US 20060149279 A1
Methods and instruments for preparing a disc space and for forming interbody devices therein are provided. The instruments include distractors having enlargeable portions positionable in the disc space for distracting the disc space. The enlargeable portions can also provide form about or against which an interbody device of a first material is placed. A second material may be placed in the disc space in the space previously occupied by the distractors.
48. A spinal surgical system, comprising:
a distraction instrument including an enlargeable portion with a reduced size configuration for insertion into a disc space between adjacent vertebrae and an enlarged configuration adapted to occupy a first portion of the disc space and distract the adjacent vertebrae, wherein in said enlarged configuration said enlargeable portion includes opposite vertebral endplate contacting surfaces for contacting vertebral endplates adjacent the disc space;
a material having a first condition for placement in a second portion of the disc space formed exteriorly of the enlarged enlargeable portion, said material being changeable to a second condition after placement in the second portion; and
a stabilization system attachable to the adjacent vertebrae exteriorly of the disc space.
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68. A spinal surgical system, comprising:
a first distraction instrument including a first enlargeable portion with a reduced size configuration for insertion into a disc space between adjacent vertebrae and an enlarged configuration adapted to occupy a first portion of the disc space and distract the adjacent vertebrae, wherein in said enlarged configuration said first enlargeable portion includes opposite vertebral endplate contacting surfaces; and
a second distraction instrument including a second enlargeable portion with a reduced size configuration for insertion into the disc space between the adjacent vertebrae and an enlarged configuration adapted to occupy a second portion of the disc space and distract the adjacent vertebrae, wherein in said enlarged configuration said second enlargeable portion includes opposite vertebral endplate contacting surfaces.
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This application is a divisional of U.S. patent application Ser. No. 09/918,332, filed on Jul. 30, 2001, which is hereby incorporated by reference in its entirety.
The present invention relates generally to instruments and devices for spinal surgery, more particularly to methods and devices for spinal disc space preparation and interbody spinal stabilization.
There are prior art interbody devices that are fabricated prior to implantation and then inserted into the patient's spinal disc space during surgery. It is also known to insert one or more pre-fabricated devices from anterior, antero-lateral, lateral, postero-lateral, transforaminal, posterior, posterior mid-line or any other known approach to the disc space. These pre-fabricated devices can require the surgeon to modify the interbody device, the vertebral bodies, and/or the vertebral endplates to achieve a desired fit between the spinal anatomy and the interbody device. While some pre-fabricated devices can be modified before and during surgery by the surgeon, this is a time consuming task and also does not always result in a desired or optimum fit with the natural or altered spinal anatomy. Further, the various approaches and instruments required to insert pre-fabricated devices can be invasive and traumatic to the nervature, vasculature, and tissue between the skin and the disc space.
What is therefore needed are methods and devices for providing interbody devices in a disc space between vertebral bodies that allow the surgeon to achieve a desired or optimum fit between the device and the natural or altered spinal anatomy. What is also needed are devices and methods for preparing a disc space for an interbody device while minimizing invasion into the tissue between the skin and the subject disc space. What is further needed are improved devices and methods for performing spinal surgery. What is also needed are methods and devices for providing interbody fusion utilizing minimally invasive approaches and instruments. The present invention is directed toward meeting these needs, among others.
According to one aspect of the present invention, there is provided a form positionable in a spinal disc space and an interbody device made from material that has a first condition allowing placement around the form and in contact with the vertebral endplates and thereafter the material has a second condition that provides structural support between the endplates.
According to another aspect of the invention, there is provided a distractor for a disc space that has a reduced-size configuration for insertion into a disc space and an enlarged configuration for distracting the disc space and for defining a void between the enlarged portion and the inner wall of the disc space annulus.
According to yet another aspect of the invention, a spinal disc space distractor provides an intradiscal form around which an interbody device is placed.
According to a further aspect of the invention, a spinal disc space distractor having an enlargeable portion is provided.
According to a further aspect of the invention, a spinal disc space distractor having an enlargeable portion with upper and lower vertebral endplate contact surfaces with predetermined areas is provided.
According to another aspect of the invention, a surgeon inserts a distractor in a spinal disc space and places a first material around the distractor and between the vertebral endplates. When the first material cures, the distractor is withdrawn and a second material is placed in the disc space in the space that was occupied by the distractor.
