Compliant mechanisms for orthopedic joint replacements and implanted prostheses

Abstract

The disclosed invention relates to an orthopedic device having a first articulation member having an inner surface and an outer surface, a second articulation member having an inner surface and an outer surface, and at least one bending element having first and second ends, the first end coupled to the inner surface of the first articulation member and the second end coupled to the inner surface of the second articulation member, wherein the first and second articulation members are configured to move relative to one another within a first degree of freedom.

Description

[Background technology]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 287,375, filed December 8, 2021, which is incorporated by reference in its entirety.

[0002] Conventional orthopedic joint replacements constitute replacement of the articular surfaces of damaged joints. Conventional implants are composed of distinct artificial joint surfaces that articulate across one another as the joint moves, so joint stability depends on the bone structure and natural ligaments surrounding the reconstruction, limiting the amount of deformation that can be corrected. The articulating surfaces also generate synthetic particulates that cause osteolytic-type responses and aseptic loosening, which is the primary failure mode for all joint replacements. Rotating hinge prostheses also generate particulates due to their dependency on the articulating load surfaces, and are therefore also subject to eventual failure via aseptic loosening. Furthermore, rotating hinge prostheses are overconstrained, meaning that they exhibit excessive stiffness in all directions except a single rotational DOF. Conventional joint replacements also depend on robust integration with the surrounding natural bone, which is often compromised as a result of underlying disease, resulting in subsidence and implant failure.

[0003] The compliance of biological tissues plays an essential role in regulating human movement. Mechanical compliance determines the body's response to external disturbances, allowing it to accommodate imperfections, attenuate shocks, and store and return mechanical energy. This compliance is particularly important in joints, which govern how bones move in relation to one another. Disruption of natural joint compliance dramatically alters the biomechanics of movement, with devastating effects on limb function and quality of life. In some cases, these disruptions occur as a result of injury or disease. For example, rheumatoid arthritis makes joints excessively stiff, causing severe pain and increasing the muscle strength required to move. In other words, some connective tissue disorders, such as Ehlers-Danlos syndrome, make tissues excessively flexible, which makes joints unstable and leads to recurrent dislocations. In addition to disease or injury, disruptions to biological compliance often occur as a side effect of reconstructive procedures sometimes used to correct more severe bone and joint pathologies (Figures 1A, 1B, 1C). For example, in existing systems, titanium structures used in total joint replacements (Figure 1A) and constrained endoprostheses (Figure 1B) are much stiffer than the spongy cancellous bone they replace. This lack of compliance reduces the joint's ability to accommodate biomechanical defects that can lead to particulate-driven osteolysis (bone resorption) and aseptic loosening (Figure 2). In extreme cases, the lack of better options makes the destruction of biological compliance necessary. For example, arthrodesis (joint fusion) is often pursued as a last resort procedure in cases where state-of-the-art implants are inadequate or have already failed. Arthrodesis involves mechanically fixing bones so that they fuse together, effectively removing all compliance within the affected joint. Patients with extensive fusions in the legs face significant limitations in even basic walking, are unable to run or participate in athletic activities, and are more likely to develop arthritis in the adjacent non-fused joints. These reconstructive procedures are intended to salvage extreme cases.However, although these procedures may leave the patient with a viable limb attached to the body (viable), it is unable to support even basic mobility (non-functional). Patients with upper limb fusions face significant limitations in functional tasks that require positioning the arm or grasping with the hand. Summary of the Invention [Problem to be solved by the invention]

[0004] Thus, there is a need in the art for treatment options that restore joint function, allow for high levels of activity, and prevent unnecessary limb loss. [Means for solving the problem]

[0005] In some embodiments, the present invention provides an orthopedic device comprising: a first articular member having an inner surface and an outer surface; a second articular member having an inner surface and an outer surface; and at least one bending element having a first and a second end, the first end being coupled to the inner surface of the first articular member and the second end being coupled to the inner surface of the second articular member, The present invention relates to an orthopedic device, wherein first and second articulation members are configured to move relative to one another within a first degree of freedom.

[0006] In some embodiments, the at least one flexion element has at least a first flexion element and a second flexion element. In some embodiments, the at least one flexion element has at least a first flexion element, a second flexion element and a third flexion element. In some embodiments, the first and third flexion elements are oriented at the same angle relative to one another between the inner surfaces of the first and second articulation members. In some embodiments, the second flexion element is positioned between the first and third flexion elements, and the second flexion element is oriented at a different angle relative to the first and third flexion elements between the inner surfaces of the first and second articulation members.

[0007] In some embodiments, the first articular member has a top region, a bottom region and a central region between the top and bottom regions along its length, the second articular member has a top region, a bottom region and a central region between the top and bottom regions along its length, a first bending element is coupled at its first end to an inner surface of the bottom region of the first articular member and at its second end to an inner surface of the top region of the second articular member, a second bending element is coupled at its first end to an inner surface of the central region of the first articular member and at its second end to an inner surface of the central region of the second articular member, and a third bending element is coupled at its first end to an inner surface of the bottom region of the first articular member and at its second end to an inner surface of the top region of the second articular member.

[0008] In some embodiments, the device further comprises a first tissue anchor extending from an outer surface of the first articular member and a second tissue anchor extending from an outer surface of the second articular member, hi some embodiments, the first and second tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

[0009] In some embodiments, the first and second articulation members each have a curvature along its length including a top region, a middle region and a bottom region. In some embodiments, the first and second articulation members are oriented relative to one another such that the top region of the second articulation member overlaps with the bottom region of the first articulation member. In some embodiments, the at least one flexion element is configured to deform when the first articulation member moves relative to the second articulation member within a first degree of freedom. In some embodiments, the first degree of freedom is a translational degree of freedom.

[0010] In some embodiments, the at least one flexion element comprises a plurality of flexion elements. In some embodiments, the plurality of flexion elements are oriented at the same angle relative to one another between the inner surfaces of the first and second articulation members. In some embodiments, the plurality of flexion elements are positioned equidistant radially about a central axis passing through the first and second articulation members.

[0011] In some embodiments, the device further comprises a central opening in the first articular member such that the first articular member forms a ring, and a central post having a first end fixed to or adjacent to an inner surface of the second articular member and a second end extending through the opening in the first articular member such that the first articular member can rotate about the post. In some embodiments, the device further comprises a housing enclosing at least the first articular member, the second articular member and the plurality of flexion elements, one articular member being fixed to the housing.

[0012] In some embodiments, the device further comprises a first tissue anchor coupled to the second end of the central post and a second tissue anchor coupled to an outer surface of the second articulation member. In some embodiments, the device further comprises a first tissue anchor coupled to the second end of the central post and a second tissue anchor coupled to the housing. In some embodiments, the housing further comprises at least one recess, the second articulation member further comprises at least one tab extending from the outer surface of the second articulation member and positioned within the at least one recess of the housing, the at least one recess sized to allow a limited range of movement of the at least one tab within the at least one recess when the second articulation member is rotated relative to the first articulation member.

[0013] In some embodiments, the plurality of flexion elements are configured to deform when the first articulation member moves within a first degree of freedom relative to the second articulation member. In some embodiments, the first degree of freedom is a rotational degree of freedom. In some embodiments, the device further comprises at least one range limiting element configured to limit movement of the first articulation member relative to the second articulation member to within the first degree of freedom. In some embodiments, the device further comprises at least one range limiting element configured to limit movement of the second articulation member relative to the first articulation member to within the first degree of freedom.

[0014] In some embodiments, the device further comprises at least one spring coupled to the first and second articulation members, the spring configured to deform upon movement of the first and second articulation members relative to one another. In some embodiments, the at least one spring comprises a first spring and a second spring, the first spring configured to provide a restoring torque to the orthopedic device and the second spring configured to store and return energy to the orthopedic device.

[0015] In some embodiments, the device further comprises a third articulation member having an inner surface and an outer surface; a fourth articulation member having an inner surface and an outer surface; at least one bending element having first and second ends, the first end being coupled to the inner surface of the third articulation member and the second end being coupled to the inner surface of the fourth articulation member; the third and fourth articulation members are configured to move relative to one another within a second degree of freedom different from a first degree of freedom of movement between the first and second articulation members; and the outer surface of the third articulation member is coupled to the outer surface of the second articulation member.

[0016] In some embodiments, the first and second degrees of freedom are each translational degrees of freedom. In some embodiments, the first degree of freedom is translational and the second degree of freedom is rotational. In some embodiments, the first and second degrees of freedom are each rotational degrees of freedom. In some embodiments, the device further comprises a first tissue anchor coupled to an outer surface of the first articular member and a second tissue anchor coupled to an outer surface of the fourth articular member. In some embodiments, the first and second tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

[0017] In some embodiments, the device includes a third articulation member having an inner surface and an outer surface, a fourth articulation member having an inner surface and an outer surface, a fifth articulation member having an inner surface and an outer surface, a sixth articulation member having an inner surface and an outer surface, at least one bending element having a first and second end, the first end being coupled to the inner surface of the third articulation member and the second end being coupled to the inner surface of the fourth articulation member, and at least one bending element having a first and second end, the first end being coupled to the inner surface of the fifth articulation member and the second end being coupled to the inner surface of the sixth articulation member. a flexion element, the flexion element being coupled to an inner surface of the sixth articulation member, the inner surface of the second articulation member being coupled to an outer surface of the third articulation member and the outer surface of the fourth articulation member being coupled to an inner surface of the fifth articulation member, the third and fourth articulation members being configured to move relative to each other in a second degree of freedom different from the first degree of freedom of movement between the first and second articulation members; and the fifth and sixth articulation members being configured to move relative to each other in a third degree of freedom different from the second degree of freedom of movement between the third and fourth articulation members.

[0018] In some embodiments, the first degree of freedom is a translational degree of freedom, the second degree of freedom is a rotational degree of freedom, and the third degree of freedom is a translational degree of freedom. In some embodiments, the first degree of freedom is a rotational degree of freedom, the second degree of freedom is a translational degree of freedom, and the third degree of freedom is a rotational degree of freedom. In some embodiments, the first, second, and third degrees of freedom are each translational degrees of freedom. The first, second, and third degrees of freedom are each rotational degrees of freedom.

[0019] In some embodiments, the device further includes a first tissue anchor extending from an outer surface of the first articular member and a second tissue anchor extending from an outer surface of the sixth articular member, In some embodiments, the first and second tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

[0020] In some aspects, the invention relates to a method for designing a compliant implantable prosthesis comprising: performing neuromuscular-skeletal (NMS) modeling of a subject to identify anatomical constraints and compliance of desired degrees of freedom for an implant; generating a rough approximation of the mechanism geometry required to create the desired compliance space by using free and constraint topology (FACT); creating a parameterized finite element model (FEM) of a generic mechanism from a quasi-static mechanical model of the implant under loads representative of those encountered during walking; and refining the mechanism geometry by adjusting the shape of the implant.

[0021] The following detailed description of the embodiments of the invention will be better understood when read in conjunction with the accompanying drawings, in which it should be understood, however, that the invention is not limited to the precise arrangements and instrumentality of the embodiments shown in the drawings. [Brief description of the drawings]

