HK1171354B - Interspinous process implants having deployable engagement arms - Google Patents

Description

Interspinous process implant with deployable engagement arms

Cross Reference to Related Applications

This application claims priority to U.S. patent application serial No.12/538,068 filed on 8/7/2009, which is a continuation-in-part application of and claims priority to U.S. patent application serial No.12/011,905 filed on 30/1/2008, which in turn claims priority to U.S. patent application serial No.12/011,905 filed on 11/1/2007, U.S. patent application serial No. 61/001,430 filed on 11/29/2007, U.S. patent application serial No. 61/000,831 filed on 10/29/2007, U.S. patent application serial No. 60/961,780 filed on 24/7/2007, U.S. patent application serial No. 60/959,799 filed on 16/2007, and U.S. patent application serial No. 61/007,916 filed on 5/1/2007. This application also claims priority benefits from U.S. patent application serial No.61/207,339 filed on 11/2/2009. The entire contents of each of the aforementioned patent applications are incorporated herein by reference.

Technical Field

The present invention relates to spinal implants, and more particularly to an interspinous process implant having a threaded body and deployable engagement arms for percutaneous placement into the interspinous process space to treat lumbar spinal stenosis.

Background

The spine is made up of a series of twenty-four vertebrae extending from the skull to the hips. Soft tissue intervertebral discs are disposed between adjacent vertebrae. The vertebrae provide support for the head and body, while the intervertebral discs serve as cushioning pads. In addition, the spine encloses and protects the spinal cord, which is surrounded by a bone tunnel (bony channel) known as the spinal canal. There is typically a space between the spinal cord and the boundaries of the spinal canal so that the spinal cord and its associated nerves are not compressed.

Over time, the ligaments and bone surrounding the spinal canal may thicken and harden, resulting in narrowing of the spinal canal and compression of the spinal cord or nerve roots. This condition is called spinal stenosis, which results in back and leg pain and numbness, a weakening and/or loss of balance. These symptoms often worsen after walking or standing for a period of time.

There are a variety of non-surgical treatments for stenosis. These methods include the use of non-steroidal anti-inflammatory drugs to reduce swelling and pain, and corticosteroids injection to reduce swelling and treat acute pain. While some patients may experience relief from the symptoms of spinal stenosis by such treatment, many patients do not experience relief and, therefore, are moving to surgical treatment. The most common surgical procedure for treating spinal stenosis is a decompressive laminectomy, which involves removing portions of the vertebrae. The goal of the surgical procedure is to relieve pressure on the spinal cord and nerves by increasing the area of the spinal canal.

Interspinous Process Decompression (IPD) is a less invasive surgical procedure for treating spinal stenosis. Through IPD surgery, bone or soft tissue removal is not required. However, the implant or spacer device is positioned posterior to the spinal cord or nerve between spinous processes protruding from vertebrae in the lower back. A well-known implant for performing IPD procedures is the X-STOPThe apparatus was first introduced by St.Francis Medical Technologies, Inc. of Alameda CA. However, X-STOPImplantation of the device still requires an incision to access the spinal column to deploy the X-STOPProvided is a device.

It would be advantageous to provide an implant for performing IPD surgical procedures that can be inserted percutaneously into the interspinous process space and effectively treat lumbar spinal stenosis.

Disclosure of Invention

The present invention relates to new and useful spinal implants, which in one aspect comprise a spinal implant comprising: an elongate body portion configured and dimensioned for percutaneous introduction into an interspinous process space. The body portion may be wholly or partially threaded or alternatively have a smooth surface.

The body portion may include an inner lumen, and further include a plurality of deployable engagement members adapted and configured to move in unison (in tandem) between a stowed position retracted within the inner lumen of the body portion and a deployed position extending from the inner lumen of the body to engage the spinous processes.

A drive assembly may be provided that extends into the internal cavity of the threaded body portion for selectively cooperatively moving the engagement members from the stowed position to the deployed position. Means may be provided in operative association with the drive assembly for selectively locking the engagement members in the deployed position. The drive assembly may include a main drive shaft extending into the internal cavity of the body portion along a longitudinal axis of the body portion. The drive shaft may include a shift end having a plurality of bevel gear teeth for operative engagement with the bevel gear teeth on the central hub of each engagement member to facilitate torque transfer therebetween.

Two engagement members for engaging the spinous processes can be provided, wherein each engagement member includes a pair of curved engagement arms extending radially outward from a central hub. The central hub of each engagement member may include a plurality of bevel gear teeth and may be mounted for rotation about a common axis extending transverse to the longitudinal axis of the body portion. Each engagement arm may include a distal claw portion having a plurality of different teeth for engaging the spinous process.

According to the invention, the threaded body portion may comprise an outer profile which tapers axially inwardly in the distal nose portion of the body portion, the outer profile being configured to gradually distract adjacent spinous processes during insertion or advancement of the implant into the interspinous process space. The thread may be provided on the body portion and may extend at least partially over the nose portion of the body portion. The distal nose portion may taper axially inwardly relative to a central region of the body at an angle of between about 5 degrees and 65 degrees relative to a longitudinal axis thereof. According to one aspect of the invention, the angle may be between about 15 degrees and 45 degrees. According to another aspect, the angle may be between about 25 degrees and 35 degrees. According to another aspect, the angle may be about 30 degrees.

An internal core may be provided that is adapted and configured for use in hardening a spinal implant, the internal core being disposed within a body portion of the subject implant. Such a core may comprise an integral tip portion disposed at the distal end of the implant. If desired, a separately formed tip portion, whether or not such a core portion is provided, may be provided and disposed at the distal end of the implant.

According to the present invention, the body portion and the tip portion may be formed of different materials.

The tip may include an axially inward taper and may or may not be threaded on its outer surface depending on the exact implementation.

The body portion may include a separately formed proximal portion formed of a material different from the material forming the central portion of the body portion. The proximal portion may be formed of a metallic material and the central portion of the body portion may be formed of a polymeric material, for example.

At least one stop recess may be provided on the implant to align the implant with an insertion device for the implant.

According to another aspect of the invention, a spinal implant comprises: an elongated body portion configured and dimensioned for percutaneous introduction into an interspinous process space and having an inner lumen; a deployable engagement member adapted and configured for cooperative movement between a stowed position retracted within the interior cavity of the body portion and a deployed position extending from the interior cavity of the body to engage the spinous process; and a rotatable drive shaft extending along a longitudinal axis thereof into the interior cavity of the threaded body portion for selectively cooperatively moving the engagement members from the stowed position to the deployed position.

A locking cover may be provided in operative association with the rotatable drive shaft and the body portion for selectively locking the engagement member in the deployed position.

Two engagement members for engaging the spinous processes can be provided, wherein each engagement member includes a pair of curved engagement arms extending radially outward from a central hub. The central hub of each engagement member may include a plurality of bevel gear teeth and be mounted for rotation about a common shaft extending transverse to the longitudinal axis of the body portion.

A drive shaft may be provided that includes a speed change end having a plurality of bevel gear teeth for operative engagement with the bevel gear teeth on the central hub of each engagement member to facilitate torque transfer therebetween. Each engagement arm may include a distal claw portion having a plurality of different teeth for engaging the spinous process.

In accordance with yet another aspect of the present invention, there is provided a method of laterally inserting a spinal implant into an interspinous process space, comprising the steps of: forming an incision in the patient's skin from a lateral side of a target interspinous process space in which an implant is to be placed; inserting a stylet through the incision using internal imaging techniques transverse to the target interspinous process space to form an access path; sequentially inserting one or more dilators along the access path to dilate soft tissue between the incision and the target intervertebral projection space; inserting a cannula through the access path; selecting an implant having a size suitable for a desired amount of intervertebral distraction; inserting an implant held by an insertion device through the cannula until a target interspinous process space is reached; and advancing the implant into the interspinous process space.

The method according to the invention may further comprise the following steps, for example. The methods may further include the step of aligning the implant with the spinous process of the patient after the advancing step.

The advancing step may include rotating the implant along a longitudinal axis of the implant to effect axial advancement of the implant by means of threads formed on an outer surface of the implant.

These methods may further comprise the steps of: when the implant includes a plurality of engagement members for engaging the spinous processes adjacent to the target interspinous process space, the engagement members are deployed.

Fluoroscopy may be used as an internal imaging technique during insertion of the stylet and optionally throughout the procedure, such as during insertion of the implant body.

The tap is insertable into a target interspinous process space and is used to form threads on a surface of an adjacent spinous process prior to insertion of the threaded implant for threaded engagement with the implant.

The method of the present invention may further comprise the step of filling one or more cavities within the implant with an osteogenesis promoting substance. The osteogenesis promoting substance may be, for example, demineralized bone glue.

It will be understood that each feature of the disclosed implants and related methods can be interchanged with various other features and freely combined to utilize any combination thereof. These and other features of the intervertebral projection implant and percutaneous placement method of the subject invention will become more apparent to those skilled in the art from the following detailed description of the preferred embodiments, which is to be read in connection with the accompanying drawings.

Drawings

Thus, those skilled in the art to which the subject invention pertains will readily understand, without undue experimentation, how to make and use the interspinous process implant of the subject invention, the preferred embodiments of which will be described in detail herein below with reference to certain drawings, wherein:

fig. 1 is a perspective view of an interspinous process implant constructed in accordance with a preferred embodiment of the subject invention, including a threaded body portion (shown in perspective) configured and dimensioned for percutaneous introduction into an interspinous process space of a patient, and a set of engagement arms for selectively engaging a spinous process, the engagement arms disposed in a stowed position within a lumen of the threaded body portion.

FIG. 2 is a perspective view of the interspinous process implant of FIG. 1 with the engagement arms disposed in a deployed position extending from the interior cavity of the threaded body portion.

FIGS. 3, 4 and 5 are exploded perspective views of the interspinous process implant of FIG. 1 with parts separated for ease of explanation;

FIG. 6 is a detailed cross-sectional view of the proximal end of the interspinous process implant of FIG. 1, taken along line 6-6 of FIG. 1;

fig. 7 is a transverse cross-sectional view looking toward the proximal end of the interspinous implant of fig. 1, taken along line 7-7 of fig. 6;

FIG. 8 is a representative diagram illustrating a posterior insertion technique illustrated with the aid of the interspinous process implant of FIG. 1, as applicable to all embodiments of the present invention;

FIG. 9 is a representative view illustrating a lateral insertion technique illustrated by way of the interspinous process implant of FIG. 1, as applicable to all embodiments of the present invention;

FIG. 10 is a representation illustrating the posterior (dorsal) side of the advancement of the interspinous process implant of FIG. 1 as may be applied to all embodiments of the present invention;

FIG. 11 is a posterior (dorsal) representation of the interspinous process implant of FIG. 1 illustrating deployment of the engagement arms and engagement of the engagement arms with the adjacent spinous processes;

FIG. 12 is a perspective view of another embodiment of an interspinous process implant having an integral tap chamfer on its leading end providing self-tapping capability, obviating the need for separate threading of the interspinous process space, in accordance with the present invention;

FIG. 13 is a partial, inferior perspective view of the interspinous process implant of FIG. 12;

fig. 14 is a perspective view of another embodiment of an interspinous process implant having separately formed tip portions and an inner core portion (fig. 15) to provide additional structural rigidity in accordance with the present invention.

FIG. 15 is an exploded view of the interspinous process implant of FIG. 14;

FIG. 16 is a perspective view of another embodiment of an interspinous process implant according to the present invention, the interspinous process implant having an outer surface without threads;

FIG. 17 is a posterior (dorsal) view illustrating placement of the interspinous process implant of FIG. 16 into a target interspinous process space; and

FIG. 18 is a partially exploded view of an alternative configuration of a distal tip for an interspinous process implant according to the present invention.

Detailed Description

Referring now to FIG. 1, one exemplary embodiment of an interspinous process implant constructed in accordance with a preferred embodiment of the subject invention is illustrated and generally designated by the reference numeral 10. Implant 10 is particularly suited for performing minimally invasive surgical procedures to treat spinal stenosis, including, for example, Interspinous Process Decompression (IPD).

However, it is contemplated that the implant 10 of the subject invention may be equally useful in other spinal procedures, including but not limited to as an adjunct to spinal fusion procedures or spinal fixation devices. As will be readily appreciated by those skilled in the art from the following description, the interspinous process implant of the subject invention is well suited for percutaneous insertion, thus overcoming many of the deficiencies of the prior art devices currently used in IPD procedures. That is, implant 10 is configured and dimensioned for introduction and placement through a small skin incision, rather than an open surgical procedure involving removal of tissue.

Referring to fig. 1-5, the intervertebral projection implant 10 of the subject invention includes a threaded body portion 12 having left and right body sections 12a, 12 b. The body sections 12a, 12b are held together in part by fixation pins 14 located adjacent to a tapered nose cone 15 of the implant body 12.

The two body sections 12a, 12b are preferably formed from a biocompatible polymeric material having a modulus of elasticity substantially similar to that of bone, for example Polyetheretherketone (PEEK) or similar materials. However, the body sections may also be made of machined bone, biocompatible metals such as titanium alloys or stainless steel, ceramics, composites or similar materials or combinations thereof.

The body portion 12 is configured and dimensioned for placement between spinous processes of a symptomatic intervertebral disc layer (disclevel) via a threaded connection. In this regard, it is contemplated that the outer diameter of the implant 10 may range from about 8.0mm to about 16.0mm with a thread depth of about 1.0 mm. The threads on the body portion 12 of the implant 10 may be configured such that the implant may be self-tapping to ease insertion of the implant into the interspinous process space, as described below in connection with fig. 12 and 13.

In the embodiment shown in fig. 1 to 7, an optional stop recess 3, in this embodiment constituted by stop recesses 3a and 3b formed in the two body sections 12a and 12b, respectively, is provided for engaging an insertion device in a bilateral insertion technique, wherein the insertion device is attached to the proximal and distal ends of the implant, engaging the stop recess 3. This technique is described in U.S. patent publication No.2009/0054988, the disclosure of which is incorporated herein by reference in its entirety.

It is contemplated that the implant 10 may have various thread forms, such as a turned thread or a female thread. It is also contemplated that the body portion of the implant may be provided without threads and as discussed in more detail below in connection with fig. 16 and 17 while remaining within the scope of the subject disclosure.

In addition to facilitating advancement of the implant 10 into the target interspinous process space through axial rotation of the implant 10, the threads on the implant 10 also facilitate spinal fixation by engaging corresponding threads formed in the adjacent spinous processes prior to or during insertion, as described in greater detail below.

Further, as shown, the distal end of the implant 10 includes a tapered nose 15, thus gradually enlarging the interspinous process space during insertion. Thus, a separate expander is not required to expand the interspinous process space prior to insertion of the implant 10. The distal nose 15 as shown is tapered axially inwardly relative to the central region of the body at an angle alpha (alpha) of between about 5 degrees and about 65 degrees relative to its longitudinal axis 19. According to one aspect of the invention, the angle α (alpha) may be between about 15 degrees and 45 degrees. According to another aspect, the angle α (alpha) may be between about 25 degrees and 35 degrees. According to another aspect, the angle may be about 30 degrees. However, it is understood that the angle α (alpha) should not be limited to the foregoing range. Further, it is understood that these ranges may be applied to other embodiments of the present invention.

Moreover, as will be appreciated by those skilled in the art, due to the provision of such threads, the implant 10 may serve as a threaded cage for the interspinous process space. To facilitate implementation as a cage, the body portion 12 may be provided with a plurality of apertures or cut-outs that allow for the insertion of demineralized bone or another type of fusion adjunct material, which also facilitates bone ingrowth, as discussed further below.

The body portion 12 of the implant 10 defines an internal cavity 18 or chamber that houses two deployable engagement members 20a, 20b formed of titanium, stainless steel, ceramic, composite, or similar high strength and light weight biocompatible metals. The engagement members 20a, 20b are adapted and configured for coordinated movement between a stowed position retracted within the interior cavity 18 of the body portion 12 as shown in figure 1 and a deployed position extended from the interior cavity 18 of the body portion 12 to engage the spinous processes as shown in figure 2. Advantageously, implantation of the implant 10 is inhibited once the engagement members 20a, 20b are deployed to engage the spinous processes, in addition to the lateral implantation resistance provided by the threads alone.

As shown and best shown in fig. 3-5, each engagement member 20a, 20b includes a pair of curved engagement arms 22a, 22b extending radially outward from a central hub 24 in an arcuate manner. In the illustrated embodiment, each engagement arm 22a, 22b includes a distal clevis portion 26a, 26 b. The finger portions 26a, 26b of the engagement arms 22a, 22b are preferably each provided with a plurality of tines 28, the tines 28 being used to engage and pierce the bone of the adjacent spinous processes to effect fixation of the implant 10. The teeth 28 on each jaw portion 26a, 26b are preferably, but not necessarily, of different size and orientation to better engage a particular bone formation of an individual, which may vary from patient to patient in size and shape.

The central hub 24 of each coupling member 20a, 20b includes a plurality of bevel gear teeth 30 and is mounted for rotation about a spindle 32 extending transverse to the longitudinal axis of the body portion 12. The mandrel 32 is secured in place within the body portion 12 of the implant 10 by means of a retaining ring 34, such as a nut, circlip, snap or press-fit ring, or other mechanical fastener known in the art. According to a preferred aspect, a ring 34, or alternatively a cap or termination device having another suitable configuration, is welded to the mandrel 32. In a preferred embodiment, the welding is performed by laser welding. In the embodiment of fig. 1 to 5, the mandrel 32 and the retaining ring 34 are also used in combination with the securing pin 14 provided more proximally to hold the body sections 12a, 12b together.

The interspinous process implant 10 further includes an actuating assembly defined in part by a long drive shaft 40, the long drive shaft 40 extending along its longitudinal axis into the interior chamber 18 of the body portion 12. The drive shaft 40 includes a proximal threaded section 42, an intermediate support flange 44, and a distal drive section 46. The proximal threaded section 42 comprises an end fitting 48 of hexagonal shape, the end fitting 48 being intended to cooperate with an insertion device (not shown in fig. 1 to 5) having a socket for receiving at least the end fitting 48 of the shaft 40. The insertion device is used to axially rotate or otherwise actuate the drive shaft 40 to selectively deploy the engagement members 20a, 20 b.

The intermediate support flange 44 of the drive shaft 40 is received, along with an axially rotating annular bushing 50 supporting the drive shaft 40, within a journal chamber 45, the journal chamber 45 being formed within the proximal end of the internal cavity 18 of the body portion 12. The distal drive subsection 46 of the drive shaft 40 includes a distal bevel gear 52, which distal bevel gear 52 is adapted and configured to operatively engage the bevel gear teeth 30 located on the central hub portion 24 of each engagement member 20a, 20b and transmit torque to the bevel gear teeth 30 to selectively co-rotate the engagement arms 22a, 22b of the two engagement members 20a, 20b to a deployed position such as shown in fig. 2 and 11.

A locking cap 60 is operatively associated with the threaded proximal subsection 42 of the drive shaft 40. The locking cap 60 serves two functions. First, the locking cap 60, together with the securing pin 14 and spindle 32, functions to hold the body sections 12a, 12b together. In addition, the locking cover 60 functions to selectively lock the pair of engaging arms 22a, 22b of the engaging members 20a, 20b to the deployed position. More specifically, the locking cap 60 is cooperatively associated with the threaded lock nut 62 by means of a pair of opposed locating pins 64a, 64b that are received within an annular groove 66 formed in the lock nut 62. The lock nut 62 is threadably associated with the threaded proximal subsection 42 of the drive shaft 40.

In addition, the locking cap 60 includes an inner planar surface 67, as best shown in fig. 5, the inner planar surface 67 having a set of four locking ribs 68 a-68 d disposed thereon. These ribs 68a to 68d are configured and dimensioned to engage in a rotationally locked manner with toothed annular surfaces 70a, 70b (see fig. 3) provided on the proximal end of the body sections 12a, 12 b. The interlocking action of the ribs 68 a-68 d with the toothed annular surfaces 70a, 70b is best seen in fig. 1 and 2 through a semi-circular port 72 formed in the side wall of the locking cap 60. One or more circumferentially opposed pairs of ports 72 may be provided to facilitate machining of the internal structure of the locking cap 60.

In use, once the engagement arms 22a, 22b of each engagement member 20a, 20b have been deployed by axially rotating the drive shaft 40, the locking cap 60 is moved axially into the locking position by rotation of the threaded lock nut 62 until the locking ribs 68a to 68d of the locking cap 60 engage the toothed annular surfaces 70a, 70b on the proximal end of the body sections 12a, 12 b. It should be noted that although the engagement arms 22a, 22b are deployed in unison in practice, the present invention is not limited to this configuration.

As best shown in fig. 5-7, an aperture 74 is formed in the planar surface 67 of the locking cap 60, the aperture 74 including diametrically opposed flat surfaces 76, the diametrically opposed flat surfaces 76 corresponding with diametrically opposed longitudinal flats 78 formed on the threaded portion 42 of the drive shaft 40. The interaction between the opposing surfaces 76 of the aperture 74 and the opposing lands 78 of the threaded portion 42 allows the locking cap 60 to move axially relative to the drive shaft 40 while preventing the locking cap 60 from rotating relative to the drive shaft 40 when the locking cap 60 is moved into the locked position by rotation of the lock nut 62.

Additionally, one or more alignment and/or engagement structures may be provided on the interspinous process implant 10 for engaging an insertion device for the interspinous process implant. As illustrated in the embodiment of fig. 1 to 7, an annular groove 13 may be provided in the proximal region of the implant 10 for securing the implant to the insertion device, limiting accidental relative axial movement. One or more axially located circumferentially located grooves 16 may be provided in combination with the annular groove 13 for limiting unintentional relative rotational movement therebetween.

Fig. 8-11 illustrate insertion example aspects of a device according to the present invention and are described in connection with the interspinous process implant of fig. 1-7. As seen in fig. 8, a sleeve 87 is provided to facilitate insertion. The insertion method may include the use of a stylet, dilator, or the like to obtain a pathway for the cannula 87 and define a path, as described in more detail below. However, dorsal insertion may be achieved as set forth in U.S. patent application serial No.12/011,905 (U.S. publication No.2009/0054988), filed on 30/1/2008, the entire contents of which are incorporated herein by reference.

As shown, in FIG. 8, the dorsal insertion of the subject implant, represented by implant 10, may be accomplished by forming an incision 89 through the patient's skin 88 at a height corresponding to the targeted interspinous process space 82 defined between adjacent spinous processes 81a, 81 b. Through the dorsal approach shown in fig. 8, the path traversed by the implant 10, and thus also by the cannula 87, is curved to align the path and the implant 10 with the target interspinous process space 82.

In contrast, fig. 9 illustrates the direct lateral insertion of the implant 10 into the target interspinous process space 82. In this configuration, an incision 99 is made in the patient's skin 88, and eventually a cannula 97 is advanced through the tissue to the target interspinous process space 82, and the implant 10 coupled to the insertion device 92 is advanced through the cannula 97. As shown in fig. 10 and 11, the cannula 97 is not shown for clarity, and the implant 10 is rotated axially by means of the insertion device 92 to thread the implant 10 into the target interspinous process space 82, distract the adjacent spinous processes 81a, 81b, and advance the implant to its final position, generally centered relative to the spinous processes 81a, 81 b. During rotation of the implant 10, relative rotation and axial translation between the implant 10 and the insertion device 92 are preferably prevented by the above-mentioned grooves 13, 16. When in its position, the engagement arms 22a, 22b may be actuated to the deployed configuration shown in fig. 11. Subsequently, the lock nut 62 may be tightened, distally advancing the locking cap 60 into engagement with the body 12, thereby rotationally locking the locking cap 60 with the body 12 via the toothed surface 70 and the ribs 68 a-68 d described above. Moreover, the lock nut 62 is held in frictional engagement with the lock cover 60 to fix the lock nut 62 and the lock cover 60 in the axial direction and in a rotation-proof manner. Subsequently, one or more bone growth promoting substances may be packed in the implant 10 and/or around the implant 10 to promote spinal fusion, as desired.

The alignment pins 64a and 64d are provided in the illustrated embodiment for maintaining an axial connection (relative to the central longitudinal axis of the implant) to hold the locking cap 60 and the locking nut 62 together while allowing axial rotation of the locking nut 62 relative to the locking cap 60. Thus, tightening of the lock nut 62 produces a rotational locking engagement between the body 12, the locking cap 60 and the drive shaft 40, thereby fixing the position of the engagement arms 22a, 22 b. Similarly, loosening of the locking nut 62, such that pulling the locking cap 60 proximally by way of the alignment pins 64a and 64d, allows the engagement arms 22a, 22b to unlock and retract, thereby allowing the implant 10 to be removed.

A separate tap may be used prior to insertion of the implant, or the implant may be provided with a structure that provides self-tapping capabilities as described herein.

As discussed above, a method of laterally inserting the spinal implant 10 into the target interspinous process space 82 may include: after the incision 99 is made, a stylet (not shown) is inserted through the incision transverse to the target interspinous process space 82, preferably using internal imaging techniques such as fluoroscopy. The insertion of the stylet forms an access path along which one or more dilators may be sequentially advanced to dilate the soft tissue between the incision and the target interspinous process space 82. The cannula 97 can then be advanced through the access path. After selecting an implant 10 having dimensions suitable for the desired amount of intervertebral distraction, the implant 10 can be inserted, held by the insertion device 92, advanced through the cannula 97 until the target interspinous process space 82, after which the implant can be inserted into the interspinous process space. In the case of a threaded implant, a rotational motion is applied to advance the implant 10 and distract the adjacent spinous processes 81a, 81 b. In the case of a non-threaded implant, lateral pressure may be applied until the implant is in the desired position, after which any engagement elements, if provided, may be deployed.

Fig. 12 and 13 are perspective views of another embodiment of an interspinous process implant 100 according to the present invention, the interspinous process implant 100 having an integral tap chamfer (tap chamfer)117 on its leading end 115, thereby providing self-tapping capability and thus avoiding the need to separately tap the targeted interspinous process space (e.g., 82). The same elements as those described in conjunction with the above embodiments are denoted by the same reference numerals.

Implant 100 is similar in many respects to implant 10 of fig. 1-7 and includes a threaded body 112, claw portions 26a, 26b on each engagement arm, an optional retaining recess 3, a retaining nut 62, an end fitting 48 for actuating the engagement arms, as described in connection with the embodiment of fig. 1-7. However, in such embodiments, the proximal cap 119 is provided with the body 112 and is preferably integrally formed, such as by machining and/or casting from a metallic material, such as titanium, surgical grade stainless steel, or other suitable biocompatible material, such as PEEK. The proximal cap 119 is configured to receive the proximal end of the body 12, thereby maintaining the longitudinally separated portions of the body in contact with one another. The proximal cap 119 is preferably press fit onto the body during assembly thereof, but may be attached in another suitable manner, which may include a friction fit, threaded engagement with one another, or the like. The proximal cap 119 includes an annular toothed surface 70 (see, e.g., fig. 15), the annular toothed surface 70 being an integral embodiment of the structure provided in the separate halves 70a, 70b in the above-described embodiments. The proximal cap 119 is also provided with opposing circumferential tangential slots 113, the circumferential tangential slots 113 being located in a planar portion 137 also provided on the proximal cap. The planar portion 137 and the slot 113 prevent inadvertent relative rotation and axial movement between the implant 100 and the insertion device, respectively. The locking cap 160 includes two circumferentially opposed ports 172 disposed therein.

Fig. 14 and 15 are perspective and exploded perspective views of another embodiment of an interspinous process implant 200 according to the present invention, the interspinous process implant 200 having a tip portion 205 and an inner core portion 207 formed separately, the tip portion 205 and inner core portion 207 providing additional structural rigidity to the implant 200. The same elements as those described in connection with the above embodiments are denoted by the same reference numerals. Many of the elements are substantially the same as in the previous embodiment, as are the function of the engagement arms and their respective engagement fingers 26a, 26 b. The proximal cap 119 is similar in construction and function to the embodiment of figures 12 and 13. The exploded view of fig. 15 illustrates one example configuration of the proximal ends of the body sections 12a, 12b, wherein the body sections 12a, 12b are engaged by a proximal cap 119.

Implant 200 differs in that tip portion 205 and inner core portion 207 are provided and, in combination with proximal cap 119, provide a secure, unitary structure for implant 200. Tip portion 205 and core portion 207 are preferably formed of a relatively rigid material, such as a titanium alloy, or alternatively another suitable material. Pins 233 are preferably provided for interengaging distal portions of body halves 212a, 212b with core 207 and tip 205 by penetrating apertures 209 in core 207 and tip 205. The pins 233 are secured in a suitable manner, such as using clips 235, by laser welding, or other suitable attachment means.

