Spinal spacer for cervical and other vertebra, and associated systems and methods

Spinal spacers for cervical and other vertebra, and associated systems and methods are disclosed. A device in accordance with a particular embodiment includes a hook member having a hook positioned to extend in a first direction, a post carried by the hook member and extending axially in a second direction transverse to the first direction, and a cam surface carried by the hook member. An actuator device is movably engaged with the post, and a spinal spacer is pivotably coupled to one of the actuator device and the post. The spinal spacer is axially movable relative to the hook member and has a spacing element in contact with the cam surface to pivot outwardly away from the post as the actuator device moves.

TECHNICAL FIELD

The present disclosure is directed to spinal spacers for cervical and other vertebra, and associated systems and methods.

BACKGROUND

Spinal pain has long been a source of patient discomfort and a limitation on the patient's mobility and quality of life. Spine fusion (arthrodesis) is a procedure in which two or more adjacent vertebral bodies are fused together. It is one of the most common approaches for alleviating various types of spinal pain, particularly pain associated with one or more affected intervertebral discs. While spine fusion generally helps to eliminate certain types of pain, it has been shown to decrease function by limiting the range of motion for patients in flexion, extension, rotation, and lateral bending. Furthermore, the fusion creates increased stresses on adjacent non-fused vertebra, and accelerated degeneration of the vertebra. Additionally, pseudarthrosis (resulting from an incomplete or ineffective fusion) may not provide the expected pain relief for the patient. Also, the device(s) used for fusion, whether artificial or biological, may migrate out of the fusion site, creating significant new problems for the patient.

Various technologies and approaches have been developed to treat spinal pain without fusion in order to maintain or recreate the natural biomechanics of the spine. To this end, significant efforts are being made in the use of implantable artificial intervertebral discs. Artificial discs are intended to restore articulation between vertebral bodies so as to recreate the full range of motion normally allowed by the elastic properties of the natural disc. Unfortunately, the currently available artificial discs do not adequately address all of the mechanics of motion for the spinal column.

More recently, surgical-based technologies, referred to as “dynamic posterior stabilization,” have been developed to address spinal pain resulting from one or more disorders, particularly when more than one structure of the spine has been compromised. An objective of such technologies is to provide the support of fusion-based implants while maximizing the natural biomechanics of the spine. Dynamic posterior stabilization systems typically fall into one of two general categories: posterior pedicle screw-based systems and interspinous spacers.

Examples of pedicle screw-based systems are disclosed in U.S. Pat. Nos. 5,015,247; 5,484,437; 5,489,308; 5,609,636; 5,658,337; 5,741,253; 6,080,155; 6,096,038; 6,264,656; and 6,270,498. These types of systems typically involve the use of screws that are positioned in the vertebral body through the pedicle. Because these types of systems require the use of pedicle screws, implanting the systems is often more invasive than implanting interspinous spacers.

Examples of interspinous spacers are disclosed in U.S. Pat. Nos. Re 36,211; 5,645,599; 6,149,642; 6,500,178; 6,695,842; 6,716,245; and 6,761,720. The spacers, which are made of either a hard or a compliant material, are placed between the adjacent spinous processes of adjacent vertebra. While slightly less invasive than the procedures required for implanting a pedicle screw-based dynamic stabilization system, hard or solid interspinous spacers still require that the muscle tissue and the supraspinous and interspinous ligaments be dissected. Accordingly, in some instances, compliant interspinous spacers are preferred. However, the compliancy of such spacers makes them more susceptible to displacement or migration over time. One type of spacer developed by the assignee of the present application, and disclosed in U.S. patent application Ser. No. 11/314,712, is directed to rigid interspinous spacers that may be deployed from a posterior direction so as to reduce the amount of tissue dissected during implantation. These spacers also include deployable features that are stowed as the spacer is implanted to provide a low profile shape, and are then expanded once the spacer is implanted to provide the structure that stabilizes neighboring vertebra. Such devices have proven beneficial in many instances. However, there remains a need for reducing the invasiveness of an interspinous implant, while at the same time (a) reducing the likelihood for the implant to migrate, and (b) maintaining or improving the ability of the implant to provide suitable stability.

SUMMARY

The following summary is provided for the benefit of the reader only, and is not intended to limit in any way the invention as set forth by the claims. Aspects of the present disclosure are directed generally to spinal spacers for cervical and other vertebra, and associated systems and methods. A device for stabilizing a first vertebra relative to a second vertebra in accordance with a particular embodiment includes a hook member having a hook positioned to extend in a first direction, and a post carried by the hook member and extending axially in a second direction transverse to the first direction. The device can further include a cam surface carried by the hook member, and an actuator device moveably engaged with the post. The device can still further include a spinal spacer pivotably coupled to one of the actuator device and the post, and axially moveable relative to the hook member. The spinal spacer can have a spacing element in contact with the cam surface to pivot outwardly away from the post as the actuator device moves.

