Patent Description:
Patients experiencing spinal diseases or disorders such as degenerative disc disease, or spinal injury often require placement of an interbody cage between two adjacent vertebrae. Non-union of the adjacent vertebrae remains a persistent complication, however. Prior art devices have improved procedures required to implant the interbody cage, but require relatively stiff interbody cages to minimize stress shielding of ingrown bone and reduce the risk of cage subsidence. The stiff nature of these interbody cages generally negates any potentially beneficial effects of vibrational waves and/or graft strain on the bone growth process.

<CIT> describes a three-dimensional lattice structure for use in medical implants.

There remains a need for improved spinal implants that modify (e.g., enable, enhance, redirect, control, and/or dampen) applied mechanical load (e.g., a compression force, a torsion force, a sheer force, or a vibrational wave). The present disclosure describes systems and methods (not claimed) that meet those needs.

The present invention provides a dynamic spinal implant configured to be inserted between two adjacent vertebrae, as set out in claim <NUM>.

The present disclosure provides a dynamic spinal implant configured to be inserted between two adjacent vertebrae, the device comprising: a first endplate configured to contact the inferior face of a first vertebrae; a second endplate substantially opposite the first endplate and configured to contact the superior face of a second, adjacent vertebrae; and an inner structure disposed between the first endplate and the second endplate, wherein the inner structure is configured to generate a modified strain tensor on bone graft and/or bone substitute material disposed within the dynamic spinal implant.

The present disclosure describes a method of promoting intervertebral bone growth in a subject, the method comprising: inserting a dynamic interbody fusion device of any one preceding claim between two adjacent vertebrae; and optionally applying a mechanical load to the dynamic interbody fusion device for a period of time sufficient to promote bone growth.

These and other features are described in greater detail herein.

The figures depict various embodiments of this disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of embodiments described herein.

Referring generally to <FIG>, the present disclosure provides dynamic interbody fusion devices; and inner structure repeatable units, resonating elements, free resonators, and mechanical load directors for incorporation therein.

Generally, spinal implant systems consistent with the present disclosure are intended to fuse together two adjacent vertebrae. The spinal implant systems can be an interbody fusion cage, an anterior plate, a posterior fixation, or a combination of those.

In some embodiments, the spinal implant comprises load sharing and deformable structure design allowing graft strain in a desired range (e.g., +/-<NUM>%).

The strain experienced by the graft is a direct result of the spinal implant deformation. Since the graft is located within the interbody space, any local deformation of the structure leads to the same amount of deformation of the graft at the interface of this local structure. As a consequence, the whole bone graft is subjected to strain. One can therefore assume that the strain of the graft at the interface with the spinal implant is directly related to the strain of the spinal implant.

In a linear elastic approximation, the spinal implant structure follows Hooke's law, defined as below: <MAT> where σi is the stress tensor, Cij is the stiffness tensor and εj is the strain tensor.

By defining the <NUM> different components of the stiffness tensor Cij of the spinal implant at each locus of the structure, the strain experienced by the graft at the interface with the spinal implant can be controlled and limited within a desired range.

The profile of each coefficient of the strain tensor are defined along the x-, y- and z-axes in order to control the strain. In some embodiment, the stiffness tensor is defined to limit the stress in order to remain under high strain deleterious for the bone formation. In some embodiments, the strain tensor is defined to allow different targeted strain of the graft along x, y and z axis. Especially the strain along the spine main axis, called εzz, should be greater than in the other direction. In some embodiment, the stiffness tensor is defined to avoid shear stress experienced by the graft.

In some embodiments, the stiffness tensor of the spinal implant is defined such that the graft strain is maintained within a constant range all along the bone migration process.

The definition of the structure can made either with a direct patterning (repetition of a unit cell within a volume), a conformal patterning (optimal mesh of a volume) or a topology optimization patterning.

Referring now generally to <FIG> and <FIG>, dynamic interbody fusion devices <NUM> consistent with the present disclosure comprise an interbody cage portion <NUM>, and optionally an anterior plate <NUM>.

The interbody cage portion <NUM> is sized and shaped to be inserted between two adjacent vertebrae V1,V2, for example to replace an intervertebral disc that has been injured. The interbody cage portion <NUM> includes an inner structure <NUM> disposed between a superior endplate 122a and an inferior endplate 122b. The inner structure <NUM> includes voids to support bone growth media and/or bone graft material (not shown). The voids may be disposed between a series of struts <NUM> (<FIG>).

