Abstract:
Total ankle arthroplasty with a tibial plate, a talar plate and a middle or core component. The ankle arthroplasty may allow for varus or valgus accommodation through the use of a core component with various medial and lateral heights in varus and valgus orientations. In addition the resurfacing of the talus is accomplished with a talar plate with a curved orientation that is congruent to one surface of the core component to allow for appropriate ankle manipulation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the following which is incorporated herein by reference: 
         [0002]    U.S. Provisional Patent Application No. 61/478,254, filed Apr. 22, 2011, entitled TOTAL ANKLE ARTHROPLASTY WITH VARUS-VALGUS ACCOMMODATION, Attorney&#39;s docket no. DUG-11 PROV, which is pending. 
     
    
     BACKGROUND 
       [0003]    The ankle, or talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus bone in the foot. This joint plays an integral role in balance, muscle stabilization, load bearing and motion, and is responsible for the upwards and downwards movement of the foot. Total ankle replacement is often necessary for patients with arthritis or other degenerative or traumatic conditions. Often when choosing a total ankle replacement system, a varus-valgus design is desirable to accommodate different patient deformities. 
         [0004]    The present disclosure relates to systems, apparatus, method and kit for total joint replacement. Specifically, this disclosure relates to a total ankle replacement apparatus, system, kit and methods suitable to accommodate or correct various patient deformities. The disclosed ankle replacement may resist off center loads by restricting some of the degrees of freedom of rotation. This resistance may result from an alignment system in which a component contains a slot in which a rib of an endplate slides. The ability to resist off center loads may allow the disclosed ankle replacement to accommodate issues such as various patient deformities and different surgical placement procedures. By adjusting the varus-valgus orientation of a core piece of the ankle replacement system, the disclosed system may provide stability to the weight bearing ankle joint in patients with various deformities. 
         [0005]    While the examples in the present disclosure relate to the ankle joint, the systems and methods are applicable to other synovial joints in the body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Various examples of the present technology will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only typical examples of the technology and are therefore not to be considered limiting of its scope. 
           [0007]      FIG. 1  is a perspective assembly view of an ankle replacement system; 
           [0008]      FIG. 2A  is a top perspective view of a tibial endplate of the system of  FIG. 1 ; 
           [0009]      FIG. 2B  is a bottom perspective view of the tibial endplate of  FIG. 2A ; 
           [0010]      FIG. 3A  is a perspective top view of a core of the system of  FIG. 1 ; 
           [0011]      FIG. 3B  is a bottom perspective view of the core of  FIG. 3A ; 
           [0012]      FIG. 4A  is an anterior view of the core of  FIG. 3A ; 
           [0013]      FIG. 4B  is a cross sectional lateral view of the core of  FIG. 3A ; 
           [0014]      FIG. 4C  is a lateral side view of the core of  FIG. 3A ; 
           [0015]      FIG. 4D  is a cross sectional anterior view of the core of  FIG. 3A ; 
           [0016]      FIG. 5A  is a top perspective view of a talar endplate of the system of  FIG. 1 ; 
           [0017]      FIG. 5B  is a bottom perspective view of the talar endplate of  FIG. 5A ; 
           [0018]      FIG. 6A  is an anterior view of the talar endplate of  FIG. 5A ; 
           [0019]      FIG. 6B  is a cross sectional lateral view of the talar endplate of  FIG. 5A ; 
           [0020]      FIG. 6C  is a lateral side view of the talar endplate of  FIG. 5A ; 
           [0021]      FIG. 6D  is a cross sectional anterior view of the talar endplate; 
           [0022]      FIG. 7  is an exploded view of the total ankle replacement system of  FIG. 1 ; 
           [0023]      FIG. 8A  is an anterior view of the total ankle replacement system of  FIG. 1  operatively assembled; 
           [0024]      FIG. 8B  is a cross sectional lateral view of the ankle replacement system of  FIG. 1  operatively assembled; 
           [0025]      FIG. 8C  is a lateral view of the ankle replacement system of  FIG. 1  operatively assembled; 
