FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to orthopedic implants and, in particular, it concerns adjustable orthopedic implants with releasable ratchet retention mechanisms.

It is known to deploy implants between tissue surfaces in a range of orthopedic procedures, and in various cases, it may be advantageous to use an implant to modify an angular relation between the tissue surfaces. By way of non-limiting example, this need may occur in spinal surgery, such as where there is a need for restoration of a lordotic and/or kyphotic angle between vertebrae, or to correct scoliosis misalignment between vertebrae.

In certain cases, it may be possible to adjust an angle between tissue contact surfaces after an implant is positioned within the body. An example of a device for perforrning such an adjustment is US Patent No. 6190414 to Young et al.

Also relevant to the present invention are implants which additionally, or alternatively, provide adjustment of at least one dimension, for example, height, to achieve a desired degree of axial distraction. SUMMARY OF THE INVENTION

The present invention is an orthopedic implant as defined in the appended claims.

According to the teachings of the present invention there is provided, an implant for insertion between two regions of tissue, the implant comprising: (a) a base having a first contact surface for contacting a first region of tissue, the base comprising a first portion displaceable relative to a second portion, the base assuming an initial length and being adjustable towards a second length when the first portion is displaced relative to the second portion; (b) a displaceable element having a second contact surface for contacting a second region of tissue; (c) a mechanical linking arrangement linking between the displaceable element and each of the first and second portions of the base such that relative displacement of the first and second portions causes displacement and/or rotation of the second contact surface relative to the first contact surface; and (d) a ratchet release element, wherein the first portion and the second portion are formed with complementary features defining a ratchet configuration comprising a plurality of ratchet teeth and a resiliency biased detent, the ratchet configuration being deployed to allow movement of the base from the initial length towards the second length, and to oppose movement of the base from the second length towards the initial length, and the ratchet release element being deployable to release engagement of the detent with the ratchet teeth to allow movement of the base from the second length towards the initial length.

According to a further feature of an embodiment of the present invention, the implant further comprises an insertable element inserted via an opening in a proximal end of the implant and engaging a distal one of the first and second portions of the base, the insertable element having at least one feature to bear on a part of the ratchet configuration so as to release engagement of the detent with the ratchet teeth to allow movement of the base from the second length towards the initial length. According to a further feature of an embodiment of the present invention, the implant further comprises a deployment rod inserted via an opening in a proximal end of the implant and engaging a distal one of the first and second portions of the base such that a force applied to one of the proximal and distal ends of the implant can be opposed by tension applied to the deployment rod, thereby causing movement of the base from the initial length towards the second length.

According to a further feature of an embodiment of the present invention, an engagement of the deployment rod with the distal portion is configured to allow a first motion of the deployment rod while maintaining engagement with the distal portion, and wherein the deployment rod has at least one feature deployed such that the first motion is effective to bring the at least one feature to bear on a part of the ratchet configuration so as to release engagement of the detent with the ratchet teeth to allow movement of the base from the initial length towards the second length.

According to a further feature of an embodiment of the present invention, the engagement is a threaded engagement, and wherein the first motion is a rotation effective to advance the deployment rod in relation to the threaded engagement.

According to a further feature of an embodiment of the present invention, the first contact surface and the second contact surface are each partial surfaces having one or more openings totaling at least a quarter of a total area of a contact surface footprint.

According to a further feature of an embodiment of the present invention, the relative motion of the second contact surface relative to the first contact surface includes a change of angle.

According to a further feature of an embodiment of the present invention, the relative motion of the second contact surface relative to the first contact surface includes a change of a distance separating between the first and second contact surfaces. According to a further feature of an embodiment of the present invention, the plurality of ratchet teeth are sequentially arranged to support movement of the base through a continuous range of lengths.

There is also provided according to an embodiment of the present invention, an implant for insertion between two regions of tissue, the implant comprising: (a) a base having a first contact surface for contacting a first region of tissue, the base comprising a first portion displaceable relative to a second portion, the base assuming an initial length and being adjustable towards a second length when the first portion is displaced relative to the second portion; (b) a displaceable element having a second contact surface for contacting a second region of tissue; and (c) a mechanical linking arrangement linking between the displaceable element and each of the first and second portions of the base such that relative displacement of the first and second portions causes displacement and/or rotation of the second contact surface relative to the first contact surface, wherein the first portion and the second portion are formed with complementary features defining a locking configuration comprising a plurality of teeth, at least one detent, and a mechanical clamping arrangement configured to selectively move the detent between a first position and a second position, the first position allowing movement of the base from the initial length towards the second length, and allowing movement of the base from the second length towards the initial length, and the second position opposing movement of the base from the initial length towards the second length, and opposing movement of the base from the second length towards the initial length.

According to a further feature of an embodiment of the present invention, the detent is resiliently biased, and the mechanical clamping arrangement is further configured to move the detent to a ratchet configuration to allow movement of the base from the initial length towards the second length, and to oppose movement of the base from the second length towards the initial length. According to a further feature of an embodiment of the present invention, the implant further comprises a deployment rod inserted via an opening in a proximal end of the implant and engaging a distal one of the first and second portions of the base such that a force applied to one of the proximal and distal ends of the implant can be opposed by tension applied to the deployment rod, thereby causing movement of the base from the initial length towards the second length.