In further particular embodiments, the device can include one or more of several additional features, For example, the post can have internal threads and the actuator device can have external threads threadably engaged with the internal threads. In another embodiment, this arrangement can be reversed with the post having external threads and the actuator device having internal threads. The hook member can include a first portion and a second portion movably coupled to the first portion. At least one of the first and second portions is movable relative to the other between a stowed position and a deployed position, with the second portion extending in the first direction when in the deployed position. In another embodiment, the cam surface can be a first cam surface, and the device can further comprise a second cam surface carried by the hook member. The spacing element can be a first spacing element, and the spinal spacer can include a second spacing element in contact with the second cam surface to pivot outwardly away from the post as the actuator device moves axially. The first and second spacing elements can be pivotable relative to the post about a common axis, or about different axes.

Other embodiments of the disclosure are directed to methods for stabilizing a first vertebra relative to a second vertebra. A method in accordance with one embodiment includes inserting a hook member into an interspinous space between a first vertebra and a second, neighboring vertebra, with the hook member contacting the first vertebra, and with a post carried by the host member extending axially from the hook member. The method can further include moving an actuator relative to the post to pivot a spinal spacer outwardly away from the post and into contact with the second vertebra. The method can still further include continuing to move the actuator axially along the post while the hook member contacts the first vertebra and the spinal spacer contacts the second vertebra to force the first and second vertebra apart from each other.

In particular embodiments, the hook member can be inserted between the C3 and C4 cervical vertebra. The hook member can be inserted so as to project in an inferior direction, and can be inserted from a posterior position. In further particular embodiments, the spinal spacer can include spacing elements having spaced apart portions that are positioned laterally on opposite sides of the second vertebra to at least restrict lateral motion of the device relative to the first and second vertebra. The hook member can extend into a vertebral foramen of the first vertebra to at least restrict dorsal motion of the device.

DETAILED DESCRIPTION

Several embodiments of intervertebral spacers, systems, and associated methods are described below. The term “intervertebral” generally refers to the positional relationship between two neighboring vertebral bodies of a human spine. A person skilled in the relevant art will also understand that the devices, systems, and/or methods disclosed herein may have additional embodiments, and that embodiments of the devices, systems, and methods disclosed herein may not include all the details of the embodiments described below with reference toFIGS. 1A-17H.

For purposes of organization, the following discussion is divided into several sections, each generally associated with one of four particular embodiments of spinal spacer devices, or tools used to implant and/or deploy such devices. While the following discussion is divided to enhance the reader's understanding of each embodiment, it will be understood that aspects of each embodiment may be combined with other embodiments without departing from the scope of the present disclosure.

B. Spinal Spacer Device in Accordance with a First Embodiment

FIG. 1Ais a partially schematic side view of a spinal spacer device100configured in accordance with a first embodiment of the disclosure.FIG. 1Bis a top isometric view of the device100shown inFIG. 1A. Referring toFIGS. 1A and 1Btogether, the device100includes a hook member120having a hook121that projects along a first axis A1. The hook member120carries a post130that extends along a second axis A2, transverse to the first axis A1. The hook121is configured and positioned to fit within the vertebral foramen of a patient's vertebra. The device100further includes a spinal spacer110that moves between a stowed position, shown inFIGS. 1A and 1B, and a deployed position described further below with reference toFIGS. 1C and 3. An actuator device140moves the spinal spacer110from the stowed position to the deployed position.

In a particular embodiment, the spinal spacer110is pivotably attached to the actuator device140via a pair of pivot pins112. The actuator device140includes internal actuator threads141that are engaged with corresponding external post threads131of the post130. As the post130is rotated about the second axis A2, the actuator device140travels axially along the post130. The post130includes a tool grip portion132that allows a tool to grip and rotate the post130.

The spinal spacer110includes a pair of spacing elements113, each with a corresponding spacer surface111. The spacer surfaces111bear against corresponding cam surfaces123carried by the hook member120. For example, the hook member120can include oppositely facing sides122, each having a corresponding cam surface123against which the corresponding spacer surface111bears. As the actuator device140moves downwardly along the post130, each spacer surface111slides against the corresponding cam surface123, and the spinal spacer110pivots outwardly.

Referring now toFIG. 1B, each of the spacing elements113can have a wing-type shape, in a particular embodiment. The spacing elements113are held in a fixed position relative to each other by a saddle114. The saddle114and the spacing elements113include vertebral contact surfaces115that press against a superior vertebra when deployed. In the illustrated embodiment, the pivot pins112are co-linear so that the spacing elements113more in parallel planes.

