Abstract:
A surgically implanted spinal stabilization system uses posterior anchor hooks attached to vertebrae to retain elastic bands to retain flexibility and mobility while maintaining alignment and preventing excessive motion and deformity. The elastic bands may parallel the longitudinal axis of the spine, or, for enhanced promotion of alignment, they may also arranged in a diagonally crossing configuration. Multi-level fixation can be achieved using the spinal stabilization system with longer elastic bands. A method of applying the spinal stabilization system using an elastic band application tool facilitates simple, rapid application of the system to a patient.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to devices used to provide spinal stabilization and more particularly to systems for spinal stabilization allowing flexibility of the vertebrae.  
         [0003]     2. Description of Related Art  
         [0004]     The human spine is comprised of 33 stacked vertebrae extending from the base of the skull to the tailbone with cartilaginous disks sandwiched between each two adjacent vertebrae providing a cushion and easing movement of the vertebrae relative to each other. In a healthy spine, this interconnected arrangement of vertebrae and disks supports loads while remaining highly flexible—since each vertebra can move with respect to the adjoining vertebrae, the spine can bend and twist to a remarkable degree. However, with a spinal injury, deformity or degeneration, even at a single disk level, the spine&#39;s ability to support load can be greatly compromised. As a result, a person&#39;s spinal injury often leads to great discomfort when standing and an inability to lift heavy objects.  
         [0005]     While spinal injuries such as herniated disks are currently treatable, certain treatments have undesirable results. Traditionally, incompetent disks have been surgically treated by solidly fusing the vertebrae adjacent to the injured disk or disks. In this method, two or more vertebrae are fused with bone grafts and internal devices such as cages or metal screws and rods to heal into a single solid bone. This traditional spinal fusion method is also used in certain instances to treat injuries to vertebrae, abnormal curvatures of the spine (scoliosis or kyphosis), and weak or unstable spine caused by degenerative changes, infections or tumors. While this traditional method of treatment for spinal injuries can restore the strength of the spinal column and its proper curvature, the fusion of adjacent vertebrae restores strength at the expense of flexibility. Therefore, a person who has undergone traditional vertebral fusion surgery will lose a degree of bending and twisting flexibility in the spine. Also, the disks adjacent to the fused levels degenerate at an increased rate, often requiring extension of the fusion. Furthermore the traditional fusion treatment (and its accompanying lack of flexibility) is essentially irreversible. Pseudoarthrosis (or failed fusion) also is a risk of all attempts at achieving solid bony fusion, usually requiring reoperation.  
         [0006]     Certain spinal conditions may benefit from surgical stabilization to maintain posterior curvature (lordosis) and alignment. This is particularly true after posterior decompressive surgery procedures that remove bone, ligaments, joints and disks to relieve pressure on nervous tissues. Such procedures can weaken the spinal structure and result in post-operative increase in misalignments or reversal of normal lordosis. Fusion would not be required in these situations if a posterior, flexible device that could preserve normal spinal alignment was implanted. This would be an advantage over fusion because more normal motion would be preserved, no boney fusion growth would be required, and adjacent level integrity would not be threatened.  
         [0007]     Others have attempted to address the shortcomings of the traditional spinal fusion method, however, these attempts have had limited success and introduced further shortcomings. Several prior art systems employ a complex array of rods, springs and posts to position the spinal column of a wearer as desired. In these systems, two rods parallel to the desired axial configuration of the spine are attached to the spine with posts attached to each vertebra. These devices are designed to be removable and allow some degree of flexibility while maintaining the proper alignment and support of the spine. However, these devices are complex, involving a large number of component parts. This complexity would undesirably lead to long application and removal times and the need for extensive training by the applying surgeon. Furthermore, the rigid alignment rods and other hardware would negatively impact flexibility (though not as much as the traditional vertebral fusion method).  