           [0026]      FIG. 8D  is a cross sectional anterior view of the ankle replacement system of  FIG. 1  operatively assembled; 
           [0027]      FIG. 9  is a front view of a set of cores; 
           [0028]      FIG. 10  is a perspective view of the total ankle assembly of  FIG. 1  with a neutral core implanted between a tibia and a talar bone; 
           [0029]      FIG. 11A  is a front view of the total ankle assembly of  FIG. 1  with a 10 degree varus core implanted between a tibia and a talar bone; 
           [0030]      FIG. 11B  is a front view of the total ankle assembly of  FIG. 10  with a neutral or 0 degree core implanted between a tibia and a talar bone; and 
           [0031]      FIG. 11C  is a front view of the total ankle assembly of  FIG. 1  with a 10 degree valgus core implanted between a tibia and a talar bone. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    In this specification, standard medical directional terms are employed with their ordinary and customary meanings. Superior means toward the head. Inferior means away from the head. Anterior means toward the front. Posterior means toward the back. Medial means toward the midline, or plane of bilateral symmetry, of the body. Lateral means away from the midline of the body. Proximal means toward the trunk of the body. Distal means away from the trunk. 
         [0033]    The present disclosure relates to systems, methods and kits for ankle anthroplasty, or in other words for replacing damaged and injured ankle joints with an artificial joint prosthesis. Those of skill in the art will recognize that the following description is merely illustrative of the principles of the technology, which may be applied in various ways to provide many different alternative embodiments. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts in the appended claims. 
         [0034]    In order to accommodate various patient deformities, it may be advantageous to have variation in the angle of articulation between the proximal end of the talus and the distal end of the tibia. 
         [0035]    In one embodiment, an artificial ankle joint comprises a core, which may also be referred to as an articular insert or nucleus, beset on either side by endplates that may interact with the bones. Referring to  FIGS. 1-3 , an ankle replacement system is illustrated. System  90  may include a proximal bone-interfacing endplate  100 , which may also be referred to as a tibial endplate, a core  200 , or core component, and a distal bone-interfacing endplate  300 , or talar plate, which may also be referred to as a talar endplate. 
         [0036]    Referring to  FIG. 1 , a perspective view of an operatively assembled ankle replacement system is shown. Fins  102  are shown to protrude proximally from the tibial endplate  100 , or tibial plate, to facilitate engagement with the bone, and may be coated in a bone growth enhancing material. It can also be seen in  FIG. 1  that the core portion contains a slot  202 , which will be shown to be congruent with a rib structure on the talar endplate. 
         [0037]    Referring to  FIGS. 2A and 2B , a top perspective view and a bottom perspective view of the tibial endplate  100  is illustrated. The tibial endplate  100  may include a first bone-facing side  104 , a second core-facing side  110  and an edge surface  112  extending between the two sides. The proximal, bone-facing side  104  of the tibial endplate may have a smooth surface, or may otherwise include surface roughening features, and may be provided with a bone growth enhancing media. 
         [0038]    In  FIG. 2A , at least one fin  102  is illustrated protruding from the proximal side  104  of the endplate  100 , which fin may serve to facilitate interaction with the bone. The fin  102  may also be referred to as a keel, tooth, ridge or blade. In the example shown in  FIG. 2A , two fins  102  are illustrated extending from a first end portion  103  to a second end portion  105  of the tibial endplate  100 . In other examples, the fin or fins  102  may extend only partially between the first end  103  and the second end  105  of the endplate  100 . The fins  102  are shown to be parallel to one another across the length of the tibial endplate  100 , however, the fins  102  may have alternative orientations with respect to one another. 
         [0039]    The fins  102  may include a sharpened edge  107  that is shaped to engage with a bone surface. The fins  102  may also have alternative surface geometries, such as rounded or otherwise contoured surfaces. 