FIG. 1Cillustrates the device100in the deployed configuration. To achieve the deployed configuration, a practitioner releasably engages a tool (not shown inFIG. 1C) with the tool grip portion132of the post130, e.g., by threading or clamping the tool onto the post130. The practitioner then rotates the post130counterclockwise, as indicated by arrow R1, which drives the actuator device140axially away from the tool grip portion132, as indicated by arrow T1. As the actuator device140moves axially, the spinal spacer110pivots about the pivot pins112, outwardly away from the post130as indicated by arrow R2. This motion is guided by the sliding contact between the spacer surfaces111and the corresponding cam surfaces123on each side122of the device100.

FIGS. 2 and 3are cross-sectional illustrations of the device100shown inFIG. 1A, taken substantially along line2-2ofFIG. 1A. As shown inFIG. 2, the internal actuator threads141of the actuator device140are threadably engaged with the external post threads131of the post130. The post130includes a retainer ring133that fits into a corresponding circumferential slot of the hook member120. Accordingly, the post130can rotate about the second axis A2relative to the hook member120.

FIG. 3illustrates the device100after the actuator device140has been rotated about the second axis A2(as indicated by arrow R1) so as to translate axially along the post130(as indicated by arrow T1). As the actuator device140moves along the second axis A2, the spinal spacer110pivots outwardly relative to the post130, as indicated by R2.

FIG. 4is a partially schematic, isometric illustration of a patient's spine190, illustrating particular cervical vertebrae C2, C3, C4, C5, and C6. Arrow S identifies the superior direction, arrow I identifies the inferior direction, arrow D identifies the dorsal direction, and arrow V identifies the ventral direction. Prior to inserting the device100, the practitioner makes a small incision in the patient's skin, along the midline193. The practitioner makes another incision through the posterior longitudinal ligament (not shown inFIG. 4) to access the vertebrae via a posterior approach. The device100is inserted in its stowed configuration between the third cervical vertebra C3 and the fourth cervical vertebra C4 in a dorsal-to-ventral direction, so that the hook121is received in the vertebral foramen192of the inferior C4 vertebra. The post130is then rotated, as discussed above, so as to rotate the spinal spacer110in a generally superior direction. The spinal spacer110(e.g., the spacing elements113and the saddle114) contact the superior C3 vertebra via one or more of the vertebral contact surfaces115. In a particular embodiment, the vertebral contact surfaces115engage with the spinous process191of the superior C3 vertebra. As the spinal spacer110rotates, it bears against the spinous process191of the superior C3 vertebra, while the hook member120bears against the inferior C4 vertebra, thus increasing the spacing between these two neighboring vertebra. At the same time, the hook121, which is positioned in the vertebral foramen192, prevents the device100from dislodging, or otherwise moving in a significant manner from the position illustrated inFIG. 4. Accordingly, the device100can provide pain relief for the patient by providing the proper spacing between the neighboring C3 and C4 vertebra, and can maintain its position at the spine190. In particular, the spacing elements113are positioned on opposing lateral sides of the spinous process191to restrict and/or prevent lateral motion of the spinal spacer110, while the hook121(in combination with the contact between the spacing elements113and the spinous process191) restricts and/or prevents motion of the device100in the dorsal direction D. The components of the device100can be formed from any of a variety of suitable biocompatible materials, including metals (e.g., stainless steel or titanium) and/or plastics, e.g., PEEK.

C. Spinal Spacer Device in Accordance with a Second Embodiment

FIG. 5is a partially schematic, top isometric illustration of a device500configured in accordance with a second embodiment of the disclosure. The device500can include a hook member520having a fixed hook521and carrying a post530having external post threads531. The hook member520can also include two cam surfaces523(one of which is visible inFIG. 5) rotatably secured to the hook member520via a cam pin524. Accordingly, the cam surfaces523can rotate relative to the hook member520. The device500can further include a spinal spacer510having two wing-shaped spacing elements513, one positioned on each of two opposing sides of the hook member520, and connected via a saddle514. The spinal spacer510is moved relative to the hook member520via an actuator device540that includes an actuator element542having internal actuator threads541threadably engaged with the external post threads531of the post530. The actuator element542fits within an annular opening of a collar543so as to rotate relative to the collar543. The collar543is coupled to the spinal spacer510with pivot pins512. Accordingly, a practitioner can engage flat external edges546of the actuator element542with an actuator tool (not shown inFIG. 5) and rotate the actuator element542about the second axis A2, as indicated by arrow R1. As the actuator element542rotates, it drives the collar543downwardly as indicated by arrow T1. Spacer surfaces511of the spacing elements513bear against and rotate the corresponding cam surfaces523, causing the spinal spacer510to rotate outwardly as indicated by arrow R2. It is expected that the ability of the cam surfaces523to rotate relative to the hook member520can reduce the friction between the cam surfaces523and the spacing elements513, thus enhancing the mechanical efficiency with which the spinal spacer510is deployed, and/or reducing the likelihood for these components to bind or jam during operation.