         [0008]     Other devices attempting to address the shortcomings of the traditional spinal fusion method have done so by joining vertebrae together with cables or dampers attached to pairs of posts attached to individual vertebrae. In these prior art devices, the cables or dampers may run between vertebrae along the axis of the spine or they may run in a crossing pattern between vertebrae. In some of the cable-based spinal stabilization devices, dampening devices have been substituted for the cables running between vertebrae parallel to the axis of the spine. These prior art devices address the traditional vertebral fusion&#39;s removability shortcoming but do not address the flexibility shortcomings. Tension in the cables used in these devices provides compression across the disk space. Therefore, these devices restrict the wearer&#39;s range of mobility in bending and flexure. Moreover, since the cables used in these devices are much less elastic than the cartilage, ligaments, and other soft tissues that define mobility in a healthy spine, these devices create an unnatural firm stop at the limits of movement  
         [0009]     Therefore, there is a need for a spinal stabilization device that is simple, facilitating ease of application, permits the wearer to retain nearly a full range of mobility and flexibility in the spine, and is removable.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention addresses the shortcomings of the prior art, by providing a system for posterior spinal stabilization that is simple, permits the user to retain a large range of spinal flexibility and mobility while preventing excessive motion and maintaining proper alignment, and is removable. The system is also universally applicable to all levels of the human spine.  
         [0011]     The spinal stabilizer of the present invention is a posterior spinal implant system comprising at least one elastic band retained by at least one pair of anchor hooks. The small number of component elements in the spinal stabilization system of the present invention facilitates relatively quick surgical application and removal times. The flexible nature of the elastic bands allows flexibility and mobility of the wearer&#39;s spine while simultaneously maintaining alignment and preventing excessive motion and deformity  
         [0012]     The anchor hooks of the present invention are of a material, such as titanium, that is strong, durable, and can be safely surgically implanted. The anchor hooks of the present invention are to be screwed into pilot holes drilled in locations appropriate to the level of the vertebra to be flexibly connected. The screw locations will preferably be in the lateral masses for cervical vertebrae and in the pedicles in lumbar and thoracic vertebrae. Varying sizes of screw threads and anchor hooks may be used in the system of the present invention to facilitate application on different sized vertebrae along the length of the spine.  
         [0013]     The spinal stabilization system of the present invention comprises three different types of anchor hooks: eye hooks and double hooks and multiple hooks. Eye hooks comprise a crimpable hook section connected to the head of a screw thread. The upper surface of the crimpable hook section has a groove in it to mate in the correct alignment with an elastic band application tool. Eye hooks are oriented so that the open end of the crimpable hook section faces away from the center of fixation. Double hooks comprise two crimpable hook sections connected to the head of a screw thread. Multi-hooks will be able to crimp over three bands oriented in different directions when crisscross banding is performed. Depending on the affected vertebrae and the desired treatment, eye hooks may be used alone to flexibly connect two adjacent vertebrae or in conjunction with double hooks for multi-level fixation. Multi-level fixation may be used to prevent post laminectomy kyphosis and maintain decompressive lordosis. All hooks are configured to be crimped around the elastic bands. The crimpable hook sections hooks feature a recess at the end of the crimpable hook section adjacent to the head of the screw thread and a tapered tip at the opposite end of the crimpable hook section. The recess facilitates application and retention of the elastic band to the hook shaped portion. The tapered tip on the elastic band retaining portion allows for flush closure when the elastic band retaining portions are crimped around an elastic band, preventing release of the elastic band.  
         [0014]     By combining different sizes and resistances of elastic bands with different sizes and types of anchor hooks, multiple embodiments of the present invention can be made. For example, a first embodiment representing treatment for a simple case in which two adjacent vertebrae are to be flexibly connected, two pairs of eye-hooks (one pair per vertebra) would be screwed into pilot holes drilled into the appropriate locations on the vertebrae. The first embodiment further comprises a pair of elastic bands with the desired length and resistance properties. Each of the elastic bands parallels the longitudinal axis of the spine and connects an eye-hook on one vertebra with the corresponding eye-hook on the other vertebra. A second, slightly more complex embodiment could be used to flexibly connect two adjacent vertebrae where enhanced promotion of alignment is desired. The second embodiment of the invention comprises all of the elements of the first embodiment of the invention arranged as in the first embodiment of the invention, and further comprises a second pair of elastic bands, with the desired length and resistance for diagonal use, arranged in a crossing diagonal pattern between the anchor hooks in the vertebrae (i.e. one elastic band of the second pair would be retained by the upper left anchor and the lower right anchor and the second elastic band of the second pair would be retained by the upper right anchor and the lower left anchor).  
