Patent Publication Number: US-2022218491-A1

Title: Modular talar fixation method and system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/410,387, filed May 13, 2019, which is a continuation of U.S. patent application Ser. No. 15/848,934, filed Dec. 20, 2017 (U.S. Pat. No. 10,327,906), which is a continuation of U.S. patent application Ser. No. 14/835,208, filed Aug. 25, 2015 (U.S. Pat. No. 9,877,839), the entireties of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     An ankle joint may become severely damaged and painful due to arthritis, prior ankle surgery, bone fracture, osteoarthritis, and/or one or more additional conditions. Options for treating the injured ankle have included anti-inflammatory and pain medications, braces, physical therapy, joint arthrodesis, and total ankle replacement. 
     Total ankle replacement generally comprises two components—tibial implant and a talar implant. The implants comprise articulation surfaces sized and configured to mimic the range of motion of the ankle joint. For example, the talar implant may comprise an implant sized and configured to mimic the talar dome and the tibial implant may comprise an articulation surface sized and configured to mimic articulation of the tibia. An articulating component may be located between the talar implant and the tibial implant. 
     Installation of a total ankle replacement can include forming one or more holes or cuts in a bone. For example, a hole may be drilled through the talus and into the tibia to create a channel for inserting a tibial stem. In some installations, additional bone is removed from the talus to make space for a talar stem extending from the talar portion. 
     SUMMARY 
     In various embodiments, a talar implant system is disclosed. The talar implant system includes an implant having a body including a bone contact surface and an articulation surface located opposite the bone contact surface. The body defines at least one fastener hole extending therethrough from the articulation surface to the bone contact surface along a longitudinal axis. A fastener is sized and configured to be partially received within a distal end of the at least one fastener hole at a first angle with respect to the longitudinal axis of the fastener hole. A fastener cap is sized and configured to be received within a proximal end of the at least one fastener hole, wherein the fastener cap couples the body to the fastener. 
     In various embodiments, a total joint replacement system is disclosed. The total joint replacement system includes a tibial implant sized and configured to couple to a resected tibia and a talar implant sized and configured to couple to a resected talus. The talar implant includes a body having a bone contact surface and an articulation surface located opposite the bone contact surface. The body defines at least one fastener hole extending therethrough from the articulation surface to the bone contact surface along a longitudinal axis. The at least one fastener hole is sized and configured to receive a fastener therein at a first angle with respect to the longitudinal axis of the fastener hole. A fastener cap is sized and configured to be received within a proximal end of the at least one fastener hole. The fastener cap couples the body to the fastener. 
     In various embodiments, a talar implant is disclosed. The talar implant comprises a body including a bone contact surface and an articulation surface located opposite the bone contact surface. The body defines at least one angled fastener hole extending therethrough from the articulation surface to the bone contact surface along a longitudinal axis. The at least one angled fastener hole is sized and configured to receive a fastener therein at a first angle with respect to the longitudinal axis of the fastener hole. A fastener cap is sized and configured to be received within a proximal end of the at least one fastener hole to couple the body to the fastener. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The features and advantages of the present invention will be more fully disclosed in, or rendered obvious by the following detailed description of the preferred embodiments, which are to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein: 
         FIG. 1  illustrates an anatomic view of an ankle joint. 
         FIG. 2  illustrates one embodiment of an ankle joint having a total ankle replacement system therein. 
         FIG. 3  illustrates one embodiment of an implant having one or more angled fastener holes formed through an articulation surface. 
         FIG. 4  illustrates a bottom-view of the implant of  FIG. 3 . 
         FIG. 5  illustrates a cross-sectional view of the implant of  FIG. 3  taken along line  5 - 5  in  FIG. 4 . 
         FIG. 6  illustrates a cross-sectional view of a fastener cap having an internally threaded cavity, in accordance with some embodiments. 
         FIG. 7  illustrates a fastener having a threaded head, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “proximal,” “distal,” “above,” “below,” “up,” “down,” “top” and “bottom,” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. 
     In various embodiments, the present disclosure generally provides an implant for use with a total ankle replacement system. The implant includes one or more variable angle screw holes extending through the articulation surface of the implant at an angle with respect to a bone contact surface. A cap and/or retainer can be installed over the screws to couple the screws to the implant. 
       FIG. 1  illustrates an anatomic view of an ankle joint  2 . The ankle joint  2  comprises a talus  4  in contact with a tibia  6  and a fibula  8 . A calcaneus  10  is located adjacent to the talus  4 . In total ankle replacements, the talus  4  and the tibia  6  may be resected, or cut, to allow insertion of a talar implant and a tibial implant.  FIG. 2  illustrates the ankle joint  2  of  FIG. 1  having a total ankle replacement system  12  inserted therein. 
     The total ankle replacement system  12  comprises a talar implant  14  and a tibial implant  18 . The talar implant  14  comprises a body defining a talar articulation surface  16  (or talar dome). The talar implant  14  may be anchored to the talus by one or more screws (not shown). The tibial implant  18  is sized and configured for installation into the tibia  6 . The tibial implant  18  comprises a body having an articulation surface  20  and, in some embodiments, a tibial stem  24  extending into the tibia  6  to anchor the tibial implant  18 . The talar joint surface  16  and the tibial joint surface  20  are mutually sized and configured to articulate. The joint surfaces  16 ,  20  replace the natural ankle joint surfaces, which are removed, to restore a range of motion that mimics the natural joint. One or more holes may be formed in the tibia and/or the talus prior to and during insertion of the tibial implant  18  or the talar implant  12 . For example, in some embodiments, a hole is drilled starting in the bottom of the talus, extending through the talus and into the tibia. The hole may comprise, for example, a 6 mm hole configured to receive the stem  24  of the tibial implant  18 . 
     The joint surfaces  16 ,  20  may be made of various materials, such as, for example, polyethylene, high molecular weight polyethylene (HMWPE), rubber, titanium, titanium alloys, chrome cobalt, surgical steel, and/or any other suitable metal, ceramic, sintered glass, artificial bone, and/or any combination thereof. The joint surfaces  16 ,  20  may comprise different materials. For example, the tibial joint surface  20  may comprise a plastic or other non-metallic material and the talar joint surface  16  may comprise a metal surface. Those skilled in the art will recognize that any suitable combination of materials may be used. 
       FIG. 3  illustrates one embodiment of an implant  102  having one or more fastener holes  110   a ,  110   b  formed through an articulation surface  106 . The implant  102  comprises a body  104  having an articulation surface  106  and an opposed bone contact surface  108 . The body  104  has a predetermined thickness between the articulation surface  106  and the bone contact surface  108 . The predetermined thickness can be constant and/or variable. The articulation surface  106  is sized and configured to interface with an opposing joint surface of an opposing implant. For example, in one embodiment, the articulation surface  106  is sized and configured to interface with a joint surface of a tibial implant, such as, for example, the tibial implant  18  shown in  FIG. 2 . In another example, the articulation surface  106  is sized and configured to interface with an articulation body located between a tibial implant  18  and the talar dome  106 . The bone contact surface  108  comprises a surface configured to contact a resected bone section. For example, in some embodiments, the bone contact surface  108  is configured to rest on and couple to a resected talus. In other embodiments, the bone contact surface  108  is configured to couple to a plate anchored to the bone. The bone contact surface  108  may comprise a planar surface, a concave surface, and/or any desirably shaped surface. For example, in the illustrated embodiment, the bone contact surface  108  comprises a concave surface. 
     In various embodiments, the implant  102  comprises one or more fastener holes  110   a ,  110   b  extending through the body  104 . The fastener holes  110   a ,  110   b  extend from the articulation surface  106  through the body  104  to the bone contact surface  108 . The fastener holes  110   a ,  110   b  are sized and configured to receive a fastener  114  therein. In some embodiments, the fastener  114  comprises a head  118  and a threaded section  120 . The threaded section  120  is configured to couple to a bone, such as, for example, a talus and/or a plate. Although a single thread is illustrated, it will be appreciated that the fastener  114  may include any number of threads on the threaded section  120  and/or on the head  118 . In various embodiments, the fastener  114  may comprise a screw (such as a bone screw, a slotted screw, and/or any other suitable screw), a peg (such as a coated and/or an uncoated peg) and/or any other suitable fastener. The fastener holes  110   a ,  110   b  may define one or more internal thread patterns  112 . 
     The fastener holes  110   a ,  110   b  can be formed through the body  104  at any suitable angle. For example, in the illustrated embodiment, the fastener holes  110   a ,  110   b  are formed through the articulation surface  106  at an angle of about 0°, e.g., the fastener holes  110   a ,  110   b  have a longitudinal axis substantially perpendicular with a tangent line of the curve of the articulation surface  106  at a center of the fastener hole  110   a ,  110   b . In other embodiments, the fastener holes  110   a ,  110   b  may be formed at any angle with respect to the articulation surface. For example, in various embodiments, the fastener holes  110   a ,  110   b  can include longitudinal axes positioned at any angle with respect to a tangent line of the curve of the articulation surface  106 , such as, for example, an angle between 0 and 30 degrees, 0 and 45 degrees, 0 and 60 degrees, or 0 and 90 degrees. Although specific angles are given herein as examples, it will be appreciated by those skilled in the art that the fastener holes  110   a ,  110   b  may be formed in the body  104  at any angle with respect to the articulation surface  106  and/or the bone contact surface  108 . 
     In some embodiments, the fastener  114  is sized and configured to be inserted into the fastener holes  110   a ,  110   b  at an angle with respect to a longitudinal axis of the fastener holes  110   a ,  110   b . For example, in some embodiments, the fastener  114  may be inserted at an angle of between 0 and 90 degrees, such as, for example, 30 degrees, 45 degrees, or 60 degrees. In some embodiments, the angle between the fastener  114  and the longitudinal axis of the fastener hole  110   a ,  110   b  is predetermined. In other embodiments, the angle between the fastener  114  and the longitudinal axis of the holes  110   a ,  110   b  is variable and/or selectable within a predetermined range. A clinician may select an angle for the fastener during installation of the implant  102 . Although specific angles are given herein as examples, it will be appreciated by those skilled in the art that the fasteners  114  may be inserted into the fastener holes  110   a ,  110   b  at any suitable angle with respect to the longitudinal axis of the fastener holes  110   a ,  110   b . In some embodiments, the angles of the fasteners  114  in each of the fastener holes  110   a ,  110   b  are the same. In other embodiments, the angles of fasteners  114  in each of the angled fastener holes  110   a ,  110   b  are different. 
     In some embodiments, the fastener holes  110   a ,  110   b  comprise a diameter larger than the diameter of a head  118  of the fastener  114 . The fasteners  114  can freely slide through the angled fastener holes  110   a ,  110   b  and do not interface with internal threads  112  of the holes  110   a ,  110   b . The fasteners  114  can be inserted into a specific position in a bone prior to installation of the implant  102 . After the fasteners  114  are positioned, the implant  102  is placed on the bone such that the fasteners  114  are located within the fastener holes  110   a ,  110   b . In other embodiments, the fasteners  114  may be installed through the fastener holes  110   a ,  110   b  after the implant  102  is positioned on a bone. After positioning the fasteners  114  within the fastener holes  110   a ,  110   b , a fastener cap  116  can be inserted into a proximal end of each of the fastener holes  110   a ,  110   b  to secure the body  104  to the fasteners  114 . 
     In some embodiments, the fastener cap  116  includes external threads configured to mate with the internal threads  112  of the fastener holes  110   a ,  110   b . The fastener cap  116  includes a cavity  122  at a distal end configured to interface with a head  118  of the fastener  114 . For example, in some embodiments, the fastener cap  116  acts as a set screw that maintains the implant  102  and the fastener  114  in a locked relationship. In some embodiments, as shown in  FIGS. 6-7 , the cavity  122  of the fastener cap  116   a  includes internal threads  130  sized and configured to couple to threads  132  formed on the head  118   a  of a fastener. 
     In some embodiments, the fastener cap  116  is sized and configured to be flush with the articulation surface  106  when in a locked position, e.g., fully inserted into the fastener hole  110   a ,  110   b . In some embodiments, the fastener cap  116  is sized and configured to sit below the articulation surface  106  when in a locked position. An additional articulation cap (not shown) may be inserted over the fastener cap  116  to fill the fastener hole  110   a ,  110   b  and provide a solid, smooth articulation surface  106 . In some embodiments, the fastener cap  116  extends beyond the articulation surface  106  when in a locked position. The fastener cap  116  may operate as a rotational stop for an implant placed in an articulating arrangement with the articulation surface  106 . For example, in some embodiments, the fastener cap  116  may operate as a rotational stop for a tibial implant in an articulating relationship with the implant  102 . 
       FIG. 5  illustrates the a cross-sectional view of the implant  102  taken along line  5 - 5  of  FIG. 4 . As shown in  FIG. 5 , the fastener  114  has a diameter less than the internal diameter of the holes  110   a ,  110   b  such that the fastener  114  fits within the holes  110   a ,  110   b  at a variable angle without interfacing with and/or contacting the internal threads  112  of the hole  110   a ,  110   b . A fastener cap  116  can be inserted into a proximal end of the hole  110   a ,  110   b . The fastener cap  116  includes a distal cavity  122  sized and configured to receive a fastener head  118  therein. The fastener cap  116  locks the implant  102  to the fastener  114  such that the fastener  114  and the fastener cap  116  maintain the implant  102  in a fixed position with respect to a bone. In some embodiments, the fastener hole  110   a ,  110   b  comprises a lip  124  formed at a distal end to prevent the fastener cap  116  from being inserted beyond a predetermined depth. The distal lip  124  may correspond to a fully locked position of the fastener cap  116   
     In some embodiments the fastener  114  can be positioned at a predetermined angle with respect to the bone contact surface  108  of the talar dome  102 . For example, in some embodiments, the fastener  114  is inserted into the bone at an angle with respect to a longitudinal axis of the fastener hole  110   a ,  110   b . The fastener  114  may be inserted at any suitable angle with respect to the longitudinal axis of the hole  110   a ,  110   b , such as, for example, any angle between 0 and 90 degrees, 0 and 60 degrees, 0 and 45 degrees, 0 and 30 degrees, and/or any other suitable angle. In some embodiments, the head  118  of the fastener  114  and/or the cavity  122  of the fastener cap  116  are sized and configured to allow the fastener cap  116  and the fastener  114  to interface at a variety of angles. For example, in some embodiments, the head  118  of the fastener  114  includes a rounded, or ball-type, head. The cavity  122  is a socket-type cavity configured to interface with the head  118  of the fastener  114 . The ball-and-socket coupling allows the fastener  114  to be placed at a variety of angles with respect to the talar dome  102  and coupled to the talar dome  102  by the fastener cap  116 . The fastener  114  may comprise any suitable fixation device, such as, for example, a screw, a peg, a coated peg, a slotted screw, a push-fit fastener, and/or any other suitable fastener. 
     Although the implant  102  is shown having two angled fastener holes  110   a ,  110   b  located on a first side of the articulation surface  106 , it will be appreciated that the implant  102  may comprise any suitable number of fastener holes  110   a ,  110   b  such as, for example, one, two, or four fastener holes  110   a ,  110   b . In addition, the fastener holes  110   a ,  110   b  may be located in any suitable position on the articulation surface  106 , such as, for example, on the same side (as shown in  FIG. 1 ), on opposite sides, and/or on multiple sides of the articulation surface. 
     In various embodiments, an implant system is disclosed. The implant system includes an implant having a body including a bone contact surface and an articulation surface located opposite the bone contact surface. The body defines at least one fastener hole extending from the articulation surface to the bone contact surface along a longitudinal axis. A fastener is sized and configured to be partially received within a distal end of the at least one fastener hole at a first angle with respect to the longitudinal axis of the fastener hole. A fastener cap is sized and configured to be received within a proximal end of the at least one fastener hole, wherein the fastener cap couples the body to the fastener. 
     In some embodiments, the at least one fastener hole comprises a plurality of internal threads. The fastener can have a first diameter less than a diameter of the internal threads of the fastener hole. 
     In some embodiments, the fastener cap includes a plurality of external threads sized and configured to couple to the internal threads of the at least one fastener hole. The fastener cap can include a distal cavity sized and configured to receive a head of the fastener therein. In some embodiments, the distal cavity comprises a socket and the head of the fastener comprises a ball. In some embodiments, the distal cavity defines a plurality of internal threads and the head of the fastener defines a plurality of external threads sized and configured to interface with the plurality of internal threads of the distal cavity. The fastener can comprise a bone screw. 
     In various embodiments, a total joint replacement system is disclosed. The total joint replacement system includes a tibial implant sized and configured to couple to a resected tibia and a talar implant sized and configured to couple to a resected talus. The talar implant includes a body having a bone contact surface and an articulation surface located opposite the bone contact surface. The body defines at least one fastener hole extending therethrough from the articulation surface to the bone contact surface along a longitudinal axis. The at least one fastener hole is sized and configured to receive a fastener therein at a first angle with respect to the longitudinal axis of the fastener hole. A fastener cap is sized and configured to be received within a proximal end of the at least one fastener hole. The fastener cap couples the body to the fastener. 
     In some embodiments, the at least one fastener hole comprises a plurality of internal threads. The fastener can have a first diameter less than a diameter of the internal threads of the fastener hole. In some embodiments, the fastener cap includes a plurality of external threads sized and configured to couple to the internal threads of the at least one fastener hole. The fastener cap can include a distal cavity sized and can be configured to receive a head of the fastener therein. In some embodiments, the distal cavity comprises a socket and the head of the fastener comprises a ball. In some embodiments, the distal cavity defines a plurality of internal threads and the head of the fastener defines a plurality of external threads sized and configured to interface with the plurality of internal threads of the distal cavity. The fastener can comprise a bone screw. 
     In various embodiments, a talar implant is disclosed. The talar implant comprises a body including a bone contact surface and an articulation surface located opposite the bone contact surface. The body defines at least one angled fastener hole extending therethrough from the articulation surface to the bone contact surface along a longitudinal axis. The at least one angled fastener hole is sized and configured to receive a fastener therein at a first angle with respect to the longitudinal axis of the fastener hole. A fastener cap is sized and configured to be received within a proximal end of the at least one fastener hole to couple the body to the fastener. 
     In some embodiments, the at least one fastener hole comprises a plurality of internal threads. The fastener can have a first diameter less than a diameter of the internal threads of the fastener hole. The fastener cap can comprise a plurality of external threads sized and configured to couple to the internal threads of the at least one fastener hole. 
     Although the subject matter has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments, which may be made by those skilled in the art.