Methods and apparatus for accessing and treating the facet joint

Abstract

Methods and systems are disclosed for accessing and treating the interior of the facet joint for vertebral distraction and immobilization. The systems include a number of tools that facilitate access to the facet joint, distraction of the articulating decortication of the articulating surfaces, and delivery of implants and agents into the facet joint for fusion.

Claims

1. A method of accessing a facet joint to prepare the joint for delivery of an implant between a first and second articulating subchondral surface of the facet joint, the method comprising: accessing the facet joint from a posterior-lateral approach with a facet access tool, the facet access tool comprising: an elongate handle having a proximal end and a distal end; and a capsule piercing portion disposed at the distal end of the handle, the capsule piercing portion comprising a flat leading edge; and decorticating the facet joint with a decortication apparatus to prepare the joint for delivery of an implant between the first and second articulating subchondral surfaces of the facet joint, wherein the decortication apparatus comprises a flat, spatula shaped rasp configured to decorticate at least one of the articulating surfaces.

2. The method of claim 1, wherein the decortication apparatus further comprises a shaft attached to the rasp and includes a distal, beveled surface.

3. The method of claim 1, wherein the decortication apparatus comprises a flat device configured to decorticate at least one of the articulating surfaces.

4. The method of claim 1, wherein the implant comprises bone allograft.

5. A method of preparing a facet joint for delivery of an implant between the first and second articulating subchondral surfaces of the facet joint from a posterior-lateral approach, the method comprising: accessing the facet joint with a facet access tool; and decorticating the facet joint with the decortication apparatus to prepare the facet joint for an implant, the decortication apparatus comprising a flat, spatula shaped rasp with a distal beveled surface and configured to decorticate at least one articulating surface, the decortication apparatus further comprising a shaft attached to the rasp.

6. The method of claim 5, wherein the implant comprises bone allograft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:

(2) FIG. 1 is a lateral view of two cervical vertebral members in a stenosed condition.

(3) FIG. 2 is a view of a traditional introducer needle being inserted into the facet joint of the vertebral members.

(4) FIGS. 3A-3H include several views of a facet access tool according to certain embodiments.

(5) FIG. 4 is a schematic lateral view of the facet access tool of FIGS. 3A-3H positioned at the facet joint capsule of two cervical vertebral members.

(6) FIG. 5 is a schematic lateral view of the facet access tool of FIGS. 3A-3H piercing and being manipulated within the facet joint capsule, according to certain embodiments.

(7) FIG. 6 is another view of the of the facet access tool of FIGS. 3A-3H piercing the facet joint capsule, according to certain embodiments.

(8) FIG. 7 is a view of the slit-shaped aperture created by the facet access tool of FIGS. 3A-3H.

(9) FIGS. 8A-8H include several views of a facet introducer, according to certain embodiments.

(10) FIG. 9 is a schematic lateral view of the introducer tool of FIGS. 8A-8H being manipulated within the facet joint capsule, according to certain embodiments.

(11) FIG. 10 is a schematic lateral view of the facet blade being used to guide the introducer tool of FIGS. 8A-8H into the joint capsule, according to certain embodiments.

(12) FIGS. 11A-11I include several views of a facet distraction device, according to certain embodiments.

(13) FIGS. 12A-H include several views of a detachable wedge used with the facet distraction device of FIGS. 11A-11I.

(14) FIGS. 13A-13G include several views of an alternative facet distraction device, according to certain embodiments.

(15) FIGS. 14A-14I include several views of a facet decortication tool, according to certain embodiments.

(16) FIGS. 15A-15G include several views of a facet delivery tool for delivering an injectable biomaterial, according to certain embodiments.

(17) FIGS. 16A-16I include several views of a facet inflatable membrane introducer, according to certain embodiments.

DETAILED DESCRIPTION OF THE INVENTION

(18) Referring more specifically to the drawings, for illustrative purposes, one embodiment of an apparatus is generally shown in FIG. 3A through FIG. 16. It will be appreciated that the apparatus may vary as to configuration and as to details of the parts, and that the method may vary as to the specific steps and sequence, without departing from the basic concepts as disclosed herein.

(19) FIG. 1 illustrates a simplified lateral view of a portion of the cervical spine 10. The basic biomechanical unit or motion segment of the spine consists of two adjacent vertebrae 12 and 14 and the three joint articular complex through which they move and are constrained in relation to one another. The spine articulations generally consist of an intervertebral disc 26 located between the vertebral bodies 26 of adjacent vertebrae 12, 14, and two facet joints 16 symmetrically located laterally from the sagittal plane at the posterior end of the vertebral bodies 26.

