JP2008517672A - Spinal motion retention assembly - Google Patents

Abstract

  A spinal motion retention assembly suitable for use in the spinal motion segment is disclosed, including a method of delivering and assembling the spinal motion retention assembly to the spinal motion segment through an axial channel formed by a transsacral approach. The spinal motion holding assembly uses a dual pivot. A number of different embodiments of spinal motion retention assemblies have been disclosed that include at least one component adapted to elastic deformation under compressive loading. The disclosed motility retention assembly provides dynamic stabilization (DS) of the spinal motion segment.

Description

  The present invention relates to an implantable device assembly, mounting system and method for accessing spinal motion segments via a minimally invasive transsacral approach (described in US Pat. No. 6,558,390, incorporated herein by reference) and Used to fix bones, position in the human spine, manage movement, stabilize spinal motion segments, relieve back pain, restore lumbar physiology, prevent degenerative disease progression or metastasis It relates to a procedure involving the placement of implantable components and assemblies. More specifically, the present invention relates to a spinal mobility retention assembly (MPA) that is transcutaneously introduced through tissue to an access point in the spine in a minimally invasive and less traumatic manner to treat the spine.

  The present invention is an extension of research attributed to Applicant's Trans1 Inc. (TranS1 Inc.), whose principal place of business is in Wilmington, NC. Most of the work is described in detail in a number of applications mentioned above and incorporated by reference into the present application. Therefore, the background of the invention described herein focuses on how the present invention deepens this series of research, rather than repeating every detail described in earlier applications.

  The spinal column is a complex system of bone segments (vertebral bodies and other bone segments), which are often separated from each other by intervertebral discs in the intervertebral space (sacral vertebrae are an exception). FIG. 1 shows various segments of the human spinal column from the side. In the context of the present invention, a “motion segment” refers to the adjacent vertebrae, ie, the upper and lower vertebral bodies, and whether it has an enucleated gap or an intact or damaged spinal disc. And a disc space separating two vertebral bodies. Each motion segment contributes to the overall flexibility of the spine, which is responsible for the overall ability of the spine to flex and support trunk and head motion.

  Conventionally, the vertebrae of the spinal cord are subdivided into a plurality of parts. Moving from the head to the tailbone, these parts are the cervical vertebra 104, the thoracic vertebra 108, the lumbar vertebra 112, the sacral vertebra 116, and the caudal vertebra 120. Individual vertebral bodies in the part are identified by a number starting from the vertebral body closest to the head. Of particular importance in this application are the vertebral bodies in the lumbar and sacral regions. Usually, in adults, the various vertebral bodies in the sacrum are fused, so it is sufficient and simply more convenient to refer to the sacrum rather than individual sacral components.

  Before entering into a more detailed discussion of the background of the invention, it is useful to show some of the standard medical terms. In the context of this discussion, the anterior refers to the anterior (ventral) side of the spine, the posterior refers to the posterior (dorsal) side of the spine; the cephalad refers to the patient's head. (Sometimes “upper”); caudal (sometimes “lower”) refers to a direction or position closer to the foot. Proximal and distal are defined in the context of this channel approach, as this application intends to access various vertebral bodies and intervertebral spaces through a preferred approach that enters from the sacrum and moves toward the head. . Thus, proximal is closer to the starting portion of the channel and hence to the foot or surgeon, and distal is further away from the starting portion of the channel and hence to the head, or farther from the surgeon. is there.

  Individual motion segments within the spinal column allow motion within restricted limits and protect the spinal cord. As a person walks, bends, rises, or makes other movements, the intervertebral disc is important to support and disperse large forces that penetrate the spinal column. Unfortunately, for many reasons, one or more discs in the spinal column do not function as intended in some humans. The reasons for disc failure range from congenital anomalies, disease, injury or degeneration due to aging. If the intervertebral disc does not function properly, the gap between adjacent vertebral bodies is reduced, which often results in further problems including pain.

  Currently, more than 700,000 surgical procedures are performed annually in the United States to treat low back pain. In 2004, it is estimated conservatively that more than 200,000 lumbar fusions will be performed in the United States and over 300,000 worldwide, representing approximately $ 1 billion in efforts to relieve patient pain. ing. About 60% of spine surgery is performed on the lumbar spine, of which about 80% are the lower lumbar vertebrae called the fourth lumbar vertebra ("L4"), the fifth lumbar vertebra ("L5") and the first sacral vertebra ("S1") is connected with. Persistent low back pain is often due to degeneration of the disc between L5 and S1 (see the edge between the lumbar 112 and the sacrum 116 in FIG. 1).

  Various treatments have been developed to alleviate the pain associated with disc defects. One class of solutions is to remove damaged discs and then to fuse two adjacent vertebral bodies with a permanent but inflexible gap, both with static stabilization. Called. As mentioned above, an estimated 300,000 fixed operations are performed every year. If one part is fixed, the bending ability in the motion segment is interrupted. Loss of normal physiological intervertebral disc function for a motion segment due to a fixed motion segment may be better than continuing to suffer from pain, but relieves pain and retains all or many normal functions of a healthy motion segment It would be better if possible.

  Another class of treatment is to attempt to repair the disc so that it resumes function with the intended disc space and mechanical properties. One type of repair is to replace the original damaged disc with an artificial disc. This type of therapy is called by different names such as dynamic stabilization or spinal motility retention.

(Work of the spine)
The continuous lumbar vertebral body, thoracic vertebral body and cervical vertebral body are connected to each other and separated by a spinal disc. Each spinal disc includes an outer shell of fibrocartilage surrounding a central mass “medullary nucleus” (or “nucleus” herein) that provides cushioning and cushioning of the compression force against the spinal column. The outer shell that surrounds the nucleus consists of the cartilaginous endplate attached to the opposing cortical bone endplates of the cranial and caudal vertebral bodies and the multilayered opposing collagen fibers that surround the nucleus pulposus and connect the cartilage endplates. Including “annulus” (or “annulus” herein). The natural physiological nucleus consists of hydrophilic (water-attracting) mucopolysaccharides and fiber bundles (protein polymers). The nucleus is relatively inelastic, but the annulus expands slightly outward and can accept loads applied axially to the spinal motion segment.

  The intervertebral disc is in front of the spinal canal and is located between the opposite end faces or endplates of the cranial and caudal vertebral bodies. The lower joint process is articulated with the upper joint process of the following vertebra in the caudal (ie, foot or lower) direction. Multiple ligaments (supraspinal ligament, interspinous ligament, anterior and posterior longitudinal ligaments and yellow ligament) hold the vertebrae in place but have limited movement. The collection of two vertebral bodies, the inserted spinal disc and the attached ligaments, muscles and facet joints are referred to as “spine motion segments”.

  The relatively large vertebral bodies and intervertebral discs located in the front of the spine support the majority of the spinal column load. Each vertebral body has a relatively strong cortical bone layer including the exposed outer surface of the vertebral body including the endplate and a relatively fragile cancellous bone including the center of the vertebral body.

  The nucleus pulposus that forms the center of the disc consists of 80% of the water absorbed by proteoglycans in the healthy adult spine. With aging, the nucleus becomes less fluid and more sticky, sometimes even in dehydration and contraction (sometimes called "isolated disc resorption") in many cases Causes severe pain. The spinal disc functions as a “buffer” between each vertebral body, minimizing the impact of motion on the spinal column, and degeneration of the disc, characterized by a decrease in nuclear water content, causes the disc to load into the annulus. The effect of transmission is lost. In addition, the rings tend to be thicker, dry and harder, have a reduced ability to elastically deform under load, and are prone to tearing or cracking, so when the ring cracks or tears Degeneration of one form of the intervertebral disc occurs. The crack may or may not be accompanied by protrusion of the nuclear material into the ring and beyond the ring. In addition to the general degenerative changes in the intervertebral connective tissue, the fissure itself can be the only morphological change, but the intervertebral disc crack can be painful and debilitating. Biochemicals contained in the nucleus are pushed out of the crack and stimulate nearby structures.

  Cracks may also occur with annulus formation or rupture of the annulus, where the nucleus expands outward or protrudes through the crack and contacts the spinal column or nerve (a “ruptured disc” or “escape” disc). For a constrained disc herniation, the nucleus can enter a portion of the annulus, but remains contained within the annulus or under the posterior longitudinal ligament, and there are no free nuclear fragments in the spinal canal. However, even with an intervertebral disc herniation, outward projections can compress the spinal cord or spinal nerve and cause sciatica.

  If the intervertebral disc expands circumferentially outward in all directions, not just at one location, another disc failure occurs. This occurs when the intervertebral disc becomes weaker over time, expands outward and assumes a “roll” shape. The mechanical stiffness of the joint is reduced, the spinal motion segment can become unstable and the spinal cord segment can be shortened. When the intervertebral disc “roll” extends beyond the normal circumference, the disc height can be impaired, and the nerve holes with the nerve roots are compressed, causing pain. Other current procedures other than spinal fusion for symptomatic disc rolls and disc herniation include “laminectomy”, which involves surgical exposure of the annulus and surgical removal of the symptomatic portion of the prolapsed disc Followed by a relatively long recovery period. In addition, osteophytes can be formed on the outer surface of the disc roll to further invade the spinal canal and nerve tunnels through which the nerves pass. The cranial vertebra can eventually settle on top of the caudal vertebra. This condition is called “lumbar spondylosis”.

  Various other surgical procedures that simply hold the spinal disc and simply try to relieve pain include removing some or most of the inner core, thereby reducing and reducing the outward pressure on the annulus. Includes “discectomy” or “disc decompression”. In a minimally invasive microsurgical procedure known as "microlumbar discectomy" and "automatic percutaneous lumbar discectomy", the nucleus is removed by aspiration through a needle that extends laterally through the annulus. . These procedures are less invasive than incisions, but suffer from the potential for instability due to damage to the nerve roots and dural sac, perineural scarring, surgical site rehernia formation and excessive bone removal. In addition, these procedures typically involve ring drilling.

  Injured discs and vertebral bodies can be identified by current diagnostic images, but existing surgical interventions and clinical outcomes are not always good. Furthermore, patients undergoing such fusion surgery experience serious complications and uncomfortable and long-term recovery. Surgical complications include, for example, disc space infection; nerve root injury; hematoma formation; instability of adjacent vertebrae and destruction of muscles, tendons and ligaments.

  Several companies continue to develop prostheses for the human spine with the goal of completely replacing the physiological disc, ie, an artificial disc. In patients whose degree of degeneration has not progressed to annulus destruction, instead of total disc replacement, the preferred treatment option may be to replace or augment the nucleus pulposus including placement of the prosthetic disc nucleus. As described above, the normal nucleus is contained in a gap surrounded by the upper and lower bony vertebrae and the annulus fibrosus surrounding them. In this way, the nucleus is completely enclosed and encapsulated, and the only transmission to the body is fluid exchange that occurs through the bone interface with the vertebra, known as the endplate.

  Hygroscopic substances, including physiological nuclei, have an affinity for water (volume swells), which distracts (ie, increases) the disc space, regardless of significant physiological loads applied across the disc in normal activity. Or “expand”)). These forces range from about 0.4 times to about 1.8 times the body weight, producing local pressures that are well above normal blood pressure, and the nucleus and annular internal tissue are actually effectively avascular.

The presence of the nucleus as a cushion (eg, the nucleus is “air” if the spinal disc is a “tire”) and the annulus as a flexible element is involved in a series of movements in the normal disc. The series of movements is described in terms of degrees of freedom (ie, translation relative to a reference point and rotation around three orthogonal planes, instantaneous center of rotation around the longitudinal axis of the spine). The axial spinal implant assembly of the present invention in maintaining, restoring and / or managing motility in terms of flexion, extension, compression, left / right (L / R) rotation, L / R lateral bending and distraction. The advantages of will be more apparent from an explanation of the relationship between spinal motion and anatomy and the consequences and effects of the following injuries (eg trauma / mechanical injury or aging).
(Bending and stretching)
Spine flexion and extension combines anterior sliding and rotation of the vertebrae. The facet joints and rings resist forward sliding. The rotation is resisted by the wheel; the facet joint capsule; the action of the back muscles and the passive tension produced by the thoracolumbar fascia. Extension is resisted by the facet joint and, secondarily, the annulus.

  Because the combination of facet joints and discs is inherently stable in this aspect, the spine is resistant to injury if the force is purely flexed. Although the spinous muscles are important in controlling this movement during strong flexion, they can be damaged, but subsequent pain is usually not chronic.

Elongation is inhibited by the fixation of the lower joint process to the facet joint and ultimately to the lamina. This can result in cartilage damage to the facet joint; tearing of the facet joint capsule and fractures of the facet joint or facet joint.
(compression)
Spinal compression is due to weight and the load applied to the spine. Body weight is a small compression load. The main compressive load on the spine is generated by the back muscles. When a person bends forward, it is necessary to balance the body weight + external load by the force generated by the back muscles. That is, the muscle load balances the gravity load, so the spine is in an equilibrium state and prevents the person from falling down. The external force is calculated by multiplying the load by the vertical distance of the load from the spine. The greater the distance from the spine, the greater the load. Since the spine acts close to the spine, it is necessary to apply a large force to balance the load. The force generated by the back muscles compresses the spinal structure.

  Most compressive loads (-80%) are supported by the anterior column (disc and vertebral body). The intervertebral disc is a static pressure system. The nucleus acts as a confinement fluid in the ring. The nucleus converts compression (axial load) in the vertebral endplate to tension in the annulus fibrosus.

