Patent Application
20060142861
The present invention relates to a spinal disc replacement and, more particularly, to a bellows type device which flexes in all directions to accommodate natural bodily movements.
Spine non-fusion technologies have been under development for over 50 years. Many designs over the years have been purely theoretical. Consequently, many of the designs, patents and ideas were abandoned well before any clinical work was performed. In the past two years, non-fusion technology and philosophy has evolved from the clinical setting to a realized industry.
Total disc replacements are presently being sold worldwide. The rapid growth of the market may be attributed to:
The relief of low back and leg pain is the primary endpoint to spine surgery. One of the most integral components to the relief of pain and to ensuring success is the surgical technique and implant design. The currently offered Total Disc design technologies are anterior surgical procedures. In U.S. Pat. No. 4,932,975, Main et al disclose a vertebral prosthesis including a pair of housings having side and end walls forming a chamber in each housing. A suspension plane is in each housing, and at elastometric medium surrounds each suspension plate. The two suspension plates are interconnected by an expandable bellows.
Fuhrmann et al in U.S. Pat. No. 5,002,576 disclose an intervertebral disk endoprosthesis filled with a viscoelastic material, and a circular or elliptical corrugated tube surrounds the viscoelastic material and is contiguous thereto.
Fleischmann et al in U.S. Pat. No. 6,375,682 disclose a spinal prosthesis device which is expanded (or retracted) hydraulically.
In U.S. Pat. No. 6,395,032, Gauchet discloses an intervertebral disc prosthesis having a liquid in a closed chamber formed by a flexible seal between two opposing plates. A body, disposed in the chamber, has a plurality of pores at an outer surface thereof, and further has cavities extending from the pores in the body. The materials of the body and the liquid, respectively, are selected such that a compressive force must be applied to the liquid to force it into the cavities.
In U.S. Pat. No. 6,527,804 Gauchet et al disclose an intervertebral disc prosthesis having a body providing a cushion between two plates, and further having a compressible fluid (such as a gas) extending around the periphery of the body. The cushion exhibits a hysteresis-shaped curve of mechanical reaction to a compression as a function of a variation in a dimension of the cushion in the direction of the compression.
Gauchet also discloses, in U.S. Pat. No. 6,582,466, a prosthesis in which a compressible fluid in a sealed chamber is provided with a compressible body having a resistance to compression forces which is greater than that of the fluid.
Gauchet further discloses, in U.S. Pat. No. 6,582,468, a prosthesis having a compressible body in a closed fluid chamber formed by a flexible seal extending between a pair of opposed plates. The flexible seal enables the plates to move relative to each other.
In U.S. Patent Published Application No. 2003/0009223, Felding et al disclose a prosthesis having a caudal disc which is parallel to, and axially spaced from, a cranial disc. A spring means is disposed between the discs to elastically support the discs upon compression. the material of the spring means is a memory-metal alloy which has super elastic properties at body temperature.
In U.S. Patent Published Application No. 2003/083719, Kuslich et al disclose a device for connecting and stabilizing a spinal deformity. At least two stacked rods, closely spaced and parallel to each other, are connected to bone anchors for compressing the rods tightly together.
Ferree et al, in U.S. Patent Published Application No. 2003/0074076, disclose an artificial disc replacement (ADR) which includes a pair of end plates, a cushioning component therebetween, and a filler material within the cushioning component.
However, despite all of the interest and activity in the field, there is a need for an improved replacement device. There is specially a need for a device which accommodates normal bodily movement and which can be used with less invasive posterior surgical techniques.
It is an object of the present invention to provide a spinal disc replacement for damaged regions of the spine to avoid spinal fusion type surgery.
It is further an object of the present invention to provide a device having at least one bellows to be surgically implanted in the spine to replace a damaged spinal disc.
It is another object of the present invention to provide a device which compressible anteriorly/posteriorly and which is compressible medially/laterally.
It is still another object of the invention to provide a device which has rotational torsion between a top plate and a bottom plate.
In accordance with the teachings of the present invention there is disclosed a spinal disc replacement adapted to be surgically implanted in the vertebrae of a human patient. A device has at least one bellows disposed between a pair of spaced-apart top and bottom plates secured together peripherally of the bellows for retaining the bellows therebetween. The bellows is encapsulated to form a barrier against bodily fluids contacting the bellows. The bellows accommodates normal bodily movements of a patient receiving the spinal disc replacement, including twisting movements of the spinal disc replacement to a limited angular degree and in either direction circumferentially about a central longitudinal axis of the bellows.
