaging surface, a second carpal engaging surface, a first carpal articulating surface, and a second carpal articulating surface. The first carpal engaging surface has an arcuate concave shape that at least substantially corresponds to a natural shape of a scaphoid bone. The second carpal engaging surface at least substantially corresponds to a natural shape of a lunate bone. The first carpal articulating surface is opposite to the first carpal engaging surface. The first carpal articulating surface has an arcuate convex shape. The second carpal articulating surface is opposite to the second carpal engaging surface. 
     The present disclosure further provides for a wrist arthroplasty system comprising a carpal implant and a radial implant. The carpal implant is for resurfacing carpal bones and has a concave, arcuate carpal engaging surface that at least substantially corresponds to the natural shape of carpal bones and a convex, arcuate carpal articulating surface that is opposite to the engaging surface. The radial implant is for resurfacing a radius bone having a concave, radial articulating surface operable to articulate with the carpal articulating surface. A convex radial engaging surface is opposite to the radial articulating surface. A first radial stabilizing fin extends from the radial engaging surface. 
     The present disclosure also provides for a wrist arthroplasty system comprising a unitary carpal implant and a unitary radial implant. The unitary carpal implant has a main carpal body with a carpal engaging surface on a first side of the main body and a carpal articulating surface on a second side of the main body. The first side is opposite to the second side. The unitary radial implant has a main radial body with a radial engaging surface on a first side of the main radial body and a radial articulating surface on a second side of the main radial body. The first side is opposite to the second side. The carpal articulating surface articulates directly with the radial articulating surface. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  illustrates bones of a typical human wrist; 
         FIG. 2A  illustrates an upper surface of a radial implant according to the present teachings; 
         FIG. 2B  is a plan view of the radial implant of  FIG. 2A ; 
         FIG. 2C  is a side view of the radial implant of  FIG. 2A ; 
         FIG. 3  is a plan view of an additional radial implant in accordance with the present teachings; 
         FIG. 4  is a plan view of a further radial implant in accordance with the present teachings; 
         FIG. 5  is a plan view of another radial implant in accordance with the present teachings; 
         FIG. 6A  is a plan view of a carpal implant in accordance with the present teachings; 
         FIG. 6B  is a bottom view of the carpal implant of  FIG. 6A ; 
         FIG. 6C  is a side view of the carpal implant of  FIG. 6A ; 
         FIG. 7  is a plan view of an additional carpal implant in accordance with the present teachings; 
         FIG. 8  is a plan view of a further carpal implant in accordance with the present teachings; 
         FIG. 9A  is a plan view of another carpal implant in accordance with the present teachings; 
         FIG. 9B  is a bottom view of the carpal implant of  FIG. 9A ; 
         FIG. 9C  is a side view of the carpal implant of  FIG. 9A ; 
         FIG. 10  illustrates the preparation of the wrist joint of  FIG. 1  to receive a carpal and/or radial implant according to the present teachings; 
         FIG. 11  is a side view of the radius and scaphoid of the human wrist of  FIG. 1  prepared in accordance with the present teachings to receive a radial implant in accordance with the present teachings and a carpal implant in accordance with the present teachings; 
         FIG. 12  is a cross-sectional view of the radial implant of  FIG. 5  implanted in the radius; 
         FIG. 13  is a cross-sectional view of the carpal implant of  FIG. 6A  implanted in the wrist of  FIG. 1 ; 
         FIG. 14  illustrates the carpal implant of  FIG. 9A  and the radial implant of  FIG. 3  implanted in the wrist of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
       FIG. 1  illustrates the primary bones of a human forearm and wrist. The bones of the forearm include a radius  1  and an ulna  4 . The radius  1  articulates against a scaphoid bone  2  and a lunate bone  3 , which are each carpal bones. Joint space  5  is defined as an area between the radius  1  and the carpal bones  2  and  3 , or between the articulating surfaces of the implants described herein for the radius  1  or carpal bones  2  and  3 . 
       FIG. 2  illustrates a resurfacing implant for the radius  1 .  FIG. 2A  illustrates an articulating surface  102 A of a radial implant  100 A. The radial implant  100 A can have tapered edges to prevent sharp contact with soft tissue.  FIG. 2B  illustrates a frontal plan view of the radial implant  100 A, the articulating surface  102 A, and the static surface  101 A.  FIG. 2C  is a side view of the radial implant  100 A, illustrating a stabilizing fin  150 A that fits into the radius  1 . 
