Expanding tibial stem

Abstract

An ankle prosthesis is provided that includes a tibial stem with a retractable member configured to be controllably movable between a retracted position and an extended position so that in the extended position the retractable member engages the surface of the bone that defines an intramedullary canal so as to enhance anchoring of the tibial stem within the tibia.

Description

FIELD OF THE INVENTION

The invention is related to total ankle replacement surgical procedures and devices.

BACKGROUND OF THE INVENTION

Tibia stem components help fixate implants where limited bone is available for total ankle arthroplasty. “Pistoning” or loosening of the implant often presents a long-term complication. Bone in-growth into certain implant designs can inhibit establishment of replacement prostheses. Thus, improved tibial stem components that can better engage with the tibia bone, improve immediate implant stability, reduce implant migration over time, and be more easily replaced are desired.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of the invention provide an implant that engages cancellous, and possibly cortical, tibia bone to improve immediate implant stability and reduce implant migration long term. Retractable members are movable from a withdrawn position to extend outward and retractable to be fully captured within the device.

According to one embodiment of the invention, an ankle prosthesis incorporates a tibial stem including a leading end, a trailing end, and a longitudinal axis defined therethrough. A tibia tray is provided and configured to be attached to a prosthetic joint articulating surface, where the tibia tray extends from the trailing end and is sized and configured to be placed in a resected tibia or, in some embodiments, a resected joint. The tibial stem is configured to be placed in an intramedullary canal defined in a tibia, and includes a retractable member configured to be controllably movable between (i) a retracted position and (ii) an outwardly, longitudinally extended position to a deployed position. In the retracted position, the retractable member is contained substantially within the tibial stem and does not extend outwardly. The retractable member is able to engage the bone that defines the intramedullary canal within the tibia thereby to enhance anchoring of the tibial stem within the intramedullary canal when the tibial stem is located in the intramedullary canal and the retractable member is in the deployed position. Often, the retractable member is configured to be moved back to the retracted position from the deployed position. Additionally, the tibia tray often includes a channel extending between a pair of opposed rails to receive a prosthetic joint surface. In some embodiments, the channel extends in at least one of an anterior-posterior direction, a medial-lateral direction, and in an oblique direction. In other embodiments, the tibial stem may include an elongated, generally cylindrical shell that defines an internal cavity that is open at the trailing end. In many embodiments, there is formed an opening in the cylindrical shell through which the retractable member may move between the retracted position and the deployed position.

In another embodiment of the invention, the tibial stem further includes a rotational actuator, located within the internal cavity, that is configured to rotate within the internal cavity around a longitudinal axis. The retractable member may include an engagement end, teeth, and a tail end. The engagement end is often a free end that is movable through the opening provided in the cylindrical shell of the tibial stem so as to engage the internal surface of the tibia that defines the intramedullary canal. Here, the retractable member may be located between (i) a retracted position and (ii) a deployed position, by rotating the rotational actuator within the internal cavity. Often, the rotational actuator includes a tool interface to receive a tool used to rotate the rotational actuator, where the tool interface may be accessed in a channel of the tibia tray that extends between a pair of opposed rails that arranged so as to receive the prosthetic joint surface. Also, the rotational actuator may include a gear portion that meshes with the teeth of the retractable member so that by rotating the rotational actuator the gear portion rotates and moves the retractable member. The prosthesis of the invention often further includes a coating or surface modification on the tibial stem and/or the tibia tray to promote bony in-growth.

The above and other features, elements, characteristics, steps, and advantages of the invention will become more apparent from the following detailed description of preferred embodiments of the invention with reference to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

The features of the embodiments described herein will be more fully disclosed in the following detailed description, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts.

FIGS. 1 and 2 are illustrations of a prosthesis formed in accordance to one embodiment of the invention.

FIG. 3 is a cross section view of the prosthesis formed in accordance to one embodiment of the invention.

FIGS. 4 and 5 are illustrations of the prosthesis with deployed retractable members formed in accordance to one embodiment of the invention.

FIG. 6 is a top view of the actuation assembly of the prosthesis formed in accordance to one embodiment of the invention.

FIG. 7-9 are illustrations of another prosthesis formed in accordance to one embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The description of the preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In this description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top,” “bottom,” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both moveable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively coupled” is such an attachment, coupling, or connection that allows the pertinent structures to operate as intended by virtue of that relationship.

As used herein, the term “substantially” denotes elements having a recited relationship (e.g., parallel, perpendicular, aligned, etc.) within acceptable manufacturing tolerances. For example, as used herein, the term “substantially parallel” is used to denote elements that are parallel or that vary from a parallel arrangement within an acceptable margin of error, such as +/−5°, although it will be recognized that greater and/or lesser deviations can exist based on manufacturing processes and/or other manufacturing requirements.