In further accordance with the teachings of the present invention, there is disclosed a bellows assembly to be inserted into a patient's spinal column for replacement of a ruptured disc in lieu of a fusion procedure. The device has at least one bellows welded to top and bottom plates, respectively. The bellows and each of the plates are formed from different metallic materials, and an insulating member is disposed between the bellows and each of the plates, thereby preventing an electrolytic action between the bellows and the plates, respectively.
In still further accordance with the teachings of the present invention, there is described a bellows assembly to be inserted into a patient's spinal column for replacement of a ruptured disc in lieu of a fusion procedure. The assembly has at least one bellows welded to top and bottom plates, respectively, wherein the assembly can flex in a compressive mode substantially along the longitudinal axis of the bellows and between the respective plates. The assembly can accommodate pivotal movement of the assembly in a torsional mode and, to a limited degree, circumferentially about the longitudinal axis of the bellows.
Additionally, in accordance with the teachings of the present invention there is disclosed both an anterior and a posterior method of replacing the damaged spinal disc.
These and other objects of the present invention will become apparent from a reading of the following specification taken in conjunction with the enclosed drawings.
Referring now to
Abutting the insulator panel 20 is a housing plug 22 which has a depending cylinder 24 of a smaller diameter than the housing plug 22. The top of the housing plug 22 is disposed in an opening in a locator plate 26 with the depending cylinder 24 extending through the opening in the locator plate 26. The depending cylinder 24 is disposed in a top housing 28. The top housing 28 serves as a top end of the bellows 14.
The bellows 14 is a plurality of vertically joined rings forming a unitary bellows. The rings may be of the same or of different thickness to obtain a desired modulus of elasticity. The bellows may also be coated with a polymer if desired.
The bottom of the device is the reverse of the top, having, in sequence, a bottom housing 30, a locator plate 26, a housing plug 12, with a cylinder 24 formed thereon, an insulator panel 20 and a bottom plate 12 with exterior spikes 16. The device is secured with a plurality of fasteners 32, the top plate 10 and the bottom plate 12. Preferably, the respective locator plates 26 are welded to the top plate 10 and the bottom plate 12. An insulator barrier 34, preferably of an elastometric material, encapsulates the outer periphery of the device to keep out body fluids.
The above description addresses only one bellows but as noted above, two bellows may be disposed between the top plate 10 and the bottom plate 12. The second bellows is mounted and disposed in an identical manner to the first bellows.
The device 10 is compressible anteriorly/posteriorly from approximately 0°-4° as shown in
The device does not require any fluid to be contained within the bellows.
The device may be made without the insulator. As shown in
The device may also be made without a housing plug, an insulator, a housing or a locator plate. As shown in
The device with the kidney shaped plates and two bellows is surgically implanted in the patient by anterior procedures which require an incision abdominally in the patient.
A device formed having only one bellows may also be made. As shown in
Similarly, as shown in
Also, a single bellows device having the insulator panel 20 may be made as shown in
The device is surgically implanted in the spine of a human being by making an incision in the abdominal area of the patient and providing access to the spine. The damaged region of the spine is removed. The device having at least one bellows and preferably having a kidney shaped top and bottom plate is inserted into the spine where the damaged region had been removed.
Techniques to be used by the surgeon will be developed and refined.
The device may also be implanted in the spine of a human being by making a midline incision posteriorly (
The type of device is selected by the surgeon depending upon the needs of the patient. The device may be any of those described above, i.e., the device without a domed housing plug, the device with the domed housing plug or the device with insulator panel.
The bellows 19 preferably is made from stainless steel and the top and bottom plate are formed form implantable grade titanium alloy or other alloy suitable to the practice.
The devices may be made in small, medium or large sizes. Under maximum anatomic material load of 1200 N±10 bellows compression distance is 9.5 mm to 6.5 mm.
Obviously, many modifications may be made without departing from the basic spirit of the present invention. Accordingly, it will be appreciated by those skilled in the art that within the scope of the appended claims, the invention may be practiced other than has been specifically described herein.
