Patent Description:
Intervertebral implants are commonly used in spinal surgery, such as in interbody fusion procedures, in which an implant (e.g., a spacer or cage) is placed in the disc space between two vertebrae to be fused together. At least a portion of the disc is typically removed before the implant is positioned in the intervertebral space, and the implant may be supplemented with bone graft material to promote fusion of the vertebrae. Interbody fusion procedures may also be performed in conjunction with other types of fixation, such as pedicle screw fixation, to provide additional stability, particularly while the vertebrae fuse together.

Different interbody fusion procedures can be distinguished by their location along the spine (e.g., in the cervical, thoracic, or lumbar regions); by the type of implant used; and by the surgical approach to the intervertebral space, in which different surgical approaches often imply different structural characteristics of the implant or implants used. Different surgical approaches to the spine include anterior, posterior, and lateral. Examples of interbody fusion techniques performed along a posterior approach include posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF). PLIF techniques typically include positioning two intervertebral implants into the intervertebral space along a posterior to anterior direction, with one implant being positioned towards the left side of the spine and one implant being positioned towards the right side of the spine. The implants used in such PLIF techniques typically have a straight shape, in that they extend along a central axis. TLIF techniques, by contrast, typically include positioning one intervertebral implant into the intervertebral space (often towards the anterior portion of the intervertebral space) from the posterior of the patient, but the spine is approached on one side from a more lateral position than in PLIF techniques. The implants used in such TLIF techniques are often curved, such that they have an overall kidney bean-like shape. Interbody fusion techniques performed along a lateral approach, on the other hand, often involve implants that are generally symmetric along their linear longitudinal axis (e.g., having a substantially rectangular or oval shape), but the implants are typically larger than those used in PLIF or TLIF techniques. That is, intervertebral implants used in lateral approaches often cover a substantial portion of the disc space.

Included among the different types of intervertebral implants are dynamic implants which, unlike static ones, have outer geometries that can be modified after the implant is inserted into the patient's body, such as within the intervertebral space. Examples of such dynamic intervertebral implants include those which can then be expanded in the superior-inferior direction, like those disclosed in <CIT> ("the '<NUM> Patent"), <CIT>, and in <CIT> (hereinafter "the '<NUM> Publication"). Such implants have an initially contracted configuration, so that they have a low profile in the superior-inferior direction to ease insertion into the intervertebral space, and then the implants are expandable after implantation so as to securely engage and stabilize the vertebrae on both sides of the intervertebral space. Other examples of dynamic implants are those which have a profile along the transverse plane that can be modified after insertion, such as the implant disclosed in <CIT> ("the '<NUM> Patent"). That implant has portions which can be re-oriented with respect to one another in the transverse plane (i.e., within the plane of the intervertebral disc space), such that the implant has a generally linear profile along the insertion axis during movement into the disc space, after which the portions can be reoriented to provide stability over a larger area of the disc space (e.g., by changing to the curved, kidney bean-like shape of a typical TLIF implant). In that manner, the implant may allow for a less invasive approach by minimizing the cross-sectional area of the implant during insertion, without sacrificing the footprint taken up by the implant once implanted.

Although considerable effort has been devoted in the art to optimization of such intervertebral systems and methods, still further improvement would be desirable.

According to the invention, there is provided a lumbar interbody fusion device as defined in claim <NUM> and in the corresponding dependent claims, there is provided a method of manufacturing an interbody device as defined in claim <NUM>, and there is provided a method of assembling an interbody device as defined in claim <NUM> and in the corresponding dependent claims.

The present disclosure relates to an implant or cage that has flexible
portions enabling reversible elastic transition between a linear profile and a curved or kidney bean-like shape on a plane corresponding to a transverse plane of a patient relative to an intended final position of the cage. The cage includes two body portions or wings connected by a bridge. The wings may have a round or oblong cross-section on the transverse plane and may be thicker on the transverse plane than the bridge. The relatively thin cross-section of the bridge on the transverse plane may enable flexure of the bridge corresponding to movement and reorientation of the wings relative to each other. The elastic flexibility of the bridge is
facilitated by a pattern of apertures perforating the bridge. A variety of patterns of apertures may contribute to the elastic flexibility of the bridge.