(20) The facet joints 16 allow constrained spinal motion, while protecting the contained neural structures. From a kinematic viewpoint, the intervertebral facet joints 16 are highly constrained sliding planar articulations, lubricated by synovial fluid contained within the facet joint capsule 30. In the cervical spine, the geometry of the cervical vertebral bodies provides a high degree of protection for the neural elements by limiting normal motion of the spine to within physiologic limits. The upward inclination of the superior articular surfaces of the facet joints allows for considerable flexion and extension, as well as for lateral mobility.

(21) The distraction, preparation and delivery devices disclosed herein facilitate minimally invasive or percutaneous surgical access, distraction and implant delivery to the facet joint, which is advantageous due to reduced surgical time, reduced recovery time, and improved surgical outcome. Each vertebral segment comprises a spinous process 34 located at the posterior end of the vertebrae, with the vertebral body located anteriorly. Each vertebra comprises an inferior articular (or transverse) process 35 and the superior articular process 37 that form four posterior articulating, e.g. opposing subchondral, surfaces: two superior facets 18 and two inferior facets 16. The inferior facet 18 from the inferior articular process 35 of the upper vertebra 12 and the superior facet from the superior articular process 37 of the lower vertebra 14 form the facet joint 16 on each lateral side of the spine.

(22) Located medial to the articular processes 37 and vertebral bodies 26 is an aperture, or intervertebral foramina 38, that serves as a nerve root canal for the spinal nerves and vessels that transmit signals from the spinal chord to respective locations in the body.

(23) Each facet joint 16 is covered by a dense, elastic articular capsule 28, which is attached just beyond the margins of the articular facets 18, 22. The inside of the capsule is lined by a synovial membrane (not shown), which secretes synovial fluid for lubricating the facet joint. The exterior of the joint capsule is surrounded by a capsular ligament (not shown), which may be temporarily repositioned to give access for insertion of the extendable implant of the present invention, described in further detail below. Thus, from a posterior-lateral approach, access to the facet joint 16 is relatively straightforward and well prescribed, as compared to other regions of the spine, which present a higher likelihood of trauma and risk of permanent damage.

(24) It should also be noted that FIG. 1 depicts cervical foraminal stenosis, e.g. loss of height between the adjacent vertebrae 12, 14. As a result of disc 36 herniation and corresponding height loss, the nerve root canal 38, or intervertebral foraminal height, having a value H.sub.s, is narrowed relative to that of healthy anatomy. This narrowing of the foraminal height H.sub.s often leads to compression of the spinal cord and nerve roots (not shown), causing radicular symptoms.

(25) As a result of the stenosed foraminal height H.sub.s, the height of the facet joint 16, or distance between subchondral articulating surfaces 18 and 22, is also narrowed, (shown as value D.sub.s in FIG. 1). This may pose complications in the facet joint 16 as well. However, because the height of the disc will be relatively fixed, an increase in the facet joint height will also have a corresponding increase in foraminal height, as described in greater detail below.

(26) FIG. 2 illustrates a typical procedure for accessing the facet joint using a standard discography introducer needle 44 to access the facet joint. Because the gap or cavity 30 bound between subchondral articulating surfaces 18 and 22 is generally planar, the cylindrical needle 44 may be difficult to navigate into the capsule 30. Generally precise alignment and orientation of the needle 44 with the subchondral surface 18 and 22 may be used for the needle to enter the cavity 30. Thus, the shape and size constraints of the facet joint 16 make typical cylindrical needles 44 difficult to predictably and consistently gain access to the facet joint capsule.

(27) FIGS. 3A-16 show a system and method of the present invention for performing a minimally invasive procedure configured to distract one or more of the facet joints 16 of vertebrae 12, 14, thereby increasing the dimension of the neural foramen while retaining facet joint mobility. One of the major advantages of minimally invasive surgery is the ability to perform the procedure with minimal tissue trauma. Television image intensifier fluoroscopy may be used to provide guidance for surgeon placement of instrumentation and implants precisely to the desired anatomic target in the facet joint 16. The radiographic landmarks are well taught and the relative procedural difficulty of this technique is low.

(28) FIGS. 3A-3H illustrate a facet access tool 100 in accordance with certain embodiments. Tool 100 comprises an elongate handle having a flat cutting blade 112 on its distal end 102. The blade 112 generally comprises a straight, flat (i.e. planar), leading edge 110 at distal tip 102 that is sharpened to allow for piercing of the facet joint capsule 28. Although the leading edge 110 is shown as a straight-line surface when viewed from above in FIG. 3B, it is appreciated that different shapes may also be utilized, (e.g. arcuate, triangular, etc.)