[0022] [Figure 1A-1C] 1A-1C depict current treatments for limb pathology. FIG. 1A depicts a joint replacement that relies on ligaments for stability and is subject to friction / sliding wear. FIG. 1B depicts a constrained endoprosthesis that is inherently stable and subject to friction / sliding wear and overconstraint. FIG. 1C depicts a fusion therapy that is stable and viable but non-functional. All of these treatment options produce unnatural limb compliance. [Diagram 2] FIG. 2 illustrates a rotating hinge total knee prosthesis. [Figure 3A] Figures 3A-3B depict a one degree of freedom implementation of an exemplary implant device of the present invention: Figure 3A depicts an exemplary non-deformable implant device of the present invention. [Figure 3B] FIG. 3B illustrates an exemplary modified implant device of the present invention. [Figure 3C] Figures 3C-3L depict various embodiments of a compliant mechanism for an implant device of the present invention: Figure 3C depicts a side view of a compliant mechanism for an implant device of the present invention. [Figure 3D] FIG. 3D illustrates a perspective view of a compliant mechanism for an implant device of the present invention. [Figure 3E] FIG. 3E illustrates a side view of an exemplary three-piece compliant mechanism for an implant device of the present invention. [Figure 3F] FIG. 3F illustrates a perspective view of an exemplary three-piece compliant mechanism for an implant device of the present invention. [Figure 3G] FIG. 3G illustrates an exploded perspective view of an exemplary three-piece compliant mechanism for an implant device of the present invention. [Fig. 3H-3I]3H and 3I illustrate finite element analyses for ankle load validation of an exemplary non-deformable compliant mechanism for an implant device of the present invention. [Fig. 3J-3K] Figures 3J and 3K depict perspective and side views of a compliant mechanism for an implant device of the present invention. [Figure 3L] FIG. 3L illustrates a finite element analysis for ankle load validation of an exemplary deformable compliant mechanism for an implant device of the present invention. [Figure 4A-4F] 4A-4F depict an exemplary implant device of the present invention applied to an ankle joint. FIG. 4A depicts a side view of an exemplary non-deformed implant device of the present invention applied to an ankle joint. FIG. 4B depicts a perspective view of an exemplary non-deformed implant device of the present invention applied to an ankle joint. FIG. 4C depicts a perspective view of an exemplary non-deformed implant device of the present invention applied to an ankle joint. FIG. 4D depicts a perspective view of an exemplary non-deformed implant device of the present invention with a cover for protecting the surrounding tissue of the ankle joint. FIG. 4E depicts a perspective view of an exemplary non-deformed implant device of the present invention applied to an ankle joint. FIG. 4F depicts a side view of an exemplary non-deformed implant device of the present invention applied to an ankle joint. [Figure 5A] Figures 5A-5D depict an exemplary implant device of the present invention: Figure 5A depicts a perspective view of an exemplary non-deformable implant device of the present invention. [Figure 5B] FIG. 5B illustrates a perspective view of an exemplary non-deformable implant device of the present invention. [Figure 5C] FIG. 5C illustrates a side view of an exemplary non-deformable implant device of the present invention. [Figure 5D] FIG. 5D illustrates a finite element analysis of ISO ankle loading for an exemplary implant device of the present invention. [Figure 6A-6B] 6A-6B depict an exemplary modular implant device of the present invention. Figure 6A depicts an exploded perspective view of an exemplary modular implant device of the present invention applied to an ankle joint. Figure 6B depicts a perspective view of an exemplary assembled modular implant device of the present invention applied to an ankle joint. [Figure 7] FIG. 7 illustrates a finite element analysis of ISO ankle loading for an exemplary implant device of the present invention. [Figure 8A-8B] 8A-8B depict an exemplary implant device of the present invention. Fig. 8A depicts an exemplary 2-DOF implant device of the present invention applied to the ankle and subtalar joint. Fig. 8B depicts an exemplary 2-DOF implant device of the present invention applied to the ankle and subtalar joint deforming under load. [Figure 9] FIG. 9 illustrates a perspective view of an exemplary two degree of freedom implant device of the present invention. [Figure 10A-10D] 10A-10D depict an exemplary 2 degree of freedom implant device of the present invention applied to the ankle and subtalar joint. FIG. 10A depicts a side view of an exemplary non-deformable device of the present invention. FIG. 10B depicts a front view of an exemplary non-deformable device of the present invention. FIG. 10C depicts a posterior view of an exemplary non-deformable device of the present invention. FIG. 10D depicts a medial view of an exemplary non-deformable device of the present invention. [Figures 11A-11D] 11A-11D depict an exemplary two degree of freedom implant device of the present invention applied to the ankle and subtalar joint. FIG. 11A depicts a lateral view of an exemplary deformable device of the present invention (dorsiflexion). FIG. 11B depicts an anterior view of an exemplary deformable device of the present invention (valgus). FIG. 11C depicts a posterior view of an exemplary deformable device of the present invention (varus). FIG. 11D depicts a medial view of an exemplary deformable device of the present invention (plantar flexion). [Figure 12] FIG. 12 illustrates an exemplary one degree of freedom implant device of the present invention designed for moderate compressive loads and high range of motion. [Figure 13] FIG. 13 illustrates an exemplary coil spring that can be used in conjunction with the implant device of the present invention to increase energy storage capacity. [Figure 14A-14D] Figures 14A-D depict exemplary two degree of freedom implementations of implant architectures: Figure 14A depicts a cross-axis pivot architecture; Figure 14B depicts a cable suspended architecture; Figure 14C depicts a parallel leaf spring and cross-axis pivot architecture; and Figure 14D depicts a cross-axis pivot architecture. [Figure 15A] FIG. 15A is a perspective view of an exemplary implant device of the present invention. [Figure 15B] FIG. 15B illustrates a finite element analysis of the rotational loading of an exemplary implant device of the present invention. [Figure 15C] FIG. 15C illustrates a finite element analysis of the rotational loading of an exemplary implant device of the present invention. [Figure 16] FIG. 16 is a perspective view of an exemplary implant device of the present invention. [Figure 17A] FIG. 17A illustrates an exploded perspective view and cutaway view of an exemplary implant device of the present invention. [Figure 17B] FIG. 17B illustrates a cutaway and perspective view of an exemplary compliant mechanism for an exemplary implant device of the present invention. [Figure 17C] FIG. 17C illustrates a cutaway and perspective view of an exemplary implant device of the present invention. [Figure 17D] FIG. 17D illustrates a cutaway and perspective view of an exemplary compliant mechanism of an exemplary implant device of the present invention. [Figure 17E] FIG. 17E illustrates an overhead view of an exemplary implant device of the present invention. [Figure 18A] FIG. 18A illustrates an exploded side view of an exemplary implant device of the present invention. [Figure 18B] FIG. 18B illustrates a finite element analysis of the rotational loading of an exemplary implant device of the present invention. [Figures 19A-19D] 19A-19D depict an exemplary implant device of the present invention. FIG. 19A depicts a side view of an exemplary implant device of the present invention. FIG. 19B depicts a bottom perspective view of an exemplary implant device of the present invention. FIG. 19C depicts a top perspective view of an exemplary implant device of the present invention. FIG. 19D depicts a bottom perspective view of an exemplary implant device of the present invention. [Fig. 19E-19H] Figures 19E-19H depict an exemplary implant device of the present invention. Figure 19E depicts a perspective view of an exemplary implant device of the present invention. Figure 19F depicts a perspective view of a cross-section of an exemplary implant device of the present invention. Figure 19G depicts a side view of a cross-section of an exemplary implant device of the present invention. Figure 19H depicts a perspective cutaway view of an exemplary implant device of the present invention without an outer shell. [Figure 20A] Figures 20A-20H depict an exemplary two degree of freedom implant device of the present invention: Figure 20A depicts a side view of an exemplary implant device of the present invention. [Figure 20B] FIG. 20B illustrates a perspective view of an exemplary implant device of the present invention. [Figure 20C] FIG. 20C illustrates a side view of an exemplary implant device of the present invention. [Figure 20D] FIG. 20D illustrates a front view of an exemplary implant device of the present invention. [Figure 20E] FIG. 20E illustrates a perspective view of an exemplary implant device of the present invention. [Figure 20F] FIG. 20F illustrates a side view of an exemplary implant device of the present invention. [Figure 20G] FIG. 20G illustrates a perspective view of an exemplary implant device of the present invention. [Figure 20H] FIG. 20H illustrates a rear view of an exemplary implant device of the present invention. [Figure 21A]Figures 21A-21D depict finite element analysis of the loading of an exemplary implant device of the present invention: Figure 21A depicts a finite element analysis of the loading of an exemplary non-deformable implant device of the present invention. [Figure 21B] FIG. 21B illustrates a finite element analysis of the loading of an exemplary implant device of the present invention. [Figure 21C] FIG. 21C illustrates a finite element analysis of the loading of an exemplary variant implant device of the present invention. [Figure 21D] FIG. 21D illustrates a finite element analysis of the loading of an exemplary variant implant device of the present invention. [Figure 22A] Figures 22A-22G depict an exemplary 3 degree of freedom implant device of the present invention: Figure 22A depicts a perspective view of an exemplary 3 degree of freedom implant device of the present invention. [Figure 22B] FIG. 22B illustrates a side view of an exemplary three degrees of freedom implant device of the present invention. [Figure 22C] FIG. 22C illustrates a perspective view of an exemplary three degrees of freedom implant device of the present invention. [Figure 22D] FIG. 22D illustrates a side cutaway view of an exemplary three degree of freedom implant device of the present invention. [Figure 22E] FIG. 22E illustrates a perspective cutaway view of an exemplary three degrees of freedom implant device of the present invention. [Figure 22F] FIG. 22F illustrates an overhead view of an exemplary 3-DOF implant device of the present invention. [Figure 22G] FIG. 22G illustrates a side view of an exemplary three degrees of freedom implant device of the present invention. [Figure 23A] 23A-23L depict an exemplary implant device of the present invention for an animal model: FIG 23A depicts an exploded perspective view of an exemplary implant device of the present invention for an animal model; [Figure 23B] FIG. 23B depicts a side view of an exemplary implant device of the present invention for use in an animal model. [Figure 23C]FIG. 23C illustrates a side view of an exemplary implant device of the present invention for an animal model with a cover to protect the surrounding tissue of the joint. [Figure 23D] FIG. 23D illustrates a side view of an exemplary implant device of the present invention for an animal model without a cover. [Figure 23E] FIG. 23E depicts an enlarged side view of an exemplary implant device of the present invention for an animal model with a cover to protect the surrounding tissue of the joint. [Figure 23F] FIG. 23F depicts an enlarged side view of an exemplary implant device of the present invention for an animal model without a cover. [Figure 23G] FIG. 23G depicts a perspective view of an exemplary implant device of the present invention for an animal model without a cover. [Figure 23H] FIG. 23H depicts a perspective view of an exemplary implant device of the present invention for an animal model with a cover to protect the surrounding tissue of the joint. [Figure 23I] FIG. 23I depicts an enlarged perspective view of an exemplary implant device of the present invention for an animal model without a cover. [Figure 23J] FIG. 23J depicts an enlarged perspective view of an exemplary implant device of the present invention for an animal model with a cover to protect the surrounding tissue of the joint. [Figure 23K] FIG. 23K depicts an enlarged perspective view of an exemplary implant device of the present invention for use in an animal model. [Figure 23L] FIG. 23L depicts an enlarged side view of an exemplary implant device of the present invention for use in an animal model. [Figure 24] FIG. 24 depicts a schematic diagram of an exemplary device of the present invention in use with an external exoskeleton. [Diagram 25] FIG. 25 is a flow chart depicting an exemplary method for facilitating the design of a compliant implant for limb reconstruction. [Figure 26A]Figures 26A-B depict exemplary drill guides for implantation of at least one anchor or rod of the present invention. Figure 26A shows a calcaneal drill guide. [Figure 26B] FIG. 26B shows a midfoot drill guide. [Fig. 27A-27F]

[0023] Figures 27A-F depict preliminary modeling and experimental studies of an exemplary implant device of the present invention. Figure 27A depicts ankle-hindfoot implant design. Figure 27B depicts finite element analysis of ISO standard ankle loading. Figure 27C depicts bench-top evaluation of preliminary mechanisms. Figure 27D depicts bench-top evaluation of preliminary mechanisms. Figure 27E depicts bench-top evaluation of preliminary mechanisms. Figure 27F depicts cadaver dissection to assess potential distal fixation sites. [Figure 28] FIG. 28 illustrates the cadaveric dissection and placement of an exemplary implant device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] It should be understood that the figures and description of the present invention have been simplified for the purpose of illustrating elements relevant to a clear understanding of the present invention, while omitting many other elements found in the field of orthopedic joint replacement and implantable prostheses for clarity. Those skilled in the art may recognize that other elements and / or steps are desirable and / or required in implementing the present invention. However, a discussion of such elements and steps is not provided herein because such elements and steps are well known in the art and because they do not facilitate a better understanding of the present invention. The disclosure herein is directed to all such variations and modifications to such elements and methods that are known to those skilled in the art.

[0024] definition Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. Although any methods and materials similar or equivalent to those described herein can be used in the practice of testing the present invention, exemplary materials and methods are described herein. In describing and claiming the present invention, the following terms shall be used.

[0025] Also, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0026] As used herein, the articles "a" and "an" are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0027] As used herein, "about" when referring to a measurable value such as an amount, duration, and the like, is intended to encompass variations of ±20%, ±10%, ±5%, ±1% or ±0.1% from the stated value, as such variations are appropriate.

[0028] The terms "patients," "subject," "individual," and the like are used interchangeably herein and refer to any animal suitable for the systems, devices, and methods described herein. A patient, subject, or individual may be a mammal, and in some cases, a human.

[0029] Range: Throughout this disclosure, various aspects of the invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be considered as an inflexible limitation on the scope of the invention. Thus, the description of a range should be considered to have specifically disclosed all possible subranges as well as individual numerical values ​​within that range. For example, the description of a range such as 1-6 should be considered to have specifically disclosed subranges such as 1-3, 1-4, 1-5, 2-4, 2-6, 3-6, etc., as well as individual numbers within that range, such as 1, 2, 2.7, 3, 4, 5, 5.3, and 6. This is true regardless of the breadth of the range.

[0030] As used herein, the term "connected to" may mean connected by direct contact or mechanically connected through one or more intermediate components.

[0031] Orthopedic joint replacement implants and implantable prostheses The present invention provides, in part, an orthopedic implant that includes one or more compliant mechanisms. As contemplated herein, a compliant mechanism utilizes a flexible structure, also described herein as a flexing element, that transmits motion through bending and / or elastic deformation of the flexible structure. In some embodiments, a compliant mechanism achieves its motion from the relative flexibility of structural members rather than from rigid joints alone. In some embodiments, a compliant mechanism can be designed to allow motion (both linear and rotational) in some directions and be functionally rigid in other directions. In some embodiments, a compliant mechanism can be composed of a single piece or many pieces coupled together. For example, a compliant mechanism may include at least one flexible structure. However, it should be recognized that a compliant mechanism may include any number of flexible structures. For example, the compliant mechanism may include at least two flexible structures, at least three flexible structures, at least four flexible structures, at least five flexible structures, at least six flexible structures, at least seven flexible structures, at least eight flexible structures, at least nine flexible structures, at least ten flexible structures, at least twenty flexible structures, at least fifty flexible structures, or at least one hundred flexible structures. In some embodiments, the orthopedic implant devices of the present invention are configured to replace or augment biological joint function. In some embodiments, the devices of the present invention are configured to allow flexible movement in one or more engineered degrees of freedom (both translational (e.g., linear) and rotational) and stiffness in all remaining degrees of freedom. This configuration may allow for increased longevity and joint stability. In some embodiments, the devices of the present invention are configured to redesign limb compliance. In some embodiments, the devices of the present invention are configured to correct pathological compliance. In some embodiments, the devices of the present invention provide pain relief.In some embodiments, the devices are configured to prevent amputation. In some embodiments, the devices mimic or augment natural biological compliance, thereby restoring joint function and eliminating pain. In some embodiments, the devices are comprised of flexible elements that deform under load to produce the desired motion. In some embodiments, the devices precisely guide motion without the mechanical complexity of bearings and linkages. In some embodiments, the devices generate essentially no or negligible friction and therefore negligible wear. In some embodiments, the devices have inherent stability, which is important because it allows compromised bone to be resected without destabilizing the joint. In some embodiments, the devices store energy and generate restoring torque, opening the door for implantable devices to function as prostheses, restoring lost limb or prosthetic function, and augmenting or compensating function within intact biological limbs. This mechanism benefits localized muscle pathology by reducing compensatory muscle function required to support walking. In some embodiments, the devices are configured to withstand cyclical walking loads.

