Abstract:
A prosthesis suited for orthopedic implantation comprising a modular intramedullary rod that provides intramedullary guidance and that supports an artificial joint surface that can articulate with another artificial joint surface in various ways. Intramedullary guidance systems and methods introduce some and/or all surgical tools and ankle prostheses components through the tibia, using minimal invasive exposure. The systems and methods align the talus and tibia for the installation of one or more ankle prostheses components, and also maintain that alignment during the installation using intramedullary guidance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/783,915, filed Mar. 14, 2013, the entirety of which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]    The invention relates to ankle replacement prostheses and systems, as well as associated surgical instruments and procedures. 
       BACKGROUND OF THE INVENTION 
       [0003]    Until the early to mid-1970&#39;s, patients with injured or diseased ankle joints commonly resulting from rheumatism, or degenerative or traumatic arthritis, had few options when their ankle joints failed. The most common procedure to help these patients regain some use of their ankle was obliteration of the joint by fusion, a procedure that is still commonly used today. Fusion, however, renders the ankle stiff and generally immobile relative to the lower leg, resulting in limited use and additional stresses on the knee and hip joints. 
         [0004]    Total ankle prosthesis have been used since at least as early as 1969. The medical community recognized that such ankle replacement led to largely increased use of the ankle joint because the replacement permitted ankle ranges of motion which generally attempted to mimic the natural human joint. Since that time, ankle replacement prostheses have become increasingly common in use and improved in design. However, less invasive surgical methods with improved healing and decreased failure rates are desirable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  illustrates one example of a curved reamer reaming an intramedullary cavity in a tibia in accordance with some embodiments. 
           [0006]      FIG. 2  is a plan view of one example of a broach in accordance with some embodiments. 
           [0007]      FIG. 3  is a cross-sectional view of one example of different modular broach components in accordance with some embodiments. 
           [0008]      FIG. 4  illustrates a pair of angled broach components coupled together via a hinge in accordance with some embodiments. 
           [0009]      FIG. 5  illustrates a plurality of broach components hinged together in accordance with some embodiments. 
           [0010]      FIG. 6  provides various view of broach segments in accordance with some embodiments. 
           [0011]      FIG. 7  illustrates a handle in accordance with some embodiments. 
           [0012]      FIG. 8  is a cross-sectional view of one example of a self-advancing reamer in accordance with some embodiments. 
           [0013]      FIG. 9  illustrates various views of examples of angled reamers in accordance with some embodiments. 
           [0014]      FIG. 10  illustrates a plurality of intramedullary rod components disposed within an intramedullary canal and coupled to a varus/valgus and plantar/dorsi flexion alignment guide in accordance with some embodiments. 
           [0015]      FIG. 11  illustrates a plurality of intramedullary rod components disposed within an intramedullary canal and coupled to a tibial cut guide in accordance with some embodiments. 
           [0016]      FIG. 12  illustrates one example of a tibia and talar cut guide in accordance with some embodiments. 
           [0017]      FIG. 13  illustrates one example of tibia and talar cuts having been made in accordance with some embodiments. 
       
    
    
     SUMMARY OF THE INVENTION 
       [0018]    In one embodiment, an intramedullary rod is provided that includes a plurality of modular components sized and configured to be disposed in an intramedullary canal. The modular components are configured to be interconnected with one another in situ, with the distal-most modular component is a base component configured to engage an alignment guide. 
         [0019]    A system is provided for intramedullary guidance to implant an ankle prosthesis that includes a first tool sized and configured to form a passage between a tibia and a talus and a second tool sized and configured to create an intramedullary canal in a distal end of the tibia. A plurality of modular tibial rod components are provided, sized, and configured to be disposed in the intramedullary canal and connected to each other in situ to form a single tibial rod component. A base modular component located on a distal end of a tibial rod component is configured to engage an alignment guide. The alignment guide is configured to translate coronal, transverse, and sagittal adjustments from the alignment guide to a cutting guide. 
         [0020]    In one method according to the invention, a plurality of modular components are inserted into an intramedullary canal, and connected in situ to form a single intramedullary rod component, with the distal end of the intramedullary rod component being connected to an alignment guide. 