FIG. 6is a top isometric view of the device500shown inFIG. 5, with the spinal spacer510moved to its deployed position. Accordingly, the actuator element542has moved downwardly along the post530, pushing the collar543downwardly as well. The spacing elements513have rotated outwardly as they bear against and rotate the corresponding cam surfaces523.

FIG. 7is a partially schematic, isometric, exploded view of components forming the device500in accordance with an embodiment of the disclosure. As shown inFIG. 7, the hook member520and the post530are fixed relative to each other. The hook member520includes a cam pin hole529that receive the cam pin524so that the cam pin524can rotate relative to the hook member520. The cam pin524includes a head525with an outer cylindrical surface that forms one of the cam surfaces523. The cam pin524is attached to a keeper526having an outer cylindrical surface that forms the opposite cam surface523. The collar543includes a collar opening545which receives the actuator element542. Once the actuator element542is inserted into the collar543, a retaining ring533is attached to the bottom of the actuator element542to capture the collar543between the retaining ring533and the actuator element542. The actuator element542is then threaded onto the post threads531of the post530, and the spinal spacer510is attached to the collar543. The spinal spacer510includes holes515that are aligned with corresponding collar holes544in the collar543. During assembly, the pivot pins512are inserted through the holes515in the spinal spacer510and attached to the collar543via the collar holes544. Accordingly, the spinal spacer510can pivot outwardly relative to the collar543.

FIG. 8is a partially schematic, side view of the patient's spine190and skull189. The device500has been inserted between the third and fourth cervical vertebra C3, C4 and deployed in the manner described above so as to increase or at least maintain the spacing between these two vertebra. The functions provided by the hook member520, the hook521, and the spinal spacer510are generally similar to those described above with reference to the corresponding elements shown inFIGS. 1A-4.

D. Spinal Spacer Device in Accordance with a Third Embodiment

FIG. 9Ais a partially schematic side view of a device900configured in accordance with a third embodiment of the disclosure, and shown in its stowed configuration.FIG. 9Bis a side view of the device900shown in its deployed configuration. Referring toFIGS. 9A and 9Btogether, the device900includes a hook member920carrying a hook921. The hook member920can have a distal end927with a generally pointed shape to aid in inserting the device900into the interspinous space between neighboring vertebra. The hook member920carries a post930having external post threads931that engage with internal threads of an actuator element942. The actuator element942is slidably positioned within a collar943to form an actuator device940that operates in a manner generally similar to the actuator device540described above. A spinal spacer910is pivotably attached to the collar943via a pair of pivot pins912, one of which is visible inFIG. 9A. The spinal spacer910includes two spacing elements913, one of which is visible inFIG. 9A, connected to each other with a saddle914. Each of the spacing elements913has an aperture916(e.g., a generally slot-shaped aperture) that receives a cam pin924and associated cam surface923when the spinal spacer910is stowed. The aperture916is bounded in part by a spacer surface911that bears against the corresponding cam surface923. The apertures916allow the corresponding spacing elements913to hook around the corresponding cam pins924during insertion, reducing or eliminating the likelihood for the spacing elements913to deploy inadvertently during insertion.

InFIG. 9B, the spinal spacer910has been deployed by rotating the actuator element942relative to the post930, thus driving the collar943in a generally ventral/superior direction, which forces the spinal spacer910to pivot in a generally superior/dorsal direction as the spacer surfaces911bear against the corresponding cam surfaces923. As discussed above, the hook member920and the spinal spacer910can accordingly space neighboring vertebra apart from each other, while the hook921and spinal spacer910prevent or at least restrict motion of the device900relative to the patient's spine.

FIGS. 10A and 10Billustrate the device900from a generally ventral position in the stowed configuration (FIG. 10A) and in the deployed configuration (FIG. 10B). As shown inFIGS. 10A and 10B, the spacing elements913are not positioned parallel to each other, but instead splay outwardly relative to each other in a generally superior direction. The pivot pins912are not collinear and, accordingly, the spacing elements913rotate in non-parallel planes. This arrangement is expected to more closely track the shape of the dorsal side of the superior vertebra, which also splays outwardly around the vertebral foramen. Accordingly, it is expected that this arrangement will provide more contact and/or more secure contact between the device900and the vertebra between which the device is placed. In order to accommodate the relative motion between the spacing elements913as the spinal spacer910is deployed, the saddle914can include a centrally located saddle element919, which is supported in place by two saddle pins918(FIG. 10B), each of which extends inwardly from a corresponding one of the spacing elements913. As the spacing elements913pivot, the saddle pins918can move outwardly within corresponding apertures in the saddle element919, so that the saddle element919does not cause the spinal spacer910to bind as it pivots. The saddle element919and the saddle pins918can be shaped and configured so that the saddle element919remains in a central location as the spacing elements913move. For example, each of the saddle pins918can terminate in a spherical bulb or ball. Accordingly, the saddle element919can aid in centering the device900on the midline of the patient's spine, despite vertebral shapes that may vary from one patient to another.