In another aspect, a lumbar interbody fusion device includes a first wing, a
second wing, and a bridge. The bridge may have an arcuate resting shape and include a first end connected to the first wing, a second end connected to the second wing, and at least one aperture extending through the bridge in a radial direction relative to the arcuate resting shape of the bridge. The bridge may be elastically deformable such that a distance between the first wing and the second wing may vary according to elastic deformation of the bridge.

In some arrangements according to any of the foregoing, a method of constructing the device includes additively manufacturing the device by stacking layers in an axial direction perpendicular to the radial direction.

In some arrangements according to any of the foregoing, the layers may be layers of titanium.

In some arrangements according to any of the foregoing, the first wing may have a V shaped recess that is concave toward the second wing and the second wing may have a V shaped projection that is convex toward the first wing, and the V shaped projection may extend into the V shaped recess when the bridge is in the resting shape.

In some arrangements according to any of the foregoing, the arcuate resting shape of the bridge may be centered on an axis extending perpendicular to the radial direction and extending from an inferior direction to a superior direction, and the wings are radially inward of the bridge.

In some arrangements according to any of the foregoing, the at least one aperture may be a plurality of slots extending across bridge from an inferior edge of the bridge and from a superior edge of the bridge to define a serpentine bar shape of the bridge.

In some arrangements according to any of the foregoing, a cavity may extend through the bridge between the first and the second end. The at least one aperture may include a spiral slot extending along the bridge between the first end and the second end. The spiral slot may provide an opening from the cavity to an exterior surface of the bridge.

In some arrangements according to any of the foregoing, the bridge may be a coil shaped element extending from the first end to the second end.

In some arrangements according to any of the foregoing, the axis may be perpendicular to a flexure plane. A width of the bridge may be defined parallel to the axis, and the width of the bridge may be greater than a radial thickness of the bridge on the flexure plane at every location between the first end and the second end.

In some arrangements according to any of the foregoing, flexure of the bridge perpendicular to its width may correspond to movement of the first wing and second wing along the flexure plane.

In another aspect according to any of the foregoing, a method of assembling an interbody device includes
positioning a first wing adjacent a second wing such that a fulcrum extending from the first wing extends along a fulcrum axis toward a socket included by the second wing. inserting the fulcrum into the socket, and rotating the first wing relative to the second wing such that the fulcrum turns within the socket about the fulcrum axis.

In some arrangements according to any of the foregoing, the fulcrum engages tabs partially enclosing the socket, thereby preventing withdrawal of the fulcrum from the socket along the fulcrum axis when the rotating step is completed.

In some arrangements according to any of the foregoing, the rotating step is completed when a first channel extends through the first wing is aligned with a second channel extending through the second wing.

In some arrangements according to any of the foregoing, the method includes a step of inserting a leaf spring through the aligned first channel and second channel.

In another aspect according to any of the foregoing, a lumbar interbody fusion device may comprise a first wing, a second wing. and an elastic biasing element maintaining the first wing and the second wing in contact with one another at a pivoting contact point. The first wing and the second wing may be freely separable from one another absent the biasing element.

In some arrangements according to any of the foregoing, the elastic biasing element may include a first end bearing on the first wing and a second end bearing on the second wing and being oriented to bias the first wing relative to the second wing about the pivoting contact point toward a rest position.

In some arrangements according to any of the foregoing, the biasing element may be a coil spring.

In some arrangements according to any of the foregoing, the biasing element may be a leaf spring.

In some arrangements according to any of the foregoing, the first wing may include a first outer facet and a first inner facet and may be movable about the pivoting contact point between a first position in which the first outer facet bears on the second wing and a second position in which the first inner facet bears on the second wing.

In some arrangements according to any of the foregoing, the first wing may define a vertex between the first inner facet and the first outer facet upon which the first wing rocks when rotating about the pivoting contact point.