In some embodiments, such as those consistent with the embodiment specifically shown in <FIG>, the interbody cage consists essentially of an inner structure <NUM> without additional structure provided by a superior endplate 122a, an inferior endplate 122b, or an outer wall <NUM>. In such embodiments, and after implantation into an intervertebral space of a subject, the inferior portion of the inner structure <NUM> will be in direct contact with the inferior adjacent vertebra V2, while the superior portion of the inner structure <NUM> will be in direct contact with the superior adjacent vertebra V1.

In some embodiments, the superior endplate 122a includes one or more holes 126a through which bone may grow, resulting in fusion of the interbody cage <NUM> with the adjacent superior vertebrae V1.

In some embodiments, the inferior endplate 122b includes one or more holes (not shown) through which bone may grow, resulting in fusion of the interbody cage <NUM> with the adjacent inferior vertebrae V2.

The anterior plate <NUM> is configured to be anchored to the adjacent superior vertebrae V1 (e.g., by driving an anchor (e.g., an anchor nail or a screw) through one or more anchoring holes 146a of a superior plate portion 142a into the adjacent superior vertebrae V1), the adjacent inferior vertebrae V2 (e.g., by driving an anchor through one or more anchoring holes 146b of an inferior plate portion 142b into the adjacent inferior vertebrae V2), and the interbody cage portion <NUM> (e.g., by driving an anchor through one or more anchoring holes 146c of a central plate portion 142c into the interbody cage portion <NUM>). In some embodiments, a central plate portion 142c is disposed between the superior inner structure 144a and the inferior inner structure 144b. In some embodiments, the anterior plate <NUM> includes a superior inner structure 144a that includes voids and/or an inferior inner structure 144b that includes voids that, in combination with the designs of the superior plate portion 142a, the inferior plate portion 142b, and the central plate portion 142c, operate to enable a predetermine amplitude of strain at desirable vibrational frequency(ies).

In some embodiments, the interbody cage portion <NUM> includes an inner wall <NUM> defining a central void 127a. The central void 127a does not include material that forms the inner structure <NUM>. In some embodiments, the inner wall <NUM> includes one or more holes <NUM>.

In some embodiments, such as those shown specifically in <FIG>, the interbody cage portion <NUM> includes an outer wall <NUM> disposed between the superior endplate 12a and the inferior endplate 122b. In some embodiments, the outer wall <NUM> includes one or more holes <NUM>.

Referring now to <FIG>, the interbody cage portion <NUM> may have a controlled rigidity structure that imparts a first spring constant k across the x-axis of the interbody cage portion <NUM>, a second spring constant k' across the z-axis of the interbody cage portion <NUM>, and a third spring constant ky across the y-axis of the interbody cage portion <NUM>. The first spring constant k is related to the stiffness tensor Cij of Equation <NUM>.

Referring now to <FIG>, the interbody cage portion <NUM> may have a controlled low-rigidity auxetic structure (e.g., in the inner structure <NUM>) that imparts a first spring constant k (in this example, a substantially linear spring constant k) across the x-axis of the interbody cage portion <NUM>, and a second spring constant k' (in this case, a nonlinear or parabolic spring constant k' across the z-axis of the interbody cage portion <NUM>. In this example, the third spring constant ky across the y-axis of the interbody cage portion <NUM> is not specifically graphed.

Referring now to <FIG>, the interbody cage portion <NUM> may include an internal graft shield <NUM> configured to contact (e.g., engage or contain) bone graft material BG. A flexible pivot 123p is disposed between the internal graft shield <NUM> and the outer wall <NUM>, and enables the internal graft shield <NUM> to move in a direction contrary to movement of the outer wall <NUM> (see arrows). The flexible pivot 123p defines a radius r that can be chosen to provide a predetermined amplitude ratio between the flexible pivot 123p and the outer wall <NUM>. Without wishing to be bound by theory, it is believed that the contrary movement of the internal graft shield <NUM> relative to the outer wall <NUM> enabled by the flexible pivot 123p reduces displacements of the bone graft material BG, or portions thereof, in response to compressive forces or vibrations applied to the outer wall <NUM> of the interbody cage portion <NUM>. The predetermined amplitude ratio in some embodiments is defined as shown in Equation <NUM> below: <MAT>.