As is also shown inFIGS. 10A and 10B, the post930can include an alignment slot934, and the actuator element942can include outwardly facing edges946. The alignment slot934can be used to align an actuation tool relative to the post930, and the edges946can engage with the actuation tool to facilitate rotating the actuator device942relative to the post930. Further details of this operation are described below with reference toFIGS. 11A-11E.

E. Actuation Tool for Use with a Device in Accordance with the Third Embodiment

FIG. 11Ais an isometric, partially schematic view of an actuator tool1150configured to insert and deploy a spinal spacer device, for example, the device900described above with reference toFIGS. 9A-10B. In one aspect of this embodiment, the actuator tool1150includes a shaft assembly1151, a handle1152, a first knob1153, and a second knob1154. The handle1152can be elongated along a handle axis A4for ease of operation, and to facilitate aligning the tool1150. The handle1152, the first knob1153, and the second knob1154are connected to and operate concentrically arranged components of the shaft assembly1151, as described further below.

FIG. 11Bis a partially schematic, cross-sectional illustration of the actuator tool1150, taken substantially along line11B-11B ofFIG. 11A.FIG. 11Cis a partially schematic, cross-sectional illustration of the actuator tool1150, taken substantially along line11C-11C ofFIG. 11A. Referring toFIGS. 11B and 11Ctogether, the shaft assembly1151includes an actuator shaft1157connected to the second knob1154and an attachment shaft1156positioned annularly inwardly from the actuator shaft1157and connected to the first knob1153. The shaft assembly1151further includes an alignment shaft1155positioned annularly inwardly from the attachment shaft1156and attached to the handle1152. Accordingly, when a practitioner rotates the handle1152, the alignment shaft1155rotates. When the practitioner rotates the first knob1153, the attachment shaft1156rotates, and when the practitioner rotates the second knob1154, the actuator shaft1157rotates. Referring toFIG. 11B, the attachment shaft1156includes internal threads1159for attaching to the device900, and the alignment shaft1155includes an alignment tab1158for aligning the actuator tool1150properly with the device900. These features are described further below with reference toFIG. 11D.

FIG. 11Dis a bottom isometric view, looking upwardly at the distal end portion of the shaft assembly1151described above with reference toFIGS. 11A-11C. As shown inFIG. 11D, the alignment tab1158is elongated along a tab axis A3and extends outwardly from a lower portion of the alignment shaft1155. The attachment shaft1156includes internal threads1159and can rotate relative to the alignment shaft1155. The actuator shaft1157includes inwardly facing engagement surfaces1160and can rotate relative to both the attachment shaft1156and the alignment shaft1155.

The operation of the actuator tool1150is now described with reference toFIGS. 11D and 11E, and also with reference to the device900upon which it operates, which was described above with reference toFIGS. 9A-10B, and which is shown again inFIG. 11F. When the tool1150is in a starting configuration, the tab axis A3of the alignment tab1158shown inFIG. 11Dis aligned parallel with the handle axis A4of the handle1152shown inFIG. 11E. Accordingly, the operator can align the handle axis A4with the alignment slot934of the device900shown inFIG. 11F. Doing so will automatically align the alignment tab1158(FIG. 11D) with the alignment slot934of the device900(FIG. 11F). With the alignment tab1158placed within the alignment slot934, the practitioner rotates the first knob1153, thereby engaging the internal threads1159of the attachment shaft1156with the external post threads931of the post930. This operation releasably secures the device900to the actuator tool1150, as is shown inFIG. 11E. This operation also advances the engagement surfaces1160of the actuator shaft1157axially so that they are positioned adjacent to the corresponding edges946of the actuator device940. Accordingly, when the operator rotates the second knob1154, the attached actuator shaft1157rotates the actuator element942. The practitioner continues to rotate the second knob1154to advance the actuator element942along the post930, thereby deploying the spinal spacer910to the deployed position shown inFIG. 9B.

F. Spinal Spacer Device in Accordance with a Fourth Embodiment

FIGS. 12A and 12Bare partially schematic, side elevation views of a device1200configured in accordance with a fourth embodiment of the disclosure, shown in a stowed configuration (FIG. 12A) and a deployed configuration (FIG. 12B). In one aspect of this embodiment, the device includes a deployable hook. In another aspect of this embodiment, the post is internally threaded and the actuator is externally threaded. Further details of these features are described below.

Referring toFIGS. 12A and 12Btogether, the device1200includes a hook member1220having a hook1221that is folded (e.g., generally parallel to the second axis A2) when the device100is in its stowed configuration. The hook1221is unfolded so as to extend along the first axis A1when the device1200is deployed. The hook member1220has a fixed position relative to a generally cylindrical housing1280, which has a housing aperture1282(e.g., a generally cylindrical cavity) and a housing cap1281over the end of the housing aperture1282. An actuator device1240(visible inFIG. 12B) rotates within the housing1280to deploy a spinal spacer1210.

The spinal spacer1210can include two spacing elements1213(one is visible inFIGS. 12A,12B) pivotably coupled to the actuator device1240via corresponding pivot pins1212. Each spacing element1213has a spacer surface1211that bounds, in part, an aperture1216. Each spacer surface1211bears against a corresponding cam surface1223which can rotate relative to the hook member1220. In a particular embodiment, the cam surface1223is carried by a cam pin1224which is attached to an annular keeper1226to limit the lateral motion of the corresponding spacing element1213. In the stowed configuration, the spacing element1213is generally aligned with the second axis A2, and the cam surface1223is received in the aperture1216. When the device1200is changed to the deployed configuration (shown inFIG. 12B), the hook1221deploys outwardly, and the spacing elements1213deploy outwardly, generally in the opposite direction.

FIGS. 13A and 13Billustrate the device1200during two steps in an overall component assembly process. Referring first toFIG. 13A, the spacing elements1213of the spinal spacer1210are pivotably connected to the post1230with corresponding pivot pins1212. The spacing elements1213are non-parallel to each other, and splay outwardly as they deploy, in a manner generally similar to that described above with reference toFIGS. 10A-10B. The post1230, which has internal post threads1231, is inserted into the housing aperture1282, as indicated by arrow T3.

Referring now toFIG. 13B, the post1230has been inserted into the housing aperture1282. The actuator device1240, with its external actuator threads1241, is then threadably engaged with the post threads1231. The actuator device1240includes an alignment slot1247for alignment with an actuation tool, described below. After the actuator device1240has been threadably engaged with the post1230, the housing cap1281is positioned over the actuator device1240, and is sealed to a corresponding cap lip1284extending upwardly from the housing1280(e.g., with a thermal weld or an adhesive). Accordingly, the actuator device1240is captured within the housing1280, but is free to rotate relative to the housing1280. A cutout1285in the housing cap1281is used to align an insertion tool, and an engagement slot1283receives the tool, as described later with reference toFIG. 17C.

FIGS. 14A and 14Bare partially schematic, cross-sectional illustrations of the assembled device1200in a stowed configuration (FIG. 14A) and a deployed configuration (FIG. 14B). Referring toFIGS. 14A and 14Btogether, the device1200is changed from the stowed configuration to the deployed configuration by inserting a tool having a flat blade (generally like a standard screwdriver) into the tool slot1247and rotating the tool about the second axis A2, as indicated by arrow R1. As the actuator device1240rotates about the second axis A2, it drives the post1230downwardly as shown inFIG. 14B. The post1230includes a hook actuator1235that is received in a hook slot1228of the hook1221. As the post1230and the hook actuator1235move downwardly, the hook actuator1235drives the hook1221to rotate outwardly to its deployed position, shown inFIG. 14B. At the same time, the spacing elements1213(one of which is visible inFIGS. 14A and 14B) rotate outwardly to their deployed positions as they pivot relative to the post1230about the pivot pins1212(FIG. 12B), and slide relative to the cam surfaces1223(FIG. 12B). In one embodiment, the motion of the spacing elements1213can be delayed relative to the motion of the hook1221because part of the spacer surface1211(best shown inFIG. 12A) is aligned generally parallel to the second axis A2. Accordingly, the spacing elements1213can remain aligned with the second axis A2until the upper surface of the aperture1216(shown sloping slightly upwardly and to the right inFIG. 12A) engages the cam surface1223. In other embodiments, the motion of the hook1221and the spacing elements1213can be simultaneous, or can have other timing sequences.

FIGS. 15A and 15Billustrate the device1200in the stowed and deployed configurations, respectively, from a posterior or dorsal position. As shown inFIGS. 15A and 15B, the spacing elements1213pivot in a generally superior direction S while the hook1221deploys in a generally inferior direction I, as the actuator device1240is rotated in the direction indicated by arrow R1. The spinal spacer1210can include a saddle1214, including a saddle element1219supported by corresponding saddle pins1218. As discussed above with reference toFIGS. 9A-10B, the saddle pins1218can retain the saddle1214in a central position, while partially withdrawing from or otherwise moving relative to the saddle element1219as the spacing elements1213splay outwardly during deployment.

G. Insertion Tool for Use with a Device in Accordance with the Fourth Embodiment

FIG. 16Ais a partially schematic, side isometric view of a cannula1673and an associated cannula insertion tool1670. The cannula1673provides a temporary channel into the patient's intervertebral space for inserting a spinal spacer device, such as the device1200described above with reference toFIGS. 12A-15B. The cannula insertion tool1670includes features for inserting the cannula1673, after which it can be removed to allow the spinal spacer device to be inserted through the cannula1673. The cannula1673can include a handle1674and a lumen1675that extends from a proximal opening1665located at the handle1674to a distal opening1676. The cannula1673can further include roughness features1666toward the distal opening1676that aid in holding the cannula1673in place, and an alignment mark1671bfor alignment with the cannula insertion tool1670and/or other elements.

The cannula insertion tool1670can include a penetrating tip1672and a corresponding alignment mark1671athat the practitioner aligns with the alignment mark1671bof the insertion tool1670. In operation, the practitioner aligns the two marks1671a,1671band inserts the penetrating tip1672into the lumen1675through the proximal opening1665. The practitioner moves the cannula insertion tool1670through the lumen1675, until the penetrating tip1672extends outwardly from the distal opening1676. In preparation for inserting the cannula1673, the practitioner can make an incision through the patient's skin, and can make a further incision through the patient's spinous ligament. Referring now toFIG. 16B, with the insertion tool1670inserted in the cannula1673, and the penetrating tip1672extending outwardly from the cannula1673, the practitioner drives the penetrating tip1672between neighboring vertebra (e.g., cervical vertebra C3 and C4), to lodge the cannula1673between these vertebra. The practitioner then removes the insertion tool1670from the cannula1673, leaving the cannula1673in place.

FIG. 17Aillustrates a device insertion tool1777, which can be releasably engaged with a spinal spacer device (e.g., the device1200described above) and then inserted into the cannula1673(FIG. 16B) to deploy the device between neighboring vertebra. In a particular embodiment, the device insertion tool1777includes an alignment mark1771which is aligned with a corresponding alignment mark1671bof the cannula1673. The device insertion tool1777includes an internal shaft1769which is rotatably controlled by a handle1774. The distal end of the shaft1769includes a head1768that engages the device1200. The distal end of the shaft1769has multiple shaft sections1763(e.g., four). The shaft sections1763are separated by axial slots1762so that the shaft sections1763can flex outwardly relative to each other when the head1768engages the device1200. An external sleeve1779is positioned annularly around the shaft1769, and can slide down over the shaft sections1763to prevent the sections1763from flexing after the device1200is engaged. The sleeve1779is controlled by a locking knob1778.

FIG. 17Bis a partially schematic, isometric view of the distal end of the shaft1769shown inFIG. 17A, illustrating the head1768. The head1768can include multiple tabs1764(two are shown as a first tab1764aand a second tab1764b), each carried by a corresponding one of the sections1763. The tabs1764can engage with the spacer device, as described below with reference toFIG. 17C.

FIG. 17Cillustrates the head1768of the shaft1769, positioned adjacent to the spacer device1200. The first tab1764ais configured so that it can only be placed over the housing cap1281when it is properly aligned with a corresponding cutout1285in the housing cap1281. The second tab1764bis positioned opposite from the first tab1764a. In operation, the practitioner aligns the first tab1764awith the cutout1285and advances the head1768over the outwardly projecting portion of the housing cap1281, as indicated by arrow T2. The practitioner then rotates the shaft1769as indicated by arrow R4(e.g., by about 90°) so that the tabs1764a,1764benter corresponding engagement slots1283(one of which is visible inFIG. 17C) in the housing cap1281. As the tabs1764a,1764brotate around the squared-off portions of the housing cap1281, the shaft sections1763deflect outwardly and then inwardly until the tabs1764a,1764bsettle into the corresponding engagement slots1283. The sleeve1779(not visible inFIG. 17C) is then deployed over the shaft sections1763to prevent further flexing, as described below with reference toFIGS. 17F-17G.

