Patient-specific Total Talus Total Ankle Arthroplasty

Abstract

The present invention provides a talus prosthesis comprising a base having a top surface and a bottom surface, and an articular component having a top surface and a bottom surface, the bottom surface of the articular component being removably coupled to the top surface of the base.

Description

[Technical field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to (i) U.S. Provisional Application No. 63 / 322,178, filed on March 21, 2022, for “Patient-Specific Total Talus for Total Ankle Arthroplasty,” and (ii) U.S. Provisional Application No. 63 / 337,556, filed on May 2, 2022, for “Artificial Implants Using Zinc Strontium Alloy for Stem Cell Stimulation,” the contents of each of which are incorporated herein by reference in their entirety. [Background technology]

[0002] Avascular necrosis (AVN) of the ankle typically occurs when a fracture damages the talus, destroying it and causing severe pain and arthritis in the ankle. Treatment of AVN can involve ankle fusion (such as tibiotalar calcaneal fusion). Recently, total talus replacement has been used to address the unique problems of AVN of the ankle. However, if a total talus replacement fails, revision surgery can bring complications for both the surgeon and the patient. Disclosed herein is a talus prosthesis that can address the complications associated with revision surgery. Summary of the Invention

[0003] The disclosure herein includes a talus prosthesis for an ankle prosthesis. The talus prosthesis described herein can address complications associated with a failed TAR, a failed total talus replacement, a failed ankle fusion, or an AVN talus.

[0004] The talus prosthesis described herein provides a modular total talus that allows a defined portion of the total talus to be disconnected from the base of the implant. In one example, the articular component can be made removable (e.g., via a Morse taper connection, as a non-limiting example), allowing the surgeon to replace only the proximal component if further articular damage occurs to the tibia. This also allows the surgeon to convert a total talus replacement to a total ankle replacement by replacing the proximal component with a new articular component that matches the mating geometry of the poly insert of the various total ankle implants. Such a modular system is particularly useful when implanting a total talus that also has fused subtalar or talonavicular joints, since these fusions do not need to be disrupted to remove the entire total talus implant. Additionally, the talus prosthesis described herein includes suture eyelets or pre-tapped holes to receive bone anchors, allowing the surgeon to reconnect the surrounding ankle ligaments to the implant. The use of such fixation methods for dermal grafts or synthetic allografts may delay or inhibit damage caused by the metallic articular components of the talus prosthesis.

[0005] Thus, in one aspect, the present disclosure provides a talus prosthesis including a base having a top surface and a bottom surface, and an articular component having a top surface and a bottom surface, the bottom surface of the articular component being removably coupled to the top surface of the base.

[0006] These and other aspects, advantages and alternatives will become apparent to those of ordinary skill in the art from a reading of the following detailed description, taken, as appropriate, with reference to the accompanying drawings. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is an exploded perspective view of an example of an artificial talus of an artificial ankle. [Diagram 2] FIG. 2 is an assembled perspective view of the example talus prosthesis of FIG. 1. [Diagram 3]FIG. 2 is an anterior-posterior view of an example of a talus prosthesis of an artificial ankle. [Figure 4] FIG. 4 is an exploded perspective view of the example talus prosthesis of FIG. 3. [Diagram 5] FIG. 4 is an assembled perspective view of the example talus prosthesis of FIG. 3. [Figure 6] FIG. 2 is a side cross-sectional view of an exemplary articular component of the talus prosthesis of FIG. 1, showing a lattice structure. [Figure 7] 1 is an example of a prosthetic talar joint component showing a shell structure with an internal honeycomb structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Total talus replacement surgery has been used to address a variety of conditions in the ankle, such as avascular necrosis (AVN) of the ankle. However, if a total talus replacement fails, revision surgery can cause complications for both the surgeon and the patient. The talus prosthesis described here can address complications associated with failed TAR, failed total talus replacement, failed ankle fusion, or AVN talus.

[0009] In particular, the talus prosthesis described herein provides a modular total talus that allows certain portions of the total talus to be disconnected from the base of the implant. In one example, the articular component can be made removable, allowing the surgeon to replace only the proximal component if further articular damage occurs to the tibia. This also allows the surgeon to convert a total talus replacement into a total ankle replacement by replacing the proximal component with a new articular component that matches the mating shape of the poly insert of various total ankle implants.