[0032] 3A-3B, an exemplary implant device having a cross-axis flexure pivot is shown. In some embodiments, the device 100 includes a first articular member 102, a second articular member 104, at least one flexure element (e.g., a first flexure element 106, a second flexure element 107, and a third flexure element 108), a proximal anchor 118, and a distal anchor 120.

[0033] In some embodiments, the present invention relates to an orthopedic device 100 including a first joint member 102 having an inner surface and an outer surface, a second joint member 104 having an inner surface and an outer surface, and at least one bending element having first and second ends, the first end being coupled to the inner surface of the first joint member 102 and the second end being coupled to the inner surface of the first joint member 104, wherein the first and second joint members are configured to move relative to each other within a first degree of freedom.

[0034] In some embodiments, the first joint member 102 and the second joint member 104 may have any shape known to one skilled in the art. In some embodiments, the first joint member 102 and the second joint member 104 may have a circular or rounded outer geometry to allow the first joint member 102 and the second joint member 104 to rotate smoothly about a center of rotation. In some embodiments, the first joint member 102 has a larger inner diameter than the second joint member 104. In some embodiments, this configuration has hard stops to limit movement to a range that would not overstress at least one flex element (e.g., the first flex element 106, the second flex element 107, the third flex element 108). In some embodiments, the first joint member 102 and the second joint member 104 may have any thickness in the range of approximately 0.05 to 10 mm. In some embodiments, the first articular member 102 and the second articular member 104 may have any width or diameter within the range of approximately 0.5-20 cm depending on the joint. In some embodiments, the thickness, width and / or diameter of the first articular member 102 and the second articular member 104 may be modified to change the overall behavior including, but not limited to, the range of motion, load bearing capacity, stiffness, center of rotation trajectory, etc. In some embodiments, the first articular member 102 and the second articular member 104 have a thickness, width and / or diameter that varies along their length. In some embodiments, the first articular member 102 and the second articular member 104 have a uniform thickness, width and / or diameter along their length. In some embodiments, the first articular member 102 and the second articular member 104 are substantially C-shaped to provide a certain stiffness in joint compression.

[0035] In some embodiments, the device 100 may further include at least one range-limiting element 103 configured to limit movement so that the device 100 is not subjected to undue stress or overstretching. In some embodiments, the at least one range-limiting element 103 includes a raised or extended portion along the length of the second articulation member 104, thus forming a hard stop configured to block further movement of a moving element, such as the leading edge 102a of the first articulation member 102. The hard stop may have any shape known to those skilled in the art. For example, the range-limiting element 103 may have one or more flat surfaces or faces against which the respective flat surfaces or faces of the moving elements press at the end of the range of motion. In some embodiments, the at least one range-limiting element 103 includes one or more hooks or overhangs that the respective hooks or overhangs of the moving elements capture at the end of the range of motion. In some embodiments, at least one range-limiting element 103 includes one or more linear or non-linear stiffening flexure elements, such as springs or compliant mechanisms, that include a range of motion that is limited, e.g., in full or partial compression and / or tension, at the ends of the range. In other embodiments, the range-limiting elements may include tabs or other extensions that fit within a corresponding opening or recess such that movement is limited when the tabs or other extensions contact the walls of the opening or recess.

[0036] The first articulation member 102 and the second articulation member 104 are configured to form a cross-axis pivot flexion, where the first articulation member 102 and the second articulation member 104 are each oriented in a manner such that their movement is along the same plane, allowing one degree of freedom. The first articulation member 102 includes a top region 110, a middle region 111, and a bottom region 112. The top region 110 is coupled to a proximal anchor 118 and is configured to move in the same plane relative to the second articulation member 104. The second articulation member 104 includes a top region 114, a middle region 115, and a bottom region 116. The bottom region 116 is coupled to a distal anchor 120 and is configured to move in the same plane relative to the first articulation member 102. The device 100 is configured such that the bottom region 116 of the second articular member 104 nests within the bottom region 112 of the first articular member 102. In some embodiments, the top region 110 of the first articular member 102 overlaps the top region 114 of the second articular member 104. In some embodiments, the first articular member 102 rotates within the second articular member 104.

[0037] Other hard stops or range limiting elements are contemplated herein. In some embodiments, the second articulation member 104 can be designed to press against the side of the base region 116 to prevent excessive stress on the mechanism from out-of-plane loads (e.g., in-page forces on the distal anchor 120). In some embodiments, a hard stop could be placed between the top region 110 and the top region 114 to prevent interference between the portions during large compressive loads and excessive tensile stress on the flexion elements. Such a hard stop could comprise a different material than the rest of the implant, for example, ultra-high molecular weight polyethylene.

[0038] In some embodiments, the first articular member 102 includes a top region 110, a bottom region 112 and a central region 111 between the top and bottom regions along its length, the second articular member 104 includes a top region 114, a bottom region 116 and a central region 115 between the top and bottom regions along its length, and the first bending element 106 is coupled at its first end to an inner surface of the bottom region of the first articular member 102 and at its second end to an inner surface of the second articular member 104. The first bending element 107 is connected at its first end to the inner surface of the central region of the first joint member 102 and at its second end to the inner surface of the central region of the second joint member 104, and the third bending element 108 is connected at its first end to the inner surface of the bottom region of the first joint member 102 and at its second end to the inner surface of the top region of the second joint member 104.

[0039] In some embodiments, the first articular member 102 and the second articular member 104 each have a curvature along their length including a top region, a middle region and a bottom region. In some embodiments, the first articular member 102 and the second articular member 104 are oriented relative to one another such that the top region of the second articular member 104 overlaps the bottom region of the first articular member 102.

[0040] In some embodiments, the at least one flexion element includes a first end of the flexion element connected to the first articulation member and a second end of the flexion element connected to the second articulation member. In some embodiments, the device 100 may have any number of flexion elements, where each flexion element forms a connection between the first and second articulation members. In some embodiments, the at least one flexion element includes a first flexion element 106, a second flexion element 107, and a third flexion element 108, where each flexion element 106, 107, and 108 has a respective first end connected to the first articulation member and a respective second end connected to the second articulation member. For example, the first flexion element 106 and the third flexion element 108 connect the bottom region 112 of the first articulation member 102 to the top region 114 of the second articulation member 104. In some embodiments, the connection point of the first and second flex elements 106 and 108 may be at the leading edge of the first and second articulation members 102 and 104, as shown in FIG. 3E. The second flex element 107 connects the first articulation member 102 to the second articulation member 104 at a point along their respective arc lengths. The first flex element 106 and the third flex element 108 may have the same structure and angular orientation, with the second flex element 107 being disposed between the first flex element 106 and the third flex element 108 and positioned at a different angle than the first and second flex elements 106 and 108. In some embodiments, at least one flex element is formed as one unit with the first articulation member 102 and / or the second articulation member 104. In some embodiments, at least one flexion element is formed separately from the first articular member 102 and / or the second articular member 104 and is later coupled to the first articular member 102 and / or the second articular member 104.

[0041] In some embodiments, the at least one flexure element is configured to deform when the first articulation member 102 moves in a first degree of freedom relative to the second articulation member 104. In some embodiments, the first degree of freedom is a translational degree of freedom. In some embodiments, the first degree of freedom is a rotational degree of freedom.

[0042] In some embodiments, the device 100 further includes a first tissue anchor (e.g., proximal anchor 118) extending from an outer surface of the first articular member 102, and a second tissue anchor (e.g., distal anchor 120) extending from an outer surface of the second articular member 104. In some embodiments, the first and second tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

[0043] 3C, 3D, 3J and 3K illustrate close-ups of a compliant mechanism similar to that shown in FIGS. 3A and 3B, with parts numbered the same for ease of explanation. In some embodiments, the device 100 includes a first articular member 102 and a second articular member 104 having a width 130 and a thickness 132. In some embodiments, the first articular member 102 and the second articular member 104 may have any thickness 132 in the range of approximately 0.05-10 mm. In some embodiments, the first articular member 102 and the second articular member 104 may have any width 130 or diameter in the range of approximately 0.5-20 cm depending on the joint. In some embodiments, the width, thickness and diameter of the first articular member 102 and the second articular member 104 may be modified to change the overall behavior, including but not limited to the range of motion, load bearing capacity, stiffness, center of rotation, etc., depending on the type of joint being replaced. In some embodiments, the first articular member 102 and the second articular member 104 have a variable width, thickness and / or diameter along their length. In some embodiments, the first articular member 102 and the second articular member 104 have a uniform width, thickness and / or diameter along their length.

[0044] As described herein, one or more bending elements are also referred to as blades. In some embodiments, the device 100 includes at least one bending element or blade, where the element or blade has a thickness 138, a width 140, a length 142, a relative angle 144, an articulation member angle 145, a fillet length 146, and a fillet width 141. In some embodiments, the first bending element 106, the second bending element 107, and the third bending element 108 may have the same thickness. In some embodiments, the first bending element 106 and the third bending element 108 may have a greater thickness than the second bending element 107. In some embodiments, the second bending element 107 may have a greater thickness than the first bending element 106 and the third bending element 108. In some embodiments, the first bending element 106, the second bending element 107, and the third bending element 108 may have any thickness 138 within a range of approximately 0.005 to 50 mm. In some embodiments, the first flex element 106, the second flex element 107, and the third flex element 108 may have a thickness that varies along its length. For example, the blade may include fillets or thicker regions 146 along its length such that the blade has an increased thickness 138 at the connection point to the first or second articulation member 102 or 104. In such embodiments, the blade utilizes a thinner central region 147 of its length to facilitate the desired deformation during bending. In some embodiments, the first flex element 106, the second flex element 107, and the third flex element 108 may have the same width. In some embodiments, the first flex element 106 and the third flex element 108 may be wider than the second flex element 107. In some embodiments, the second flex element 107 may be wider than the first flex element 106 and the third flex element 108. In some embodiments, the first bending element 106, the second bending element 107, and the third bending element 108 may have widths that vary along their lengths. In some embodiments, the first bending element 106 and the third bending element 108 may have any width 140 within the range of approximately 0.1 to 10 cm.In some embodiments, the second bending element 107 may have any width 140 within the range of approximately 0.1 to 10 cm. In some embodiments, the first bending element 106, the second bending element 107, and the third bending element 108 may have the same length. In some embodiments, the first bending element 106 and the third bending element 108 may be longer than the second bending element 107. In some embodiments, the second bending element 107 may be longer than the first bending element 106 and the third bending element 108. In some embodiments, the first bending element 106 and the third bending element 108 may have any length 142 within the range of approximately 0.2 to 20 cm. In some embodiments, the second bending element 107 may have any length 142 within the range of approximately 0.2 to 20 cm. In some embodiments, the thickness 138, width 140, and length 142 of the first flexion element 106, second flexion element 107, and third flexion element 108 may be modified to change the overall behavior, including but not limited to the range of motion, load carrying capacity, stiffness, center of rotation orbit, etc. In some embodiments, the thickness 138, width 140, and length 142 of the first flexion element 106, second flexion element 107, and third flexion element 108 may be varied in at least one region of the flexion element.

[0045] In some embodiments, any two bending elements may have any angle 144 orientation relative to one another. For example, angle 144 may be between 0° and 180°, between 0° and 90°, between 0° and 60°, between 0° and 45°, between 0° and 30°, between 0° and 15°, or between 0° and 10°. In some embodiments, angle 144 may be 180° or less, 170° or less, 160° or less, 150° or less, 140° or less, 130° or less, 120° or less, 110° or less, 100° or less, 90° or less, 80° or less, 70° or less, 60° or less, 50° or less, 40° or less, 30° or less, 20° or less, 10° or less, 5° or less, 1° or less, or about 0°.

[0046] In some embodiments, the first and third flexion elements are oriented at the same articulation member angle 145 in relation to one another between the inner surfaces of the first articulation member 102 and the second articulation member 104. In some embodiments, the second flexion element 107 is positioned between the first flexion element 106 and the third flexion element 108, where the second flexion element 107 is oriented at a different angle in relation to the first flexion element 106 and the third flexion element 108 between the inner surfaces of the first articulation member 102 and the second articulation member 104.

[0047] In some embodiments, any flexion element may have any articulation member angle 145 relative to any articulation member. For example, angle 145 may be between 0° and 180°, between 0° and 90°, between 0° and 60°, between 0° and 45°, between 0° and 30°, between 0° and 15°, or between 0° and 10°. In some embodiments, angle 144 may be 180° or less, 170° or less, 160° or less, 150° or less, 140° or less, 130° or less, 120° or less, 110° or less, 100° or less, 90° or less, 80° or less, 70° or less, 60° or less, 50° or less, 40° or less, 30° or less, 20° or less, 10° or less, 5° or less, 1° or less, or about 0°.

[0048] In some embodiments, the bending element may include at least one fillet having any fillet length 146 within a range of approximately 0.1 to 50 mm. In some embodiments, the bending element may have any fillet width 141 within a range of approximately 0.1 to 50 mm. In some embodiments, the bending element may have any fillet thickness 138 within a range of approximately 0.1 to 50 mm. In some embodiments, the bending element may have any fillet radius within a range of approximately 0.1 mm to 10 cm.