Turning now to <FIG>, the interbody cage portion <NUM> may include a pair of opposing internal guide rails <NUM>', for example disposed continuously/contiguously with the side walls <NUM>, and configured to receive a pair of graft shield rails <NUM>'a that are associated with graft shield <NUM>'. The graft shield <NUM>' is not attached to the interbody cage portion <NUM> in these embodiments; rather, the graft shield <NUM>' is free to move within the interbody cage portion <NUM>, with the largest freedom of movement being along the z-axis (e.g., vertically).

As shown in <FIG>, interbody cage portions <NUM> consistent with some embodiments include a slit <NUM>', such as a lateral slit <NUM>', disposed in the side wall <NUM>. In some embodiments, the slit <NUM>' is disposed at least partially between one or more caudal fixation holes 126a and one or more cranial fixation holes 126b. In some embodiments, for example those in which the interbody cage portion <NUM> is intended to be implanted into a subject by an anterior lumbar interbody fusion ("ALIF") procedure, the lateral slit <NUM>' may be disposed in an anterior portion of the side wall <NUM>.

In some embodiments, such as those consistent with the embodiment specifically shown in <FIG>, the slit <NUM>' is located all around or substantially around the interbody cage portion <NUM> of the spinal implant device <NUM>. In such embodiments, the lower structure (e.g., the inferior endplate 122b) and the upper structure (e.g., the superior endplate 122a) are associated only (or substantially only) through their associations with the inner structure <NUM> (in this depicted example, the auxetic lattice). The slit <NUM>' in the outer wall <NUM> in such embodiments may act as a mechanical stop to prevent compression along the z-axis more than a predetermined amount; when the slit <NUM>' collapses under compression load, the interaction of the complementary pattern (e.g., teeth) located on the interface between the two ends of the side wall <NUM> prevent shear and bending motion of the implant <NUM>. In these embodiments, the stiffness of the inner structure <NUM> along the z-axis is relatively low. Under compression, this embodiment of the spinal implant <NUM> has a double slope response to compressive force along the z-axis in terms of stiffness shown in <FIG>. In the beginning of the deformation, only the inner structure <NUM> is compressed. Once the mechanical stop is reached (e.g., when the slit <NUM>' collapses), both the inner structure <NUM> and the outer wall <NUM> are compressed, resulting in a much greater stiffness or resistance to the compressive force along the z-axis. The slopes (e.g., resistance to compression) can be adjusted (e.g., tuned) either by adjusting the parameters of the inner structure <NUM> (e.g., strut diameter 124d,124d', length, initial deflection 124f' between adjacent flexion struts 124f, etc.) and/or the thickness and design of the outer wall <NUM>.

Referring now specifically to <FIG>, two in silico model dynamic interbody fusion devices <NUM> including a slit <NUM>' completely separating the superior endplate 122a and the inferior endplate 122b and including different inner structures <NUM> were prepared in silico as shown in <FIG>. In these embodiments, the inner structure <NUM> primarily absorbs mechanical load imparted on the dynamic interbody fusion device <NUM> while the slit <NUM>' remains in an "open" configuration. When the slit126' collapses, or adopts a "closed" configuration, the superior endplate 122a, the inferior endplate 122b, and the side wall <NUM> (when present) then primarily absorb mechanical load imparted on the device <NUM>. For example, when compressed along the z-axis, the devices <NUM> shown in <FIG> initially resist the compression force at a first resistance slope m<NUM> that is related to the specific dimensions and parameters of the inner structure <NUM> of that device <NUM>. Once the slit <NUM>' collapses under the compressive force, however, the device <NUM> resists further compression at a second resistance slope m<NUM> that is related to the specific dimensions and parameters of the superior endplate 122a, the inferior endplate 122b, and the side wall <NUM> (when present). Thus, the device <NUM> may be tuned to resist imparted mechanical load along any axis by a desired amount by selecting the dimensions, materials, parameters, and orientation of the inner structure <NUM>, the superior endplate 122a, the inferior endplate 122b, and the side wall <NUM>.

The caudal fixation holes 126a and/or cranial fixation holes 126b may, in some embodiments, also define an instrument interface area 125a to which the interbody cage portion <NUM> may be affixed (e.g., temporarily affixed) to an implantation instrument.

