Patent Description:
Spinal disorders such as degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor, and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and aging. Spinal disorders typically result in symptoms including pain, nerve damage, and partial or complete loss of mobility. For example, after a disc collapse, severe pain and discomfort can occur due to the pressure exerted on nerves and the spinal column.

Non-surgical treatments, such as medication, rehabilitation and exercise can be effective, however, may fail to relieve the symptoms associated with these disorders. Surgical treatment of these spinal disorders includes fusion, fixation, discectomy, laminectomy, osteotomy and implantable prosthetics. These treatments may employ spinal implants and, in some cases, the placement of interbody implants via a variety of invasive, partially invasive and/or minimally invasive surgical pathways. Furthermore, in spinal disorders wherein a patient has an abnormal spinal curvature, surgeons may perform a complete and/or partial osteotomy to remove bony structures from the spine in order to reorient the bones of the spine to provide the patient with a desired spinal curvature. In many cases, however, there is difficulty in providing an accurate kyphotic and/or lordotic angle when performing osteotomy. Various factors contribute to this difficulty, including, but not limited to: the challenge of cutting a wedge-shaped aperture in the spinal anatomy having a precise slope; and the breakdown or subsidence of the remaining bony portions after an osteotomy is performed. This disclosure describes an improvement in these technologies.

Prior art document <CIT> discloses an intrabody implant adapted to be placed between at least <NUM> separated portions of a single bony structure being a vertebral body according to the preamble of claim <NUM>.

Further examples of prior art concerning interbody spacer for insertion between vertebral members are disclosed in <CIT>, <CIT>, <CIT> and <CIT>. From <CIT> and <CIT> intrabody implants are known for non-vertebrae bones.

The present invention provides an intrabody implant adapted to be placed between at least two separated portions of a single bony structure being a vertebral body according to claim <NUM>. Further embodiments of the invention are described in the dependent claims Associated methods are also described herein to aid understanding of the invention, but these do not form part of the claimed invention.

Further, various illustrative methods not claimed are also described to further the understanding of the inventive intrabody implant, especially in respect to illustrative methods for surgically adjusting a curvature of the spine. Such illustrative methods may include steps of: removing a wedge-shaped portion of a single vertebral body to form <NUM> at least partially-separated portions of the vertebral body; providing a wedge-shaped intrabody implant comprising first and second surfaces disposed at an acute angle relative to one another; placing the wedge-shaped intrabody implant between the <NUM> at least partially-separated portions; and closing the <NUM> at least partially-separated portions about the implant. The illustrative methods may result in the orientation of the <NUM> at least partially-separated portions of the vertebral body at a correction angle relative to one another.

The illustrative methods described herein may make use of the inventive intrabody implant to provide lordotic and/or kyphotic correction to a spinal column at the level of the single vertebral body or across multiple levels, as part of an osteotomy procedure that may include, but is not limited to, a pedicle subtraction osteotomy (PSO). The closing step disclosed herein may comprise securing the <NUM> at least partially-separated portions of the single vertebral body relative to one another using a rod and pedicle screw construct. Furthermore, the illustrative methods may also comprise packing the intrabody implant with bone-growth promotion material (in a bone growth aperture defined in the intrabody implant, for example).

The exemplary embodiments of an intrabody implant disclosed herein are discussed in terms of medical devices for the treatment of musculoskeletal disorders and more particularly, in terms of an intrabody implant for placement after osteotomy. It is envisioned that the disclosed intrabody implant may provide, for example, a means for more accurately introducing a correction angle to a portion of the spinal column by virtue of the intrabody implant, which may enable a surgeon to more precisely predict the closure and/or correction angle despite variations in wedge angle that may be introduced in the "bone-on-bone" closure of known osteotomy procedures. In one embodiment, the wedge design of the intrabody implant may aid in the maintenance of anterior vertebral body height while allowing for closure (height collapse) on a posterior portion of the same vertebral body in order to introduce a corrective angulation.