[0010] Referring to the drawings, FIGS. 1-7 show an artificial ankle talus prosthesis 100. In particular, the artificial talus prosthesis 100 shown in FIGS. 1-7 is an example of a patient-specific artificial talus prosthesis 100 defined by computed tomography (CT). The artificial talus prosthesis 100 includes a base 102 having a top surface 104 and a bottom surface 106. The artificial talus prosthesis 100 further includes an articular component 108 having a top surface 110 and a bottom surface 112. The bottom surface 112 of the articular component 108 is removably coupled to the top surface 104 of the base 102. In one example, the bottom surface 112 of the articular component 108 is removably coupled to the top surface 104 of the base 102 prior to placing the artificial talus prosthesis 100 in the patient. In another example, the bottom surface 112 of the articular component 108 is removably coupled to the top surface 104 of the base 102 in situ.

[0011] In use, the top surface 110 of the articular component 108 is positioned adjacent the patient's tibia and the bottom surface 106 of the base 102 is positioned adjacent the patient's calcaneus. The bottom surface 106 of the base 102 also articulates against the navicular bone. In one example, the bearing surfaces are constructed of ultra-high molecular weight polyethylene (UHMWPE). When removably coupled, the base 102 and articular component 108 of the talus prosthesis 100 are shaped to resemble the anatomy of the patient's talus. The modular aspect of the talus prosthesis 100 described herein allows the surgeon to replace only the proximal portion of the implant to fit the new eroded anatomy of the distal tibia or to match the mating shape of a poly insert of a total ankle replacement implant.

[0012] In one example, the base 102 is constructed from a first material and the articular component 108 is constructed from a second material that is different from the first material. In one such example, the first material is constructed from a titanium alloy and the second material is constructed from a cobalt chromium (CoCr) alloy. Other combinations of materials are possible.

[0013] In one example, the bottom surface 112 of the articular component 108 includes a protrusion 114 and the top surface 104 of the base 102 includes a recess 116 configured to receive the protrusion 114, thereby removably coupling the articular component 108 to the base 102. As an example, as shown in FIG. 1, the protrusion 114 and the recess 116 form a morse taper connection. Such a configuration allows for correction of internal and external rotation. In another example, the protrusion 114 and the recess 116 form a mechanical fastener, such as a screw. In yet another example, the bottom surface 112 of the articular component 108 includes a recess 116 and the top surface 104 of the base 102 includes a protrusion 114 configured to receive the recess 116, thereby removably coupling the articular component 108 to the base 102.

[0014] In another example, the recess 116 includes features that allow for anterior-posterior positioning of the articular component 108 relative to the base 102. In one example, the features include channels. In another example, the features consist of rails. In another example, the features include a number of evenly spaced holes. This degree of modularity allows the mechanical axis of the tibia to be aligned with the weight-bearing axis of the talus prosthesis 100. The articular component 108 is locked into a final position via fasteners, thereby locking the anterior-posterior position of the articular component 108 relative to the base 102.

[0015] As shown in FIG. 1 and FIG. 2, the articular component 108 includes a sidewall 118 disposed between the top surface 110 and the bottom surface 112. In one example, as shown in FIG. 1 and FIG. 2, the sidewall 118 includes a plurality of holes 120. In another example, the plurality of holes 120 may be disposed on other surfaces of the articular component 108. In one example, the plurality of holes 120 are configured to receive corresponding plurality of dermal or synthetic allografts. Such synthetic allografts may be composed of a silicate material, as a non-limiting example. The articular component 108 shown in FIG. 1 and FIG. 2 may be configured to contact the ankle joint, the talonavicular joint, and the subtalar joint. Each of these joints includes a plurality of holes 120 for receiving skin or synthetic allografts, which may improve the articular joint and even allow for reduced pressure. Such skin or synthetic allografts may be used to secure sutures or to place suture anchors to hold the allograft in place.