         [0015]     Additional embodiments of the present invention could provide stabilization to more than two vertebrae. For example, a third embodiment of the invention could provide multilevel flexible connection of the spine by flexibly attaching three or more vertebrae. The third embodiment comprises two pairs of eye hooks, one pair for each of the upper and lower vertebrae to be flexibly connected plus one pair of double hooks for each intermediate vertebra to be flexibly connected. A pair of elastic bands of the desired length parallels the longitudinal axis of the spine and is retained by the anchor hooks. One of the elastic bands connect all of the anchor hooks on the left side (in relation to the longitudinal axis of the spine) of the spinal column, and the other of the pair of elastic bands would connect all of the anchor hooks on the right side (in relation to the longitudinal axis of the spine) of the spinal column. A fourth embodiment of the invention could provide multi-level fixation with enhanced promotion of alignment. This fourth embodiment combines the multilevel stabilization arrangement of the third embodiment with additional pairs of elastic bands, arranged in a crossing diagonal pattern between adjacent vertebrae as in the second embodiment. These four embodiments provide examples of several of the spinal stabilization arrangements possible within the scope of the present invention. However, it should be recognized that many other combinations of the components of the present invention, may be made. While not individually listed, these combinations are within the spirit and scope of the present invention.  
         [0016]     The elastic bands of the spinal stabilization system of the present invention are composed of a material that allows flexibility to a limit while being able to withstand millions of contractions with no significant degradation in flexibility. The material of the elastic bands must also be safe for implanting into humans and resist degradation. The preferred material for the elastic band is reinforced silastic, although other materials with the described properties are also considered within the scope of the present invention. Different thicknesses of elastic bands, with corresponding differences in resistance to extension may be used in the system of the present invention. Therefore, the system of the present invention is adaptable to provide varying degrees of mobility and flexibility depending on the desired treatment. The elastic bands may be color coded by resistance to facilitate application of the desired resistance level by the applying physician  
         [0017]     Several lengths of elastic bands may be employed in the spinal stabilization system of the present invention. The various lengths of elastic bands allow the spinal stabilization system to be applied at any desired location along the length of a wearer&#39;s spine: shorter bands would be used on cervical vertebrae, and progressively longer sized bands would be used on lower vertebrae in the thoracic and lumbar regions. Still longer elastic bands would be used in the system of the present invention to accomplish multi-level fixation. In multi-level fixation, more than two vertebrae would be flexibly connected by the system of the present invention with a pair of eye hooks anchored into the upper vertebra to be flexibly connected, a pair of double hooks anchored in each of the intermediate vertebrae to be flexibly connected, and a pair of eye hooks anchored into the lower vertebra to be flexibly connected. The elastic bands of the present invention will further comprise a continuous radio opaque stripe. This radio opaque stripe would allow the elastic bands of the present invention to be monitored by x-ray. A breakage of the elastic band would be visible as a discontinuity in the radio opaque stripe as viewed on an x-ray image. Likewise, the position of the elastic bands relative to the anchor hooks could be monitored with x-ray imaging.  
         [0018]     The spinal stabilization system of the present invention is applied by screwing pairs of anchor hooks into corresponding pairs of pilot holes drilled in vertebrae. An elastic band application tool may then be used to stretch an elastic band running parallel to the axis of the spine, over anchor hooks in the upper and lower vertebrae to be flexibly connected. The elastic band application tool comprises two lever arms, a locking mechanism to hold the elastic band open the desired amount, an anchor hook interface to mate with grooves in the anchor hooks in tongue-in-groove fashion, and an elastic band rolling mechanism that slides the elastic band over the anchor hooks. Once the elastic band is properly positioned over the anchor hooks, a crimping tool is used to close the anchor hooks over the elastic band. If the spinal stabilization is a multilevel fixation, the elastic band is applied and secured, as described above, to the eye hooks in the upper and lower vertebrae to be flexibly connected. Then the elastic band is rolled over the double hooks in the intermediate vertebrae to be flexibly connected with the elastic band application tools. The double hooks are then crimped over the elastic band with a crimping tool. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a diagram showing a first embodiment of the spinal stabilization system of the present invention as applied to two vertebrae.  
         [0020]      FIG. 2  is a diagram showing a second embodiment of the spinal stabilization system of the present invention as applied to two vertebrae.  
         [0021]      FIG. 3  is diagram showing a third embodiment of the spinal stabilization system of the present invention as applied to several vertebrae.  
