WO2014076157A1

WO2014076157A1 - Pre-tensioned bone anchors and methods of using and manufacturing the same

Info

Publication number: WO2014076157A1
Application number: PCT/EP2013/073769
Authority: WO
Inventors: Benjamin Geebelen; Nils FABER
Original assignee: Materialise N.V.
Priority date: 2012-11-14
Filing date: 2013-11-13
Publication date: 2014-05-22

Abstract

Devices and methods for anchoring implants to bone are disclosed. A pre-tensioned device (200) for anchoring an implant to bone includes a base element (210), a head element (220), and a tensioning element (230). The base element includes a bone engagement portion (213), and the head element includes an implant engagement portion (223). The tensioning element can serve to create a predetermined amount of tension within the device. A method of anchoring an implant to bone can include inserting such a device through a hole in an implant into bone, with the tensioning element set to a predetermined tension.

Description

PRE-TENSIONED BONE ANCHORS AND METHODS OF USING AND

MANUFACTURING THE SAME

BACKGROUND

Field of the Invention

[0001] The present disclosure relates to medical devices and methods of using and manufacturing the same. More particularly, the disclosure relates to orthopedic devices used to secure implants or other materials to bone. The disclosure also relates to methods for using and manufacturing orthopedic anchoring devices.

Description of the Related Art

[0002] Knee and hip arthroplasties, as well as other joint replacement surgeries, are becoming increasingly prevalent in our aging society. In joint replacement surgeries, orthopedic implant devices are often used to replace joints that have degenerated, for example, due to traumatic injury or arthritis. Many orthopedic implants, such as the tibial component of a total knee prosthesis, are fixed in the patient by means of an intramedullary stem. Such a stem has certain drawbacks. For example, surgical insertion of an intramedullary stem requires reaming out the medullary cavity of a bone. Such an invasive procedure can cause damage to weakened or brittle bones, can cause loss of bone stock and bone density in already weakened bones, and can result in long recovery times. Moreover, the stems are typically cemented in place, introducing polymer bone cements into the human body. The long-term biocompatibility of these polymer cements has not been fully established. Additionally, fixating an implant in this manner does not correspond with the natural loading, bone growth and bone remodeling mechanisms of the human body. Consequently, the bone stem can loosen over time and may result in implant failure.

[0003] To move away from implants having intramedullary stems, an alternative fixation mechanism must be provided. One option is to fixate joint implants to bone using orthopedic bone screws. However, currently available bone screws do not create sufficient force to provide for the long-term fixation of joint implants to bone. Consequently, a need exists for an improved orthopedic anchoring device. SUMMARY

[0004] Various implementations of systems, methods and devices within the scope of the appended claims each have several aspects, no single one of which is solely responsible for the desirable attributes described herein. Without limiting the scope of the appended claims, some prominent features are described herein.

[0005] The present application relates generally to orthopedic anchoring devices. Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, embodiments, and advantages will become apparent from the description, the drawings, and the claims.

[0006] One aspect of this disclosure provides a pre-tensioned device for anchoring an implant to bone. The pre-tensioned device includes a base element having a bone engagement portion, a head element having an implant engagement portion, and a tensioning element configured to create a pre-determined amount of tension within the pre-tensioned device. In one embodiment, the base element also includes a base shaft extending proximally from the bone engagement portion, and the head element includes a head shaft extending distally from the implant engagement portion. The tensioning element has a distal end secured to the base element and a proximal end secured to the head element. In some embodiments, the tensioning element extends through a central bore that includes an interior bore of the head shaft and an interior bore of the base shaft. In other embodiments, the tensioning element wraps around at least a portion of an outer surface of the base shaft and at least a portion of an outer surface of the head shaft. In some embodiments, the pre-tensioned device further includes a spreading element configured to move the base element distally relative to the head element to define an amount of tension in the tensioning element. In some embodiments, the base shaft is disposed at least partially within or around the head shaft and is configured to move longitudinally relative to the head shaft. In some embodiments, the base shaft is configured to interact with the head shaft to limit rotational movement and lateral movement of the base shaft relative to the head shaft. In some embodiments, the tensioning element includes a spring having a distal end secured to the base element and a proximal end secured to the head element, and the spreading element includes a pin configured to stretch the spring by a pre-determined amount. The amount of tension within the device may be determined, in part, by the length of the pin. In some embodiments, the pin is removable and the spring is configured to exert a compressive force between the implant and the bone upon removal of the pin. In other embodiments, the pin is fixed, at least in part, between the base element and the head element. In some embodiments, the base element, the head element, and the spring form a single, integrated unit.