According to a further aspect of the invention, multiple distractors having enlargeable distracting portions are inserted in the disc space to form a void for receiving a first material
According to another aspect of the invention, a disc space is bi-laterally distracted by inserting an enlargeable portion of a first distractor at a first lateral disc space location and an enlargeable portion of a second distractor at a second lateral disc space location. Scoliosis can be addressed by providing the enlargeable portions with different distraction heights.
According to a further aspect of the invention, a spinal disc space distractor having an enlargeable portion of a predetermined shape is provided. The predetermined shape is selected from one of the following: vertically-oriented cylinder, horizontally-oriented cylinder, sphere, cylindrical center portion with frusto-conical tapered ends; banana-shaped, and pear shaped.
These and other aspects, forms, features and advantages will be apparent from the following description of the illustrated embodiments.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications in the illustrated devices, and any such further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
The present invention provides techniques for forming interbody devices in a disc space of the spinal column. It is contemplated that techniques of the present invention utilize minimally invasive endoscopic instruments and methods for performing discectomy and other disc space preparatory procedures. However, open surgical techniques and other visualization instruments and techniques are also contemplated. In techniques where the interbody device is part of a spinal fusion procedure, percutaneous stabilization and fixation techniques through the pedicles or facets are also possible after completing insertion of the interbody device. The present invention further provides minimally invasive techniques for segmental stabilization of a spinal disc space to repair a spinal disc space due to, for example, disc space collapse or progressive mono-segmental instability which are normally repaired via discectomy procedures that do not include interbody fusion. The present invention has application from any approach to any disc space along the spinal column, including L5-S1. Further, the present invention has application in a bi-portal, postero-lateral approach to one or disc spaces in the lumbar region of the spine.
Reference will now be made to
In one specific surgical technique used with the present invention, the disc space in the lumbar region of the spine is accessed endoscopically via a foraminal or postero-lateral, bi-portal approach. Cannulas and dilators can be used for access ports 18, 19 and catheters inserted therethrough for visualization, discectomy procedures, distraction, and material delivery. In these approaches, the outer cannulas can have an outside diameter of up to 7.5 millimeters and more typically in the range of about 6.5 millimeters. However, any sized cannula is contemplated so long as there is an acceptable level of trauma to the tissue and nerve structures.
To provide access ports 18, 19 in this specific technique, insertion begins 9 to 13 centimeters from the midline with a guidewire or discogram needle. The facet joint at the dome of the facet is initially targeted and palpated by the tip of the needle. The needle is withdrawn and re-angulated to go inside the dome, thus missing the exiting nerve root. The posterior vertebral bodyline is imaged fluoroscopically to document its resting position. The fluoro machine is then moved to an A-P position and the resting zone is either on the mid or lateral pendicular starting position for a postero-lateral approach or the medial pendicular midline for a foraminal approach. Needle insertion into the disc space can be completed simultaneously on the left and right hand sides. The needles can be triangulated to touch one another in the posterior central portion of the disc space or alignment can be adjusted and conformed via discography.
One or more dilators of increasing diameter are then sequentially placed over each of the needles to the annulus, and a cannula is placed over each of the final dilators to land on the annulus. The final dilators are removed and a trephine used through each cannula to cut holes in the annulus to allow for entry into the disc space. An endoscope can be used at any time throughout the procedure to document the presence of nerve roots or to observe the annulus prior to cutting. The final dilator is then re-inserted into each of the cannulas and impacted through the hole in the annulus and into the disc space. The final dilator thus secures the cannula into position and obstructs the annulus opening to ensure material is delivered into the disc space without excursion out of the disc space. The cannulas and dilators are then used as access portals to the disc space for completion of the remaining procedures, and also allow for the interchange of instruments between the left and right sides. Either one of the access ports 18, 19 can then be used for endoscopic visualization and the other access portal 18, 19 can be used for disc material removal with manual, automated, ultrasonic, laser, or any other disc material removal instruments desired by the surgeon.
After discectomy there is a prepared disc space 24. It can also be desired by the surgeon to expose and gently remove endplate cartilage and to remove all soft tissue and debris from within the disc space to expose the inner wall of the annulus. Inner portions of a minimally appropriate amount of the inner wall laminates of annulus 14 surrounding the removed nucleus can be removed to increase the lateral and anterior-posterior extent of the prepared disc space 24. The remaining portion of the annulus remains intact except for the access holes cut for instrument entry locations. An endoscope can be placed in one of the access portals to check disc material removal and to also check the annulus to ensure there are no wall defects requiring repair. In cases where interbody fusion is desired, the endplates can be prepared by eburnating the apophyseal ring to prepare it for bony fusion, and the vertebral endplates can be scraped or abraded to reduce them to bleeding bone. Right angle curettes or probes can also be inserted to make small protrusions or abrasions into the endplates to further facilitate fusion if so desired.