         [0021]    In a further method of implanting an ankle prosthesis system a passage is formed between a tibia and a talus so as to define an intramedullary canal in a distal end of a tibial shaft with a flexible reaming tool. A plurality of modular rod components are introduced inferiorly through the intramedullary canal into the tibial shaft so as to interconnect the modular rod components to form a single tibial rod component thereby allowing a modular tibial base component to be coupled to a distal-most end of the tibial rod component. An alignment guide is coupled to the tibial base component using the alignment guide to translate adjustments to a cutting guide. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “horizontal,” “vertical,” “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 figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. 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. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. 
         [0023]    This description is divided into logical sections for ease of disclosure. Section I provides structural descriptions of representative embodiments of a modular intramedullary rod component of a total ankle replacement system and exemplary devices that have the desired form, fit, and function. Section II provides descriptions of representative embodiments of systems, methods, and techniques useful for the implantation of total ankle replacement systems using intramedullary guidance and devices to achieve the desired form, fit, and function. 
         [0024]    Although the disclosure hereof is detailed and exact to enable those of ordinary skill in the art to practice the invention, the physical embodiments herein disclosed are merely examples. While the preferred embodiments have been described, the details may be changed without departing from the spirit and scope of the present invention, which is defined by the claims. 
       I. Modular Intramedullary Rod Component 
       [0025]    Two or more modular components may form an intramedullary rod component suitable for use in any surgical procedure in which a rod is used for intramedullary guidance of surgical tools or fixation of an implant, whether it is a total joint implant, fusion (arthrodesis) implant, osteotomy fixation implant, or fracture fixation implant. As illustrated in  FIG. 10 , for example, a rod component  100  includes a top (i.e., superior) modular component  102 , one or more optional mid-modular components  104 , and a base (i.e., inferior) modular component  106 . Top component  102  is preferably convex or domed to facilitate advancement of rod  100  in the direction of top component  102  within an intramedullary canal  12  within tibia  10 . The modular component configuration is ideally suited for securing prosthetic components together in a minimally invasive procedure. This configuration is also ideally suited for minimally invasive surgeries in which a small surgical opening is used to install relatively larger prosthetic components. 
         [0026]    Two or more of modular components  102 ,  104 ,  106  may be sequentially connected to one another, in situ, to form a single intramedullary rod assembly  100 . For example, top modular component  102  may be joined with a base modular component  106 . Alternatively, one or more mid-modular components  104  may be placed between top  102  and base  106  modular components to form an intramedullary rod  100  of a desired length. Modular components  102 ,  104 ,  106  may be attached to one another by a variety of fixation structure, e.g., morse tapers, complementary threaded structures, or bayonet mounts of the type known in the art. 
         [0027]    Thus, a plurality of modular components  102 ,  104 ,  106  may be assembled so as to form a single intramedullary rod component  100 . Intramedullary rod component  100  may be positioned and fixed within a tibia  10  with bone cement, hydroxyapatite, a ground bone composition, screws, or a combination thereof, or any other fixation materials suitable for prosthetic surgery. For example, a modular intramedullary rod  100  placed in a tibial intramedullary canal may be fixed to the tibia with screws. If screws are used, they may extend anteriorly, posteriorly, medially, laterally and/or at oblique angles, or any combination thereof. 
         [0028]    One or more of modular components  102 ,  104 ,  106  may include a configuration for engagement with a driver or other tool to facilitate advancement of the component within bone and/or to torque one component into an adjacent component. Similarly, one or more of modular components  102 ,  104 ,  106  may include a second configuration for engagement with a wrench or other tool to grasp or otherwise secure the component during installation. 
         [0029]    Each modular component  102 ,  104 ,  106  is desirably sized and configured to be individually installed through a small incision, e.g., a small anterior opening in the ankle, and through a passage between a tibia and a talus (which has been formed in advance). In this way, individual modular components  102 ,  104 ,  106  may be sequentially joined together, in situ, e.g., within a reamed intramedullary canal  12  within tibia  10  and progressively advanced up the intramedullary canal  12 , top modular component  102  first. 