[0007] Another aspect of the disclosure provides a method of anchoring an implant to bone. The method includes inserting a pre-tensioned anchoring device through a hole in an implant and into a bone, wherein the anchoring device includes abase element, ahead element, and a tensioning element. The tensioning element has a distal end secured to the base element and a proximal end secured to the head element, and the tensioning element is set to a predetermined tension. The method further includes securing the base element to the bone and coupling the head element to the implant. Some embodiments further include releasing the tension in the tensioning element to exert a compressive force between the implant and the bone. In some embodiments, securing the base element to the bone includes screwing or drilling at least a portion of the base element into cortical bone. In some embodiments, releasing tension in the tensioning element includes at least partially removing a pin positioned at least partially between the base element and the head element. In some embodiments, the anchoring device further includes a spreading element configured to move the base element distally relative to the head element to create tension in the tensioning element.

[0008] An additional aspect of the disclosure provides a method of manufacturing a pre-tensioned orthopedic anchoring device. The method includes creating a device design for an orthopedic anchoring device, and manufacturing the orthopedic anchoring device based on the device design, wherein the orthopedic anchoring device is manufactured one layer at a time. In one embodiment of the method, the device design includes a base element having a bone engagement portion, a head element having an implant engagement portion, and a tensioning element having a distal end secured to the base element and a proximal end secured to the head element, wherein the tensioning element can be set to a predetermined tension. In some embodiments, the device design is a digital model created on a computer. In some embodiments, manufacturing the orthopedic anchoring device is performed using rapid prototyping and manufacturing techniques. In some embodiments, manufacturing the orthopedic anchoring device is performed using metal sintering.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above-mentioned aspects, as well as other features, aspects, and advantages of the present technology will now be described in connection with various embodiments, with reference to the accompanying drawings. The illustrated embodiments, however, are merely examples and are not intended to be limiting. Throughout the drawings, similar symbols typically identify similar components, unless context dictates otherwise. Note that the relative dimensions of the following figures may not be drawn to scale.

[0010] FIG. 1 A illustrates an example of a knee with a total knee prosthesis secured using prior art methods and devices.

[0011] FIG. IB illustrates an example of a knee with a total knee prosthesis secured, at least in part, with one embodiment of a presently disclosed anchoring device.

[0012] FIG. 2 illustrates a perspective view of one embodiment of an anchoring device in a neutral position.

[0013] FIG. 3 illustrates a perspective view of one embodiment of an anchoring device in a stretched position.

[0014] FIG. 4 illustrates a perspective view of one embodiment of a spreading element.

[0015] FIG. 5A illustrates a side view of one embodiment of an anchoring device.

[0016] FIG. 5B illustrates a cross-section of the anchoring device of FIG. 5A taken along line 5B-5B.

[0017] FIG. 6 illustrates a perspective view of one embodiment of an anchoring device with a spreading element in place.

[0018] FIG. 7 illustrates a flow diagram depicting one embodiment of a method of manufacturing an anchoring device.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

[0019] In the following detailed description, reference is made to the accompanying drawings, which form a part of the present disclosure. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and form part of this disclosure.

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. It will be understood by those within the art that if a specific number of a claim element is intended, such intent will be explicitly recited in the claim, and in the absence of such recitation, no such intent is present. For example, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises," "comprising," "includes," and "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the fist.

[0021] To assist in the description of the devices and methods described herein, some relational and directional terms are used. As recited within this disclosure, the "longitudinal axis" of the anchoring device is the elongated axis running through the length of the device from a proximal head to a distal tip.

[0022] "Connected" and "coupled," and variations thereof, as used herein include direct connections, such as being contiguously formed with, or glued or otherwise attached directly to, on, within, etc. another element, as well as indirect connections where one or more elements are disposed between the connected elements. "Connected" and "coupled" may refer to a permanent or non-permanent (i.e., removable) connection. [0023] "Secured" and variations thereof as used herein include methods by which an element is directly secured to another element, such as being glued, screwed or otherwise fastened directly to, on, within, etc. another element, as well as indirect means of securing two elements together where one or more elements are disposed between the secured elements.

[0024] "Proximal" and "distal" are relational terms used herein to describe position from the perspective of a medical professional using the anchoring device. For example, as compared to "distal," the term "proximal" refers to a position that is located more closely to the medical professional and to the insertion point through which the anchoring device enters a patient's body.

[0025] Embodiments disclosed herein relate to orthopedic anchoring devices for securing materials, such as implants, to bone. The orthopedic anchoring devices of the present invention are configured to engage with both implants and bone and may advantageously be used to secure implants to bone without the need for an intramedullary stem. The orthopedic anchoring devices of various illustrated embodiments may include tensioning mechanisms configured to achieve higher compressive forces between bone and implant man can be achieved with conventional bone screws. The compressive forces generated by the presently disclosed orthopedic anchoring devices may pull an implant and bone towards one another, thereby reinforcing the connection between the two. Moreover, the compressive forces may stimulate bone growth around the orthopedic anchoring device, facilitating a secure fixation within the bone. Importantly, bone may adapt to the loads under which it is placed. When loading on a bone increases, the bone tends to adapt by growing and remodeling itself over time. Such bone growth and remodeling about the site of the orthopedic anchoring device may facilitate long-term fixation of the orthopedic anchoring device within the bone.