Conditional language, such as “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments.

The methods, systems, and structures described for the ankle herein may be adapted to other applications in arthroplasty, including but not limited to the knee, shoulder, hip, elbow, and other joints.

Referring to FIGS. 1-5, an ankle prosthesis 100 according to an embodiment of the invention includes a tibial stem 110 and a tibia tray 120 configured to be attached to a prosthetic joint articulating surface. Optionally, the ankle prosthesis 100 may be fabricated such that the tibial stem 110 and the tibia tray 120 are monolithic, e.g., made integral with one another as one piece. As shown in FIG. 3, the tibial stem 110 may include a leading end 111, a trailing end 112, and a longitudinal axis L.

The tibia tray 120 extends from the trailing end 112 of the tibial stem 110. The tibial stem 110 may be sized and configured to be inserted in an intramedullary canal defined by the interior bone surface of a tibia. The tibial stem 110 may include one or more retractable members 130 configured to be controllably movable between a retracted position and an outwardly extended position that is away from the tibial stem 110 so as to in a deployed or extended position. In the retracted position, the one or more retractable members 130 may be contained within the envelope of the tibial stem 110 and do not extend outside of openings 116 in the tibial stem 110. In use, after the tibial stem 110 has been placed within the intramedullary canal of a tibia, the one or more retractable members 130 may be moved from their retracted position outwardly and away from the longitudinal axis L so that the one or more retractable members 130 engage the surface of the bone defining the intramedullary canal's so as to enhance anchoring of the tibial stem 110 within the tibia. Referring to FIG. 1, the tibia tray 120 may also include a tooling interface 122 that may be used to fit tools used to handle, place, locate, or replace the ankle prosthesis 100 during surgery. As shown, the tooling interface 122 may include circular recesses in a side of the tibia tray 120. Optionally, the tooling interface 122 may be threaded or tapered, and may be any suitable shape.

The tibial stem 110 may include one or more retractable members 130 (shown as two in the figures). In many situations, having two retractable members 130 may provide anchoring configurations that are more symmetrical. The symmetry involved here may be planar symmetry or radial symmetry with respect to the longitudinal axis L of the tibial stem 110. Retraction of the retractable members 130 allows for in-situ installation, adjustment, repositioning, and removal of the tibial stem 110 as required by the surgeon. Referring to FIG. 2, the tibia tray 120 may include a channel 124 extending between a pair of opposed rails 124A and 124B so as to receive a prosthetic joint surface. The channel 124 in the tibia tray 120 may extend in at least one of an anterior-posterior direction, medial-lateral direction, and in an oblique direction.

Referring to FIGS. 4 and 5, the retractable members 130 extend away from the longitudinal axis L of the tibial stem 110 when moving from their retracted positions outwardly and away from the longitudinal axis L to the deployed position. The one or more retractable members 130 may retract toward the longitudinal axis L of the tibial stem 110 when moving from their deployed positions to their retracted positions. The tibial stem 110 may include an elongated generally cylindrical shell defining an internal cavity 115 that is open at the trailing end 112. An opening 116 is provided in the generally cylindrical shell of the tibial stem 110 for each of the retractable members 130. The retractable members 130 extend outward through the openings 116 from the retracted position. The in and out movements of the retractable members 130 allow for suitable anchoring and eases release of the tibial stem 110 during relocation or replacement of the prosthesis 100. Although, the shape of the shell forming the tibial stem 110 is referred to as being generally cylindrical, the invention encompasses a variety of shapes for the shell other than those having circular or oval cross-sections. The term “generally cylindrical” as used herein is intended to encompass a structure for the shell that may have a variety of other cross-sectional shapes such as polygons (i.e., a triangle, a quadrilateral, a pentagon, a hexagon, a heptagon, a cone, an octagon, etc.). Additionally, the term “generally cylindrical” as used herein is intended to encompass structures that may not have a continuous solid shell.

As best viewed in FIG. 3, the tibial stem 110 may further include a rotational actuator 117 provided within the internal cavity 115. The rotational actuator 117 is configured to rotate within the internal cavity 115 around the longitudinal axis L. Referring to FIG. 6, each of the retractable members 130 may include an engagement end 131, teeth 132, and a tail end 133. The teeth 132 are engaged with a gear portion 118 of the rotational actuator 117. The engagement end 131 is a free end that is movable through its respective opening 116 to engage the bone surface, that defines the intramedullary canal, as the prosthesis 100 is installed inside the intramedullary canal of a tibia. The gear portion 118 may include a circular gear including teeth to match the teeth 132 of the retractable members 130. The movement of the retractable members 130 from the retracted position to the deployed position is controllably achieved by rotating the rotational actuator 117 within the internal cavity 115. The movement of the rotational actuator 117 may be either clockwise or counter-clockwise around the longitudinal axis L.