[0016] In conventional total talus implants, the articular component 108 of the talus prosthesis 100 directly interfaces with the cartilage surfaces of the calcaneus, navicular, and tibia, potentially causing damage to the surrounding cartilage. Providing an allograft fixation method can delay or inhibit damage caused by metal articular components. In particular, the allograft can act as a buffer between the articular component 108 of the talus prosthesis 100 and the cartilage of the distal tibia, calcaneus, and / or navicular, prolonging the life of the talus prosthesis 100 and increasing the time between revision surgeries. Additionally, the multiple holes 120 shown in FIGS. 1 and 2 and described above also allow for replacement of the allograft in the event of minimal damage to the articular component of the distal tibia, further prolonging the need to replace the entire talus implant or convert the patient to a total ankle replacement.

[0017] In one example, the articular component 108 and / or base 102 may include suture eyelets and / or drilled and tapped holes 122 configured to receive bone anchors for lateral ankle or deltoid instability. Such suture eyelets and / or drilled and tapped holes allow the surgeon to reconnect the surrounding ankle ligaments to the talus prosthesis 100 during surgery. The advantage of providing tapped holes 122 for receiving bone anchors allows knotless anchoring techniques to be utilized in surgery. The location of the suture eyelets or tapped holes 122 for anchors may be determined during preoperative planning after a computed tomography (CT) scan.

[0018] In one example, the base 102 includes one or more holes designed to allow for subtalar fixation, ankle fixation, TTC fixation, and / or talonavicular fixation. These holes may be located above the neck of the base 102 or below the neck of the base 102 to allow for screws to be targeted from the patient's calcaneus. In one example, a targeting guide that goes around the ankle joint may be required. The base 102 of the talus prosthesis 100 may include a mechanism for mechanically attaching such a targeting guide. In the case of a TTC fusion, the base 102 may include a hole to allow for insertion of a TTC nail through the subtalar joint into the intramedullary canal of the patient's tibia.

[0019] Most modern joint replacement devices that articulate with bearing surfaces are manufactured from cobalt chrome (CoCr) alloys, ceramic alloys, zirconium oxide, and titanium alloys coated with nitrides to improve wear resistance. However, because cobalt chrome (CoCr) and the aforementioned materials are dense materials, the increased weight can increase wear against the less dense bone in which the implant is placed. To minimize such wear and reduce the weight of the implant while still maintaining the desirable properties of cobalt chrome (CoCr), a weight reduction mechanism is desirable. In one example, as shown in FIG. 6, at least a portion of the interior of the talus prosthesis 100 is hollow. In one example, the interior of the talus prosthesis 100 includes a lattice structure 124. Although only the articular component 108 with the lattice structure 124 is shown in FIG. 6, the base 102 can also include a similar lattice structure 124. In one example, the entire interior of the base 102 and / or the entire interior of the articular component 108 is comprised of the lattice structure 124. In another example, the interior of the base 102 and / or the interior of the articular component 108 includes alternating solid and lattice structure layers. The solid and lattice layers may be manufactured from the same material (such as CoCr) or a variation of mixed material layers. This same material may also comprise the shell of the base 102 and / or the shell of the articular component 108. The lattice structure 124 located in the hollow interior of the talus prosthesis 100, which adds strength to the implant, may be either a uniform beam design or a mathematically driven gyroid shape.

[0020] As shown in Fig. 7, in one example, at least a portion of the interior of the talus prosthesis 100 is hollow. In one such example, the interior of the talus prosthesis 100 includes a honeycomb structure 126. Although Fig. 7 only shows the articular component 108 with the honeycomb structure 126, the base 102 may also include a similar honeycomb structure 126. The honeycomb structure 126 may provide additional strength to the talus prosthesis 100 while reducing weight. Additionally, the honeycomb structure 126 may provide an additional structure for positioning the lattice structure 124.

[0021] As further shown in FIGS. 6 and 7 and described above, the articular component 108 includes a protrusion 114 and the top surface 104 of the base 102 includes a recess 116 configured to receive the protrusion 114, thereby removably coupling the articular component 108 to the base 102. In one example, the protrusion 114 comprises a single protrusion, as shown in FIG. 6. In another example, the protrusion 114 comprises a pair of protrusions, as shown in FIG. 7. In one example, the interior of the protrusion 114 is solid. In another example, the interior of the protrusion 114 is hollow and includes a lattice structure similar to the lattice structure 124 of the body of the talus prosthesis 100 described above. In one example, the protrusion 114 is at an angle between 0 degrees and 90 degrees relative to the bottom surface 112 of the articular component 108. In another example, the protrusion 114 is perpendicular to the bottom surface 112 of the articular component 108.