[0049] Aspects of the present invention relate to a compliant mechanism involving a multi-piece assembly of the implant device of the present invention. FIGS. 3E-3G illustrate a close-up of a compliant mechanism similar to that shown in FIGS. 3A and 3B, and use the same numbered parts for ease of explanation. Shown in FIGS. 3E and 3F is the assembled compliant mechanism. Shown in FIG. 3G is an exploded view of the compliant mechanism. In some embodiments, the compliant mechanism includes at least one main component. For example, in some embodiments, the compliant mechanism includes a first component 101, a second component 103, and a third component 105. In some embodiments, the first component 101 includes a first articular member 102a and a second articular member 104a connected by a first flex element 106. In some embodiments, the second component 103 includes a first articular member 102b and a second articular member 104b connected by a second flex element 107. In some embodiments, the third component 105 includes a first articulation member 102c and a second articulation member 104c connected by a third flexure element 108. In some embodiments, the first component 101, the second component 103, and the third component 105 have mating surfaces that allow for a friction fit of the components when assembled. In some embodiments, the compliant mechanism has features for securing the components together with a friction fit, such as, but not limited to, slots, grooves, holes, channels, notches, tongues, pins, pegs, shanks, wedges, blades, and / or stabs. For example, in some embodiments, the compliant mechanism has a peg 150 and holes 152 such that multiple pegs mate with multiple holes to secure the components together. The pegs 150 and holes 152 may be configured to allow the components including the first articular member 102 (102a, 102b, 102c) and the second articular member 104 (104a, 104b, 104C) to be fixedly attached yet still allow at least one bending element to bend.In some embodiments, the shape of the pegs 150 and / or holes 152 are round, square, oval, polygonal, and any other shape known to one of ordinary skill in the art. In some embodiments, the components including the first articular member 102 and the second articular member 104 may be welded together (including by electron beam or laser welding).

[0050] In some embodiments, the first flex element 106, the second flex element 107, and the third flex element 108 may function as springs and cross each other independently to provide a rotation axis for the first articulation member 102 and the second articulation member 104. In some embodiments, the first flex element 106, the second flex element 107, and the third flex element 108 may cross at any point along their length. In some embodiments, the center of rotation may be approximated by the crossing point, but moves as the flex elements deform. In some embodiments, the flex elements may have different lengths and may be oriented at any angle, where changing any of these characteristics affects the mechanical behavior of the mechanism. In some embodiments, the flex elements may be oriented in such a way that the first flex element 106, the second flex element 107, and the third flex element 108 form a crossing pattern. In some embodiments, the flexure elements may be oriented such that the first flexure element 106, the second flexure element 107 and the third flexure element 108 are substantially parallel.

[0051] In any of the embodiments described herein, the articular member may be made of any material known to those skilled in the art, including but not limited to pure metals, metal alloys, polymers, ceramics, metallic glasses, or combinations thereof. In some embodiments, the articular member may be made of a biocompatible material. In some embodiments, the articular member may be coated in a biocompatible material. In some embodiments, the articular member may include a titanium alloy, including but not limited to Ti6-Al4v. In some embodiments, the articular member may include Cr-Co. In some embodiments, the articular member may include a stainless steel, including but not limited to SS316. In some embodiments, the articular member may include polyethene or ultra-high molecular weight polyethylene.

[0052] In some embodiments, device 100 is configured such that when the mechanism is in compression, first bending element 106, second bending element 107, and third bending element 108 are in tension.

[0053] In any of the embodiments described herein, the bending element may be made of any material known to one of ordinary skill in the art, including, but not limited to, pure metals, metal alloys, polymers, ceramics, metallic glasses, or combinations thereof. In some embodiments, the bending element may include a biocompatible material. In some embodiments, the bending element may be coated in a biocompatible material. In some embodiments, the bending element may include Ti6-Al4v. In some embodiments, the bending element may include Cr-Co. In some embodiments, the bending element may include SS316.

[0054] In some embodiments, device 100 is configured to tolerate high compressive loads, hi some embodiments, device 100 is configured to receive loads in the range of approximately 10-30,000N.

[0055] A proximal or tissue anchor 118 is attached to the first articular member 102 at one end and is configured to attach the device 100 to the bone at the opposite end. A distal or tissue anchor 120 is attached to the second articular member 104 at one end and is configured to attach the device 100 to the bone at the opposite end. In some embodiments, the device 100 may be secured to the surrounding bone through the proximal and distal anchors 118, 120 via any method known to those skilled in the art, including but not limited to intramedullary fixation, extramedullary fixation, surface osseointegration, and the like. In some embodiments, the device may be secured to the surrounding bone using any of a number of strategies for intramedullary fixation, such as long stems, short stems, threaded intramedullary screws, press-fit or cemented stems, nails, threaded or threaded implants, compression type implants, implants porous coated for bone ingrowth, and the like. In some embodiments, intraosseous rods or pins may be used for fixation to cancellous bone.

[0056] 4A-4F, the device 100 is secured to the surrounding bone through a proximal anchor 118 and a distal anchor 120 by intramedullary fixation. In some embodiments, the device 100 includes a first articular member 102, a second articular member 104, at least one bending element, a proximal anchor 118, at least one distal anchor 120, and a cover 122. The cover 122 is configured to at least partially encase the first articular member 102 and the second articular member 104 and to protect the surrounding soft tissue. In some embodiments, the cover 122 may include small gaps that allow fluid to pass therethrough. In some embodiments, the cover 122 may have a plurality of pores that allow fluid to pass therethrough to the first articular member 102 and the second articular member 104. In some embodiments, the cover 122 may be made of any material known to those skilled in the art, including but not limited to pure metals, metal alloys, polymers, ceramics, metallic glasses, or combinations thereof. In some embodiments, the cover 122 may include a biocompatible material. In some embodiments, the cover 122 may be coated in a biocompatible material. In some embodiments, the cover 122 may include Ti6-Al4v. In some embodiments, the cover 122 may include Cr-Co. In some embodiments, both devices may include SS316.

[0057] 5A-5B depict an exemplary non-deformable implant device 100 of the present invention similar to that shown in FIGS. 3A and 3B, and use the same numbered parts for ease of explanation.

[0058] In some embodiments, the device 100 further includes a first distal anchor 120a and a second distal anchor 120b. In some embodiments, the first distal anchor 120a has three pegs or rods protruding on its distal end. In some embodiments, the three rods of the first distal anchor 120a are intended for implantation into three of the cuneiform bones of the foot. In some embodiments, the first distal anchor 120a and the second distal anchor 120b have a relative angle 149. In some embodiments, the angle 149 is at least 5 degrees. In some embodiments, the angle 149 is at least 10 degrees. In some embodiments, the angle 149 is at least 15 degrees. In some embodiments, the angle 149 is at least 20 degrees. In some embodiments, the angle 149 is at least 25 degrees. In some embodiments, the angle 149 is in the range of 5 degrees to 40 degrees. In some embodiments, the angle 149 is at least 10 degrees and 30 degrees. In some embodiments, the first distal anchor 120a and the second distal anchor 120b diverge in multiple planes. In some embodiments, the first distal anchor 120a and / or the second distal anchor 120b are threaded screws that may be fixedly attached to the distal end of the device 100. In some embodiments, the first distal anchor 120a comprises a peg or rod placed in the bones of the midfoot (cuneiform, navicular). In some embodiments, these pegs or rods may be cemented, porous coated, press-fit, screwed, etc.

[0059] In some embodiments, at least one coil spring 210 may be used in conjunction with the device 100 (FIGS. 5B and 5C). In some embodiments, the coil spring 210 has a first articulation member 212, a second articulation member 204, and at least one flex element connecting the first and second articulation members. In some embodiments, the coil spring 220 has a rotational flex with at least + / - 10 degrees of motion. In some embodiments, the coil spring 220 has a range of motion of 5-10 degrees. In some embodiments, the coil spring 220 has a range of motion of 10-15 degrees. In some embodiments, the coil spring 220 has a range of motion of 20-25 degrees. In some embodiments, the coil spring 220 has a range of motion of 25-30 degrees. In some embodiments, the coil spring 220 has a range of motion of 30-45 degrees. In some embodiments, the first articulation member 212 may be attached to the second articulation member 104 and the second articulation member 214 may be attached to the first articulation member 102 such that translational movement of the members causes rotational deformation of the coil spring 210. In some embodiments, the first articulation member 212 may be attached to the first articulation member 102 and the second articulation member 214 may be attached to the second articulation member 104. In further embodiments, this could be accomplished using linear springs placed between the mechanism and each hard stop, where one spring is to induce the movement and the second spring is to store and return energy. In some embodiments, the second springs may have any shape known to those skilled in the art, including but not limited to coil springs, multiple linear springs, cross axis pivots, etc.

[0060] Aspects of the present invention relate to modular implant devices to properly size and fit the device to the patient. The modularity of the implant device also aids in implantation of the device and allows for possible repair or revision procedures without disturbing the surrounding bone. Figures 6A-6B depict an exemplary modular implant device 100 of the present invention. Figure 6A depicts an exploded perspective view of an exemplary modular implant device 100 in which the proximal anchor, bending element, and distal anchor are separate components that are fixedly attached or coupled together during a surgical procedure. Figure 6B depicts a perspective view of an assembled modular implant device 100 of the present invention applied to an ankle joint. In some embodiments, the proximal anchor 118 and the distal anchor 120 are separate components but may be fixedly attached or coupled to the first articular member 102 and the second articular member 104, respectively. Separate components may be fixedly attached or connected by any method known to those skilled in the art, including but not limited to adhesives, cements, glues, friction fits, screws, bolts, threads, slots, tongue and grooves, pegs, holes, and the like.

[0061] Each anchor has a proximal region for engaging at least one articular member and a distal region for engaging bone or tissue. In some embodiments, the proximal anchor 118 includes a proximal engagement region 118a for engaging the first articular member 102 and a distal engagement region 118b for engaging bone or other tissue. In some embodiments, the distal anchor 120 includes a proximal engagement region 120a for engaging the second articular member 104 and a distal engagement region 120b for engaging bone or other tissue.

[0062] In one exemplary embodiment, the distal anchors 120 may be attached to the calcaneus, navicular and cuneiform bones when the device 100 is used in the ankle-hindfoot joint.

[0063] In some embodiments, the device 100 may be secured to the surrounding bone through the proximal anchor 118 and the distal anchor 120 by extramedullary fixation. In some embodiments, the device may be secured to the surrounding bone using any of a number of strategies for intramedullary fixation, including but not limited to plates and screws. In some embodiments, conventional orthopedic hardware may be used for extraosseous fixation, including but not limited to customized plates and screws, standardized plates and screws, etc. In some embodiments, the device 100 may be secured to the surrounding bone by ingrowth on a porous surface. In some embodiments, the bone surface may be pre-treated intraoperatively for ingrowth onto the porous surface (e.g., a porous coating for bone ingrowth as in an acetabular cup for a total hip replacement). In some embodiments, initial stability may be aided by combination with any other fixation tactics.

[0064] In some embodiments, the proximal anchor 118 and the distal anchor 120 may have any shape / geometry known to one of skill in the art, including but not limited to cylindrical, cubical, and the like.

[0065] In some embodiments, the proximal anchor 118 and the distal anchor 120 may be made of any material, including, but not limited to, titanium, Ti6-Al4v, Cr-Co, SS316. In some embodiments, the proximal anchor 118 and the distal anchor 120 may be porous. In some embodiments, the proximal anchor 118 and the distal anchor 120 may be further coated with any material known to those skilled in the art, including, but not limited to, pure metals, metal alloys, polymers, ceramics, metallic glasses, or combinations thereof. In some embodiments, the proximal anchor 118 and the distal anchor 120 may include titanium. In some embodiments, the proximal anchor 118 and the distal anchor 120 may include a biocompatible material.

[0066] In some embodiments, the device 100 may be used for common orthopedic procedures including, but not limited to, total hip replacement, total knee replacement, total wrist replacement, total ankle replacement, total shoulder replacement, and the like. In some embodiments, the joint (e.g., foot) may be surgically altered to facilitate fixation. In one exemplary embodiment, the joint may be fused to eliminate movement that may be detrimental to bone ingrowth and osseointegration. In some embodiments, bones may be fused together to create a larger bone surface onto which an implant could be fixed. In some embodiments, bone may be removed or repositioned to create more space for the implant.

[0067] Referring now to FIG. 8A, the implant may include a first compliant mechanism in series with a second compliant mechanism to create at least a two degree of freedom system. In some embodiments, the device of the present invention may be combined in series with a second compliant mechanism to create two degrees of freedom in the ankle and subtalar joint (FIG. 8B). In some embodiments, the second degree of freedom may be a second cross-axis pivot in tension. In some embodiments, the second degree of freedom may be any other mechanism known to those skilled in the art. In some embodiments, the implant includes a first compliant device 100a, which may be similar to device 100 as described and uses the same numbered parts for ease of description. However, instead of being engaged with a distal anchor, device 100a engages with a second compliant device 100b, which may be similar to device 100 as described and uses the same numbered parts for ease of description. Device 100b allows one degree of freedom, similar to 100a, but in another plane allowing a different range of motion or range of movement. In some embodiments, device 100b replaces distal anchor 118 of device 100a. In some embodiments, bottom region 116 of device 100a connects with top region 110 of device 100b.

