Patent Application
20070016204
The present invention relates to a device for positioning between adjacent vertebrae of a spinal column of a patient, and, more particularly, to a device that is affixed to one or more vertebrae and which has a desired flexibility to allow motion between the vertebrae while providing support for the spinal column.
In the field of spinal devices and techniques, there is a normal practice today of implanting artificial discs or motion devices intermediate to adjacent vertebrae as an alternative to the fusing of those vertebrae together. Since the fusion technique results in a loss of motion between the fused vertebrae, the use of an artificial disc is a procedure that allows the patient to have more flexibility in the spinal column so as to carry out more of the normal movement and function of the spinal column and restore the normal anatomical position of the spinal column.
There is a potential for the artificial disc replacement to migrate or extrude outwardly from the intradiscal space after implantation therein, and therefore, there can be a device that is affixed to the anterior of the spinal column that prevents such extrusion or migration of the artificial disc from the implanted position. One such device is shown and described in U.S. Publication 2003/0204260 A1 where the device includes a barrier plate that is affixed to a vertebra with a link member that allows some movement of the intradiscal device.
As such, there is a realization that with such procedures of installing artificial discs, there is a need for some device that may be emplaced and located along the anterior of the spinal column for a number of purposes. First, an anterior device can act as a buttress to prevent the potential migration of the artificial disc out of its emplaced position intermediate adjacent vertebrae. Secondly, an anterior device can act as a revision device that can be installed following a failed motion device surgery of an artificial disc or, thirdly, an anterior device can be emplaced as a stand alone device.
In any of the foregoing uses of an anterior device, it would be advantageous for the device to have certain inherent flexibility so that the movement of the anterior region of the vertebrae is allowed and it would also be advantageous to be able to design a particular desired flexibility into the anterior device in order to meet the needs of the spinal column or particular use of the anterior device.
Accordingly, it would be advantageous to have an anterior spinal buttress device for a spinal column that can be attached to the anterior of a spinal column so as to allow a desired flexibility between the vertebrae of that spinal column.
Therefore, in accordance with the present invention there is an anterior spinal buttress device that is intended, for example, for the lumbar, thoracic and cervical sections of the spinal column and which provides a positive, yet flexible means of stabilizing the anterior of the spinal column. The device of this invention adds stability to the spinal column and also acts as an adhesion barrier or shield that prevents the growth of scar tissue.
The anterior spinal buttress device of the present invention includes a device that has opposed ends, that is, there are first and second ends, one of which is adapted to be attached to one of the adjacent vertebra and the other of which is adapted to be in close proximity to, and possible in direct contact with, the other adjacent vertebra of a spinal column. As alternate embodiment, the present spinal buttress device can span multiple vertebrae, that is, between vertebrae that are not adjacent to each other. In one embodiment, both of the first and second opposed ends are adapted to be attached to the adjacent vertebrae. In one described exemplary embodiment, the means of affixing either or both ends of the anterior spinal buttress device is by providing holes in both of the ends that accommodate bone screws that pass through the holes and the threads of the screws are screwed into the respective adjacent, or multiple vertebrae. Alternate means of affixation can include molybolts, wedges and the like.
Intermediate the first and second ends, there is a flexible region that allows the anterior spinal buttress device to flex in order to allow the adjacent vertebrae to also have a flexing action. The flexible region is specially constructed to be strong, monolithic device comprising, as an exemplary embodiment, a body having one or more slots formed therein in order to provide the necessary flexibility to the flexible region, and, of course, to the adjacent vertebrae.
For example, there may be single spiral slot or plurality of successive spiral slots formed in the flexible region of the anterior spinal buttress device in the manner as described in U.S. Pat. No. 5,488,761 of Leone, the disclosure of which is incorporated herein in its entirety by reference. As an alternate flexible region, the flexible region may comprise a body having alternating pairs of oppositely disposed slots formed therein with alternating pairs of slots being angularly offset, for example, at an angle of about 90 degrees as shown and described in co-pending patent application of Jaime Martinez, entitled “Flexible Shaft” and filed Jun. 3, 2005 as Ser. No. ______, the disclosure of which is hereby incorporated herein by reference in its entirety.
As a still further alternative, the flexible region may be constructed in accordance with the serpentine, helix-like slot forming the flexible member of U.S. Pat. No. 6,053,922 of Krause et al, and the disclosure of that patent is also incorporated herein in its entirety by reference.