Compression damage is mainly caused by two mechanisms; axial loading or muscular action due to gravity. Gravity damage is due to sticking the hips, while muscle damage is due to severe movement during pulling or lifting. The serious outcome of the injury is destruction of the vertebral endplate. Because endplates are nutritionally important to the disc, damage can alter the biochemistry and metabolic state of the disc. If the endplate heals, the disc will not be harmed. However, if the endplate does not heal, the nucleus can undergo harmful changes. The nucleus loses its proteoglycan and thus its water retention capacity. The static pressure characteristics of the nucleus are impaired. Rather than sharing the load between the nucleus and the wheel, more load is transmitted to the wheel. And the annulus is destroyed. In addition to ring tearing, the layers of the ring separate (separate). The intervertebral disc can collapse or maintain its height with progressive ring rupture. If the annulus becomes significantly weakened, the intervertebral disc may break, causing nuclear material to move to the annulus or spinal canal, causing nerve root compression.
(rotation)
Spinal rotation is achieved by contraction of the abdominal muscles acting through the thorax and thoracolumbar fascia. There are no major muscles involved in lumbar rotation. Annulus intervertebral joints and collagen fibers resist this rotation. During rotation, only 50% of the collagen fibers are always in tension, which makes the ring susceptible to damage.

The spine is particularly susceptible to damage in a combination of rotational and bending loads. Bending applies compressive stress to the annulus. As the spine rotates, compression occurs at the facet joint surface of the joint opposite to the rotation. Distraction occurs at the facet joint on the same side of rotation. The center of rotation of the motion segment moves from the back of the intervertebral disc to the compressed facet joint. The intervertebral disc moves laterally and the shear force on the annulus fibrosus is significant. The annulus is fragile in this direction and can tear. If rotation continues, the facet joint can maintain cartilage damage, rupture and rupture, but the annulus can rupture in several different ways. Any of these injuries can be a source of pain.
(Lateral bending)
Bending is a combination of lateral bending and rotation through the annulus and facet joint.
(Distraction)
Pure distraction rarely occurs and is usually a combination of tension and compression at the spinal joint depending on the direction of the applied force. An example of distraction force is therapeutic spinal traction to “unload” the spine.

  In the context of the present invention, as used herein, the term distraction refers to the elevation in height that increases the disc space, which formally results from the introduction of a motion retention assembly or a prosthetic nucleus device (“PND”). This can be accomplished with the device axially positioned during implantation or assisted by a temporary distraction rod. Temporary distraction refers to an increase in intervertebral disc height by means such as a distraction rod, which is later removed, but the increase is maintained during the operation while the patient is in a prone position. Thus, the device is inserted into the elevated disc space initially formed by other distraction means, after which the physical presence and stericity of the inserted device is key to maintaining its height gap and decompressing the disc And relieve pain caused by nerve contact.

  Thus, taking a reference point on the upper surface of the vertebral body, the motion segment including the vertebral body, the next most cranial vertebral body and the intervertebral disc between the two vertebral bodies has six degrees of freedom. If the x-axis is oriented in the anterior / posterior direction, the y-axis is oriented in the right / and left side, and the z-axis is oriented in the caudal / cranial direction, the six degrees of freedom are:

今日まで、現在企図され、或いは配置されている人工髄核デバイスの欠点には、沈降（ｓｕｂｓｉｄｅｎｃｅ）；その突出又は移動する傾向；骨を侵食する傾向；経時的に劣化する傾向或いは生体力学的荷重の分散及び支持を付与しない傾向が含まれる。これらの欠点の一部は、通常、その配置が、患者のからだを横方向に貫通して椎間板部位に導入されるとともに、椎間板及び隣接する皮質骨を切除し、或いは椎間板及び隣接する皮質骨を貫通する横方向の孔を開けるように操作される器具によって達成されるほぼ完全な椎間板切除を伴うという事実に関連する。椎体の終板は非常に硬い皮質骨を含み、椎体に必要な強度を与える役割を果たし、通常、孔開け中に脆弱化し、或いは破壊される。椎体終板は各椎骨の頂部及び底部を取り囲む特別な軟骨構造体であり、椎間板と直接接触している。椎体終板は椎間板への栄養素及び水の通過を可能にするため、椎間板の栄養に重要である。これらの構造体が損傷すると、椎間板の劣化及び椎間板機能の変化が生じ得る。横方向に開けられた大きな１つの孔又は複数の孔は椎体の統合性を損なうのみならず、過度に後方に孔開けされた場合、脊髄が損傷し得る。

To date, artificial nucleus pulposus devices currently contemplated or deployed have the following disadvantages: subsidence; tendency to protrude or move; tendency to erode bone; tendency to degrade over time or biomechanical load And a tendency to impart no support and support. Some of these shortcomings are usually introduced laterally through the patient's body and into the disc site, and the disc and adjacent cortical bone are removed or the disc and adjacent cortical bone are removed. Related to the fact that it involves an almost complete discectomy achieved by an instrument that is manipulated to pierce a transverse hole therethrough. The end plate of the vertebral body contains very hard cortical bone and serves to give the vertebral body the necessary strength and is usually weakened or broken during drilling. The vertebral endplate is a special cartilage structure that surrounds the top and bottom of each vertebra and is in direct contact with the intervertebral disc. Vertebral endplates are important for disc nutrition because they allow the passage of nutrients and water to the disc. Damage to these structures can result in disc degradation and changes in disc function. A large hole or holes drilled laterally not only compromises the integrity of the vertebral body, but can also damage the spinal cord if drilled excessively posteriorly.

  Alternatively, current devices may be surgically created in the annulus or placed through an enlarged hole. The annulus fibrosus consists of strong and thick collagen fibers. Collagen fibers including the annulus are arranged in alternating concentric layers. The intra-layer orientation of these fibers is parallel, but the collagen fibers in each alternating (ie, interlayer) layer are oriented diagonally (˜120 degrees). This oblique orientation allows the wheel to resist forces in the vertical and horizontal directions. Axial compression of the disc results in an increase in pressure in the disc space. This pressure is transmitted to the wheel in the form of a load (stress) perpendicular to the wall of the wheel. When stress is applied, these fiber layers become in tension and the horizontal angle shrinks and resists the load better, ie, the ring transmits their load to the outer circumference of the ring (hoop stress), thereby causing their vertical Works to resist stress. The normal tensile force resists bending and distraction (bending and stretching). The horizontal tensile force resists rotation and sliding (ie, twisting). The vertical component of the annulus layer allows the intervertebral disc to withstand anterior and posterior bending sufficiently, but only half the horizontal fibers of the annulus involved during rotational movement. In general, the intervertebral disc is more susceptible to damage during torsional movement and gains its primary protection from the posterior facet joint during rotation, but this risk is further increased when the annulus is damaged.

  In addition, the disruption of the annulus remains post-operatively, impairing the physiological biomechanics of the disc structure and providing a path for device protrusion and movement. Other devices that attempt to provide sufficient mechanical integrity to withstand the stresses they receive are constructed to be very tough, stiff and inflexible, thus corroding bone or vertebrae over time. There is a tendency to be embedded in the body and this phenomenon is known as “sedimentation” and is sometimes referred to as “telescoping”. The result of sedimentation is a reduction in the effective length of the spine, which can subsequently cause damage to the nerve root and the nerve that passes between the two adjacent vertebrae.

  The present invention has been made in view of the above-mentioned concerns.

  Functions in conjunction with one or more elastic (eg, semi-flexible; compressible) or spring members (including non-helical springs such as relatively thin Belleville disc springs) and with respect to the longitudinal axis of the spine A spinal motion retention assembly is disclosed that is configured to include a plurality of pivots that are particularly effective for retaining motion in any plane.

  In the context of the present invention, a “plane” is defined relative to the orthogonal axes x, y, z, where z is the longitudinal axis of the spine. More specifically, rotation around x, y, z and movement around x, y are made possible by a plurality of pivot points, and the elastic member allows movement in the z direction, Functions to suppress directional compression.

  As used herein, the term unconstrained refers to the fact that the pivot is not fixed and refers to motion that exceeds the normal range of motion in all six degrees of freedom. Thus, for the lumbar spine, the normal maximum range of motion is usually about 12 ° flexion, about 8 ° extension, about 9 ° left or right lateral bending and about 2 ° clockwise or counterclockwise motion. A motion retaining assembly according to a preferred embodiment of the present invention (e.g., having an unconstrained dual pivot in conjunction with an elastic member) that is generally configured for the lumbar spine is at least about 4 °, and often at least about 8 , Preferably about 20 ° bend (forward bending), and at least about 4 °, often at least about 6 °, preferably about 20 ° extension (backward bend). The rotation is completely unconstrained and there is no limit. With respect to the spine, generally the MPA according to the present invention often provides at least about 100 or 125% of the normal maximum range of motion for any particular motion segment being treated.

  While it is known in the art to implant certain other human joints (eg, fingers and knees) using a device intended to maintain translation, as noted above, the spine is Is the only human joint with 6 degrees of freedom. Unlike current devices (e.g., Medtronic (R) Maverick (TM) devices or SpineCore Flexicore (TM) discs), the spinal implant assembly of the present invention retains motion (including translation) in all six degrees of freedom. It is possible. The reason is that these assemblies are preferably coupled with an elastic member or an elastically deformable member so that the movement (translation) of the natural structure supporting the physiological load is not obstructed in any plane. This is because it is configured with a pivot point and an arrangement oriented substantially at the main compressive stress line, that is, an arrangement at the center of rotation with respect to the human disc motion segment.

  Generally, after partial or complete nucleotomy, the assembly is axially inserted into the spine, through a cannula secured to the sacrum, and beyond the treatment area to the surgically enucleated disc space. Can be inserted. In one aspect of the invention, the artificial or augmentation material is introduced through at least one vertebral body or into at least one intervertebral disc space. The introduction of the spinal MPA of the present invention is performed without the need to surgically create a hole in the annulus of the intervertebral disc, or to detractably expand the existing hole, and to place the physiological function of the intervertebral disc structure therapeutically. Is done.

  In one aspect of the present invention, the risks associated with implant escape, migration or sedimentation (essentially less with the MPA of the present invention) engage the vertebral body and secure (ie, anchor) the implant assembly therein. It can be further mitigated by external holding means, for example self-tapping male threads configured to distribute stress evenly over a large surface area.

  Typically, the screw is a “cancellous” bone screw known in the art. Typically, the screw is cut to a substantially flat surface at the thread, with the flattest portion of the surface oriented in the direction of the applied load. In one embodiment, the generally thread form includes a deep thread with an asymmetric thread form, which provides the benefits of improved weight support and load distribution. The thread is formed at the root and extends as a continuous thread from the rear end to the front end of each thread. The thread includes a plurality of rotating portions spaced along the root by gaps between the threads. Because the threads on the proximal and distal components are similar twists (ie, the threads rotate in the same direction), both threads are clockwise or both are counterclockwise.

  Self-tapping screws may or may not be configured to assist distraction of adjacent vertebral bodies in the motion segment, i.e., distal and proximal components (each superior The vertebral body, which may or may not be anchored to the inferior vertebral body, where the distal anchor has a smaller outer diameter than the proximal anchor. The clockwise rotation of the embodiment configured with clockwise threads (ie, different pitches and outer diameters as described above) advances the assembly axially and moves the upper and lower vertebral bodies in the motion segment relative to each other. Distract.

  In the context of the present invention, “dynamic” refers to enabling mobility by assisting or promoting force or load bearing ability to assist, or substitute for damaged, weakened, or absent physiological structures. Refers to a non-static device that has the inherent ability to The motility retention assembly (MPA) of the present invention provides pain from symptomatic discs ranging from the treatment of patients with little apparent degeneration or collapse on radiographs to patients for whom a prosthetic nucleus device or total disc replacement is indicated. Provides dynamic stabilization (DS) of ongoing therapeutic interventions to treat For example, artificial nucleus pulposus (PN) may be indicated in patients who have a high degree of degeneration and loss of intervertebral disc height but do not reach a stage where advanced annulus destruction exists. The prosthetic nucleus can exceed the scope of dynamic stabilization by including invasive nucleotomy and subsequent filling of the enucleation gap with a suitable material. The purpose in this case is to restore disc height and movement. In general, total disc replacement (TDR) is a more advanced disease than in the case of an artificial nucleus pulposus, but is indicated when some ring functions remain. The motion retention assembly of the present invention is much less invasive (in terms of placement) than conventional total disc replacement, and enhances, retains, restores, and manages or enhances physiology according to the indicated intervention, It functions as an artificial disc replacement (PDR) that is configured to be retained, recovered, or managed. In general, the inventive axial motion retention assembly disclosed herein is preferably configured as a device having an aspect ratio greater than 1, ie, the device dimensions at the vertebral axis are close to the physiological instantaneous center of axial rotation. Larger than the device dimension in any orthogonal direction to the axis, and positioned in an orientation substantially along the main compressive stress line and positioned approximately at the center of rotation relative to the human disc motion segment.

(Axial transsacral access)
The present invention contemplates the use of axial transsacral access to the lumbosacral spine. The axial transsacral access method shown in FIG. 2 stabilizes, moves and retains the treatment during the intervention, and eliminates the need for other invasive procedures associated with myotomy and conventional spine surgery. Allows the design and placement of new and improved instruments and therapeutic interventions, including systems.

  FIG. 2 shows an introductory overview of the process, while FIGS. 2A and 2B monitor a fluoroscope (not shown) and “slowly advance” the rounded tip stylet 204 over the front of the sacrum 116, 116 shows the process of reaching 116 desired positions. In this process, the rectum 208 is moved aside, so a straight path is established for subsequent steps. FIG. 2C shows a representative axial transsacral channel 212 constructed in the L4 vertebra 220 through the sacrum 116, L5 / sacral disc space, L5 vertebra 216, L4 / L5 disc space. If treatment is not performed on the L4 / L5 motion segment, the channel may terminate at L5 rather than extending to L4.