[0068] In some embodiments, the device 100 further includes a third articulation member 124 having an inner surface and an outer surface, a fourth articulation member 126 having an inner surface and an outer surface, and at least one flexure element having a first and a second end, where the first end is coupled to the inner surface of the third articulation member 124 and the second end is coupled to the inner surface of the fourth articulation member 126, the third articulation member 124 and the fourth articulation member 126 are configured to move relative to each other in a second degree of freedom that is different from a first degree of freedom of movement between the first articulation member 102 and the second articulation member 104, and the outer surface of the third articulation member 124 is coupled to the outer surface of the second articulation member 104. In some embodiments, the first and second degrees of freedom are each translational degrees of freedom. In some embodiments, the first degree of freedom is a translational degree of freedom and the second degree of freedom is a rotational degree of freedom. In some embodiments, the first and second degrees of freedom are each rotational degrees of freedom.

[0069] In some embodiments, the device further includes a proximal tissue anchor (e.g., proximal anchor 118) extending from an outer surface of the first articular member 102 and at least one distal tissue anchor (e.g., first distal anchor 120a, second distal anchor 120b) extending from an outer surface of the fourth articular member 126. In some embodiments, the tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

[0070] 11A and 11D, the kinematics are shown for a compliant device 100a applied to the ankle joint. Referring to Figures 11C and 11B, the kinematics are shown for a compliant mechanism 100b applied to the ankle joint.

[0071] In some embodiments, device 100 may be used in ankle joints. In some embodiments, device 100 may be used to replace any joint in the body, including but not limited to joints of fingers, thumbs, hands, wrists, elbows, shoulders, toes, feet, ankles / subtalar, knees, hips, etc. In some embodiments, device 100 may be used to replace vertebrae in the back or neck.

[0072] In some embodiments, device 100 may be used in rehabilitation applications. In some embodiments, device 100 may be used in prevention / augmentation applications where no pathology has been diagnosed and the goal is to improve baseline function or prevent future pathology. In some embodiments, device 100 may be used to treat subjects with diagnosed pathology. In some embodiments, device 100 may be used for subjects seeking prophylactic injury prevention. In some embodiments, device 100 may be used to help subjects increase athletic performance beyond their baseline capabilities.

[0073] In some embodiments, device 100 may be used in tandem with an existing joint to manipulate the mechanical properties of the existing joint and store and return energy. In one exemplary embodiment, device 100 may be implanted in tandem with a joint in a subject with a weakened joint to generate a restoring torque around the joint, provide energy storage, and enable improved function.

[0074] 12, another exemplary implant device 200 is shown. In some embodiments, device 200 includes one first stage element 201, two second stage elements 203, and one third stage element 205. First stage element 201 is structurally and functionally similar to device 100 described elsewhere herein.

[0075] The second stage element 203 includes a first articular member 202, a second articular member 204, and a pair of intersecting flexure elements 206. In some embodiments, the first articular member 202 and the second articular member 204 may have any shape known to those skilled in the art. In some embodiments, the first articular member 202 and the second articular member 204 may have a circular or rounded outer geometry. In some embodiments, the first articular member 202 and the second articular member 204 may be made from any material known to those skilled in the art, including but not limited to pure metals, metal alloys, polymers, ceramics, metallic glasses, or combinations thereof. In some embodiments, the first articular member 202 and the second articular member 204 may include a biocompatible material. In some embodiments, the first articular member 202 and the second articular member 204 may be coated in a biocompatible material. In some embodiments, the first articular member 202 and the second articular member 204 may comprise Ti6-Al4v. In some embodiments, the first articular member 202 and the second articular member 204 may comprise Cr-Co. In some embodiments, the first articular member 202 and the second articular member 204 may comprise SS316.

[0076] A pair of bending elements 206 connect the first joint member 202 to the second joint member 204 such that one end of the bending element pair 206 is attached to the first joint member 202 and the other end is connected to the second joint member 204.

[0077] The flex element pairs 206 may have any thickness known to those of skill in the art. In some embodiments, the flex element pairs 206 may have the same thickness. In some embodiments, the flex element pairs 206 may have different thicknesses. In some embodiments, the flex element pairs 206 may have a thickness in the range of 0.005-5 mm. In some embodiments, the flex element pairs 206 may have a thickness that varies along their length. In some embodiments, the flex element pairs 206 may have any width known to those of skill in the art. In some embodiments, the flex element pairs 206 may have the same width. In some embodiments, the flex element pairs 206 may have different widths. In some embodiments, the flex element pairs 206 may have a width in the range of 0.1-10 cm. In some embodiments, the flex element pairs 206 may have a width that varies along their length. In some embodiments, the flex element pairs 206 may have any length known to those of skill in the art. In some embodiments, the flex element pairs 206 may have the same length. In some embodiments, the flexure element pairs 206 may have different lengths. In some embodiments, the flexure element pairs 206 may have lengths in the range of 0.2 to 20 cm.

[0078] In some embodiments, the thickness, width and length of the flexion element pair 206 may be modified to change the overall behavior, including but not limited to the range of motion, load carrying capacity, stiffness, center of rotation orbit, and the like.

[0079] The first stage element 201 and the two second stage elements 203 are nested in series such that the two second stage elements 203 are positioned one on each side of the first stage element 201. In some embodiments, the first stage element 201 and the two second stage elements 203 are configured such that when the mechanism is in compression, all bending elements are in tension.

[0080] The third stage element 205 includes a shell 208 and is positioned around the outer periphery of the first stage element 201 and the two second stage elements 205. The shell 208 has a diameter approximately in the range of 0.5 cm to 15 cm.

[0081] In some embodiments, device 200 is configured to provide a greater range of motion than device 100. In some embodiments, device 200 provides at least one degree of freedom. In some embodiments, device 200 may be used in series with other mechanisms to add more degrees of freedom.

[0082] In some embodiments, the device 200 may be used in a knee joint. In some embodiments, the device 200 may be used in an elbow joint. In some embodiments, the device may be used to replace any joint in the body, including but not limited to fingers, thumbs, hands, wrists, shoulders, toes, feet, ankles / subtalar, hips, etc. In some embodiments, the device may be used to replace vertebrae in the back and neck.

[0083] In one exemplary embodiment, a coil spring 210 may be used in parallel with both device 100 and device 200 (FIG. 13). Coil spring 210 includes an outer edge 212 and an inner point 214. In some embodiments, outer edge 212 may be attached to first stage element 201 and inner point 214 may be attached to second stage element 203, thus inducing deformation of coil spring 210 to rotate the compliant joint. In some embodiments, this may also be accomplished using linear springs placed between the mechanism and each hard stop, where one spring is to induce the motion and a second spring is to store and return energy. In some embodiments, the second spring may have any shape known to one of skill in the art, including but not limited to a coil spring, multiple linear springs, cross axis pivots, etc. In some embodiments, the lateral edge 212 may be attached to the first articulation member 102 and the medial point 214 may be attached to the second articulation member 104 .

[0084] 14A-14D, additional exemplary compliant mechanism architectures are shown. In some embodiments, any compliant architecture may be used to replace a biological joint, including but not limited to cross-axis pivots (FIGS. 14A, 14C, 14D), suspended wire bends (FIGS. 14B), cross leaf springs (FIGS. 14A, 14C), and the like. Unlike other embodiments (FIGS. 14A, 14C, 14D) that achieve two skew-orthogonal rotational degrees of freedom (DOFs) by stacking two parallel joints in series, the suspended wire bend embodiment (FIG. 14B) achieves two desired DOFs by directly joining two rigid bodies together in a single parallel joint using multiple wire bends. The embodiment depicted in FIG. 14B includes four wire bends, where the axes of both rotational DOFs intersect with the axes of the four wire bends to achieve the desired skew-orthogonal rotation. A single rotational DOF can also be achieved with two or more blade flexures or leaf springs that lie in intersecting planes along the axis of rotation, as depicted in the lower portion of FIG. 14A labeled subtalar DOF and in the upper half of FIG. 14C to augment the rotational range of motion of the DOF labeled Ankle DOF. In some embodiments, at least one compliant mechanism may be used to replace a single joint. In some embodiments, a compliant mechanism having a different architecture may be used to replace a single joint. In some embodiments, the compliant mechanism may provide at least one degree of freedom.

[0085] 15A, an exemplary implant device 500 is shown. In some embodiments, the device 500 includes a first articular member 502, a second articular member 504 connected by at least one flexion element. In some embodiments, the first articular member 502 and the second articular member 504 may have any shape known to those skilled in the art. In some embodiments, the first articular member 502 and the second articular member 504 may have a circular or rounded outer geometry to allow the first articular member 502 and the second articular member 504 to rotate smoothly about a center of rotation. In some embodiments, the first articular member 502 has a larger diameter than the second articular member 504.

[0086] In some embodiments, the at least one bending element includes at least one element or blade, or a plurality of blades 514, where the element or blade has a thickness 538, a width 540, a length 542, and a distance to blade center 550. In some embodiments, the device 500 may be subjected to a tensile load 560 and a rotational load 570. In some embodiments, the plurality of blades 514 may have a length 542 in a range of about 0.3 cm to about 20 cm. In some embodiments, the plurality of blades 514 may have a width 540 in a range of about 0.1 cm to about 3 cm. In some embodiments, the plurality of blades 514 may have a thickness 538 up to about 0.3 cm. In some embodiments, the plurality of blades 514 may have a distance to blade center 550 in a range of 0.1 cm to 20 cm. In some embodiments, the plurality of blades 514 may be configured for a compressive load in a range of 1 to 10,000 N. In some embodiments, the plurality of blades 514 may be configured for a tensile load in a range of 1 to 10,000 N. In some embodiments, the plurality of blades 514 may be configured for rotational loads in the range of 1-10,000 N*m. In some embodiments, the plurality of blades 514 are disposed substantially parallel. In some embodiments, the plurality of blades 514 are disposed concentrically. In some embodiments, the plurality of blades 514 are disposed radially from a central axis. In some embodiments, the plurality of blades 514 are equidistant about the central axis.

[0087] 16 and 17A-17E, an exemplary implant device 600 of the present invention is shown inverted relative to the embodiment of FIG 15 A. Similar to device 500, device 600 includes a first articulation member 602, a second articulation member 604 and a plurality of blades 612 coupled to the first and second articulation members 602 and 604.

[0088] In some embodiments, the first articular member 602 and the second articular member 604 may have any desired shape as would be known to one of ordinary skill in the art. In some embodiments, the first articular member 602 and the second articular member 604 may have any desired thickness, for example, within the range of approximately 0.05-10 mm. In some embodiments, the first articular member 602 and the second articular member 604 may have any desired width or diameter, for example, within the range of approximately 0.5-20 cm, depending on the joint. In some embodiments, the width, thickness and diameter of the first articular member 602 and the second articular member 604 may be modified to change the overall behavior, including but not limited to the range of motion, load bearing capacity, stiffness, center of rotation trajectory, etc., depending on the type of joint being replaced. In some embodiments, the first articular member 602 and the second articular member 604 have a variable width, thickness and / or diameter along their length. In some embodiments, the first articular member 602 and the second articular member 604 have a uniform width, thickness and / or diameter along their length.

[0089] Similar to the embodiment of FIG. 15A, the plurality of blades 612 may have a length in the range of about 0.3 cm to about 20 cm. In some embodiments, the plurality of blades 612 may have a width in the range of about 0.1 cm to about 3 cm. In some embodiments, the plurality of blades 612 may have a thickness up to about 0.3 cm. In some embodiments, the plurality of blades 612 may have a distance to blade center in the range of 0.1 cm to 20 cm. In some embodiments, the plurality of blades 612 may be configured for a compressive load in the range of 1 to 10,000 N. In some embodiments, the plurality of blades 612 may be configured for a rotational load in the range of 1 to 10,000 N*m. In some embodiments, the plurality of blades 612 are substantially parallel. In some embodiments, the plurality of blades 612 are concentrically arranged. In some embodiments, the plurality of blades 612 are radially arranged from a central axis. In some embodiments, the plurality of blades 612 are equidistant about the central axis.

[0090] Additionally, the device 600 includes a central stem or post 619. The post 619 is fixed to or otherwise adjacent to the second articulation member 604. The first articulation member 602 has an opening and is ring-shaped, allowing the post 619 to extend through the opening in the first articulation member 602. Thus, the blades 612 are separate from the post 619. In one embodiment, the blades 612 are separated from the post 619 by a gap 617. In some embodiments, at least a portion of one or more of the blades may be in contact with the post 619. What is important is that the first articulation member 602 is not fixed to the post 619, and the first articulation member 602 can freely rotate about the post 619.

[0091] The device 600 may also include a housing or outer shell 616 that encloses the first and second articulation members and the plurality of blades. The housing 616 may also be coupled to or integral with a distal anchor 620. In some embodiments, the device 600 is constructed such that the distal anchor 620 and the outer shell 616 are formed as a single unit. In some embodiments, the distal anchor 620 may be separate from the housing or form a portion of the housing 616. In some embodiments, the outer shell 616 forms a proximal rim and a cup with a cavity therein for housing a compliant mechanism having at least one bending element.

[0092] In any of the embodiments described herein, the first and second articular members, the central post, the housing, the anchor component, and the blades may be made of any material known to one of skill in the art, including, but not limited to, pure metals, metal alloys, polymers, ceramics, metallic glasses, and any coatings, including porous coatings, or combinations thereof. In some embodiments, the first and second articular members, the central post, the housing, the anchor component, and the blades may comprise a biocompatible material. In some embodiments, the first and second articular members, the central post, the housing, the anchor component, and the blades may be coated in a biocompatible material. In some embodiments, the first and second articular members, the central post, the housing, the anchor component, and the blades may comprise Ti6-Al4v. In some embodiments, the flexion element may comprise Cr-Co. In some embodiments, the first and second articular members, the central post, the housing, the anchor component, and the blades may comprise SS316.