According to a further feature of an embodiment of the present invention, the first contact surface and the second contact surface are each partial surfaces having one or more openings totaling at least a quarter of a total area of a contact surface footprint.

According to a further feature of an embodiment of the present invention, the relative motion of the second contact surface relative to the first contact surface includes a change of a distance separating between the first and second contact surfaces.

According to a further feature of an embodiment of the present invention, the teeth are ratchet teeth.

According to a further feature of an embodiment of the present invention, the ratchet teeth are sequentially arranged to support movement of the base through a continuous range of lengths.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIGS. 1A-1C are isometric views of an implant, constructed and operative according to an embodiment of the present invention, with an adjustable angle between two tissue contact surfaces, the implant being shown in a minimum-angle, an increased-angle and a maximum-angle state, respectively; FIGS. 2A-2C are isometric views similar to FIGS. 1A-1C, respectively, cut-away along a center-plane of the implant;

FIG. 3A is an isometric exploded view illustrating the components of the implant of FIG. 1A;

FIG. 3B is an enlarged view of the region of FIG. 3 A designated III;

FIG. 4A is a side view of the implant of FIG. IB showing the implant in a partially raised state engaged by a deployment rod with an integrated ratchet release element effective to release locking of a ratchet configuration;

FIG. 4B is a view similar to FIG. 4A during removal of the deployment rod, and showing the ratchet configuration engaged;

FIGS. 5A and 5B are central-plane cross-sectional views taken through FIGS. 4A and 4B, respectively;

FIG. 6A is an isometric view illustrating the implant of FIG. 1A attached to a delivery system;

FIG. 6B is an enlarged view of the region of FIG. 6A designated VI;

FIG. 7A is a center-plane cross-sectional view taken through the delivery system as illustrated in FIG. 6A;

FIG. 7B is an enlarged view of the region of FIG. 7 A designated VII;

FIG. 7C is an enlarged view of the region of FIG. 7A designated VIII; FIG. 8A is an isometric view of a variant of the implant of FIG. 1 A-1C employing a keyhole slot for engagement of a deployment rod;

FIG. 8B is an enlargement of a region of FIG. 8A designated IX;

FIG. 8C is an isometric view of a deployment rod for use with the implant of FIG. 8A including a keyhole slot engagement configuration and a cam-type ratchet mechanism release feature;

FIGS. 9A-9C are central-plane cross-sectional views taken through the implant of FIG. 8 A showing the deployment rod in a pre-engagement state, an engaged ratchet-release state and an engaged ratchet-engaged state, respectively;

FIGS. 1 OA- IOC are cross-sectional views taken along the plane X shown in FIGS. 9A-9C, respectively; FIG. 11A is an isometric view illustrating an implant, constructed and operative according to an embodiment of the present invention, with an adjustable distance between two tissue contact surfaces in a minimum separation state attached to a delivery system;

FIG. 1 IB is an enlarged view of the region of FIG. 11 A designated XI;

FIG. llC is an isometric view similar to FIG. 11B, cut-away along a center-plane of the implant;

FIG. 12A is an isometric view similar to FIG. 11B showing an implant in a maximum separation state;

FIG. 12B is an isometric view similar to FIG. 12A, cut-away along a center-plane of the implant;

FIG. 13A is an isometric view illustrating a schematic representation of an expanding cage implant in a raised state engaged by a deployment rod with an integrated ratchet release element effective to release locking of a ratchet configuration;

FIG. 13B is an isometric view similar to FIG. 13 A, cut-away along a center-plane of the implant;

FIG. 13C is a side view illustrating a schematic representation of an expanding cage implant in a raised state engaged by a deployment rod with an integrated ratchet release element effective to release locking of a ratchet configuration;

FIGS. 14A and 14B are additional isometric views corresponding to FIG. 13A taken from above the implant;

FIGS. 15A, 16A and 17A are isometric views of an implant, constructed and operative according to an embodiment of the present invention, with an adjustable distance between two tissue contact surfaces with a locking configuration transverse to the direction of expansion, in a minimum separation state and free state, increased separation and free state, and increased separation and clamped state, respectively;

FIGS. 15B, 16B and 17B are isometric views corresponding to FIGS. 15 A, 16A and 17 A, respectively, taken from below the implant; FIGS. 15C, 16C and 17C are bottom views corresponding to FIGS. 15B, 16B and 17B, respectively;

FIG. 18 is an isometric exploded view illustrating the components of the implant of FIGS. 15A-17C;

FIGS. 19A-19C are center-plane cross-sectional views corresponding to

FIGS. 15A, 16A and 17A, respectively;

FIGS. 20A-20C are central-plane cross-sectional views taken through the implants of FIGS. 19A-19C, respectively, showing the deployment rod actuation of a minimum separation state and free state, increased separation and free state, and increased separation and clamped state, respectively;