  The discussion of FIG. 2 is presented to provide a background to the present invention. Applicants' earlier applications (partially registered as US patents) describe another access method that is a posterior transsacral axial spine approach rather than an anterior transsacral axial spine approach (eg, U.S. Pat. No. 6,558,386, “Axial Spinal Implant and Method for Implanting an Axial Spinal Implant in Imprint” Vertebrae of the Spine), which describes the anterior transsacral axial approach shown in Figure 2, and the contents disclosed therein are also disclosed herein. And those were). The teachings of the present invention can be used with axial transsacral channels.

  An overview of the method for accessing the spinal region and receiving treatment is useful to illustrate the background of the invention. As shown in FIG. 2A, a pre-sacral approach from a percutaneous anterior pathway toward the target site of the sacrum, through which a transsacral axial hole is drilled and the channel is extended distally, followed by multilevel axial orientation Proceed with spinal stabilization assembly. The anterior, pre-sacral, percutaneous route extends through the “pre-sacral space” and forward of the sacrum. The pre-sacral, percutaneous route is preferably used to introduce and access the instrument (eg, distal / cranial direction through one or more lumbar vertebral bodies and intervertebral discs). By opening). “Percutaneous” in this context means simply reaching a posterior or anterior target point through the skin, such as transcutaneous or transdermal, and does not imply a specific treatment from other medical fields. Absent. However, unlike percutaneous access, percutaneous openings are desirably minimized and are less than 4 cm in diameter, preferably less than 2 cm, and sometimes less than 1 cm in diameter. In general, the percutaneous route is at least one sacral body and one or more in the cranial direction from the respective posterior or anterior target point, as visualized by fluoroscopy or fluoroscopy devices. Axially aligned with a hole extending through the lumbar vertebral body. More specifically, as shown in FIG. 2b, the lumbar vertebra is accessed through a small skin opening adjacent to the tip of the coccyx. A standard percutaneous approach is used to enter the pre-sacral space and an introducer assembly with the blunt end of the stylet functioning as a dilator is placed through the lateral coccyx entry site. As the stylet tip passes through the face layer, the blunt end is rotated relative to the front surface of the sacrum and “slowly advanced” to the desired position of the sacrum under fluoroscopy. When the target site is accessed and the risk of soft tissue damage is reduced, the blunt stylet is removed and a guide pin or wire is safely introduced through the guide pin introducer tube and “tapped in”. The guide pin establishes a path for subsequent bone dilator and sheath placement through which a twist drill is introduced to form an axial bore, the lumen of which is expanded distally. The guide pins maintain an axial arrangement of larger diameter access and preparation tools and an array of cannulated spinal stabilization devices and assemblies, which are subsequently 23 inches long and 0.090 inches long. It is introduced over a guide pin with a diameter of (about 2.28 mm) and through an exchange cannula for placement in the spinal column. In this regard, all of the same assignee's US patent applications 10 / 972,065, 10 / 971,779; 10 / 971,781; No. 971,731; 10 / 972,077; 10 / 971,765; 10 / 971,775; 10 / 972,299; and 10 / 971,780, and 2005 8 As described at least in part in US Patent Application No. 60 / 706,704, filed on the 9th of the month, by the same assignee, and the contents disclosed in these patent documents are also disclosed in the present application. To do.

(Example)
In order to disclose selected exemplary embodiments, the present invention will be described in more detail with reference to the accompanying drawings. However, the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and as part of an effort to convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

  In order to avoid the impression that can arise in a patent application when considering many different alternative configurations at once, reference is made to FIG. 3, which shows one very specific embodiment of the present invention. In order to show schematically the components and their placement relative to the spinal motion segment, an overview of the implanted device will be given. Subsequent drawings detail the delivery and assembly of the device.

FIG. 3 shows an implanted motion retention assembly 300. FIG. 4 is an exploded view showing another view of the components described in FIG.
The motion retention assembly 300 is implanted in the distal vertebral body 304 and the proximal vertebral body 308 and extends across the disc space 312. The motion retaining assembly 300 can be placed in a pre-formed axial channel 212. Collectively, the distal vertebral body 304, the proximal vertebral body 308, and the disc space 312 form a motion segment 316. The vertebral body drawings are not intended to convey anatomical details of the spinal components, but to illustrate the placement of the assembly motion holding assembly 300. One mapping of the components shown in FIG. 3 to the spine is such that the distal vertebral body is the L5 vertebral body 216 (see FIG. 2) at the caudal end of the lumbar vertebra 112 (see FIG. 1). The distal vertebral body 308 can be the sacrum 116 (see FIG. 1). Alternatively, the motion segment can be more cranial (and thus more distal to the surgeon), such as the L4 / L5 vertebral bodies 220, 216 (see FIG. 2).

  The major components of the motion retention assembly 300 are the distal component (fixed to the upper or distal vertebral body, sometimes referred to herein as the distal bone anchor) 340, the proximal component (lower) Or 344, anchored to the proximal vertebral body (sometimes referred to herein as a proximal bone anchor) 344, an artificial nucleus pulposus 348 (generally including the outer membrane 460), and a pivot 352.

  The distal bone anchor 340 shown in FIG. 3 has a set of external threads 356. Alternatively, the set of male threads 356 may include a tip breaker portion 360 at the distal end of the distal bone anchor to facilitate initiating thread path cuts into the distal vertebral body 304. The chip breaker portion is clearly shown in FIG. The chip breaker is a discontinuity in the thread and allows the chip to peel off when the thread path is cut. An axial channel 212 is formed in the distal vertebral body 304, and the diameter of the axial channel 212 in the distal vertebral body 304 is approximately equal to the small diameter of the set of external threads 356.

  The distal bone anchor 340 has a cavity 364 that extends from the distal surface 366 of the distal bone anchor 340 to the proximal surface 370 of the distal bone anchor 340. In this connection, the surface is the three-dimensional surface of the part as viewed from the side and is similar to the six three-dimensional surfaces of one dice from a pair of dice. The cavity 364 is not a uniform cross section and serves multiple purposes. The distal end of the cavity 364 indicates that the cavity can be used to allow the distal bone anchor 340 to be placed on the guidewire. The cavity 364 includes an internal thread portion 368 that can be engaged with a driver, a holding or removing tool described below. The cavity 364 in the distal bone anchor 340 shown in FIG. 3 has a distal pivot cup 372 at the corresponding cup portion 376 of the cavity 364.

The distal pivot cup 372 then has a cavity 380 that functions as a support surface for the distal end 384 of the pivot 352.
The pivot 352 shown in FIG. 3 has the distal end 384 and the proximal end 388 configured in this embodiment as substantially spherical components that are integral with the pivot body 392.

  Proximal bone anchor 344 has a set of external threads 404 that include an introducer 408. The proximal bone anchor 344 has a cavity 412 that extends from the distal surface 410 of the proximal bone anchor 344 to the proximal surface 414 of the proximal bone anchor 344. The cavity 412 is not uniform in cross section. A portion of the cavity 412 has a set of internal threads 416. The pitch of the set of female threads 416 is preferably relatively fine (possibly 16 threads per inch, up to 64 threads per inch). . In the embodiment shown in FIG. 3, the proximal bone anchor cavity 412 includes a proximal pivot cup 420 having a set of internal threads 424 that engage a set of internal threads 416 and includes a driver ( Torque from (not shown) rotates the proximal pivot cup 420 relative to the proximal bone anchor 344 and advances the proximal pivot cup 420 in the axial direction (distal). As the proximal pivot cup 420 is advanced axially, the proximal pivot cup 420 contacts the pivot 352 and the pivot 352 contacts the distal pivot cup 372. Once these components are in contact, further proximal advancement of the proximal pivot cup 420 causes the distal bone anchor 340 to the proximal bone anchor 344 (and the proximal vertebral body 308 engaged with the proximal bone anchor 344). An axial movement of (and the distal vertebral body 304 engaged with the distal bone anchor 340) occurs. This movement of one vertebral body away from another vertebral body results in distraction of the disc space between the two vertebral bodies.

  The distraction achievable by rotation of the proximal pivot cup 420 is preferably used as one adjustment to change the load distribution between the pivot of the motion retention assembly and the prosthetic nucleus component. The primary means of achieving distraction is by the distraction and insertion tool 2032 in FIG.

  Returning to FIG. 3, the driver engagement portion 428 may be configured to apply torque by the driver, among many types of manners. A female hexagon socket is a preferred choice. The proximal pivot cup 420 shown in FIG. 3 includes a threaded cavity 432 that is engageable with a driver or removal tool. The proximal pivot cup 420 includes a distal cavity 436 that functions as a support surface for the proximal end 388 of the pivot 352.

  The cavity 412 in the proximal bone anchor 344 also includes a jam nut 440 having a distal end 442 and a proximal end 446. The jam nut 440 has a set of external threads 444 adapted to engage with a set of internal threads. The jam nut 440 also has a driver engagement portion 448 configured to receive torque applied to a corresponding driver, such as a male hex driver. The torque input advances the jam nut 440 in the axial direction (distal) and contacts the proximal pivot cup 420. The jam nut 440 shown in FIG. 3 also includes a threaded cavity 452 that can be used by a driver or removal tool.

  The artificial nucleus pulposus 348 includes an outer membrane 460 and an artificial nucleus pulposus material 464. Because the outer membrane 460 is filled with artificial nucleus pulposus material 464, the outer membrane 460 expands to lower the lower endplate of the distal vertebral body 304, the upper endplate of the proximal vertebral body 308, and the annulus fibrosis (not shown). Conformably in contact with the inner wall and collectively define the disc space boundary.

  FIG. 4 shows the various components prior to insertion into the body, showing the outer membrane 460 before being expanded by the prosthetic nucleus material 464 to form the prosthetic nucleus 348 within the disc space. FIG. 4 also illustrates the mechanism by which the outer membrane 460 is sufficiently attached to the distal bone anchor 340 and proximal bone anchor 344 to stretch the membrane and fill the disc space without being pulled away from the bone anchor. A pair of retaining rings 484 used as part are shown. The mounting of the retaining ring 484 can be performed in a number of ways, including the use of adhesives, laser welding, crimping or drawing. The ring may be spring loaded or shrinkable (eg, nitinol or heat shrinkable polymer). In a preferred mounting method, the outer periphery of the retaining ring 484 is welded to the bone anchors 340 and 344 using a laser welding method. When the retaining ring 484 is welded, it is useful to compress the retaining ring 484 by laser welding, so that the ring is reduced and is more effective to hold the outer membrane 460 in place. . Laser welding can apply energy at the exact location so that the welding is done without transferring a large amount of heat to the assembly that can adversely affect the membrane.

  FIGS. 5 and 6 show further views of the motion holding assembly 300. In FIG. 5, the quarter circle is removed from the distal bone anchor 340 and the proximal bone anchor 344, showing the components in the assembled set of components (but no prosthetic nucleus material 464 is inserted. This device is Because it is not transplanted into the motor segment). FIG. 6 shows the same motion retaining assembly 300 but with the entire assembly's quarter circle removed.

  FIG. 7 shows an enlarged portion of FIG. FIG. 7 shows details of one method of coupling the outer membrane 460 to the distal bone anchor 340 and the proximal bone anchor 344. In a preferred embodiment, the outer membrane 460 is configured as an expandable membrane, preferably made of an elastic material such as silicone rubber, such as that obtained from Nusil Silicone Technology, Inc., located in Carpeneria, California. Exhibit an elongation of about 500% to about 1500%, most preferably about 1000%, and have a wall thickness of 0.220 inches (about 5.58 mm). Outer membrane 460 has a distal end 508 that fits into groove 516 at the proximal end of distal bone anchor 340 and a proximal end 504 that fits into groove 512 at the distal end of proximal bone anchor 344. After the retaining ring 484 is placed on the epicardial ends 504, 508 and along the respective perimeter to the bone anchors 340, 344 (preferably while compressing the retaining ring 484 so that the ring is smaller). The adventitia 460 is tightly coupled to the two bone anchors, so that the adventitia 460 extends significantly without being pulled away from the bone anchors 340 or 344, and the pressure from the inserted prosthetic nucleus material 464 causes the disc space to be Fulfill.

  Returning to FIG. 3, the bulk prosthetic nucleus material (PNN) (element 464 in FIG. 3) is an elastic solid and viscoelastic gel, or an elastic solid or viscoelastic gel, ie its viscoelastic properties (eg rheology and It is preferred to include a material that allows it to function in a functional manner substantially equivalent to a physiological disc nucleus, either alone or with the biomechanical properties of the expandable outer membrane 460. Preferred artificial nucleus pulposus materials and systems are biomedical silicone elastomers (eg, silicone rubber) such as those sold by Nusil Silicone Technology, Inc., Carpeneria, Calif., Or hydrogels or blends thereof (eg, Hydrogel / hydrogel or hydrogel / elastomer). Cross-linked hyaluronic acid, such as that commercially available from the Italian company Fidia, is an example of a suitable material, but many natural and artificial hydrogels or blends thereof can be configured to obtain similar properties without inflammatory reactions. For example, the above-mentioned U.S. patent applications, and in particular, U.S. Patent Application No. 60 / 599,989 filed on Aug. 9, 2004 and No. 60 / 558,069 filed on Mar. 31, 2004. Disclosed and described in

  FIG. 4 of timely delivery shows a view of slot 488 in cavity (364) of distal bone anchor 340 and slot 492 in cavity 412 of proximal bone anchor 344. The use of these two slots allows for adapted delivery of the two components. The adapted (or timely) delivery of the two bone anchors 340 and 344 allows control over the rotational position of the two sets of threads. The purpose of this controlled delivery is to avoid thread crossing. More specifically, when selecting to use the same thread pitch for male thread 356 on distal bone anchor 340 and male thread 404 on proximal bone anchor 344, distal bone anchor 340 is proximal bone anchor 344. Can be formed with a cross section (rod diameter) of the same size. Having a large cross-section is desirable because it makes it easier to design a distal bone anchor with adequate strength and maximum engagement of the thread and bone of the distal vertebral body.