Referring now generally to <FIG> and <FIG>, the inner structure <NUM> includes a lattice pattern 124a formed by struts <NUM>, and/or flexion struts 124f, and/or cage struts 124c; and voids <NUM> disposed between the structs <NUM>, 124f, 124c. The struts <NUM> and flexion struts 124f may have any suitable cross-sectional shape, such as a square, a circle, a rhombus, a rectangle, a trapezoid, an oval, a triangle, a quadrilateral, a pentagon, a hexagon, etc. In some embodiments, the struts <NUM> have a circular cross-sectional shape with a strut diameter 124d. In some embodiments, the flexion struts 124f have a circular cross-sectional shape with a flexion strut diameter 124fd.

Generally, the resonance frequency(ies) of the inner structure <NUM> can be selected by using one or more lattice patterns 124a; using struts <NUM>, flexion struts 124f, and/or cage struts 124c of differing dimensions and diameters; and the material(s) from which the struts <NUM>, flexion struts 124f, and cage struts 124c are constructed.

As shown in <FIG>, the lattice pattern 124a in some embodiments is an orthorhombic body-centered lattice pattern including eight struts <NUM>. In some embodiments, each strut <NUM> has a similar length and diameter 124d. In some embodiments, each strut <NUM> has an identical length and diameter 124d. The orthorhombic body-centered lattice pattern has a repeatable unit with a width W, a length L, and a height H. In some embodiments, the width W is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the length L is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the height H is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the width W, length L, and height H are substantially similar. In some embodiments, the width W, length L, and height H are identical.

Referring now to <FIG>, the lattice pattern 124a in some embodiments is a caged orthorhombic body-centered lattice pattern including eight struts <NUM> surrounded by cage struts 124c. In some embodiments, each strut <NUM> has a similar length and diameter 124d. In some embodiments, each strut <NUM> has an identical length and diameter 124d. The caged orthorhombic body-centered lattice pattern has a repeatable unit with a width W, a length L, and a height H. In some embodiments, the width W is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the length L is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the height H is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the width W, length L, and height H are substantially similar. In some embodiments, the width W, length L, and height H are identical.

As shown in <FIG>, the lattice pattern 124a in some embodiments is a dode-thin lattice pattern including <NUM> struts <NUM>. In some embodiments, each strut <NUM> has a similar length and diameter 124d. In some embodiments, each strut <NUM> has an identical length and diameter 124d. The dode-thin lattice pattern has a repeatable unit with a width W, a length L, and a height H. In some embodiments, the width W is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the length L is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the height H is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the width W, length L, and height H are substantially similar. In some embodiments, the width W, length L, and height H are identical.

Referring now to <FIG>, the lattice pattern 124a in some embodiments is a diamond lattice pattern including <NUM> struts <NUM>. In some embodiments, each strut <NUM> has a similar length and diameter 124d. In some embodiments, each strut <NUM> has an identical length and diameter 124d. The diamond lattice pattern has a repeatable unit with a width W, a length L, and a height H. In some embodiments, the width W is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the length L is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the height H is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the width W, length L, and height H are substantially similar. In some embodiments, the width W, length L, and height H are identical.

As shown in <FIG> and <FIG>, the lattice pattern 124a in some embodiments is an auxetic lattice pattern including struts <NUM> and flexion struts 124f. In some embodiments, each strut <NUM> has a similar length and diameter 124d. In some embodiments, each strut <NUM> has an identical length and diameter 124d. In some embodiments, each flexion strut 124f has a similar diameter 124fd. In some embodiments, each flexion strut 124f has an identical diameter 124fd. The auxetic pattern may feature an initial deflection 124f' between adjacent flexion struts 124f; the resonant properties of the inner structure <NUM> may be tuned in part by including an auxetic lattice pattern with a specific initial deflection 124f'. Generally, the deflection of the flexion struts may be defined by the maximum change in the distance 124f' between the respective apexes of two adjacent flexion struts 124f. In some embodiments, the deflection is not more than about half the height H less the diameter 124fd of the flexion struts 124f (i.e., H/<NUM> - 124fd). In some embodiments, the deflection is not more than about <NUM>, for example not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>. The auxetic lattice pattern has a repeatable unit with a width W, a length L, and a height H. In some embodiments, the width W is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the length L is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the height H is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the width W, length L, and height H are substantially similar. In some embodiments, the width W, length L, and height H are identical.