The various embodiments described herein may also be especially useful in maintaining the shape and position of the vertebral body during and after an osteotomy. For example, in known osteotomy procedures as a wedge-cut vertebral body (see <FIG>, for example) collapses, the anterior portion of the vertebral body (V1, V2) may also break during closure of the angle Θ. It may be difficult for a surgeon to predict any shifts that may occur once the anterior portion of the vertebral body breaks. Thus, the intrabody implant <NUM> (see <FIG>, for example) may help restrict any shift in the bony structure being a vertebral body V1, V2 remaining after an osteotomy procedure.

Referring to <FIG>, an illustrative method using an inventive intrabody implant for surgically adjusting a curvature of the spine is described in the following to further improve the understanding of potential uses of the inventive intrabody implant. A vertebral body V can be selected for an osteotomy procedure which may include removing portions of the pedicle P, spinous processes SP and/or facet j oint structures F at the level of the vertebral body V. While level L3 is depicted in <FIG>, a surgeon may apply the illustrative method described herein to any number of spinal levels in the lumbar, thoracic, or cervical spine to introduce a corrective curvature to the spine.

As shown in <FIG>, the illustrative method may further comprise removing a wedge-shaped portion of a single vertebral body V (see <FIG>) to form <NUM> at least partially-separated portions V1, V2 of the single vertebral body V. A surgeon may select and/or measure a corrective angle Θ to serve as the basis for this step. However, and as described further herein, the acute angle α defined by the surfaces <NUM>, <NUM> of the implant <NUM> (see <FIG>) may be used to ensure that the completed spinal surgery results in a desired level of spinal curvature (see <FIG>) regardless of the angle Θ of the removal cut made by the surgeon as part of the removal step.

As described herein with respect to <FIG>, the removing step may comprise a pedicle subtraction osteotomy (PSO) procedure wherein the pedicle P, spinous process SP, and/or portions of the facet joint structure F are completely or partially removed from the vertebral body.

The illustrative method may further comprise providing an inventive wedge-shaped intrabody implant <NUM> (as described further herein with respect to <FIG>) comprising a first surface <NUM> and a second surface <NUM>, wherein the second surface <NUM> may be disposed at an acute angle α to the first surface <NUM>. In some embodiments as shown in <FIG>, the intrabody implant <NUM> may be provided with an aperture <NUM> extending through the wedge-shaped intrabody implant <NUM> to allow for bone growth therethrough. The illustrative method may further comprise packing the aperture <NUM> with a bone-growth promotion material prior to the placing step described herein with respect to <FIG>.

As shown in <FIG>, the illustrative method can further comprise placing the wedge-shaped intrabody implant <NUM> between the <NUM> at least partially-separated portions V1, V2 of the single vertebral body V, and closing the <NUM> at least partially-separated portions V1, V2 of the single vertebral body about the intrabody implant <NUM>. Therefore, the <NUM> at least partially-separated portions V1, V2 of the single vertebral body are oriented at a correction angle relative to one another. Preferably, the resulting correction angle may be substantially predictable based on the selected implant. For example, the correction angle may be within a selected number of degrees of the acute angle defined by the intrabody implant. The range of difference between the correction angle and the acute angle may be relatively wide (i.e. <NUM>-<NUM> degrees). The range of difference between the correction angle and the acute angle may be relatively narrow (i.e. <NUM>-<NUM> degrees).

According to various illustrative methods, the correction angle of the spinal column defined at least in part by the acute angle α of the intrabody implant may provide a lordotic correction to a spinal column at the level of the single vertebral body V. The implant direction may also be reversed such that the correction angle of the spinal column defined at least in part by the acute angle α of the intrabody implant may provide a kyphotic correction to a spinal column at the level of the single vertebral body V. The illustrative methods making use of the implant body of the present invention may provide a correction angle across multiple levels (such that the acute angles α of several intrabody implants <NUM> may provide a lordotic correction to a spinal column across <NUM> or more levels). The removing, providing, placing and closing steps disclosed herein may be repeated across two or more levels of the human spine to achieve an overall spinal correction across the two or more levels.

