Abstract:
A spinal disc replacement has at least one bellows disposed between two spaced-apart plates. The bellows are compressible anteriorly/posteriorly and left/right. Several embodiments have top plates and bottom plates which are torsionally rotatable. Methods of use are provided.

Description:
FIELD OF THE INVENTION  
       [0001]     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.  
       BACKGROUND OF THE INVENTION  
       [0002]     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.  
         [0003]     Total disc replacements are presently being sold worldwide. The rapid growth of the market may be attributed to: 
        Rapid uptake of total disc replacements through comprehensive surgeon training and education.     Steady sales growth and continued increases of annual usage.     Surgical Technique training workshops.     Philosophical education on the biomechanics, theoretical advantages, and presentation of long-term clinical data on various technologies.     Better understanding of the science of non-fusion and the associated segmental benefits of preserving motion and maintaining form and function.     Improved easy-to-use instrumentation that makes the procedure repeatable and reproducible.        
 
         [0010]     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.  
         [0011]     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.  
         [0012]     Fleischmann et al in U.S. Pat. No. 6,375,682 disclose a spinal prosthesis device which is expanded (or retracted) hydraulically.  
         [0013]     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.  
         [0014]     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.  
         [0015]     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.  
         [0016]     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.  
         [0017]     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.  
         [0018]     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.  
         [0019]     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.  
         [0020]     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.  
       BRIEF SUMMARY OF THE INVENTION  
       [0021]     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.  
         [0022]     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.  
         [0023]     It is another object of the present invention to provide a device which compressible anteriorly/posteriorly and which is compressible medially/laterally.  
         [0024]     It is still another object of the invention to provide a device which has rotational torsion between a top plate and a bottom plate.  
         [0025]     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.  
         [0026]     In further accordance with the teachings of the present invention, there is disclosed a bellows assembly to be inserted into a patient&#39;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.  
         [0027]     In still further accordance with the teachings of the present invention, there is described a bellows assembly to be inserted into a patient&#39;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.  
         [0028]     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.  
         [0029]     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. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]      FIG. 1  is a perspective anterior view of a human spine having the device of the present invention surgically implanted therein.  
         [0031]      FIG. 2  is a perspective view of the device of the present invention.  
         [0032]      FIG. 3  is a top view of the device of the present invention.  
         [0033]      FIG. 4  is a partial cross-section view of the present invention.  
         [0034]      FIG. 5  is a perspective view of a bellows.  
         [0035]      FIG. 6  is an exploded side view of a preferred embodiment of the present invention.  
         [0036]      FIG. 7  is an end view showing anterior/posterior compression.  
         [0037]      FIG. 8  is a side view showing left/right compression.  
         [0038]      FIG. 9  is a top view showing torsional rotation between the top plate and the bottom plate.  
         [0039]      FIG. 10  is a perspective view of the device showing torsional rotation of the plates in opposite directions.  
         [0040]      FIG. 11  is a perspective view of the device showing torsional rotation of the plates in the same direction.  
         [0041]      FIG. 12  is a perspective view of the device showing torsional movement of only the top plate.  
         [0042]      FIG. 13  is a perspective view of the device showing torsional movement of only the bottom plate.  
         [0043]      FIG. 14  is an exploded view of the device having a dome on the housing plug.  
         [0044]      FIG. 15  is an exploded view of the two bellows device showing the bellows connected directly to the top plate and the bottom plate.  
         [0045]      FIG. 16  is an exploded view of the device having one bellows connected directly to the top and bottom plates.  
         [0046]      FIG. 17  is a bottom view of the top plate of the device of  FIG. 16  shown for the right or left insertion.  
         [0047]      FIG. 18  is an exploded view of the device having one bellows similar to  FIG. 14 .  
         [0048]      FIG. 19  is a bottom view of the top plate of the device of  FIG. 18  shown for right or left insertion.  
         [0049]      FIG. 20  is a partial cut-away view of the device having a single bellows and insulator panels above and below the bellows.  
         [0050]      FIG. 21  is a bottom view of the top plate of the device shown for right or left insertion.  
         [0051]      FIG. 22  is a perspective view of the surgical procedure being performed posteriorly. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0052]     Referring now to  FIGS. 1-5 , the device of the present invention has a top plate  10  and a spaced-apart bottom plate  12 . At least one bellows  14  is disposed between the top plate  10  and the bottom plate  12 . In a preferred embodiment, the top plate  10  and the bottom plate  12  are kidney shaped and two bellows  14  are disposed side-by-side between the plates.  