FIG. 21 A is an isometric view of an implant, constructed and operative according to an embodiment of the present invention, with an adjustable distance between two tissue contact surfaces in an increased separation state and free state;

FIG. 21 B is an isometric view corresponding to FIG. 21 A;

FIG. 21C is a top view corresponding to FIG. 2 IB.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is an adjustable orthopedic implant with a mechanism to maintain an adjusted state, and preferably also including a release mechanism. The family of implants is exemplified herein with reference to an implant with an adjustable angle between two tissue contact surfaces, but is equally applicable to various expanding cage implants. Although the exemplary embodiments in the description and appended claims are in regard to an implant for insertion between two regions of tissue, the implants exemplified herein are also suitable for various medical procedures, including, but not limited to, procedures for treating vertebral compression fractures and corpectomy procedures. The principles and operation of implants according to the present invention may be better understood with reference to the drawings and the accompanying description.

Referring now to the drawings, FIGS. 1A-21C illustrate various embodiments of an implant, constructed and operative according to the teachings of an embodiment of the present invention.

Overview

Referring collectively to the embodiments depicted in FIGS. 1A-10C, there is shown an implant, for insertion between two regions of tissue, having a base 12 having a first contact surface 14 for contacting a first region of tissue. Base 12 includes a first portion 16 displaceable relative to a second portion 18 so that base 12 assuming an initial length, and is shortened towards a second length when first portion 16 is displaced towards second portion 18. A hinged element 20, having a second contact surface 22 for contacting a second region of tissue, is interconnected with first portion 16 of base 12 at an effective hinge 24. A linking segment 26 is hingedly connected to both second portion 18 of base 12 at a hinge 28 and to hinged element 20 at a hinge 30.

The structure and deployment of linking segment 26 is such that shortening of base 12 from its initial length towards its second length causes the linking segment to push a region of hinged element 20 away from base 12, thereby changing an angle of second contact surface 22 relative to first contact surface 14. Although the exemplary embodiments described herein discuss the movement of hinged element 20 away from base 12 via the shortening of base 12, the geometries of the devices described herein may be altered such that lengthening of the base 12 achieves the desired displacement of hinged element 20.

Referring collectively to the embodiments depicted in FIGS. 11A-21C, there is shown an implant device with a linking segment 26 at both ends of the implant. Each device is conceptually similar to the implants depicted in FIGS. 11A-21C. The structure and deployment of linking segments 26 is such that shortening of base 12 from its initial length towards its second length causes the linking segments to push hinged element 20 away from base 12 so as to achieve an overall lifting effect, thereby increasing a distance of second contact surface 22 relative to first contact surface 14. As such, the relative motion of hinged element 20 and base 12 is primarily parallel, or has a significant parallel component In the embodiments depicted in FIGS. 11A-31B, there is an additional linkage 27 linking base 12 and hinged element 20. Linkage 27 is hingedly connected to both first portion 16 of base 12 at a hinge 29 and to hinged element 20 at hinge 30. Additional linkage 27 therefore provides additional stability of the parallel component. In the embodiments depicted in FIGS. 15A-21C, the stability of the parallel component is maintained by the addition of an interlocking flex joint 31 between linkages 26.

The shortening of base 12 is referred to hereinafter as the actuation of the device. In most cases, after actuation, it is desired to maintain an adjusted state of the implant, typically at or near the final raised state which the implant achieved during adjustment This is referred to herein as "locking". It should be noted that in cases where implant is in an increased separation or increased angle state, locking opposes the lengthening of base 12 but allows for the continued shortening of base 12. In the embodiments depicted in FIGS. 15A- 21C, there is a two-way locked state which opposes both the lengthening of base 12 and further shortening of base 12.

The locking mechanisms used to implement the present invention employs a ratchet configuration to maintain a desired deployed state of the device. Specifically, first portion 16 and second portion 18 are preferably formed with complementary features defining a ratchet configuration. The complementary features as illustrated here include a plurality of ratchet teeth 42 associated with proximal portion 16 and a resiliency biased detent 44 associate with distal portion 18. The ratchet configuration is deployed to allow shortening of base 12 from its initial length through a range of lengths, and to oppose lengthening of the base. It is preferred that ratchet teeth 42 are arranged in a sequential series to allow the shortening of base 12 from its initial length through a continuous range of lengths.

The terms "proximal" and "distal" are used in their normal senses to relate to the portions of the device closer and further, respectively, from the medical practitioner during deployment of the device. In many of the exemplary embodiments, first portion 16 corresponds to the proximal portion and second portion 18 corresponds to the distal portion. This correspondence, however, is exemplary and should not be considered limiting. Reversed configurations also clearly fall within the scope of the present invention.

Although hinged element 20 as shown in FIGS. 1A-21C is of substantially minimal geometric curvature along the dimension linking proximal and distal portions, hinged element 20 may also be of alternate curvature and shape, such as arcuate or the like.

Use of a ratchet configuration is particularly advantageous in certain embodiments in that it allows unrestricted adjustment of the implant angle during deployment, while ensuring that the deployed angle is maintained very close to the maximum angle after the deployment system is released. The spacing of the ratchet teeth defines the distance between locking positions, defining at least one, and preferably at least three, and more preferably at least six, sequential states in which the implant locks. In some cases, ten or more teeth may be used to achieve a quasi-continuous range of locking positions.