If the small and large diameters of the threads of the distal bone anchor 340 and the proximal bone anchor 344 are the same, the proximal vertebral body 308 and the distal vertebral body 304 formed during the process of forming the axial channel 212 are penetrated. The holes to be made have the same dimensions. As the distal bone anchor 340 is moved in the direction of the hole in the distal vertebral body 304, the distal bone anchor 340 is first advanced axially by rotating through the hole in the proximal vertebral body 308. As the distal bone anchor 340 is rotatably advanced through the proximal vertebral body 308, the male screw 356 cuts a helical thread path through the bone around the hole in the proximal vertebral body 308. The hole is substantially the same as the small diameter dimension of the male screw 356, and the large diameter of the male screw 356 extends into the bone beyond the hole. Without timely or adapted delivery, subsequent axial advancement of the proximal bone anchor 344 tends to cut a new helix into the bone around the hole in the proximal vertebral body 308. Because the bone has just undergone a newly cut thread helix, this second helix experiences additional resistance and the bond strength between the male threads 404 on the proximal bone anchor 344 is cut through the bone earlier. Damaged by screw paths that are not currently used. In contrast, timely delivery allows the leading edge of the spiral thread outside the proximal bone anchor 344 to enter the spiral thread path left by the external thread 356 on the distal bone anchor 340. An alternative to timely delivery is to dimension the large diameter of the male screw on the distal bone anchor to be smaller than the diameter of the hole in the proximal vertebral body, and then Forming a hole in the distal vertebral body that is approximately the same.
(Extension of motion segments through the use of different thread pitches)
Previous patent applications assigned to the present applicant describe a method of imposing a distraction on a motion segment (two vertebral bodies are pulled apart from each other along the z-axis). See, for example, US Pat. No. 6,921,403, “Method and Apparatus for Spinal Distraction and Fusion”. Thus, the thread rod with the first finer thread pitch distal thread engages the distal vertebral body (the bore in the proximal vertebra is larger than the larger diameter of the thread in the distal thread). When the proximal coarser thread on the same threaded rod engages the proximal vertebral body, the rotation of the two threads with different thread pitches is finer at the distal end. A smooth pitch thread is advanced to the distal vertebral body slower than the coarser thread is advanced to the proximal vertebral body. The net effect is that the engagement of the two screw threads with the two vertebral bodies separates the two vertebral bodies.

This same method uses a bone anchor for the present invention to a single driver that can maintain a predetermined spatial separation between non-adjacent bone anchors and impose the same rotation on each bone anchor. When placed, it can be used to impose axial distraction. This type of driver is described in U.S. Application No. 60 / 621,730, filed Oct. 25, 2005, “Multi-Part Assembly for Introducing Implants into the Theatre. Spine) ”, and the contents disclosed in the patent document are also disclosed in the present application.
(Another means to impose distractions)
Although different thread pitches may be imposed as described above, other preferred distraction means may be used with the tool described below in connection with FIG. 20 to advance the distal pivot cup, which tool Axially advanced by engagement with the internal thread at the proximal bone anchor.
(Degree of freedom and constraints)
3-7 are shown stationary and the desired attribute of the motion holding assembly is dynamic stabilization, detailing how the motion segment moves with the implanted motion holding device. That is reasonable.

  A pivot point 480 located just above the thread cavity 432 in the proximal pivot cup allows the distal bone anchor 340 and the corresponding distal vertebra 304 to move relative to the pivot point 480 in a number of ways. Can exercise. The first type of motion is axial rotation (clockwise or counterclockwise). None of this particular motion holding device constrains the amount of clockwise or counterclockwise motion. As noted above, a system that allows approximately 2 ° rotation in this axis will support a normal range of motion in this axis (Note: the range and degree of motion will vary depending on the vertebral body level—eg, L4 -L5 is not the same as L5-S1).

  To avoid constraining the normal range of motion, the normal maximum range of motion usually allows about 12 ° flexion, about 8 ° extension, and about 9 ° left or right lateral bending. The exercise-holding device to be used will need to allow at least these amounts of exercise. The exact range and degree of motion relative to the motion segment varies along the motion segment of the spine. For example, the range and degree of motion in the L4-L5 motion segment is not exactly the same as the L5-S1 motion segment.

  The device shown in FIG. 3 is radially symmetric around the z-axis and need not be placed in a particular orientation to provide maximum rotational capability in a particular direction (eg, bending vs. stretching or lateral) Bending). The rotation of the implanted distal bone anchor relative to the proximal bone anchor is accomplished through a combination of the action of the proximal pivot head 388 moving relative to the proximal pivot cup 420 and the action of the distal pivot head 384 relative to the distal pivot cup 372. Can be broken.

  By changing two parameters, the depth of the cavity in the pivot cup and the width of the pivot body relative to the pivot cavity, the maximum pivot angle of the pivot relative to the corresponding pivot cup can be changed. 8A and 8B illustrate these concepts. FIG. 8A shows two different pivot body widths. If the pivot body is changed from width 608 to width 612, the wider pivot body 612 will impact the pivot end cup 604 after a smaller amount of rotation than if the pivot body is in the width 608 state.

  8B uses the pivot body portion of FIG. 8a, but is located in a pivot end cup 616 that is not too deep so that the pivot rotates relative to the pivot end cup in the case of FIG. 8B rather than in FIG. 8A. Can do.

  The use of two pivots allows translation of one implanted bone anchor relative to another anchor in the x-axis (anterior / posterior), y-axis (lateral), or a combination of the two. To understand the benefits of using two pivots, it is useful to look at the motion when there is one pivot. In FIG. 9A, a single pivot 650 engages a support surface at the proximal bone anchor 654 and is secured to the distal bone anchor 658. As shown in FIG. 9B, when the pivot 650 rotates away from the z-axis in the xz plane, the distal bone anchor 658 rotates with respect to the proximal bone anchor 654 and the other bone of one bone anchor Change the relative orientation with respect to the anchor.

  In contrast, in FIG. 9C, pivot 660 is a dual pivot and thus can pivot relative to proximal bone anchor 654 or distal bone anchor 668. Thus, the distal bone anchor 668 is capable of a substantially pure translation along the x axis with respect to the proximal bone anchor 654. The relative orientation of the bone anchor is retained because the movement did not impose rotation on the distal bone anchor 668. The term almost pure translation was used because the height of the distal bone anchor 668 changed slightly during the movement from the state shown in FIG. 9C to the state shown in FIG. 9D, which is a pure x-axis translation. It will not occur. Although this example shows a translation in the x-axis, the same kind of motion as shown in FIG. 9 occurs in the y-axis or a mixture of x and y components if the pivot is not constrained in any way. obtain.

  The embodiment shown in FIG. 3 does not provide significant ability for significant additional x or y translation because the pivot cup is approximately the same size as the pivot end located on the pivot cup. If the pivot cup is expanded so that it exceeds the maximum diameter of the pivot end sphere by 5 mm, some additional capability for translation is obtained. Doing this with both pivot cups adds the possibility of an additional amount of translation.

  The embodiment shown in FIG. 3 uses a radially symmetrical pivot end and a pivot cup cavity. Using an asymmetric cavity in the pivot cup may allow a larger amount of additional allowable translation in one direction compared to the other direction. FIG. 10 shows an example of this concept. Looking down on the half pivot 608, the maximum dimensions of the pivot body wall and pivot spherical head are shown. Also shown is a trajectory 620 that functions as a constrained region when the pivot 608 moves inward. Note that the additional translation in the x direction is extremely limited, but a much larger amount of additional translation is in the y (lateral) direction. If such an asymmetric trajectory is used, the insertion technique will need to control the orientation of the bone anchor so that the extension direction of the trajectory is aligned in the proper direction. One way is to insert the component in a specific orientation with respect to the driver. It is also possible for the driver to have a marker so that the driver marker is monitored and the components are placed in the proper orientation with respect to the forward / backward and lateral axes. The orientation of the pivot cup within the inserted hole anchor may be controlled by having the pivot and key anchor key and slot engagement.

  A way to allow further bending in one direction than in the other direction is to have an asymmetric pivot. FIG. 11 shows asymmetric pivot 624 in pivot cup 628 (only one end of the pivot is shown). This asymmetric pivot is more constrained by movement in the x direction (forward / backward) than in the y direction (lateral left / lateral right). If an asymmetric component is used, it is important that the asymmetric component be placed in the proper starting position during the installation procedure. The device supports unrestricted rotation along the z-axis, but the range of axial rotation for the individual motion segments is only about 2 ° clockwise and about 2 ° counterclockwise, so an asymmetric pivot arrangement Note that is relatively constant.

  To provide a sixth degree of freedom, translation in the z-axis, the motion retention assembly would need to allow the distal bone anchor to move in the z-axis relative to the proximal bone anchor (watch carefully) If so, the translation in the x or y axis achieved through the use of a dual pivot point will accidentally provide a change in the z axis, but this kind of translation is purely a force along the z axis. Note that it doesn't seem to give rise to Adding a degree of freedom to the z translation can theoretically be achieved by a device that stretches under tension. However, tensile loads that impart distraction to the motion segment are rare. The most common is to use therapeutic traction to stretch the spine.

  Thus, a more useful ability for translation in the z-axis is the ability to compress. Ideally, compression is reversible and iterative. Therefore, compression-derived deformation will need to be elastic. Elasticity is a property in which a solid object receives a force and changes its shape and dimensions, but when the force is removed, it recovers its original shape. For many, elastic deformation is reminiscent of a rubber ball that is deformable and restores its original shape. Air bags can undergo elastic deformation (examples include air tires and soccer ball air bags). Elastic deformation can be achieved through the use of springs including various types of disc springs, such as Belleville disc springs or similar springs.

  If an elastically deformable component is added to the motion holding assembly, this motion segment will contribute to the ability of the spine to compress under a strong compressive force such as landing after jumping or buttocks. Since the set of motion segments are stacked, the lack of the ability to elastically compress one motion segment is acceptable, as is acceptable for a person with a fusion motion segment. Although having some ability to elastically compress in the z-direction is considered particularly desirable for motion retention devices with artificial nucleus pulposus, they ideally mimic the behavior of natural motion segments Because of that.

  The elastic deformation of the motion-retaining device that allows the endplates of the distal and proximal vertebral bodies to approach each other provides a compressive force on the prosthetic nucleus that conforms to the endplates of these vertebral bodies. Apply. The compression of the prosthetic nucleus in the z direction expands it radially outward and maintains the total amount of the prosthetic nucleus. Because the prosthetic nucleus expands radially outward, it transmits forces to the various layers of the annulus, thus mimicking the natural transmission and dissipation of physiological loads.

Having an exercise-holding device that has the ability to undergo elastic deformation in the z-axis and the radial distribution of loads to the annulus and mimic normal physiological load sharing reduces the risk of sedimentation or transition syndrome Tend to.
(Introduction of elastically deformable components)
One option of using an elastically deformable component to support compressible axial parallel motion and load balancing capability is to provide an O between the distal end of the distal pivot cup 372 and the distal bone anchor 340. Place a ring, elastomeric washer or other elastomeric object. Ideally, the distal pivot cup or the distal bone anchor or both can be shaped to allow a void for the elastomeric material. Such elastomeric components can be constructed from semi-flexible materials such as fluoropolymer elastomers (Viton ™), polyurethane elastomers or silicone rubber.

  Another location that may be used for placement of the elastomeric component is within the proximal bone anchor between the proximal pivot cup and the jam nut (embodiment not shown). In this configuration, the proximal pivot cup will not have an external thread, so it moves freely in the axial direction in the cavity of the proximal bone anchor and between the proximal end of the proximal pivot cup and the distal face of the jam nut. Compress the elastomeric material. A further position for placement of the elastomeric surface is between the support surface and the pivot.

  FIG. 12 shows one motion retention assembly 800 having elastomeric components. More specifically, the motion retention assembly 800 has a pivot 804 that fits into a cavity in the distal pivot cup 808 that provides a support surface for the distal end of the pivot 804. The other end of the pivot 804 fits into a cavity in the proximal pivot cup 812 that also provides a support surface. The exterior of the distal pivot cup 808 and proximal pivot cup 812 is not threaded and the pivot cup can move longitudinally within the cavities at the distal bone anchor 816 and the proximal bone anchor 820. Distal O-ring 824 is disposed between the distal pivot cup 808 and the cavity wall in the distal bone anchor 816. Similarly, proximal O-ring 828 is disposed between proximal pivot cup 812 and thread cap 832 that engages a set of internal threads at the proximal end of the cavity at proximal bone anchor 820. The thread cap 832 has a slot 836 for receiving a similarly shaped driver for applying torque to the thread cap. With sufficient input to slot 836, the thread cap can be threaded cap 832, O-ring 828 (which also compresses), proximal pivot cup 812, pivot 804, distal pivot cup 808, distal O-ring 824 and It can be used to impart distraction to a motion segment having this motion retention device inserted by advancing the distal bone anchor 816 axially (distally). Since the axial movement of the thread cap 832 is related to the proximal bone anchor 820, the movement of all other components is responsible for the movement of the vertebral body engaged with the distal bone anchor 816 to the proximal bone anchor 820. Exercise the combined vertebral bodies.