         [0022]      FIG. 4  is a diagram showing a fourth embodiment of the spinal stabilization system of the present invention as applied to several vertebrae.  
         [0023]      FIG. 5  is a side view diagram showing anchor hooks of the present invention.  
         [0024]      FIG. 6  is a side view diagram showing elastic bands of the present invention.  
         [0025]      FIGS. 7A and 7B  are diagrams showing application of an elastic band to anchor hooks using the method of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     The present invention provides a spinal stabilization system that overcomes the limitations of prior-art spinal stabilization systems. In the detailed description that follows, like element numerals are used to indicate like elements that appear in one or more of the drawings.  
         [0027]      FIG. 1  depicts a first embodiment of the system of the present invention. In the first embodiment, the spinal stabilization system of the present invention is a system for flexibly connecting an upper vertebra  10  and an adjacent lower vertebra  12 . The system of the first embodiment comprises: a left anchor hook  14  and a right anchor hook  16  attachable to the upper vertebra  10 , a left anchor hook  18  and a right anchor hook  20  attachable to the lower vertebra  12 , a first elastic band  22  retained by the left anchor hook  14  in the upper vertebra  10  and the left anchor hook  18  in the lower vertebra  12  and substantially parallel to the longitudinal axis of the spine, and a second elastic band  24  retained by the right anchor hook  16  in the upper vertebra  10  and the right anchor  20  hook in the lower vertebra  12  and substantially parallel to the longitudinal axis of the spine.  
         [0028]     As is evident from the first embodiment in  FIG. 1 , the system of the present invention flexibly attaches two vertebrae  10 ,  12  while allowing the vertebrae to move relative to each other to the extent of the elasticity of the elastic bands  22 ,  24 , thereby allowing the wearer to have a high degree of mobility and flexibility. Further, the few component parts of the present invention facilitate ease of application.  FIG. 1  depicts the system of the present device as applied to two lumbar vertebrae  10 ,  12 , with the anchor hooks  14 ,  16 ,  18 ,  20  attached to the vertebrae  10 ,  12  at the pedicle location  26 . However, it should be recognized that the system of the present invention may be applied to any two adjacent vertebrae along the length of the spine. The location of the anchor hooks, however would vary from lateral masses in the cervical vertebrae to pedicles  26  in the thoracic and lumbar vertebrae.  
         [0029]     A second embodiment of the present invention is depicted in  FIG. 2 . The second embodiment flexibly connects two vertebrae  10 ,  12  while providing enhanced promotion of alignment and preventing listhesis. The second embodiment comprises all of the elements of the first embodiment, as depicted in  FIG. 1 , and further comprises: a third elastic band  28  retained by the left anchor hook  14  in the upper vertebra  10  and the right anchor hook  20  in the lower vertebra  12 ; and a fourth elastic band  30  retained by the right anchor hook  16  in the upper vertebra  10  and the left anchor hook  18  in the lower vertebra  12 .  
         [0030]     The second embodiment of the present invention allows flexibility and mobility while enhancing promotion of alignment. Further, the second embodiment of the present invention has very few component elements as compared with complex rod-based systems of the prior art. As with the first embodiment of the invention, the second embodiment may be applied, by varying attachment locations for the anchor hooks, to any two adjacent vertebrae along the length of the spine.  
         [0031]     A third embodiment of the present invention is depicted in  FIG. 3 . The third embodiment of the present invention allows flexible connection of more than two vertebrae  32 ,  34 ,  36 . The third embodiment of the present invention comprises: a left anchor hook  38  and a right anchor hook  40  attachable to an upper vertebra  32 ; a left anchor hook  42  and a right anchor hook  44  attachable to a lower vertebra  34 ; a left anchor hook  46  and a right anchor hook  48  attachable to each of the at least one intermediate vertebrae  36 ; a first elastic band  50  retained by the left anchor hook  38  in the upper vertebra  32 , the left anchor hooks  46  in the at least one intermediate vertebrae  36 , and the left anchor hook  42  in the lower vertebra  34 , wherein the first elastic band  50  is substantially parallel to the longitudinal axis of the spine; and a second elastic band  52  retained by the right anchor hook  40  in the upper vertebra  32 , the right anchor hooks  48  in the at least one intermediate vertebrae  36 , and the right anchor hook  44  in the lower vertebra  34 , wherein the second elastic band  52  is substantially parallel to the longitudinal axis of the spine.  
