Method and apparatus for intervertebral disc expansion

[0001] This application relates to co-pending U.S. patent application Ser. No. ______ , filed on Sep. 18, 2002, entitled Collagen-Based Materials And Methods For Augmenting Intervertebral Discs, naming Hai Trieu and Michael Sherman as inventors. The co-pending application is incorporated herein by reference in its entirety, and is assigned to the assignee of this application.

[0002] The present disclosure relates to surgical apparatus and methods, and more particularly to the treatment of intervertebral discs.

[0003] Degenerated disc disease (DDD) leads to disc dehydration (black disc), gradual collapse, and ultimately leg and/or back pain. Interbody fusion is the current standard of care for DDD. It is desirable that this end-stage treatment be delayed as long as possible by early intervention with less invasive approaches. Disc augmentation by injection of a biomaterial into the disc space has been proposed previously as an early minimally invasive treatment for a degenerated disc. Depending on the level of dehydration and collapse, injection of a biomaterial into the disc space of an intact disc (uncompromised annulus with no significant tears and original nucleus pulposus still in place) may require a high injection pressure and the injectable volume of biomaterial may be limited. High injection pressure increases the overall risk of the procedure including leakage, disc rupture, etc. Limited injectable volume reduces the effectiveness of the treatment and may require multiple treatments to achieve desirable results.

[0004] In known methods for intervertebral disc expansion, a cut is made in the disc annulus and disc tissue is removed to provide a passage for the insertion of an expansion device, an expansion material, or both. Also, the nucleus pulposus is removed and replaced by the expansion material and/or expansion device. Furthermore, degeneration of the disc is accelerated when an opening is cut into the disc annulus and tissue is removed.

[0005] Therefore, what is needed is a device and method for accessing the nucleus pulposus for expansion of the disc such that no portion of the disc annulus and the nucleus pulposus are removed. Also, what is needed is an apparatus and method for a minimally invasive disc treatment which increases injectable volume at a lower pressure.

[0006] One embodiment, accordingly, includes an expandable device for intervertebral disc expansion by means of an inflatable member insertable into a dilated opening in an intact intervertebral disc annulus and into a nucleus pulposus of the disc. An inflation device is connected to controllably inflate the inflatable member within the nucleus pulposus without removing the nucleus pulposus.

[0007] A principal advantage of this embodiment is that it enables disc expansion with a percutaneous or minimally invasive approach. The disc expansion enables a larger volume of biomaterial injection per treatment. A larger volume of biomaterial injection reduces the number of treatments to achieve desirable level of augmentation. This treatment enables disc expansion without removal of the nucleus pulposus and helps determine the appropriate biomaterial volume prior to injection. Over-injection of the disc, and resulting pain and complications, can be minimized using the proposed device and method.

[0008] Another advantage is that the disc remains intact such that no portion of the disc annulus or disc nucleus is removed.

[0009] FIG. 1 is a cross-sectional view illustrating an embodiment of a disc structure.

[0010] FIGS. 2A-2F are cross-sectional views illustrating an embodiment of a disc expansion method and apparatus.

[0011] FIG. 3 is a cross-sectional view illustrating another embodiment of a disc expansion method and apparatus.

[0012] FIG. 4 is a cross-sectional view illustrating another embodiment of a disc expansion method and apparatus.

[0013] FIGS. 5A-5D are cross-sectional views illustrating another embodiment of a disc expansion method and apparatus.

[0014] A disc structure 10, FIG. 1, generally comprises adjacent vertebrae 12 and 14 of the cervical, thoracic, or lumbar regions of the spine. An intervertebral disc 16 facilitates motion between the vertebrae 12 and 14 while absorbing shock and distributing loads. The disc 16 generally comprises a soft central core, i.e. the nucleus pulposus 18 (disc nucleus), that bears the majority of the load in a healthy disc, and a tough outer ring, i.e. the annulus fibrosis 20 (disc annulus), that surrounds and stabilizes the disc nucleus 18. A pair of cartilage endplates 22 are between each respective vertebrae 12 and 14, and the disc nucleus.

[0015] The method and apparatus are used following a patient diagnosis and selection for treatment, and in addition, a discogram to ensure disc annulus integrity.