Particularly preferred implementations as illustrated herein employ a pair of ratchet arrangements deployed bilaterally, with a row of ratchet teeth 42 running along each side of a forked first portion 16, and a corresponding pair of spaced-apart biased detents 44 on second portion 18, as best seen in FIG. 3A. This provides enhanced stability and rigidity to the deployed implant

It should be noted that the ratchet configuration may be implemented in any orientation, and may arbitrarily be reversed between the proximal and distal portions. Thus, the series of ratchet teeth may be implemented as part of proximal portion 16, and may face "upwards" towards hinged element 20, "downwards" towards contact surface 14, inwards towards the internal space of the implant, or outwards.

The two-way locking and unlocking mechanism used to implement embodiments of the present invention employ a locking configuration to maintain a desired deployed state of the device. Specifically, first portion 16 and second portion 18 are preferably formed with complementary features defining a locking configuration. The complementary features as illustrated here include a series of teeth 42 associated with proximal portion 16, resiliency biased detents 44 associated with distal portion 18, and a clamping nut 45 positioned between detents 44. The locking configuration is deployed to allow shortening and lengthening of base 12 from its initial length through a range of lengths when in a free state, and to oppose shortening and lengthening of base 12 when in a clamped state. By way of one non-limiting example, FIGS. 15A- 21C illustrate an expanding cage implant which employs a locking configuration using inward-facing, or transverse, teeth 42. It is most preferred that teeth 42 are ratchet teeth 42 for providing additional control during actuation. Particularly preferred implementations as illustrated herein employ a pair of ratchet arrangements deployed bilaterally, with a row of ratchet teeth 42 running along each side of a forked first portion 16, and a corresponding pair of spaced-apart biased detents 44 on second portion 18, as best seen in FIG. 18. This provides enhanced stability and rigidity to the deployed implant.

As with all medical implants, it may in certain cases be desired to reposition or remove an implant, either during the deployment process or at a later date. Optionally, the rear surfaces of ratchet teeth 42 may have a relatively steep rise surface but may avoid full locking that would be achieved by an upright or undercut surface. This case would allow the locking to be overcome by application of sufficient outward force to overcome the reverse resistance of the ratchet configuration. More preferably, however, the present invention provides a ratchet release mechanism and a two-way locking and unlocking mechanism which facilitate reversal of the deployment without requiring application of large forces, as will be described. At this stage, it will already be appreciated that the present invention provides a highly advantageous solution for adjusting the angular relation and spacing between tissue surfaces. In a first particularly preferred set of implementations and corresponding applications, the device is deployed in an intervertebral space and actuated to restore a desired degree of lordosis. In other applications, the device may be oriented to allow adjustment of a lateral misalignment between vertebrae, such as for correction of a scoliosis misalignment. The device preferably provides a continuous, or near continuous, range of adjustment, typically spanning a range (from minimum angle to maximum angle) of at least 10 degrees. In some implementations, adjustments reaching angles in excess of 30 degrees may be provided. These and other features of the invention will become clearer from the following description and with reference to the accompanying drawings.

It should be appreciated that several of the exemplary embodiments of the present invention described below are closely analogous to each other in structure and function. For conciseness of presentation, features described in the context of one embodiment will not be described again in the context of another embodiment, and should be understood to apply equally to all embodiments unless explicitly stated or clearly evident to the contrary. For example, various forms of deployment and corresponding methods described and an exemplary delivery system described with reference to FIGS. 6A-7C, are not limited to the details of the implant embodiments with which they are illustrated, and should be understood to be applicable to all embodiments of the present invention disclosed herein, with any minor adaptations that would be required, as will be clear to a person ordinarily skilled in the art.

Definitions

Before addressing the features of the invention in more detail, it will be helpful to define certain terminology as used herein in the description and claims. Where reference is made to various elements, such as base 12, hinged element 20 and linking segment or segments 26, it should be appreciated that each element may in fact be made up of various subcomponents, rigidly or flexibly interconnected. With the exception of first and second portions 16, 18 of base 12 which are explicitly referred to as being relatively movable, other subdivisions of the above components into subcomponents are most preferably rigidly interconnected such that they function mechanically as a single component.

Reference is made to various "contact surfaces" for contacting tissue, and to angles formed between such contact surfaces. As will be clear from the various embodiments shown herein, the contact surfaces are typically not smooth surfaces, but rather are formed with various textures and/or tissue engaging features which facilitate anchoring of the device against the adjacent tissue surfaces, typically bone. Furthermore, the overall profile of the contact surface may have a curvature, such as a convex curvature to engage a corresponding concavity, for example, in a lumbar vertebral endplate. In all such cases, a plane of the contact surface for the purpose of defining angles thereto is defined by a best-fit plane over the entire contact surface, for example by minimizing a least-squares misfit, neglecting localized projecting features. When reference is made to contact surface 14 of base 12, this includes the parts of both first and second portions 16 and 18 that are disposed to contact adjacent tissue, but excludes relatively recessed intermediate portions which are not typically expected to come in contact with adjacent tissue.

