Patent Publication Number: US-2016242823-A1

Title: Interspinous process spacer device including locking ring

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 62/118,087, titled, Interspinous Process Spacer Device Including Bone Graft Fusion Ports, filed Feb. 19, 2015, and U.S. Provisional Patent Application Ser. No. 62/173,848, titled, Interspinous Process Spacer Device Including Locking Ring, filed Jun. 10, 2015. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to an interspinous process spacer device that is operable to be inserted between the spinous process of adjacent vertebrae and, more particularly, to an interspinous process spacer device that is operable to be percutaneously inserted between the spinous process of adjacent vertebrae using minimally invasive surgical procedures, where the spacer device includes a tapered front-end portion having mounting turns, an annular spacer ring and a center channel having ports that allow bone graft material to be provided through the device and between the front-end portion and the spacer ring so as to allow bone to span between the adjacent spinous processes. 
     2. Discussion of the Related Art 
     The human spine includes a series of vertebrae interconnected by connective tissue referred to as discs that act as a cushion between the vertebrae. The discs allow for movement of the vertebrae so that the back can bend and rotate. The vertebra includes a bony spinous process that protrudes towards the back. 
     The intervertebral disc is an active organ in which the normal and pathologic anatomies are well known, but the normal and pathologic physiologies have not been greatly understood. The intervertebral disc permits rhythmic motions required of all vertebrate animals in their various forms of locomotion. The disc is a high-pressure system composed primarily of absorbed water, an outer multilayered circumferential annulus of strong, flexible, but essentially inelastic collagen fibers, and an inner core of a hydrogel called the nucleus pulposus. The swelling of the contained hydrogel creates the high pressure that tightens the annular fibers and its laminations. Degeneration of discs in humans is typically a slow, complex process involving essentially all of the mechanical and physiologic components with loss of water holding capacity of the disc. Discogenic pain arises from either component, but is primarily due to altered chemistry. When this pain is severely disabling and unyielding, the preferred contemporary treatments are primarily surgical, particularly fusion and/or disc replacement. 
     Annular collagen fibers are arranged in circumferential belts or laminations inserting strongly and tangentially in right-handed and left-handed angulated patches into each adjacent vertebral body. Inside the annular ring is contained an aggrecan, glycosaminoglycan, a protein-sugar complex gel having great hygroscopic ability to hold water. The swelling pressure of the gel of the nucleus maintains the pressure within the annulus, forcing the vertebrae apart and tightening the annular fibers. This tightening provides the primary mechanical stability and flexibility of each disc of the spinal column. Further, the angulated arrangement of the fibers also controls the segmental stability and flexibility of the motion segment. Therefore, the motion of each segment relates directly to the swelling capacity of the gel and secondarily to the tightness of intact annulus fibers. The same gel is also found in thin layers separating the annular laminar construction, providing some apparent elasticity and separating the laminations, reducing interlaminar torsional abrasion. With aging or degeneration, nucleus gel declines, while collagen content, including fibrosis, increases. 
     Disc degeneration, which involves matrix, collagen and aggrecan, usually begins with annular tears or alterations in the endplate nutritional pathways by mechanical or pathophysiologic means. However, the disc ultimately fails for cellular reasons. As a person ages, the discs in the spine go through a degenerative process that involves the gradual loss of the water holding capacity of the disc, referred to as desiccation. As a result of this loss of water, the disc space height may partially collapse, which may lead to chronic back pain disorders and/or leg pain as a result of the nerves being pinched. 
     Progressive injury and aging of the disc occurs normally in later life and abnormally after trauma or metabolic changes. In addition to the chemical effects on the free nerve endings as a source of discogenic pain, other degenerative factors may occur. Free nerve endings in the annular fibers may be stimulated by stretching as the disc degenerates, bulges, and as circumferential delamination of annular fibers occurs. This condition may lead to a number of problems, such as back pain. It has been shown that a person&#39;s disc is typically taller in the morning when a person awakes. This phenomenon may be due in part to the reduction of body weight forces on the disc when lying in a recumbent position overnight that causes the disc height to restore. Therefore, reduction of compressive forces on the disc may help to restore disc space height. 