[0016] The disc annulus 20, FIG. 2A, is punctured at 21 using a small diameter needle 24. A preferable needle size is 20 gauge. A small diameter (i.e. 1 to 3 mm) high-pressure balloon catheter 26, FIG. 2B, is introduced through the puncture 21 in the disc annulus 20. The location of a balloon 28 attached to catheter 26, in the disc nucleus 18 may be verified using fluoroscopy. The puncture required for insertion of devices for disc expansion and injection is small enough i.e. no greater than 3 mm, that the puncture may completely close, or close sufficiently that the injected biomaterial will remain captured. In the case of a biomaterial that sets up in the disc space after injection, capture of the injected biomaterial is assured. The use of an annulus closure device such as a plug or material such as a sealant is optional.

[0017] The balloon 28, FIG. 2C is gradually inflated with a saline and/or radiographic contrast medium such as sodium diatrizoate solution sold under the trademark Hypaque, while monitoring the internal balloon pressure with a well known pressure gauge. Expansion of the balloon 28 is monitored using fluoroscopy. The rate of inflation and the pattern, size or shape of the balloon 28 can be varied between patients depending on disc condition. As the intradiscal pressure is increased and/or the endplates 22 are spread apart by the balloon 28, the disc annulus 20 is expected to stretch, as it is a viscoelastic material. The balloon may remain inflated from about 1 minute to about 1 hour, which may be varied for each patient. If significant expansion is required, the balloon may remain inflated up to 4 hours or it may be left in the disc space as a temporary implant up to 10 weeks.

[0018] As the balloon 28, FIG. 2D, is deflated, the disc 16 becomes slack with an augmented space and reduced intradiscal pressure. Injectable biomaterial 29 such as a collagen gel can be delivered to the disc nucleus 18, FIG. 2E, either through the same catheter, or a different needle 30 may be used after the balloon catheter 26 is deflated and removed. If the same catheter is used for injection, the injection can be done simultaneously as the balloon 28 is being deflated, as will be discussed below in greater detail.

[0019] Examples of biomaterials 29 which may be used for disc augmentation can be natural or synthetic, resorbable or non-resorbable. Natural materials include various forms of collagen that are derived from collagen-rich or connective tissues such as an intervertebral disc, fascia, ligament, tendon, skin, demineralized bone matrix, etc. Material sources include autograft, allograft, xenograft, human-recombinant origin, etc. Natural materials also include various forms of polysaccharides that are derived from animals or vegetation such as hyaluronic acid, chitosan, cellulose, agar, etc. Other natural materials include other proteins such as fibrin, albumin, silk, elastin and keratin. Synthetic materials include various implantable polymers or hydrogels such as silicone, polyurethane, silicone-polyurethane copolymers, polyolefin, polyester, polyacrylamide, polyacrylic acid, polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polylactide, polyglycolide, poly(lactide-co-glycolide), poly(dioxanone), poly(-caprolactone), poly(hydroxylbutyrate), poly(hydroxylvalerate), tyrosine-based polycarbonate, polypropylene fumarate or combinations thereof. It is preferred that the biomaterial can undergo transition from a flowable to a non-flowable state shortly after injection. This can typically be achieved by adding a crosslinking agent to the biomaterial before, during, or after injection.

[0020] Proteoglycans may also be included in the injectable biomaterial 29 to attract and/or bind water to keep the disc nucleus 18 hydrated. Similarly, growth factors (e.g. transforming growth factor beta, bone morphogenetic proteins, fibroblast growth factors, platelet-derived growth factors, insulin-like growth factors, etc.) and/or other cells (e.g., intervertebral disc cells, stem cells, etc.) to promote healing, repair, regeneration and/or restoration of the disc, and/or to facilitate proper disc function, may also be included. Additives appropriate for use in the claimed invention are known to persons skilled in the art, and may be selected without undue experimentation.

[0021] Injectable biomaterial 29 is preferably mixed with the radiographic contrast medium prior to injection into the disc nucleus 18. This will allow the injection to be monitored using fluoroscopy. The catheter 26 or the needle 30, FIG. 2F, used for injection, is removed after an appropriate volume of biomaterial is deposited in the disc nucleus 18.

[0022] As an alternative to withdrawing the balloon 28, as illustrated in FIG. 2D above, a balloon 128, FIG. 3 may be detachable at 127 from a catheter 126, and may remain inflated in the disc nucleus 18 as an implant. In the case of the detachable balloon 128, it may be advantageous to inject a biomaterial which, after injection, takes a set in an elastic or gel form. This could be accomplished by injecting a second material with the biomaterial which would alter the form of the injected material.

[0023] As an alternative to inflating balloon 28 with the radiographic contrast medium as described above, the balloon 28 may be inflated by injection of the biomaterial 29. This would be advantageous in the embodiment described above where the balloon is detachable and where the biomaterial may take a set after injection.