The aforedescribed flexible region has the added advantage in that the degree of flexibility can be designed into the particular flexible region, that is, the flexibility of the region can be designed so as to have a desired flexibility by selecting among a number of parameters, such as, but not limited to, changing the spacing of the slots, selecting the material for making the region or changing the cross section of the body and any one or more of those selections can be made to design into the flexible region, the flexibility that is desired in the ultimate anterior spinal buttress device. Accordingly, the amount of flexibility of the anterior spinal buttress device of the present invention can be designed in accordance with the needs of the particular spinal column and/or use of the device.
The anterior spinal buttress device is also installed by means of a novel method. In particular, the ends of the device are both aligned and positioned so as to be proximate to or actually touching adjacent vertebrae and one of the ends of the device is attached to an adjacent vertebra by means of the bone screws passing through a hole or holes formed in that end and the threads screwed into the vertebra. As an alternate, both ends of the anterior spinal buttress device are attached to the adjacent vertebrae by the screws.
Thus, in the method, one of the ends of the anterior spinal buttress device is located abutting one of the adjacent vertebrae and firmly affixed thereto with the other end in close proximity to the adjacent vertebrae or in contact therewith. In a further embodiment, both of the opposed ends of the anterior spinal buttress device are affixed to the adjacent vertebrae with, in either embodiment, the flexible region between those ends providing the desired flexibility for the motion between the adjacent vertebrae.
Other features of the anterior spinal buttress device of the present invention and its method of installation will become more apparent in light of the following detailed description of a preferred embodiment thereof and as illustrated in the accompanying drawings.
Referring now to
On the posterior of the spinal column 16 there is a spinal stabilization system that is described more fully in co-pending U.S. patent application Ser. No. ______, filled ______ and entitled DYNAMIC SPINAL STABILIZATION SYSTEM AND METHOD and the disclosure of that patent application is hereby incorporated herein in its entirety by reference. In summary, however, the spinal stabilization system, for example, is affixed to the posterior of the spinal column 16 in order to allow some flexure of the adjacent vertebrae 12, 14 while stabilizing the spinal column. The spinal stabilization system includes a plurality of anchoring members 20, 22 that are affixed, respectively, to the vertebrae 12, 14. The anchoring members 20, 22 are identical and both include threads 24, 26 that are screwed into the vertebrae 12, 14 in order to solidly affix the anchoring members 20, 22 to the vertebrae 12, 14.
The anchoring members 20, 22 have external head ends 28, 30 extending from the threads 24, 26, respectively, and consequently also extending outwardly from the vertebrae 12, 14.
A flexible shaft 32 is affixed between the external head end 28 and 30 and is affixed thereto to span the adjacent vertebrae 12, 14.
As stated, the flexible shaft 32 may be specially constructed to be a strong, monolithic body having a slot or slots 34 formed therein in order to impart the flexibility to the otherwise relatively stiff shafts. The slot may be of the spiral type disclosed in Leone, U.S. Pat. No. 5,488,761, a serpentine helical slot as shown and described in Krause et al, U.S. Pat. No. 6,053,922 or may be of the type shown and described in copending U.S. patent application to Jaime Martinez, entitled “Flexible Shaft” having Ser. No. ______, filed Jun. 3, 2005, and the disclosure of the Leone, Krause et al patents and the Martinez application are hereby incorporated herein in their entirety by reference. That Martinez flexible shaft includes oppositely disposed slots in a body where alternating pairs of oppositely located slots are rotated 90 degrees about the outer periphery of the body such that the body can flex in multiple directions.
In any instance, the flexible shaft 32 can be designed for the desired flexibility by changing the configuration of the slot, the material of the body, the cross section of the body as well as other design changes so that the designer can determine the desired flexibility of the flexible shaft 32 depending upon the characteristics of the spinal column to which the flexible shaft 32 is installed.
Accordingly, while the spinal stabilization system is installed on the posterior side of the spinal column 16, the present invention, that is, the anterior spinal buttress device 10 is installed to the anterior side of the spinal column 16. As shown, the anterior spinal buttress device 10 includes opposed ends, that is, a first end 36 and a second end 38. As can be seen, the first and second ends 36, 38 abut up against the anterior of the adjacent vertebrae 12, 14 to effectively retain the disc 18 from any migration outwardly from its position between the adjacent vertebrae 12, 14. In the
The affixation of the second end 38 to the vertebra 24 can be carried out by a number of means, however, as shown, there is a bone screw 40 that passes through a suitable hole formed in the second end 38 and which is then screwed into the vertebra 14 to secure the second end 38 to the vertebra.