         [0040]    In  FIG. 2A , the fins  102  may extend proximally perpendicularly to the first bone-facing surface  104 . Additionally, in this example the fins  102  are shown to be integral with the bone-facing surface  104 , however, the fins  102  may also be detachable from the tibial endplate  100 . 
         [0041]      FIG. 2B  depicts the distal, core-facing side  110  of the endplate  100 , which may be opposite to the first bone-facing surface  104  and may include a recessed surface  106  that is shaped to engage with a complementary feature on the core  200 . The recessed surface may be at least partially encircled by a perimeter wall  108 , or perimeter rim. The perimeter  108  of the recessed surface  106  may be of various sizes and shapes. The perimeter  108  may intersect the edge surface  112  of the tibial endplate  100 . The endplate  100  may also contain a locking mechanism to secure the tibial endplate to the core. 
         [0042]    Referring to  FIGS. 3A and 3B , different perspective views of the core  200  are illustrated. The core  200  may also be referred to as the articular insert or nucleus. The core may include a first endplate-facing surface  208 , or tibial plate facing surface, a second endplate-facing surface  210 , or talar plate facing surface, and an edge surface  212  that extends between the two endplate-facing surfaces. The edge surface  212  may be perpendicular to the first end plate-facing surface  208 . 
         [0043]      FIG. 3A  shows that the first, or proximall or superior side of the core  200 ? contains a protruded surface  204 , or protrusion, which is congruent with and complementary to the recessed area  106  of the tibial endplate  100 . The protrusion may be at least partially encircled by a recessed perimeter surface  214 . The core  200  may include a locking mechanism to secure the connection between the endplate and core section. For example, the core  200  may rigidly lock to the endplate  100  by an interference lock, Morse taper, or press fit. 
         [0044]      FIG. 3B  depicts the second, or distal, endplate-facing surface  210  of the core  200 . The distal endplate-facing surface  210  may include a curved articular surface  206  and a slot  202 . The slot  202  may also be referred to as a groove, cleft or a channel. The curved articular surface  206  may be smooth, and may be contoured to match a complementary contoured surface of the talar endplate  300 . The edge surface  212  may include a first, or medial, wall  216  and a second, or lateral, wall  218  opposite the first wall. Wherein each wall  216 ,  218  may extend from the end plate-facing surface  208  to the curved articular surface  206 . 
         [0045]    The slot  202  may be rounded, as seen in  FIG. 3B , or may have various other shapes and dimensions, such as chamfered or square edges. Here it is shown that the slot  202  extends entirely between a first end  203  and a second end  205  of the core  200 . Alternatively, the slot may extend only a partial distance between the first end  203  and the second end  205 . 
         [0046]    It will be appreciated that the features of the recess  106  of the tibial plate  100  and the protrusion  204  of the core component  200  may be switched and have the same rigid locking. That is to say that a recess may be on the core component  200  and a protrusion on the tibial plate  100 . 
         [0047]    Referring to  FIGS. 4A-4D , different views of the core  200  are illustrated.  FIG. 4A  is an anterior view of the core  200 . The protruded surface  204  on the proximal endplate-facing side  208  can be seen extending from the recessed perimeter surface  214 . On the distal endplate-facing side of the core  210 , the slot  202  is illustrated as being substantially centrally located on the core  200 , and having a symmetric cross section. The slot  202  may otherwise be located away from the center of the core  200 , and the distal face  210  of the core may include more than one slot  202 . 
         [0048]      FIG. 4B  provides a cross section of the core  200  of  FIG. 4A  from a lateral view through cross section line  4 B- 4 B. The concave curvature of the distal side  210  of core  200  can be seen in  FIG. 4B .  FIG. 4C  is a lateral view of the core  200 , again showing the concave curvature of the distal endplate-facing side  210  of the core  200 .  FIG. 4D  provides a cross section of the core  200  of  FIG. 4C  from an anterior view through cross section line  4 D- 4 D. The slot  202  can be clearly seen in  FIG. 4D . 