[0026] FIG. 1A illustrates an example of a knee 100 with a total knee prosthesis secured using prior art methods and devices. The bones surrounding the knee include the femur 101 and the tibia 105. Knee arthroplasty (i.e., total knee replacement surgery) is often performed when cartilage between the femur 101 and the tibia 105, and/or the ends of the bones themselves, erode. In knee arthroplasty, the joint of the knee is replaced, at least by a femoral component implant 102 and a tibial component implant 103. Currently, the tibial component implant 103 typically comprises a long intramedullary stem 104, included to secure the tibial component implant 103 in place. To secure the implant, a patient's medullary canal inside the tibia bone 1 OS is reamed out and marrow and/or other bone components are removed. Bone cement and the intramedullary stem 104 are then inserted. This is considered an extremely invasive procedure, with long and painful recoveries. The embodiments described herein create an improved anchoring device such that intramedullary stems 104 may no longer be needed in at least some joint replacement surgeries.

[0027] FIG. IB illustrates an example of a knee 100 with a total knee prosthesis secured, at least in part, with one embodiment of the presently disclosed orthopedic anchoring device 200. In some embodiments, the anchoring device 200 may be inserted through a hole in an implant, such as the tibial component implant 103 of FIG. IB, and into bone 105. In some embodiments, the anchoring device 200 is inserted in a pre-tensioned state and configured to engage with both the implant 103 and the bone 105. The anchoring device 200 of various embodiments is configured such that, once fully inserted into the implant 103 and bone 105, the anchoring device 200 can exert a compressive force between the implant 103 and the bone 105. This compressive force may advantageously stimulate bone growth about the anchoring device 200 and thus facilitate long-term fixation of the orthopedic anchoring device 200 within the bone 105.

[0028] While the disclosure herein describes an orthopedic anchoring device 200 for use with a knee arthroplasty implant, one of skill in the art will readily appreciate that the presently described orthopedic anchoring device 200 can equally be used with other joint arthroplasty implants, as well as other partial joint replacement implant devices, and other bone implants more generally. The orthopedic anchoring device 200 set forth in this disclosure can be broadly used to secure implants, plates, and/or other materials to bone.

[0029] FIG. 2 illustrates a perspective view of one embodiment of an anchoring device 200. In various embodiments, the anchoring device 200 includes a base element 210 configured for insertion into, and engagement with, bone. The base element 210 includes one or more engagement features to facilitate such insertion and engagement. In the depicted embodiment, the base element 210 includes external threads 211 configured to facilitate the drilling of the base element 210 into cortical bone. The threads 211 are disposed on at least a portion of an outer surface of the base element 210. Additionally, as shown in FIG. 2, in some embodiments, the base element 210 has a tapered and/or sharp distal tip 212 configured to facilitate insertion of the anchoring device 200 into bone. In other embodiments, additional and/or different engagement features may be present, such as, for example, teem, barbs, or other protrusions disposed on the surface of the base element 210.

[0030] The anchoring device 200 further includes a head element 220 configured for insertion into, and engagement with, an orthopedic implant. The head element 220 of some embodiments includes one or more engagement features or characteristics to facilitate such engagement. For example, in some embodiments, the head element 220 may be over-sized in relation to a hole within the implant through which the remainder of the anchoring device 200 passes. Such a configuration would cause a distal face of the head element 220 to contact and engage at least a portion the implant. In other embodiments, such as the embodiment shown in FIG. 2, the head element 220 includes external threads 221 disposed on at least a portion of an outer surface of the head element 220. The threads 221 of some embodiments are configured to create a frictional connection between the head element 220 and the implant into which the head element 220 is placed. Additionally, the head element 220 of some embodiments includes a screw drive design 222 configured to facilitate rotation, and consequently insertion, of the anchoring device 200. Any screw drive design 222 known to those skilled in the art may be used, including, for example, Phillips, hex, hex socket, or a slotted design.