Referring now to <FIG>, the lattice pattern 124a in some embodiments is an S-shaped lattice pattern including struts <NUM>. In some embodiments, the struts <NUM> have a circular cross-sectional shape having a diameter 124d (not shown). In other embodiments, the struts have a rectangular cross-sectional shape having a width 124d and a length 124d'. The S-shaped lattice pattern has a repeatable unit with a width W, a length L, and a height H. In some embodiments, the width W is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the length L is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the height H is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the width W, length L, and height H are substantially similar. In some embodiments, the width W, length L, and height H are identical.

In some embodiments, the inner structure <NUM> includes only one lattice pattern 124a. In other embodiments, the inner structure <NUM> includes more than one lattice pattern 124a, such as <NUM> lattice patterns 124a, <NUM> lattice patterns 124a, <NUM> lattice patterns 124a, <NUM> lattice patterns 124a, <NUM> lattice patterns 124a, <NUM> lattice patterns 124a, <NUM> lattice patterns 124a, <NUM> lattice patterns 124a, <NUM> lattice patterns 124a, or more than <NUM> lattice patterns 124a.

Regardless of the lattice pattern(s) 124a, the inner structure <NUM> includes a ratio of the volume of voids <NUM> to the volume of struts <NUM>,124f,124c of about <NUM>:<NUM> to about <NUM>:<NUM>, for example about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, about <NUM>:<NUM>, or about <NUM>:<NUM>.

In some embodiments, the distribution of the lattice pattern units through the inner structure <NUM> is substantially consistent throughout the inner structure <NUM>. In other embodiments, the density of lattice pattern units through the inner structure <NUM> is unequal, for example including one or more areas of relatively high density and one or more areas of relatively low density. In some embodiments, the density of lattice pattern units through the inner structure <NUM> represents a gradient, such as a linear gradient, a quadratic gradient, an exponential gradient, or a logarithmic gradient (e.g., a natural logarithmic gradient and/or a base-<NUM> logarithmic gradient).

In some embodiments, the inner structure <NUM> is formed using an additive (e.g., 3D printing) process. In such embodiments, the inner structure <NUM> may consist or consist essentially of any material that can be used in an additive (e.g., 3D printing) process that is also biocompatible. Non-limiting examples of such materials include titanium, poly-ethyl ethyl ketone (PEEK), stainless steel (e.g., <NUM> or BIODUR <NUM> stainless steel), cobalt chrome alloy, a ceramic, or a combination thereof.

Turning now to <FIG>, interbody cage portions <NUM> consistent with some embodiments of the present disclosure include a plurality of free resonators <NUM> disposed on lattice structures 124a/<NUM> and/or on transverse plates 124f/124c of the inner structure <NUM>. In some embodiments, all of the free resonators <NUM> have stem portions <NUM> that are aligned, for example parallel to the z-axis as shown specifically in <FIG>.

Referring now to <FIG>, interbody cage portions <NUM> consistent with some embodiments include both a lattice structure in the inner structure <NUM> and a graft shield <NUM>' surrounding the cavity 127a. The graft shield <NUM>' is associated with the superior endplate 122a and/or the inferior endplate 122b via springs <NUM>.

As shown in <FIG>, interbody cage portions <NUM> consistent with some embodiments include resonating elements <NUM> (<FIG>) and/or free resonators <NUM> (<FIG>) disposed within the cavity 127a.

Referring now generally to <FIG>, dynamic interbody fusion devices <NUM> consistent with the present disclosure may include one or more resonating elements <NUM>. The resonating element(s) <NUM> may be sized and shaped to vibrate at a desired frequency, for example to amplify or dampen vibration of the dynamic interbody fusion device <NUM> at predetermined frequency(ies).