  One skilled in the art will appreciate that the use of a single O-ring is a viable alternative to the use of two O-rings. When one skilled in the art uses two elastomeric inserts in a single motion holding assembly, the elastomeric inserts can have different properties, eg, made of different thicknesses or from different elastomeric materials, while It will be understood that will respond under a smaller axial load than the other.

  In view of appropriate modifications to the shape of the components within the motion retaining assembly, the O-ring can be replaced with other elastomeric components such as washers. The O-ring can also be replaced with screws of various configurations and stiffness that can tolerate elastic deformation without depending on the use of elastomeric components.

A coil spring is one option. Another option is one of various types of spring washer products such as Belleville disc springs. The spring washers can be stacked to give a greater total deflection or simply change the response curve of the deflection to the force.
(Processing spring)
FIG. 13 shows a cross-section of a pivot 900 having a first end 904, a second end 908, and a machined hollow rod 912 that joins the two ends. A spring machined into a hollow rod can be made with high accuracy (as opposed to a spring formed from coil stock), and variations between machined springs are reduced.

Another use of the processing spring is in a pivot cup that does not have an external thread, such as the pivot cup shown in FIG. A pivot cup having an integrated processing spring may have a first portion that houses one end of the pivot and functions as a support surface. The other part of the pivot cup may include a cylindrical part that can be machined to incorporate a machining spring.
(Other embodiments)
FIG. 14 illustrates another embodiment of the motion retaining assembly 300. Distal bone anchor 740 and proximal bone anchor 744 are shown with pivot 352, but without outer membrane 460 (see FIG. 7). The groove 512 at the distal end of the proximal bone anchor and the groove 516 at the proximal end of the distal bone anchor can be seen from this view. The main difference between this motion retention assembly 700 and motion retention assembly 300 is that the distal pivot cup 772 has a male thread 776 and is threaded into a corresponding set of female threads 780 in the cavity of the distal bone anchor 740. The artificial nucleus pulposus material 464 is introduced directly into the disc space rather than filling the outer membrane and is described in US patent application Ser. No. 11 / 199,541 filed Aug. 8, 2005. And with or without the process of sealing the surface of the disc space by means and methods as briefly described below. The distal pivot cup 772 engages a corresponding driver's locking projection that torques the distal pivot cup 772 and rotates it to threadably engage the distal bone anchor 740. Note that

  FIG. 14 illustrates the use of a cavity ramp 748 along the leading edge of the cavity that houses the end of the pivot 352, allowing the cavity ramp 748 to proceed further before the pivot body 392 contacts the cavity wall. To do. In this context, “go further” means more than is possible with the same components, except that the cavity walls do not include ramps.

FIG. 14 shows a proximal pivot cup 720 (shown in cross section so that the pivot is visible) and a jam nut 760 that engage within the threaded interior of the proximal bone anchor 744.
FIG. 15 shows an exploded view of another motion holding assembly 1000. The motion holding assembly 1000 differs from the motion holding assembly 300 in several respects. The motion retention assembly 1000 has a distal bone anchor 1004 with an integrated support surface (invisible). The motion retention assembly 1000 has a proximal bone anchor 1008 with a cavity extending through the proximal bone anchor. Pivot 1012 can be inserted into proximal bone anchor 1008 and membrane 1016 coupled to proximal bone anchor 1008 and distal bone anchor 1004. Pivot 1012 is more general in that the length of the pivot body can vary from pivot to pivot and this diversity can be used to create a combination of components tailored to a particular patient's anatomy. Illustrate.

  The distal end of the pivot 1012 that is inserted contacts the support surface of the distal bone anchor 1004. A thread cap 1020 with an integrated support surface (invisible) has a driver engagement portion 1024 that is torqued by a corresponding driver to rotate the thread cap 1020 and onto the thread cap. Axial advancement into the proximal end of the cavity in the proximal bone anchor through engagement of the set of male screws 1028 and the set of female screws 1032 in the cavity of the proximal bone anchor 1008.

  It may be preferable for the cavity to have a support surface that does not interfere with the continuity of the support surface. Thus, if the distal bone anchor is to be provided with an integrated support surface for engagement with the pivot, it should preferably be avoided to use a guide wire for the placement means. Similarly, thread cavities such as element 368 in FIG. 3 are preferably not used because they can cause discontinuities or gaps in the support surface.

  Since there are other means for positioning the distal bone anchor, including the use of locking means and locking recesses, it is desirable to have a continuous bottom against the support surface without adding a cavity.

  FIG. 16 illustrates yet another motion holding assembly 1100 component. The assembly includes a distal bone anchor 1104, a distal O-ring 1108, a distal pivot cup 1112, a pivot 1116, a proximal pivot cup 1120, a proximal O-ring 1124, a proximal bone anchor 1132 and an end cup 1136. The interaction of these components is similar to the interaction between the components, including proximal bone anchor 1132 through screw engagement between the exterior of end cup 1136 and the threaded interior of proximal bone anchor 1132. The ability to impose distraction based on rotation of the end cup 1136 for axial advancement therein is included. An additional component in the motion retention assembly 1100 is a helical spring 1128 that may be coupled between the distal end of the proximal bone anchor 1132 and the proximal end of the distal bone anchor 1104 in actual use. A helical spring 1128 may be placed in the disc space of the motion segment that houses the motion retention assembly 1100. This particular spring will not resist compressive loads when its low energy state is compressed. However, the helical spring 1128 will resist the rotation of the motion retaining assembly 1100 as the motion segment bends due to bending, stretching or lateral bending, but any one of these motions may cause the spiral spring to This is for extending the opposite side of the spring while compressing one side surface.

  FIG. 3 shows an implanted motion retention assembly 300 that includes a prosthetic nucleus 348 that fills the disc space 312 and the outer membrane 460 is filled with a prosthetic nucleus material 464. FIG. 3 should not be construed as a requirement that all motion retention assemblies have an artificial nucleus pulposus or a specific type of artificial nucleus pulposus, as the motion retention assembly was formed with a blocking-sealing membrane as follows: This is because it can be used with an artificial nucleus pulposus.

  In an embodiment of a prosthetic nucleus motion retention assembly that is configured without an expandable membrane, a two-step placement method is generally used, preferably first a blocking-seal membrane (BSM) is connected to the inner surface of the disc space. Introduced through consistent contact, seals the cracks in physiological structures, such as the annulus, and prevents leakage of subsequently introduced bulk prosthetic material. In an artificial nucleus pulposus device used as part of a motion-holding assembly, viscoelastic properties, such as bulk and compression moduli, are designed to substantially "match" the natural disc nucleus, the largest device within the disc space Functionally enables consistent contact of surface areas; “mimics” the distribution and dissipation of physiological loads; prevents bone erosion or implant settling; exhibits sufficient resistance to fatigue and shear forces; Prevent fragmentation and migration from the disc. In embodiments where the motion retention assembly is configured to be used with a block-seal membrane, the block-seal agent is an aqueous solution of a synthesized or purified (non-antigenic) biopolymer or protein, such as collagen or collagen-albumin. A mixture or slurry; or preferably a highly fibrous fibrinogen, thrombin or the like or combinations thereof; highly crosslinked; a dense solid (eg, greater than 65 mg / ml). In one embodiment, the biopolymer protein system is modified to be insoluble, and it is preferred that the protein be type 1 where possible and appropriate. In another embodiment, the sealant is a cross-linking agent such as glutaraldehyde / aldehyde or other suitable functional group modified to minimize toxicity and necrosis, or toxicity or necrosis (eg, citric acid derivatives). Is further included.

  In a preferred embodiment of the barrier-sealing membrane, the cross-linking agent includes functional groups that reduce residues or are naturally metabolized substances. In one embodiment, the cross-linking agent comprises at least one citrate derivative and a synthetic or highly purified biopolymer or protein such as those described above (eg, collagen; collagen-endosperm; elastin, etc.). In a preferred embodiment, the cross-linking agent is a relatively low weight macromolecule containing polar functional groups such as carboxyl or hydroxyl groups modified by electron withdrawing groups, for example succinimidyl groups.

  In yet another embodiment, the barrier-seal and barrier or barrier-seal or barrier (eg, thick layer) comprises hydrocolloids. More specifically, the barrier-seal membrane can be configured to include a water-soluble hydrophilic colloidal component, such as carboxymethylcellulose, in combination with an elastomer or biopolymer as a sealant or tissue repair matrix, respectively. Thus, the barrier membrane includes a non-degradable semi-permeable film. In other embodiments, the barrier may be a pectin base or foam.

  The motion retention assembly can be deployed without simultaneous formation of the prosthetic nucleus, such as when the prosthetic nucleus is not deployed. The motion-retaining assembly prevents the movement or leakage of the prosthetic nucleus material or adventitia through the hernia by contacting the annulus, damping the instantaneous load and inserting an elastomeric ring or collar that distributes the load radially to the annulus It can arrange | position in the assembly procedure containing.

  More specifically for non-expandable elastomers (eg, silicone or polyurethane) for an elastomer ring or collar that contacts the ring, functions as an artificial annulus, attenuates the instantaneous load, and distributes the load radially to the annulus The collar can be used in combination with an expandable membrane. This collar is described in U.S. Application No. 60 / 558,069 “Axially-Deployed Spinal Mobility Devices”, and the contents disclosed in this patent document are also described in this application. It shall be disclosed. This collar is first placed in a folded fashion and then delivered to the disc space. The collar is adapted to fit, i.e., to strengthen the annulus and prevent movement or leakage of the membrane through the hernia. The cross section of the collar is stiff compared to an expandable membrane. In a preferred embodiment, the collar has a height of about 8-12 mm and a thickness of about 0.5-1.0 mm.

  Another way to reinforce the annulus is to use an expandable outer membrane (instead of the outer membrane 460 above) between the distal and proximal anchor portions, in which case the outer membrane is expanded. Then, a membrane material harder than the membrane material arranged near the endplates of the proximal and distal vertebral bodies is arranged on the annulus fibrosus.

This annulus-enhanced adventitia can be placed alone or in combination with an elastomeric ring or collar that contacts the annulus, so that the motion retention assembly device is not subject to the invasiveness of current total disc replacement (TDR) procedures. It functions effectively as a (PD) and provides the same load bearing characteristics as a natural disc. A balance between integrity and stiffness, i.e., semi-flexible elastomeric configurations, whether provided as collars and outer membranes, or collars or outer membranes, in artificial nucleus pulposus with integral high stiffness components as described above The addition of the element allows the motion retaining assembly to protect the motion segment from impact without collapsing under compressive loads. That is, the semi-flexible component provides momentary load damping and conformal contact between the motion-retaining assembly and the physiological structure, i.e. the annulus and the endplates of the proximal and distal vertebral bodies (harmonic interface). The effective surface area of) is also maintained. This in turn results in a more uniform radial load distribution and a more approximate physiological load sharing. In accordance with this aspect of the invention, the motility devices disclosed herein are less likely to cause sedimentation and transition syndrome, or sedimentation or transition syndrome.
(Preferred material)
In a preferred embodiment of the present invention, the inelastic component motion retention assembly of the present invention is preferably configured to include a biocompatible high strength material, eg, MP35N; Co—Cr alloy such as Stellite ™. . In the context of this specification, “biocompatible” refers to the absence of a chronic inflammatory response when physiological tissue is contacted with or exposed to the materials and devices of the present invention (eg, wear debris). In addition to biocompatibility, in another aspect of the invention, the material comprising the motion retention assembly is sterilizable; preferably visible and imageable, or visible or imageable, eg, fluoroscopy Top; or alternatively through CT (Computerized Tomography) or MRI (Magnetic Resonance Imaging), this last listed imaging method indicates that the material is substantially free of Fe (iron). In addition, considering contrast, detail, and position sensitivity, contrast agents or other materials (eg, barium sulfate) may be needed from time to time and used when constructing the device, if appropriate, Assist or modify radiation opacity. Also, as used herein, high strength means that the material of the exemplary embodiment generally meets the ISO 10993 standard for long-term implants and / or is about 1250 Newtons (N ) (280 lbf) to 2250 N (500 lbf) axial compression; transverse and longitudinal longitudinal shear stress of 100 N (25 lbf) and 450 N (100 lbf) long-term normal range physiological loads (ie, implant lifetime) Or a maximum of about 40 × 10 ⁶ cycles). In addition, the motion retaining assembly of the present invention provides a total axial compression of about 8000 Newton (N) (1800 lbf); a lateral shear stress of about 2000 N (450 lbf); It is preferable to be able to reliably withstand maximum physiological loads over a short range of motion (eg, over about 20 consecutive cycles).

In a preferred embodiment, the pivot and support surface is a Co—Cr alloy such as Stellite ™. In addition, the end of the pivot can be treated (eg, surface or heat treated as appropriate) to increase wear resistance. Thus, the chemical composition can be the same, but the end is now a different material than the middle, and in this context, the “material” is a combination of composition and processing to produce a property. . In yet another embodiment, the pivot body can be made of another compatible material (eg, a material that does not react to cause electrochemical corrosion), while the pivot end is made more wear resistant. The material used for the pivot body and the pivot body part, or the material used for the pivot body part or the pivot body part can be treated to increase fatigue resistance relative to the material used for the pivot end. Rather than being machined from a single piece of metal, making the pivot from two pivot ends and one pivot body makes the end and body the same material, for example a highly polished that is commercially available Even if made from highly circular spheres, it is not an unreasonable manufacturing method. A preferred material for the retaining ring 484 is titanium.
(Details on how to install the exercise holding assembly)
US Application No. 60 / 621,730, filed Oct. 25, 2004, “Multi-Part Assembly for Introducing Implants into the Spine” is a priority. The contents of which are claimed as documents and disclosed in the same document are also disclosed in the present application.Details regarding tools and methods for mounting the motion retaining assembly are found in that application.