[0031] Continuing with FIG. 2, the anchoring device 200 also includes a mechanism for generating tension between the base element 210 and the head element 220. A pre-tensioned anchoring device 200 can advantageously create a compressive force between an implant and bone, thereby facilitating long-term fixation of the anchoring device 200. Any suitable mechanism for generating tension known to those skilled in the art may be used. In the embodiment illustrated in FIG. 2, the anchoring device 200 includes a tensioning element in the form of a coiled spring 230. The spring 230 has a distal end secured to the base element 210 and a proximal end secured to the head element 220. At least through this connection with the spring 230, the base element 210, the head element 220, and the spring 230 are all directly or indirectly connected. Through this connection, the base element 210 and the head element 220 can translate with respect to each other along the longitudinal axis of the anchoring device 200. In such an embodiment, tension can be created by stretching the spring 230 longitudinally beyond its neutral position. The amount of tension that can be created in a spring 230 is determined by the spring's properties, such as, for example, the material of the spring, the thickness of the spring, the free length of the spring, the number of active windings, and the size of the spring's outer diameter. With any given spring 230, the amount of pre-tensioning exerted on the anchoring device 200 varies according to the distance over which the spring 230 is stretched. The spring 230 depicted in FIG. 2 is in a relaxed or neutral position.

[0032] FIG. 3 illustrates a perspective view of one embodiment of an anchoring device 200 wherein the spring 230 is in a stretched position. As shown in FIG. 3, the base element 210 of some embodiments includes a bone engagement portion 213 and a base shaft 214. The base shaft 214 extends proximally from the bone engagement portion 213. In some such embodiments, the threads 211 and/or other bone engagement features are positioned on the bone engagement portion 213 of the base element 210. Similarly, the head element 220 of some embodiments includes an implant engagement portion 223 and a head shaft 224. The head shaft 224 extends distally from the implant engagement portion 223. In some such embodiments, the threads 221 and/or other implant engagement features are positioned on the implant engagement portion 223 of the head element 220.

[0033] As illustrated in FIG. 3, in some embodiments, the base shaft 214 is formed of an outer base shaft wall 215, which defines an inner bore 216, and the head shaft 224 is formed of an outer head shaft wall 225, which defines an inner bore 226. In some such embodiments, one of either the base shaft 214 or head shaft 224 is positioned at least partially inside the other shaft 214, 224. In such a configuration, at least a distal portion of the head shaft 224 and a proximal portion of the base shaft 214 overlap. The inner bores 216, 226 form one continuous central bore 240. The head shaft 224 and base shaft 214 are configured to translate relative to each other along the longitudinal axis of the anchoring device 200. As the shafts 214, 224 translate toward each other, the central bore 240 shortens, and as the shafts 214, 224 translate away from each other, the central bore 240 lengthens. In some such embodiments, the spring 230 is housed within the central bore 240. With such a configuration, when the head element 220 slides distally relative to the base element 210, the implant engagement portion 223 moves closer to the bone engagement portion 213, the head shaft 224 increases its overlap with the base shaft 214, the central bore 240 shortens, and the spring 230 compresses. Conversely, when the head element 220 slides proximally relative to the base element 210, the two components move farther apart, the head shaft 224 decreases its overlap with the base shaft 214, the central bore 240 lengthens, and the spring 230 stretches. In other embodiments (not shown), the spring or other tensioning element is wrapped around at least a portion of an outer base shaft wall and at least a portion of an outer head shaft wall. Similar to the embodiment depicted in FIG. 3, in such embodiments, when a head element slides distally relative to abase element, an implant engagement portion moves closer to a bone engagement portion, the head shaft increases its overlap with the base shaft, and the spring compresses. When the head element slides proximally relative to the base element, the two components move farther apart, the head shaft decreases its overlap with the base shaft, and the spring stretches. The inner of the head shaft and the base shaft may be hollow or partially or substantially solid. In the various embodiments, all movement is relative, and the head element 220 and the base element 210 are configured to slide relative to the other.

[0034] Continuing to refer to FIG. 3, in some embodiments, the base shaft wall 215 comprises a plurality of fixed struts 217 indirectly connected to each other by a ring 218 disposed at a proximal end of the base element 210. In other embodiments, the base shaft wall 215 may be substantially uniform, forming a solid circumferential wall around the inner bore 216. In still other embodiments, other wall designs may be used. Similarly, in some embodiments, the head shaft wall 225 may be substantially uniform, forming a solid circumferential wall around the inner bore 226. In other embodiments, other wall designs may be used. For example, in the embodiment depicted in FIG.3, the head shaft wall 225 comprises a plurality of struts 227 and one or more feet 228. The feet 228 are disposed on the distal ends of one or more of the struts 227. In some embodiments, the feet 228 may connect to one, two, or more struts 227 on the head element 220. The feet 228 are configured to protrude radially outward from the longitudinal axis of the anchoring device 200. In some such embodiments, the feet 228 of the head shaft 224 are configured to extend radially outward between the struts 217 of the base shaft 214. The width of both the feet 228 and the spaces between the struts 217 of the base shaft 214 may be selected such that the feet 228 have a close fit, but not a tight fit, between adjacent struts 217. Such a configuration may advantageously allow the shafts 214, 224 to slide relative to each other along the longitudinal axis without significant frictional resistance between the feet 228 and the struts 217, while at the same time blocking all other relative movements. By aligning the feet 228 of the head shaft 224 between the fixed struts 217 of the base shaft 214, rotational movement and lateral movement between the shafts is limited. [0035] As mentioned above, in some embodiments, the struts 217 that comprise the base shaft wall 215 are indirectly connected to each other by a ring 218 disposed at a proximal end of the base element 210. Such a configuration may advantageously create a longitudinal blocking mechanism between the two shafts 214, 224. The longitudinal blocking mechanism blocks the distal end of the head shaft 224 from sliding proximally beyond the proximal end of the base shaft 214. That is, the longitudinal blocking mechanism prevents the two shafts 214, 224 from sliding so far away from each other that they completely disengage from one another. Imposing such a limit on translational movement may help protect the spring 230 from damage or failure that could result if the spring 230 were stretched too far.

