Vertebral fusion device and method for using same

An intervertebral fusion device includes a body having a proximal portion along a major axis of the body and a distal portion along the major axis, and supporting means at the distal portion. The supporting means supports vertebrae in a distracted position while the vertebrae fuse. At least one of the body and the supporting means has a height distinct from a width, whereby the body or supporting means can distract vertebrae, between which the body or the supporting means has been placed, by rotation of the body or the supporting means about the major axis. A method of fusing vertebrae includes the steps of inserting between two vertebrae an intervertebral fusion device and rotating the body or the supporting means, whereby the vertebrae are supported in a distracted position while the vertebrae fuse.

BACKGROUND OF THE INVENTION

Spine fusion procedures represent the state of the art treatment for intervertebral disc problems, which generally involve open surgery and the use of interbody fusion cages and spinal fixation systems to stabilize the fusion site.

Less invasive methods of performing interbody fusion have gained popularity in recent years due to deminished disruption of the body's tissues and lower blood loss during surgery, resulting in lower post-operative pain and faster recovery. Anterior lumbar interbody fusion (ALIF) procedures obviate the need to disrupt back muscles and liganients, but requires careful navigation around sensitive structures such as the aorta. Transforaminal lumbar interbody fusion (TLIF) procedures require only one incision made in the patient's back and involves placing a single fusion device obliquely into the disc space. Distraction of the disc space with subsequent decompression of nerve roots can be accomplished by rotating a device between the adjacent vertebrae. However, filling the space around the device with a material, e.g. bone graft, is difficult, time consuming and results in significant morbidity at the graft donor site.

Thus, there is a need for a method and a device that would minimize or overcome the above-referenced problems.

SUMMARY OF THE INVENTION

The present invention relates to a device that can be employed, after performing a discectomy or nucleotomy, to both distract the disc space and inject or insert supporting means into the distracted disc space.

In one embodiment, the present invention is an intervertebral fusion device, comprising (a) a body having a proximal portion along a major axis of the body and a distal portion along the major axis and (b) supporting means at the distal portion that support vertebrae in a distracted position while the vertebrae fuse. The body defines a conduit substantially parallel to the major axis and the supporting means define a conduit in fluid communication with the conduit defined by the body. At least a portion of the body or the supporting means has a height distinct from a width taken along a cross-section of the portion of the body or supporting means perpendicular to the major axis, whereby the portion of the body or supporting means can distract vertebrae, between which the portion of the body or the supporting means has been placed, by rotation of the body or the supporting means about the major axis.

In another embodiment, the present invention is a kit for providing fusion-promoting material comprising an intervertebral fusion device and a flowable osteogenic material selected from the group consisting of morsellized autograft, demineralized bone matrix, bone marrow aspirate, bone marrow concentrate, platelet-rich plasma, hyaluronic acid, collagen, calcium phosphate cements, and bioabsorbable polymers. In another embodiment, the flowable material also contains an added bone growth factor such as a bone morphogenic protein. The device includes (a) a body having a proximal portion along a major axis of the body and a distal portion along the major axis and (b) supporting means at the distal portion that support vertebrae in a distracted position while the vertebrae fuse. The body defines a conduit substantially parallel to the major axis and the supporting means define a conduit in fluid communication with the conduit defined by the body. At least a portion of the body or the supporting means has a height distinct from a width taken along a cross-section of the portion of the body or supporting means perpendicular to the major axis, whereby the portion of the body or supporting means can distract vertebrae, between which the portion of the body or the supporting means has been placed, by rotation of the body or the supporting means about the major axis.

In another embodiment, the present invention is a method of fusing vertebrae, comprising the steps of (a) inserting between two vertebrae an intervertebral fusion device, said device including a body and a supporting means and (b) rotating the body or the supporting means, whereby the vertebrae are supported in a distracted position while the vertebrae fuse, thereby fusing the vertebrae. The body has a proximal portion along a major axis of the body and a distal portion along the major axis and defines a conduit substantially parallel to the major axis. The supporting means at the distal portion of the body supports vertebrae in a distracted position while the vertebrae fuse. The supporting means define a conduit in fluid communication with the conduit defined by the body. At least a portion of the body or the supporting means has a height distinct from a width taken along a cross-section of the portion of the body or supporting means perpendicular to the major axis, whereby the portion of the body or supporting means can distract vertebrae, between which the portion of the body or the supporting means has been placed, by rotation of the body or the supporting means about the major axis.