[0093] Referring again to FIG. 17A, an exploded side view of the implant device is shown. In some embodiments, the device 600 is arranged such that the distal anchor 620 and the outer shell 616 are formed as a single unit. In some embodiments, the outer shell 616 forms a cylindrical or cup shape with the proximal rim with a cavity for housing at least one compliant mechanism, such as the first and second articular members 602 and 604 and a plurality of blades 612. Thus, the at least one compliant mechanism includes the first articular member 602 having inner and outer surfaces with a peripheral rim and the second articular member 604 having at least one flexion element 612 and inner and outer surfaces, forming a single unit. In some embodiments, the device 600 includes shell set screw holes 634 disposed circumferentially around the proximal rim of the housing or outer shell 616. In some embodiments, the device 600 includes top plate set screw holes 636 disposed circumferentially on the peripheral rim of the first articular member 602. In some embodiments, the top plate set screw holes 636 have threads for engaging at least one set screw. In this example, at least one flexion element is inserted into the cup of the outer shell 616 and is fixedly attached to the proximal rim of the cup. To prevent migration, the housing is secured to the first articulation member 602 with set screws positioned in the shell set screw holes 634 and the top plate set screw holes 636. Similar to device 300 described herein, the flexion elements of device 600 are in tension when the device is in compression.

[0094] As previously described, the device 600 further includes a central opening in the first articular member such that the first articular member forms a ring, and a central post having a first end fixed to or adjacent to an inner surface of the second articular member and a second end extending through the opening in the first articular member such that the first articular member can rotate about the post.

[0095] In some embodiments, the device 600 further includes a housing 616 enclosing at least the first articulation member, the second articulation member, and the plurality of flexion elements, where the first articulation member is secured to the housing. In some embodiments, the device 600 further includes a first tissue anchor coupled to the second end of the central post and a second tissue anchor coupled to an outer surface of the second articulation member. In some embodiments, the device 600 further includes a first tissue anchor coupled to the second end of the central post and a second tissue anchor coupled to the housing.

[0096] In some embodiments, the housing further includes at least one recess and the second articulation member further includes at least one tab extending from an outer surface of the second articulation member and positioned within the at least one recess of the housing, where the at least one recess is sized to permit a limited range of movement of the at least one tab within the at least one recess when the second articulation member is rotated relative to the first articulation member.

[0097] In some embodiments, the outer shell 616 includes a plurality of slits 624 that allow for fluid communication between the interior and exterior of the outer shell 616. In some embodiments, the plurality of slits 624 are holes in the body of the outer shell 616. In some embodiments, the plurality of slits 624 may have a width in the range of about 0.1 mm to about 2 cm. In some embodiments, the plurality of slits 624 may have a height in the range of about 0.1 mm to about 15 cm. In some embodiments, the plurality of slits 624 may be any shape known to one of ordinary skill in the art.

[0098] In some embodiments, to further resist rotational motion, the housing 616 of the device 600 further includes a distal recess or slot 614 within the cup of the outer shell 616 for receiving the distal tab 640 once the implant device is assembled. In some embodiments, the distal slot 614 is a range-limiting feature that allows a constrained rotational path for the second articular member 604. For example, the tab 640 may be sized to fit within the slot 614 with limited movement. Then, when the second articular member 604 rotates within the housing 616, the tab 640 will also rotate within the slot 614 until it contacts the wall of the slot 614, limiting further rotational movement of the second articular member 604 at this point.

[0099] In some embodiments, the device 600 includes a proximal anchor 618 having a top surface and a distal anchor 620 having a bottom surface. In some embodiments, a proximal mounting hole 642 is formed on the top surface of the proximal anchor 618. In some embodiments, a distal mounting hole 644 is formed on the bottom surface of the distal anchor 620. These holes may be used to secure the device 600 to other components, for example, with a screw, bolt, friction fit, etc. In some embodiments, the device 600 may further include at least one hard stop or range limiting element. For example, the proximal anchor 618 may include a range limiting feature that contacts the first articular member 602 to prevent damage from any force other than a compressive force.

[0100] In some embodiments, the device 600 may be partially or completely inserted into the bone. In some embodiments, the device 600 is at least partially inserted into the bone such that at least a portion of the proximal anchor 618 protrudes from the bone.

[0101] In some embodiments, as shown in FIG. 18A, the at least one flexion element includes a first articulation member or top plate 606 and a second articulation member or bottom plate 610 with a peripheral rim and at least one flexion element 612. Similar to the embodiment of FIG. 17A, a central stem or post 622 is fixed to or adjacent to the bottom plate 610 and extends through an opening in the top plate 606. The flexion element 612 is coupled to the top plate 606 and bottom plate 610 and is separate from the post 622. The top plate 606 is not fixed to the post 622, and thus the top plate 606 may freely rotate about the post 622. Similar to the embodiment of FIG. 17A, the device 600 includes a housing or outer shell 616 and shell set screw holes 634 disposed circumferentially around a proximal rim of the outer shell 616. In some embodiments, the device 600 includes a top plate set screw hole 636 with threads disposed circumferentially on the peripheral rim of the top plate or first articular member 606. In this example, at least one flexion element is inserted into the cup of the outer shell 616 and fixedly attached to the proximal rim of the cup. To prevent migration, the compliant mechanism is set in place using set screws positioned in the top plate set screw hole 636 and shell set screw hole 634 to secure the housing 616 to the top plate 606.

[0102] In some embodiments, the at least one bending element 612 is positioned radially and equidistantly about a central axis passing through the first and second articulation members. In some embodiments, the first and second articulation members may rotate through at least one degree of motion. In some embodiments, the first and second articulation members may bend in the same plane.

[0103] Devices 300, 400, 500 and 600 represent implants that are formed with compliant stems that can be used for any orthopedic implant that has a stem (e.g. knee, hip, shoulder, elbow, wrist, ankle, etc.) Compliance allows for rotational movement without creating large shear stresses at the bone-implant interface.

[0104] 19A-19D, there is shown another exemplary implant device 400. The device 400 includes a proximal end 402, a distal end 404, a top plate 406, a central post, a bottom plate 410, a number of bending elements 412, and a number of blades 414.

[0105] Top plate 406 includes a top surface 407 and a bottom surface 409. Bottom surface 409 includes a plurality of ridges 411. In some embodiments, the plurality of ridges 411 may have any shape known to one of ordinary skill in the art. In some embodiments, the plurality of ridges 411 has a height in the range of about 0.1 cm to about 10 cm. In some embodiments, the plurality of ridges 411 has a width in the range of about 0.1 cm to about 3 cm. In some embodiments, the distance between two ridges 411 may be in the range of about 0.1 cm to about 3 cm.

[0106] Top plate 406 is coupled to a proximal anchor at a top surface 407 and is coupled to a plurality of blades 414 at a bottom surface 409 through a plurality of ridges 411. In some embodiments, top plate 406 may have any shape known to those of skill in the art, including but not limited to circular, oval, and the like. In some embodiments, top plate 406 may have any diameter ranging from approximately 0.5 cm to about 5 cm. In some embodiments, the proximal anchor is configured to attach device 400 to the surrounding bone via any method known to those of skill in the art, including but not limited to intramedullary fixation, extramedullary fixation, surface osseointegration, and the like.

[0107] At the distal end 404, a number of blades 414 are coupled to the bottom plate 410. In some embodiments, the number of blades 414 may have any shape known to one of ordinary skill in the art, including but not limited to rectangular, trapezoidal, and the like.

[0108] In some embodiments, the plurality of blades 414 may have a height in the range of about 0.3 cm to about 20 cm. In some embodiments, the plurality of blades 414 may have a width in the range of about 0.1 cm to about 3 cm. In some embodiments, the plurality of blades 414 may have a thickness of up to about 0.3 cm.

[0109] The central strut includes a strut body 413 and a number of protrusions 415 extending laterally from a proximal end 402 of the strut body 413. The number of protrusions 415 are coupled to a number of bending elements 412 at the proximal end 402. The number of protrusions 415 are positioned between two ridges 411, where the distance between the two ridges 411 is configured to define the degree of rotation of the number of bending elements 412 in each direction. In some embodiments, the number of bending elements 412 may have a freedom of movement of 1 to 90 degrees in each direction. In some embodiments, the strut body 413 may have any cross-sectional shape known to those of skill in the art, including, but not limited to, circular. In some embodiments, the strut body 413 may have a width in the range of about 0.5 cm to about 5 cm. In some embodiments, the strut body 413 may have a height in the range of about 1 cm to about 30 cm.

[0110] The central post rotates relative to the bottom plate 410 due to bending of the bending elements between the proximal end of the central post and the bottom plate 410. The bottom plate 410 simultaneously rotates relative to the top plate 406, which becomes secured to the bone via bending of the bending elements between the top and bottom plates. Note that in device 300, all bending elements are in tension when the device is in compression. In device 400, half of the bending elements are in tension while the other half are in compression.

[0111] A plurality of bending elements 412 are coupled to the plurality of ridges 412 at the proximal end 402 and to the bottom plate 410 at the distal end 404. In some embodiments, the plurality of bending elements 412 may be coupled to the strut body 413. In some embodiments, the bending elements 412 may have any shape known to one of ordinary skill in the art, including but not limited to rectangular, trapezoidal, and the like. In some embodiments, the bending elements 412 may have a height in the range of about 0.3 cm to about 20 cm. In some embodiments, the bending elements 412 may have a width in the range of about 0.1 cm to about 3 cm. In some embodiments, the bending elements 412 may have a thickness of up to about 0.3 cm. In some embodiments, the height of each bending element 412 may be less than each blade 414. In some embodiments, the height of each bending element 412 is similar to the height of each blade 414.

[0112] The plurality of bending elements 412 and the plurality of blades 414 are configured to provide rotational compliance as well as compression compliance in the proximal and distal directions.

[0113] In some embodiments, the top plate 406 may have a larger diameter than the bottom plate 410. In some embodiments, the top plate 406 may have the same diameter as the bottom plate 410. In some embodiments, the top plate 406 may have a smaller diameter than the bottom plate 410.

[0114] In some embodiments, the device 400 may further include an outer shell for protecting surrounding tissue. In some embodiments, the plurality of blades 414 may be coupled to the outer shell. In some embodiments, the outer shell may be made of any material known to those skilled in the art, including, but not limited to, pure metals, metal alloys, polymers, ceramics, metallic glasses, or combinations thereof. In some embodiments, the outer shell may be made of a biocompatible material. In some embodiments, the outer shell may be coated in a biocompatible material. In some embodiments, the outer shell may include Ti6-Al4v. In some embodiments, the outer shell may include Cr-Co. In some embodiments, the outer shell may include SS316.

[0115] In some embodiments, the outer shell can be coupled to a distal anchor at a distal end 404. In some embodiments, the distal anchor is configured to attach the device 400 to the surrounding bone via any method known to those of skill in the art, including, but not limited to, intramedullary fixation, extramedullary fixation, surface osseointegration, bone cement fixation, and the like.

[0116] 19E-19H, another exemplary implant device is shown. The device 300 includes a proximal end 302, a distal end 304, a top plate 306, a central post, a bottom ring 310, a number of bending elements 312, a number of blades 314, and an outer shell 316.

[0117] The top plate 306 includes an opening 318 located at the center of the top plate 306. In some embodiments, the top plate 306 may have any shape known to those of skill in the art, including, but not limited to, circular, oval, and the like. In some embodiments, the top plate 306 may have any diameter within a range of approximately 0.5 cm to 5 cm. In some embodiments, the opening 318 may have any shape known to those of skill in the art, including, but not limited to, circular, oval, and the like. The top plate 306 is coupled to a proximal anchor at a proximal end 302 and to a plurality of bending elements 312 at a distal end 304. In some embodiments, the proximal anchor is configured to attach the device 300 to the surrounding bone via any method known to those of skill in the art, including, but not limited to, intramedullary fixation, extramedullary fixation, surface osseointegration, and the like.

[0118] The central post is positioned within the opening 318 and includes a top plate 306, a central shaft 322, and a plurality of bending elements 312. The central shaft 322 is coupled to the top plate 306 at a proximal end 302 and extends distally from the top plate 306 toward the bottom ring 310 without contacting the bottom ring 310. In some embodiments, the central shaft 322 may have any cross-sectional shape known to those of skill in the art, including, but not limited to, circular. In some embodiments, the central shaft 322 may have a diameter in the range of about 0.2 cm to about 4 cm. In some embodiments, the central shaft 322 may have a height in the range of about 0.3 cm to about 20 cm.

[0119] The plurality of flexure elements 312 are coupled to the top plate 306 at a proximal end 302 and to the bottom ring 310 at a distal end 304. In some embodiments, the plurality of flexure elements 312 may have any shape known to one of ordinary skill in the art, including, but not limited to, a rectangle.

[0120] The flexion elements 312 are coupled to the top plate 306 at a proximal end 302 and to the bottom ring 310 at a distal end 304. In some embodiments, the flexion elements 312 may have any shape known to one of ordinary skill in the art, including but not limited to rectangular, trapezoidal, and the like. In some embodiments, the flexion elements 312 may have a height in the range of about 0.3 cm to about 20 cm. In some embodiments, the flexion elements 312 may have a width in the range of about 0.1 cm to about 3 cm. In some embodiments, the flexion elements 312 may have a thickness of up to about 0.3 cm.

[0121] In some embodiments, the top plate 306 may have a larger diameter than the bottom ring 310. In some embodiments, the top plate 306 may have the same diameter as the bottom ring 310. In some embodiments, the top plate 306 may have a smaller diameter than the bottom ring 310.

[0122] In some embodiments, the bending elements 314 may have any shape known to one of ordinary skill in the art, including, but not limited to, rectangular, trapezoidal, and the like. In some embodiments, the bending elements 314 may have a height in the range of about 0.3 cm to about 20 cm. In some embodiments, the bending elements 314 may have a width in the range of about 0.1 cm to about 3 cm. In some embodiments, the bending elements 314 may have a thickness of up to about 0.3 cm. In some embodiments, the height of each blade 314 may be less than each bending element 312.