(29) The blade 110 is coupled to shaft 108 that is received inside a central channel 116 running axially down handle 106. The shaft and blade protrude distally from the handle 106 so that flat surface 114 running along the bottom of the blade 112 is exposed. The flat surface 114 facilitates introduction and cooperation of additional instruments used for the procedure, discussed in further detail below.

(30) The shaft 108 has a beveled surface 118 that terminates at a point on the distal tip 102 of blade 112. As will be described in further detail below, the beveled surface 118 allows the blade 112 to access into the facet joint from sub-optimal angles of entry, and wedge the blade 112 into the joint for treatment.

(31) It is appreciated that blade 112 may be a separable from shaft 108 and joined with an adhesive, fastener or other securing means. Alternatively blade 112 and shaft 108 may comprise one contiguous or integral piece of material. The blade and shaft may comprise a hardened metal, such as stainless steel or titanium.

(32) The blade 112 and shaft 108 correspondingly have a D-shaped cross-section. Accordingly, chamber 116 of handle 106 also has a D-shaped cross-section, and is sized to receive shaft 108 and blade 112 with a snug fit. Handle 106 may comprise a plastic or similar polymer that is extruded, molded, or heat-shrunk in shape.

(33) FIG. 4 illustrates lateral views of facet access tool 100 positioned at the facet joint 16. According to the method of the present invention, the blade 112 is positioned at the desired location facet joint capsule 28 and then pushed into the capsule to generate an opening 32. FIG. 5 shows the access tool 100 manipulated in the facet cavity 30 through the opening 32 in the capsule wall 28.

(34) FIGS. 6 and 7 illustrate a postero-lateral view of the incision created by the access tool. As seen in FIG. 7 a slit-like opening 32 is generated that runs generally parallel to the facet joint articular surfaces 18, 22.

(35) Once we have gained access to the facet joint cavity 30 with the cutting blade of the facet access tool 100, an introducer 150 may be inserted into the joint. The introducer 150, illustrated in FIG. 8, comprises a handle 164 at its proximal end, and a malleable “spatula” shaped tip 154 at its distal end 152.

(36) The tip 154 generally comprises a straight, flat leading edge 110 at distal end 152. Although the leading edge 152 is shown as a straight-line surface when viewed from above in FIG. 8A, it is appreciated that different shapes may also be utilized, (e.g. arcuate, triangular, etc.)

(37) The tip 254 is coupled to shaft 158 that is received within a D-shaped opening channel 168 of the handle 156. The shaft 158 and tip 154 protrude distally from the handle 156 so that flat surface 160 running along the bottom of the tip and shaft is exposed. The shaft 158 has a beveled surface 162 that terminates at a point proximal to the distal tip end 152 of tip 154.

(38) The malleable and thin planar shape of the “spatula” tip 154 and beveled shaft 158 allow for suboptimal entry angles and compensates for the narrow spacing of the facet joint. In the method of the present invention, the tip 154 is inserted into the opening 32 created by the facet access tool 100. The flat, thin cross-section of tip 154 is configured to easily slide into thin, planar cavity 30 of the facet joint 30.

(39) As shown in FIG. 9, the tip 154 of introducer is malleable so that it bends into the cavity 30 if introduced from a sub optimal angle. This, along with the beveled surface 162, allows the blade introducer 150 to access into the facet joint from sub-optimal angles of entry, and wedge or manipulate the introducer 150 into the proper orientation in the joint 16 for treatment.

(40) The introducer 150 may be inserted into the cavity 30 after the access blade 100 has been removed, or may be inserted while the access blade 100 is still in place, essentially using the access blade to guide the introducer 150 by sliding the flat bottom surface 160 along the bottom surface 114 of the access blade, as shown in FIG. 10.

(41) In a similar fashion as illustrated in FIG. 10 with the access blade 100, the flat tip 154 of the introducer is also configured to provide a point of entry for later devices used in the surgical method of the present invention, e.g. to enable distraction, decortication, decompression, and fusion of the facet joint 16.

(42) With proper access and orientation of the instruments in the facet joint 16, the articular surfaces 18 and 22 may be distracted to increase the distance D.sub.s. Distraction of the joint 16 may be accomplished via a number of methods, including use of an inflatable membrane such as that disclosed in U.S. patent application Ser. No. 11/618,619 filed on Dec. 29, 2006, herein incorporated by reference in its entirety.

(43) Referring now to FIGS. 11A-11I and 12A-12H, distraction may be achieved via a wedge-inserter 170. The wedge inserter 170 comprises an elongate handle 178 at its proximal end 180 and detachable wedge-shaped tip 172 disposed on shaft 174 that is encased, at least proximally, within the handle 178.