     As discussed above, as a person ages, the discs of the spine degenerate, and the disc space height collapses. Further, the ligaments and facets of the spine degenerate as well resulting in hypertrophy or overgrowth of these structures. These structures are in close proximity to the nerves and spinal canal. The ligamentum flavum is found within the spinal canal and the facets are the posterior joints of the spinal that enable movement between vertebrae. Facet and ligamentum flavum hypertrophy can lead to central canal, lateral recess and or neural foramenal stenosis. The neural foramen is the opening between the vertebrae that allows the nerve from the spinal cord to pass through. Because the nerve(s) passes through the spinal canal and neural foramen, the nerve(s) will often get pinched leading to various types of back pain. Further, these problems often lead to difficulty walking. Patients typically respond by walking shorter distances, then sitting down, and flexing the spine by leaning over or by walking with the aid of a device, such as a cane, walker, shopping cart, etc., which helps to flex the spine. This condition is called neurogenic claudication and results from lumbar spinal stenosis. Neurogenic claudication is frequently seen in elderly patients who are often poor surgical candidates because they have many co-morbidities like diabetes, hypertension, coronary artery disease, and stroke. 
     Current surgical procedures for treating spinal stenosis require that the ligaments and bone that are causing the compression be removed surgically to take the pressure off of the nerves. Additionally, spinal structures such as the spinous processes that are not involved in the compression of the nerve are removed as well. The paraspinous muscles are also detached and frequently never return to their normal anatomical function due to scar formation and muscular denervation. This can lead to further problems resulting in spinal instability, adjacent segment pathology, scar formation and chronic pain conditions requiring additional surgery and cost of care. In many instances these patients develop debilitating spinal conditions that cannot be remedied with further surgery. 
     Recently, interspinous process spacers, such as the X-stop™, have been developed to address this pathology. Known interspinous process spacers operate by flexing the spine and opening the canal, lateral recess and foramen to take pressure off of the nerves. These devices typically can be useful for conditions of central canal and lateral recess stenosis or foramenal stenosis alone. The benefit is that they can be placed relatively easily with minimal destruction of the normal anatomy of the spine. These devices can also be potentially useful as an adjunct to minimally invasive laminectomy for stenosis where the spinous process is preserved. Interspinous process spacers can act as an adjunct device to minimally invasive laminectomy for stenosis to treat the foramenal stenosis component of this disorder. Following minimally invasive lumbar lam inectomy for stenosis, the interspinous process spacer could be placed between the preserved spinous processes of the spine. The result would be to address and treat the lateral or foramenal stenosis that could persist despite the decompression of the spinal canal. Nevertheless, current traditional interspinous process spacers require removal of the paraspinous muscles from the spinous processes and lamina, thus potentially adding to surgical morbidity and destabilization of the spine. Additionally they do not routinely allow for bone graft to be placed between adjacent spinous processes to achieve a spinal fusion linking vertebral bodies together. Fusion is needed to prevent the recurrence of spinal stenosis and helps to assure optimal long-term patient outcomes. 
     U.S. Pat. No. 7,879,039 issued Feb. 1, 2011 to Perez-Cruet et al., assigned to the assignee of this application and herein incorporated by reference, discloses an interspinous process spacer insertion device that positions an interspinous process spacer between the spinous process of adjacent vertebrae in a minimally invasive percutaneous surgical procedure, thus preventing the removal of paraspinal muscles for insertion of the device. The insertion device includes a trocar rod that extends through a cannulated sleeve. The spacer is attached to the end of the cannulated sleeve, where a trocar tip of the trocar rod extends through the spacer. The trocar rod is moved through the cannulated sleeve and an incision in the patient, and is positioned between the spinous process of the adjacent vertebra to align the spacer. The cannulated sleeve is then moved down the trocar rod so that the spacer slides between the spinous process, and the trocar rod is then withdrawn from the patient. Once the device is inserted, bone graft material can be applied down the insertion cannula and is squirted out around the device to form a fusion mass linking adjacent spinous processes. 