         [0030]    The last or base component  106  is sized and configured to attach to an alignment guide  200 . Alignment guide  200  is configured to make coronal, transverse, or sagittal adjustments and, to aid in preparing a joint to receive an ankle replacement prosthesis. Alignment guide  200  may comprise one or more pins, such as Steinmann pins, to translate the coronal, transverse, and/or sagittal adjustments to a cutting guide  300 ,  400  ( FIGS. 11 and 12 ). Also, a cutting guide  300  may be configured to aid in making a cut in tibia  10  in order to prepare it for receiving a tibial component of an ankle replacement prosthesis in accordance with embodiments of the invention. Cutting guide  400  may be configured to aid in cutting tibia  10  and/or talus  20  to prepare the bones to receive a total ankle prosthesis. Once the cuts have been made to the appropriate portions of tibia  10  or talus  20 , and using intramedullary rod component  100  to provide guidance of the tibial and/or talar cuts that are to be made ( FIG. 13 ), modular rod component  100  may be disengaged from alignment guide  300 ,  400 . Base component  106  is configured to then attach to a tibial component of an ankle prosthesis that would comprise the upper half of an ankle prosthesis. 
         [0031]    Modular components  102 ,  104 ,  106  may be made of any material suitable for forming a total joint or materials suitable for use in the prosthetic arts including, but not limited to, metals, ceramics, titanium, titanium-alloys, tantalum, chrome cobalt, surgical steel, polyethylene, absorbable polymer, or any other total joint replacement metal and/or ceramic, bony in-growth surface, sintered glass, artificial bone, any uncemented metal or ceramic surface, or a combination thereof. Modular components  102 ,  104 ,  106  may further be covered with one or more coatings such as antimicrobial, antithrombotic, and osteoinductive agents, or a combination thereof. These agents may further be carried in a biodegradable carrier material with which the pores of tibial rod component may be impregnated. 
         [0032]    Modular intramedullary rod  100  configuration not only permits installation using minimally-invasive surgical procedures, but provides a means to install long fixation members or rods that might not be achievable if they were constructed of a single piece. While the long or extended length of the modular intramedullary rod is particularly well-suited for use in the tibia, the modular rod could be used in other long bones or, in the talus as well. 
       II. Intramedullary Guidance System and Technique 
       [0033]    Proper overall alignment of the total ankle prosthesis and improved long term results are achieved with embodiments of the present invention. Desirably, the ankle replacement prosthesis is installed using minimally invasive intramedullary guidance. Intramedullary guidance is established with respect to the major axis of the tibia by minimally invasive access through a passage formed between tibia  10  and talus  20 , via an incision in the anterior portion of the ankle, and through the tibial shaft. Intramedullary guidance along the axis of the tibia makes it possible to make properly oriented bone cuts of the talus and tibia through an anterior access incision to the ankle joint. Using installation tools, systems, and techniques that incorporate intramedullary guidance, the total ankle system prosthesis can be installed in desired alignment and orientation with all the natural axes of the native ankle joint it replaces. These natural axes include the anterior to posterior axis (Y-horizontal axis) of rotation of the ankle joint, the natural medial-to-lateral axis (X-horizontal axis) of rotation of the ankle joint, and the natural superior-to-inferior axis (Z-vertical axis) of alignment of the ankle joint with the major axis of the tibia. 
         [0034]    Among the benefits achieved by the invention is establishing and maintaining proper alignment of the anterior to posterior axis (Y-horizontal axis) of rotation, so that the ankle replacement prosthesis establishes and maintains the desired degree of plantar-dorsi (“up and down”) flexion of the foot. Further, by establishing and maintaining proper alignment of the natural medial-to-lateral axis (X-horizontal axis) of rotation, the prosthesis establishes and maintains the desired degree of inversion/eversion (“in and out”) rotation of the foot. In addition, by establishing and maintaining proper alignment of the natural superior-to-inferior axis (Z-vertical axis) of alignment of the ankle joint with the long axis of the tibia, the prosthesis is accurately oriented with respect to the central tibial axis of the leg, so that intramedullary support can be achieved by inferior drilling of the tibia using fluoroscopic guidance. 
       A. Boring the Tibia for the Modular Intramedullary Rod Component 
       [0035]    A physician makes an incision on an anterior portion of an ankle joint. A first tool, e.g. a guide pin, may be used to establish or to create a passage between the tibia and the talus bones. The passage provides anterior access to a distal end of the tibial shaft so that an intramedullary canal may be formed. A second tool is provided, such as a flexible intramedullary reamer  500  ( FIG. 1 ) for the purpose of establishing an intramedullary canal  12  within the tibia  10 . Canal  12  is configured to receive modular tibial rod components  102 ,  104 ,  106 , making use of the anterior access through the cleared passage between tibia  10  and talus  20 . Reamer  500  advantageously includes a bullet-shaped, i.e., parabolic or rounded conical, nose  502  having cutting flutes  503  on an outer surface, and that fits within the previously formed passage between the tibia and the talus. Entering the passage, reamer  500  forms an intramedullary tibial canal  12 . A depth mark can be noted on the reamer so that the tibia is reamed to a predetermined depth as deemed appropriate by the physician. The physician may retract reamer  500  through the anterior passage previously formed between tibia  10  and talus  20 , via intramedullary canal  12 , for installation of the modular intramedullary rod  100 . 
         [0036]    In some embodiments, one or more broaches  600  may be arranged and used to create intramedullary canal  12 . For example,  FIGS. 2-6  illustrate examples of modular broach components  650  that may be coupled together and thereafter forced into the intramedullary canal  12  of a tibia  10  so as to selectively enlarge the diameter of the canal.  FIG. 2  illustrates a dove-tail  602  configured to allow the alignment of the modular broach components. As illustrated in  FIG. 3 , broach components  650 ,  660  include a groove at one end that is sized and configured to be coupled to a handle or to engage a complementary structure of another broach component so as to couple the two broach components together. The exterior surface of broach components  650 ,  660  respectively define circumferential groove  652  suitable for being engaged by a holding tool. Broach component  650  tapers at a first end  656  and includes cutting flutes  503  that are suitable for cutting bone. An opening  654  is defined at the opposite end of broaching component  650  and configured to engage a coupling structure  666 , e.g., a “T-shaped post, extending from an end of broach component  660 . Broach component  660  also defines an opening configured to engage an engagement structure  666  of another broach component  660 . 
         [0037]    Referring to  FIGS. 4 ,  5 , and  6 , broach components  700 ,  702  may be hingedly coupled to one another by a plurality of hinges  704 . In some embodiments and as best seen in  FIG. 5 , a spring-loaded dowel pin  706  (i.e., a dowel pin  706  biased by a spring  708  or other biasing member) is configured to align two broach components/segments  700 ,  702 . When dowel pin  706  is retracted by, e.g., inserting a wedged tip into an extractor hole, adjacent segments  700 ,  702  that are coupled together are able to be bent or pivot relative to one another. When dowel pin  706  is engaged, broach components  700 ,  702  are locked relative to one another. Also, an impactor tip  800  is configured to be connected to a broach  700 ,  702 . As best seen in  FIG. 6 , broaches  700 ,  702  may define a groove  710  sized and configured to receive a rail of a tibial stem guide therein. 
         [0038]      FIGS. 8 and 9  illustrate examples of self-advancing reamers  900 . In  FIG. 8 , reamer  900  includes a threaded tip  902  that pulls or otherwise advances reamer  900  into bone. Reamer  900  also includes flutes  904  configured to pull the reamer through the bone as reamer  900  cuts the bone. In some embodiments, a retrieval wire  906  is coupled to reamer body  908  and is configured to be pulled by a surgeon or other medical professional to retrieve the reamer from an intramedullary channel. As shown in  FIG. 9 , a self-advancing reamer  900  may include a beveled gear assembly  910  that is slidably coupled to reamer body  908  such that reamer body  908  can be advanced into an intramedullary canal with the reamer gearing remaining in position (although allowed to rotate). In some embodiments, a circumferential groove  912  is provided that is sized and configured to be coupled to other guide structures, which allows beveled gear assembly  910  to rotate while being held in a fixed position as reamer body  908  advances axially within the bone. In some embodiments, the reamer is driven by a gear chain disposed within reamer body  908  that is configured to interface with an alignment guide for holding the reamer step perpendicular to the resection. 
         [0039]      FIG. 7  illustrates one example of handle  150  configured to allow slap-hammer  800  to assist with the extraction of broach segments and can also be used for revision implant extraction. In some embodiments, the external broach handle  150  includes a modular tip configured to be coupled to modular or hinged broaches and prosthesis components (e.g., stem and/or trays) for impacting the prosthesis within an intramedullary cavity. 