     The articulating surface  102 A has at least one generally concave surface facing the joint space  5 , and can have one or more points of concavity generally shaped and oriented to match the carpal bones  2  and  3 . The static surface  101 A contacts the cartilage, bone, or tissue of the radius  1 , and is shaped to generally fit within the radius  1 . The static surface  101 A can also have a more consistent shape that could be cut or reamed into the radius  1 . An additional component can be a polymer or bone cement layer between the static surface  101 A and the radius  1  to fill voids and provide a more uniform contacting surface. 
     The stabilizing fin  150 A can be a fixed component of the radial implant  100 A or a separate attachment connected during assembly of the implant  100 A. The stabilizing fin  150 A can also be inserted into the intramedullary canal. In another embodiment, the fin  150 A can transition into a rod that secures in the intramedullary canal. In another embodiment, the intramedullary rod can be secured directly to the radial implant. 
       FIG. 3  illustrates an additional embodiment of the radial implant  100 A at reference numeral  100 B. The articulating surface  102 B can have a smooth, generally concave surface without specific contours for the carpal bones. Other embodiments include prongs or hooks extending from or near the articulating surface  102 B dorsally or anteriorly to wrap around the distal aspect of the radius  1 . Dorsally, the prongs or hooks can be aligned between ligaments, including but not limited to the radioscapholapitate ligament, the short radiolunatea ligament, the long radiolunate ligament, and the ulnal lunate ligament. The stabilizing fin  150 B can have cutouts  151 B to allow a mechanical lock when bone or tissue grows into the cutouts  151 B. Alternatively, the cutouts  151 B can be filled with bone paste, absorbable polymers, collagen, or any other substance to facilitate bone growth. Alternatively, the stabilizing fin  150 B can be porous, coated, or otherwise textured to facilitate bone growth, such as applying a titanium using plasma spray or sintered beading, or applying a ceramic or polymer coating. 
       FIG. 4  illustrates an additional embodiment of the radial implant at  100 C. The radial implant  100 C includes a first stabilizing fin  150 C′ and a second stabilizing fin  150 C″ spaced apart from the first stabilizing fin  150 C′. The first and second stabilizing fins  150 C′ and  150 C″ are positioned to engage strong bone in the radius  1 , such as the cortical shell. The stabilizing fins  150 C′ and  150 C″ can be tapered to transition forces from the radial implant  100 C into the radius  1 . One or more support members can connect the stabilizing fins  150 C′ and  150 C″ to provide additional stability. 
       FIG. 5  illustrates an additional embodiment of the radial implant at  100 D. The radial implant  100 D includes a protrusion  103 D for articulation between the radius  1  and ulna  4 . The protrusion  103 D can function as a spacer between the radius  1  and ulna  4  when there is arthritis or damage at this joint. Alternatively, the protrusion  103 D can secure to the ulna  4  or a separate implant in the ulna  4  and have a hinge or pivoting mechanism to allow motion between the radius  1  and ulna  4 . Alternatively, the protrusion  103 D can be any attachment feature for ulna implants. 
       FIG. 6  illustrates a resurfacing implant for the carpal bones  3  and  4  of the wrist joint at reference numeral  200 A.  FIG. 6A  illustrates a frontal plan view of the carpal implant  200 A having an articulating surface  202 A and a static surface  201 A. The carpal implant  200 A can have tapered edges to prevent sharp contact with soft tissues.  FIG. 6B  illustrates a bottom view of the articulating surface  202 A.  FIG. 6C  is a side view of the carpal implant  200 A illustrating a spacer  230 A sized to fit between the scaphoid  2  and the lunate  3 . 
     The articulating surface  202 A has at least one generally convex surface facing the joint space  5 , and can have one or more points of convexity generally shaped and oriented to match the radius  1 . The static surface  201 A can contact the cartilage, bone, or tissue of the carpal bones  2  and  3 , and is shaped to generally fit the carpal bones  2  and  3 . An additional component, such as a polymer or bone cement layer can be positioned between the static surface  201 A and the radius  1  to fill voids and provide a more uniform contacting surface. 
     The static surface  201 A and the spacer  230 A maintain stability by being shaped to closely fit the carpal bones  2  and  3 . In another embodiment, the spacer  230 A has one or more holes to facilitate alignment of stabilizing pins, rods, or screws. In another embodiment, the static surface  201 A or spacer  230 A are porous or coated with a porous material to facilitate bone growth for stability. In yet another embodiment, the static surface  201 A has a shape that could be cut or reamed into the carpal bones  2  and  3  for a precise fit. 