[0036] In other embodiments, different longitudinal blocking mechanisms may be used to prevent the distal end of the head shaft 224 from sliding proximally beyond the proximal end of the base shaft 214. As with the feet and strut example above, other blocking mechanisms may also have the added benefit of limiting rotational and lateral movement of the shafts 214, 224 relative to each other. In one non-limiting example (not shown), the walls of the shafts may be solid. The outermost shaft may have a groove running longitudinally along an interior portion of the shaft wall. The inner shaft may have a complimentary ridge line that fits within the groove. Such an embodiment limits movement of the shafts to longitudinal sliding of the ridge within the groove. Rotational and lateral movement is restricted. Moreover, if the groove does not run the entire length of the shaft wall, but instead stops short, the embodiment will also serve as a longitudinal blocking mechanism. In another embodiment (not shown), the inner-most shaft may have an outer wall having a non-circular cross-section. For example, the cross-section of the wall may form a square, hexagon, star, or other non-circular shape. In such an embodiment, the outer-most shaft may have a complementary-shaped inner bore. As with the other embodiments described within this paragraph and other embodiments obvious to those of ordinary skill in the art, such a design would limit movement of the shafts to longitudinal sliding; rotational and lateral movement would be substantially restricted.

[0037] Various embodiments of the pre-tensioned anchoring device provide the ability to include a predetermined amount of tension in the device. In the embodiment shown in FIG. 3, setting a specific predetermined amount of tension is provided by controlling the longitudinal movement (e.g., the amount of stretching) experienced by the spring 230. As mentioned above, when the head element 220 slides proximally relative to the base element 210, the two components move farther apart, the head shaft 224 decreases its overlap with the base shaft 214, the central bore 240 lengthens, and the spring 230 stretches. Thus, the amount of stretching experienced by the spring 230 can be regulated by controlling the distance between the head element 220 and base element 210. Various components and/or mechanisms can be used to control the distance between the elements 220, 210 of the anchoring device 200. This disclosure contemplates and incorporates the use of any suitable component and/or mechanism known to those skilled in the art, which can hold the head element 220 and base element 210 at a fixed distance relative to each other while the anchoring device 200 is inserted through an orthopedic implant and into bone.

[0038] FIG. 4 illustrates a perspective view of one example of a spreading element 400 configured to hold the head element 220 and base element 210 at a fixed distance relative to each other. The spreading element shown in FIG. 4 includes a pin 400 comprising a pin head 420 and a pin shaft 410. The pin 400 is sized for placement within the central bore 240 of the anchoring device and is configured to be coupled with the head element 220 and the base element 210. In some embodiments, the pin head 420 comprises external threading 421 or other coupling feature(s) disposed on at least a portion of the pin head 420 for engaging the implant engagement portion 223 of the head element 220. In some embodiments, the pin head 420 can be held securely in a fixed position within an inner lumen 242 of an implant engagement portion 223 (such as that shown in FIG. 5B) via a frictional fit, a snap fit, or other means of coupling known to those skilled in the art. In some embodiments, the pin head 420 comprises a screw drive 422. The screw drive 422 may be configured to facilitate insertion, rotation, and engagement of the pin head 420 with at least part of the implant engagement portion 223. In some embodiments, the pin shaft 410 has a distal tip 411 designed to interact with the bone engagement portion 213 of the base element 210. For example, the distal tip 411 may comprise a flat distal face suitable for abutting and applying forces to a proximal- facing surface of the bone engagement portion 213. In some embodiments, the bone engagement portion 213 may have a trough or recess 243 (see FIG. SB) configured to cradle the distal tip 411.

