Patent Application
20160242823
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'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.
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.
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 '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.
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 '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.
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.
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.
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
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.
| Number | Date | Country | |
|---|---|---|---|
| 62118087 | Feb 2015 | US | |
| 62173848 | Jun 2015 | US |