FIG. 17Dillustrates the device insertion tool1777with the handle1774properly aligned with the device1200, just prior to engaging the head1768with the housing cap1281.FIG. 17Eillustrates the device insertion tool1777with the head1768engaged with the device1200. The practitioner has rotated the handle1774as indicated by arrow R5to seat the tabs1764in the corresponding engagement slots1283, as described above with reference toFIG. 17C. Accordingly, the main axis of the handle will be aligned with the patient's spine during insertion. The practitioner then moves the sleeve1779downwardly over the shaft1769to prevent the individual shaft sections1763from moving radially apart from each other.FIG. 17Fillustrates a process for moving the sleeve1779in accordance with a particular embodiment. In this embodiment, the practitioner rotates the locking knob1778clockwise as indicated by arrow R6, then slides the locking knob and the sleeve1779toward the device1200as indicated by arrow T3, and then secures the locking knob1778in position by rotating the locking knob1778in a counterclockwise direction, indicated by arrow R7.FIG. 17Gillustrates further details of this operation. The locking knob1778includes a projection that is received in a corresponding guide slot1767, which guides the rotational and translational motion described above with reference toFIG. 17F.

FIG. 17Hillustrates the device insertion tool1777, with the device1200releasably attached to it, inserted into and through the cannula1773, just prior to being deployed. At this point, the device1200is positioned between the two vertebra (not shown inFIG. 17H) positioned on each side of the cannula1773. The practitioner then inserts a screwdriver-like actuator tool through an axially extending opening in the device insertion tool1777, to engage with the tool slot1247(FIG. 17C) of the device1200. The practitioner then deploys the spinal spacer1210in the manner described above with reference toFIGS. 14A-15B. To complete the procedure, the practitioner removes the actuator tool, then removes the device insertion tool1777(by reversing the steps described above with reference toFIGS. 17C-17G), then removes the cannula1773, sutures the spinous ligament, and closes the skin over the insertion site.

One feature of at least some of the foregoing embodiments is that the device can include a hook member that enters the vertebral foramen to prevent or at least restrict motion of the spinal spacer device after it has been implanted. Accordingly, the likelihood that the device will be dislodged after implantation can be reduced when compared with existing devices.

Another feature of at least some of the embodiments described above is that the spinal spacer device can be inserted into the patient from a posterior direction. An advantage of this feature is that it is expected to be less invasive than procedures in which a spinal spacer is delivered laterally.

Still another feature of at least some of the foregoing embodiments is that elements of the device can be stowed as the device is implanted, and then deployed when the device reaches the implantation site. For example, the hook and/or the spinal spacer elements can be stowed during implantation and then deployed once the device is in position. An advantage of these features, alone or in combination, is that the device can be made more compact during insertion, resulting in a less invasive insertion process. At the same time, the device can include deployable features that securely and stably keep the device in position once it is implanted.

Yet another feature of at least some of the foregoing embodiments is that the actuator can be threadably engaged with the post. One advantage of this feature is that the threads between these two elements can have a relatively fine pitch, allowing the practitioner to adjust the spacing between neighboring vertebra with greater precision than is available with at least some existing devices. For example, in a particular embodiment, the practitioner can track the number of rotations he or she provides to the actuator tool, and can directly correlate this number with the deflection provided to the spinal spacer. Another expected advantage of this arrangement is that the practitioner can adjust the threaded interface between these elements in either direction, with relative ease. Accordingly, if the practitioner overdeploys the spinal spacer, he or she can partially retract the spinal spacer by simply rotating the actuator tool in the opposite direction. Still another advantage of this feature is that it is expected that the mechanical resistance of the threaded arrangement will prevent or at least resist relative motion between the post and the actuator after the device has been implanted. Accordingly, the device is less likely to retract or partially retract, or otherwise become dislodged once implanted. In particular embodiments, the actuator and post can be secured relative to each other after implantation, for example, with an adhesive or mechanical insert.

From the foregoing, it will be appreciated that specific embodiments of the disclosure have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. For example, certain aspects of the spinal spacer devices and associated tools may be modified in further embodiments. Such modifications can include changing the shape of the spacing elements, and/or the hook to accommodate particular patient physiologies. In other embodiments, the post and actuator can have arrangements other than a male thread/female thread arrangement, for example, a rack and pinion arrangement. In still further embodiments, the hook can project into the vertebral foramen of the superior vertebra, and the spinal spacer can engage the inferior vertebra.

Certain aspects of the disclosure described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, procedures and tools described above for inserting the device shown inFIGS. 12A-15Bcan be used, either as is, or modified, to insert other devices described herein. While the spinal spacer devices are illustrated as being inserted between the C3 and C4 vertebra, the devices or other embodiments of the devices can be inserted between other cervical or non-cervical vertebra. Further, while advantages associated with certain embodiments have been described in the context of those embodiments, other embodiments may also exhibit such advantages. Not all embodiments need necessarily exhibit such advantages to fall within the scope of the present disclosure. Accordingly, the disclosure can encompass other embodiments not expressly shown or described herein.