The angle between two contact surfaces is defined herein in the description and claims as the angle formed between the planes of the two contact surfaces when extrapolated to intersect, typically beyond the body of the implant. In a state in which the two contact surface planes are parallel, the angle between them is defined as zero. Where the end of hinged element 20 furthest from effective hinge 24 is initially closer to base 12 than the other end of hinged element 20 the angle is defined as negative.

The distance between two contact surfaces is defined herein in the description and claims as the maximum distance between the two contact surfaces. As also clear from the various examples, the contact surfaces are typically not full surfaces but rather have various openings (apertures or spaces) which may be either enclosed or open-sided. In fact, in certain preferred implementations such as for spinal fusion, it is particularly preferred that the contact surface are partial surfaces having one or more openings totaling at least a quarter, and most preferably at least half, of a total area of a contact surface footprint. The "contact surface footprint" for this purpose is taken to be the region enclosed by the shortest line in the contact surface plane encompassing (the projections of) all parts of the contact surface.

Where reference is made to a length of the contact surface, this refers to the largest dimension of the contact surface footprint. Where reference is made to the length of linking segment 26, this refers to a dimension of the linking segment between axes 28, 30 of its hinged interconnection with base 12 and hinged element 20.

Where reference is made to an "effective hinge" or "hinged interconnection", this refers to both hinge joints, pivotal linkages and integral hinges which provide an effect similar to a single hinge over the relevant range of angular motion. It is a particular feature of certain preferred embodiments of the present invention that overall geometry of the axes, or effective axes, 24, 28 and 30 remains effectively a rigid triangular form with one variable-length side which generates the required change in form, although a linkage or integral joint which defines an effective axis which lies outside the body of the implant and/or which moves somewhat during the adjustment also falls within the scope of this definition.

It should be noted that any and all references to particular orientations of the devices of the present invention, to anatomical directions, or to motion of one component relative to another, are used merely for clarity of presentation, and do not limit the scope of the invention as claimed unless explicitly stated to the contrary. The devices may be used in any orientation including, for example, with "base 12" uppermost, and motion of first portion 16 towards second portion 18 typically refers to relative motion which may be achieved by moving either or both of the components in question.

Geometrical Configurations

As mentioned above, a wide range of implementations of the present invention may essentially be viewed as a rigid triangular configuration defined by the positions of axes, or effective axes, 24, 28 and 30, wherein shortening of one side of the triangle, corresponding to at least part of base 12, causes a change in angle of hinged element 20, associated with one of the other sides of the triangle, relative to the base. Within this general definition, the specific positions of the axes, relative sizes of the sides, and geometrical forms of the contact surfaces relative to the underlying triangle, may all vary considerably according to the intended application, the required range of angles, the expected loading, the available deployment forces, and the properties of the materials to be used. It should also be apparent mat in certain preferred embodiments, there is an alternate quadrilateral geometry, wherein shortening one side of the quadrilateral, corresponding to at least part of base 12, causes a change in the separation distance of hinged element 20 from base 12. It should also be apparent that in certain preferred embodiments, there is a triangular geometry wherein shortening of one side of the triangle, corresponding to at least part of base 12, causes a change in the separation distance of hinged element 20 relative to base 12. A partial set of examples of possible geometries is presented in the examples described herein.

In one subset of implementations the contact surface length of hinged element 20 is at least 40% longer than the linking segment length of element 26, and in many cases 100% longer, i.e., where the contact surface length is at least twice the linking segment length. This ratio reflects the fact that hinged element 20 performs a function of supporting tissue whereas linking segment 26 provides only an internal mechanical support function, leading to asymmetry between elements 20 and 26. Furthermore, in a range of applications, it may be preferable that a "fully raised" state of linking segment 26, corresponding to the fully shortened state of base 12, has the axis-to-axis direction of linking segment 26 deployed at a steep angle, typically in excess of 70 degrees, to a plane of base 12.

The contact surface length of hinged element 20 is also typically at least 80% of the minimum length of base 12, and in various cases, at least equal to the minimum length of base 12.

A further parameter which may vary between implementations is the position of hinged connection 30 along hinged element 20. In certain implementations, hinged connection 30 is located closely adjacent to (i.e., within 10% of the contact surface length from) the end of hinged element 20 furthest from effective hinge 24. In various cases, it may be advantageous to place hinged connection 30 closer to effective hinge 24, thereby typically achieving an increased range of angular adjustment for a given adjustment of the length of base 12. For this reason, a preferred position of hinged connection 30 for certain implementations of the present invention is specifically distanced from the end of hinged element 20 by at least 10% of the contact surface length.

By way of example, in a preferred but non-limiting example of an implant 100 illustrated with reference to FIGS. 14A-18B, hinged connection 30 is located between 10% and 30% of the contact surface length from the end.