Generally, resonating elements <NUM> include a mass <NUM> associated with a stem portion <NUM>, such as at or near one end of the stem portion <NUM>. When the stem portion <NUM> (e.g., the opposite end of the stem portion <NUM>) is affixed to or otherwise associated with the dynamic interbody fusion device <NUM> (e.g., with the inner structure <NUM>), the resonating elements <NUM> act as harmonic resonators, vibrating in response to wave(s) applied to the dynamic interbody fusion device <NUM> when the wave includes a frequency in resonance with the vibrational frequency(ies) of the resonating element <NUM>. In some embodiments, the resonating element <NUM> has a fundamental harmonic frequency of about <NUM> to about <NUM>, for example about <NUM> , about <NUM> , about <NUM> , about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

The resonating element <NUM> may be formed of any suitable biocompatible material, such as titanium, PEEK, stainless steel (e.g., <NUM> or BIODUR <NUM> stainless steel), cobalt chrome alloy, a ceramic, or a combination thereof. In some embodiments, the resonating element <NUM> is formed by an additive manufacturing process, such as 3D printing. In some embodiments, the resonating element <NUM> is formed concurrently with formation of the inner structure <NUM>, for example by 3D printing methods.

Referring now specifically to <FIG>, a resonating element <NUM> consistent with one embodiment of the present disclosure comprises a disc-shaped mass portion <NUM> disposed at a distal end 164a of a stem portion <NUM>. The disc-shaped mass portion <NUM> has a thickness <NUM> and a diameter 162d. In some embodiments, the thickness <NUM> is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. In some embodiments, the diameter 162d is about <NUM> to about <NUM>, for example about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. The stem portion <NUM> has a length <NUM> and a diameter 164d. In use, the resonating element <NUM> is attached to the inner structure <NUM> at the proximal end 164b of the stem portion <NUM>.

As shown in <FIG>, a resonating element <NUM> consistent with another embodiment of the present disclosure includes a spherical mass portion <NUM> disposed at a distal end 164a of a stem portion <NUM>. The spherical mass portion <NUM> has a radius 162r; the stem portion <NUM> has a stem diameter 164d and a length <NUM>. In use, the resonating element <NUM> is attached to the inner structure <NUM> at the proximal end 164b of the stem portion <NUM>.

The resonant frequency(ies) of the resonating element <NUM> are determined (e.g., tunable) by selecting the size and shape of the mass portion <NUM>, the length <NUM> of the stem portion <NUM>, and the material from which the resonating element <NUM> is made. Generally, a higher mass of the mass portion <NUM> and longer length <NUM> of the stem portion <NUM> result in lower resonant frequencies compared to a resonating element <NUM> made from the same material but having a smaller mass of the mass portion <NUM> and shorter length <NUM> of the stem portion <NUM>.

Referring now to <FIG> and <FIG>, a resonating element <NUM> consistent with the present disclosure may be a free-resonating element <NUM> that is retained by, but not affixed to, the inner structure <NUM>. In some embodiments, the free-resonating element <NUM> includes a first mass portion <NUM> disposed at a first end 164a of a stem portion <NUM>, and a second mass portion <NUM>' disposed at a second end 164b of the stem portion <NUM>. The first mass portion <NUM> may feature a similar or identical size and shape as the second mass portion <NUM>' in some embodiments; in other embodiments, the first mass portion <NUM> has a different size and/or shape than the second mass portion <NUM>'. The stem portion <NUM> extends through a hole 124t in the inner structure <NUM> that has a slightly larger diameter 124td than the diameter 164d of the stem portion <NUM>. The stem portion <NUM> has a length <NUM> greater than the width 124W of the strut <NUM>/124f/124c through which the stem portion <NUM> extends. In such embodiments, the resonating element <NUM> is free to slide (e.g., oscillate) through the strut <NUM>/124f/124c a maximum distance approximately equal to the length <NUM> of the stem portion <NUM> in response to an applied wave (e.g., an applied acoustical wave).

<FIG> show representative arrangements of one or more resonating elements <NUM> within repeatable unit cubes of various inner structure patterns 124a. In some embodiments, such as that shown in <FIG>, only one resonating element <NUM> is disposed in each repeatable unit cube of the inner structure pattern 124a. In some embodiments, the resonating element <NUM> is disposed in each repeatable unit cube of the inner structure <NUM> such that each resonating element <NUM> is oriented in the same direction. In other embodiments, the resonating element <NUM> is disposed in each repeatable unit cube of inner structure <NUM> such that the resonating element <NUM> of one repeatable unit cube may be oriented in a different direction than the resonating element <NUM> of an adjacent cube.

Referring now to <FIG>, a repeatable unit cube 124a of the inner structure <NUM> of some embodiments includes more than one resonating element <NUM>. In this example, the inner structure pattern 124a includes five resonating elements <NUM>: one centrally located and four disposed in four of the eight internal corners. In this embodiment, the five resonating elements <NUM> are oriented in five different directions.