     SUMMARY OF THE INVENTION 
     The present disclosure describes a percutaneous interspinous process spacer device that is operable to be positioned between the spinous processes of adjacent vertebra and allow for bone graft fusion. In one embodiment, the spacer device is percutaneously inserted between the spinous process using minimally invasive surgical procedures. The spacer device includes a body portion having a central bore extending therethrough, where the body portion includes a cylindrical center portion, a tapered front-end portion at one end of the center portion and a threaded portion at an opposite end of the center portion. The spacer device also includes a spacer ring having an outer rim with a larger diameter than the center portion and an opening that allows the spacer ring to be slid onto the threaded portion. The spacer device further includes a securing member positioned against the spacer ring and including a threaded opening that allows the member to be threaded onto the threaded portion opposite to the center portion so that the spinous process can be tightly secured between the front-end portion and the spacer ring by compressing the adjacent spinous processes. 
     Additional features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a portion of a human spine showing several lumbar vertebra each including a spinous process, and showing a interspinous process spacer device positioned between two of the spinous process; 
         FIG. 2  is a side view of an interspinous process spacer device; 
         FIG. 3  is a cross-sectional view of the interspinous process spacer device shown in  FIG. 2 ; 
         FIG. 4  is a back-end view of the interspinous process spacer device shown in  FIG. 2 ; 
         FIG. 5  is an isometric view of another embodiment of an interspinous process spacer device including a threaded end portion; 
         FIG. 6  is a cross-sectional view of the interspinous process spacer device shown in  FIG. 5 ; 
         FIG. 7  is a front-end view of the interspinous process spacer device shown in  FIG. 5 ; 
         FIG. 8  is a broken-away, cross-sectional type view of an interspinous process spacer device affixed to an end of a percutaneous insertion interspinous process spacer device insertion assembly; 
         FIGS. 9 and 10  are two different isometric views of a portion of the human spine, and showing another interspinous process spacer device positioned between adjacent spinous process; 
         FIG. 11  is an isometric view of the interspinous process spacer device shown in  FIGS. 9 and 10 ; 
         FIG. 12  is an exploded view of the interspinous process spacer device shown in  FIG. 11 ; and 
         FIG. 13  is an isometric view of an interspinous process spacer device insertion assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following discussion of the embodiments of the invention directed to an interspinous process spacer device is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. For example, the spacer device disclosed herein has particular application to be inserted between the spinous process of adjacent vertebra in a minimally invasive percutaneously performed surgical procedure. However, the interspinous process spacer device disclosed herein will have application to be inserted using other surgical techniques. 
     As will be discussed in detail below, the present invention proposes an interspinous process spacer device that can be configured to be inserted percutaneously using, for example, an interspinous process spacer insertion device such as the one disclosed in the &#39;039 patent referenced above. Studies and investigations have shown that the surgical procedure for inserting the interspinous process spacer device to open the spinal canal, neural foramen and alleviate pain as discussed above can benefit by providing bone graft material around the spacer device so as to fuse the spinous process together. The present invention proposes a reconfigured interspinous process spacer device that allows percutaneous ease of insertion between the spinous process, and allows bone graft material to be easily placed in and around the spacer device that will ultimately harden and fuse the spinous processes together. 
       FIG. 1  is a broken-away side view of a lumbar portion of a human spine  10  showing several lumbar vertebra  12 . Each of the vertebra  12  includes a vertebral body  14 , where a disc  16  is shown between adjacent vertebral bodies  14 . Each vertebra  12  also includes a spinous process  18 , a lamina  20  and a foramen  22 . A cauda equine (or bunch of nerves) extends through a spinal canal formed by the vertebra  12 , where nerve roots  26  are shown extending from the cauda equina and through the neural foramen  22 . An interspinous process spacer device  28  is shown positioned between two of the spinous process  18 , and is intended to depict any of the embodiments of the interspinous process spacer devices discussed herein. 