[0024] In the case of direct injection of biomaterial 29 into the inflatable balloon member 28, the balloon 28 may be porous or permeable (e.g. woven fabric, mesh structure, perforated membrane, etc.) to allow material or fluid migration out of the inflatable member during or after injection.

[0025] Alternatively, a modified balloon 28a, FIG. 4, may be of a shape including a profiler for inflating in a pattern for spreading the endplates 22 apart. That is, the balloon 28a is manufactured to expand to a suitable shape to better accomplish spreading the endplates 22 apart rather than to conform to the shape of disc nucleus 18 as in FIG. 2C.

[0026] An alternative balloon catheter may be used, i.e. a double lumen catheter which can be used for injection as the balloon is being deflated. In an alternative embodiment, FIG. 5A illustrates a balloon catheter 526 introduced into the disc nucleus 18. The catheter 526 includes a first channel 531, a second channel 532 and a balloon 528. The saline and/or radiographic contrast medium is injected into balloon 528 via the first channel 531 to inflate balloon for expansion of the disc nucleus 18. In FIG. 5B, the inflated balloon 528 remains inflated in the disc nucleus 18 for an appropriate amount of time to stretch the annulus fibrosis and/or expand the nuclear disc space. In FIG. 5C, an appropriate biomaterial 29 is injected into the disc nucleus 18 via the second channel 532 in catheter 526 while the balloon inflating medium is simultaneously evacuated via the first channel 531. In FIG. 5D, the deflated balloon 528 is withdrawn with catheter 526 from the disc nucleus 18 and the injected biomaterial 29 remains within the disc nucleus 18.

[0027] As a result, one embodiment provides an apparatus including a high-pressure balloon catheter with a small shaft diameter (3 mm or smaller, preferably 2 mm or smaller, most preferably 1 mm or smaller). The catheter has a pointed tip for puncturing an intact disc annulus and insertion of the balloon section into the nuclear disc region. The catheter either has rigid shaft or is supported by a rigid guide-needle during penetration into the disc. For a rigid shaft, the catheter can be made of metal tubing. For a flexible shaft, the catheter can be made of polymeric tubing and is supported with a rigid guide-needle or guide-wire. If a guide-needle is used, the catheter can be double lumen. The balloon has an appropriate final volume of from about 0.1 cc to about 8.0 cc, preferably up to 5.0 cc and dimensions (length5-40 mm, preferably 10-30 mm; diameter3-20 mm, preferably 5-15 mm) to fit the nuclear disc region. The balloon can be of various shapes; conical, spherical, square, long conical, long spherical, long square, tapered, stepped, dog bone, offset, or combinations thereof. Balloons can be made of various polymeric materials such as polyethylene terephthalates, polyolefins, polyurethanes, nylon, polyvinyl chloride, silicone, polyetheretherketone, polylactide, polyglycolide, poly(lactide-co-glycolide), poly(dioxanone), poly(-caprolactone), poly(hydroxylbutyrate), poly(hydroxylvalerate), tyrosine-based polycarbonate, polypropylene fumarate or combinations thereof.

[0028] Another embodiment provides first, a determination that the treated disc has a competent and intact annulus fibrosis for safe expansion and effective containment of the subsequently injected biomaterial. After the annulus quality and integrity are verified using discography, the disc expansion device with the smallest shaft diameter possible, is inserted into the center of the disc. Insertion of the device can be done percutaneously, preferably under fluoroscopic guidance. The balloon is gradually inflated with radio-contrast fluid or saline to pressurize the disc, and thereby, stretch the annulus fibrosis. After a predetermined inflation time, the balloon is deflated and removed from the disc space. The biomaterial is subsequently injected into the disc using a small-diameter hypodermic needle until a desirable injection volume is achieved. When a double-lumen catheter is employed, the biomaterial can be injected into the disc through the same catheter during or after balloon deflation. The whole procedure is preferably done under fluoroscopic guidance.

[0029] The foregoing has described an apparatus and method for expansion of an intervertebral disc prior to its augmentation with an injectable biomaterial. Disc expansion prepares the disc annulus to receive a desirable or effective volume of injectable material in a single treatment. Because the annulus fibrosis is a viscoelastic material, it can be temporarily stretched as the disc is expanded under pressure.

[0030] Although illustrative embodiments have been shown and described, a wide range of modification, change and substitution is contemplated in the foregoing disclosure and in some instances, some features of the embodiments may be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner. consistent with the scope of the embodiments disclosed herein.