As shown in <FIG>, a repeatable unit cube 124a of the inner structure <NUM> of some embodiments includes six resonating elements <NUM>, each disposed at the center junction of a orthorhombic body-centered inner structure pattern 124a. Five of the six resonating elements <NUM> are visible in the illustrate perspective view, with the sixth resonating element <NUM> disposed opposite the center junction from and pointing in the opposite direction than the horizontally oriented resonating element <NUM>'.

Referring now to <FIG>, one or more free-resonating elements <NUM> may be incorporated into a repeatable inner structure pattern 124a in any suitable location and orientation. In the embodiment specifically shown in <FIG>, for example, one free-resonating element <NUM> is disposed through a hole 124t (not shown) in the central junction of the orthorhombic body-centered inner structure pattern 124a.

Referring now generally to <FIG> and <FIG>, one or more mechanical load directors <NUM> may be incorporated into a dynamic interbody fusion device <NUM> consistent with the present disclosure to redirect (e.g., focus) a propagating wave to a targeted area of interest 18t or away from a targeted area 18t. Without wishing to be bound by theory, it is believed that incorporation of one or more mechanical load directors <NUM> into the dynamic interbody fusion device <NUM> may enable redirection (e.g., focusing) of a propagating wave based at least in part on a difference in relative stiffness of the mechanical load director(s) <NUM> and the surrounding structural features (referred to generally herein as "mechanical structure <NUM>").

In some embodiments, the mechanical load director <NUM> includes a guiding structure <NUM> associated with a mechanical structure <NUM>. In some embodiments, the mechanical load director <NUM> further includes one or more empty spaces <NUM> disposed between at least a portion of the guiding structure <NUM> and the mechanical structure <NUM>.

In some embodiments, such as those consistent with the embodiment specifically shown in <FIG>, the mechanical structure <NUM> is a strut <NUM>/124f/124c, and the guiding structure <NUM> is defined by one or more empty spaces <NUM> formed in the strut <NUM>/124f/124c.

In some embodiments, such as those consistent with the embodiment specifically shown in <FIG>, the mechanical structure <NUM> is a strut <NUM>/124f/124c, and the guiding structure <NUM> is defined by a contour of the guiding structure <NUM> formed in the strut <NUM>/124f/124c.

In some embodiments, the anterior plate <NUM> includes one or more mechanical load directors <NUM>. In other embodiments, the outer wall <NUM> includes one or more mechanical load directors <NUM>. In some embodiments, at least one mechanical load director <NUM> is disposed on the anterior plate <NUM> and at least one mechanical load director <NUM> is disposed on the interbody cage portion <NUM>.

The mechanical load director <NUM> may be formed of any suitable biocompatible material, such as titanium, PEEK, stainless steel (e.g., <NUM> or BIODUR <NUM> stainless steel), cobalt chrome alloy, a ceramic, or a combination thereof. In some embodiments, the mechanical load director <NUM> is formed by an additive manufacturing process, such as 3D printing. In some embodiments, the mechanical load director <NUM> is formed concurrently with formation of the inner structure <NUM>, for example by 3D printing methods.

In some embodiments, such as those consistent with the embodiment specifically shown in <FIG>, the mechanical load director <NUM> includes an empty space186 disposed through the mechanical structure <NUM>.

Dynamic interbody fusion devices <NUM> may be implanted into a patient in need thereof by any suitable means, including by standard surgical techniques for implanting interbody cages into an intervertebral space. Bone graft material and/or bone growth media may be inserted into the dynamic interbody fusion device <NUM> if desired.

Once implanted, growth of bone tissue between the adjacent vertebrae V1,V2 may be stimulated by applying a vibrational wave to the dynamic interbody fusion device <NUM>. The generated vibrational wave propagates through the patient's skin and tissues until it contacts the dynamic interbody fusion device <NUM>. In some embodiments, the vibrational wave is generated by the subject's own movement. For example, vibrational wave(s) may be generated by the subject's movement while walking, running, driving, riding in a vehicle, bicycling, dancing, or the like.

The vibrational wave may then be transformed by interacting with the dynamic interbody fusion device <NUM>. For example, one or more frequencies present in the applied wave (optionally modified after traversing through the patient's skin and tissues) may be enhanced or dampened by the resonance frequency(ies) of the inner structure <NUM>. Application of a vibrational wave having specific frequency(ies) to the dynamic interbody fusion device <NUM> may therefore promote bone growth between the vertebrae V1,V2 and substantially shorten the vertebral fusion process.