       B. Installing the Intramedullary Rod Component 
       [0040]    Once intramedullary canal  12  has been formed within the distal tibia, it is ready to receive the multi-component, modular intramedullary rod  102 ,  104 ,  106  as illustrated in  FIGS. 10 and 11 . In this installation sequence, as in previously described sequences of the installation, installation of the modular intramedullary rod  102 ,  104 ,  106  takes advantage of the anterior access incision provided in the cleared joint passage between the tibia and talus. The physician inserts the top tibial modular component  102  into the joint space through the previously formed anterior passage. The assembly tool engages top modular component  102 , by gripping the top modular component. Top modular component  102  is advanced partially up into the preformed tibial canal. 
         [0041]    A mid-modular component  104  is inserted through the same anterior incision. A driver is configured to engage mid-modular component  104 , with a tool engaging top modular component  102  to keep it from rotating, the physician twists the driver to torque the threaded male end of mid-modular component  104  into the threaded female end of top modular component  102 . This joins the top and mid modular components  102 , 104 . Once tightened, the wrench is switched from top modular component  102  to mid-modular component  104 . The physician axially advances the driver to push top modular component  102  beyond the confines of the cleared joint space and up into the tibial canal. 
       C. Making Bony Cuts in the Talus and Tibia 
       [0042]    In the representative embodiments, base modular component  106  of the intramedullary rod is sized and configured to engage alignment guide  200  ( FIG. 10 ) which allows for coronal, transverse, and sagittal adjustments. Additionally, alignment guide  200  may comprise one or more pin holes  209  configured for receiving Steinmann pins that may be used to translate the coronal, transverse and/or sagittal adjustments from alignment guide  200  to cutting guide  300 . Cutting guide fixtures  300 ,  400  ( FIGS. 11 and 12 ) may be configured to aid in making a bony cut in the tibia. Alternatively, cutting guide  300  may be configured to aid in making bony cuts in both the tibia and the talus. Cutting guide fixtures  300 ,  400  may be installed and stabilized over the ankle joint in an anterior, posterior, or lateral position relative to the ankle joint. Cutting guide fixtures  300 ,  400  may be secured either directly to intramedullary rod  100  or to underlying frame  200  to which the alignment guide is also attached ( FIGS. 11 and 12 ). Cutting guide fixtures  300 ,  400  may include a superior bone cutting blade guide and an inferior bone cutting blade guide. The cutting guide fixture also includes apertures  215  for receiving fixation pins adjacent the superior and inferior blade guides  222 . In a representative embodiment, the pins can comprise Steinmann pins. A pair of the pins are positioned in tibia  10 , adjacent to a superior blade guide and another pair of pins are positioned in passageways  223  located in talus  20 , adjacent an inferior blade guide so as to resect those portions of the distal tibia and proximal talus as schematically illustrated in  FIG. 13 . Modular intramedullary rod  100  component helps to ensure that the joint components maintain the correct alignment relative to one another so that the resulting cuts are more accurately positioned. Fluoroscopy may be used to aid in making the bony cuts. 
       D. System and Technique for Installing a Total Ankle Prosthesis 
       [0043]    After the bony cuts have been made, the fixture and pins may be disengaged from the base modular component. Loose bone pieces are removed and the cleared joint space irrigated. The cleared joint space and the anterior passage provide for the insertion of other installation tools and the components of a total ankle replacement prosthesis. For example, an artificial tibial joint surface may be coupled to the distal end of modular intramedullary rod component  106 . Further, an artificial talar joint surface may be fixed to the talus for articulation with the artificial tibial joint surface. 
         [0044]    Other embodiments and uses of the apparatuses, systems, and methods described herein will be apparent to those of ordinary skilled in the art from consideration of the specification and practice of the disclosed methods. The specification should be considered exemplary only with the true scope and spirit of the apparatuses, systems, and methods indicated by the following claims. As will be easily understood by those of ordinary skill in the art, variations and modifications of each of the disclosed embodiments can be easily made within the scope of the disclosed apparatuses, systems, and methods as defined by the following claims.