[0039] In various embodiments, the length of the selected pin 400 controls the amount of expansion and stretching experienced by the anchoring device 200. If the longitudinal length of a selected pin 400 exceeds the longitudinal length of the central bore 240 in the neutral position, the distal tip 411 will exert a translational force on the bone engagement portion 213 during insertion of the pin 400 into the anchoring device 200. The translational force results in distal longitudinal movement of the base element 210 and continues until the length of the central bore 240 accommodates the length of the selected pin 400. The spring 230 will correspondingly stretch with the longitudinal movement of the base element 210. Upon securing the pin head 420 within the head element 220, the anchoring device 200 will be held in place in this lengthened position. The spring 230, held in a stretched position, exerts tension on the anchoring device 200. A longer pin 400 will result in increased stretching of the spring 230 and increased tension, and a shorter pin 400 will result in less stretching of the spring 230 and less tension. Such tension will remain until the pin 400 is at least partially removed. In pin embodiments comprising threading 421 on the pin head 420, the pin 400 can be removed by unscrewing the pin 400 from its position within the implant engagement element 223. In such embodiments, upon partially or fully unscrewing the pin 400, the spring 230 is biased back towards its neutral configuration, thereby creating compressive forces on the head element 220 (and attached implant) and on the base element 210 (and attached bone). In other embodiments, the pin 400 may be fixedly and/or integrally attached within the anchoring device 200, positioned at least partially between the implant engagement element 223 and the bone engagement element 213, thereby holding the spring 230 at a fixed level of tension.

[0040] FIG. 5A and 5B illustrate a side view and a cross-sectional view, respectively, of one embodiment of an anchoring device 200. In the embodiment of FIG. 5A, the base element 210 and head element 220 are connected via a spring 230, and the spring 230 is in a neutral position. FIG. SA illustrates the cut line used to create the cross-section illustrated in FIG. 5B. In the illustrated cross-section, the above-mentioned inner lumen 242 of the implant engagement portion 223 of the head element 220 and the recess 243 within the bone engagement portion 213 of the base element 210 are visible. As shown in FIG. 5B, in some embodiments, the inner lumen 242 has complementary threading or other feature(s) to facilitate insertion and stabilization of the pin head 420 within the lumen 242. Additionally, in some embodiments, the inner lumen 242 connects to the central bore 240 to form a contiguous bore through which the pin 400 can extend. In some embodiments, the pin 400 may be inserted into, and removed from, the inner lumen 242 through the aperture 241 positioned on the proximal end of the head element 220.

[0041] FIG. 6 illustrates a perspective view of one embodiment of an anchoring device 200 with a spreading element 400 positioned within the lumen 242 (not visible) of the implant engagement portion 223 and extending through the central bore 240. The anchoring device 200 of FIG. 6, as currently depicted, is in a neutral position. However, with the spreading element 400 present, the anchoring device 200 could be transitioned into a stretched position by using the threads 421 and the screw drive 422 to move the spreading element 400 distally, advancing it further into the anchoring device 200. In its present configuration, the distal tip 411 (not visible) of the spreading element 400 is in contact with a proximal portion of the bone engagement element 213. Thus, as the spreading element 400 is advanced distally into the anchoring device 200, it will result in translational movement of the bone engagement element 213 in the distal direction and cause resultant stretching of the spring 230. Thus by advancing the spreading element 400 into the anchoring device 200, tension can be created within the anchoring device 200. The amount of tension created is dependent on the amount of stretching of the spring 230, and therefore, is dependent on the length of the spreading element 400.

[0042] In some embodiments, such as the embodiment of FIG. 6, the orthopedic anchoring device 200 may be a single, integrated structure. All of the orthopedic anchoring device components, including the base element 210, the head element 220, and the tensioning element 230, may be contiguously fabricated (e.g., formed from a single mold or a single additive manufacturing process). In some embodiments, the spreading element 400 may also form part of the contiguously fabricated structure. In other embodiments, the spreading element 400 is formed separately and removably inserted into the anchoring device 200 before surgical use. In still other embodiments, no spreading element is present. In some embodiments, each component of the anchoring device 200 may be a separately-formed structure. In such embodiments, fixation means must be used to securely affix the tensioning element 230 to the head element 220 and the base element 210. Any suitable fixation means may be used including, for example, glue, cement, welding or overmolding. In some embodiments, fixation means may also be used to affix the spreading element 400 in a set position at least partially between at least a portion of the head element 220 and a portion of the base element 210.

[0043] FIG. 7 illustrates a method of manufacturing a pre-tensioned orthopedic anchoring device, such as, for example the anchoring device 200. At block 701 , the method includes creating a device design for an orthopedic anchoring device, wherein the device design includes: a base element comprising a bone engagement portion, a head element comprising an implant engagement portion, and a tensioning element having a distal end secured to the base element and a proximal end secured to the head element, wherein the tensioning element can be set to a predetermined tension. In some embodiments, the device design is a digital model formed on a computer. At block 702, the method includes manufacturing the orthopedic anchoring device based on the device design. In the embodiment illustrated in FIG. 7, the orthopedic anchoring device is manufactured one layer at a time.