The latter options (particularly implants 200 and 300) facilitate achieving a greater distance between first and second contact surface 14 and 22 by an overall lifting effect of hinged element 20. The increased distance subjects the components to significantly greater mechanical stress than the earlier embodiments, therefore requiring use of strong mechanical materials and/or more robust structural design. A typical, non-limiting example of material suitable for manufacturing various embodiments of the present invention, including such high-stress implants, is titanium. An additional material more suited for the lower-stress implementations is a biocompatible structural polymer, such as PEEK. Actuation Mechanisms and Locking Mechanisms

Angular adjustment of the implants of the present invention is preferably achieved by shortening base 12, i.e., by bringing first portion 16 and second portion 18 towards each other, referred to herein as "actuation". In most cases, after actuation, it is desired to maintain an angled state of the implant, typically at or near the final raised state which the implant achieved during adjustment. The functions of actuation and locking may be performed by a single combined mechanism, or by separate mechanisms dedicated to each function, and such mechanisms may be either integrated into the implant structure or may be separate structures which are deployable within the implant prior to use and/or removable from the implant after use, as appropriate.

By way of one non-limiting example of a combined, integrated actuation and locking mechanism, a threaded actuator (not shown) may be deployed so as to link first and second portions 16, 18 so that rotation of an actuator bolt, or of a tightening nut, is effective to apply force to bring the two portions together, thereby shortening base 12. A threaded actuator with a suitably chosen thread pitch also achieves frictional locking, thereby maintaining any desired final angle of the device.

In a particularly preferred but non-limiting set of implementations, a removable actuating mechanism is employed, most preferably integrated with a delivery system for positioning the implant within a body. An example of such a system is illustrated in FIGS. 6A-7C.

A preferred principle of operation for a removable actuation system employs a deployment rod 32 (FIGS. 4A-5B and 7A-7C) which is inserted via an opening 34 in a proximal end of the implant, here corresponding to first portion 16, and engages a distal portion, here corresponding to second portion 18. As a result of this engagement, a force applied to a proximal end of the implant, in this case first portion 16, in a distal direction can be opposed by a counterforce applied via deployment rod 32 to second portion 18, thereby causing shortening of base 12. In an alternate principle of operation, as a result of the engagement of deployment rod 32 with a distal portion corresponding to second portion 18, a force applied to a distal end in a proximal direction can be opposed by a counterforce applied via deployment rod 32 first portion 16, thereby causing shortening of base 12.

Engagement of a tip of deployment rod 32 with distal portion 18 may be by any suitable arrangement, such as via threaded engagement 36, as illustrated in FIG. 5A, or by a pin 38 and keyhole-slot 40 arrangement, as illustrated in FIGS. 8A-8C. Application of actuating force is preferably achieved by use of an actuator mechanism built into a handle of a delivery system, such as that of FIGS. 6A-7C, which allows continuous and controllable adjustment of the relative displacement of first and second portions 16, 18. After completion of the actuation, deployment rod 32 is preferably disengaged from second portion 18 and the deployment system is removed. The removable actuator structure is of particular value in interbody fusion applications, where the remaining inner volume of the implant is preferably contiguous with the aforementioned openings in the tissue contact surfaces to provide a through-channel for formation of a bone bridge between the vertebral endplates. Proximal opening 34 also allows for introduction and/or topping up of a filler material, such as natural or processed bone chips, medicaments and/or other fillers.

A non-limiting example of a delivery system, generally designated 60, is illustrated in FIGS. 6A-7C. The delivery system preferably includes a forked gripping mechanism including a pair of jaws 62 with complementary engagement features configured to engage lateral gripping regions 64 of the implant (visible in FIG. 1A). Jaws 62 are tightened against and released from engagement with implant 100 by advancing or retracting an outer sleeve 66 by rotation of a threaded collar 68.

Adjustment of the angle of contact surfaces of the implant is achieved by relative motion of jaws 62 pushing distally on first portion 16 while a counterforce is applied to second portion 18 via deployment rod 32. An exemplary mechanism for generating these forces is illustrated in FIGS. 7A and 7C. In the example shown here, rotation of a handle 70 causes rotation of an insert 72 which is locked against axial motion relative to an outer housing 74, but is free to rotate. Insert 72 terminates at an internally threaded collar 76 which is engaged with a displacer element 78 which is mechanically restricted to axial motion within housing 74. Displacer element 78 engages an actuator sleeve 80 which is mechanically linked to outer sleeve 66 and jaws 62. Deployment rod 32 passes through the center of this entire assembly, and is fixed against axial displacement relative to housing 74 by a clamping element 82 which engages with a peripheral recess 84 in rod 32. As a result of this structure, rotation of handle 70 is effective to advance displacer element 78 relative to deployment rod 32, thereby applying the required forces via actuator sleeve 80 and jaws 62 to push proximal portion 16 towards distal portion 18 which is held by deployment rod 32. Preferably, an angle indicator 86 is associated with displacer element 78 so as to move relative to angle markings provided on housing 74, thereby indicating to a medical practitioner the angle currently reached by the contact surfaces of the implant.

Use of a removable actuation system typically requires provision of a separate locking mechanism. As mentioned above, the locking mechanism of the present invention is a ratchet configuration to maintain a desired deployed state of the device.