(44) The detachable tip 172, further illustrated in FIGS. 12A-12H, converges to a nipple 176 at the distal extremity via beveled surfaces 182 and lateral arcuate surfaces 184. The detachable tip 172 has a keyed receiving hole 186 for attaching the tip 172 to the shaft 174.

(45) The upper and lower beveled surfaces 182 converge to nipple 176 from a box shaped platform defined by lower and upper parallel distraction surfaces 188, and 190. The distance between the lower and upper distraction surfaces 188, and 190 sets the thickness T of the wedge.

(46) The inserter 170 may be directed into to the facet joint cavity 30 with guidance from sliding it along introducer 150. When inserted into the cavity 30, the inserter generates an outward compressive force on the subchondral surfaces 18 and 22 to increase the distance between them to a desired treatment or nominal value D.sub.T. As shown in FIGS. 12B-12D, a set of tips 192, 194 and 196, all having a different thickness T, may be used in series so that the joint is progressively distracted. The final thickness T will correspond to the treatment or nominal value D.sub.T.

(47) This distraction of walls 18 and 22 correspondingly increases the height of the intervertebral foramin to a treatment or nominal value H.sub.T. The value of D.sub.T, and resulting increase in H.sub.T may be predetermined by the surgeon prior to the surgery based on pre-op analysis of the patient's condition and anatomy, and/or may also be iteratively devised by patient feedback of symptom improvement during the procedure.

(48) Referring now to FIGS. 13A-13G, distraction may also be achieved via duck-billed distraction device 200. The duckbill comprises an upper pivoting member 204 and lower pivoting member 202 mounted to a tube 214 at hinge 206. A rasp 208 is mounted on shaft 220 that is slideably received within the tube 214.

(49) The distal tips 210 of the pivoting members 202, 204 are configured to collapse down over rasp 208 to facilitate entry of the duckbill into the facet joint cavity 30. Correspondingly, the proximal ends 212 of the pivoting members 202, 204 expand outward from tube 214. Once properly positioned within the cavity 30, the proximal ends of the pivoting members 202, 204 (which are in an expanded configuration), can be manually pressed inward toward the shaft 214. This activation causes the duckbill to expand at distal tips 210, and distract the facet joint 16.

(50) With the facet joint surfaces 18, 22 distracted, the rasp 232 may be articulated distally outward from the duckbill and on to the facet surfaces 18, 22. The rasp 208 may be reciprocated back and forth within the tube 214 (via manual manipulation of the proximal end of shaft 220), thereby decorticating (by sanding or grating the surface) the surfaces in preparation for fusion.

(51) FIGS. 14A-14I illustrate a standalone decorticator 230. Decorticator 230 comprises a flat, flexible spatula-shaped rasp 232 at its distal end 236. The rasp 232 is coupled to shaft 238 that is received inside a central channel running axially down handle 246. The shaft and rasp protrude distally from the handle 246 so that flat surface 242 running along the bottom of the rasp 232 is exposed. The flat surface 242 facilitates introduction and cooperation with the introducer 150 described above.

(52) The shaft 238 has a beveled surface 240 that terminates at a point proximal to the distal tip 236 of the rasp 232. The thin, flexible shape allows the rasp to bend and access into the facet joint from sub-optimal angles of entry. The rasp may have one or more surfaces comprise a plurality of teeth 234 configured to grate down the hard cortical surface of the opposing facet joint surfaces 18, 22.

(53) Alternative decorticating devices may include a flat device with an aggressive cutting surface that is rolled to achieve roughening of the facet surface (not shown), and a device with two opposing rasp surfaces that articulate in a lateral motion through a “scissor like” activation feature. In such a configuration, the two blades of the scissors have flat upper and lower roughened surfaces that would simultaneously decorticate the opposing subchondral surfaces by remote manipulation of the blades. In other embodiments, decorticating devices may take the form of an abraded shaft and decorticating may be performed by rolling the device. In yet other embodiments, decorticating device may take the form of a file mechanism and decorticating may be performed with a back and forth filing motion, where the decorticating device is positioned and actuated using floss.

(54) With the facet joint 16 distracted and decorticated, the method of the present invention includes an embodiment where a specifically shaped piece of structural bone allograft (not shown) is then inserted into the space of distraction between the opposing facet joint surfaces. The bone allograft may be one of a series or kit of bone allograft having a predetermined shape and size (e.g. be sized in thickness that vary by small increments). The bone allograft may then be further shaped by the physician to have a custom size and shape correlating to the specific anatomy of the patient to be treated.