         [0053]      FIG. 6  shows the components of a preferred embodiment of the present invention. The top plate  10  is formed with a plurality of spikes  16  formed on an upper surface. The spikes  16  engage the vertebrae of the spine immediately above the device when implanted in the patient. The lower surface of the top plate  10  has a well  18  formed therein. An insulator panel  20  formed from a bearing material such as polyacetal or UHMWPE is received in the well  18 . Other materials known to persons skilled in the art may be used. This insulator panel separates the bellows  14  from the top plate  10  and prevents the formation of an electrolitic reaction due to the presence of dissimilar metals. The top and bottom plates may be made from metal which are not the same as the bellows. If an electrolitic reaction were to occur, the device could be damaged by corrosion and failure could occur.  
         [0054]     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 .  
         [0055]     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.  
         [0056]     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.  
         [0057]     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.  
         [0058]     The device  10  is compressible anteriorly/posteriorly from approximately 0°-4° as shown in  FIG. 7 . As shown in  FIG. 8 , the device is compressible approximately 0°-3° left/right. The assembly flexes in the compressive modes substantially along a longitudinal axis of the bellows. Because of the low coefficient of the friction of the material from which the insulator panel  20  is formed, the top plate  10  and the bottom plate  12  may rotate torsionally approximately 1°-6°. Each plate may rotate independently of the other plate or both may rotate simultaneously ( FIGS. 9-13 ). The multi-dimensional movement of the device provides movement of the vertebrae of the surgically-corrected spine which simulates movement of a person with a healthy spine.  
         [0059]     The device does not require any fluid to be contained within the bellows.  
         [0060]     The device may be made without the insulator. As shown in  FIG. 14 , the housing plug  22  is formed with an arch or dome  36  on the top surface. The dome contacts the inside of the well  18  in the top plate  10 . The bottom of the bellows  14  is received directly in the well in the bottom plate  12 . The device with the dome top housing plug also is compressible approximately 0°-4° anteriorly/posteriorly and approximately 0°-3° left/right. Due to the domed surface, the device also has transitional rotation of approximately 1°-6° between the top plate and the bottom plate circumferentially about the longitudinal axis of the bellows.  
         [0061]     The device may also be made without a housing plug, an insulator, a housing or a locator plate. As shown in  FIG. 15 , the bellows  14  are directly connected to the respective top plate  10  and lower plate  12 . This device is compressible approximately 0°-4° anteriorly/posteriorly and approximately 0°-3° left/right. However, the device has no translational rotation properties.  
         [0062]     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.  
         [0063]     A device formed having only one bellows may also be made. As shown in  FIG. 16 , the device is essentially one-half of the device in  FIG. 15 . There is only a bellows  14  connected directly to the top plate  10  and the bottom plate  12 . The device is formed as being for the right side or the left side of the spine as shown in  FIG. 17 .  
         [0064]     Similarly, as shown in  FIGS. 18-19 , a single bellows device similar to the device of  FIG. 14  may be made. The device has the dome  36  on the housing plug  22 . It also is formed for the right side or the left side of the spine. The device has torsional rotation of approximately 1°-6° of the top plate. The device is compressible approximately 0°-4° anteriorly/posteriorly and is compressible approximately 0°-3° left/right as the device is described above.  
         [0065]     Also, a single bellows device having the insulator panel  20  may be made as shown in  FIGS. 20-21 . The device is formed for the right side or the left side of the spine. It has the torsional rotation of approximately 1°-6° of the top plate and the bottom plate. The device is compressible approximately 0°-4° anteriorly/posteriorly and is compressible approximately 0°-3° left/right as the device described above and shown, as a double bellows device in  FIGS. 3-6 .  
         [0066]     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.  
         [0067]     Techniques to be used by the surgeon will be developed and refined.  
         [0068]     The device may also be implanted in the spine of a human being by making a midline incision posteriorly ( FIG. 22 ). The damaged region of the spine is removed. A device having a single bellows and configured to fit the right side of the spine is inserted into the spine where the damaged region had been removed. A device having a single bellows and configured to fit the left side of the spine is inserted where the damaged region had been removed. The two inserted devices are adjacent to one another.  
         [0069]     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.  
         [0070]     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.  
         [0071]     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.  
         [0072]     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.