         [0049]      FIGS. 5A and 5B  provide different perspective views of the talar endplate  300 , which is located distal to the core  200  when the total ankle assembly is operatively arranged as illustrated in  FIG. 1 . The talar endplate comprises a proximal core-facing surface  310 , a distal bone-facing side  304  and an edge surface  312  connecting the proximal and distal surfaces. The bone-facing surface  304  may also be provided with a biocompatible bone growth enhancing media. 
         [0050]      FIG. 5A  provides a top perspective view of the talar endplate  300 . The proximal surface  310  may be an articulated, contoured surface that is congruent with the curvature of the distal articulating surface  206  of the core  200 . The proximal surface  310  may be smooth, or may contain a variety of surface-roughening features. 
         [0051]    A rib  302  is depicted protruding proximally from the proximal surface  308 , which may be congruent with the slot  202  on the distal endplate-facing side of the core  200 . The rib  302 , which may also be referred to as a rail, may extend at least partially between a first end portion  303  and a second end portion  305  of talar endplate  300 . The talar endplate  300  may also include more than one rib  302  to engage the core  200 . An equal number of ribs and slots may be provided on complementary talar endplates and cores. 
         [0052]    The rib  302  may be shaped such that it can slide within the slot  202 , providing for limited joint articulation and limited degrees of freedom when the ankle system  90  is assembled. In one example, the rib and slot may be closely fitted so that articulation is limited to a direction established by the rib and slot. In another example, the slot may be wider than the rib so that articulation may include rotation about the long axis of the tibia or in varus/valgus directions. 
         [0053]      FIG. 5B  provides a bottom perspective view of talar endplate  300 .  FIG. 5B  illustrates the presence of endplate teeth, also referred to as keels,  306 ,  307 , on the distal bone-facing side  304  of the talar plate  300 . These teeth may have a thin, sharpened edge  307  to facilitate interaction of the ankle replacement system  90  with the proximal section of the talar bone. The teeth may also be of various other shapes and dimensions. 
         [0054]    As shown in  FIG. 5B , distal bone-facing surface  304  may include a resurfacing talar surface  313 .  FIG. 5B  depicts the resurfacing talar surface  313  as a concave curved surface, however, it may also be flat or convexly shaped, depending on the nature of the surgical procedure and on the patient anatomy. 
         [0055]      FIGS. 6A-6D  provide additional views and cross-sections of the talar endplate  300 .  FIG. 6A  provides a front view of the talar endplate  300  and depicts the convex curvature on the proximal core-facing side  310  of the talar endplate  300 , which is congruent with the concave curvature of the distal endplate-facing side  210  of the core  200 . Also shown in  FIG. 6A  is the rib  302  that protrudes from the articular surface  308  of the talar endplate.  FIG. 6B  provides a cross-section of the talar plate  300  of  FIG. 6A  through section line  6 B- 6 B and shows one of the endplate teeth  306  that protrude from the resurfacing surface  313 .  FIG. 6C  is a lateral view of the talar endplate  300 .  FIG. 6D  provides a cross section of the talar endplate of  8 C through section line  6 D- 6 D and gives another view of the top surface  308  of the talar endplate and protruded rib  302  section, as well as the two teeth extensions  306  from the distal bone-facing side  304  of the talar endplate  300 . 
         [0056]    Referring to  FIG. 7 , an exploded perspective view of the three primary components of system  90  is illustrated. When system  90  is operatively assembled, the tibial endplate  100  is located proximal to the core  200 . The recessed surface  106  on the distal surface  110  of the tibial endplate  100  receives the protruded surface  204  of the core  200  and rigidly locks the core  200  to the endplate  100 . The talar endplate  300  sits distal to the core  200 . The rib structure  302  is received by the slot feature  202  located on the distal side  210  of the core  200 . The curvature of the proximal surface  308  is congruent with the distal side  210  of the core  200 . The talar endplate  300  articulates congruently with the core  200 , at least by sliding along a direction established by the rib  302  and the slot  202 . The first end portions  103 ,  203 ,  303  of the tibial endplate  100 , the core  200 , and the talar endplate  300 , respectively, all face the same way. 