[0123] The blades 314 are positioned between the two flexure elements 312 and are configured to limit the degree of rotation in each direction of the flexure elements 312. In some embodiments, the flexure elements 312 may have a freedom of movement of between 1 and 90 degrees in each direction.

[0124] The plurality of bending elements 312 and the plurality of blades 314 are configured to provide rotational compliance as well as compression compliance in the proximal and distal directions.

[0125] The outer shell 316 is configured to protect surrounding tissue and at least partially encase the plurality of bending elements 312. In some embodiments, the outer shell 316 may be made of any material known to one of ordinary skill in the art, including, but not limited to, pure metals, metal alloys, polymers, ceramics, metallic glasses, or combinations thereof. In some embodiments, the outer shell 316 may be made of a biocompatible material. In some embodiments, the outer shell 316 may be coated in a biocompatible material. In some embodiments, the outer shell 316 may include Ti6-Al4v. In some embodiments, the outer shell 316 may include Cr-Co. In some embodiments, the outer shell 316 may include SS316.

[0126] The outer shell 316 may be coupled at the distal end 304 to a distal anchor 320. The distal anchor 320 is configured to attach the device 300 to the surrounding bone via any method known to those of skill in the art, including, but not limited to, intramedullary fixation, extramedullary fixation, surface osseointegration, and the like.

[0127] 20A-20H, an exemplary two degree of freedom implant device 700 of the present invention is shown. In some embodiments, at least one implant device of the present invention is attached in series to allow at least one degree of freedom of movement. In one example, a first implant device allows a first degree of freedom of movement and a second implant device allows a second degree of freedom of movement. In the example of FIGS. 20A-20H, an implant device 100 of the present invention is fixedly attached in series to an implant device 600 of the present invention to allow two degrees of freedom.

[0128] 22A-22G, an exemplary three degree of freedom implant device 800 of the present invention is shown. In some embodiments, at least one implant device of the present invention is mounted in series to allow for at least one degree of freedom of movement. In this example, a first implant device allows for a first degree of freedom of movement, a second implant device allows for a second degree of freedom of movement, and a third implant device allows for a third degree of freedom of movement. In some embodiments, device 800 includes a first compliant device 800a, a second compliant device 800b, and a third compliant device 800c.

[0129] In some embodiments, the device 800 includes a first articular member 802, a second articular member 804, a third articular member 824, a fourth articular member 826, a fifth articular member 828, a sixth articular member 830, at least one flexion element (e.g., the first flexion element 806 and the second flexion element 808), a proximal anchor 818, and a distal anchor 820. In some embodiments, the first articular member 802, the second articular member 804, the third articular member 824, the fourth articular member 826, the fifth articular member 828, and the sixth articular member 830 may have any shape known to one of skill in the art.

[0130] 22B, in some embodiments, the first compliant device 800a includes a first articulation member 802 having a bridge member 802a with a first arm 802b and a second arm 802c extending from either end of the bridge member. In some embodiments, the third compliant device 800c includes a sixth articulation member 830 having a bridge member 830a with a first arm 830b and a second arm 830c extending from either end of the bridge member. The first and second arms extending from either end of each bridge member are connection points for at least one bending element. In some embodiments, the second compliant device 800b includes a third articulation member 824 and a fourth articulation member 826, each having a bridge member (824A and 826A, respectively). In some embodiments, the first articular member 802 has a top end region for connecting to the proximal anchor 818 and a bottom end region for connecting to at least one bending element. In some embodiments, the sixth articular member 830 has a bottom end region for connecting to the distal anchor 820 and a top end region for connecting to at least one bending element.

[0131] In some embodiments, the at least one flexure element may have any number of applicable flexure elements known to those of ordinary skill in the art. In some embodiments, the at least one flexible structure includes a first flexure element 806, a second flexure element 806.

[0132] In some embodiments, the implant device includes a third articular member 824 having an inner surface and an outer surface; a fourth articular member 826 having an inner surface and an outer surface; a fifth articular member 828 having an inner surface and an outer surface; a sixth articular member 830 having an inner surface and an outer surface; at least one bending element having a first and second end, the first end being coupled to the inner surface of the third articular member 824 and the second end being coupled to the inner surface of the fourth articular member 826; at least one bending element having a first and second end, the first end being coupled to the inner surface of the fifth articular member 828 and the second end being coupled to the inner surface of the sixth articular member 830. an inner surface of the second joint member 804 coupled to an outer surface of the third joint member 824, an outer surface of the fourth joint member 826 coupled to an inner surface of the fifth joint member 826, the third joint member 824 and the fourth joint member 826 configured to move relative to each other in a second degree of freedom different from the first degree of movement freedom between the first joint member 802 and the second joint member 804; and the fifth joint member 828 and the sixth joint member 830 configured to move relative to each other in a third degree of freedom different from the second degree of movement freedom between the third joint member 824 and the fourth joint member 826.

[0133] In some embodiments, the first degree of freedom is a translational degree of freedom, the second degree of freedom is a rotational degree of freedom, and the third degree of freedom is a translational degree of freedom. In some embodiments, the first degree of freedom is a rotational degree of freedom, the second degree of freedom is a translational degree of freedom, and the third degree of freedom is a rotational degree of freedom. In some embodiments, the first, second, and third degrees of freedom are each translational degrees of freedom. In some embodiments, the first, second, and third degrees of freedom are each rotational degrees of freedom.

[0134] In some embodiments, the device further includes a first tissue anchor (proximal anchor 818) extending from an outer surface of the first articular member 802, and a second tissue anchor (distal anchor 820) extending from an outer surface of the sixth articular member 830. In some embodiments, the first and second tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

[0135] The first articular member 802 and the fourth articular member 808 have the same structure in an inverted, orthogonal orientation, with the second articular member 804 and the third articular member 806 disposed between the first articular member 802 and the fourth articular member 808.

[0136] In some embodiments, the first bending element 810 and the second bending element 812 function as springs and can cross each other independently to provide at least one axis of rotation for the articulation member 802, the second articulation member 804, the third articulation member 806 and the fourth articulation member 808.

[0137] In some embodiments, the first flexure element 810 and the second flexure element 812 may intersect at any point along their length. In some embodiments, the center of rotation may be approximated by the intersection point, but moves as the flexure elements deform. In some embodiments, the flexure elements may have different lengths and may be oriented at any angle, where varying these properties affects the mechanical behavior of the mechanism. In some embodiments, the flexure elements may be oriented such that the first flexure element 810 and the second flexure element 812 form a crossing pattern. In some embodiments, the flexure elements may be oriented such that the first flexure element 910 and the second flexure element 812 are substantially parallel.

[0138] The proximal anchor 818 is configured to attach at one end to the first articular member 802 and at the opposite end to attach the device 800 to a bone. The distal anchor 820 is configured to attach at one end to the fourth articular member 808 and at the opposite end to attach the device 800 to a bone.

[0139] In some embodiments, the device 800 may be anchored to the surrounding bone through the proximal anchor 818 and the distal anchor 820 via any method known to those skilled in the art, including but not limited to intramedullary fixation, extramedullary fixation, surface osseointegration, and the like. In some embodiments, the device 800 may be anchored to the surrounding bone through the proximal anchor 818 and the distal anchor 820 by intramedullary fixation. In some embodiments, the device may be anchored to the surrounding bone using any of a number of strategies for intramedullary fixation, such as long stems, short stems, threaded intramedullary screws, press-fit or cemented stems, nails, threaded or threaded implants, compression type implants, porous coated implants for bone ingrowth, and the like. In some embodiments, intraosseous rods or pins may be used for fixation to cancellous bone.

[0140] In some embodiments, the device 800 may be secured to the surrounding bone through the proximal anchor 818 and the distal anchor 820 by extramedullary fixation. In some embodiments, the device may be secured to the surrounding bone using any of a number of strategies for intramedullary fixation, including but not limited to plates and screws. In some embodiments, conventional orthopedic hardware may be used for extraosseous fixation, including but not limited to customized plates and screws, standardized plates and screws, etc. In some embodiments, the device 800 may be secured to the surrounding bone by ingrowth on a porous surface. In some embodiments, the bone surface may be pre-treated intraoperatively for ingrowth onto the porous surface (e.g., a porous coating for bone ingrowth as in an acetabular cup for a total hip replacement). In some embodiments, initial stability may be aided by combination with any other fixation tactics.

[0141] In some embodiments, the proximal anchor 818 and the distal anchor 820 may have any shape / geometry known to one of skill in the art, including but not limited to cylindrical, cubical, and the like.

[0142] In some embodiments, the proximal anchor 818 and the distal anchor 820 may be made of any material, including, but not limited to, titanium, Ti6-Al4v, Cr-Co, SS316. In some embodiments, the proximal anchor 818 and the distal anchor 820 may be porous. In some embodiments, the proximal anchor 818 and the distal anchor 820 may be further coated with any material known to one of skill in the art, including, but not limited to, pure metals, metal alloys, polymers, ceramics, metallic glasses, or combinations thereof. In some embodiments, the proximal anchor 818 and the distal anchor 820 may include titanium. In some embodiments, the proximal anchor 818 and the distal anchor 820 may include a biocompatible material.

[0143] In some embodiments, the device 800 may be used for common orthopedic procedures including, but not limited to, total hip replacement, total knee replacement, total shoulder replacement, etc. In some embodiments, the joint (e.g., foot) may be surgically altered to facilitate fixation. In one exemplary embodiment, the joint may be fused to eliminate movement that may be detrimental to bone ingrowth and osseointegration. In some embodiments, bones may be fused together to create a larger bone surface onto which an implant could be fixed. In some embodiments, bone may be removed or repositioned to create more space for the implant.

[0144] 23A-23J depict an exemplary implant device 900 of the present invention for an animal model. In some embodiments, device 900 includes a tibial stem 980, a stem adapter 982, a flexion element 984, a metatarsal stem 986, an implant cover 988, and a Morse taper 990. Tibial stem 980 and metatarsal stem 986 are fixedly attached to flexion element 984 by any method known to one of skill in the art.

[0145] In some embodiments, devices 100-900 may be implemented in parallel with an external exoskeleton to provide power or additional passive assistance to the subject (FIG. 24). In some embodiments, the external exoskeleton may interface unidirectionally with the subject's nervous system. In some embodiments, the external exoskeleton may interface bidirectionally with the subject's nervous system. In some embodiments, the configuration includes fully sensory biological limbs. In some embodiments, the configuration includes neurally controlled mechanical joints. In some embodiments, the configuration includes a closed skin envelope that is robust to infection. In some embodiments, the configuration includes external mechatronics that are accessible for repair or upgrade.

[0146] In some embodiments, devices 100-900 may be used in tandem with a separate spring / compliant mechanism, including but not limited to a coil spring, a second compliant mechanism, etc., to increase the energy storage capacity of the joint. In some embodiments, it is contemplated that this may be a fixed component integrated within the compliant mechanism, or may be a modular component that is interchangeable depending on the specifics of the patient's anatomy or pathology.

[0147] In some embodiments, the devices 100-900 may be used in rehabilitation applications. In some embodiments, the devices 100-900 may be used in prevention / augmentation applications. In some embodiments, the devices 100-900 may be used to treat subjects with diagnosed pathologies. In some embodiments, the devices 100-900 may be used for subjects seeking prophylactic injury prevention. In some embodiments, the devices 100-900 may be used to enhance a subject's athletic performance beyond their baseline capabilities.

[0148] In some embodiments, devices 100-900 may be used in tandem with existing joints to manipulate the mechanical properties of the existing joint and store and return energy. In one exemplary embodiment, devices 100-900 may be implanted in tandem with a joint in a subject with a weak joint to stiffen the joint and allow for improved function.

[0149] In some embodiments, devices 100-900 may be manufactured using traditional subtractive manufacturing without any assembly, traditional subtractive manufacturing with assembly, additive manufacturing, and combinations thereof. In some embodiments, traditional subtractive manufacturing may be used. In some embodiments, devices 100-900 may be manufactured as a single part using traditional subtractive manufacturing. In some embodiments, both devices may be manufactured using traditional subtractive manufacturing without any assembly. In some embodiments, both devices may be manufactured using traditional subtractive manufacturing with assembly. In some embodiments, both devices may be manufactured in at least two distinct parts. In some embodiments, the at least two distinct parts may be assembled prior to sterilization and implantation. In some embodiments, the joint between the at least two distinct parts may be secured using any method known to one of skill in the art, including but not limited to welding, bolting, adhesives, interference fits, thermally modulated interference fits, and the like. In some embodiments, the individual components of each of the at least two distinct parts may be assembled at low temperature, and when exposed to body heat, the parts may expand until they reach an interference fit. In some embodiments, the device may be manufactured using additive manufacturing techniques, including but not limited to 3D printing. In some embodiments, both devices may be 3D printed as a single part. In some embodiments, both devices may be 3D printed as at least two parts that can be assembled.

[0150] In some embodiments, a potential option for manufacturing is to precision machine the bent blades as shims from bulk material. These shim blades could then be inserted into a housing that is conventionally machined, 3d printed, injection molded or investment cast. The shims could be attached to the housing via a press fit, thermal expansion fit, welds, bolts or any combination of these options.

[0151] Alternatively, in another embodiment, the shim blade could be fitted into the implant mold to be used for investment casting the housing. This would allow for a bulk weld between the shim blade and the housing, eliminating the need for molten material to flow into the small blade profile. It is believed that all or a portion of the shim blade could be actively or passively cooled to keep the blade unaffected by the molten housing material.