[0022] In addition to the advantages discussed above, the talus prosthesis 100 described above in connection with FIGS. 1-7 provides advantages in the surgical approach. Conventional total talus can be very large, and in some cases the surgeon must break the fibula to gain access and then reattach the fibula after installation of the total talus. The talus prosthesis 100 described above includes a bottom surface 112 of the articular component 108 that is removably coupled to a top surface 104 of the base 102, allowing the surgeon to assemble the talus prosthesis 100 in two pieces. This allows the surgeon to perform surgery in an anterior approach, which is the standard approach for performing total ankle replacement surgery. Additionally, separating the talus prosthesis 100 into two components allows the talus prosthesis 100 to be more securely fixed with bone screws, facilitating fixation of the talus prosthesis 100 to the calcaneus.

[0023] In one example, one or more components of the artificial talus 100 described above in connection with Figures 1-7 are configured to be placed in contact with a patient's bone, and at least a portion of the outer surface of the artificial talus 100 includes a zinc strontium (Zn-Sr) alloy. In such an example, the Zn-Sr alloy is selected from the group consisting of Zn-Sr, Zn-0.8Sr, Zn-0.6Sr, Zn-0.5Sr, Zn-0.4Sr, Zn-0.2Sr, and Zn-0.1Sr. When the artificial talus 100 contacts the patient's bone, the Zn-Sr alloy stimulates bone formation in mesenchymal stem cells at the implant site. In one example, the Zn-Sr alloy stimulates mesenchymal stem cells selected from the group consisting of CD45-, CD45-CD146+, CD45-CD271+, CD31-44+45-73+90+105+, and CD45-CD34+. Additionally, the Zn-Sr alloy increases intracellular PI3K / Akt, MAPK / Erk, and / or Wnt / β-catenin pathway signaling, thereby promoting anabolic and anticatabolic effects on bone remodeling. In one example, the Zn-Sr alloy further comprises a material selected from the group consisting of tricalcium phosphate (TCP), hydroxyapatite (HA), and silicon. In another example, the Zn-Sr alloy contains no more than trace amounts of magnesium.

[0024] The addition of Sr-Zn based metals to one or more components of the artificial talus 100 helps promote and / or stimulate new bone formation while inhibiting bone resorption during the healing process, thereby reducing potential failure modes associated with implant loosening and subsidence.

[0025] In one example, the Zn-Sr alloy comprises a three-dimensional structure that extends away from the outer surface of the talus prosthesis 100. In one such example, the three-dimensional structure comprises a scaffold.

[0026] As shown in any one of FIGS. 1-7, in some examples, one or more components of the artificial talus 100 are manufactured by an additive manufacturing process using additive manufacturing machines such as stereolithography, multi-jet modeling, inkjet printing, selective laser sintering / melting (or DMLS, EBM), and fused filament manufacturing. Additive manufacturing can create one or more components of the artificial talus 100 and other physical objects as interconnected single-piece structures using a layer-by-layer production process. Additive manufacturing involves placing a physical object in one or more selected materials based on a design of the object. For example, additive manufacturing can generate one or more components of the artificial talus 100 using a computer-aided design (CAD) of the artificial talus 100 as instructions. As a result, design changes to the artificial talus 100 can be implemented immediately during the subsequent physical creation of the artificial talus 100. This allows the components of the artificial talus 100 to be easily tailored or scaled for different types of applications (e.g., for use in different types and sizes of artificial ankles).

[0027] The layered processes utilized in additive manufacturing can deposit one or more components of the talus prosthesis 100 in complex designs that may not be possible with devices assembled using subtractive manufacturing. Alternatively, the design of the talus prosthesis 100 may include aspects aimed at improving overall operation. For example, the design may incorporate physical elements that help redirect stresses in a desired manner that may not be reproducible in a conventionally manufactured device.