In some illustrative methods, the closing step described herein may further comprise securing the <NUM> at least partially separated portions V1, V2 of the vertebral body V about the implant <NUM> using an extradiscal stabilization system (which may include, for example, a rod <NUM> and pedicle screw <NUM>, <NUM> construct as shown generally in <FIG> and <FIG>. The pedicle screws <NUM>, <NUM> may be inserted into the pedicles of adjacent vertebral bodies V3, V4 and connected via rod <NUM> that may be shaped and/or bent by the surgeon to further reinforce the corrective angle sought as part of the surgical procedure. <FIG> shows a perspective view of a bi-lateral screw <NUM>, <NUM>, <NUM>, <NUM> and rod <NUM>, <NUM> construct that may also be used to reinforce the corrected spinal curvature using the various illustrative methods described here. Various screw and rod systems may be used for the reinforcement step, including but not limited to the SOLERA® and LEGACY® extradiscal stabilization systems offered by Medtronic® Spine.

Referring now to <FIG>, an intrabody implant <NUM> is disclosed for placement between at least <NUM> separated portions V1, V2 of a bony structure being a vertebral body such as a vertebral body V. The implant <NUM> may be formed in whole or in part from a variety of biocompatible materials suitable for long-term implantation. The implant <NUM> is formed of PEEK and comprises a coating of titanium applied to the first and second surface.

According to the various embodiments provided herein, the implant <NUM> comprises a first surface <NUM> configured for engaging a first V1 of the at least two separated portions of the bony structure being a vertebral body. The implant <NUM> further comprises a second surface <NUM>, disposed opposite the first surface <NUM>, and configured for engaging a second V2 of the at least two separated portions of the bony structure being a vertebral body. As shown in <FIG>, the first and second surfaces <NUM>, <NUM> may be disposed at an acute angle α relative to one another. The angle α may range widely from zero to <NUM> degrees. However, in some preferable embodiments the angle α may range from <NUM> to <NUM> degrees. According to the invention, the angle α ranges from <NUM> to <NUM> degrees.

As shown in <FIG>, the implant <NUM> may further comprise a wall <NUM> disposed between the first and second surfaces <NUM>, <NUM>. The wall <NUM> comprises an anterior portion <NUM> and a posterior portion <NUM>. As shown in <FIG>, the posterior portion <NUM> has a posterior height and the anterior portion <NUM> has an anterior height, wherein the posterior and anterior heights are unequal to form the preferably acute angle α between the first surface <NUM> and the second surface <NUM> of the implant <NUM>. In some embodiments, as shown in <FIG>, the posterior height may be less than the anterior height such that the angle α of the implant <NUM> introduces a lordotic angle between the first and second portions V1, V2 of the bony structure being a vertebral body V (see <FIG>, for example). Furthermore, as shown in <FIG>, the posterior portion <NUM> and/or anterior portion <NUM> of the implant may be provided with a convex profile between the first and second surfaces <NUM>, <NUM> to aid in the ease of insertion of the implant <NUM>. The profile may also, in alternate embodiments, be chamfered and/or provided with edge radii to allow for easier insertion of the implant <NUM> from either the posterior or anterior directions.

<FIG> shows a top view of an implant <NUM> according to one embodiment wherein the first and second surfaces <NUM>, <NUM> define an aperture <NUM> extending through the implant <NUM> to allow for bone growth through the implant <NUM> from the first portion V1 of the bony structure being a vertebral body V to the second portion V2 (see <FIG>, for example). The aperture <NUM> may also be packed with bone growth promoting material, including but not limited to bone allograft, bone xenograft, bone autograft, bone morphogenetic protein (BMP) and/or combinations thereof. Furthermore, as shown in <FIG>, the implant <NUM> may be formed in a shape that conforms to the anatomy of the human spine. For example, the posterior portion <NUM> of the wall <NUM> may comprise an outer concave surface configured to conform to a posterior anatomy of the bony structure being a vertebral body V. Furthermore, the anterior portion <NUM> of the wall <NUM> may comprise an outer convex surface configured to conform to an anterior anatomy of the bony structure being a vertebral body V.

Referring again to <FIG>, the implant <NUM> may include a width W extending substantially parallel to the anterior portion <NUM> and the posterior portion <NUM>. The width W of the implant <NUM> may be chosen to substantially fill the width of the vertebral body V or other bony structure where the intrabody is intended to be placed after osteotomy. For example, in some examples, the width W may be at least <NUM>. In other examples, the width W may be at least <NUM> (when used, for example, in the lower lumbar region). In other embodiments, the width W may be tailored for use in smaller vertebral bodies (for example, in smaller patients or in the upper thoracic or cervical spine). In some such examples, the width W may be in the range of <NUM>-<NUM> (or according to the invention, <NUM>-<NUM> in some preferable cervical and thoracic embodiments). The depth of the implant <NUM> may also vary accordingly (wherein the depth is measured perpendicular to the width W from the anterior portion <NUM> to the posterior portion <NUM>). In some examples, the depth may range from <NUM> to <NUM> (and according to the invention, from <NUM>-<NUM>).

As shown in <FIG>, the first surface <NUM> and second surface <NUM> of the implant <NUM> may further comprise a plurality of surface features <NUM> extending outward from the surfaces <NUM>, <NUM> to engage a complementary surface of the bony structure being a vertebral body V. For example, the surface features <NUM> may include, but are not limited to: ridges, teeth, pyramidal structures, roughened irregular projections and/or combinations thereof. The surface features <NUM> may be optimized in shape and/or directional orientation to resist the expulsion of the implant <NUM> from between the portions V1, V2 of the bony structure being a vertebral body when the patient applies weight forces to the spine during the course of standing or movement. For example, the surface features <NUM>, may comprise rows of teeth (see <FIG>) having a substantially right-triangular profile wherein the teeth are sloped upwards towards the anterior portion <NUM> of the wall <NUM> of the implant <NUM>. In other embodiments, the implant <NUM> may further comprise a coating applied to one or more of the surfaces <NUM>, <NUM> and/or the wall <NUM> to encourage bone growth onto the implant <NUM>. Such coatings may include, but are not limited to: gold, according to the invention titanium, hydroxyapatite (HA) and/or combinations thereof. The coatings may be applied with a roughened texture so as to provide a plurality of irregular projections that may serve as surface features <NUM> to also resist expulsion of the implant <NUM> after implantation. In other embodiments, the implant <NUM> may have substantially smooth surfaces <NUM>, <NUM> and wall <NUM> having no projections or surface features.

Claim 1:
An intrabody implant (<NUM>) adapted to be placed between at least <NUM> separated portions (V1, V2) of a single bony structure (V) being a vertebral body, the intrabody implant (<NUM>) comprising:
a first surface (<NUM>) configured for engaging a first (V1) of the at least two separated portions (V1, V2) of the bony structure (V);
a second surface (<NUM>), disposed opposite the first surface (<NUM>), and configured for engaging a second (V2) of the at least two separated portions (V1, V2) of the bony structure (V), the second surface (<NUM>) disposed at an acute angle (α) relative to the first surface (<NUM>);
a wall (<NUM>) disposed between the first and second surfaces (<NUM>, <NUM>), the wall comprising an anterior portion (<NUM>) and a posterior portion (<NUM>), the posterior portion (<NUM>) having a posterior height and the anterior portion (<NUM>) having an anterior height, the posterior and anterior heights being unequal to form the acute angle (α) between the first surface (<NUM>) and the second surface (<NUM>);
wherein the implant (<NUM>) is wedge-shaped with the first and second surfaces (<NUM>, <NUM>), in a side view of the implant (<NUM>),
- extending rectilinearly to define the acute angle (α) therebetween,
- extending at an acute angle relative to the anterior portion (<NUM>) of the wall (<NUM>), and
- extending at an obtuse angle relative to the posterior portion (<NUM>) of the wall (<NUM>),
wherein the acute angle (α) between the first and second surfaces (<NUM>, <NUM>) is between <NUM> degrees and <NUM> degrees, and
wherein the implant (<NUM>) includes a width (W) extending parallel to the anterior portion (<NUM>) and the posterior portion (<NUM>), and a depth measured perpendicular to the width (W) from the anterior portion (<NUM>) to the posterior portion (<NUM>),
characterized in that
the width (W) is in the range of <NUM>-<NUM>, and the depth is in the range from <NUM>-<NUM>,
the intrabody implant (<NUM>) is formed entirely of PEEK polymer, and
the intrabody implant (<NUM>) further comprises a coating of titanium applied to the first and second surfaces (<NUM>, <NUM>).