[0152] Methods of the Invention The present invention provides methods for facilitating the design of orthopedic implants with compliant mechanisms for limb repair. In some embodiments, the methods of the present invention are configured to integrate biomechanical, analytical, and finite element modeling to generate optimized geometry and placement of bending elements within a compliant mechanism (from a predefined target biomechanical set). In some embodiments, the methods of the present invention may be used to design compliant implantable prostheses for all joints of the body. In some embodiments, the methods of the present invention may be used to correct various pathologies including, but not limited to, arthritis, trauma, tumors, congenital deformities, infections, diabetic arthropathy, and the like. In some embodiments, the methods of the present invention may result in joint- and pathology-specific compliant implants optimized to restore limb biomechanics.

[0153] 25, an exemplary method 1000 for designing a compliant implantable prosthesis is depicted. The method 1000 begins at step 1002, where neuromuscular (NMS) modeling or any biomechanical modeling is performed on a subject to identify desired degree of freedom compliances and anatomical constraints for the implant.

[0154] In step 1004, freedom and constraint topology (FACT) is used to generate a rough approximation of the mechanism geometry required to create the desired compliance space. In some embodiments, FACT can be used to organize an overall compliant system of any geometry. In some embodiments, FACT links these small movements, including but not limited to degrees of freedom or "DOFs," to a full design space of compliant solutions that achieve infinitesimal movements. In some embodiments, FACT is configured to open the door for rapid identification of application-specific compliant geometries. In some embodiments, FACT may be combined with recent computational advances to enable optimization of these geometries. In some embodiments, FACT may be configured to enable the design of compliant mechanisms with prescribed mechanical behavior.

[0155] In step 1006, a parameterized finite element model (FEM) of the generic mechanism is generated from the quasi-static mechanical model of the implant under loads representative of those encountered during gait. In some embodiments, the model is constructed based on the geometry and materials of the mechanism. In some embodiments, the model outputs deformations, stresses, stiffness, etc. in response to simulated applied loads.

[0156] In step 1008, the mechanism geometry is refined by adjusting the shape of the implant. In some embodiments, the shape of the implant may be adjusted based on its mechanics and fatigue life.

[0157] In some aspects, the invention relates to a method for designing a compliant implantable prosthesis, comprising: performing neuromuscular-skeletal (NMS) modeling of a subject to identify anatomical constraints and compliance of desired degrees of freedom for an implant; generating a rough approximation of the mechanism geometry required to create the desired compliance space by using free and constraint topology (FACT); creating a parameterized finite element model (FEM) of a generic mechanism from a quasi-static mechanical model of the implant under loads representative of those encountered during walking; and refining the mechanism geometry by adjusting the shape of the implant.

[0158] In some embodiments, the present invention relates to a drill guide for implantation of at least one implant device of the present invention. Referring now to Figures 26A and 26B, exemplary drill guides for implantation of at least one implant device of the present invention are shown. Shown in Figure 26A is a calcaneal drill guide. Shown in Figure 26B is a midfoot drill guide. Note that the blue and red lines represent k-wires that are placed in place to hold the guide in place and guide the drill. EXAMPLES

[0159] The present invention will be further described with reference to the following experimental examples. These examples are provided for illustrative purposes only and are not intended to be limiting unless otherwise specified. Therefore, the present invention should not be considered as being limited to the following examples, but rather as embracing any variations that become evident as a result of the teachings provided herein.

[0160] Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the following illustrative examples, make and utilize the present compositions and practice the claimed methods. As such, the following examples specifically point out illustrative embodiments of the present invention, and are not to be construed as limiting in any way the remainder of the disclosure.

[0161] Example 1: Preliminary modeling and experimental work was performed to demonstrate the feasibility of compliant implant designs for the treatment of severe ankle and hindfoot pathologies. This pilot work demonstrates that i) implantable compliant mechanisms of appropriate size and constrained space for the ankle can withstand cyclic walking loads; ii) the behavior of these mechanisms can be predictably adjusted with minor modifications to the flexion geometry; and iii) the target site has adequate bone for robust fixation. The generic ankle mechanism design (Figure 27A) has high compliance about one axis and adjustable compliance in off-axis rotation and vertical compression. The design also includes a cover for the mechanism, which is important to prevent dead space and impingement within the prosthesis space. Preliminary finite element modeling (FEM) demonstrated that the titanium (Ti6-Al4v) mechanism design can be used for 10 8 This corresponds to a modest 5000 steps per day for 91 years before failing due to fatigue. Two prototype mechanisms of identical size, but with distinctly different bending geometries (Fig. 27C), were also 3D printed to demonstrate that FEM can accurately predict their radically different stiffness (Fig. 27D, E).

[0162] The intention is to remove the damaged talus and anchor the distal end of the ankle-hindfoot implant directly to the calcaneus, navicular, and cuneiform bones; although these bones are often used in fusion or other reconstructive approaches, novel hardware is required for this specific fixation approach. To this end, several incisions were made to assess these bones as potential fixation sites (Figure 27F and Figure 28) and to design a fixation strategy utilizing porous titanium to promote osseointegration with the target bones.

[0163] The disclosures of each and every patent, patent application and publication cited herein are each incorporated herein by reference in their entirety. Although the present invention has been disclosed with reference to specific embodiments, it is apparent that other embodiments and variations of the present invention may be devised by those skilled in the art without departing from the true spirit and scope of the present invention. It is intended that the appended claims be construed to include all such embodiments and equivalent variations.

Claims

1. a first articulation member having an inner surface and an outer surface; a second articulation member having an inner surface and an outer surface; at least one flexion element having first and second ends, the first end connected to the inner surface of the first articulation member and the second end connected to the inner surface of the second articulation member; 1. An orthopedic device comprising: An orthopedic device, wherein the first and second articulation members are configured to move relative to one another within a first degree of freedom.

2. The orthopedic device of claim 1 , wherein the at least one bending element includes at least a first bending element and a second bending element.

3. The orthopedic device of claim 1 , wherein the at least one bending element includes at least a first bending element, a second bending element, and a third bending element.

4. the first and third bending elements are oriented at the same angle relative to one another between the inner surfaces of the first and second articulation members; The orthopedic device of claim 3 .

5. 5. The orthopedic device of claim 4, wherein the second bending element is positioned between the first and third bending elements, and the second bending element is oriented at a different angle relative to the first and third bending elements between the inner surfaces of the first and second articulation members.

6. the first articulation member including a top region, a bottom region, and a central region between the top region and the bottom region along its length; the second articulation member including a top region, a bottom region, and a central region between the top region and the bottom region along its length; the first bending element is connected at a first end to the inner surface of the bottom region of the first articulation member and at a second end to the inner surface of the top region of the second articulation member; the second bending element is connected at a first end to the inner surface of the central region of the first articulation member and at a second end to the inner surface of the central region of the second articulation member; and the third bending element is connected at a first end to the inner surface of the bottom region of the first articulation member and at a second end to the inner surface of the top region of the second articulation member; The orthopedic device of claim 5.

7. The orthopedic device of claim 6 , further comprising a first tissue anchor extending from the outer surface of the first articular member and a second tissue anchor extending from the outer surface of the second articular member.

8. 8. The orthopedic device of claim 7, wherein the first and second tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

9. The orthopedic device of claim 6 , wherein the first and second articulation members each have a curvature along their length including the top, middle and bottom regions.

10. 10. The orthopedic device of claim 9, wherein the first and second articular members are oriented relative to one another such that the top region of the second articular member overlaps the bottom region of the first articular member.

11. the at least one flexure element is configured to deform when the first articulation member moves relative to the second articulation member within the first degree of freedom.

11. An orthopedic device according to any one of claims 1 to 10.

12. The orthopedic device of any one of claims 1 to 11, wherein the first degree of freedom is a translational degree of freedom.

13. The orthopedic device of claim 1 , wherein the at least one bending element comprises a plurality of bending elements.

14. The orthopedic device of claim 13 , wherein the plurality of bending elements are oriented at the same angle relative to one another between the inner surfaces of the first and second articulation members.

15. The orthopedic device of claim 14 , wherein the plurality of bending elements are positioned equidistant radially about a central axis passing through the first and second articulation members.

16. a central opening in the first articulation member such that the first articulation member forms a ring; a central post having a first end fixed to or adjacent to an inner surface of a second articulation member and a second end extending through the opening in the first articulation member such that the first articulation member can rotate about the post; 16. The orthopedic device of claim 15, further comprising:

17. The orthopedic device of claim 16, further comprising a housing enclosing at least the first articulation member, the second articulation member, and the plurality of flexion elements, the first articulation member being secured to the housing.

18. The orthopedic device of claim 16, further comprising a first tissue anchor coupled to the second end of the central strut and a second tissue anchor coupled to the outer surface of the second articulation member.

19. The orthopedic device of claim 17 , further comprising a first tissue anchor coupled to the second end of the central post and a second tissue anchor coupled to the housing.

20. the housing further comprising at least one recess; the second articulation member further includes at least one tab extending from the outer surface of the second articulation member and positioned within the at least one recess in the housing; the at least one recess is sized to allow a limited range of movement of the at least one tab within the at least one recess when the second articulation member is rotated relative to the first articulation member.

18. The orthopedic device of claim 17.

21. 21. The orthopedic device of any one of claims 13 to 20, wherein the plurality of bending elements are configured to deform when the first articulation member moves within the first degree of freedom relative to the second articulation member.

22. The orthopedic device of any one of claims 13 to 21, wherein the first degree of freedom is a rotational degree of freedom.

23. 23. The orthopedic device of any one of claims 1 to 22, further comprising at least one range-limiting element configured to limit movement of the first articulation member relative to the second articulation member to the first degree of freedom.

24. 23. The orthopedic device of any one of claims 1 to 22, further comprising at least one range-limiting element configured to limit movement of the second articulation member relative to the first articulation member within the first degree of freedom.

25. 23. The orthopedic device of any one of claims 1 to 22, further comprising at least one spring coupled to the first and second articulation members, the spring configured to deform when the first and second articulation members move relative to one another.

26. 26. The orthopedic device of claim 25, wherein the at least one spring includes a first spring and a second spring, the first spring configured to provide a restoring torque to the orthopedic device and the second spring configured to store and return energy to the orthopedic device.

27. a third articulation member having an inner surface and an outer surface; a fourth articulation member having an inner surface and an outer surface; at least one flexion element having first and second ends, the first end connected to the inner surface of the third articulation member and the second end connected to the inner surface of the fourth articulation member; further comprising the third and fourth articulation members are configured to move relative to one another within a second degree of freedom that is different from the first degree of freedom of movement between the first and second articulation members; and the outer surface of the third articulation member is connected to the outer surface of the second articulation member; The orthopedic device of claim 1 .

28. The orthopedic device of claim 27 , wherein the first and second degrees of freedom are each translational degrees of freedom.

29. The orthopedic device of claim 27, wherein the first degree of freedom is a translational degree of freedom and the second degree of freedom is a rotational degree of freedom.

30. The orthopedic device of claim 27 , wherein the first and second degrees of freedom are each rotational degrees of freedom.

31. 31. The orthopedic device of any one of claims 27 to 30, further comprising a first tissue anchor coupled to the outer surface of the first articular member and a second tissue anchor coupled to the outer surface of the fourth articular member.

32. 32. The orthopedic device of claim 31 , wherein the first and second tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

33. a third articulation member having an inner surface and an outer surface; a fourth articulation member having an inner surface and an outer surface; a fifth articulation member having an inner surface and an outer surface; a sixth articulation member having an inner surface and an outer surface; at least one flexion element having first and second ends, the first end connected to the inner surface of the third articulation member and the second end connected to the inner surface of the fourth articulation member; at least one flexion element having first and second ends, the first end coupled to the inner surface of the fifth articulation member and the second end coupled to the inner surface of the sixth articulation member; further comprising the inner surface of the second articulation member is connected to the outer surface of the third articulation member; the outer surface of the fourth articulation member is connected to the inner surface of the fifth articulation member; the third and fourth articulation members are configured to move relative to one another within a second degree of freedom that is different from the first degree of freedom of movement between the first and second articulation members; and the fifth and sixth articulation members are configured to move relative to one another in a third degree of freedom that is different from the second degree of freedom of movement between the third and fourth articulation members. The orthopedic device of claim 1 .

34. The orthopedic device of claim 33, wherein the first degree of freedom is a translational degree of freedom, the second degree of freedom is a rotational degree of freedom, and the third degree of freedom is a translational degree of freedom.

35. The orthopedic device of claim 33, wherein the first degree of freedom is a rotational degree of freedom, the second degree of freedom is a translational degree of freedom, and the third degree of freedom is a rotational degree of freedom.

36. The orthopedic device of claim 33, wherein the first, second, and third degrees of freedom are each translational degrees of freedom.

37. The orthopedic device of claim 33, wherein the first, second, and third degrees of freedom are each rotational degrees of freedom.

38. The orthopedic device of claim 33, further comprising a first tissue anchor extending from the outer surface of the first articular member and a second tissue anchor extending from the outer surface of the sixth articular member.

39. 39. The orthopedic device of claim 38, wherein the first and second tissue anchors are each configured to engage bone via at least one selected from the group consisting of intramedullary fixation, extramedullary fixation, osseointegration, and combinations thereof.

40. In a method for designing a compliant implantable prosthesis: performing neuromuscular-skeletal (NMS) modeling of the subject to identify compliance with anatomical constraints and desired degrees of freedom for the implant; generating a rough approximation of the mechanism geometry required to create the desired compliance space by using free and constraint topology (FACT); creating a parameterized finite element model (FEM) of the generic mechanism from a quasi-static mechanical model of the implant under loads representative of those encountered during gait; - refining mechanism geometry by adjusting the shape of the implant; A method comprising:

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