As such, only one end in the
The body 42 of the anterior spinal buttress device 10 intermediate the first and second ends 36, 38 is formed so as to have a predetermined flexibility in the same manner, generally, as the flexible shaft 32 such that there is one or more slots 44 formed in the body 42 intermediate the first and second ends 36, 38 in order to provide that inherent and desired flexibility. There is thus formed a flexible region 45 intermediate the first and second ends 36, 38.
The flexibility of the body 42 is therefore specially designed and constructed to be of a predetermined amount by the formation of a strong, monolithic body having a slot or slots 44 formed therein in order to impart the flexibility to the otherwise relatively stiff shafts.
Again, as with the flexible shaft 32, the slots 44 may be of the spiral type disclosed in Leone, U.S. Pat. No. 5,488,761 or may be of the serpentine helical-like slot as shown and described in Krause et al, U.S. Pat. No. 6,053,922 or may be of the type shown and described in the aforementioned copending U.S. patent application to Jaime Martinez, entitled “Flexible Shaft”. Therefore, in order to obtain the desired characteristic flexibility, the body 42 can be configured of a particular cross section, can have the shape and/or depth of the slot or slots varied or the material can be selected to as to achieve whatever flexibility is desired in order to suit the particular needs of the patient and/or the particular use of the anterior spinal buttress device 10.
Turning to
Accordingly, as can now be appreciated, the anterior spinal buttress device 10 is installed to the anterior of the spinal column 16 by means of screws that are screwed into the adjacent vertebrae, whether to one vertebra or both vertebrae with the flexible region 45 therebetween so that there is a desired flexibility brought about by the design and construction of the device, so as to allow a flexure between the adjacent vertebrae along the anterior of the spinal column. In the embodiment illustrated in
Turning now to
In
Next, in
The slots 66 are formed in the peripheral outer surface 70 of the tubular body 68 such that each slot 66 is less than 180 degrees about the peripheral outer surface 70 of the tubular body 68. Accordingly, since the pairs of slots 66 each are grouped in oppositely disposed slots 66, each slot is cut into the tubular body 68 and the slots 66 approach each other but terminate at ends 72 short of reaching the center of the tubular body 68, that is, the pairs of slots 66 are non-continuous and do not reach the longitudinal axis A as shown in
Therefore, between each of the ends 72 of a pair of slots 66 there are formed web sections 74 that separate the ends 72 of the pairs of slots 66. Thus, each pair of oppositely disposed slots 66 as illustrated in
The pairs of slots 66 are alternately angularly oriented with respect to each other around the outer peripheral surface of the tubular body 68, that is, each succeeding pair of oppositely disposed slots 66 is rotated or displaced a predetermined angular amount from the orientation of the succeeding pair of slots 66. In the embodiment shown in
While the angular displacement is illustrated in
The width w of the slots 66 can be predetermined in accordance with the desired flexibility of the completed anterior spinal buttress device 64, that is, the larger the width dimension w, the more flexible the flexible region 45 is and, consequently, also the eventual tubular body 68. The same is true of the depth of the slots 66 as the oppositely disposed slots approach each other nearing the midpoint or longitudinal axis A of the tubular body 68 i.e. the smaller the thickness t of the web sections 74 between the slots of each pair, the more flexible the flexible region 45 becomes. In one suitable embodiment, the thickness t of the web sections 74 is about the same, dimensionally, as the width w of the slots 66.
As can therefore be seen, the flexibility of the flexible region 45 can be different depending on the particular direction of flexing of the flexible region 45. One means of accomplishing that different flexibility would be to establish differing widths of pairs of slots 66 along two opposite sides of the tubular body 68 such that the flexibility in one direction of the pairs of slots 66 is different than the flexibility in another direction of motion, such as a direction at 90 degrees to the first direction. As such, the present anterior spinal buttress device 64 can be affixed to the anterior of the vertebrae of the patient in a particular orientation where the front to back flexibility of the spinal column can be different, and possibly more flexible, than the flexibility of the spinal column in a side to side direction.
The formation of the slots in this and other flexible regions can be accomplished by a variety of methods including milling the slots into the tubular body, using wire electrical discharge machining, water-jet machining, laser machining, spark erosion machining or rotary cutting machining. The material for the flexible regions and the anterior spinal buttress device itself can be any hard, rigid material including, but not limited to stainless steel, titanium, chrome cobalt molybdenum, polymers and carbon fiber composites.
While the present invention has been set forth in terms of a specific embodiment or embodiments, it will be understood that the anterior spinal buttress device and the method of installing the same disclosed herein may be modified or altered by those skilled in the art to other configurations. Accordingly, the invention is to be broadly construed and limited only by the scope and spirit of the claims appended hereto.