Ratchet Release Mechanism

By way of introduction, although described herein in the context of an adjustable angle implants and expanding cage implants, the ratchet and ratchet release mechanism described herein are applicable broadly to any adjustable implant in which adjustment is achieved by relative motion between two components which should normally be maintained at the displaced positions they reach at the end of the adjustment, but which must on occasion be released in order to readjust, reposition or remove the implant.

One particularly preferred but non-limiting example of a ratchet release mechanism is illustrated in FIGS. 3A and 3B. In order to facilitate release of the ratchet arrangement, and particularly in this case, simultaneous release of the bilateral pair of ratchet configurations, a crossbar 46 is mechanically linked to detents 44 so that upward displacement of crossbar 46 (in the orientation illustrated here) is effective to flex the resilient support structure and raise detents 44 out of engagement with ratchet teeth 42.

Disengagement of the ratchet configuration can thus be achieved by insertion of a suitably formed ratchet release element via proximal opening 34 so as to bear against crossbar 46 and release engagement of detents 44 with ratchet teeth 42, thereby allowing lengthening of base 12. In a particularly preferred set of implementations, in order to facilitate reversal of deployment when needed during the deployment process, this "ratchet release element" is integrated as part of deployment rod 32.

According to this approach, an engagement of deployment rod 32 with the distal portion of base 12, in this case, second portion 18, is configured to allow a first motion of the deployment rod while maintaining engagement of deployment rod 32 with the distal portion. Deployment rod 32 is provided with at least one feature deployed such that this first motion is effective to bring the at least one feature to bear on crossbar 46, thereby releasing engagement of detent(s) 44 with the ratchet teeth 42 to allow lengthening of the base.

A first implementation of these features is further illustrated in FIGS.

4A-5B. Specifically, the threaded engagement 36 between deployment rod 32 and second portion 18 allows a range of axial positions, depending upon the number of axial rotations of deployment rod 32 used to engage the threaded engagement. Deployment rod 32 here features an outward step 48 which is positioned such that, in a first axial position (FIG. 5A), when fully engaged with the threaded engagement 36, outward step 48 bears against crossbar 46, flexing it "upwards" as shown, thereby disengaging detents 44 from ratchet teeth 42 as shown in FIG. 4A. In a second axial position (FIG. 5B), when deployment rod 32 is engaged along only part of threaded engagement 36, outward step 48 is sufficiently withdrawn along the axis of the rod that crossbar 46 has returned to its unstressed state, and detents 44 are engaged with ratchet teeth 42 (FIG. 4B) to maintain the deployed state of the implant.

An alternative implementation is illustrated in FIGS. 8 A- 10C in which engagement between deployment rod 32 and distal (second) portion 18 is achieved through lateral pin 38 engaging a bayonet slot with a keyhole opening 40. As best seen in FIGS. 10A-10C, deployment rod 32 here assumes a first position with pin 38 upwards (FIG. 10A) in which the rod can be freely inserted and removed via keyhole opening 40, a first rotated position (FIG. 10B), rotated anticlockwise 90 degrees, in which pin 38 is already locked within the bayonet slot, and a second rotated position (FIG. 10C), rotated 180 degrees anticlockwise. As best seen in FIG. 8C, a region of deployment rod 32 positioned to come into alignment with crossbar 46 is provided with an eccentric cam surface 50, shown in this example with its maximum radius roughly opposite pin 38. As a result of this structure, rotation of deployment rod 32 from its first rotated position to its second rotated position is effective to bring cam surface 50 to bear on crossbar 46, thereby lifting detents 44 out of engagement with ratchet teeth 42.

Optionally, normal insertion of the implants of the present invention may be performed with the ratchet arrangement engaged, thereby achieving immediate, step-wise retention and stabilization of the implant during the adjustment process. In this case, the ratchet arrangement may provide audible and/or tactile feedback during the adjustment process which may be helpful to the medical practitioner. Further motion of deployment rod in order to release the ratchet mechanism would then only be performed in the event that readjusting, repositioning or removal of the implant becomes necessary.

Alternatively, the ratchet-release state may be used as the default state during deployment. In all cases, reengagement of the ratchet preferably occurs as part of the disengagement process, and prior to complete disengagement of deployment rod 32 from the distal portion, thereby helping to ensure that any forces acting on the implant do not disturb the intended adjusted state of the implant. As mentioned before, the ratchet and ratchet release features of the present invention are relevant to a wide range of adjustable implants, including expanding cage implants in which the relative motion of the displaceable element 20 and base 12 is primarily parallel, or has a significant parallel component. Examples of such implants are illustrated in FIGS. 1 1A-21C, where each device is conceptually similar to the implants described above, but has a linking segment 26 at both ends of the implant so as to achieve an overall lifting effect, thereby increasing a distance of second contact surface 22 relative to first contact surface 14. In all other respects, the structure and function of these expanding cage embodiments will be fully understood by analogy with the similarly labeled components of the variable angle implants described herein.

Two- Way Locking and Unlocking Mechanism

As mentioned before, the series of ratchet teeth may be implemented as part of proximal portion 16, and may face "upwards" towards hinged element 20, "downwards" towards contact surface 14, inwards towards the internal space of the implant, or outwards.

One particularly preferred but non-limiting example of a combined, integrated actuation, two-way locking and unlocking mechanism is illustrated in FIGS. 15A-20C. In the example shown here, ratchet teeth 42 are transverse, facing inwards towards the internal space of the implant device. In order to facilitate the two-way locking and unlocking of the ratchet teeth 42 and detents 44, flexible detents 44 are positioned at the ends of tapered arms 47. Arms 47 are tapered away from detents 44 such that detents 44 are disengaged from ratchet teeth 42. The portions of arms 47 facing inward towards the internal space of the implant device are threaded with a threading 43. A threaded two- way clamping nut 45 with complementary threading to threading 43 is positioned between detents 44, and is movable between the distal end of the implant and detents 44 along threading 43 by clockwise and anticlockwise rotation. In the example shown in FIGS. 15A-20C, threading 43 is female and clamping nut 45 has male threading. A preferred principle of operation for a removable actuation system employs a deployment rod 32 which is inserted via opening 34 in a proximal end of the implant, here corresponding to first portion 16, and engages a distal portion, here corresponding to second portion 18 (FIGS. 20A-20C). As previously described, as a result of this engagement, a force applied to a proximal end of the implant, in this case first portion 16, in a distal direction can be opposed by a counterforce applied via deployment rod 32 to second portion 18, thereby causing shortening of base 12. In an alternate principle of operation, as a result of the engagement of deployment rod 32 with a distal portion corresponding to second portion 18, a force applied to a distal end in a proximal direction can be opposed by a counterforce applied via deployment rod 32 first portion 16, thereby causing shortening of base 12.

In the example shown here, clamping nut 45 has a hexagonal aperture (FIG. 18) for fitting a hexagonally shaped rod. As previously described, engagement of a tip of deployment rod 32 with distal portion 18 may be by a pin 38 and keyhole-slot 40 arrangement in distal portion 18. In the example shown here, deployment rod 32 is hexagonally shaped and hollow with a central rod 33 freely rotatable within hexagonally shaped rod 32. As such, pin 38 is attached to the end of central rod 33 and is configured to engage keyhole- slot 40.

As previously described, application of actuating force is preferably achieved by use of a mechanism built into a handle of a delivery system, such as that of FIGS. 6A-7C and 11A-11C. The state in which detents 44 are disengaged from ratchet teeth 42 is referred to as a "free state". Implant 300 being in the free state facilitates the unopposed shortening and lengthening of base 12. After completion of actuation, rotation of clamping nut 45 is used to facilitate the two-way locking of the clamping arrangement Rotation of clamping nut 45 by hexagonal rod 32 in a clockwise direction of rotation moves clamping nut 45 from a distal end towards a proximal end along threading 43. The movement of clamping nut 45 provides an outward force on detents 44 and causes detents 44 to engage ratchet teeth 42 (FIGS. 17A-17C). The positioning of clamping nut 45 prevents detents 44 from flexing further inward, thus preventing further shortening of base 12. The engagement of detents 44 with ratchet teeth 42 while be prevented from further flexing by clamping nut 45 is referred to as a "clamped state".

Disengagement of detents 44 from ratchet teeth 42 is achieved by insertion of hexagonal rod 32 via proximal opening 34 to return clamping nut 45 to distal portion 18 of base 12, thereby allowing further shortening and lengthening of base 12.

Re-positioning implant 300 to the free state is achieved by movement of clamping nut 45. Specifically, rotation of clamping nut 45 by hexagonal rod 32 in an anticlockwise direction of rotation moves clamping nut 45 from a proximal end towards a distal end along threading 43. The movement of clamping nut 45 subdues the outward force on detents 44 and causes detents 44 to retract out of engagement with ratchet teeth 42 (FIGS. 17A-17C), thereby allowing further shortening and lengthening of base 12.

Selective positioning of clamping nut 45 allows for implant 300 to achieve "locking" as previously described. Specifically, there is a point during movement of clamping nut 45 at which detents 44 engage ratchet teeth 42 to form the ratchet configuration without out being prevented from flexing further inward. This is of particular use when implant 300 is not actuated and detents 44 are partially engaged with ratchet teeth 42. As such, during actuation, detents 44 slide in and out of the spaces between ratchet teeth 42 providing more control of the actuation of implant 300. Moving clamping nut 45 towards the distal end acts as the ratchet release mechanism, changing the state of implant 300 from a locked state to a free state.

In an alternate configuration, it may be preferable to clearly define flexion points 49 in arms 47 at which the ratchet configuration is achieved, as shown in FIGS. 21A-21C. The delineation of flexion points 49 allows for more controlled ratchet functionality during actuation of the implant.

Although the implant description thus far has pertained to a locking configuration using a clamping nut 45 positioned between detents 44, other embodiments are possible in which alternate mechanical arrangements are used to alternate the configuration of the implant between a free state, a clamped state, and a ratchet configuration. Such mechanical arrangements include, but are not limited to, wedges, dowels, and cylindrical elements with apertures. It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.