When referring to specific directions and planes in the following disclosure, it should be understood that, as used herein, the term "proximal" means closer to the operator/surgeon, and the term "distal" means further away from the operator/surgeon. The term "anterior" means toward the front of the body or the face, and the term "posterior" means toward the back of the body. With respect to the longitudinal axis of the spine, the term "superior" refers to the direction towards the head, and the term "inferior" refers to the direction towards the pelvis and feet. The "transverse plane" is that plane which is orthogonal to the longitudinal axis of the spine. The "coronal plane" is a plane that runs from side to side of the body along the longitudinal axis of the spine and divides the body into anterior and posterior portions. The "sagittal plane" is a plane that runs along the longitudinal axis of the spine and defines a plane of symmetry that separates the left and right sides of the body from each other. Finally, the "medial" refers to a position or orientation toward the sagittal plane, and lateral refers to a position or orientation relatively further from the sagittal plane.

<FIG> illustrate a cage <NUM> according to an embodiment of the present disclosure. Cage <NUM> includes a distal wing <NUM> and a proximal wing <NUM> joined to each other by a flexible bridge <NUM>. Bridge <NUM> defines an arcuate shape having a generally constant radius relative to an axis (not pictured) along a length of bridge <NUM>, which axis extends generally in the superior-inferior direction in the implanted state of the cage <NUM>. The terms radial, axial, circumferential, and tangential as used throughout this disclosure will indicate directions relative to that superior-inferior axis about which the arc of bridge <NUM> extends.

Both wings <NUM>, <NUM> have similar roughly ovoid axial cross-sections. A radial gap <NUM> exists between wings <NUM>, <NUM> and bridge <NUM>, and wings <NUM> are separated by seam <NUM>. Radial gap <NUM> cooperates with the flexibility of bridge <NUM> such that bridge <NUM> acts as a living hinge and enables variation in a width of seam <NUM> and the radius of bridge <NUM>. Bridge <NUM> may be formed of any elastically flexible biocompatible material, meaning bridge <NUM> is internally biased toward a neutral radius or position. Example materials for the bridge <NUM> and the cage <NUM> as a whole include biocompatible polymers (e.g., polyether ether ketone (PEEK)), elastomeric materials, shape memory polymers, and shape memory metals (e.g., nitinol). In some arrangements, the neutral radius of bridge <NUM> results in a narrow seam <NUM> as shown in <FIG>. In other arrangements, the neutral radius of bridge <NUM> is smaller than shown in <FIG>, so bridge's <NUM> internal bias presses wings <NUM>, <NUM> into abutment.

Wings <NUM>, <NUM> include axial through holes <NUM>. Through holes <NUM> are illustrated as oblong in shape, but in other arrangements may be in other shapes. Such through holes <NUM> contribute to bone in-growth after cage <NUM> is implanted, and the though holes may be packed with bone growth promoting material (e.g., autologous and/or allogeneic bone graft, a bone growth enabling matrix, and/or bone growth stimulating substances). Axial surfaces of wings <NUM>, <NUM> include ridges <NUM> which prevent slippage of cage <NUM> and may further facilitate in-growth.

Bridge <NUM> meets distal wing <NUM> near a distal end <NUM> of cage <NUM> and meets proximal wing <NUM> near a proximal end <NUM> of cage <NUM>. Distal end <NUM> of cage <NUM> includes bevels <NUM> between a distal circumferential surface and the axial surfaces of cage <NUM>. Proximal end <NUM> includes a flat proximal surface <NUM> extending perpendicular to a longest dimension of cage <NUM>. An attachment structure may be provided at the proximal end <NUM> of the cage <NUM> for connection to a portion of a delivery tool (not shown) for inserting and positioning the cage <NUM> within the intervertebral space. The attachment structure may include a notch <NUM> cut into cage <NUM> at proximal end <NUM> and extending partially across flat proximal surface <NUM>. A pin <NUM> extending generally parallel to the axial direction may be positioned within the notch <NUM>. That pin <NUM> may be configured to be grasped by a portion of the delivery tool such that the cage <NUM> can be pivoted about the longitudinal axis of pin <NUM>. A suture may also be looped around pin <NUM> before delivery of cage <NUM>. The notch <NUM> and pin <NUM> together provide a hitch for the suture.