       FIG. 7  illustrates an additional embodiment of the carpal implant  200 A at reference numeral  200 B. The carpal implant  200 B includes an articulating surface  202 B that has one generally convex surface that can be shaped to fit the radius of the radial implant  100 . The spacer  230 B can be used to separate the scaphoid  2  and lunate  3 . In another embodiment, the spacer  230 B can contour along the carpal bones but not enter the joint space between the scaphoid and lunate. In another embodiment, the spacer  230 B can be omitted. In another embodiment, the carpal implant  200 B can be sized to fit only one carpal bone. 
       FIG. 8  illustrates another embodiment of the carpal implant  200 A at reference numeral  200 C. The carpal implant  200 C includes a stabilizing component  203 C that secures one or more edges of one or more carpal bones to help secure the carpal implant  200 C. The stabilizing component  203 C can have holes or cutouts for rods, pins, or screws that secure to the carpal bones. 
       FIG. 9  illustrates an additional embodiment of the carpal implant  200 A at reference numeral  200 D. The carpal implant  200 D includes a stabilizing fin  250 D.  FIG. 9A  is a frontal plan view illustrating the stabilizing fin  250 D that would enter the scaphoid  2 . The stabilizing fin  250 D has one or more cutouts  251 D for stability from bone or tissue growth. In another embodiment, the fin  250 D is textured or porous, or coated with a textured or porous material. In another embodiment, the fin  250 D is smooth.  FIG. 9B  illustrates a bottom view of the carpal implant  200 D articulating surface  202 .  FIG. 9C  illustrates a side view of the carpal implant  200 D with the stabilizing fin  250 . 
       FIG. 10  illustrates a reaming device  300  to prepare the radius  1  and the carpal bones  2  and  3  to receive one of the radial implants  100 A-D and/or one of the carpal implants  200 A-D. The reaming device  300  is textured to remove cartilage or other tissues. In the embodiment illustrated, the reaming device  300  is shaped to create a single radius of curvature for both the radius  1  and carpal bones  2  and  3 . In another embodiment, the reaming device  300  can create multiple points of curvature. In another embodiment, the reaming device  300  can be designed with texture only on certain areas, allowing the surgeon to prepare only the radius  1 , or only the carpal bones  2  and  3 , or only one carpal bone, or a combination thereof. 
       FIG. 11  illustrates a side view of the radius  1  and scaphoid  2  with a slot  410  cut for the stabilizing fins  150  and  250  to enter the radius  1  and scaphoid  2 . Alignment of the slot  410  is controlled by a fixture or jig that can be oriented using alignment holes  420 . A saw can create the slot  410  to receive the implants  100 A-D and  200 A-D. An additional component can be pre-shaped bone graft or bone growth material to fit inside one or more of the slots  410 . 
       FIG. 12  illustrates a cross-sectional view of the radial implant  100 D for resurfacing the radius  1 , with the stabilizing fin  150 D implanted inside the radius  1 . 
       FIG. 13  illustrates a cross-sectional view of the carpal implant  200 A resurfacing the scaphoid  2  and lunate  3  with one or more stabilizing pins or screws  220  extending through the spacer  230 A and into the carpal bones  2  and  3 . 
       FIG. 14  illustrates the radial implant  100 B and the carpal implant  200 D combined to form a total wrist resurfacing implant. The radial stabilizing fin  150 B has one or more holes  151 B to allow bone growth and the carpal implant  200 D is secured by a carpal stabilizing fin  250 D. 
     While  FIG. 14  illustrates metal on metal articulation with the radial implant  100 B articulating with the carpal implant  200 D, it is not necessary that the implants  100 B and  200 D articulate with each other or that both be present. For example, the radial implant  100 B alone, as well as radial implants  100 A,  100 C, and  100 D, can be implanted and can articulate with the carpal bones  2  and  3 . Similarly, the carpal implant  200 D alone, as well as carpal implants  200 A- 200 C, can be implanted and can articulate with the radius  1 . Further, the static surfaces  101 A- 101 D are also radius  1  engaging surfaces and the static surfaces  201 A- 201 D are also carpal  2  and  3  engaging surfaces. 
     All components of the invention can be used with bone growth materials, replacements, or simulators, including biologic and genetic drugs, coatings, or components. 
     The articulating surfaces  102 A-D and  202 A-D can include highly polished Cobalt Chromium. In other embodiments, polymers and ceramics such as pyrolytic carbon, polycarbon, or UHMWPE can be used, or a combination thereof. 