An in silico study of an interbody cage portion <NUM> consistent with <FIG> was performed using Altair® Radioss™ and the following parameters:.

The resulting dynamic response (curves 27A and 27B) to the forced excitation (curves 27C and 27D) is shown in <FIG>: the graft shield amplitude is <NUM> at a frequency of <NUM>.

These results demonstrate that interbody cage portions <NUM> consistent with the present disclosure are capable of isolating graft material from vibrations by up to <NUM>%.

To understand how interbody cage portions <NUM> consistent with the present disclosure may behave in situ, an in silico analysis of the interbody cage portion <NUM> shown in <FIG> (Example <NUM>) was performed using Altair® Radioss™ and the following parameters:.

As shown in <FIG>, observed Von Mises stresses did not exceed the yield strength of the specified materials. The maximum stress in cortical bone was observed at <NUM> MPa, and <NUM> MPa in the trabecular bone, while the maximum stress in the endplates was <NUM> MPa. The maximum stress observed in the interbody cage portion <NUM> was observed to be <NUM> MPa.

An oscillating motion was observed in the lattice structure <NUM> of the interbody cage portion <NUM>, as shown in <FIG> (plot 30A) in response to the imposed displacement of the S1 spinal bone (plot 30B). Without wishing to be bound by theory, it is postulated that the observed oscillating motion may be due the lack of physical connection of the lattice structure <NUM> to the superior endplate 122a and the inferior endplate 122b. <FIG> shows the graft shield dynamic response as a function of position over time; <FIG> shows the graft shield dynamic response as a function of velocity over time.

An in silico study of a dampening system including five free resonators <NUM> consistent with the embodiment shown in <FIG> was performed. The five free resonators <NUM> were oriented in parallel in a fine cage plate, surrounded by a bone graft cube obtained by a Boolean operation (<FIG>). A fine element model simulating a forced excitation of <NUM> and <NUM> using a normal graft consistent with Simmons, Meguid & Pilliar (<NUM>), and a softer graft representing fluid-like behavior before ossification. Relevant parameters are provided below.

This study revealed that the central resonating element had a maximum amplitude of <NUM> in soft graft at <NUM>, an amplitude that was <NUM>% higher than the input excitation (<FIG>, <FIG>). As shown in <FIG>, a second mode at about <NUM> emerged, suggesting that promotion of vibrations at specific frequencies might be possible using tuned resonating elements <NUM>. The observed maximal tissue strain for this model was <NUM>%, which is superior to the recommended maximal strain of <NUM>% for ingrown bone (Lin et al.

The central resonating element in soft graft responded even more unexpectedly at <NUM>, with a maximum amplitude of <NUM>-more than twice the input amplitude of <NUM> (<FIG>, <FIG>). A second mode at about <NUM> was observed in this model (<FIG>), further suggesting that a tuned resonating element <NUM> may be employed to promote a desired vibrational frequency. Maximum tissue strain observed in this model was <NUM>%, also superior to the prescribed <NUM>% tissue strain level.

When this model was tested in normal graft at <NUM> excitation, the dynamic response of the resonating element <NUM> was synchronized to the excitation (<FIG>, <FIG>). The maximum amplitude was <NUM>, and the maximum graft strain was only <NUM>% under these conditions. These data suggest that vibration isolation and promotion are unlikely to occur when graft transitions from soft graft to normal graft (e.g., many days after surgery).

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.

Claim 1:
A dynamic spinal implant configured to be inserted between two adjacent vertebrae, the device comprising:
a first endplate (122a) configured to contact the inferior face of a first vertebrae;
a second endplate (122b) substantially opposite the first endplate and configured to contact the superior face of a second, adjacent vertebrae;
an inner structure (<NUM>) disposed between the first endplate and the second endplate;
and a bone graft or bone substitute material disposed within the dynamic spinal implant,
wherein the inner structure is configured to generate a modified strain tensor on the bone graft and/or bone substitute material disposed within the dynamic spinal implant,
wherein the inner structure is configured to modify a mechanical load to promote bone growth within the inner structure, and wherein the dynamic spinal implant comprises at least one resonating element (<NUM>).