Elastic flexibility and durability of designs of bridge <NUM> consisting of a single, continuous strip of material may be limited, particularly where the implant is made of a relatively stiff or rigid material such as titanium. For example, such bridge designs may only flex only across a relatively small range or only a relatively small number of times before bridge <NUM> deforms permanently or fractures. Variations of bridge's <NUM> design may enable bridge <NUM> to elastically deform across a greater range or a greater number of times, which can be beneficial to various methods for delivering bridge. In one example, bridge <NUM> may be modified to include a number of apertures or openings extending radially therethrough. Certain such perforated designs of bridge <NUM> may have greater elastic flexibility than a solid bridge <NUM> of the same material.

<FIG> and <FIG> illustrate a cage <NUM> according to another arrangement. Cage <NUM> shares features in common with cage <NUM>, and like numerals indicate like elements except where stated otherwise. For example, cage <NUM> includes distal wing <NUM> and proximal wing <NUM> similar to distal wing <NUM> and proximal wing <NUM>, and through holes <NUM> and a radial gap <NUM> similar to through holes <NUM> and radial gap <NUM>, respectively, of cage <NUM>. Bridge <NUM> of cage <NUM> includes perforations <NUM> extending radially through bridge <NUM>. As illustrated, perforations <NUM> each have an oval shape with a longest dimension extending axially along bridge <NUM>. Perforations <NUM> are arranged in a staggered pattern of axially extending columns such that each whole perforation <NUM> (as opposed to partial length perforations <NUM> terminating on axial edges of bridge <NUM>) is axially centered on a space between two mutually axially adjacent perforations <NUM> in any radially adjacent columns. Perforations <NUM> alter flexibility characteristics of bridge <NUM>. Bridge <NUM> having perforations <NUM> as illustrated may be able to bend more easily or further without fracture than an unperforated bridge <NUM> constructed of the same material.

Cage <NUM>, or any other cage described in the present disclosure, may be additively manufactured. Examples of additive manufacturing processes for creating some or all of the components of cage <NUM>, or other cages disclosed herein, are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT> as well as <CIT>.

<FIG> shows a cage <NUM> having a bridge <NUM> that includes a pattern of interlocking right-angle hooks <NUM>. The pattern of interlocking hooks <NUM> facilitates reversible flexure of bridge <NUM> similarly to perforations <NUM>. The hooks <NUM> are provided by cuts extending radially through bridge <NUM>. The hooks <NUM> each include a series of linear components with right angle bends between the components. The hooks <NUM> branch outward from cross-points, and the right angle bends in each hook <NUM> are clockwise as the hook extends away from the respective cross-point. In other arrangements, however, hooks <NUM> may be provided by lines extending in directions having both circumferential and axial components.

The pattern of interlocking hooks <NUM> particularly facilitates localized flexibility of bridge <NUM>. For example, hooks <NUM> enable bridge <NUM> to deform at and around a contact point of an applied load while areas of bridge <NUM> further from the contact point exhibit little or no deformation from a rest position in response to the applied load.

<FIG> shows an arrangement of cage <NUM> with hooks <NUM> similar to hooks <NUM> illustrated in <FIG>. However, hooks <NUM> are provided by branching curved lines intersecting at approximately right angles. Hooks <NUM> similarly contribute to flexure of bridge <NUM>.

In the arrangement illustrated in <FIG>, bridge <NUM> is a helical coil extending circumferentially from distal wing <NUM> to proximal wing <NUM>. The helical coil shape is provided by helical void <NUM> bounding bridge <NUM>.

In the arrangement illustrated in <FIG>, bridge <NUM> includes several axial columns of shorter slots <NUM> extending axially across bridge <NUM>. Circumferentially adjacent columns of slots <NUM> are axially staggered relative to each other such that each whole slot <NUM> (as opposed to partial slots <NUM> terminating at axial edges of bridge <NUM>) is axially centered on a space between two mutually axially adjacent slots <NUM> in any radially adjacent columns. Bridge <NUM> is also longer relative to wings <NUM>, <NUM> and attaches to wings <NUM>, <NUM> further from seam <NUM> than the bridges shown above in <FIG>, further contributing to flexibility of cage <NUM>. However, it should be understood that the bridge length and attachments shown in <FIG> may be used in any of the other arrangements throughout the present disclosure, and the slots <NUM> may be applied to a bridge having the length and attachment locations shown in any of the other arrangements throughout the present disclosure.

<FIG> illustrates an arrangement of cage <NUM> with multiple differently-shaped through holes 736a, 736b, 736c extending radially through bridge <NUM>. Opposed arches 736a extend circumferentially parallel to axial edges of bridge <NUM> and curve axially toward each other. Arches nearly meet at an axial midpoint of bridge <NUM> that is circumferentially aligned with seam <NUM>, and a bridging connection <NUM> may connect the apexes of the arches 736a together. Wedges 736b fill much of two axial spaces between either circumferential sides of arches 736a, but each wedge <NUM> tapers inward to a point at its end closest to the seam <NUM>. Diamonds 736c fill four axial spaces between wedges 736b and arches 736a, but extend circumferentially beyond wedges 736b and arches 736a such that circumferential midpoints of diamonds 736c are approximately circumferentially aligned with ends of wedges 736b and arches 736a. The above described design of through holes 736a, 736b, 736c provides bridge <NUM> with flexibility and a relatively simple design. The relative simplicity of bridge <NUM> can result in a shorter production time for cage <NUM> depending on the chosen method of manufacture.

Bridge <NUM> of the arrangement shown in <FIG> and <FIG> includes a serpentine bar <NUM> defined between two rows of slots <NUM>, namely a superior row 836a and an inferior row 836b. The slots in the superior row 836a extend from the superior end 839a of the bridge towards the inferior end 839b but stop short of the inferior end 839b, and the slots in the inferior row 836b likewise extend from the inferior end 839b of the bridge towards the superior end 839a but stop short of the superior end 839a. In that manner, the slots 836a, 836b define curved sections 835a of the bar <NUM> connecting adjacent straight sections 835b of the bar, where successive curved sections 835a alternate between being positioned at the superior end 839a and the inferior end 839b of the bridge. The orientation of the superior and inferior directions relative to the distal end <NUM> and proximal end <NUM> described here is merely exemplary and may be reversed in other examples. Further, though the illustrated example shows the slots <NUM> extending proximally as they extend from the inferior end 839b to the superior end 839a, slots <NUM> according to other examples may extend proximally as they extend from the inferior end 839b to the proximal end 839a. The slots in both rows of slots 836a, 836b each extend along a direction that has both axial and circumferential components. For example, the slots 836a, 836b, and thus the intervening straight sections 835b of the bar <NUM>, may extend generally along a coronal plane of the body while oriented at a <NUM>° angle to the medial-lateral axis as illustrated. Though straight sections 835b of the illustrated arrangement extend at a <NUM>° relative to the medial-lateral axis, other angles may be suitable. Angles from <NUM>° to <NUM>° are explicitly contemplated. The slot 836b in each row of slots 836b that is circumferentially terminal in the direction of the row's circumferential component is shorter than the other slots 836b. In the illustrated example, the shorter slots 836b extend to an axial midpoint of bridge <NUM>. Each slot 836b ends in a circular node 836c having a greater diameter than a width of the slots 836b, further contributing to flexibility of bridge <NUM> and reducing stress concentration.

<FIG> illustrate a cage <NUM> with a bridge <NUM> provided by a coil 936a, similar to that described above with regard to <FIG>, with <FIG> being a sectional view along section line 9E of <FIG>, corresponding to an axial cross-section at an axial midpoint of cage <NUM>. Coil 936a is partially defined by spiral slot 936b extending circumferentially along bridge <NUM>. Both ends of slot 936b end in a circular node 936c on a radially outer surface of bridge <NUM>. Nodes 936c each have a greater diameter than a width of slot 936b. Coil 936a surrounds a circumferentially extending cavity <NUM> within bridge <NUM>. Axial surfaces of wings <NUM>, <NUM> at both the superior end and the inferior end of the cage <NUM> extend radially over radial gap <NUM> and bridge <NUM>, defining axial gaps <NUM> between overhanging portions of the superior and inferior surfaces and the bridge <NUM>. Both circumferential ends of radial gap <NUM> end in an approximately cylindrical axial column <NUM> having a greater diameter than a radial thickness of radial gap <NUM>.

Each wing <NUM>, <NUM> includes a radial port <NUM> extending from a radially interior surface of the respective wing <NUM>, <NUM> to a respective axial through hole <NUM>. An attachment structure may be provided at the proximal end <NUM> of the cage <NUM> for connection to a portion of a delivery tool (not shown) for inserting and positioning the cage <NUM> within the intervertebral space. For example, proximal wing <NUM> may include a threaded bore <NUM> at proximal end <NUM>, which threaded bore <NUM> may extend distally from a concavity <NUM> defined in the proximal end <NUM>. Seam <NUM> has a chevron shape with its peak oriented in a distal direction toward distal wing <NUM>. The chevron shape is provided by a "V" shaped recess 922a in distal wing <NUM> that is concave toward proximal wing <NUM> and a "V" shaped projection 922b on proximal wing <NUM> that is convex toward distal wing <NUM>. When cage <NUM> is in a resting shape, the "V" shaped 922b projection extends into the "V" shaped recess 922a, thereby defining seam's <NUM> chevron shape. The chevron shape of seam <NUM> allows portions of the cage <NUM> to be self-supporting, which enables additive manufacturing of cage <NUM> without the need for (or with only minimal) sacrificial support structures. For example, the chevron shape simplifies printing of cage <NUM> in a vertical orientation, such as the orientation of cage <NUM> shown in <FIG>. Further, the chevron seam <NUM> could be applied to other constructions of cage <NUM>. For example, any of the other arrangements of cages described above or below in the present disclosure may be constructed with a chevron seam similar to seam <NUM> as illustrated in <FIG>. Furthermore, in any arrangement, the chevron seam may be constructed with its peak pointed in the proximal or distal direction.

<FIG> illustrates an arrangement of cage <NUM> having an axial coil spring <NUM>, illustrated in <FIG>, connecting wings <NUM>, <NUM>, with proximal wing <NUM> illustrated as partially transparent to show coil spring <NUM> situated at a radially outer end of seam <NUM>. Wings <NUM>, <NUM> are not connected except by coil spring <NUM>. Absent coil spring <NUM>, wings <NUM>, <NUM> would therefore be freely separable. Circumferential faces of wings <NUM>, <NUM> that meet at seam <NUM> have reliefs <NUM> (e.g., chamfers or fillets) at respective radially outer edges, defining an outer facet or relief <NUM> and an inner facet <NUM> on each of the wings <NUM>, <NUM>. Reliefs <NUM> enable wings <NUM>, <NUM> to pivot relative to one another about coil spring <NUM> by allowing one wing to rock along the other such that a contact point between wings <NUM>, <NUM> moves radially outward from the inner facets <NUM> to the outer facets <NUM> as coil spring <NUM> is flexed. Ports <NUM> extend radially outward from through holes <NUM> to radially outer faces of wings <NUM>, <NUM>, so as to promote bone in-growth and/or dispersion of bone growth promoting material (e.g., autologous and/or allogeneic bone graft, a bone growth enabling matrix, and/or bone growth stimulating substances) out of the cage <NUM> through the ports <NUM>.

As shown in <FIG>, coil spring <NUM> includes two "L" shaped arms <NUM> extending tangentially from opposite ends of the coil and axially toward each other. <FIG> is an axial cross section at an axial midline of cage <NUM> with proximal wing <NUM> illustrated as partially transparent. <FIG> illustrates that coil spring <NUM> is disposed within arcuate channels <NUM> extending axially through wings <NUM>, <NUM> near relief <NUM>. Arms <NUM> extend into grooves <NUM> extending through wings <NUM>, <NUM> such that positions of wings <NUM>, <NUM> relative to one another correspond directly to a degree of flexure of coil spring <NUM>.

<FIG> illustrate a cage <NUM> with wings <NUM>, <NUM> having a leaf spring <NUM> for providing flexibility and/or shape memory properties, so that the wings <NUM>, <NUM> can be repositioned with respect to one another similarly to the other embodiments described above. Wings <NUM>, <NUM> similarly each include an inner facet <NUM> and outer facet or relief <NUM>, with a vertex defined therebetween upon which each wing rocks when rotated relative to the other about a pivot joint having a structure detailed below. <FIG> illustrates distal wing <NUM> as partially transparent, showing that leaf spring <NUM> is disposed along internal channels <NUM> extending along circumferentially outer faces of both wings <NUM>, <NUM>.

<FIG> shows wings <NUM>, <NUM> without leaf spring <NUM>. Distal wing <NUM> includes a rounded fulcrum <NUM> extending circumferentially toward proximal wing <NUM>, which includes a socket <NUM> for fulcrum <NUM> to pivot within. <FIG> illustrate how distal wing <NUM> and proximal wing <NUM> may be assembled. Distal wing <NUM> and proximal wing <NUM> are brought together such that fulcrum <NUM> approaches socket <NUM>, with distal wing <NUM> and proximal wing <NUM> about <NUM>° out of alignment. Fulcrum <NUM> extends from distal wing <NUM> along a fulcrum axis, and has a partially cylindrical or partially spherical shape having a thickness defined between two flat sides and corresponding to a radial direction relative to distal wing <NUM> and a diameter defined perpendicular to the thickness. Fulcrum <NUM> is inserted into socket <NUM>, and wings <NUM>, <NUM> are rotated into alignment. Alignment is achieved by rotation of wings <NUM>, <NUM> relative to one another such that fulcrum <NUM> turns within socket <NUM> about the fulcrum axis until channels <NUM> in wings <NUM>, <NUM> are aligned. Fulcrum <NUM> is keyed to socket <NUM> such that fulcrum <NUM> cannot be pulled free of socket <NUM> when wings <NUM>, <NUM> are in alignment. In the illustrated embodiment, keying of fulcrum <NUM> is achieved by tabs 1152a extending to partially enclose socket <NUM> such that an opening into socket <NUM> defined between tabs 1152a has a width in the axial direction that is less than the diameter of fulcrum <NUM> and a width in the radial direction that is greater than the diameter of fulcrum <NUM>. Fulcrum <NUM> is thereby insertable into socket <NUM> when distal wing <NUM> is rotated such that an axial direction relative to distal wing <NUM> is aligned with a radial direction relative to proximal wing <NUM>, but fulcrum <NUM> is not insertable into or removable from socket <NUM> when axial directions relative to both wings <NUM>, <NUM> are aligned. When wings <NUM>, <NUM> are aligned and fulcrum <NUM> is disposed within socket <NUM>, fulcrum <NUM> is engaged against interior surfaces of tabs 1152a to prevent withdrawal of fulcrum <NUM> along the fulcrum axis.

Wings <NUM>, <NUM> are unconnected except by keying fulcrum <NUM> into socket <NUM> and leaf spring <NUM>. Wings <NUM>, <NUM> would therefore become freely separable absent leaf spring <NUM> by rotating wings <NUM>, <NUM> relative to one another to un-key fulcrum <NUM> within socket <NUM>.

<FIG> are axial cross sections at an axial midline of cage <NUM>. As shown, leaf spring <NUM> is insertable through a slot <NUM> in proximal wing <NUM> located on a circumferentially outer side of proximal wing <NUM> near proximal end <NUM>. Leaf spring <NUM> deforms during passage through slot <NUM> and conforms to channels <NUM> upon full insertion. After assembly of cage <NUM> by insertion of leaf spring <NUM>, positions of wings <NUM>, <NUM> relative to one another correspond directly to a degree of flexure of leaf spring <NUM>. Rotation of wings <NUM>, <NUM> out of alignment as shown in <FIG> is impossible after leaf spring <NUM> is in place, so insertion of leaf spring <NUM> holds wings <NUM>, <NUM> together and prevents disassembly of cage <NUM>.