[0044] The design of the orthopedic anchoring device may be personalized by taking into account patient-specific features when designing the device. For example, the length and/or width of the anchoring device may be tailored according to the size of the bone, the density of the bone, the size of the implant, and/or the location of implantation. Similarly, the material used to form the anchoring device and/or the amount of tension set in the tensioning element may be tailored in accordance with such factors. In some embodiments, any pre-tensioned orthopedic anchoring device, including, for example, the pre-tensioned orthopedic anchoring device embodiments described above, may be manufactured through the manufacturing method described herein.

[0045] In some embodiments, the pre-tensioned orthopedic anchoring device is partially or completely made by additive manufacturing, which creates a three-dimensional (3- D) object by laying down successive layers of material. Advantageously, this method of manufacturing allows for the creation of a single unit in which the base element, head element, and tensioning element are formed together as an integrated device (in contrast to separately molded components that need to be coupled together after the molding process). Additive manufacturing technologies enable the manufacturing of intricately detailed devices at a sufficiently small scale to be useful for orthopedic anchoring. Additionally, with additive manufacturing, the 3-D object is often created directly from a digital model. Building from a digital model rather than, for example, a pre-formed mold, allows for relatively quick and inexpensive personalization and modification of the design. Accordingly, additive manufacturing allows for the integration of patient-specific features. For converting the design's digital image information into a three-dimensional object, any suitable technique known in the art may be used, such as, for example, a rapid prototyping technique.

[0046] Rapid Prototyping and Manufacturing (RP&M) may be defined as a group of techniques used to quickly fabricate a scale model of an object typically using three- dimensional (3-D) computer aided design (CAD) data of the object. Currently, a multitude of Rapid Prototyping techniques are available, including, for example, stereolithography (SLA), Selective Laser Sintering (SLS), Fused Deposition Modeling (FDM), and foil-based techniques.

[0047] A common feature of these techniques is that objects are typically built layer by layer. Stereolithography, presently the most common RP&M technique, utilizes a vat of liquid photopolymer "resin" to build an object one layer at a time. On each layer, an electromagnetic ray (e.g. one or several laser beams that are computer-controlled), traces a specific pattern on the surface of the liquid resin, the pattern defined by the two-dimensional cross-sections of the object to be formed. Exposure to the electromagnetic ray cures, or solidifies, the pattern traced on the resin and adheres it to the layer below. After a coat had been polymerized, the platform descends by a single layer thickness and a subsequent layer pattern is traced, adhering to the previous layer. A complete 3-D object can be formed by this process.

[0048] Fused deposition modeling (FDM) and related techniques make use of a temporary transition from a solid material to a liquid state, usually due to heating. The material is driven through an extrusion nozzle in a controlled way and deposited in the required place as described, for example, in U.S. Pat. No. 5,141,680, the entire disclosure of which is hereby incorporated by reference.

[0049] Foil-based techniques fix coats to one another by means of gluing or photo polymerization or other techniques and cut the object from these coats or polymerize the object. Such a technique is described in, for example, U.S. Pat. No. 5,192,539, also incorporated by reference in its entirety.

[0050] Typically, RP&M techniques start from a digital representation of the 3-D object to be formed. Generally, the digital image is sliced into a series of cross-sectional layers which can be overlaid to form the object as a whole. The RP&M apparatus uses this data for building the object on a layer-by-layer basis. The cross-sectional data representing the layer data of the 3-D object may be generated using a computer system and computer aided design and manufacturing (CAD/CAM) software.

[0051] A selective laser sintering (SLS) apparatus may be used for the manufacture of an orthopedic anchoring device template, instead of a computer model. Selective laser sintering (SLS) uses a high power laser or another focused heat source to sinter or weld small particles of plastic, metal, or ceramic powders into a mass representing the 3-D object to be formed. It should be understood however, that various types of rapid manufacturing and tooling may be used for accurately fabricating these orthopedic anchoring devices including, but not limited to, stereolithography (SLA), Fused Deposition Modeling (FDM) or milling.

[0052] The orthopedic anchoring devices described above (or parts thereof) may be manufactured using different materials. In some embodiments, if SLS is used as a RP&M technique, the orthopedic anchoring device may be fabricated from a polyamide such as PA 2200 supplied by EOS, Munich, Germany. In other embodiments, any material known by those skilled in the art, which is suitable for use with orthopedic implants and suitable for use in additive manufacturing, may be used. In some embodiments, only materials that are biocompatible (e.g. USP class VI compatible) with human bone are used. In some embodiments, the base element may be formed from any biocompatible material that attaches well to bone, and the head element may be formed from a material that attaches well to the selected orthopedic implant. In some embodiments, polylactic acid (PLA), polyether-emer- ketone (PEEK), titanium, or any other suitable plastic, metal, metal alloy, or composite material may be used to form all or part of the orthopedic anchoring device.