       FIG. 2  is side view,  FIG. 3  is a cross-sectional view and  FIG. 4  is a back-end view of an interspinous process spacer device  30 , which can be used as the spacer device  28 . The spacer device  30  is a single piece member being made of a suitable surgical material, such as titanium or PEEK, and fabricated, such as by a suitable molding process, to have the configuration and shape as shown. The spacer device  30  includes a central cylindrical body portion  32 , an annular back-end plate  34  having a rounded edge  44 , and a tapered front-end portion  36  having a rounded tip  38 . The back-end plate  34  and the front-end portion  36  have a larger cross-sectional dimension than the body portion  32 , where a shoulder  40  is defined between the plate  34  and the body portion  32  and a shoulder  42  is defined between the front portion  36  and the body portion  32 , so that the spinous process  18  are locked between the front portion  36  and the plate  34 . A central bore  50  extends the length of the spacer device  30  through all of the back-end plate  34 , the body portion  32  and the tapered front portion  36 . The tapered portion  36  includes opposing flat portions  52  on opposite sides thereof. The back-end plate  34  includes a hexagonal-shaped opening  54  formed through a back surface  56  of the plate  34  that is concentric with the bore  50 . A series of ports  58 , here six, are positioned within the opening  54  and are circumferentially disposed around the internal bore  50 . The ports  58  are in communication with channels  60  that extend through the end plate  34  and the body portion  32  to a side surface of the body portion  32 , as shown. 
     The spacer device  30  is inserted between the spinous process  18  of the adjacent vertebra  12  using, for example, the insertion device disclosed in the &#39;039 patent, or otherwise, in an orientation so that the flat portions  52  line up with the spinous process  18 . Once the tapered portion  36  has extended beyond the spinous process  18  so that the spinous process  18  are positioned adjacent to the body portion  32  between the tapered portion  36  and the back-end plate  34 , the surgeon will use a suitable rotation tool (not shown) positioned within the opening  54  to rotate the spacer device  30  so that the flat portions  52  no longer align with the spinous process  18 , which causes the spinous process  18  to be locked between the back-end plate  34  and the tapered portion  36 . While in this position, the surgeon will then use a suitable delivery device (not shown) to administer bone graft material to the channels  60  through the ports  58  so that the bone graft material flows into the area around the body portion  32 , and thus around the spinous process  18 . Once the bone graft material hardens, the spinous processes  18  are fused together. 
       FIG. 5  is an isometric view,  FIG. 6  is a cross-sectional view and  FIG. 7  is a front-end view of an interspinous process spacer device  70  according to another embodiment, where like elements to the spacer device  30  are identified by the same reference number. In this embodiment, the tapered portion  36  is replaced with a tapered front portion  72  including turns  74 . Additionally, the back-end plate  34  is replaced with an annular back-end plate  76  that includes an outer hexagonal-shaped rim  78  that is used in connection with a rotation tool. Further, the channels  60  are provided in a different position and orientation relative to the body portion  32  and the back-end plate  76 , as shown. In this design, the tapered portion  72  allows better rotation of the device  70  after it is placed between the spinous process  18 . Additionally, the tool that is used to rotate the device  70  uses the outer hexagonal-shaped rim  78  of the back-end plate  76  instead of the internal opening  54 . 
       FIG. 8  is a cross-sectional type view of an illustration  80  showing an interspinous process spacer device insertion assembly  82  that is similar to those disclosed in the &#39;039 patent, where an interspinous process spacer device  84  is attached to the assembly  82 , and where the device  84  is shown positioned between adjacent spinous process  18 . The spacer device  84  is similar to the spacer devices  30  and  70 , where like elements are identified by the same reference number. The spacer device  84  includes an annular locking groove  86  formed in the annular rim  78 . 
     The insertion assembly  82  includes a trocar rod  88  that provides the insertion path for the spacer device  84  to be positioned between the spinous process  18 . The spacer device  84  is mounted to an end of a driver  90  that is concentric with the rod  88 , where the trocar rod  88  extends through an internal channel  92  in the driver  90  and the bore  50 . A bone graft reservoir  94  including an inner chamber  96  is positioned around the driver  90 , as shown, where the reservoir  94  includes an end portion  98  that is mounted within the locking groove  86 . Bone graft material  100  is provided within the chamber  96  proximate to the tip portion  92  and adjacent to an annular plunger  102  also positioned within the chamber  96 . Pressure applied to the annular plunger  102  forces the bone graft material  100  into the channels  60  and into the space around the body portion  32  and the spinous process  18 , as shown. 
