Interspinous implants and methods

The present invention provides spinous process implant and associated methods. In one aspect of the invention the implant limits the maximum spacing between the spinous processes. In another aspect of the invention, a spacer has at least one transverse opening to facilitate tissue in-growth. In another aspect of the invention, an implant includes a spacer and separate extensions engageable with the spacer. The spacer is provided in a variety of lengths and superior to inferior surface spacings. In another aspect of the invention, an implant includes a spacer and a cerclage element offset from the midline of the spacer in use so that the spacer defines a fulcrum and the cerclage element is operative to impart a moment to the vertebrae about the spacer. In another aspect of the invention, instrumentation for inserting the implant is provided. In other aspects of the invention, methods for treating spine disease are provided.

FIELD

The present disclosure relates to spinous process implants and associated instruments and methods.

BACKGROUND

The vertebrae of the human spine are arranged in a column with one vertebra on top of the next. An intervertebral disc lies between adjacent vertebrae to transmit force between the adjacent vertebrae and provide a cushion between them. The discs allow the spine to flex and twist. With age, spinal discs begin to break down, or degenerate resulting in the loss of fluid in the discs, and consequently, the discs become less flexible. Likewise, the discs become thinner allowing the vertebrae to move closer together. Degeneration also may result in tears or cracks in the outer layer, nr annulus, of the disc. The disc may begin to bulge outwardly. In more severe cases, the inner material of the disc, or nucleus, may actually extrude out of the disc. In addition to degenerative changes in the disc, the spine may undergo changes due to trauma from automobile accidents, falls, heavy lifting, and other activities. Furthermore, in a process known as spinal stenosis, the spinal canal narrows due to excessive bone growth, thickening of tissue in the canal (such as ligament), or both. In all of these conditions, the spaces through which the spinal cord and the spinal nerve roots pass may become narrowed leading to pressure on the nerve tissue which can cause pain, numbness, weakness, or even paralysis in various parts of the body. Finally, the facet joints between adjacent vertebrae may degenerate and cause localized and/or radiating pain. All of the above conditions, as well as others not specifically mentioned, are collectively referred to herein as spine disease.

Conventionally, surgeons treat spine disease by attempting to restore the normal spacing between adjacent vertebrae. This may be sufficient to relieve pressure from affected nerve tissue. However, it is often necessary to surgically remove disc material, bone, or other tissues that impinge on the nerve tissue and/or to deride the facet joints. Most often, the restoration of vertebral spacing is accomplished by inserting a rigid spacer made of bone, metal, or plastic into the disc space between the adjacent vertebrae and allowing the vertebrae to grow together, or fuse, into a single piece of bone. The vertebrae are typically stabilized during this fusion process with the use of bone plates and/or pedicle screws fastened to the adjacent vertebrae.

Although techniques for placing intervertebral spacers, plates, and pedicle screw fixation systems have become less invasive in recent years, they still require the placement of hardware deep within the surgical site adjacent to the spine. Recovery from such surgery can require several days of hospitalization and long, slow rehabilitation to normal activity levels.

More recently, investigators have promoted the use of motion preservation implants and techniques in which adjacent vertebrae are permitted to move relative to one another. One such implant that has met with only limited success is the artificial disc implant. These typically include either a flexible material or a two-piece articulating joint inserted in the disc space. Another such implant is the spinous process spacer which is inserted between the posteriorly extending spinous processes of adjacent vertebrae to act as an extension stop and to maintain a minimum spacing between the spinous processes when the spine is in extension. The spinous process spacer allows the adjacent spinous processes to move apart as the spine is flexed.

DESCRIPTION OF THE ILLUSTRATIVE EXAMPLES

Embodiments of spinous process implants according to the present invention include a spacer and an extension extending outwardly from the spacer. The extension is sometimes described as being one or more lobes associated with the spacer. The spinous process implant may be configured for insertion between adjacent spinous processes of the cervical, thoracic, and/or lumbar spine. The spacer may be provided in a variety of sizes to accommodate anatomical variation amongst patients and varying degrees of space correction. The spacer may include openings to facilitate tissue in-growth to anchor the spacer to the vertebral bodies such as tissue in-growth from the spinous processes. The spacer may be configured for tissue in-growth from superior and inferior spinous processes to cause fusion of the adjacent spinous processes. The openings may be relatively large and/or communicate to a hollow interior of the spacer. A hollow interior may be configured to receive bone growth promoting substances such as by packing the substances into the hollow interior. The openings may be relatively small and/or comprise pores or interconnecting pores over at least a portion of the spacer surface. The openings may be filled with bone growth promoting substances.

The spacer may have any suitable cross-sectional shape. For example, it may be cylindrical, D-shaped, C-shaped, H-shaped, include separated cantilevered beams, and/or any other suitable shape. The shape may include chamfers, fillets, flats, relief cuts, and/or other features to accommodate anatomical features such as for example the lamina and/or facets.

The extension may extend transversely from the spacer relative to a spacer longitudinal axis to maintain the spacer between adjacent spinous processes. A single extension may extend in one or more directions or multiple extensions may be provided that extend in multiple directions. One or more extensions may be adjustable longitudinally relative to one another and/or the spacer to allow the extensions to be positioned laterally relative to the spinous processes. A moveable extension may be provided that is movable axially relative to the spacer and another extension. Alternatively, a plurality of moveable extensions may be provided. For example, the extensions may clamp against the sides of the spinous processes to immobilize the spinous processes relative to one another and promote fusion between the adjacent vertebrae. The extensions may include fasteners engageable with the spinous processes. The fasteners may include sutures, wires, pins, straps, clamps, spikes, screws, teeth, adhesives, and/or other suitable fasteners. The fasteners may be integrated into the extensions or they may be modular. Modular fasteners may be adjustable, replaceable, and/or removable to allow tailoring of the kind and quality of fixation from rigid fixation to no fixation. The spacer, extensions, and/or fasteners may advantageously be made of different materials. For example, the spacer and extensions may be made of a relatively softer material while the fasteners may be made of a relatively harder material. For example, the spacer and/or extension may be made of a polymer and/or other relatively soft material and the fastener may be made of a metal and/or other relatively hard material.

Cerclage may be used to stabilize the spinous process implant and/or to provide other benefits. For example, wires, straps, bands, cables, cords, and/or other elongated members may encircle the pedicles, lamina, spinous processes, transverse processes, and/or other spinal structures. The cerclage may be relatively inextensible to provide a hard check to spine flexion or the cerclage may be relatively extensible to provide increasing resistance to flexion. The cerclage may be relatively flexible and trappable such as a woven fabric or it may be relatively rigid such as a metal band. The cerclage may have shape memory properties that cause it to resume a prior set shape after implantation. The cerclage may be independent of the spinous process implant or may engage it. For example, the cerclage may pass through a hollow interior of the spinous process implant and/or engage the extension. The cerclage may be offset from the spacer and provide a tensioning force that uses the spacer as a fulcrum to offload the disc and/or open the disc space.

The implant may be supplemented with bone growth promoting substances to facilitate fusion of adjacent vertebrae between spinous processes, lamina, transverse processes, facets, and/or other spinal structures. The bone growth promoting substances may be spaced from the implant, placed adjacent the implant, sandwiched between the implant and underlying bone, placed inside the implant, coated onto the implant, and/or otherwise placed relative to the implant. If it is coated onto the implant it may cover the entire implant or only selected portions of the implant such as the extensions, fasteners, spinous process contacting portions of the spacer, and/or other portions.

As used herein, bone growth promoting substances may include bone paste, bone chips, bone strips, structural bone grafts, platelet derived growth factors, bone marrow aspirate, stem cells, bone growth proteins, bone growth peptides, bone attachment proteins, bone attachment peptides, hydroxylapatite, calcium phosphate, other suitable bone growth promoting substances, and/or combinations thereof.

The spinous process implant may be used to treat spine disease in a variety of surgical techniques including superspinous ligament sacrificing posterior approaches, superspinous ligament preserving posterior approaches, lateral approaches, and/or other suitable approaches. The spinous process implant may be used to treat spine disease by fusing adjacent vertebrae or by preserving motion between adjacent vertebrae. It may include only an extension stop such as a spacer, only a flexion stop such as flexible cerclage elements, or both a flexion and extension stop, such as spinous process fasteners. The spinous process implant may be used to reduce loads on the facet joints, increase spinous process spacing, reduce loads on the disc, increase anterior disc spacing, and/or otherwise treat spine disease. Anterior effects may be accomplished by tensioning spine elements posterior to the spacer to apply a mechanical advantage to the spinal construct. Techniques for the spinal process implant may include leaving the tissues at the surgical site unmodified or modifying tissues such as trimming, rasping, roughening, and/or otherwise modifying tissues at the implant site.

The spinous process implant may have a dimension in a first direction that is less than a dimension in a second direction to aid in inserting the spinous process implant between adjacent spinous processes. For example, the spinous process implant may have a longitudinal axis and a leading end near one end of the longitudinal axis. The leading end may have a first dimension transverse to the longitudinal axis that is less than a second dimension transverse to the longitudinal axis such that the spinous process implant may be oriented with the first dimension aligned with the space between adjacent spinous processes to ease insertion and then oriented with the second dimension aligned with the spinous processes to space them apart a distance equal to the second dimension.

Insertion of spinous process implants may be facilitated by a set of instruments alternately engageable with one another to increase the interspinous space and engageable with a spinous process implant to help maneuver it between adjacent spinous processes.

Insertion of spinous process implants may be facilitated by an introducer insertable between adjacent spinous processes and able to engage a spinous process implant to help maneuver it between the adjacent spinous processes. The introducer may be rigid, flexible, or include both rigid and flexible portions. The introducer may engage the inside and/or the outside of the spinous process implant. The introducer may engage a relatively small portion or a relatively large portion of the spinous process implant. For example, the introducer may include a sleeve and/or trocar engageable with the inside or outside of the spinous process implant in nesting relationship. For example, a rigid sleeve may be positioned between adjacent spinous processes and then receive a spinous process implant such that when the sleeve is withdrawn the implant remains between the spinous processes. Such a sleeve may be initially inserted by installing a trocar in the sleeve. The introducer may include a flexible leader that is threadable between adjacent spinous processes to then draw the introducer and/or spinous process implant between the spinous processes. For example the introducer may include a sleeve with a relatively small diameter flexible leader extending from a first end and may be engageable with a spinous process implant at a second end such that it may be assembled with a spinous process implant and then the assembly drawn between the spinous processes by pulling on the leader. Alternatively, the introducer may be drawn between the spinous processes and then joined with the implant. The sleeve may be flexible to resiliently couple to the spinous process implant such as by compressing inside of the implant and/or stretching around the outside of the implant. The introducer may be solid or hollow. It may be rigid or flexible. It may be made of metal, plastic, and/or other suitable materials. The introducer may loosely engage the spinous process implant, as in a sliding relationship, or it may engage the spinous process implant such that the implant is constrained to move with the introducer. The introducer may engage the spinous process implant via a friction fit or a positive engagement.

FIGS. 1 and 2depict posterior and lateral views of a pair of adjacent vertebrae of the lumbar spine10. A superior vertebra12is separated from an inferior vertebra14by a disc16. Each vertebra includes a pair of transverse processes18,19, a posteriorly projecting spinous process20,21, and a pair of lamina22,23connecting the transverse processes18,19to the spinous process20,21. In addition to the connection through the disc16, the vertebrae12,14articulate at a pair of facet joints24.

FIGS. 1-9illustrate an exemplary spinous process implant100. The implant100includes a spacer102positioned between the spinous processes20,21. The geometry of the implant100is illustrated with the use of axes that define length (l), height (h), and width (w) directions for the spacer. When implant100is implanted in a patient, the height direction of the spacer102is generally oriented along the superior/inferior direction of the patient's anatomy, the width direction of the spacer102is generally oriented along the anterior/posterior direction of the patient's anatomy, and the length direction of the spacer102is generally oriented along the lateral/medial direction of the patient's anatomy.

The height104(FIG. 1) of lacer102limits how closely the spinous processes20,21can move together. Thus, the spacer102maintains a minimum distance between the spinous processes20,21. In the case of spine disease involving posterior subsidence of the adjacent vertebra, insertion of the spacer102between the spinous processes20,21will move the vertebrae apart and relieve pressure on nerve tissue and the facet joints24.

As shown inFIG. 3, the spacer102includes a first end106, a second end108, and a longitudinal axis110extending from the first end to the second end. The spacer102has a sidewall112, generally parallel to the longitudinal axis110, including superior and inferior outer surfaces114,116. Transverse openings118(see alsoFIG. 6) communicate from the superior and inferior outer surfaces114,116inwardly to facilitate tissue in-growth. The exemplary spacer102includes a hollow interior120bounded by an inner surface122such that the openings118communicate from the outer surfaces114,116to the hollow interior120. Bone growth promoting substances124are shown packed into the hollow interior120inFIGS. 1 and 2to promote fusion of the vertebrae12,14by bone growth between the spinous processes20,21.

The spinous process implant100further includes a first extension126projecting outwardly from the spacer102along the spacer height direction h and transversely to the longitudinal axis110to lie generally alongside the superior and inferior spinous processes20,21. Abutment of the first extension126with the spinous processes20,21helps prevent lateral movement of spacer102, thereby maintaining spacer102between the spinous processes20,21. In the exemplary spinous process implant100, the first extension126is fixed relative to the spacer102and the implant includes a second extension128mountable to the spacer for axial movement relative to the first extension126. The second extension128may be moved toward the first extension126to approximate the width of the spinous processes20,21and better stabilize the implant100. It is fixed in place by tightening a set screw130(FIG. 3) against the spacer102. The extensions126,128include fasteners132,134,136projecting from the extensions126,128to engage the spinous processes20,21to fix the spacer102to the spinous processes20,21.FIG. 1depicts additional bone growth promoting substance in the form of strips of bone125sandwiched between the extensions126,128along the sides of the spinous processes20,21to promote bone growth along the sides of the spinous processes to further enhance fusion of the vertebrae12,14. The extensions126,128preferably extend inferiorly as well as superiorly from spacer102to optionally attach to the inferior spinous processes to immobilize the spinous processes20,21relative to one another while fusion takes place.

Fasteners132,134, and136may take any suitable form. They may be made integral with the extensions126,128such as by machining or casting them with the extensions or they may be formed separately and permanently attached to the extensions126,128. Fastener132is a sharpened spike that threadably engages the extension126. The threaded engagement allows the fastener132to be replaced with a different fastener132. For example, the fastener132may be replaced by one that has a different shape, a different size, a different material, or a different surface coating. The threaded engagement also allows the fastener132to be adjusted to extend by varying amounts from the extension126to vary how it engages the bone. Thus, the fastener132can be adjusted to fit differently shaped bones or to penetrate into a bone by varying amounts. For example, multiple threaded fasteners132can be adjusted to extend by different amounts to conform to curved or angled bone. Finally, the threaded engagement allows the user to remove the fastener132when fixation is not desired such as when it is desired to use implant100in a non-fusion procedure as an extension stop without limiting flexion.

As best seen inFIG. 3, fasteners134and136are provided as multi-spike pods allowing a plurality of spikes to be quickly adjusted, changed, or omitted. Fastener134includes a non-circular tab138engageable with a non-circular opening140in the extension126. The non-circular engagement prevents the fastener134from rotating. The tab138may form a press-fit, snap-fit, or other suitable engagement with the opening140. The tab138may be further secured by a supplemental screw142. Fastener136includes a threaded shaft144threadably engaged with a base member146to allow the length of the fastener136to be adjusted. The shaft144engages the extension126in a rotating and pivoting manner such that the fastener136can be adjusted rotationally and angularly to engage the bone surface. In the illustrative embodiment, the shaft144terminates in a spherical ball148that engages the opening140in a ball-and-socket arrangement for three degrees of freedom. However, any mechanism that allows any number of degrees of freedom may be used. The fastener136may be allowed to move in use so that as the extension126is pressed toward a bone, the fastener136adjusts to the angle of the bone surface. The fastener136also may be secured such as by screw142to adjust the tension in the joint and/or to lock the fastener136in a predetermined orientation.

FIG. 4illustrates the axial relationship of fasteners on the opposing extensions126,128. In the illustrative implant100, the fasteners132at the top of the implant100are shown aligned along a common axis150that is substantially perpendicular to extensions126and128. The fasteners134at the bottom of the implant100are shown offset so that they can interleave if necessary as they are pressed into a bone. Any combination of fastener type, number, and alignment may be provided on the implant100.

As seen inFIGS. 5 and 6, the ends106,108of the spacer102include anterior chamfers152. These chamfers152allow the ends106,108to clear posteriorly facing structures of the vertebrae12,14such as the facet joints24. Also, as seen inFIGS. 5 and 6, the spacer102is offset anteriorly (in the spacer width direction w) relative to the extensions126,128such that the longitudinal axis110of the spacer102is anterior of a midline plane154(FIGS. 6,8) of the extensions126,128. The anterior offset of the spacer102allows it to fit deeply between the spinous processes20,21while the extensions126,128fit alongside the spinous processes20,21.

As best seen inFIGS. 3 and 8, the second extension128defines an aperture155conforming generally to the cross-sectional shape of the spacer102. In the illustrative embodiment ofFIGS. 1-9, the aperture155opens anteriorly to form a “C”-shape. Tabs156extend inwardly from the superior and inferior portions of the aperture to slidingly engage elongated slots158in the superior and inferior surfaces of the spacer102. The second extension128can be translated longitudinally along the spacer length l toward and away from the first extension126. Tightening the set screw130against the posterior side160of the spacer102forces the tabs156posteriorly against the sides of the slots158and locks the second extension128in place longitudinally. The posterior side160of the spacer102may be roughened as shown to better grip the set screw130. The set screw130may also dig into the surface of the spacer102upon tightening to positively grip the spacer102. The aperture155(FIGS. 3,8) may conform closely to the spacer102to constrain the second extension128to generally parallel motion relative to the first extension126. Alternatively, the aperture155may be larger than the spacer102by a predetermined amount to permit a predetermined amount of angular adjustment of the second extension128relative to the first extension126as shown inFIG. 7to allow the extension128to adjust to the underlying bone surface.

As best seen inFIG. 8, the second extension128includes a first inferior lobe161having a first lobe centerline162and a second superior lobe164having a second lobe centerline166. In the illustrative embodiment, the first lobe centerline162and the second lobe centerline166are parallel and spaced apart so that the second extension128has a generally “Z”-shaped plan form. This shape allows the extension of one implant100to interleave, if necessary, with another implant100in a multilevel surgery (as shown inFIG. 9) to permit close spacing of the implants, and/or longer extension lobes for more extensive bone engagement. In addition, first inferior lobe161has a semi-circular convex shape that is generally complementary to a semi-circular superior concave surface165formed adjacent second superior lobe164. Similarly, second superior lobe164has a semi-circular convex shape that is generally complementary in shape to a semi-circular inferior concave surface163formed adjacent first inferior lobe161. As indicated inFIG. 8, first inferior lobe161is adjacent to inferior concave surface163, and extension midline plane154is located between first inferior lobe161and inferior concave surface163. Second superior lobe164is adjacent superior concave surface165, and extension midline plane154is located between second superior lobe164and superior concave surface165. Moreover, first inferior lobe radius r1is substantially equal to superior concave surface radius r4, while second superior lobe radius r3is substantially equal to inferior concave surface radius r2. As a result, when two implants are placed on adjacent spinal levels, the first inferior lobe161of the upper implant may be (but need not be, depending on what is medically indicated) interfitted into the superior concave surface165of the inferior implant. In addition, the second superior lobe164of the inferior implant may be interfitted into the inferior concave surface163of the superior implant. In the illustrative example ofFIGS. 1-9, first inferior lobe161and second superior lobe164form a unitary second extension128. Although not separately depicted, first extension126also has complementary lobes that are similarly configured and oriented relative to one another.

As shown inFIG. 9, multiple spinous process implants100may be placed on adjacent levels of the spine. As illustrated in the figure, a first superior implant100is positioned with its spacer102between a first superior spinous process and a second intermediate spinous process, while a second inferior implant100is positioned with its spacer102between the second intermediate spinous process and a third inferior spinous process. The first extensions126of the superior and inferior implants are located on a first side of the patient's sagittal plane, while the second extensions128of the superior and inferior implants are located on a second side of the patient's sagittal plane.

In the illustrative embodiment ofFIGS. 1-9, the extension lobe centerlines162,166are offset equidistantly from the midline plane154of the second extension128. Although not separately shown, the first extension126is configured similarly. The centerlines162,166may vary from parallel and they may be offset asymmetrically to form different shapes to accommodate different vertebral anatomy. For example, the shape may be tailored for different portions of the spine10. In the illustrative embodiment ofFIGS. 1-9, the first extension126has the same shape as the second extension128. However, the shape may be varied between the first and second extensions126,128.

FIG. 10depicts an implant200having a spacer202and first and second extensions204,206. The spacer202includes pores208to allow tissue to grow. The pores208may be individual openings spaced from one another, interconnecting openings, or combinations of individual and interconnecting openings. The spacer202may be a monolithic block having uniform porosity throughout. Alternatively, the spacer202may include an outer porous layer210and an inner layer212of different composition. For example, the inner layer212may be solid, porous, hollow, or some other configuration. A porous inner layer may have pores of a different size and/or distribution than the outer layer210. Similarly, any porous portion may have uniform porosity or porosity that varies in pore size or density. A variety of pore configurations are suitable. Preferably the pore size is in the range of from about 1 μm to about 2 mm. More preferably, the pore size is in the range of from about 1 μm to about 500 μm. Still more preferably, the pore size is in the range of from about 75 μm to about 300 μm. The pores may be produced by a variety of processes such as sintering of particles; leaching a soluble component from the material; matting, weaving, or otherwise combining fibers; and/or by any other known process. The pore size may be tailored to preferentially promote hard tissue growth, soft tissue growth, or a combination of hard and soft tissue growth. The extensions204,206may be solid or they may have large and/or small openings to encourage bone growth in and/or around the extensions204,206. The spacer202and/or extensions204,206also may be coated as previously described.

The extensions204,206may be fixed and/or adjustable. In the illustrative implant200ofFIG. 10, the first extension204is fixed to one end of the spacer202and the second extension206is translatable along the length of spacer202to allow the extensions to be placed adjacent the spinous processes. The extensions204,206are shown with optional fasteners, e.g., spikes214that may engage the spinous processes20,21to fix the spinous processes20,21relative to one another.

FIG. 10also depicts the use of cerclage in conjunction with the implant200. For example, one or more flexible bands216are placed around the lamina22,23to provide a flexion stop. The band216may help carry the load exerted on the spikes214during spine flexion. Alternatively or in addition to the band216, one or more bands218,220may be placed around the transverse processes18,19.

FIGS. 11-13depict additional examples of the use of cerclage in conjunction with a spinous process implant300according to the present disclosure. The implant includes a spacer302for placement between adjacent spinous processes20,21and an extension304. In the example ofFIG. 11, a band310of flexible material is looped around the spinous processes20,21. By placing the band310behind the areas312,314where the spinous processes contact the spacer302an offset318is created. Tightening of the band310creates a moment320,322on each vertebra12,14that offloads some of the pressure on the disc16between the adjacent vertebrae12,14. With increased tightening of the band310, the anterior spacing324of the vertebrae12,14may actually be increased. Thus, by using the spinous process implant300in combination with the band310, the vertebrae12,14may be levered apart with the implant300being used as the fulcrum. In addition to the advantages already mentioned, this combination produces an anterior disc space effect with a posterior spinous process procedure that is less invasive than typical disc spacing procedures.

In the examples ofFIGS. 12 and 13, the implant300includes a mechanism for attaching the cerclage band310to the implant300. In the example ofFIG. 12, the mechanism includes openings330,332in the superior and inferior ends of the extension304. By attaching the band310to the extension304, the band310and extension304help stabilize one another against anterior-posterior displacement. This attachment also helps position the band310at a predetermined offset318from the spacer302. In the example ofFIG. 13, the band310is looped through a hollow interior of the spacer302itself. In this example, the band is not offset and produces minimal or no moment on the vertebrae.

FIGS. 14-24illustrate alternative mechanisms for attaching a movable extension to the implant ofFIG. 1. Referring toFIG. 14, an implant400includes a spacer402, a first extension404and a second, movable extension406. The movable extension406includes a body in the form of a ring408with an inner surface410generally conforming to the outer surface of the spacer402so that the ring is slidingly receivable on the spacer402. A set screw412is tightened against the spacer402to fix the movable extension406at a desired position on the spacer402. Tightening of the set screw412biases the movable extension406posteriorly relative to the spacer402. The anterior portion414of the ring presses against the anterior portion416of the spacer402to counter this posterior bias and allow the set screw412to lock the movable extension406. The spacer402may include a plurality of indentations418to create a positive engagement with the set screw412at predetermined axial locations. The ring408may be sized to permit a predetermined amount of tilting of the movable extension406relative to the spacer402.

Referring toFIG. 15, an implant500includes a spacer502, a first extension504, and a second, movable extension506. The spacer502includes a plurality of cantilevered beams508,510projecting parallel to a longitudinal axis512away from the first extension504. In the example ofFIG. 15, the spacer502includes a pair of opposed “C”-shaped beams508,510with their concave surfaces facing inwardly. The spacer502includes openings514through the beams508,510and defines elongated openings516,518anteriorly and posteriorly between the beams. The movable extension506includes a body in the form of an interrupted ring520. The ring520is open anteriorly and the margins of the opening define posteriorly directed hooks522,524. The inner surface526of the ring conforms generally to the outer surface of the beams508,510so that the ring is slidingly receivable on the spacer502. The open anterior configuration of the ring520provides clearance to ease sliding of the ring in-vivo. A set screw528is tightened against the spacer502to fix the movable extension506at a desired longitudinal position on the spacer. The hooks522,524curve around a portion of the anterior edge of the beams508,510to resist posterior translation of the ring relative to the spacer502when the set screw528is tightened.

Referring toFIG. 16, an implant600is depicted that is similar to implant500ofFIG. 15having a spacer602, first extension604, and movable extension606. However, the ring608is truncated anteriorly to provide even more anterior clearance than the ring520ofFIG. 15. The ring608includes a key610projecting anteriorly from the posterior side of the ring608and expanding superiorly and inferiorly to engage the inner surface612of the beams614,616to resist posterior translation of the ring relative to the spacer602. The key610also partially blocks the hollow interior618of the spacer602to help retain material optionally packed into the interior618.

Referring toFIG. 17, an implant700includes a spacer702, a first extension704, and a second movable extension706. The spacer702includes a sidewall708defining an outer surface710and an inner surface712. In the example ofFIG. 17, the spacer702is generally in the shape of a hollow flattened cylinder with a “D”-shaped cross section. However, the spacer702could be any desirable shape. The spacer702includes a plurality of openings714communicating from the outer surface710to the inner surface712. The movable extension706includes a projection716configured generally like the spacer702but being sized to slide within the spacer702in telescoping relationship. The projection (or the spacer) may optionally include one or more fixation mechanisms to lock the extensions704,706at a desired longitudinal spacing. Fixation mechanisms may include a set screw718, a ridge720forming a snap fit with a groove722or other feature, a detent724engageable with openings714, and/or other suitable fixation mechanisms. Any one or combinations of these mechanisms may be used and they may be reversed from the orientation shown.

Referring toFIGS. 18-20, an implant800includes a spacer802, a first extension804, and a second, movable extension806. The spacer802includes a plurality of cantilevered beams similar toFIGS. 15 and 16except that in this example there are three beams808,810,812. The beams project parallel to a longitudinal axis814away from the first extension804. In the example ofFIG. 18, the anterior beam812includes a posteriorly opening groove816. The posterior beams808,810and anterior beam812define an elongated slot818between them opening superiorly and inferiorly. The posterior beams808,810further define an elongated slot820between them opening posteriorly.FIG. 20illustrates a cruciform opening822defined by the projection of the groove816and slots818,820projected through the first extension804. The movable extension806includes a body824sized to slidingly engage the slot818. An optional lug826can project anteriorly into groove816to constrain tilting of the movable extension806relative to the first extension804. The lug826can be sized to fit closely within groove816to prevent tilting of the movable extension806or it can be sized smaller than the groove816to permit a predetermined amount of tilt. A set screw828is provided to lock the movable extension806to the spacer802.

Referring toFIG. 21, an implant900is depicted that is configured generally like that ofFIG. 16. However, an end wall902adjacent the first extension904includes a through bore906and the movable extension908includes a key910with a through bore912. The bores906,912receive a fastener to fix the extensions904,908at a maximum spacing to prevent them from moving apart. Fasteners may include screws, bolts, nuts, cables, wires, ties, rods, and/or any other suitable fastener. In the example ofFIG. 21, the fastener includes an elongated crimp receiving member914, such as a cable, and crimp members916,918, such as ferrules or compressible beads.

Referring toFIG. 22, an implant1000includes a spacer1002, a first extension1004, and a second extension1006. The spacer1002includes an outer surface1008defining one or more longitudinal grooves1010extending along the outer surface1008and through the first extension1004. The first extension1004includes one or more corresponding slots1012having a radially outwardly extending portion1014through the first extension1004and communicating with the grooves1010. The slots1012have a radially inwardly extending portion1016defining a shoulder1018at the end of the grooves1010. The second extension1006includes one or more corresponding projections1020projecting longitudinally toward the first extension1004and terminating at a radially inwardly directed tab1022. The second extension1006further includes a centering bore1024having a conical opening engageable with a conical free end1026of the spacer1002. The second extension1006is attached to the spacer1002by pressing the tabs1022against the conical end1026of the spacer1002to deflect and spread the projections outwardly until the tabs1022engage the grooves1010. The tabs1022are slid along the grooves1010until they exit through the slots1012and the tabs1022snap inwardly over the shoulders1018and into the portions1016. Abutment of the tabs1022against the shoulders1018prevents the first and second extensions1004,1006from moving apart. The engagement of the conical end1026of the spacer1002with the bore1024provides radial stability to the assembly.

Referring toFIG. 23, an implant1100includes a spacer1102, a first extension1104, and a second extension1106. The spacer1102includes a transverse groove1108with a central boss1110having an enlarged head1112. The second extension1106includes a portion1114sized to fit within the groove1108and an opening1116bordered by one or more angled tabs1118. The second extension1106is assembled to the spacer by pressing the portion1114into the groove1108with the central boss1110directed into the opening1116. As the central boss1110is pressed through the opening1116, the tabs1118flex outwardly to allow central boss1110to pass. Once the central boss1110is past the tabs1118, the tabs1118move to return to their original position and snap behind the enlarged head1112. In this configuration, the central boss1110retains the second extension1106longitudinally and the groove1108prevents the second extension1106from rotating about the longitudinal axis of the implant1100.

Referring toFIG. 24, an implant1200includes a spacer1202, a first extension1204, and a second extension1206. The spacer1202includes a solid cylindrical sidewall1208defining a hollow interior1210. The extensions1204,1206are similarly configured and each includes a projection1212,1214sized to fit inside of the spacer1202. The extensions1204,1206may attach to the spacer by press-fitting, snap-fitting, screwing, and/or otherwise engaging the projections1212,1214with the spacer1202. Alternatively, or additionally, the extensions1204,1206may attach to the spacer1202with any of the previously depicted attachment mechanisms such as with a setscrew as shown inFIG. 3or an elongated fastener as shown inFIG. 21. In the example ofFIG. 24, the extensions1204,1206are slotted longitudinally to form flexible petals1216that press into the spacer1202. The extensions1204,1206include openings1218to allow tissue growth, permit attachment of cerclage members, and/or receive additional fasteners attached to the spinous processes.

The spacer1202ofFIG. 24could have openings as shown in some of the other examples. Likewise, the other examples could have a solid surface as shown inFIG. 24. Similarly the extensions of any of the examples may be solid, have openings, or be otherwise advantageously configured.

Implants according to the present invention may be implanted using a variety of surgical approaches and techniques. Surgical approaches may include superspinous ligament sacrificing posterior approaches, superspinous ligament preserving posterior approaches, lateral approaches, and/or other suitable approaches. Techniques may include leaving the tissues at the surgical site unmodified or modifying the tissues such as trimming, rasping, roughening, and/or otherwise modifying them. For example, inFIG. 1, a lateral approach is used and the inferior spinous process is cut on its superior surface26to enlarge the interspinous space to receive the implant100. After the interspinous space is prepared, the spacer102is inserted into the interspinous space. If a first extension126is present it may be pressed inwardly to lie near or abut one or more spinous processes. If a second extension128is used, it is engaged with the spacer102and also optionally pressed inwardly. InFIG. 1, opposing extensions126,128having inwardly directed bone fasteners have been used and pressed inwardly so that the fasteners132engage the spinous processes20,21. The engagement of the fasteners132with the inferior spinous process21is not shown inFIG. 1.

Referring toFIGS. 25A-29a spinous process implant1250similar to that ofFIG. 1includes a spacer1252having a first end1254, a second end1256, and a longitudinal axis1258extending from the first end1254to the second end1256along the spacer length direction1. The spacer has a generally curved sidewall1259with a length that is generally parallel to the implant longitudinal axis1258. Generally curved sidewall1259is separated along at least a portion of its length by a superior slot1264a1and an inferior slot1264a2to define first sidewall1261aand second sidewall1261b. Sidewall1259includes superior and inferior outer surfaces1260,1262. Slots1264a1,1264a2and transverse openings1264b,1264c, and1264d(FIG. 27) communicate from the superior and inferior outer surfaces1260,1262inwardly to facilitate tissue growth. In certain exemplary embodiments, opening1264bis not provided on second anterior sidewall1261b. The exemplary spacer1252includes a hollow interior1266bounded by an inner surface1268such that the slots1264a1,1264a2, and openings1264b,1264c, and1264dcommunicate from the outer surfaces1260,1262to the hollow interior1266.

The spinous process implant1250further includes a first extension1270projecting outwardly from the spacer1252transverse to the longitudinal axis1258to lie generally alongside either one or both of the superior and inferior spinous processes. In the exemplary embodiment ofFIGS. 25A-29, the first extension1270extends both superiorly and inferiorly from spacer1252in the spacer height direction h. First extension1270defines a generally superior/inferior dimension1272(FIG. 27) along spacer height h which is greater than a generally superior/inferior dimension1274of the spacer1252(FIG. 27) along the spacer height direction h. Abutment of the first extension1270with the superior and inferior spinous processes helps to restrain spacer1252from moving laterally and to maintain the spacer1252between the spinous processes. In the illustrative embodiment ofFIGS. 25A-29, the first extension1270also extends slightly posteriorly from spacer1252to define a posterior projection dimension1276(FIG. 26) along the spacer width direction w. The spacer1252defines a generally anterior/posterior dimension1278(FIG. 26) along the spacer width direction w and transverse to the spacer superior/inferior dimension1274(FIG. 27). When implant1250is implanted between the spinous processes of a patient, anterior sidewall1261bis the anterior-most surface of implant1250while extension surface1255(FIGS. 25A and 25C) is the posterior-most surface of implant1250.

In the exemplary embodiment ofFIGS. 25A-Dto29, the anterior/posterior dimension1278is smaller than the superior/inferior dimension1274, and the smaller anterior/posterior dimension1278is formed by relieving a portion1280of the anterior sidewall1261bof the spacer1252. In the exemplary embodiment, the longitudinal length (i.e., the length along the spacer length direction1) of the spacer anterior sidewall1261bis shorter than the longitudinal length of the spacer posterior sidewall1261aby a distance1282equal to approximately one-fourth of the overall longitudinal length1294of the spinous process implant1250. The exemplary spinous process implant1250includes a second extension (not shown but similar to those of the embodiments ofFIGS. 1-24) mountable to the spacer1252for movement relative to the first extension1270.

Referring toFIG. 25B, an end view of spinous process implant1250as seen from spacer second end1256is provided. As depicted in the figure, anterior surface1263of spacer anterior sidewall1261bincludes a superior-most point1269aand an inferior-most point1269b. Correspondingly, posterior side wall surface1265of spacer posterior side wall1261aincludes superior-most point1267aand inferior-most point1267b. Note that “superior-most” and “interior-most” are for designation and do not necessarily coincide with the absolute superior and inferior point of the spacer1252. The surface length of anterior surface1263of anterior sidewall1261bas the anterior surface1263is traversed from superior-most point1269ato inferior-most point1269b(at a fixed position along the length of spacer1252) is less than the surface length of posterior surface1265as the surface1265is traversed from superior-most point1267ato inferior-most point1267b(at a fixed position along the length of spacer1252).

As shown inFIGS. 25B and 26, spacer anterior sidewall1261bis spaced apart from spacer posterior sidewall1261aalong at least a portion of the length of spacer1252by a superior spacing distance11and an inferior spacing distance12. Distances11and12correspond to the width of slots1264a1and1264a2, and are typically, but not necessarily, equal. In addition, posterior side sidewall1261aincludes a partial, frusto-conical inner surface1273that slopes toward the interior1266and toward anterior sidewall1261bof spacer1252as the frusto-conical inner surface1273is traversed along the spacer length direction1from the spacer second1256toward the spacer first end1254.

In certain implementations, it may be advantageous to include bone growth promoting substance in the hollow interior1266of spacer1252. To facilitate the insertion and retention of such material, spacer1252includes inwardly projecting posterior and anterior lips1277aand1277b(FIG. 25C). Inwardly projecting posterior lip1277ais formed at the end of frusto-conical inner surface1273which is spaced apart longitudinally from spacer end1256. Inwardly projecting anterior lip1277bis formed proximate the free end of anterior sidewall1261b. The inwardly projecting lips reduce the spacer's open cross-sectional area A2(FIG. 25B) at the free end of anterior sidewall1261b(i.e., the end that is spaced apart from first extension1270) relative to the spacer's open cross-sectional area A1at the spacer end proximate first extension1270(FIG. 25C). Thus, a bone growth promoting substance can be inserted into hollow interior1266at spacer first end1254and at least partially retained within hollow interior1266by lips1277aand1277b.

The spinous process implant1250may have a body configuration generally like any of the embodiments shown inFIGS. 1-24and other suitable configurations. Preferably, at least the spacer second end1256has an anterior/posterior dimension1278(FIG. 26) along the spacer width direction w which is smaller than the superior/inferior dimension1274(FIG. 27) along the spacer height direction h. This relationship between dimensions1274and1278facilitates implantation, as described further below. Likewise, the spinous process implant1250may be used with a second extension generally configured like any of those illustrated inFIGS. 1-24and other suitable configurations. Thus, in one example, the second extension includes tabs such as tabs156of second extension128(FIG. 3) which are engagable with spacer superior and inferior slots1264a1and1264a2to allow the second extension to slidably engage spacer1252along the spacer length direction1to adjust the distance between the first and second extensions along the spacer length direction1. In addition, when the second extension is attached to spacer1252, the first and second extensions provide a pair of superior lobes that are spaced apart long the spacer length direction1and a pair of inferior lobes that are spaced apart along the spacer length direction1. In certain examples, the superior lobes of the first and second extensions are substantially aligned with one another when viewed along the spacer length direction1, as indicated in the embodiment ofFIGS. 4-6, as are the inferior lobes of the first and second extensions.

First extension1270has a geometry similar to that of extension128ofFIG. 8. Referring toFIG. 25Cfirst extension1270includes a first superior lobe1271aand a second inferior lobe1271b. First superior lobe1271aand second inferior lobe1271bare substantially co-planar to one another and are spaced apart from one another along the spacer height direction h. In addition, first superior lobe1271aprojects superiorly away from spacer1252while second inferior lobe1271bprojects inferiorly away from spacer1252. In the embodiment ofFIGS. 25A-25D, lobes1271aand1271bare integrally formed with spacer1252to define a unitary extension1270. However, a multi-piece implant system may also be provided in which lobes1271aand1271bare not connected to spacer1252or to one another. While the lobes1271aand1271bare shown rounded, they may be squared, triangular, or other shaped.

As shown inFIG. 25C, first extension1270has a centerline1277defined along the spacer height direction h. First superior lobe1271ahas a centerline1279athat is spaced apart posteriorly from first extension centerline1277by a distance w1while second inferior lobe1271bhas a centerline1279bthat is spaced apart anteriorly from first extension centerline1277by a distance w2. In certain implementations, the distances between the lobe centerlines1279aand1279band the first extension centerline1277are substantially equal.

Referring again toFIG. 25C, first superior lobe1271ais posteriorly adjacent to first concave surface1287a, while second inferior lobe1271bis anteriorly adjacent to second concave surface1287b. Multiple implants1250may be implanted between adjacent levels of the spine in the same manner as implant100shown inFIG. 9. First superior lobe1271ais shaped to be complementary to second inferior concave surface1287bsuch that when two spinal implants are placed on adjacent spinal levels, the first superior lobe1271aof the inferior-most implant is interfittable into the second concave surface1287bof the superior-most implant. Thus, first superior lobe1271ahas a radius of curvature r5that is substantially equal to the radius of curvature r6of the second concave surface1287b. Similarly, the second inferior lobe1271bis shaped to be complementary to the first superior concave surface1287asuch that when two spinal implants are placed on adjacent spinal levels, the second inferior lobe1271bof the superior-most implant is interfittable with the first superior concave surface1287aof the inferior-most implant. Thus, second inferior lobe1271bhas a radius of curvature r7that is substantially equal to the radius of curvature r8of the first concave surface.

In use, the spinous process implant1250is initially implanted with the smaller anterior/posterior dimension1278of the spacer second end1256parallel to the superior/inferior spacing between adjacent spinous processes1284,1286as shown inFIG. 28. In this orientation, the spinous process implant1250may be more easily inserted between the spinous processes1284,1286(FIG. 28). Once the second end1256is inserted between the spinous processes1284,1286, the implant may be rotated to orient the larger superior/inferior dimension1274parallel to the superior/inferior spacing defined between the spinous processes1284,1286. The spinous process implant may then be moved into the fully inserted position ofFIG. 29. A second extension, cerclage element, and/or other additional elements may then be implanted as desired and as described above relative toFIGS. 1-24.

An exemplary method of using the spinous process implant1250to treat a spinal disease of the type mentioned previously will now be described. In accordance with the method, two adjacent spinous processes are first selected based on an assessment of a spinal disease. The interspinous ligament between the selected spinous processes is either punctured or cut to allow implant1250to be positioned through the patient's sagittal plane. If desired, a bone growth promoting substance may be placed in hollow interior space1266of spacer1252. As illustrated inFIG. 28, implant1250is inserted between the selected spinous processes with anterior/posterior dimension1278positioned in parallel to the superior-inferior spacing defined between the selected spinous processes. Once the implant1250is positioned between the selected spinous processes, the implant1250is rotated about the longitudinal axis1258of spacer1252until superior/inferior dimension1274is positioned in parallel to the superior-inferior spacing between the spinous processes. The first extension1270is then placed into abutting engagement with the selected spinous processes. At this point, spacer second end1256projects through and beyond the patient's sagittal plane. If fasteners are provided on first extension1270, they may be engaged with the superior and inferior spinous processes on one side of the patient's sagittal plane.

If desired, a second extension such as second extension128ofFIGS. 3-8may then be movably attached to spacer1252by slidably engaging tabs156with superior and inferior spacer slots1264a1and1264a2. The second extension128is then medially slid along the spacer length1toward the patient's sagittal plane until second extension128comes into abutting engagement with the selected spinous processes. Once the desired position is reached, set screw130may be used to fix the position of second extension128along the spacer length1.

Referring toFIGS. 30 and 31, introducers in the form of a set of instruments1300are provided to facilitate lateral insertion of an implant into the interspinous space. The set of instruments includes a plurality of inserters1302,1303in which each inserter1302,1303has a first or handle portion1304and a second or working portion1306. The working portion1306is insertable into the interspinous space. Preferably, the handle portion1304extends transversely to the working portion1306to facilitate holding and manipulating the inserter1302,1303while the working portion1306is in the interspinous space. The handle portion1304and working portion1306may define a curve, angle, offset, and/or any other suitable transverse orientation. In the example ofFIG. 30, the inserters1302,1303are generally “L”-shaped. The working portion1306tapers from a relatively larger cross-sectional dimension at a first portion1307spaced away from its free end1308to a relatively smaller cross-sectional dimension at its free end1308. In the illustrative embodiment, the working portion is conical and tapers from a larger diameter to a smaller diameter. The free end1308of inserter1303defines a hollow tip having an opening1310. The set of instruments1300is provided with a plurality of similarly configured inserters having differently sized working portions1306such that the free end1308of one inserter1302will fit inside the opening1310at the tip of another inserter1303. Optionally, the working portion1306may be separated into opposing halves attached to opposing handles1314,1316. As the opposing handles1314,1316are moved relative to one another, the opposing halves of the working portion1306move relative to one another. In the illustrative embodiment, squeezing the handles1314,1316toward one another causes the working portion1306to expand as the opposing halves of the working portion1306open outwardly away from one another.

In use, a first inserter1302is inserted into the interspinous space. The first inserter1302is relatively small to ease insertion. As the free end1308is inserted further, the tapered working portion1306expands the interspinous space. Optionally, the interspinous space can be further expanded by expanding the working portion while it is inside the interspinous space such as by squeezing the handles1314,1316. A second, larger inserter1303is engaged with the first inserter1302by placing its hollow tip over the tip of the first inserter1302and then passing the overlapping instruments back through the interspinous space to remove the first inserter1302and insert the second inserter1303. As the end of the second inserter1303is inserted further, the tapered working portion expands the interspinous space. Optionally, the interspinous space can be further expanded by expanding the working portion1306while it is inside the interspinous space. Progressively larger inserters can be inserted in this fashion until the interspinous space has been expanded to the desired size. Once the desired size has been reached the appropriate implant size may be determined by noting the size of the last inserter. The inserter may optionally include indicia1320on the tapered working portion1306corresponding to different spacer sizes to further facilitate sizing the implant. The implant is inserted by engaging the spacer1402(FIG. 31) with the working portion1306of the second inserter1303as shown inFIG. 31. The implant may be engaged inside of the hollow tip of the inserter or the tip of the inserter may engage a hollow tip on the implant as shown. The spacer1402is pulled into the interspinous space as second inserter1303is withdrawn. If desired, a second extension may then be attached to the spacer body as described earlier with respect toFIGS. 1-24.

Referring toFIGS. 32-37, introducers in the form of a trocar instrument1500and a sleeve instrument1550, are shown with the spinous process implant1250ofFIG. 25. The trocar instrument1500includes a handle1502extending generally parallel to a handle axis1504. In the illustrative embodiment, the handle1502is generally round at a proximal end1506and is generally thinner and more rectangular distally. The proximal end1506includes an attachment portion1508for connecting to another instrument, grip, or the like. The distal end1510of the handle1502connects to a head1512that extends outwardly from the handle1502generally transverse to the handle axis1504and generally parallel to a head axis1514. The head1512may be cylindrical, egg shaped, polygonal, and/or any other shape. In the illustrative embodiment ofFIG. 32, the head is generally cylindrical about the head axis1514. A tapered leading end1516projects from the head generally along the head axis1514to ease insertion of the head1512between adjacent spinous processes. The leading end1516may be conical, prismatic, and/or any other suitable shape. In the illustrative embodiment ofFIG. 32, the leading end1516is a blend of a cylinder and a prism defined by opposing, cylindrical sides1518(one of which is shown) that are generally mirror images of one another and converging planar sides1520(one of which is shown) that are adjacent to and disposed between the opposing cylindrical sides1518. This configuration allows the planar sides1520to be inserted between adjacent spinous processes and the head1512to be rotated about the head axis1514to pry the spinous processes apart. With partial insertion of the leading end1516, the head1512may be rotated to open the interspinous space to permit further insertion until the head1512can be fully inserted between the spinous processes. The head1512further includes a rasp portion1522on the sides of the head1512. In the illustrative embodiment, the rasp portion1522includes a plurality of cutters formed on opposite sides of the head1512. The illustrative cutters are depressions having sharp edges at the head surface. With the head1512fully inserted between the spinous processes, the spinous processes will press into the rasp portion1522depressions such that rotation of the head1512about the head axis1514will rasp away soft tissues, the bone surface, and/or other tissues to prepare the spinous processes for receiving the spinous process implant1250. By preparing the spinous processes, the growth of bone between the spinous processes, into, onto, and/or through the spinous process implant1250is enhanced.

The sleeve instrument1550includes a handle1552extending generally parallel to a handle axis1554. In the illustrative embodiment, the handle1552is generally rectangular at a proximal end1556and becomes thinner distally. The back1558of the handle1552is generally flat and includes a concave portion1560on the back of the handle at the proximal end1556. The handle distal end1562connects to a sleeve1564that extends outwardly from the handle1552generally transversely to the handle axis1554and generally parallel to a sleeve axis1566to a leading end defined by a rim1568. The sleeve1564may be cylindrical, elliptical, polygonal, and/or any other suitable shape. In the illustrative embodiment ofFIG. 32, the sleeve1564is generally cylindrical and is sized to slide over the trocar instrument head1512in close fitting relationship. With the sleeve1564slid over the trocar instrument head1512, the flat back1558of the sleeve instrument handle1552lies flat against the flat front surface of the trocar instrument handle1502and the rounded portion of the proximal end1506of the trocar instrument handle1502nests in the concave portion1560of sleeve instrument handle1552. With both handles1502,1552being relatively thin near the distal ends1510,1562, the handles1507,1552occupy less space distally and fit more easily into a surgical site while maximizing the extension of the sleeve1564and head1512from the handles1502,1552. The sleeve1564further includes a series of annular grooves1570, or alternatively ridges, that enhance the engagement of the spinous processes with the outer surface of the sleeve1564to resist slipping of the sleeve from between the spinous processes. The sleeve1564further includes a relieved portion1572defining a first region of rim1568that is spaced apart from handle1552by a distance that is less than the distance by which rim1568is spaced apart from handle1552in a second region located away from relieved portion1572. The sleeve1564is sized to engage the spinous process implant1250. In the illustrative embodiment ofFIG. 32the sleeve1564is sized with an internal dimension able to receive the spacer1252in close-fit sliding relationship along the sleeve axis1566. Also in the illustrative embodiment, the relieved portion1572is sized to receive the spacer transverse to the sleeve axis1566in sliding relationship along the relieved portion1572to ease insertion of the spacer into the sleeve1564as will be discussed more fully below. In the illustrative embodiment, the relieved portion mid-point1573is positioned on the rim1568at a position offset from the handle axis1554so that the spinous process implant1250engages the relieved portion1572along an engagement axis1574angled relative to the handle axis1554as shown inFIG. 33. In the illustrative embodiment ofFIG. 33, the angle between the engagement axis1574and the handle axis1554is in the range of 0 to about 90 degrees; more particularly 0 to about 40 degrees; more particularly about 20 degrees. By positioning the relieved portion mid-point1573at an angle relative to the handle axis1554, the handle1552and a user's hand do not block the insertion path of the spinous process implant1250. The trocar instrument1500and sleeve instrument1550may be provided in a plurality of sizes corresponding to a plurality of sizes of spinous process implants1250.

FIGS. 34-37illustrate the use of the trocar instrument1500and sleeve instrument1550in accordance with a method of implanting the spinous process implant1250between a patient's adjacent spinous processes. The interspinous ligament is first removed or penetrated such that the head1512extends into and through the patient's sagittal plane. InFIG. 34the head1512of the trocar instrument1500has been worked between adjacent spinous processes1284,1286and the head is rotated back and forth about the head axis1514to rasp the opposed surfaces of the adjacent spinous processes1284,1286to prepare them for receiving the spinous process implant1250. The trocar instrument1500is removed and engaged with sleeve instrument1550and the assembly is reinserted between the spinous processes as shown inFIG. 35. The trocar instrument1500is then removed leaving the sleeve instrument1550in place. Alternatively, the sleeve instrument1550may be inserted between the spinous processes after removal of the trocar instrument1500without engaging the trocar instrument1500with the sleeve instrument1550. As shown inFIG. 36, the spinous process implant1250is inserted into the sleeve1564by engaging the spacer1252with the relieved portion1572along the engagement axis1574and then rotating the spinous process implant1250until its longitudinal axis1258is parallel to the sleeve axis1566while simultaneously pressing the spacer1252into the sleeve1564. The spinous process implant1250is pressed into the sleeve1564until the spinous process implant is seated as shown inFIG. 37. The sleeve instrument1550is then removed and a second extension, cerclage element, and/or other additional elements may then be implanted as desired and as described above relative toFIGS. 1-24. By using the relieved portion1572as described above, the size of the incision needed to implant the spinous process implant1250may be minimized. Alternatively, the spinous process implant1250may be inserted along the sleeve axis1566without first engaging the relieved portion and rotating the spinous process implant1250. Also, alternatively, the spinous process implant1250may be only partially inserted before the sleeve instrument1550is removed and the spinous process implant1250then subsequently seated.

Referring toFIGS. 38-40, an introducer in the form of a flexible guide1600includes an engaging portion1602, a relatively narrow leader1606, and a transition portion1604tapering between the engaging portion1602and the leader1606. The guide1600includes a flexible material allowing all or part of the guide1600to bend to facilitate pulling the guide1600between adjacent spinous processes. In the illustrative embodiment ofFIG. 38, the entire guide1600is formed of a flexible material such as polysiloxanes, natural rubber, synthetic rubber, polyethylene, polyester, polytetrafluoroethylene, and/or any other suitable material. The guide1600may be molded, cast, extruded, machined, braided, woven, wrapped, and/or otherwise formed. The engaging portion1602, transition portion1604, and leader1606may be made in one piece or made as discrete components and joined together. In the illustrative embodiment ofFIG. 38, the guide1600is molded as one piece of synthetic rubber. The engaging portion1602may engage the spinous process implant1250positively and/or frictionally. The engaging portion1602may engage inside and/or outside of the spinous process implant1250. In the illustrative embodiment ofFIG. 38, the engaging portion comprises a hollow sleeve that stretches to frictionally grip the outer surface of the spacer1252.

In use, the leader1606is passed between adjacent spinous processes1284,1286and used to pull the transition portion1604between the spinous processes1284,1286as shown inFIG. 39. The spinous process implant1250is pressed into place and rotated as the leader1606is pulled further to guide the spinous process implant1250between the spinous processes1284,1286as shown inFIG. 40. The guide1600is then removed and a second extension, cerclage element, and/or other additional elements may then, be implanted as desired and as described above relative toFIGS. 1-24.

Referring now toFIGS. 41-44, another example of interspinous implant1700is shown and described. The interspinous implant1700includes a spacer1702, a first extension or plate1704, and a second extension or plate1706. The spacer1702may be adjustably or permanently connected to either one or both of the first and second extensions1704,1706. In one example, the spacer1702is permanently connected to the first extension1704and the second extension1706may be adjustably connected to the spacer1702(e.g., axially moveable along a length of the spacer1702and fixed at an adjusted position).

The spacer1702may include first and second ends1720,1722spaced apart along a longitudinal axis1724. The spacer1702may further include first and second sidewall portions1726,1728(FIGS. 41 and 44), at least one of the first and second sidewall portions1726,1728may include one or more slot features1730, which in this exemplary spacer1702has a slot1730in the posterior portion of the first sidewall portion1726. The slot1730may allow implanting fusion material into the space and provides additional tissue in-growth paths among other things. The first and second sidewall portions1726,1728may be divided by at least one slot feature1732in the superior and inferior surfaces of spacer1702. The first and second sidewall portions1726,1728may have different lengths, shapes and sizes.

Each of the first and second extensions1704,1706may extend in superior and inferior directions relative to the spacer1702. Each of the first and second extensions1704,1706may include a first set of fasteners1708, such as, spikes, pins, screws, nails, etc. and a second set of fasteners1710, such as, spikes, pins, screws, nails, etc. that extend from a contact surface1712of first and second extensions1704,1706(best seen inFIG. 43). The contact surfaces1712are arranged to face and contact one or more spinous processes as previously described herein. The first and second sets of fasteners1708,1710are shown extending perpendicular from the contact surfaces1712and are intended to grip posterior elements of the spine such as, for example, the spinous processes, lamina, or combination thereof of a patient. The fasteners1708,1710may be mounted at an angle other than perpendicular to the contact surfaces to fit a particular anatomy. As described with respect toFIG. 3, the fasteners1708,1710may have some freedom to angelate with respect to contact surfaces1712.

The contact surfaces1712are arranged at an acute angle1714relative to a line perpendicular to the longitudinal axis1724of the spacer1702when the interspinous implant1700is assembled as shown inFIG. 44. In one example, the angle1714is in the range of about 0° to about 45°, and more preferably in the range of about 20° to about 30°. The contact surfaces1712are angled anteriorly so that the first and second sets of fasteners1708,1710are directed toward the sagittal plane and anteriorly. In other words, the contact surfaces1712converge in an anterior to posterior direction. The first and second sets of fasteners1708,1710may be adapted to seat in an anterior portion of the spinous processes, a junction between the lamina and spinous processes, or in a portion of the lamina, to provide fixation in a bone of that portion of the spine, which may be relatively stronger bone. The angled arrangement of the first and second extensions1704,1706relative to the spacer1702may be particularly well suited for connection to the L5-S1vertebrae given the small or nonexistent spinous process often associated with S1. The angled arrangement of the first and second extensions1704,1706may provide a first distance1′ at the anterior edge of the contact surface1712, and a second distance1″ at the posterior edge of the contact surfaces1712(FIG. 44).

In alternative arrangements, the contact surfaces1712of the first and second extensions1704,1706may be arranged at different angles relative to the longitudinal axis1724of the spacer1702. For example, one of the contact surfaces1712may be arranged perpendicular to the longitudinal axis1724and the other of the contact surfaces1712may be arranged at an angle1714that is non-perpendicular to the longitudinal axis1724.

An orientation of the first and second sets of fasteners,1708,1710may be at an angle1711relative to the line that is perpendicular to the longitudinal axis1724. In some cases, the angle1711may be perpendicular the contact surfaces1712. However, angle1711may be other than 90° such that the sets of fasteners1708,1710have more or less penetration into bone pursuant to patient needs. In some arrangements, the first and second sets of fasteners1708,1710may be arranged parallel with each other regardless of the angle1714of the contact surfaces1712.

In the example shown, the second extension1706is separate from spacer1702and translatable relative to spacer1702along longitudinal axis1724. Thus, the second extension1706may include a mounting portion1719to releasably attach second extension1706to spacer1702. The mounting portion1719defines a set screw bore1718. A set screw, such as set screw130as shown inFIG. 3may be threadably mated with the set screw bore1718and extend into contact with a portion of the spacer1702(e.g., the first sidewall portion1726) to secure the second extension1706to the spacer1702in a fixed axial position, in particular, the sides of slot1730may be tapered to engage the tip of a set screw.

The second extension1706also may include a spacer aperture1716sized to receive a portion of the spacer1702. In one example, the spacer aperture1716is sized to receive the first sidewall portion1726. The spacer aperture1716may be sized to permit or limit relative lateral or rotational movement between the second extension1706and the spacer1702when the interspinous implant1700is assembled as shown inFIGS. 42-44.

Referring now toFIGS. 45-49B, another example interspinous implant1800is shown and described including a spacer1802, a first extension or plate1804, and a second extension or plate1806. The spacer1802may be permanently or adjustably connected to either or both of the first and second extensions1804,1806. In at least one example, the spacer1802is permanently connected to the first extension1804and adjustably connected to the second extension1806. In at least one example, the first extension1804is integrally formed as a single piece with the spacer1802, and the second extension1806is a separate piece axially moveable along a longitudinal axis1824(FIG. 48) over a length of the spacer1802.

The spacer1802may include first and second ends1820,1822that are spaced apart along the longitudinal axis1824such that first end1820is proximate first extension1804and second end1822is distal first extension1804. The spacer1802may further include first and second sidewall portions1826,1828, that each may include one or more bores or through holes1830. The first and second sidewall portions1826,1828may be divided by one or more slots or cutouts such as superior and inferior slots1832,1834.

The first sidewall portion1826has a length X1measured from the contact surface1812of the first extension1804, and the second sidewall portion has a length X2measured from the contact surface1812of the first extension1804. In this embodiment, the length X1is less than the length X2. In other embodiments, such as the interspinous implant1700shown inFIGS. 41-44, the first sidewall portion1726has a length that is greater than a length of the second sidewall portion1728. The length of the second sidewall portion may be provided to clear the facets.

The first and second extensions1804,1806may extend in both superior and inferior directions from the spacer1802. Each of the first and second extensions1804,1806may include first and second sets of fasteners1808,1810, such as spikes, pins, screws, nail, etc. that extend from a contact surface1812. The first and second extensions1804,1806may further include a flared portion1840,1842at opposite ends thereof that define a curved surface or curvature1844(FIG. 48). The curved surface1844may be part of the contact surface1812or may be a continuous curvature with the contact surface1812. The first and second sets of fasteners1808,1810may extend from the contact surface1812and the curved surface1844. As shown in the embodiments the fasteners1808,1810may variable lengths as shown inFIG. 49A. For example, they may extend further in order for the fastener ends to reside in a plane defined by the fastener ends. In at least one example, the first and second sets of fasteners1808,1810are arranged generally parallel with each other and may, in some arrangements, be arranged collinear or offset with fasteners on the opposing extension1804,1806. Moreover, fasteners1808,1810may extend perpendicular to the tangent of curved surface1844such that some of the fasteners diverge as they extend from contact surfaces1812and/or curved surface1844.

The curved surface1844may extend in an arch or curve with a constant radius r10. The radius r10may increase or decrease moving along the flared portions1840,1842. The curved surface1844is a bent or flared surface in the anterior direction. The use of flared portions1840,1842enhance the ability of the first and second sets of fasteners1808,1810to seat in spinous processes having various geometries. For example, in a spinous process1850with little or no flare (i.e., a spinous process presents essentially a flat, vertical bone surface), the first and second sets of fasteners1808,1810penetrate and bite into the bone as shown inFIG. 49A. In a spinous process1850with a larger amount of flare (i.e., the spinous processes are wedge shaped or curved), the flared portions1840,1842allow the first and second sets of fasteners1808,1810to bite into the bone without interference from the anterior portions of the first and second extensions1804,1806abutting the bone and limiting penetration as shown inFIG. 49B. The flared portions1840,1842also permit the first and second extensions1804,1806to lie close to the lamina1857to help initially position the first and second extensions1804,1806and increase a bio-mechanical interlock of the interspinous implant1800with the bone. Additionally, if the fasteners1808,1810are arranged to extend perpendicular to the tangent of the flared portions1840,1842the fasteners would penetrate into the lamina1857.

The second extension1806may include a spacer aperture1816sized to receive a portion of the spacer1802, such as, for example, the first sidewall portion1826. The second extension1806also may include a mounting portion1819having a set screw bore1818defined therein. The set screw bore1818may be sized to receive fasteners such as a threaded set screw that extends through the set screw bore1818and contacts a portion of the spacer1802, such as first sidewall portion1826, to secure the second extension1806in a fixed axial position relative to the spacer1802and first extension1804. To facilitate a set screw engaging with first sidewall portion1826, the posterior facing surface of first sidewall portion1826may have surface texture, such as striations, knurling, or the like.

Referring now toFIGS. 50-52, another example interspinous implant1900is shown having a spacer1902, a first extension or plate1904and a second extension or plate1906. In this example, the spacer1902is formed as a separate piece from the first and second extensions1904,1906to provide a modular construction for the interspinous implant1900. The spacer1902, and first and second extensions1904,1906may be provided in various sizes and shapes that may be combined interoperatively to achieve a desired fit with a patient's anatomy. For example, the same first and second extensions1904,1906may be used with different sizes of spacers1902,1902A,1902B as shown inFIG. 52.

The spacer1902and first and second extensions1904,1906may comprise different materials such as polymers and metals as previously identified herein. In one example, the first and second extensions1904,1906may comprise a metal material and the spacer1902may be comprise a polymer material. Spacer1902may be radiolucent to facilitate, for example, visualization with medical imaging.

The spacer1902may comprise first and second ends1920,1922spaced apart along a longitudinal axis1924. The spacer1902includes a first sidewall portion1926A,1926B and a second sidewall portion1928. The sidewall portions1926A,1926B and1928may be connected along the longitudinal axis1924by transverse wall portions1925and separated or be divided from each other with one or more dividing slots1932. The first sidewall portions1926A,1926B may be sized to extend through apertures1916in the first and second extensions1904,1906to provide an adjustable connection there between as explained further below. Also, spacer1902may have channels or through holes1930.

The first and second extensions1904,1906extend in superior and inferior directions from the spacer1902. Each of the first and second extensions1904,1906may include first and second sets of fasteners1908,1910that extend from first and second contact surfaces1912,1913. The first contact surface1912may be arranged generally perpendicular to the longitudinal axis1924of the spacer1902. The second contact surface1913may be arranged at a compound angle or other angled relationship relative to the longitudinal axis1924. For example, the second contact surface1913may be a compound angle that angles inferiorly and anteriorly as shown inFIG. 54, which may make interspinous implant1900particularly suited for L5-S1.

The first and second sets of fasteners1908,1910may extend generally perpendicular to the first and second contact surfaces1912,1913, respectively. In the illustrated example, the first sets of fasteners1908may be arranged generally parallel, whether aligned or offset, with each other on the first and second extensions1904,1906. The second sets of fasteners1910may be arranged at a non-parallel angle relative to each other on the first and second extensions1904,1906as shown in at leastFIG. 54. The first set of fasteners1908may extend perpendicular to the plane defined by first contact surfaces1912. The second set of fasteners1910is arranged at an angle1915relative to the plane defined by the first contact surface1912as shown inFIG. 54.

The first and second extensions1904,1906also may include the spacer aperture1916sized to receive a portion of the sidewall portions1926A,1926B and1928of the spacer1902.FIG. 50illustrates the first sidewall portions1926A,1926B extending through spacer apertures1916of each of the first and second extensions1904,1906. The spacer apertures1916may be sized greater than the size of the first sidewall portions1926A,1926B to permit some relative lateral and rotational movement of the spacer1902in addition to relative axial movement along the longitudinal axis1924of the spacer1902.

The first and second extensions1904,1906may further include a bore1918sized to receive a locking block1952. The locking block1952may be arranged to releasably contact the first sidewall portions1926A,1926B of the spacer1902to secure the first and second extensions1904,1906in a fixed axial position relative to the spacer1902. The locking block1952may include a mating surface1953at a distal end thereof, a set screw cutout1954at a proximal end thereof, and a set screw1956sized to fit within the set screw cutout1954. The bore1918may include threads that threadably engage the threads of the set screw1956. Rotation of the set screw1956may advance the mating surface1953distally into contact with the first sidewall portions1926A,1926B.

The spacer apertures1916may be arranged noncollinearaly and be open to bore1918. The mating surface1953of the locking block1952may be angled such that the mating surface1953extends into spacer apertures1916to trap the first sidewall portions1926A,1926B in a self-centering relationship within the spacer apertures1916. In an alternative arrangement, the spacer apertures1916are collinear and the mating surface1953of the locking block1952is generally planer across its width so that the spacer1902is both vertically and axially adjustable relative to the first and second extensions1904,1906by moving the first sidewall portions1926A,1926B within the spacer apertures1916before clamping them into place with the locking block1952.

Referring now toFIGS. 53-54, another example interspinous implant2000is shown having a spacer2002and the first and second extensions or plates1904,1906described above with reference toFIGS. 50-52. The spacer2002may be separated into two separate halves, wherein a first half includes a first sidewall portion2026A and a second sidewall portion2028A, and a second half includes a first sidewall portion2026B and a second sidewall portion2028B. The spacer2002may include at least one slot2030defined therein.

The first sidewall portions2026A,2026B may be sized to extend through spacer apertures1916in the first and second extensions1904,1906. The locking block1952secures the arms of the spacer2002to the first and second extensions1904,1906as described above with reference to the interspinous implant1900. The independent halves of the spacer2002may be individually adjusted vertically, laterally, and angularly relative to the first and second extensions1904,1906to vary the position and height of the spacer2002. In one example, after a loosely assembled interspinous implant2000is placed with the spacer2002between adjacent spinous processes, a distraction tool may be engaged with the halves of the spacer2002and activated to separate the halves of the spacer2002and space the spinous processes to a desired spacing. The locking block1952may then be used to secure that spacing.

Alternatively, the spacer apertures1916and locking block1952may be arranged such that advancement of the locking block1952by rotating the set screw1956wedges the halves of the spacer2002apart.

The portions of the first and second extensions1904,1906that define the second contact surface1913may be defined as an inferior fastener pad1980that carry the second sets of fasteners1910. The fastener pads1980may be rotated about a sacral inclination axis such that the fastener pads1980form a compound angle flared inferiorly and rotated anteriorly. This compound angle may be particularly suitable for gripping an S1vertebrae.

The orientation of the fastener pad1980may be fixed or it may be adjustable. Adjustability may be provided by incorporating a bend zone1958(seeFIG. 53). The bend zone1958may be defined by providing a thinner, relatively easy to bend portion of the first and second extensions1904,1906. Adjustability also may be provided by incorporating a joint (not shown) such as a hinge, ball-and-socket, pivot or other suitable joint at a connection point of the fastener pad1980to the remaining portions of the first and second extensions1904,1906. The joint may be adjustable between unlocked and locked positions, wherein in an unlocked position the second set of fasteners1910may be penetrated into the bone to stabilize the joint. The joint may be locked using, for example, a set screw to fix an orientation of the fastener pad1980once it has been established relative to the remaining portions of the first and second extensions1904,1906.

Referring now toFIGS. 55-56, an alternative spacer configuration2102is shown. The spacer2102may include one or more hook features2136extending from an outer surface2138. The hook feature2136may extend in any direction and may have any shape and size. The hook feature2136may be operable to bite into an adjacent bone or hook behind an adjacent bone, such as a spinous process or lamina to help in securing the spacer2102to the spinous process.

FIGS. 55-56illustrate the hook feature2136extending inferiorly and curved posteriorly. This arrangement of the hook feature2136may be well adapted for hooking onto a superior edge of any vertebrae and, in particular, the S1vertebrae. The spacer2102may be combined with any of the first and second extensions of the various implants described herein. The hook feature2136may be well suited for combination with an interspinous implant that is specifically adapted for fixation to the L5and S1vertebrae. In certain aspects, the hook feature2136may be provided with any of the aforementioned spacers. When used in conjunction with the S1vertebrae, the inferior portions of the first and/or second extensions, lobes, or plates may be reduced or even eliminated.

Referring now toFIGS. 57-58, the interspinous implant1900is shown and described in further detail. At least one of first and second extensions1904,1906may include first and second lobes1960,1962at opposing ends thereof (second extension1906being shown inFIGS. 57-58). The lobes have a peripheral surface with a radius r11, r12, respectively. A centerline1964extends from the first lobe1960to the second lobe1962.

The second extensions1906further includes a first concave surfaces1966,1968having a radius r13, r14, respectively, along one side surface, and a pair of second concave surfaces1970,1972having a radius r15, r16, respectively, along an opposing side surface. The radiuses r13, r14, r15, r16may be similar in size to the radiuses r11, r12. For example, the radiuses r13, r14, r15, r16may be within about 5% to about 30% greater or less than the radiuses r11, r12. The first extension1904would have similar dimensions, but is not shown for convenience.

The first lobe1960may be referred to as a superior lobe that is anteriorly adjacent to the first concave surface1966and posteriorly adjacent to the concave surface1970. The second lobe1962may be referred to as an inferior lobe that is anteriorly adjacent to a first concave surface1968and posteriorly adjacent to a second concave surface1972. The radiuses of the first and second lobes1960,1962may be similar such that when two interspinous implants1900are placed at adjacent spinal levels, the first and second lobes1960,1962are interchangeably interfittable with adjacent concave surfaces1966,1968,1970,1972. Depending on patient anatomy and other surgical considerations, an interspinous implant1900may be interfit anteriorly or posteriorly with a first or second lobe1960,1962in any combination as shown with the plurality of interspinous implants1900and1900A-1900D shown inFIG. 57. Furthermore, the interspinous implant1900may be angled anteriorly or posteriorly while maintaining the interfitting relationship as shown inFIG. 58, wherein an angled centerline1974of the interspinous implants1900A-1900D is arranged at an angle relative to the centerline1964.

Although examples of a spinous process implant and associated instruments and techniques have been described and illustrated in detail, it is to be understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, variations in and modifications to the spinous process implant, instruments, and technique will be apparent to those of ordinary skill in the art, and the following claims are intended to cover all such modifications and equivalents.