The rotational movement of the rotational actuator 117 may be controlled by providing a tool interface. By way of example, the base of the rotational actuator 117 may be provided with a tool-receiving socket 117A (See FIGS. 2 and 3) at the bottom end so that a tool, e.g., a wrench or a screwdriver, may be used to turn the rotational actuator 117 and control the movement of the retractable members 130. To limit over rotation of the rotational actuator 117, the tail end 133 of the retractable members 130 may include a flat feature (shown in FIG. 6) that is not a tooth to cause interference between the retractable members 130 and the rotational actuator 117 when the tail end 133 engages with the rotational actuator 117.

Referring to FIGS. 7-9, an ankle prosthesis 200 formed in accordance with another embodiment includes a groove 219 that may be defined in the mushroom-shaped top of a rotational actuator 217 and a pin SP may be inserted in the leading end 211 of the tibial stem 210 and into the groove 219 so that there is a hard-stop to prevent rotation of the rotational actuator 217 once the retractable members 130 reach the deployed position. FIG. 8 is a section view where the leading end 211 has been removed so the groove 219 is visible. FIG. 9 is a view with the leading end 211 and the tibial stem 210 transparent so that the groove 219 and pin SP are visible.

Referring again to FIG. 3, in another embodiment of the invention the rotational actuator 117 may be retained within the cavity 115 using a retaining pin RP. The tibial stem 110 may define a through-hole to receive the retaining pin RP. The through-hole is positioned such that the retaining pin RP extends through the through-hole of the tibial stem 110 and is aligned to fit under a mushroom-shaped top of the rotational actuator 117, as shown in the cross-sectional view of FIG. 3. In other embodiments, more than one retaining pin RP may be used to retain the rotational actuator 117. The tibial stem 110 may be made of a shape memory alloy such as Nitinol so that the super elastic properties or the memory properties of such alloy may be employed to enhance the function of the retractable members 130.

In further embodiments, the tibial stem 110 and/or the tibia tray 120 may be made of any material commonly used in the prosthetic arts, including, but not limited to, metals, ceramics, titanium, titanium alloys, tantalum, chrome cobalt, surgical steel, polyethylene, absorbable polymer, or any other total joint replacement metal and/or ceramic via traditional subtractive manufacturing or additive manufacturing techniques. In some embodiments, the tibial stem 110 and/or the tibia tray 120 may include a coating of Biofoam™, Adaptis™, porous metal, sintered glass, artificial bone, any uncemented metal or ceramic surface, or a combination thereof that would promote bony in-growth. The tibial stem 110 and/or the tibia tray 120 may further be covered with one or more coatings, such as, antimicrobial, antithrombotic, and osteoinductive agents, or a combination thereof. In some embodiments where the above-mentioned porous coating is provided, these agents may further be carried in a biodegradable carrier material with which the pores in the porous coating may be impregnated.

It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications may be devised by those skilled in the art without departing from the scope of the invention. Accordingly, the invention is intended to embrace all such alternatives, modifications, and variances that fall within the scope of the appended claims.

Claims

1. A prosthesis, comprising: a stem including a leading end, a trailing end, a longitudinal axis, and a rotational actuator including a tool-receiving socket defined at a first end and located within an internal cavity defined by an elongate hollow shell that is open at the trailing end with an opening defined in the shell through which a retractable member can move between a retracted position within the hollow shell and a deployed position by rotation of the tool-receiving socket, the internal cavity having an open end, a rotational actuator being configured with a circular gear including gear teeth and arranged so as to rotate within the internal cavity and about the longitudinal axis and coupled to the retractable member, which includes an engagement end, member teeth operatively engageable with the gear teeth, and a flat tail end, such that the engagement end is movable through the opening defined in the cylindrical shell so that rotating the rotational actuator while engaging the tool-receiving socket, urges the member teeth to operatively engage the gear teeth so that the retractable member is moved outwardly from the retracted position to the deployed position determined by the engagement of the flat tail end with the gear teeth so as to effect deployment of the retractable member into engagement with a bone; anda tray extending from the trailing end configured to be attached to a prosthetic joint articulating surface and sized and configured to be placed in a resected joint, the tray defining a central opening that is positioned between a pair of opposed rails and in aligned communication with the tool-receiving socket when attached to the prosthetic joint so that the tool-receiving socket (i) causes the rotation of the rotational actuator within the internal cavity when rotationally engaged by a tool and (ii) is covered by a portion of the prosthetic joint articulating surface upon deployment of the retractable member through the open end.