     As will be understood by one skilled in the art, various features of each of the different radial implants  100 A- 100 D can be interchangeably used with the other implants  100 A- 100 D. For example, while only implant  100 B is illustrated as including the cutouts  151 B, one of ordinary skill in the art will appreciate that the cutouts  151 B can also be included in the stabilizing fin portion  150 A of the radial implant  100 A. Similarly, various features of each of the different carpal implants  200 A- 200 D can be interchangeably used with the other implants  200 A- 200 D. For example, while only the implant  200 C is illustrated as including the stabilizing component  203 C, one of ordinary skill in the art will appreciate that the implants  200 A,  200 B, and  200 D can also include the stabilizing component  203 C. One of ordinary skill in the art will also appreciate the advantages associated with providing each of the implants  100 A- 100 D and each of the implants  200 A- 200 D as unitary, single, one-piece, or monolithic implants. 
     A method of implanting the radial implant  100 B and the carpal implant  200 D will now be described. The description of the implantation of the radial implant  100 B and the carpal implant  200 D is for exemplary purposes only. Implantation of the other radial implants  100  is substantially similar to the implantation of radial implant  100 B and will be readily understood by one of ordinary skill in the art from the description provided herein. 
     With reference to  FIG. 10 , the wrist joint is prepared to receive one or both of the implants  100 B and  200 D using the reamer  300 , or any other suitable device for removing cartilage or tissue. If only the radial implant  100 B is being implanted, then the reamer  300  can be provided with cutting features, such as cutting teeth, on only the side of the reamer  300  facing the radius  1 . If only the carpal implant  200 D is being implanted, then the reamer  300  can be provided with cutting features on only the side of the reamer  300  facing the carpal bones  2  and  3 . The reamer  300  only clears cartilage or tissue. The reamer  300  is not used to resurface either the radius  1  or the carpal bones  2  and  3 , as was done in previous wrist joint replacements methods. The reamer  300  is inserted into the joint space  5  on the radial side of the joint, as illustrated in  FIG. 10 . 
     With reference to  FIG. 11 , if the radial implant  100 B is being implanted, then the slot  410  is formed in the radius  2  to receive the stabilizing fin  150 B to anchor the implant  100 B to the radius  2 . If the carpal implant  200 D is being implanted, then the slot  410  is formed in the scaphoid  2  to receive the stabilizing fin  250 D for anchoring the implant  200 D to the scaphoid  2 . If both the radial implant  110 B and the carpal implant  200 D are being implanted, then the slot  410  is formed in both the scaphoid  2  and the radius  1 . 
     The slot  410  can be formed using any suitable bone cutting device. For example, the slot  410  can be formed using a saw that is aligned with the radius  1  and/or the scaphoid  2  using alignment holes  420  formed in the radius  1  and/or the scaphoid  2  using a suitable bone preparation device. In contrast to prior wrist replacement procedures in which a portion of the radius  1 , scaphoid  2 , and/or lunate  3  that is proximate to the joint space  5  is reshaped or resected, surfaces of the radius  1 , the scaphoid  2 , and/or the lunate  3  facing the joint  5  are not resected or reshaped to form the slot  410 . The slot  410  simply provides a recess in the radius  1  and/or scaphoid  2  to allow the implants  100 B and  200 D to be anchored to the radius  1  and/or the scaphoid  2  respectively. The slot  410  is formed in the side of the radius  1  opposite to the ulna  4  and in the side of the scaphoid  2  opposite to the lunate  3 . 
     After the slot  410  is formed, the carpal implant  200 D and/or the radial implant  100 B are implanted. The carpal implant  200 D is implanted such that the stabilizing fin  250 D is laterally inserted into the slot  410  of the scaphoid  2  from the radial side of the wrist joint. Similarly, the radial implant  100 B is implanted such that the stabilizing fin  150 B is laterally inserted into the slot  410  of the radius  1  from the radial side of the wrist joint. The implants  200 D and  100 B can be secured in the slot  410  using any suitable device or method. For example, if the implants  200 D and  100 B include the cutouts  151 B and  251 D, the cutouts can receive bone growth or tissue growth to help anchor the implants  200 D and  100 B. Bone cement or any other suitable adhesive can also be used to anchor the implants  200 D and  100 B. 
     Implantation of the carpal implants  200 A- 200 C does not require formation of the slot  410 . For example, with reference to  FIG. 13 , the spacer  230 A of the carpal implant  200 A can be inserted within the joint space  5  with the spacer  230 A positioned between the scaphoid  2  and the lunate  3 . A suitable fastening device, such as the pin  220 , can be inserted through the spacer  230 A and into cooperation with the scaphoid  2  and/or the lunate  3  to secure the carpal implant  200 A into position. The pin  220  can be similarly used to engage the spacers  230 B and  230 C of the implants  200 B and  200 C respectively to secure the implants  200 B and  200 C into position. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.