After disc space access and discectomy, the disc space will typically still be in a collapsed state, and the only distraction that has been completed at this point has been the result of insertion of the final dilator into the disc space. The disc space must now be further distracted to the desired disc space height and also to establish lordosis if desired or necessary. Referring now to
Enlargeable portion 34 is sized with respect to prepared disc space 24 such that a void 26 is formed between the enlarged portion 34, inner wall of annulus 14, and the endplates 11 a, 11 b generally in the location of the apophyseal ring as shown in
In any event, enlargeable portion 34 is sized in the cephalad-caudal directions sufficiently to distract the spinal disc space to a desired normal disc space height and sized in the lateral and anterior-posterior directions to provide void 26 when enlarged. A single centrally placed enlargeable distractor 30 could utilize endplate geometry to create lordosis.
In addition to a single distractor having an enlargeable portion inserted into the disc space as shown above with respect to
As further shown in
It is contemplated that first material 50 can be a cement, poly(methyl methacrylate), or any other bio-compatible material that has the structural capabilities to withstand the spinal column loads applied thereto. It is further contemplated that first material 50 can be delivered in a first condition through an instrument channel or lumen of instrument 40 and thereafter changed to a second condition via any natural or chemically induced or enhanced reaction to form an interbody device 50′. First material 50 can further be static or include bio-active material to promote bone growth.
While delivery instrument 40 is illustrated as an instrument separate from distractor 30, it is also contemplated that distractor 30 could be provided with a working channel for delivery of first material 50 to void 26 or second material 60 to central space 52′. For example, as shown in
In another form, one or more flexible material delivery catheters can be placed over a guide wire extending through one of the access portals and into the disc space around enlargeable portion 34 and at various locations in void 26. The flexible catheter(s) can be placed through only one or both of the access portals 18, 19. With the desired distraction achieved and the material delivery catheters positioned as desired, the guide wires are removed and first material 50 delivered through the flexible catheter(s). First material 50 can be delivered sequentially through the catheters or simultaneously through the catheters to provide an interbody device 50′ that is completely formed about enlargeable portion 34 except for an entry port to central cavity 52′. Interbody device 50′ thus provides balanced spinal load support on the apophyseal ring. Second material 60 can then be placed centrally into the interbody device in the central cavity 52′ previously occupied by the withdrawn enlargeable portion 34 of distractor 30.
One specific technique for placement of first material 50 via bi-portal, postero-lateral access ports was completed as follows. The material delivery instrument 40 included first and second material delivery catheters each placed in a respective one of the first and second access ports 18 and 19. First material 50 was delivered through one catheter through the first access port under low pressure until the presence of first material 50 was detected at the distal end of the first access port or the second access port. The catheter was then slowly pulled back through the first access port until first material 50 was delivered to the distal end of the first access port housing the first delivery catheter. Thereafter the first material delivery catheter was withdrawn. First material 50 was then delivered through the second material delivery catheter positioned in the second access port until first material 50 was detected at the distal end of either of the second access port or the first access port. The second material delivery catheter was then pulled back through the second access port, thereby completely filling the void 26 with first material 50.
Several factors are to be considered in placing first material 50 in the disc space. For example, if first material 50 were a cement, factors to consider include the liquidity of the cement, the cure temperature of the cement and the insertion pressure of the cement. If the cement has a relatively cool temperature, then more time is required for the cement to cure which increase operating room time. Curing time can also be affected by adding other substances to it, such as growth factors, antibiotics and/or barium tracer. The injection pressure of first material 50 can affect whether it will leak out of small tears in the annulus or infiltrate interstices and nutrient canals of the vertebral endplates. It is also desirable that placement procedures for first material be carried out under fluoroscopy with a tracer such as barium in first material 50 to allow monitoring of material excursion and its presence in the disc space. Monitoring of the placement of first material 50 to confirm its proper positioning in the disc space can be accomplished by AP and lateral fluoroscopy or bi-planar fluoroscopy. The presence of material excursion could signify a significant annulus or other anatomical or surgically created defect or void. Such monitoring provides a safety measure to ensure first material 50 is not placed into inappropriate anatomic locations during formation of interbody device 50′.