Referring now to <FIG>, there is depicted an exemplary method of deploying cage <NUM>, which may be a cage according to any of the above described arrangements, through an inserter tube <NUM> into disc space <NUM>. The inserter tube <NUM> may extend through an annulus fibrosus <NUM> of the disc between two vertebrae <NUM> of the spine <NUM> by performing an annulotomy through the annulus <NUM>. The through holes of cage <NUM> may be filled with morselized bone graft material prior to inserting cage <NUM> into inserter tube <NUM>. A suture <NUM> may be secured to cage <NUM>, for example by looping suture <NUM> around features such as pin <NUM> within notch <NUM> described with regard to <FIG>, or by threading suture <NUM> through a hitch provided by notch <NUM> and pin <NUM>, prior to insertion in inserter tube <NUM>. Suture <NUM> shown in <FIG> is disposed through a groove of a deployment shaft <NUM> (such as one of the bullnose instruments disclosed in the '<NUM> patent), and deployment shaft <NUM> is then inserted into inserter tube <NUM>, pushing the cage <NUM> into place as deployment shaft <NUM> advances distally through inserter tube <NUM>. The distal end of the inserter tube <NUM> may have a curved portion <NUM> to help guide deployment of the cage <NUM> as it advances out of the tube <NUM>. The deployment shaft <NUM> may include a blunt distal tip <NUM> that can project out of the distal end of the inserter tube <NUM> to aid in distracting or maintaining the distraction of the disc space <NUM>. Once properly positioned, radiographical techniques may be used to verify the positioning of cage <NUM>, whereupon suture <NUM> is removed, as is deployment shaft <NUM>. Inserter tube <NUM> may remain in place in disc space <NUM> for application of bone graft material before inserter tube <NUM> is removed.

Insertion of cage <NUM> through insertion tube <NUM> limits displacement of patient tissue to a cross-sectional area of insertion tube <NUM>. This is a potential improvement over insertion of cage <NUM> in cage's <NUM> resting shape, as cage's <NUM> irregular resting shape creates a potential for displacing patient tissue across a greater area than that of a cross-section of cage <NUM> at any given location. Cage <NUM> must be deformed from its resting shape to fit in insertion tube <NUM> as shown in <FIG>, and elastically returns to its resting shape upon exiting insertion tube <NUM> as shown in <FIG>. Deformation of cage <NUM> shown in <FIG> is accomplished by flexure of bridge <NUM> of cage <NUM> such that wings <NUM>, <NUM> spread apart and bridge <NUM> presses flat against an interior surface of inserter tube <NUM>. Cage <NUM> returns to its resting shape by bridge <NUM> bowing to an arcuate shape and bringing wings <NUM>, <NUM> together. Bridge's <NUM> capacity for elastic deformation is therefore conducive to delivery of a cage <NUM> that has an irregular resting shape, while causing relatively little displacement of patient tissue when advancing the cage <NUM> towards the spine <NUM>.

In addition to the insertion method described above with regard to <FIG>, any method of insertion described with regard to interbody implants described in the '<NUM> patent may be employed for insertion of any of the cages described within the present disclosure.

Claim 1:
A lumbar interbody fusion device (<NUM>), comprising:
a first wing (<NUM>) and a second wing (<NUM>); and
a bridge (<NUM>) extending along a path from a first end connected to the first wing (<NUM>) to a second end connected to the second wing (<NUM>), the bridge (<NUM>) being elastically deformable such that a distance between the first wing (<NUM>) and the second wing (<NUM>) may vary according to elastic deformation of the bridge (<NUM>), the lumbar interbody fusion device characterized in that:
the bridge comprises a pattern of perforations (<NUM>) extending through the bridge (<NUM>) in a direction transverse to the path and extending radially through the bridge (<NUM>).