2. The ankle prosthesis of claim 1, wherein the rotational actuator includes a gear portion that meshes with the teeth of the retractable member, and rotating the rotational actuator rotates the gear portion and moves the retractable member.

3. An ankle prosthesis, comprising: a tibial stem including a leading end, a trailing end, an internal cavity defined by an elongate hollow shell that is open at the trailing end with an opening defined through the shell, a longitudinal axis, and a rotational actuator configured with a circular gear including gear teeth arranged so as to rotate within the internal cavity and about the longitudinal axis of the tibial stem;a tibia tray configured to be attached to a prosthetic joint articulating surface, whereinthe tibia tray defines a central opening between a pair of opposed rails and extends from the trailing end and is sized and configured to be placed in a resected tibia;the tibial stem is configured to be placed in a tibial intramedullary canal, and includes a retractable member having an engagement end, member teeth operatively engageable with the gear teeth, and a flat tail end, such that the engagement end is movable through the opening defined in the hollow shell, and having a tool-receiving socket defined at a first end and configured to be located with the internal cavity in communication with the central opening of the tibia tray so as to provide controlled rotational movement between (i) a retracted position and (ii) a deployed position by rotating the rotational actuator within the internal cavity so that the member teeth operatively engage the gear teeth thereby urging the retractable member to move outwardly and away from the longitudinal axis of the tibial stem such that in the retracted position the retractable member is contained substantially within the tibial stem, when in the deployed position the engagement end of the retractable member engages the bone surface that defines the intramedullary canal as the flat tail end of the retractable member engages the gear teeth thereby anchoring the tibial stem within the tibia; anda prosthetic joint articulating surface coupled to the tibia tray so as to cover the tool-receiving socket.

4. The ankle prosthesis of claim 3, wherein the retractable member is configured to be moved back to the retracted position from the deployed position when the tool-receiving socket is uncovered.

5. The ankle prosthesis of claim 3, wherein the tibia tray includes a channel extending between the pair of opposed rails to receive the prosthetic joint articulating surface.

6. The ankle prosthesis of claim 5, wherein the channel extends in at least one of an anterior-posterior direction, a medial-lateral direction, and in an oblique direction.

7. The ankle prosthesis of claim 3, wherein the tool-receiving socket is accessed in a channel of the tibia tray that extends between a pair of opposed rails to receive the prosthetic joint surface.

8. The ankle prosthesis of claim 3, further comprising a coating on the tibial stem and/or the tibia tray to promote bony in-growth.

9. An ankle prosthesis, comprising: a tibial stem including a leading end, a trailing end, a longitudinal axis, and an actuator located within an internal cavity defined by an elongate hollow shell that is open at the trailing end with an opening defined through the shell, the internal cavity having an open end, the actuator including a tool interface and a circular gear including gear teeth arranged so as to rotate within the internal cavity so as to be configured to move within the internal cavity and about the longitudinal axis of the tibial stem and coupled to a retractable member having an engagement end, member teeth operatively engageable with the gear teeth, and a flat tail end, such that the engagement end is movable through the opening defined in the hollow shell so as to thereby effect deployment of the retractable member through the opening in the hollow shell and away from the longitudinal axis of the tibial stem by rotation of the tool interface determined by the engagement of the gear teeth with the flat tail end; anda tibia tray extending from the trailing end configured to be attached to a prosthetic joint articulating surface and sized and configured to cover the tool interface when placed in a resected tibia.

10. The ankle prosthesis of claim 9, wherein the retractable member is configured to be controllably movable by the actuator between (i) a retracted position and (ii) a deployed position that is outward and away from the longitudinal axis.

11. The ankle prosthesis of claim 10, wherein in the retracted position the retractable member is contained substantially within internal cavity and when in the deployed position the retractable member extends from the internal cavity so as to engage the bone surface that defines the intramedullary canal thereby anchoring the tibial stem within the tibia.

12. The ankle prosthesis of claim 10, wherein the retractable member is configured to be moved back to the retracted position from the deployed position when the tool interface is uncovered.

13. The ankle prosthesis of claim 10, wherein the tibia tray includes a channel extending between a pair of opposed rails to receive the prosthetic joint articulating surface.

14. The ankle prosthesis of claim 13, wherein the channel extends in at least one of an anterior-posterior direction, a medial-lateral direction, and in an oblique direction.