         [0032]     When multi-level fixation is desired, the third embodiment of the present invention allows the user to retain mobility and flexibility while providing support to the spine. The third embodiment of the present invention has fewer component elements than complex prior art rod-based devices, thereby facilitating ease of application and removal.  
         [0033]     A fourth embodiment of the present invention is depicted in  FIG. 4 . The fourth embodiment of the present invention flexibly attaches more than two vertebrae  34 ,  36 ,  38  while enhancing promotion of alignment. The fourth embodiment comprises all of the elements of the third embodiment, as depicted in  FIG. 3 , and further comprises: at least one pair of diagonal crossing elastic bands  54 ,  56  wherein one  54  of each of the at least one pair of diagonal crossing elastic bands is retained by the right anchor hook  44  in a flexibly connected vertebra  34  and the left anchor hook  46  in an adjacent flexibly connected vertebra  36  and the other  56  of each of the at least one pair of diagonal crossing elastic bands is retained by the left anchor hook  42  in the flexibly connected vertebra  34  and the right anchor hook  48  in the adjacent flexibly connected vertebra  36 .  
         [0034]      FIG. 5  depicts two types of anchor hooks  58  used in the system of the present invention. Each anchor hook  58  attached to the upper and lower vertebrae to be flexibly connected in each of the embodiments described above is an eye hook  60 . Each eye hook  60  comprises: a crimpable hook section  62  affixed to a screw thread  64 , and wherein the crimpable hook section  62  further comprises a recess  66  where the crimpable hook section meets the screw thread and a tapered tip  68  opposite where the crimpable hook section meets the screw thread. The recess  66  in the eye hook  60  facilitates application of an elastic band to the eye hook  60 . Once an elastic band, (or in embodiments of the system with enhanced promotion of alignment, more than one elastic band) is applied to the eye hook  60 , a crimping tool is used to close the crimpable hook section  62  over the elastic band. The tapered tip  68  allows the crimpable hook section  62  to be crimped flushly around the elastic band. The eye hooks  60  are to be attached to the individual vertebrae such that the end of the crimpable hook section  62  with the tapered tip  68  faces away from the center of fixation (i.e. the tapered tip  68  will be facing up for eye hooks  60  attached to an upper vertebra and facing down for eye hooks attached to a lower vertebra). For ease of applying elastic bands to the eye hooks  60 , the eye hooks  60  preferably further comprise a groove  70  in the crimpable hook section  62  configured to interface with an elastic band application tool.  
         [0035]     The anchor hooks  58  used in intermediate vertebrae in embodiments of the present invention providing multi-level fixation are double hooks  72 . The double hooks each comprise two crimpable hook sections  74  affixed to a screw thread  76 . The crimpable hook sections  74  of the double hooks  72  each further comprise a recess  78  where the crimpable hook section  74  meets the screw thread  76  and a tapered tip  80  opposite where the crimpable hook section  74  meets the screw thread  76 . The recess  78  in each crimpable hook section  74  of the double hook  72  facilitates application of an elastic band to the double hook  72 . Once an elastic band (or in embodiments of the system with enhanced promotion of alignment, more than one elastic band) is applied to each crimpable hook section  74  of the double hook  72 , a crimping tool is used to close the crimpable hook sections  74  over the band. The tapered tip  80  allows each crimpable hook section  74  to be crimped flushly around the elastic band. The double hooks  72  are to be attached to the individual vertebrae oriented such that the crimpable hook sections  74  would open perpendicularly to the longitudinal axis of the spine, thereby allowing elastic bands running parallel to the longitudinal axis of the spine to be easily retained by the crimpable hook sections  74 . Although not depicted, another type of anchor hook, a multi-hook, may be used where the embodiment of the spinal stabilization system of the present invention results in three bands oriented in different directions being retained by the same anchor hook.  
         [0036]     The anchor hooks  58  must be composed of a material that is strong, durable, and capable of being implanted into humans without adverse reaction. The anchor hooks  58  of the present invention are preferably composed of titanium. Multiple sizes of anchor hooks  58  are contemplated within the scope of the present invention. The treating physician or surgeon can select an anchor hook  58  of a size appropriate to the vertebra to which it will be attached. Therefore, through the use of multiple sizes of anchor hooks  58 , the system of the present invention is adaptable to flexibly connect the various sizes of vertebrae along the length of a spine. Likewise, the system of the present invention is adaptable to being applied to varying sizes of vertebrae in spines of people of different ages and builds.  