  Since it can be useful to look at the interaction of the motion holding assembly with various drivers, the process steps are given below, but how the driver interacts with the motion holding assembly rather than the details of building the driver device. Emphasis on.

  FIG. 17 shows the distal bone anchor 340 and the proximal bone anchor 344, with the membrane 460 coupled to the distal bone anchor 340 and the proximal bone anchor 344. In this example, the thread pitch of the external thread 356 on the distal bone anchor is the same as the thread pitch of the set of external threads 404 on the proximal bone anchor. The keyed driver assembly 2000 has a key 2004 with a shoulder 2008. The key 2004 slides into slots in the proximal and distal bone anchors (existing). Accordingly, the keyed driver assembly 2000 prevents the proximal bone anchor 344 from rotating relative to the distal bone anchor 340. Keying in synchrony with precise control of the distance between bone anchors is approached while the leading edge of the external thread on the proximal bone anchor enters the proximal vertebral body and the distal bone anchor advances toward the distal vertebral body. Allows entry into the beginning of the thread path left in the distal bone anchor, screwed through the distal vertebral body.

  A retaining rod 2012 having an external thread 2016 engages an internal thread 368 of the distal bone anchor 340. The retaining rod 2012 is rotatable relative to the driver tip 2018 so that the distal bone anchor 340 is pulled to contact the driver tip 2018.

  Similarly, the proximal anchor retention joint 2088 is attached to the outer sheath 2096 so that the proximal anchor retention joint 2088 with the external thread 2092 is rotatable relative to the driver tip 2018. Rotation of proximal anchor retention joint 2088 causes engagement of male thread 2092 and female thread 416 of proximal anchor 344, pulling proximal anchor 344 down to shoulder 2008. Both anchors are held in contact with components of the keyed driver assembly 2000 and the position of the distal bone anchor 340 relative to the proximal bone anchor 344 is set based on the distance between the shoulder 2008 and the driver tip 2018. Can be done. Control over the distance between two separate bone anchors allows two bone anchors having the same large diameter to be inserted without cross-screwing of the proximal vertebral body.

  FIG. 18 illustrates a set of locking projections 2020 to engage the locking recess (see element 2028 in FIG. 19) in the distal bone anchor 340 of the distal pivot cup 372 by the distal cap driver 2022. Indicates delivery. FIG. 19 shows the release of the driver by extension of the atraumatic tip 2024 causing axial movement of the driver away from the distal end of the distal end cup 372 so that the locking projection 2020 is released from the locking recess 2028. The In one embodiment, the atraumatic tip 2024 is selected to be softer than the support surface at the distal end cup 372 so that the support surface is not damaged.

  FIG. 20 shows a distraction and insertion tool 2032 used to distract the motion segment, then place the prosthetic nucleus material on the membrane 460 and expand the membrane 460 to fit within the disc space gap. The insertion tool 2032 has a set of external threads 2036 that engage a set of internal threads 416 on the proximal bone anchor 344. The distal end of the insertion tool 2032 is an atraumatic tip 2042 designed to contact without damaging the support surface in the distal pivot cup 372. While extending axially, the distraction and insertion tool 2032 pushes the atraumatic tip 2042 into the distal pivot cup 372 and the vertebral body engaged with the distal bone anchor 340 relative to the vertebral body engaged with the proximal bone anchor 344. Move. After making the desired amount of distraction, the inner channel 2048 is used to apply artificial nucleus pulposus material delivered through a set of fenestrations 2052 to fill and expand the membrane 460. The prosthetic nucleus material is inserted until the membrane 460 and the endplates of the two vertebral bodies and the annulus walls match.

  After the prosthetic nucleus material is cured, the insertion tool 2032 can be removed, leaving a gap in the prosthetic nucleus material where the insertion tool was present during the formation of the prosthetic nucleus (element 348 in FIG. reference). The non-implanted device shown in FIG. 20 did not actually contain the prosthetic nucleus material because the illustrated procedure shows a device that is not implanted into the motion segment. If you are observing sensitively, you will notice that subsequent figures in this procedure do not show expandable membranes.

  FIG. 21 illustrates the delivery of pivot 352 by delivery tool 2056 that engages the proximal end 388 of the pivot by O-ring 2060. FIG. 22 shows the pivot 352 after delivery, with the distal end 384 of the pivot contacting the support surface in the distal pivot cup 372 and the proximal end 388 of the pivot being pushed over the O-ring 2060. The delivery of pivot 352 will not be hindered by hardened prosthetic nucleus material. This is because when the insertion tool 2032 occupies the volume during filling and curing, the material does not appear to have cured along the central axis of the motion retaining device. In that the compressive force on the prosthetic nucleus caused movement of the prosthetic nucleus material in the direction of the longitudinal centerline of the motion retention assembly, the pivot 352 has a reduced opening by moving the flexible prosthetic nucleus material. Can be pushed through the part.

  FIG. 23 illustrates the use of a driver 2064 that engages the proximal pivot cup 420 by a retaining rod 2068 that threadably engages the thread cavity 432 in the proximal pivot cup. The driver head 2072 engages a corresponding driver engagement portion 428 (best seen in FIG. 3) in the proximal pivot cup 420 and provides torque to cause the proximal pivot cup 420 to be axially proximal bone anchor. Advances into 344 and thus pushes distal pivot cup 372 and thus distal bone anchor 340 through pivot 352 to move distal bone anchor 340 relative to proximal bone anchor 344. When implanted in a vertebral body, this will pull the vertebral body apart and impose an axial distraction.

  Comparison of FIGS. 23 and 24 illustrates the concept of component movement, with pivot 352 being more closely centered between distal bone anchor 340 and proximal bone anchor 344. As described above, the pivot 352 can be provided in various lengths so that the pivot 352 is properly oriented with respect to the disc space after imposing a stretch.

  FIG. 24 illustrates a jam nut driver 2076 with a driver head 2080 that engages a jam nut through a thread cavity 352 (best seen in FIG. 3) and a driver engagement portion 448 (best seen in FIG. 3). A holding rod 2084 is shown.

  FIG. 25 provides an alternative to the keyed driver assembly 2000 shown in FIG. Dual anchor driver 2100 simultaneously engages distal bone anchor 2108 and proximal bone anchor 2112 using polygonal torque driver 2104. These bone anchors have external threads (2116 and 2120) having the same small diameter, the same large diameter, the same pitch and the same winding. Delivery of two bone anchors to avoid cross-screwing of helical screw cutting left in the proximal vertebral body by the distal anchor male thread 2116 as the proximal anchor male thread 2120 is rotated into the proximal vertebral body Need to be adjusted. Having control over the relative position of the bone anchor during rotation and axial movement of the bone anchor allows this. Here, A) the action of the retaining rod 2012 that engages the internal thread 2124 of the distal anchor 2108 and pulls the distal anchor 2108 to secure it to the distal tip 2128 of the polygonal torque driver 2104 and B) a set of Control is provided by the action of a proximal anchor retention joint 2132 that engages male thread 2136 with female thread 2142 of proximal anchor 2112 and secures proximal anchor 2112 to shoulder 2146 of polygon torque driver 2104. Retention rod 2012 and proximal anchor retention joint 2132 are coupled to dual anchor driver 2100, each being rotatable relative to polygonal torque driver 2104.

  Although not immediately visible in FIG. 25, the dual anchor driver 2100 using the polygonal torque driver 2104 needs to interact with the slot in the bone anchor, as is necessary when using the keying driver of FIG. Absent. Hexagons are commonly used as torque drivers, but those skilled in the art will appreciate that other polygons such as triangles, squares, pentagons, octagons, etc. can be used. More complex shapes such as stars or asymmetric shapes can be used, but simple polygons are reasonable.

  One skilled in the art will appreciate that other relationships of the driver and the two bone anchors can result in the timely delivery of the proximal bone anchor to a threaded path cut into the proximal vertebral body by the distal bone anchor. One such solution is a double hex head driver, such as a dual hex head hex driver having a hex head engaging a corresponding driver engagement portion in the cavity of the distal bone anchor, an upper hex head. And a spacer shaft extending from a larger lower hex head that engages the inner wall of the distal bone anchor. When the distal and proximal bone anchors are preloaded into a double hex driver and held there until implanted into the vertebral body (as with a retention rod and threaded retention joint), Since the rotational orientation and relative axial position do not change while in contact with the heavy hexagon head, the orientation of the two bone anchors can be controlled.

If the distal bone anchor is narrower than the proximal bone anchor, a double hex driver with a smaller distal head is appropriate, such as using a different thread pitch for distraction. However, different thread pitches are not the preferred means of distraction.
(Preferred method of arrangement and use)
The present invention can be implemented with many variations as described above, and these variations affect the process for performing, but an overview of the preferred motion retention assembly (MPA) and placement process 2200 for artificial disc replacement. Is instructive. One relates to the distal and proximal components of a spinal implant having the same rod diameter and the same large diameter, small diameter, thread pitch, and wound male threads, and the proximal vertebral body through the passage of the distal component It is necessary to have timely delivery of a proximal component that enters a spiral threaded path cut into the threaded component, which serves to secure the implant to the adjacent vertebral body. In this embodiment, it is in an intermediate position relative to the distal and proximal components and is configured to be integrated therewith, and then expanded by insertion of artificial nucleus pulposus material, and adjacent distal and proximal vertebrae. A flexible membrane is used that forms a prosthetic nucleus component within the intervertebral disc space.

  A preferred driver for two threaded components of the same diameter (as described above) is an elongated hexagonal driver similar to the driver shown in FIG. Since many details regarding bone anchors and drivers have already been introduced, this flow diagram serves as an overview rather than a detailed introduction.

  Step 2210 Place distal and proximal components on the device driver assembly. These two anchors joined by a flexible membrane are placed in an anchor driver assembly. The driver assembly is shown in FIG. 25 in that it uses an elongated torque driver, in this case a hexagonal torque driver having an elongated portion with a constant cross section (perpendicular to the longitudinal axis). Similar to anchor driver assembly.

  Attaching the driver assembly secures the distal component to the distal end of the driver, which is held at the tip during insertion and advanced axially and distally by a threaded retaining rod; Securing the proximal bone anchor to the shoulder in the dual anchor driver assembly through the use of a proximal anchor retention joint. By securing the two bone anchors to the driver assembly, a predetermined spatial separation between the distal and proximal components is maintained and the flexible membrane located between them is stretched, so The membrane is slightly necked in and is less likely to be damaged while passing through the proximal vertebral body.

  Step 2220 Insert the anchor driver assembly over the guidewire and advance the anchor driver assembly through a pre-made axial channel that includes a hole through the proximal vertebral body and a hole in the distal vertebral body. The hole in the proximal vertebral body is approximately the same as the small diameter of the male screw on both bone anchors.

  Step 2230 Torque is applied using an anchor driver assembly to rotate the distal bone anchor through the proximal vertebral body and advance it axially, thereby forming a helical thread path through the first vertebral body.

  Step 2240 Apply torque continuously to advance the bone anchor axially, the bone anchor being held in the anchor driver assembly at a spatially maintained distance, securing the distal component to the distal vertebral body, and The proximal component is secured to the proximal vertebral body without cross-screwing or re-screwing in the distal vertebral body.

  Step 2250 Once the bone anchors are placed in the respective vertebral bodies, the distal bone anchors are released from threaded engagement with the retention rod and the proximal bone anchors are released from the proximal anchor retention joint. The retaining rod and proximal anchor retention joint are rotatable relative to the elongated hexagonal driver.

Step 2260 Remove the anchor driver assembly.
Step 2270 Using a locking mechanism to engage the distal pivot cup Insert the distal pivot cup by engaging the distal pivot cup with the driver, as shown in FIGS.

Step 2280 Remove the distal pivot cup driver from the distal pivot cup and remove the distal pivot cup driver.
Step 2290 Insert the distractor / injector tool into the implanted bone anchor and the atraumatic tip of the distractor / injector tool contacts the support surface of the distal pivot cup.

  Step 2300 Proximal vertebral body by axially advancing the distractor / injector tool relative to the proximal bone anchor through screw engagement within the proximal bone anchor and pushing through the atraumatic tip on the distal pivot cup The distal vertebral body is moved relative to.

  Step 2310 Injecting prosthetic nucleus material through the outer opening in the fluidic communication between the interior of the distractor / injector and the interior of the distractor / injector and the flexible membrane, fully expanding and filling the flexible membrane; A prosthetic nucleus component of the artificial disc device is formed, and the prosthetic nucleus component is in consistent contact with the surface of the disc space.

Step 2320 Cure the injected material.
Step 2330 Remove the distractor / injector tool.
Step 2340 Engage the proximal end of the pivot with the delivery tool. The delivery tool is inserted and the distal end of the pivot is pushed through the hardened material into the distal pivot cup while simultaneously releasing the proximal end of the pivot from engagement with the delivery tool. A preferred delivery tool is shown in FIGS.

Step 2350 Remove the pivot delivery tool from the axial channel.
Step 2360 Insert a threaded proximal pivot cup into the proximal bone anchor. Engage the threads in the proximal bone anchor and advance the proximal pivot cup to contact the proximal end of the pivot.

  Step 2370 Further rotation and axial advancement of the proximal pivot cup pushes the pivot against the distal pivot cup, thus resulting in additional augmented distraction of the distal vertebral body relative to the proximal vertebral body. The ability to additionally adjust vertebral distraction in this manner is provided by the prosthetic nucleus component of the prosthetic disc device, the mechanical “in-line” subassembly including the pivot, support surface, elastomeric component, and the vertebral body. Allows selective distribution of axial load support between fixed distal and proximal threaded components. This distraction imposes a compressive force on one or more components that can undergo elastic deformation during compression.

Step 2380 Remove the driver from the pivot cup.
Step 2390 Engage the jam nut with the driver. Insert the screwdriver and jam nut into the axial channel. Engage and tighten the thread on the jam nut to the thread on the proximal bone anchor. The preferred method uses the same driver for the pivot cup and jam nut.

Step 2400 Remove the driver from the jam nut and remove the driver from the axial channel.
This completes the method of placing the motion retention device in the axial channel in the spine and the surgical site can be sutured by the surgeon.

One skilled in the art will appreciate that the alternative embodiments shown above are not universally mutually exclusive, and that alternative embodiments are possible in some cases using two or more of the above variations. . Similarly, the invention is not limited to the specific examples or specific embodiments provided to facilitate understanding of the invention. Further, as is known to those skilled in the art, the scope of the present invention covers a range of variations, modifications and alternatives to the components described herein. The legal limitations of the claims are set forth in the claims, and will evolve to cover their legal equivalents.
(Related applications)
No. 60 / 621,148, “Spinal Mobility Preservation Assemblies,” filed Oct. 22, 2004, and US application filed Oct. 25, 2004. Application No. 60 / 621,730 entitled “Multi-Part Assembly for Introducing Axial Implants into the Spine” and disclosed in these documents. This application is also disclosed in the present application, which is incorporated by reference in four U.S. patent applications Nos. 10 / 972,184, 10 / 927,039, filed Oct. 22, 2004. 10 / No. 72,040 and 10 / 972,176 are claimed and the contents disclosed in these documents are also disclosed in the present application. US Patent Application No. 60 / 558,069 filed on 31st and 60 / 513,899 filed on 23rd October 2003 claim priority. The contents disclosed in the literature shall also be disclosed in the present application, which claims priority to US patent application Ser. No. 11 / 199,541 filed Aug. 8, 2005. The contents disclosed in this application and US Patent Application No. 60 / 599,989 filed on August 9, 2004, claimed as priority documents for this application, are also disclosed herein. It shall be assumed.

  This application is also an extension of research done by the applicant and is incorporated by reference to a series of US applications, provisional applications and registered patents. This includes US Patent Application No. 60 / 182,748 filed February 16, 2000; 09 / 640,222 filed August 16, 2000 (currently No. 6,575). No. 10974, filed on June 11, 2003; 09 / 684,820 filed on October 10, 2000 (currently No. 697). No. 10 / 430,751 filed on May 6, 2003; No. 60 / 182,748 filed February 16, 2000; 2001 09 / 782,583 (registered as 6,558,390) filed on Feb. 13; 09 / 848,556 filed on May 3, 2001; 2002 No. 10 / filed on April 18 No. 25,771 (registered as No. 6,899,716); No. 10 / 990,705 filed on November 17, 2004; No. 10 / filed on May 6, 2003 No. 430,841; 09 / 710,369 filed on Nov. 10, 2000 (registered as No. 6,740,090); No. 10 / filed on May 25, 2004; No. 853,476; 09 / 709,105 filed on Nov. 10, 2000 (registered as No. 6,790,210); No. 09 / filed on Feb. 13, 2001; 782,534; U.S. patent applications 10 / 971,779, 10 / 971,781, 10 / 971,731, and 10 / 972,077, all filed on October 22, 2004. , 10/971 No. 765, No. 10 / 972,065, No. 10 / 971,775, No. 10 / 971,299, No. 10 / 971,780; No. 60/706, filed on Aug. 9, 2005. No. 704; No. 11 / 189,943 filed Jul. 26, 2005; filed Dec. 3, 2002; currently US Pat. No. 6,921,403 309, 416 are included. While these applications are incorporated by reference to provide further details, these other applications (including those later registered as patents) were created early and have a different focus than this application. It should be noted that it had. Accordingly, to the extent that the use of teachings or terminology differs from this application in any of these incorporated applications, it is adjusted in this application.

The side view which shows each part of a human spine. 1 is a schematic diagram illustrating an anterior axial transsacral access method for forming an axial channel in a spine that can be used to prepare an axial channel in the spine for use in the present invention. FIG. 6 is another schematic diagram illustrating an anterior axial transsacral access method for forming an axial channel in the spine, which can be used to prepare the axial channel in the spine for use in the present invention. FIG. 6 is another schematic diagram illustrating an anterior axial transsacral access method for forming an axial channel in the spine, which can be used to prepare an axial channel in the spine for use in the present invention. FIG. 6 is a schematic diagram illustrating a motion retention assembly 300 implanted in a spinal motion segment. FIG. 4 is an exploded view showing another view of the components shown in FIG. 3. FIG. 4 is a schematic diagram illustrating the motion retention assembly in FIG. 3 with the quarter circles removed from the distal bone anchor 340 and the proximal bone anchor 344 to represent the components in the assembly set of components. FIG. 2 is a schematic diagram illustrating the motion retention assembly 300 being the same motion retention assembly 300, but with the entire assembly's quarter circle removed; The enlarged view which shows the enlarged part of FIG. The schematic diagram which shows the effect of using two different pivot body part width | variety. The schematic diagram which shows the effect which changes the depth of a pivot end cup. The schematic diagram which shows the advantage of the dual pivot with respect to a single pivot. FIG. 5 is a schematic diagram illustrating an asymmetric cavity in a pivot cup that allows a greater amount of additional permissible translation in one direction compared to the other direction. The schematic diagram which shows an asymmetrical pivot. FIG. 3 is an exploded view showing one motion holding assembly having an elastic member. Sectional drawing which shows the cross section of the pivot 900 which the process spring has connected two ends. FIG. 6 is a schematic diagram illustrating another embodiment of a motion retention assembly having a male threaded distal pivot cup. FIG. 5 is an exploded view showing another motion retention assembly having a distal implant member having an integral support surface. FIG. 5 is an exploded view showing components of yet another motion holding assembly having a helical spring. FIG. 3 is a cross-sectional view showing a cross-section of a keyed driver assembly for delivery of two components to be implanted. FIG. 3 is a cross-sectional view showing a cross section of a delivery tool during delivery of a distal pivot cup. FIG. 3 is a cross-sectional view showing a cross section of a delivery tool during delivery of a distal pivot cup. The perspective view which shows the place where the quarter circle was removed from the distractor / injector tool. FIG. 3 is a cross-sectional view showing a cross section of a delivery tool during delivery to a dual pivot distal pivot cup. FIG. 3 is a cross-sectional view showing a cross section of a delivery tool during delivery to a dual pivot distal pivot cup. FIG. 6 is a cross-sectional view showing a cross section of the delivery tool during delivery of the proximal end cup. Sectional drawing which shows the cross section of the delivery tool during delivery of a jam nut. FIG. 6 is a perspective view showing a distal portion of a driver assembly for delivery of two components implanted using an elongated hexagonal screwdriver. FIG. 5 is a flow diagram illustrating a particular method for placement of a motion retention assembly. FIG. 5 is a flow diagram illustrating a particular method for placement of a motion retention assembly.

Claims (55)