[0028] Additive manufacturing also allows one or more components of the talus prosthesis 100 to be deposited with different materials using a multi-material additive manufacturing process. In such an example, the base 102 may be made from a first material and the articular component 108 may be made from a second material that is different from the first material, as described above. In another example, the entire talus prosthesis 100 is made from the same material. Other combinations of materials are also possible. Furthermore, one or more components of the talus prosthesis 100 may have some layers made using a first type of material and other layers made using a second type of material.

[0029] In one example, the interior of one or more components of the talus prosthesis 100 is hollow. In one such example, the interior of the base 102 and / or the articular component 108 includes a lattice structure. In one example, the entire interior of the base 102 and / or the articular component 108 includes a lattice structure. In another example, the base 102 and / or the interior of the base 102 and / or the articular component 108 includes alternating solid layers and lattice structure layers. The solid layers and lattice structure layers may be manufactured from the same material (such as CoCr) or a variation of mixed material layers. This same material may also comprise the shell of the base 102 and / or the articular component 108. The lattice structure disposed in the hollow interior of the base 102 and / or the articular component 108 that adds strength to the implant may be either a uniform beam design or a formula driven gyroid shape.

[0030] As used herein, "coupled" means directly and indirectly associated. For example, member A may be directly associated with member B, and indirectly associated with another member C. It will be understood that not all relationships between the various disclosed elements have necessarily been depicted.

[0031] Unless otherwise indicated, terms such as "first," "second," and the like are used herein merely as labels, and are not intended to impose any order, position, or hierarchy requirements on the items to which they refer. Further, reference to, for example, a "second" item does not require or preclude the presence of, for example, a "first" or lower-numbered item, and / or a "third" or higher-numbered item.

[0032] A reference herein to "one embodiment" or "one example" or "example" means that one or more features, structures, or characteristics described in connection with that example are included in at least one embodiment. Usage of the phrase "one embodiment" or "one example" or "example" in various places in this specification may or may not refer to the same example.

[0033] As used herein, a system, device, structure, article, element, component, or hardware that is "configured" to perform a particular function has the ability to perform the particular function without actual modification, rather than merely having the potential to perform the particular function after further modification. In other words, a system, device, structure, article, element, component, or hardware that is "configured" to perform a particular function is specifically selected, created, implemented, utilized, programmed, and / or designed for the purpose of performing the particular function. As used herein, "configured" refers to the existing characteristics of a system, device, structure, article, element, component, or hardware that enable the system, device, structure, article, element, component, or hardware to perform a specified function without further modification. For purposes of this disclosure, a system, device, structure, article, element, component, or hardware that is described as "configured" to perform a particular function may additionally or alternatively be described as "adapted" to perform that function and / or "operable to perform that function."

[0034] Exemplary methods and systems are described herein. It should be understood that the words "example," "exemplary," and "illustrative" as used herein mean "serving as an example, instance, or illustration." Any example or feature described herein as "example," "exemplary," or "illustrative" is not necessarily to be construed as preferred or advantageous over other examples or features. The examples described herein are not intended to be limiting. It will be readily understood that the aspects of the disclosure, as generally described and illustrated in the Figures herein, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are expressly contemplated herein.

[0035] The terms "about," "approximately," or "substantially" with respect to a quantity or measurement described herein mean that the stated characteristic, parameter, or value need not be achieved exactly, but deviations or variations including, for example, tolerances, measurement errors, limitations in measurement accuracy, and other factors known to those of skill in the art may occur to an extent that does not interfere with the characteristic's intended effect. For example, in one embodiment, the term "about" may refer to ±5% of a given value.

[0036] Moreover, it should be understood that the particular configurations shown should not be considered limiting, and that in other examples, more or less of each element may be shown in a particular figure. Further, some of the elements shown may be combined or omitted. Furthermore, examples may include elements that are not shown.

[0037] In the following description, numerous specific details are set forth to provide a thorough understanding of the disclosed concepts, although the inventive concepts may be practiced without some or all of these details. In other instances, details of well-known devices and / or processes are omitted so as to avoid unnecessarily obscuring the disclosure. While some concepts will be described in conjunction with specific examples, it will be understood that these examples are not intended to be limiting.

[0038] The following claim limitations are not written in means-plus-function form and are not intended to be construed under 35 U.S.C. § 112(f) unless such claim limitations expressly use the word "means" followed by a description of the function without further structure. [Explanation of symbols]

[0039] 100 Artificial talus 102 Base 104, 110 Top surface 106, 112 Bottom 108 Joint Components 114 Protrusion 116 Recess 118 Side wall 120 holes 124 Lattice structure 126 Honeycomb Structure

Claims

1. A talus prosthesis comprising a base having a top surface and a bottom surface, and a joint component having a top surface and a bottom surface, a bottom surface of the joint component is removably coupled to the top surface of the base, the bottom surface of the joint component being provided with a protrusion; a top surface of the base includes a recess configured to receive the protrusion such that the joint component is removably coupled to the base; The articular component includes a side wall disposed between the top surface and the bottom surface, the side wall including a plurality of holes.

2. A talus prosthesis comprising a base having a top surface and a bottom surface, and a joint component having a top surface and a bottom surface, The bottom surface of the articular component is removably coupled to the top surface of the base.

3. 3. The method of claim 2, wherein the base comprises a first material and the joint component comprises a second material different from the first material. The artificial talus described above.

4. The talus prosthesis of claim 3 , wherein the first material comprises a titanium alloy and the second material comprises a cobalt chromium (CoCr) alloy.

5. The artificial talus according to any one of claims 2 to 4, wherein a bottom surface of the joint component includes a protrusion and a top surface of the base includes a recess configured to receive the protrusion, thereby removably connecting the joint component to the base.

6. The artificial talus according to claim 5 , wherein the projection and the recess form a Morse taper connection.

7. The artificial talus according to claim 5 , wherein the recess has a function that enables the joint component to be positioned in the anterior-posterior direction relative to the base.

8. The talus prosthesis of claim 7 , further comprising a fastener configured to fix an anterior-posterior position of the joint component relative to the base.

9. The artificial talus according to any one of claims 2 to 8, wherein the joint component includes a side wall disposed between the top surface and the bottom surface, the side wall including a plurality of holes.

10. The talus prosthesis of claim 9 , wherein the plurality of holes are configured to receive a corresponding plurality of dermal grafts or synthetic allografts.

11. 11. The talus prosthesis of any one of claims 2 to 10, wherein the articular component and / or the base includes suture eyelets and / or drilled and tapped holes configured to receive bone anchors for lateral ankle or deltoid instability.

12. A talus prosthesis according to any one of claims 2 to 11, wherein the base comprises one or more holes designed to allow subtalar / ankle fixation or talonavicular fixation.

13. The talus prosthesis of claim 12 , wherein the one or more holes are disposed in the neck of the base to allow for targeting of the screws through the patient's calcaneus.

14. An artificial talus according to any one of claims 2 to 13, wherein at least a portion of the outer surface of the bottom surface of the base comprises a zinc-strontium (Zn-Sr) alloy, and / or at least a portion of the outer surface of the top surface of the joint component comprises a Zn-Sr alloy.

15. The artificial talus according to claim 14, wherein the zinc strontium (Zn-Sr) alloy is selected from the group consisting of Zn-Sr, Zn-0.8Sr, Zn-0.6Sr, Zn-0.5Sr, Zn-0.4Sr, Zn-0.2Sr, and Zn-0.1Sr.

16. The artificial talus according to claim 14 or 15, wherein the zinc-strontium (Zn-Sr) alloy stimulates osteogenesis of mesenchymal stem cells selected from the group consisting of CD45-, CD45-CD146+, CD45-CD271+, CD31-44+45-73+90+105+, and CD45-CD34+.

17. The artificial talus according to any one of claims 14 to 16, wherein the zinc-strontium (Zn-Sr) alloy further contains a material selected from the group consisting of tricalcium phosphate (TCP), hydroxyapatite (HA), and silicon.

18. The artificial talus according to any one of claims 14 to 17, wherein the zinc-strontium (Zn-Sr) alloy contains only trace amounts of magnesium or less.

19. The talus prosthesis according to any one of claims 14 to 18, wherein the zinc strontium (Zn-Sr) alloy has a three-dimensional structure extending away from the outer surface of the bottom surface of the base and / or the zinc strontium (Zn-Sr) alloy has a three-dimensional structure extending away from the outer surface of the top surface of the joint component.

20. The talus prosthesis of claim 19 , wherein the three-dimensional structure comprises a scaffold.

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