Fig. 16 is a perspective view of another embodiment of an interspinous process implant 300 according to the present invention, the interspinous process implant 300 having a body 312, the body 312 having an outer surface including an unthreaded forward surface 315 and a distal end 305. Fig. 17 is a posterior (dorsal) view illustrating placement of an interspinous process implant 300 placed into the target interspinous process space 82, and fig. 18 is a partially exploded view of an alternative configuration for a distal tip portion of an interspinous process implant according to the present invention. The same elements as those described in connection with the above embodiments are denoted by the same reference numerals.

As discussed above, the advancement of the implant 300 differs from the threaded implants described herein in that the rotational movement does not advance the implant into the target interspinous process space, but instead must apply a lateral force.

The internal structure of implant 300 may include a core portion, as in the embodiment of fig. 14 and 15, and may be integral with tip portion 305, or alternatively, tip portion 305 may be formed separately and inserted into a component of implant 300. The proximal recess 3 may optionally be provided for engagement with an insertion device as described above.

While the apparatus and methods of the present invention have been shown and described with reference to selected preferred embodiments, it will be readily understood by those skilled in the art that variations and/or modifications of the embodiments may be made without departing from the spirit and scope of the invention.

Claims (14)

1. A spinal implant for insertion into an interspinous process space, comprising:

an elongate threaded body portion configured and dimensioned for percutaneous introduction into the interspinous process space and having a longitudinal axis, the body portion defining an inner lumen;

a pair of deployable engagement members mounted for cooperative rotation about a common axis extending transverse to the longitudinal axis of the body portion between a stowed position retracted within the interior cavity of the body portion and a deployed position extending from the interior cavity of the body portion to engage spinous processes, each engagement member including a central hub and a first bevel gear disposed along the common axis, wherein the first bevel gears of the two central hubs oppose each other within the interior cavity of the body portion along the common axis; and

an elongate drive shaft extending into said interior cavity and mounted for axial rotation about an axis thereof, said elongate drive shaft including a second bevel gear for operatively engaging with two opposed first bevel gears of said central hub, wherein axial rotation of said drive shaft about said axis causes said pair of deployable engagement members to rotate about said common shaft and thereby move between said stowed and deployed positions, wherein each engagement member is mounted for rotation along a spindle extending along said common shaft transverse to said axis.

2. A spinal implant as recited in claim 1, further comprising a drive assembly extending into the internal cavity of the threaded body portion for selectively moving the engagement members in unison from the stowed position to the deployed position.

3. A spinal implant as recited in claim 2, further comprising a device operatively associated with the drive assembly for selectively locking the engagement member in the deployed position.

4. A spinal implant as recited in claim 1, wherein the drive assembly includes a main drive shaft extending into the internal cavity of the body portion along a longitudinal axis of the body portion.

5. The spinal implant of claim 1, wherein each engagement member includes a pair of curved engagement arms extending radially outward from a central hub.

6. A spinal implant as recited in claim 5, wherein each engagement arm includes a distal claw portion having a plurality of teeth for engaging the spinous process.

7. A spinal implant as recited in claim 1, wherein the threaded body portion includes an outer profile that tapers axially inward in the distal nose portion of the threaded body portion, the outer profile being configured to gradually distract adjacent spinous processes during insertion of the implant into the interspinous process space.

8. A spinal implant as recited in claim 7, wherein threads are provided on the body portion and extend at least partially over the nose portion of the body portion.

9. A spinal implant as recited in claim 8, wherein the distal nose tapers axially inwardly relative to a central region of the body at an angle of about 30 degrees relative to a longitudinal axis thereof.

10. The spinal implant of claim 1, further comprising an inner core adapted and configured for hardening the spinal implant.

11. A spinal implant as recited in claim 10, wherein the core portion includes an integral tip portion disposed at a distal end of the implant.

12. A spinal implant as recited in claim 1, wherein the body portion includes a separately formed proximal portion formed of a material different from a material forming a central portion of the body portion, the proximal portion being formed of a metallic material, and the central portion of the body portion being formed of a polymeric material.

13. A spinal implant as recited in claim 1, a locking cap operatively associated with the long drive shaft and the body portion that are rotatable to selectively lock the engagement member in the deployed position.

14. A spinal implant as recited in claim 1, wherein each engagement member includes a pair of curved engagement arms extending radially outward from the central hub, each engagement arm including a distal claw portion having a plurality of distinct teeth for engaging spinous processes.