The present invention has numerous advantages including simultaneous use as a spreader to distract adjacent vertebrae and to surgically implant supporting means. Also, the present invention can substantially restore natural lordosis, kyphosis and/or disk height. The present invention also enables introduction of flowable materials into disk space without subjecting the injected material to compressive forces, thereby permitting the injected material to set, if necessary, prior to applying significant compressive force.

DETAILED DESCRIPTION OF THE INVENTION

Devices of the Invention

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

The present invention relates to a vertebral fusion device for simultaneously distracting two adjacent vertebral bodies and delivering a flowable material into a disk space. As used herein, the term “vertebral fusion” refers to a medical procedure that results in maintaining separation between vertebrae. In one embodiment, vertebral fusion provides for bony ingrowth that fixes two adjacent vertebrae in a desired, for example, distracted and/or angulated, position.

In a preferred embodiment, a natural angle between two adjacent vertebral plates is replicated by fusing the two adjacent vertebrae. As used herein, the “natural angle” refers either to natural lordosis or to natural kyphosis. In one embodiment, a natural lordosis is replicated or restored. As used herein, the term “natural lordosis” refers to a natural angle between two adjacent vertebral plates within the lumbar or cervical spine segments wherein the distance between the anterior portions of the two adjacent vertebral plates is not smaller than the distance between the posterior portions of the two adjacent vertebral plates. In another embodiment, a natural kyphosis is replicated or restored. As used herein, the term “natural kyphosis” refers to a natural angle between two adjacent vertebral plates within the thoracic spine segment wherein the distance between the anterior portions of the two adjacent vertebral plates is not greater than the distance between the posterior portions of the two adjacent vertebral plates. In another embodiment of vertebral fusion, a fusion means maintains the separation between the vertebrae.

Subsequent to discectomy or nucleotomy, a device of the present invention can be used to distract the adjacent vertebrae, inject a flowable material, for example a fusion-promoting composition, in the intervertebral space and maintain the distracted vertebrae in the distracted position. Additionally, the present invention can be used to at least partially restore natural angle or disk space.

For the purposes of the present invention, the “distal portion” of the device is that portion that penetrates the annulus fibrosis, while the “proximal portion” of the device is that portion that remains outside the annulus fibrosis.

Referring toFIG. 1(a), in one embodiment the present invention is an assembly that includes cannula12and device20. Cannula12further includes proximal outlet14, distal outlet16and hilt18. Device20, having proximal portion22and distal portion24along major axis26, includes stopper28at proximal portion22, attached to central section30that spans proximal and distal portions22and24of device20, clamp32at distal portion24, attached to central section30and, preferably, connector36, attached to clamp32.

For the purposes of the present invention, the portion of device20that includes stopper28, central section30, clamp32and, preferably, connector36is referred to herein as the “body” of the device. The terms “major axis,” labeled26inFIG. 1(a), and “major axis of the body,” are used interchangeably herein.

Device20preferably has conduit34, substantially parallel to major axis26and defined by the body of the device. Conduit34has inlet38, located at proximal portion22of device20, preferably in stopper28, and outlet40, located at a distal portion of clamp32or, preferably, at connector36.

Cannula12, shown schematically inFIG. 1(b), preferably has a rectangular cross-section taken perpendicular to major axis26. Clamp32and a distal portion of central section30of device20are shown inFIG. 1(c). Preferably, central section30and connector36have circular cross-sections taken perpendicular to major axis26.

Device20further includes supporting means50at the distal portion22for supporting vertebrae in a distracted position while the vertebrae fuse. Referring toFIG. 1(c) andFIG. 1(d), at least one of the clamp32and the supporting means50has a height H distinct from a width W taken along a cross-section of clamp32or supporting means50perpendicular to major axis26. As the result, clamp32or supporting means50can distract vertebrae, between which clamp32or supporting means50has been placed, by rotation of device20, and thereby clamp32or supporting means50, about major axis26. Upon placing clamp32or supporting means50of the present invention between the adjacent vertebrae, a flowable material can be injected through conduit34into the disk space.

Referring toFIG. 1(a), in a preferred embodiment, supporting means50includes supporting means conduit52having an inlet53and at least one outlet54. Preferably, there are two or more outlets54. Even more preferably, and now referring toFIG. 1(e), supporting means50have multiple outlets54. Inlet53of supporting means conduit52is preferably in fluid communication with outlet40of conduit34. In one embodiment, supporting means50is an integral part of clamp32. In a preferred embodiment, supporting means50are detachably connected to clamp32and connector36.

In one embodiment, inlet38includes a connection means (not shown) to an injection means (not shown). Suitable connection means include a rubber or plastic hose or tube. Suitable injection means include syringe and a pump. Preferably, the injection means is a syringe.

In some embodiments, supporting means50is selected from the group consisting of a cage, a balloon and a ramp. In a particularly preferred embodiment, the supporting means is a cage60, depicted in a perspective view inFIG. 2(a) and, as a non-limiting example, inFIGS. 1(a), (d) and (e). Preferably, cage60is detachably connected to clamp32and, more preferably, to connector36. In this embodiment, cage60defines supporting means conduit52that is in fluid communication with conduit34defined by the body of device20. Referring toFIG. 2(a), preferably, cage60has a height H distinct from a width W taken along a cross-section of cage60perpendicular to major axis26. As the result, cage60can distract vertebrae, between which it has been placed, by rotation of device20, and thereby cage60, about major axis26. Preferably, cage60substantially maintains natural angle between the distracted vertebrae. In a particularly preferred embodiment, cage60substantially maintains a natural angle between the distracted vertebrae upon detachment of clamp32or connector36from cage60.

Referring toFIG. 2(b), lateral views of two embodiments of cage60are shown. In these embodiments, cage60has an upper bearing surface62, a lower bearing surface64and lateral surfaces66. The upper and lower surfaces define a non-zero angle α, thereby providing an anterior-posterior angle to the distracted disc space. Preferably, the angle α is between about 5 and about 15 degrees. Alternatively, the angle α defined by the upper and the lower bearing surfaces is between about −5 and about −15 degrees. When inserted into the lumbar or cervical spine, the portion of the supporting means having the greater height is preferably facing the anterior side, thus providing lordosis to the spine segment. When inserted into the thoracic spine, the portion of the supporting means having the greater height is preferably facing the posterior side, thus providing kyphosis to the spine segment.

In one preferred embodiment, the supporting member is inserted into the disc space through a transforaminal posterior approach, which causes the device to lie at an angle to the sagittal plane. In this case, the angle, defined by the upper and lower bearing surfaces, is defined along the saggital plane, therefore the supporting member is angled both along the major axis and transversely to the major axis.

Referring toFIG. 2(c), in one embodiment, cage60has at least one of the bearing surfaces62and64having a convex shape substantially adapted to match the contour of the vertebral endplates92and94.

In one embodiment, supporting means50is cage70, depicted in perspective view inFIG. 3(a) and, in plan view, inFIG. 3(b). Cage70includes frame72and at least two expandable balloons74, connected to frame72. Cage70defines therewithin a supporting means conduit52. Supporting means conduit52is in fluid communication with balloons74and with conduit34defined by the body of device20. Preferably, cage70is detachably connected to clamp32and, more preferably, to connector36. Preferably, cage70has a height H distinct from a width W taken along a cross-section of cage70perpendicular to major axis26. As the result, cage70can distract vertebrae, between which it has been placed, by rotation of device20, and thereby cage70, about major axis26. Preferably, cage70substantially maintains a natural angle between the distracted vertebrae. In a particularly preferred embodiment, cage70substantially maintains a natural angle between the distracted vertebrae upon detachment of clamp32or connector36from cage70.

In a preferred embodiment depicted inFIG. 3(c), balloons74expand substantially in the lateral direction indicated by arrow A. Preferably, balloons74have multiple outlets75located on upper and lower balloon surfaces76and77. Upon distracting the adjacent vertebrae, a flowable material can be injected through conduit34and52into balloons74. The flowable material is allowed to come in contact with the adjacent vertebrae through outlets75. In this embodiment, the balloon is substantially semi-permeable, whereby leakage outside of the disc space is prevented, while allowing direct contact of the flowable material with the vertebral body endplates.

In one embodiment, depicted in perspective view inFIG. 4(a) and, in plan view, inFIG. 4(b), supporting means50is an expandable balloon80. Balloon80is in fluid communication with conduit34defined by the body of device20. Preferably, balloon80is detachably connected to clamp32and, more preferably, to connector36.

Referring toFIG. 4(a), in this embodiment, clamp32and balloon80, subsequent to expansion, have a height H distinct from a width W taken along a cross-section of clamp32or balloon80perpendicular to major axis26. As the result, clamp32can distract vertebrae, between which clamp32has been placed, by rotation of device20, and thereby clamp32about major axis26. Upon distracting the adjacent vertebrae, a flowable, preferably hardenable, material can be injected through conduit34into balloon80.

In one embodiment, expanded balloon80substantially maintains natural angle between the distracted vertebrae. In a preferred embodiment, expanded balloon80substantially maintains natural angle between the distracted vertebrae upon detachment of clamp32or connector36from expanded balloon80.

Materials Employed by Devices of the Invention

The device can be made of materials typically selected for use in surgical instruments and implants, such as stainless steel, titanium, titanium alloys (Ti-6Al-4V), cobalt-chrome alloys. Preferably, the entire device is sterile.

In one embodiment, the supporting means50includes at least one material selected from the group consisting cortical bone graft, bioabsorbable polymer such as poly(lactic acid), poly(glycolic acid), polydioxanone, polyhydroxybutyrate, polyhydroxyvalerate, poly(propylene fumarate), polyoxaesters, amino acid-derived polycarbonates, biodegradable polyurethanes and their copolymers, and non-bioabsorbable polymer such as ether-ketone polymers (polyetheretherketone), poly(ethylene terephthalate), poysulfone, polypropylene, and nylon. These materials may be reinforced with additional materials known in the art, such as carbon fibers, glass fibers, hydroxyapatite fibers or particles.

In one embodiment, the devices of the invention include at least one balloon. In one embodiment, at least one balloon provides relative containment of the flowable material during injection, thereby preventing leakage outside of the disc space. In a preferred embodiment described above, at least one balloon is semi-permeable, thereby preventing leakage outside of the disc space, while allowing direct contact of the flowable material with the vertebral body endplates. In another embodiment, the balloon comprises a biodegradable polymer having a high rate of degradation that would allow the flowable material to contact the vertebral endplates following degradation. Examples include low-molecular weight polymers of lactic and glycolic acid, modified lactic and glycolic acid polymers such as hydroxylated poly(glycolic-co-lactic acid, collagen, and oxidized regenerated cellulose.

In another embodiment, the devices of the invention include at least one balloon that further includes a material selected from the group consisting of polyurethanes, polyolefin copolymers, polyethylene, polycarbonate, polyethylene terephthalate, ether-ketone polymers, woven fibers, non-woven fibers, fabrics and metal mesh.

Flowable materials can include a material that hardens into a structure capable of supporting the loads typically experienced by a intervertebral disc. In one embodiment, the flowable material hardens into a porous scaffold into which bone can grow from the surroundings. In another embodiment, the flowable material hardens into a cement that can induce bone growth.

A kit for providing a fusion-promoting material comprising the device of the present invention and a flowable material.

Methods of the Invention

In one embodiment, and referring back toFIGS. 1(a) and (b), the present invention is a method of fusing vertebrae.

The method includes a step of inserting between two vertebrae an intervertebral fusion device20, said device having a proximal portion22and distal portion24along major axis26, a stopper28at proximal portion22connected to a central section30, that spans proximal and distal portions22and24of device20, clamp32at distal portion24, connected to central section30and, preferably, connector36, connected to clamp32.

For the purposes of the present invention, the portion of device20that includes stopper28, central section30, clamp32and, preferably, connector36is referred to herein as the “body” of the device. The terms “major axis,” labeled26inFIG. 1(a), and “major axis of the body,” are used interchangeably herein.

The intervertebral fusion device further includes supporting means50at the distal portion24for supporting vertebrae in a distracted position while the vertebrae fuse, wherein at least one of clamp32and the supporting means50has a height H distinct from a width W taken along a cross-section of clamp32or supporting means50perpendicular to major axis26, whereby clamp32or supporting means50can distract vertebrae, between which clamp32or supporting means50has been placed, by rotation of device20or supporting means50about the major axis26and further wherein the supporting means define a conduit substantially parallel to major axis.

The method further includes the step of rotating device20or supporting means50, whereby the vertebrae are supported in a distracted position while the vertebrae fuse, thereby fusing the vertebrae.

According to the method of the invention, supporting means50is inserted between the vertebrae. Preferably, either supporting means50or clamp32has a height H distinct from a width W taken along a cross-section perpendicular to major axis26. As the result, rotation of device20, and thereby of supporting means50distracts the vertebrae. Preferably, rotation of device20, and thereby of supporting means50at least partially restores natural angle between the vertebrae.

In a preferred embodiment, at least a portion of an intervertebral disk between said vertebrae is removed resulting in formation of an intervertebral space. The device of the present invention can be used immediately after a discectomy or a nucleotomy. In performing the discectomy or a nucleotomy, the surgeon typically makes a small (˜5 mm) hole in the annulus fibrosis through which the nucleus pulposus is removed.

Preferably, the surgeon makes a device entry hole in the annulus fibrosis. The device entry hole is typically made by either making a second hole in the annulus fibrosis larger than the hole through which the nucleotomy is performed or, preferably, by enlarging the hole through which the nucleotomy is performed.

The method of the present invention can further include the step of removing at least a portion of an intervertebral disk between said vertebrae to thereby form an intervertebral space. The intervertebral space can at least partially be filled with at least one member of the group consisting of autologous bone graft, allograft, demineralized bone matrix, tricalcium phosphate granules, bioabsorbable polymer and non-bioabsorbable polymer.

The method of the present invention can further include the step of directing at least one member selected from the group consisting of morsellized autograft, demineralized bone matrix, bone marrow aspirate, bone marrow concentrate, platelet-rich plasma, hyaluronic acid, collagen, calcium phosphate cements, and bioabsorbable polymers, into supporting means conduit52defined the supporting means50. In one embodiment, the flowable material is delivered into the disk space through supporting means conduit52and outlets54. In one embodiment, supporting means50is an integral part of clamp32. In this embodiment, the surgeon preferably allows the material to at least partially cure within the disc space to a point where the at least partially cured material can withstand the, compressive forces of the spine without leaking into the spinal canal, then the clamp and supporting means are removed. In another embodiment, supporting means50is detachably connected to clamp32or connector36. In this embodiment, the surgeon can remove device20from the intervertebral space and leave supporting means in said space.

In one embodiment, the flowable material is delivered into balloon80. In one embodiment, the surgeon preferably allows the material to at least partially cure within the disc space to a point where the at least partially cured material can withstand the compressive forces of the spine. At this time, the surgeon can remove device20from the patient, leaving supporting means50that includes balloon80in the intervertebral space.

In another embodiment, the flowable material is delivered into balloons74of cage70. In this embodiment, cage70is detachably connected to clamp32or connector36. In this embodiment, the surgeon can remove device20from the intervertebral space and leave cage70in said space prior to allowing the flowable material to cure.

As a non-limiting example, the deployment of the cage60will be illustrated below.

Referring toFIGS. 5(a) and5(b), according to the method of the present invention, the surgeon advances assembly10through an incision in the annulus fibrosis, and follows by insertion of cage60between lower vertebra90and the upper vertebra94(FIG. 5(b)) in a direction shown by arrow A as depicted inFIG. 5(a). Referring toFIG. 5(b), the initial orientation of cage60is such that the lateral surfaces66are essentially parallel to lower endplate92and upper endplate96.FIG. 5(b) shows the position assumed by cage60in the intervertebral space subsequent to the insertion (for clarity, only cage60is shown).

Next, now referring toFIGS. 5(c) and5(d), the surgeon rotates device20(not shown), including cage60, by about 90° (as shown by arrow B inFIG. 5(a)) to the final orientation whereby the bearing surfaces64and62are in contact with lower endplate92and upper endplate96(FIG. 5(d)) respectively.

Since, in this example, cage60has its height H greater than its width W (seeFIG. 5(c)), the rotation achieves the desired distraction of the vertebral bodies92and94.

Next, the intervertebral space (the space between vertebrae90and94) is filled by directing a flowable, fusion-promoting material through conduit34, supporting means conduit52and supporting means conduit outlet53. The surgeon then allows the material to begin to cure within the disc space to a point where the at least partially cured material can withstand the compressive forces of the spine without leaking into the spinal canal. At this time, the surgeon can remove device20and cage60from the patient. Alternatively, when using an embodiment of device20wherein cage60is detachably connected to clamp32or connector36, the surgeon, subsequent to filling the intervertebral space with a flowable, fusion-promoting material, detaches cage60from clamp36and removes device20without cage60from the patient. In this embodiment, it is not necessary to allow the material to begin to cure.

EQUIVALENTS