A spinal motion retention assembly suitable for use in a spinal motion segment comprising:
A distal bone anchor, and the distal bone anchor is located within the distal bone anchor accessible from the distal end, proximal end, and proximal end, suitable for accommodating a corresponding driver head And a set of threads external to the distal bone anchor and adapted to engage a distal vertebral body in the motion segment;
A pivot including a distal end, a proximal end, and an intermediate portion therebetween,
A distal pivot cup, an exterior corresponding to a portion of the interior cavity of the distal bone anchor, and a proximal end of the distal pivot cup for receiving the distal end of the pivot Including a cavity in
A proximal bone anchor, the proximal bone anchor extending through the interior of the proximal bone anchor from the distal end, the proximal end, the distal end to the proximal end, and a corresponding driver head; Including a cavity suitable for containment and a set of threads external to the proximal bone anchor adapted to engage a proximal vertebral body in the motion segment;
A proximal pivot cup, the proximal pivot cup including a distal end, a proximal end, and a cavity at the distal end of the proximal pivot cup for receiving the proximal end of the pivot; ,
A spinal motion retention assembly comprising at least one component that is elastically deformable and positioned between the distal bone anchor and the proximal bone anchor.   The spinal motion retention assembly according to claim 1, wherein the distal bone anchor is engaged by a driver tool to retain the distal bone anchor in the driver head.   The spinal motion retention assembly according to claim 2, wherein the proximal bone anchor is engaged by the driver tool to retain the proximal bone anchor on a portion of the driver tool.   The distal bone anchor that engages the driver tool and the proximal bone anchor that engages the driver tool without passing through the thread path that is cut into the proximal vertebral body by passing through the spine The spinal motion retention assembly of claim 3, wherein the spinal motion retention assembly is capable of being delivered to the distal and proximal vertebral bodies by an axial channel at. The large diameter of the set of threads outside the distal bone anchor is smaller than the large diameter of the set of threads outside the proximal bone anchor;
The set of thread turns on the exterior of the distal bone anchor is the same as the set of thread turns on the proximal bone anchor;
The pitch of the set of threads on the exterior of the distal bone anchor is finer than the set of threads on the proximal bone anchor, and the distal bone anchor and the The rotation of the proximal bone anchor moves the distal vertebral body engaged with the distal bone anchor relative to the proximal vertebral body engaged with the proximal bone anchor, distracting the disc space. Item 4. The spinal motion holding assembly according to Item 3.   The distal bone anchor can be disposed on a guide wire because a cavity in the distal bone anchor extends from a proximal end to a distal end along a longitudinal axis. The spinal motion retention assembly according to claim 1.   The proximal pivot cup further includes a set of male threads corresponding to an initial thread portion of the proximal bone anchor cavity and a driver cavity at a proximal end of the proximal pivot cup, the driver cavity corresponding to a driver Because it is configured to receive a head, the driver head is capable of applying torque to the proximal pivot cup, and the proximal pivot cup is placed along a longitudinal axis of the proximal bone anchor. The spinal motion retention assembly of claim 1, wherein the spinal motion retention assembly is selectively advanced to move the pivot toward the distal bone anchor and extend the distance between the distal vertebral body and the proximal vertebral body. A jam nut further comprising:
The distal end;
A proximal end;
A jam nut body threaded at least partially threaded along the exterior of the jam nut between them and engageable with a threaded cavity of the proximal bone anchor;
A driver cavity opening at least at the proximal end of the jam nut, the corresponding driver engaging and applying torque to the driver cavity, and the jam nut along the longitudinal axis of the proximal bone anchor 8. The spinal motion retention assembly of claim 7, wherein the spine motion retainer is advanced to move the proximal end of the jam nut into contact with the proximal end of the proximal pivot cup.   A spinal motion segment having an implanted spinal motion retention assembly is capable of moving in flexion, extension, lateral bending to the right, lateral bending to the left, clockwise rotation and counterclockwise rotation. The spinal motion retention assembly of claim 1.   The spinal motion segment having an implanted spinal motion holding assembly has a bending of about 12 °, an extension of about 8 °, a lateral bending of about 9 ° to the right, a lateral bending of about 9 ° to the left, about 2 °. 10. The spinal motion retention assembly of claim 9, wherein the spinal motion retention assembly is capable of motion with a clockwise rotation of about 2 degrees and a counterclockwise rotation of about 2 degrees.   The distal vertebral body is capable of translating relative to the proximal vertebral body in anterior / posterior and transverse / left transverse directions and of at least one component of the spinal retention assembly The spinal motion retention assembly of claim 10, capable of translation resulting from elastic deformation and elastic recovery.   The spinal motion retention assembly of claim 1, wherein the at least one component capable of undergoing elastic deformation is formed from a material selected from fluoropolymer elastomers, polyurethane elastomers, and silicone rubbers.   The spinal motion retention assembly of claim 1, wherein the at least one component capable of undergoing elastic deformation comprises a spring that deforms recoverably upon compression.   The spinal motion retention assembly according to claim 1, wherein at least one component capable of undergoing elastic deformation is located between the distal pivot cup and the distal bone anchor.   The spinal motion retention assembly according to claim 1, wherein at least one component capable of undergoing elastic deformation is located between the proximal pivot cup and the proximal bone anchor.   The spinal motion retention assembly of claim 1, wherein at least a portion of the pivot is capable of undergoing elastic deformation.   The spinal motion retention assembly of claim 16, wherein the pivot is at least partially comprised of a processing spring.   The spinal motion retention assembly of claim 1, wherein at least a portion of the distal pivot cup is capable of undergoing elastic deformation.   The spinal motion retention assembly of claim 18, wherein the distal pivot cup is at least partially comprised of a working spring.   The spinal motion retention assembly of claim 1, wherein at least a portion of the proximal pivot cup is capable of undergoing elastic deformation.   21. The spinal motion retention assembly of claim 20, wherein the proximal pivot cup is at least partially comprised of a processing spring. The proximal pivot cup is configured to move longitudinally relative to the distal end of the proximal bone anchor cavity without having to rotate to move longitudinally to the distal end of the cavity. The spinal motion retention assembly comprises:
An expandable membrane that extends from the proximal end of the distal bone anchor to the distal end of the proximal bone anchor and functions as an artificial nucleus pulposus when filled with an artificial nucleus pulposus material and distributes the force to the annulus When,
A threaded cap, the threaded cap comprising:
The distal end;
A proximal end;
The body between the distal end and the proximal end, and the outer surface of the body is threaded against at least a portion of the outer surface, the thread being the first screw of the proximal bone anchor cavity Corresponding to the mountain part,
An implanted proximal bone anchor having a driver cavity at a proximal end of the threaded cap, wherein a driver head inserted into the proximal end of the proximal bone anchor is engageable within the driver cavity; Rotating the threaded cap relative to the distal bone, advancing the threaded cap distally toward the distal bone anchor and pressing against the pivot, the proximal bone anchor and the distal bone Increasing the longitudinal distance between the anchors and selectively altering the distribution of the shared axial compressive load carried by the artificial nucleus pulposus and the external threads on the proximal bone anchor and the external threads on the distal bone anchor; The spinal motion retention assembly according to claim 1, wherein: The pivot is
A first set of biomechanical properties optimized for wear and used in constructing the distal and proximal ends;
A second set of biomechanical properties optimized for fatigue resistance and comprising a material used in constructing a pivot body between the distal end and the proximal end. Item 2. The spinal motion holding assembly according to Item 1.   And further comprising an expandable membrane extending from the proximal end of the distal bone anchor to the distal end of the proximal bone anchor, the membrane acting as an artificial nucleus pulposus when loaded with an artificial nucleus pulposus material The spinal motion retention assembly of claim 1, wherein the spinal motion retention assembly is dispersed in the annulus fibrosus.   The proximal pivot cup is configured for threaded engagement with the proximal bone anchor, and a motion retention assembly is implanted in the proximal and distal vertebral bodies and the expandable membrane is hardened. Once filled, rotation of the proximal pivot cup within the proximal bone anchor can be used to advance the threaded proximal pivot cup distally toward the distal bone anchor, the pivot 25. selectively disperse the load distribution between A) the prosthetic nucleus and annulus and B) the external thread on the proximal bone anchor and the external thread on the distal bone anchor. A spinal motion retention assembly as described in.   The expandable membrane includes a membrane material having a first stiffness in at least a portion of the annulus and a second stiffness in at least a portion of the proximal vertebral body and at least a portion of the distal vertebral body. The first stiffness is higher than the second stiffness, and after expansion, the expanded membrane is the vertebral endplate of the proximal vertebral body and the distal vertebral body 25. The spinal motion holding assembly according to claim 24, wherein the spinal motion holding assembly is configured to be more rigid in an outer circumferential direction and a radial direction in the central portion in contact with the annulus than the end portion in contact with the annulus.   25. The spinal motion retention assembly of claim 24, further comprising an elastomeric collar that contacts the annulus and surrounds at least a portion of the expanded membrane after expansion.   The spinal motion retention assembly of claim 1, further comprising a volume of prosthetic nucleus material disposed in the disc space.   The spinal motion segment includes a disc space between the distal vertebral body and the proximal vertebral body, and the spinal motion holding assembly is a layer of a blocking-sealing material that conformally contacts the surface of the disc space. 30. The spinal motion retention assembly of claim 28, further comprising:   The distal end of the distal bone anchor further comprising a soft intermediate portion coupled to a proximal end of the distal bone anchor and a distal end of the proximal bone anchor, the distal to the proximal vertebral body along the longitudinal axis of the assembly; The spinal motion retention assembly of claim 1, wherein a range of motion of the distal vertebral body causes a reversible change in the shape of the soft intermediate.   31. The spinal motion retention assembly of claim 30, wherein the soft intermediate is a helical spring that couples the proximal bone anchor to the distal bone anchor.   32. The spinal motion retention assembly of claim 31, wherein the helical spring is manufactured from a single piece of material.   The spinal motion retention assembly of claim 1, further comprising an expandable flexible membrane that provides a sealed volume between a distal end of the proximal bone anchor and a proximal end of the distal bone anchor.   34. The spinal motion retention assembly of claim 33, further comprising a prosthetic nucleus material disposed on the expandable flexible membrane and expanding the expandable flexible membrane into the disc space.   35. Spinal motion retention according to claim 34, wherein the expandable flexible membrane is expanded by a prosthetic nucleus material, filling the disc space and conformably contacting a distal vertebral body, a proximal vertebral body, and an annulus fibrosis. assembly.   The spinal motion retention assembly according to claim 1, wherein the distal pivot cup has a set of external threads corresponding to a set of internal threads in at least a portion of a cavity within the distal bone anchor.   A cavity in the distal bone anchor has an alignment slot, a cavity in the proximal bone anchor has an alignment slot, and the distal bone anchor and the proximal bone anchor are proximal to the distal bone anchor. The spinal motion retention assembly of claim 1, wherein the spinal motion retention assembly can be advanced axially into the spinal motion segment by a driver that maintains a position relative to a bone anchor. The large diameter of the set of threads on the exterior of the distal bone anchor is substantially equal to the large diameter of the set of threads on the exterior of the proximal bone anchor;
The pitch of the set of threads on the exterior of the distal bone anchor is equivalent to the pitch of the set of threads on the exterior of the proximal bone anchor;
A thread turn on the exterior of the distal bone anchor is equivalent to a set of threads on the proximal bone anchor;
Alignment slots in the distal bone anchor and the proximal bone anchor assist in timely delivery of the proximal bone anchor, and a set of thread start portions in the proximal bone anchor enters the proximal vertebral body. 38. The spinal motion retention assembly of claim 37, wherein the spinal motion retention assembly is advanced to enter a threaded path cut into the proximal vertebral body by a set of threads external to the distal bone anchor.   The distal bone anchor has driver assembly engagement means, the proximal bone anchor has driver assembly engagement means, and the distal bone anchor and proximal bone anchor are held in the driver assembly, the driver assembly To maintain the relative position of the distal bone anchor relative to the proximal bone anchor, the two bone anchors can be advanced axially into the spinal motion segment while being retained by the driver assembly, The spinal motion of claim 1, wherein a distal bone anchor is provided to the proximal vertebral body by timely delivery and engages a helical thread in the proximal vertebral body that has been pre-cut by passage of the distal vertebral anchor. Retaining assembly. A spinal motion retention assembly suitable for use in a spinal motion segment comprising:
A distal bone anchor, and the distal bone anchor is located within the distal bone anchor accessible from the distal end, proximal end, and proximal end, suitable for accommodating a corresponding driver head An external cavity and a thread external to the distal bone anchor and adapted to engage a distal vertebral body in the motion segment;
A pivot including a distal end, a proximal end, and an intermediate portion therebetween,
A distal pivot cup, an exterior corresponding to a portion of the cavity within the distal bone anchor, and a proximal of the distal pivot cup for receiving the distal end of the pivot Including a cavity at the end;
A proximal bone anchor, the proximal bone anchor extending through the interior of the proximal bone anchor from the distal end, the proximal end, the distal end to the proximal end, and a corresponding driver head; Including a cavity suitable for containment and a set of threads external to a proximal bone anchor configured to engage a proximal vertebral body in the motion segment;
An expandable membrane that extends from the proximal end of the distal bone anchor to the distal end of the proximal bone anchor and functions as an artificial nucleus pulposus when loaded with an artificial nucleus pulposus material and distributes the force to the annulus When,
A proximal pivot cup, the proximal pivot cup including a distal end, a proximal end, and a cavity at the distal end of the proximal pivot cup for receiving the proximal end of the pivot; ,
A spinal motion retention assembly comprising at least one elastically deformable component positioned between the distal bone anchor and the proximal bone anchor. A spinal motion retention assembly suitable for use in a spinal motion segment comprising:
A distal bone anchor, and the distal bone anchor is located within the distal bone anchor accessible from the distal end, proximal end, and proximal end, suitable for accommodating a corresponding driver head And a screw thread adapted to engage a distal vertebral body in the motion segment outside the distal bone anchor;
A pivot including a distal end, a proximal end, and an intermediate portion therebetween,
A distal pivot cup, an exterior corresponding to a portion of the cavity within the distal bone anchor, and a proximal of the distal pivot cup for receiving the distal end of the pivot Including a cavity at the end;
A proximal bone anchor, and the proximal bone anchor penetrates the interior of the proximal bone anchor from the distal end, the proximal end, and from the distal end to the proximal end, and accommodates a corresponding driver head And a set of threads external to the proximal bone anchor and configured to engage the proximal vertebral body of the motion segment;
A proximal pivot cup, the proximal pivot cup including a distal end, a proximal end, and a cavity at the distal end of the proximal pivot cup for receiving the proximal end of the pivot; A spinal motion retention assembly, characterized by:   42. The spinal motion retention assembly of claim 41, wherein the distal pivot cup has a set of external threads corresponding to a set of internal threads in at least a portion of the interior cavity of the distal bone anchor. A spinal motion retention assembly suitable for use in a spinal motion segment comprising:
A distal bone anchor, and the distal bone anchor is located within the distal bone anchor accessible from the distal end, proximal end, and proximal end, suitable for accommodating a corresponding driver head A cavity configured to receive the distal end of the pivot and functioning as a support surface for the distal end of the pivot, and external to the distal bone anchor, the distal vertebral body of the motion segment A set of threads configured to engage the
A pivot including a distal end, a proximal end, and an intermediate portion therebetween,
A proximal bone anchor, the proximal bone anchor extending through the interior of the proximal bone anchor from the distal end, the proximal end, and from the distal end to the proximal end; Including a cavity suitable for containment and a set of threads external to the proximal bone anchor and configured to engage the proximal vertebral body of the motion segment;
A proximal pivot cup, the proximal pivot cup including a distal end, a proximal end, and a cavity at the distal end of the proximal pivot cup for receiving the proximal end of the pivot; ,
A spinal motion retention assembly comprising: at least one component positioned between the distal bone anchor and the proximal bone anchor and elastically deformable upon compression. A spinal motion stabilization assembly for imparting dynamic stabilization to motion segments within the spine, comprising:
A distal implantation device assembly;
A proximal implantation device assembly;
Contacting the distal implantation device assembly through an unconstrained pivot contact with a support surface in the distal implantation device assembly and the proximal implantation device assembly through an unconstrained pivot contact with a support surface in the proximal implantation device assembly Dual pivot in contact with,
A spinal motion stabilization assembly including an artificial nucleus pulposus surrounding at least a portion of the dual pivot.   A spinal motion segment having an implanted spinal motion stabilization assembly moves in flexion, extension, lateral bending to the right, lateral bending to the left, clockwise rotation and counterclockwise rotation 45. The spinal motion stabilization assembly of claim 44, wherein:   A motion segment having an implanted spinal motion stabilization assembly has a flexion of about 12 °, an extension of about 8 °, a lateral bending to the right of about 9 °, a lateral bending of about 9 ° to the left, and about 2 °. 46. The spinal motion stabilization assembly of claim 45, wherein the spinal motion stabilization assembly is capable of motion with a clockwise axial rotation and a counterclockwise axial rotation of about 2 °.   The motion segment includes an upper vertebral body and a lower vertebral body, the upper vertebral body being capable of translating relative to the lower vertebral body in an anterior / posterior direction, a right lateral / left lateral direction, and 45. The spinal motion stabilization assembly of claim 44, wherein the spinal motion stabilization assembly is capable of translation resulting from elastic deformation and elastic recovery of at least one component of the spinal motion stabilization assembly.   The proximal implantation device assembly is configured to move a support surface within the proximal implantation device assembly toward the distal implantation device assembly in response to torque applied during assembly of the spinal motion stabilization assembly. A) of the load between the A nucleus prosthesis and the annulus and B) the male screw on the proximal implant device assembly engaged with the proximal vertebral body and the male screw and distal vertebral body on the distal device assembly 45. The spinal motion stabilization assembly of claim 44, wherein the dispersion is selectively altered. A method of placing a spinal motion retention assembly in a motion segment accessed by an axial transsacral approach, wherein the implanted spinal motion retention assembly includes a distal component and a proximal component, both having external threads; An implantation subassembly including a pivot extending between the distal component and the proximal component and suitable for unconstrained engagement by the distal component and a dual pivot end within the proximal component; An expandable membrane that is expanded by an artificial nucleus pulposus material,
Locating the distal component and the proximal component simultaneously, engaging the distal component with a distal vertebral body, and engaging the proximal component with a proximal vertebral body simultaneously with the distal component Rotating a screwdriver that maintains a predetermined separation distance between the component and the proximal component and does not cross thread the thread path cut into the proximal vertebral body;
Inserting the distal end of the pivot into the proximal end of the distal implantation device assembly;
Selectively advancing a portion of the proximal implant device assembly and pressing the pivot against the distal implant device assembly; A) an artificial nucleus pulposus and B) an external screw on the proximal component and the distal Changing the distribution of load between male threads on the component.   50. The method of claim 49, further comprising engaging the distal component with at least one component configured to elastically deform under a compressive load.   50. The method of claim 49, further comprising engaging the proximal component with at least one component configured to elastically deform under a compressive load.   52. The method of claim 51, further comprising engaging the distal component with at least one component adapted to elastically deform under a compressive load. A method of providing dynamic stabilization to a motion segment in the spine, comprising:
A spinal motion stabilization assembly having a pair of unconstrained pivot points and at least one elastically deformable component is disposed on the motion segment by an axial channel formed by a transsacral approach, the motion segment having the spine A method comprising allowing after receiving a motion stabilization assembly to undergo a motion that allows a normal range of motion in all six degrees of freedom. Expanding a membrane bonded to the spinal motion stabilization assembly with an artificial nucleus pulposus material to form an artificial nucleus pulposus;
Selectively varying the load between the prosthetic nucleus and a set of threads on the spinal motion stabilization assembly engaged with vertebral bodies at the upper and lower ends of the motion segment. 53. The method according to 53.   55. The method of claim 54, wherein prosthetic nucleus material is provided to the membrane via the distractor / injector tool after distraction of the motion segment and prior to removal of the distractor / injector tool.

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