Patent Application
20090062807
The present invention relates to a device for percutaneously preparing an interbody space and placing a device within the interbody space of the spine.
Spinal fusion surgery is the joining together of vertebrae of the spine. The underlying concept of fusion surgery implants is to maintain the relative position of the vertebral bodies with respect to eachother while bone graft placed between the vertebrae has an opportunity to heal and mature. These devices employ different strategies and philosophies, such as devices which utilize the pedicles, and devices which are placed in the disc space. The latter devices and techniques associated with these devices are known as “interbody fusion” devices. While no single technique has been universally accepted as the most optimum method, there is growing evidence that interbody fusion may be the preferred method.
Initially, all interbody fusion procedures were accomplished using a posterior approach. The procedure typically begins with a laminectomy, followed by removal of the intervertebral disc, and then in most cases the height of the disc space is increased and packed with pieces of bone. The goal is for the inserted bone pieces to fuse together with the vertebrae above and below that disc space, forming a bridge of bone and therefore eliminating motion at that spinal level.
More recently, interbody fusion performed by an anterior procedure has gained popularity. Anterior fusion instruments typically provide for a retroperitoneal or transperitoneal approach to the lumbar disc. Some or all of the disc is removed, and either bone or a metallic device is placed into the disc space. These devices also typically provide a means for distracting the disc space, i.e. making the space between the discs wider. Presently, this aspect of lumbar interbody fusion procedures are considered to be an important step in the procedure because of its effects on the neural foramina, or areas from which the nerve roots exit through the vertebra. It is generally accepted that enlarging the disc space consequently enlarges the neural foramina, thus decompressing the exiting nerve roots.
Due to presently available equipment, current anterior interbody fusion surgeries are disadvantageously invasive, requiring large incisions and manipulation of both tissue and organs. While attempts have been made to perform anterior interbody fusions laparoscopically, these procedures are often complicated and are typically performed under general anesthesia.
Therefore, a need exists for an interbody fusion method which reduces trauma to the patient; consequently reducing recovery time. Implant and instruments for percutaneous anterior interbody fusion; enabling the surgeon to distract the disc space to restore disc height, maintain the distraction, and promote the growth of interbody bone graft, would satisfy this heretofore unaddressed need.
Most commonly, surgery over a wire or through a tube has been used for placement of devices into bones of the spine. However, the technique of the current invention has not been applied for disc space preparation and device placement.
Numerous prior art methods and devices exist in this arena. Some describe utilization of wires or tubes for percutaneous placement of interbody devices—however, most do not employ direct entry into the interbody space itself with percutaneous instruments. U.S. Pat. No. 6,666,891 to Boehm et al describes a system whereby a guide wire is placed into the discspace and a sequence of serial dilators is used to create a working channel through which disc space preparation is performed. An expandable interbody fusion device is then placed and the guide tube removed.
The current invention describes a method and means of placing an interbody device percutaneously into the space between vertebrae with a substantially posterior, posterolateral, or lateral approach. The device itself may comprise a device for purposes of fusion or for other purposes such as nucleus or disc replacement or placement of biologic substances. One embodiment of the current invention differs significantly from that of Boehm et al in that the need for a guide wire and an expandable interbody device are eliminated. The working tube of the present invention allows preparation of the endplates of the vertebra through windows in the side. This allows more stable placement of a longer tube into the disc space while maintaining access to the endplates. In yet another embodiment, the working tube with side openings also becomes the delivery device and implant. The present invention includes methods and devices for both fusion and non-fusion spinal surgeries.
While the invention has been shown and described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes and modifications in form and detail may be made therein without departing from the spirit and scope of the invention, as defined by the appended claims.
It is an object of the present invention to present a simplified, minimally invasive, percutaneous surgical procedure for placement of an interbody device.
It is also an object of the present invention to present a method of percutaneous interbody fusion surgery where the interbody device is implanted through small incisions and a minimum of incisions, thereby reducing trauma to the patient.
It is also an object of the present invention to present a means of percutaneously preparing an interbody space for accepting an implant.
It is also an object of the present invention to eliminate the need for serial dilation.
It is also an object of the present invention to eliminate the need for placement of a working tube.
It is also an object of the present invention to provide a device which can be inserted over a guide wire and which distracts the disc space.
It is also an object of the invention to provide examples of several instruments for preparation of the interbody space for receiving said interbody device. The instruments and device incorporate self-distracting features to facilitate placement and distraction of the interbody space.
It is also an object to present instruments which have tapered or rounded features to minimize entanglement of soft tissue when withdrawing the instruments from the body.
It is also an object of the present invention to provide a kit for performing a minimally invasive percutaneous interbody procedure.
A method for placing a percutaneous interbody device is also provided, in which a guide mechanism (e.g. a wire) is first placed into the disc space, possible guided by a hollow needle with an internal diameter larger than the guide mechanism, such as a bone marrow biopsy or “Jamshidi” needle. Placement and use of all instruments may be guided by fluoroscopy or other intraoperative navigation tool or tools.
Once the guide wire is placed, a wide variety of instrument constructions may be utilized which mate with and are guided by the guide mechanism. The following procedure is given as an example and is therefore not intended to limit the scope of the invention:
A kit for performing percutaneous interbody preparation is also provided which includes the guide mechanism, means for placing the guide mechanism, instruments required for performing disc removal and disc space preparation, and possibly an interbody implant with an insertion handle.
All instruments may also have a tapered or rounded trailing edge to facilitate removal of the instrument from the body and to prevent damage to soft tissues.
The device of the present invention utilizes a method of preparing a disc space for accepting an implant whereby all instruments and implants are placed over the guide mechanism and all instruments and implants have a tapered or similar leading feature. While the preferred embodiment of the guide mechanism is a wire, other embodiments could include any configuration whereby the subsequent instruments and implants substantially encompass and surround the guide mechanism even if only partially.
The preferred embodiment of the guide mechanism is a wire which is long enough to enter the interbody space and protrude from the skin incision. Alternative embodiments include: solid or hollow rods of various cross-section, or the instruments and implants may not circumscribe the guide mechanism but may have a feature such as a slot along which the instruments and implants are passed. For example, the guide mechanism may be a square bar having one or more longitudinal slots or grooves which cooperate with a feature on the instruments and implants.
All instruments and implants could potentially incorporate means for surgical tracking or intra-operative nerve monitoring to minimize injury to nervous structures.