         [0057]      FIGS. 8A-8D  provide several views and cross sections of the assembled ankle replacement.  FIG. 8A  provides a front view of the assembled ankle replacement. The core piece  200  is operatively assembled with a tibial endplate  100  and a talar endplate  300 .  FIG. 8B  provides a cross section of the ankle assembly of  FIG. 8A  through section line  8 B- 8 B. The orientation of the three components is shown as assembled.  FIG. 8C  provides a lateral view of the assembled ankle replacement system.  FIG. 8D  provides a cross section of the ankle replacement system through section line  8 D- 8 D. 
         [0058]      FIG. 9  provides a front view of a set of cores with different varus and valgus orientations. Shown at the top of  FIG. 9 , core  250  is angled in a valgus orientation at angle  252  relative to the horizontal line  220 . The core  250  in a valgus orientation includes a first, or medial,  216  wall height that is shorter than a second, or lateral, wall  218  height. Core  260  is also angled in a valgus orientation at angle  262  relative to the horizontal line  220 , wherein angle  262  is less than  252 . Similar to core  250 , the core  260  in a valgus orientation includes a first wall, or medial wall,  216  height that is shorter than a second wall, or lateral wall,  218  height; however the difference is less between the first wall  216  height to the second wall  218  height in core  260  than in core  250 . In each of the cores  250 ,  260  a plane of the tibial plate facing surface forms an acute angle relative to a horizontal line. Core  200  is oriented as previously described in a neutral position, with the elevated top portion flush with the horizontal line  220 . Core  270  is angled in a varus orientation, at angle  272  relative to the horizontal line  220 . The core  270  in a varus orientation includes a first wall, or medial wall,  216  height that is longer than a second wall, or lateral wall,  218  height. Core  280  is angled in a varus orientation at angle  282 , wherein angle  282  is greater than  272  relative to the horizontal line  220 . Similar to core  270 , the core  280  in a varus orientation includes a first wall  216  height that is longer than a second wall  218  height; however the difference is more between the second wall  218  height to the first wall  216  height in core  280  than in core  270 . In each of the cores  270 ,  280  a plane of the tibial plate facing surface forms an acute angle relative to a horizontal line. These are some examples of a comprehensive set or kit of cores which may be interchangeably used in the disclosed total ankle replacement. 
         [0059]    In the present system, a varus or valgus deformity of an ankle joint may be corrected by selecting and inserting a core which compensates for, or neutralizes, the deformity. The bone resections on the tibia may be made with reference to the tibia alone, and the cuts may be aligned so that a minimal amount of bone is resected. In one example, the tibial resections may be made with reference to the distal tibial articular surface, regardless of the orientation of the distal tibial articular surface. In a similar manner, the bone resections on the proximal talus may be made with reference to the talus alone. In one example, the talar resections may be made with reference to the proximal talar articular surface, regardless of its orientation. In this arrangement, a suitable core may be interposed between the endplates to compensate for deformity and restore a neutral orientation between the tibia and talus. 
         [0060]      FIG. 10  provides a perspective view of the disclosed ankle replacement system  90  with a neutral core implanted between the tibia and talar bones. 
         [0061]      FIGS. 11A-11C  shows the disclosed total ankle replacement as it would appear relative to the tibia and talar bones in different varus-valgus formations.  FIG. 11A  shows the disclosed ankle replacement in a 10 degree varus formation,  FIG. 11B  shows the disclosed ankle replacement in a neutral formation and  FIG. 11C  shows the disclosed ankle replacement in a 10 degree valgus formation.