[0053] For purposes of summarizing the disclosure, certain aspects, advantages and features have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0054] While this invention has been described in connection with what are presently considered to be practical embodiments, it will be appreciated by those skilled in the art that various modifications and changes may be made without departing from the scope of the present disclosure. It will also be appreciated by those of skill in the art that parts mixed with one embodiment are interchangeable with other embodiments; one or more parts from a depicted embodiment can be included with other depicted embodiments in any combination. For example, any of the various components described herein and/or depicted in the Figures may be combined, interchanged or excluded from other embodiments. With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

[0055] While the present disclosure has described certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, and equivalents thereof.

Claims

WHAT IS CLAIMED IS:

1. A pre-tensioned device for anchoring an implant to bone, comprising:

a base element comprising a bone engagement portion,

a head element comprising an implant engagement portion, and

a tensioning element configured to create a pre-determined amount of tension within the pre-tensioned device.

2. The pre-tensioned device of Claim 1, wherein the base element further comprises a base shaft extending proximally from the bone engagement portion, the head element further comprises a head shaft extending distally from the implant engagement portion, and the tensioning element has a distal end secured to the base element and a proximal end secured to the head element.

3. The pre-tensioned device of Claim 2, wherein the tensioning element extends through a central bore comprising an interior bore of the head shaft and an interior bore of the base shaft.

4. The pre-tensioned device of Claim 2, wherein the tensioning element wraps around at least a portion of an outer surface of the base shaft and at least a portion of an outer surface of the head shaft.

5. The pre-tensioned device of any of Claims 1 -4, further comprising a spreading element configured to move the base element distally relative to the head element to define tension in the tensioning element.

6. The pre-tensioned device of any of Claims 2-5, wherein the base shaft is disposed at least partially within or around the head shaft and is configured to move longitudinally relative to the head shaft.

7. The pre-tensioned device of any of Claims 2-6, wherein the base shaft is configured to interact with the head shaft to limit rotational movement and lateral movement of the base shaft relative to the head shaft.

8. The pre-tensioned device of any of Claims 5-7, wherein the tensioning element comprises a spring having a distal end secured to the base element and a proximal end secured to the head element, and the spreading element comprises a pin configured to stretch the spring by a pre-determined amount.

9. The pre-tensioned device of Claim 8, wherein the amount of tension within the device is determined, in part, by the length of the pin.

10. The pre-tensioned device of any of Claims 8 or 9, wherein the pin is removable and the spring is configured to exert a compressive force between the implant and the bone upon removal of the pin.

11. The pre-tensioned device of any of Claims 8 or 9, wherein the pin is fixed, at least in part, between at least a portion of the base element and at least a portion of the head element.

12. The pre-tensioned device of any of Claims 8-11, wherein the base element, the head element, and the spring form a single, integrated unit.

13. The pre-tensioned device of any of Claims 1-12, wherein the bone engagement portion comprises an engagement feature configured for insertion into, and engagement with, cortical bone.

14. The pre-tensioned device of Claim 13, wherein the engagement feature comprises external threading disposed on at least a portion of the bone engagement portion.

15. A method of anchoring an implant to bone, comprising:

inserting a pre-tensioned anchoring device through a hole in an implant and into a bone, the anchoring device comprising: a base element,

a head element, and

a tensioning element having a distal end secured to the base element and a proximal end secured to the head element, the tensioning element set to a predetermined tension;

securing the base element to the bone; and

coupling the head element to the implant.

16. The method of Claim 15, further comprising releasing the tension in the tensioning element to exert a compressive force between the implant and the bone.

17. The method of any of Claims 15 or 16, wherein securing the base element to the bone comprises screwing or drilling at least a portion of the base element into cortical bone.

18. The method of any of Claims 15-17, wherein the anchoring device further comprises a spreading element configured to move the base element distally relative to the head element to create tension in the tensioning element.

19. The method of any of Claims 16-18, wherein releasing tension in the tensioning element comprises at least partially removing a pin positioned at least partially between the base element and the head element.

20. A method of manufacturing a pre-tensioned orthopedic anchoring device, comprising:

creating a device design for an orthopedic anchoring device, wherein the device design includes:

a base element comprising a bone engagement portion,

a head element comprising an implant engagement portion, and

a tensioning element having a distal end secured to the base element and a proximal end secured to the head element, wherein the tensioning element can be set to a predetermined tension; and manufacturing the orthopedic anchoring device based on the device design, wherein the orthopedic anchoring device is manufactured one layer at a time.

21. The method of Claim 20, wherein the device design is a digital model created on a computer.

22. The method of any of Claims 20 or 21 , wherein manufacturing the orthopedic anchoring device is performed using rapid prototyping and additive manufacturing techniques.

23. The method of any of Claims 20-22, wherein manufacturing the orthopedic anchoring device is performed using metal sintering.