         [0037]      FIG. 6  depicts the elastic bands  82  to be used in the system of the present invention. The elastic bands  82  of the present invention are composed of a material that allows flexibility and is capable of withstanding millions of extension and contraction cycles. The material of the elastic bands  82  must also be capable of being implanted into humans with little chance of an adverse reaction. The elastic bands  82  of the present invention are preferably composed of reinforced silastic. Elastic bands  82  of varying lengths  84 ,  86 ,  88 ,  90 ,  92 ,  94  and resistances are contemplated within the scope of the present invention. Preferably, the elastic bands used in a particular application will be of a length corresponding to a desired distance between the anchor hooks that retain the band. Different lengths of elastic bands  82  will correspond to their intended area of use in the spine. For example, elastic bands for use in the cervical region  84 ,  86  will be shortest, and elastic bands for use in the thoracic  88 ,  90  and lumbar  92  regions will be progressively longer. Still longer elastic bands  94  are used in multi-level fixation. The thickness of an elastic band  82  will determine its resistance to extension. Multiple thicknesses and therefore resistances of elastic bands  82  may be chosen for each length of elastic band  82  depending on the desired resistance to extension for the treatment chosen. Alternatively, bands could be with internal variations in resistance while maintaining uniform thickness. Preferably the elastic bands  82  are color-coded by resistance to facilitate selection of the elastic band  82  with the desired flexion capability. Therefore, the system of the present invention is adaptable to meet differing flexibility and mobility needs. The elastic bands  82  may further comprise a continuous radio opaque stripe  96 . The radio opaque stripe  96  allows for a diagnostic review of the elastic bands  82  with X-ray imaging. Such a review could detect breakage or improper application of the elastic bands  82 .  
         [0038]      FIG. 7A  depicts application of the spinal stabilization system through a novel method of the present invention. The method of applying the system of the present invention comprises the steps of: drilling two pilot holes  98  in each vertebra  100  to be flexibly attached; applying an anchor hook  102  to each pilot hole  98  in the vertebrae  100  to be flexibly attached; applying elastic bands  104  to the anchor hooks  102 ; and crimping the anchor hooks  102  to retain the elastic bands  104 . Pilot holes  98  are drilled in the desired location on the vertebrae  100  to be flexibly attached. The pilot hole  98  location may vary depending on the region of the spine to be flexibly attached. Preferably pilot holes  98  will be drilled in lateral masses in cervical vertebrae and in pedicles in lumbar and thoracic vertebrae. Anchor hooks  102  are then attached to the vertebrae  100  by screwing each anchor hook  102  into a pilot hole  98 . Elastic bands  104  are then applied to the anchor hooks  102  as appropriate for the desired fixation. Preferably, an elastic band application tool  106  would be used to apply the elastic bands  104  to the desired anchor hooks  102 . The elastic band application tool  106  comprises two lever arms  108 , an anchor hook interface  110 , a locking mechanism  112 , and an elastic band rolling mechanism  114 . An elastic band  104  can be picked up and extended to the desired length with the elastic band application tool  106 . The locking mechanism  112  on the elastic band application tool  106 , here depicted as a ratchet lock, then maintains the proper extension of the elastic band  104 . The elastic band application tool  106  is then mated with the anchor hooks  102  to which the elastic band  104  will be applied. The anchor hook interface  110  on the elastic band application tool  106  mates with the groove  70  in each of the anchor hooks  102  in tongue-in-groove fashion. This mating is shown in closer detail in  FIG. 7B . This mating allows proper positioning of the elastic band  104  to facilitate its application. The elastic band rolling mechanism  114 , here depicted as a lever that slides the elastic band  104  onto the anchor hooks  102 , then rolls the elastic band  104  off of the elastic band application tool  106  and onto the anchor hooks  102 . Once the elastic band  104  has been applied to the anchor hooks  102 , the anchor hooks  102  are crimped closed around the elastic band  104 . The method of the present invention can be used to apply elastic bands  104  to eye hooks and double hooks.  
         [0039]     Having thus described several embodiments of the spinal stabilization system, it should be apparent to those skilled in the art that certain advantages of the device have been achieved. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention. The invention is further defined by the following claims.