Referring further to
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There are several distraction and material placement techniques afforded by use of lateral distractors as shown in
It is further contemplated that the placement location for first material 50 can be varied at any location about the apophyseal ring by using combinations of lateral distractors, anterior and posterior distractors, and central distractors. Further, it is contemplated first material 50 could be placed at multiple, discrete locations about the apophyseal ring to provide a number of columnar or segmented interbody devices in the disc space. These segmented interbody devices could be formed adjacent to and in contact with one another or formed with gaps therebetween. It is further contemplated that the positioning of the various interbody devices could be varied to accommodate the approach desired for material placement, including both uni-lateral injection or a bi-lateral placement.
In another embodiment, the banana-shaped lateral distractors 70 a, 70 b can be tapered in height to provide angulation between the vertebral endplates. For example, lordosis could be established by providing the enlargeable portions 74 a, 74 b with a greater height posteriorly than anteriorly. Further, the lateral distractors 70 a, 70 b can be provided with differing heights in order to distract one side of the disc space more than the other side, reducing or eliminating scoliosis. Alternatively, identical inflatable devices could be provided in which the inflatable portions have a height that corresponds to the internal inflation pressure supplied thereto. One of the lateral distractors could be inflated to a greater pressure than the contra-lateral side to provide differential distraction heights for each side. The same lateral distractor could be employed bi-laterally to change the lateral angulation of the disc space by varying the inflation pressure supplied to the enlargeable portion thereof.
After repairing scoliosis by providing the appropriate distraction and interbody devices, the disc space occupied by the enlargeable portions of the distractor is available for placement of bone growth material. For example, if two banana-shaped inflatable devices are used, a central cavity encompassed by the enlargeable portions remains after the portions are enlarged. Second material can then be placed in this central cavity. Additional first material can then be placed in the space previously occupied by the enlarged portions to provide structural peripheral support. Thus, this specific example contemplates initially central placement of a first material, such as bone growth material, and then the enlargeable distractors can be sequentially or simultaneously withdrawn from the disc space and a second material, such as a cement, placed around the central core of first material and against the enlargeable distractor portion, if any, remaining in the disc space to provide structural support of the disc space.
As discussed above, enlargeable portion 34 of the distractor 30 can be an inflatable device. In
Referring now to
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Referring now to
In addition to the above-described shapes, other shapes for the enlargeable portion 34 of distractor 30 are also contemplated. For example, the enlargeable portion can have a shape that corresponds to the shape of the vertebral endplates, such as a kidney bean shape, or can have a square or rectangular cuboid shape. It is also desirable that first material 50 does not adhere to the enlargeable portion 34 while it is curing. Thus, various coatings can be applied to the exterior surface of enlargeable portion 34 such as, for example, Teflon spray or silicone oil. Other coatings are also contemplated, so long as they prevent the adhesion of first material 50 and enlargeable portion 34. For embodiments in which enlargeable portion 34 is an inflatable device, the device should also be made from a tough yet elastic material that can withstand the inflation pressures applied thereto while also retaining the capability to return to a reduced size configuration for insertion and withdrawal from the disc space and through the access port.
The inflatable devices of the present invention can be designed to accommodate the patient anatomy. One factor considered in such a design is the force required to distract the disc space to the desired disc space height. The ability of the vertebral endplates to resist contact pressure has been found to decrease with patient age. For example, one study found those persons in the range of 20-30 years have a vertebral endplate resistance capability of 1500 pounds per square inch, those persons in the range of 40-60 year olds have a vertebral endplate resistance capability of 1050 pounds per square inch, and those persons over 60 year olds have a vertebral endplate resistance capability of 594 pounds per square inch. In order to distract the disc space with an inflatable device, sufficient pressure must be exerted to overcome the tension from the muscles and ligaments that have become accustomed to the collapsed condition of the disc space. However, the pressure on the vertebral endplates must remain within acceptable limits.
Based on the contact area of the balloon, the load the balloon will exert on the vertebral endplates to distract the disc space can be determined. The pressure exerted on the vertebral endplates can also be determined and the balloon sized so that the contact pressure does not exceed the vertebral endplate resistance capability of the patient. The following table presents the maximum allowable load for various balloon contact areas based on the vertebral endplate resistance for the patient ranges provided above:
As shown in
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.