(55) The bone allograft is further supplemented with an injectable biomaterial such as bone morphogenic protein (BMP) to supplement the fusion potential at this level. FIGS. 15A-15G illustrate an injection device 260 for injecting BMP or like substances in accordance with the present invention. In some embodiments, the injectable biomaterial is used alone without a bone allograft. In either case, the injectable biomaterial may take the form of BMP as mentioned or other injectable biomaterials such as, but not limited to OP1, bonegraft, stem cells, bone cement (PMMA), or other injectable biomaterials now known or later developed.

(56) Device 260 includes an elongate handle 268 having a flat cutting blade 264 on its distal end 262. The blade 264 generally comprises a straight, flat (i.e. planar), leading edge at distal tip 262. Although the leading edge 262 is shown as a straight-line surface when viewed from above in FIG. 15C, it is appreciated that different shapes may also be utilized, (e.g. arcuate, triangular, etc.)

(57) The blade 264 is coupled to shaft 272 that is received inside a central channel running axially down handle 268. The shaft and blade protrude distally from the handle 268 so that flat surface 266 running along the bottom of the blade 262 is exposed. The flat surface 266 facilitates introduction and cooperation with additional instruments such as introducer 150.

(58) The shaft 272 has a beveled surface 274 that terminates at a point on the distal tip 262 of blade 264. The beveled surface 274 allows the blade 112 to access into the facet joint from sub-optimal angles of entry, and wedge the blade into the joint for treatment.

(59) The blade 264 and shaft 272 correspondingly have a D-shaped cross-section. Accordingly, the chamber of handle 268 also has a D-shaped cross-section, and is sized to receive shaft 272 and blade 264 with a snug fit.

(60) The shaft has one or more channels 276 that run axially down the length of the shaft to deliver an injectable biomaterial from lines 280 located at the proximal end 270 of handle 268 to the distal tip 262 of the device. Thus, with the distal tip 262 positioned in the facet joint cavity 230, bmp is delivered though channels 276 to distal tip 262 at the treatment site.

(61) Distraction may also be accomplished via insertion of an inflatable membrane in the joint 16. FIGS. 16A-16I illustrate an insertion device 300 for inserting inflatable membrane 302 into the facet joint in accordance with the present invention.

(62) The insertion device 300 comprises a handle 316 at its proximal end 318, and a malleable “spatula” shaped tip 306 at its distal end 308.

(63) The tip 306 generally comprises a straight, flat leading edge at distal end 308. Although the leading edge 308 is shown as a straight-line surface when viewed from above in FIG. 16A, it is appreciated that different shapes may also be utilized, (e.g. arcuate).

(64) The tip 306 is coupled to shaft 310 that is received within a D-shaped opening channel of the handle 316. The shaft 310 and tip 306 protrude distally from the handle 316 so that flat surface 314 running along the bottom of the tip and shaft is exposed. The shaft 310 has a beveled surface 312 that terminates at a point proximal to the distal tip end 308 of tip 306.

(65) Inflatable membrane 302, in accordance with the present invention, has a pocket 304 such that the inflatable membrane 302 can be disposed on distal end 308, and delivered through opening 32 created by the access tool 100 and into the cavity 30. Delivery into the cavity may be guided by sliding lower surface 314 along introducer 150. Once the inflatable membrane 302 is positioned in the proper location within cavity 30, inflation medium is delivered through line 330 running axially along shaft 310 from proximal end 318 to distal tip 308, and the inflatable membrane 302 is expanded inside the joint 30. The inflatable membrane 302 generates a force on the opposing facet surfaces and distracts the joint. With the added pressure, the insertion device 300 is simply just pulled out of the joint, with the tip 306 sliding out of pocket 304 while the inflatable membrane 302 retains its position.

(66) The malleable and thin planar shape of the “spatula” tip 306 and beveled shaft 312 allow for suboptimal entry angles and compensates for the narrow spacing of the facet joint. Thus, the inflatable membrane 302 may be delivered from a less invasive, by non-aligned orientation.

(67) The delivered implant is configured to distract the joint and reverse narrowing of the nerve root canal 38 and alleviate symptoms of cervical stenosis. However, it is also within the scope of the present invention to size the implant according to other spinal conditions, for example to correct for cervical kyphosis or loss of cervical lordosis

(68) The process for achieving indirect cervical decompression and fusion may also include posterior stabilization with any number of commercially available implants & instrument sets available in the art.

(69) Although the embodiments disclosed above are directed primarily to installation in the cervical facet joint, it is contemplated that the devices and methods may also be used to increase foraminal dimension in other regions of the spine, e.g. thoracic, lumbar, etc.

(70) Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”

(71) Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.