       FIGS. 9 and 10  are broken-away, isometric views of part of the lumbar section of the human spine  10 , where another interspinous process spacer device  110  is shown positioned between two of the spinous process  18 .  FIG. 11  is an isometric view and  FIG. 12  is an exploded view of the spacer device  110  separated from the spine  10 . The spacer device  110  includes a body portion  112  having a cylindrical center portion  108 , a tapered front-end portion  114  at a front end of the body portion  112 , and a cylindrical threaded portion  120  at a back end of the body portion  112 , where a hexagonal-shaped bore  106  extends thought the body portion  112 . The front-end portion  114  includes mounting turns  116  for more readily inserting the device  110  between the spinous process  18  and bone spikes  118  for holding the device  110  to the spinous process  18 , such as shown in  FIGS. 9 and 10 . Part of the front-end portion  114  has a larger diameter than the center portion  108  so as to define a shoulder  104  therebetween that is positioned against the spinous process  18 , and the center portion  108  has a larger diameter than the threaded portion  120  to define a tapered shoulder  140  therebetween. A series of channels  138  are circumferentially disposed around the center portion  108  and are in fluid communication with the bore  106  so as to allow bone graft material to be delivered to the area around the body portion  112  once the device  110  is positioned between the spinous process  18  in the manner discussed above. 
     The spacer device  110  also includes a spacer ring  122  having an outer cylindrical rim portion  124 , a conical recess  126 , an opening  128  and bone spikes  130  for also holding the device  112  to the spinous process  18 , where the opening  128  has a larger diameter than the threaded portion  120  to allow the ring  122  to be slid onto the threaded portion  120  and be positioned against the shoulder  140  during the surgical procedure. The spacer device  110  also includes an annular securing member  132  including a front plate  142 , a hexagonal rim  136  extending rear-ward from the plate  142  and an annular threaded channel  134  extending through the member  132 . A suitable tool (not shown) can be used to engage the rim  136  to thread the member  132  onto the threaded portion  120  so that the member  132  is inserted into the recess  126  and engages the ring  122 . 
     During the surgical procedure for implanting the implant  110 , the body portion  112  is positioned between the spinous process  18  so that the shoulder  104  engages one side of the adjacent spinous process  18 . The spacer ring  122  is slid onto the threaded portion  120  until it engages the shoulder  140 . The member  132  is then threaded onto the threaded portion  120  to force the front-end portion  114  and the ring  122  against opposite side of the spinous process  18  and cause the bone spikes  118  and  130  to dig into the spinous process  18  and help hold the device  110  in place. 
       FIG. 13  is an illustration  150  showing an interspinous process spacer device insertion assembly  152  used for percutaneously inserting the spacer device  110 , or other spacer devices, between the adjacent spinous process  18 . The insertion assembly  152  includes a slide assembly  154  having a base portion  156  through which a rod  158  extends, where the slide assembly  154  can be locked at any suitable location along the rod  158  by a locking mechanism  160 . A stand  164  is secured to the base portion  156  by a rod  166  and includes a height adjustment knob  168  that controls the height of the stand  164  on the rod  166 , where the stand  164  will rest on a back of a patient  170 . The proper position for the slide assembly  154  is determined by known techniques, such as radiography, and once that position is identified, a positioning pin  172  is inserted into the patient  170  by rotating a control knob  176 , where pressure is applied to the pin  172  by a spring  178 . The insertion assembly  152  also includes a trocar  180  pivotally mounted to the slide assembly  154  and including a handle  182 . The spacer device  110  is mounted to an end of a driver  190  having a handle  194  that is also pivotally mounted to the slide assembly  154  and extends through a tube  192  in the trocar  180  where the driver  190  extends into the bore  106  of the device  110 . 
     The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims