Occipital and cervical stabilization systems and methods

A spinal stabilization system comprises an elongated stabilization device including a curved configuration along a longitudinal axis thereof. The elongated stabilization device includes a length and cross-section sized for positioning through a pathway formed from an opening in a lateral mass of a first vertebra and into the first vertebra, through the facet joint formed by adjacent articular surfaces of the first vertebra and an adjacent bony structure, and into the adjacent bony structure. Instruments can be provided to form the pathway and insert the stabilization device into the pathway.

BACKGROUND

Various devices have been employed for fixation of the cervical vertebrae, and for fixation of the occiput with the cervical vertebrae. Posterior systems include a plate attached to the occiput with screw fixation, typically in the posterior-medial section of the occiput. A rod extends from the plate and along the C1, C2 and even C3 vertebrae for attachment thereto to provide a platform for fixation. Spanning of multiple levels of the cervical spine results in fixation of these levels. However, for certain procedures fixation at one or more of these spanned levels of the cervical spine may not be desired.

In the cervical region, anatomical considerations make it difficult to utilize a trans-articular screw. Furthermore, to achieve the desired alignment for a trans-articular screw, long incisions in the tissue along the cervical region of the spine are necessary. This provides the exposure required for a proper trajectory for the surgical approach to insert the screw through the articular joint.

Sub-occipital and sub-laminar wiring techniques have also been employed to stabilize the cervical region during fusion. Wiring techniques can result in complications with intradural penetration. Plating systems lie very close to the surface of the skin and can require bi-cortical placement of screws.

Systems for occipital and cervical stabilization are needed that provide adequate stabilization, can be targeted to the vertebral level or levels in which stabilization is desired, and reduce the invasiveness and complexity of the procedure.

SUMMARY

According to one aspect, a spinal stabilization system comprises an elongated stabilization device with a curved configuration along a longitudinal axis thereof. The stabilization device includes a length and cross-section sized for positioning through a pathway. The pathway is formed from an opening in a lateral mass of a first vertebra and into the first vertebra, through a facet joint formed by adjacent articular surfaces of the first vertebra and an adjacent bony structure, and into the adjacent bony structure.

According to another aspect, a spinal stabilization system comprises an elongated stabilization device with a curved configuration along a longitudinal axis thereof. The stabilization device includes a length and cross-section sized for positioning through a pathway formed through a joint between adjacent bony structures. The stabilization device includes an elongated outer member and an elongated inner member. The inner member is movable in the outer member between a first position wherein the stabilization device includes a reduced profile for insertion in the pathway and a second position wherein the inner member engages the outer member to provide at least a portion of the stabilization device with an enlarged profile to engage bony tissue along the pathway.

According to a further aspect, a method for stabilizing adjacent bony structures includes: forming an opening in a lateral mass of a cervical vertebra; forming a curved pathway from the opening and through a facet joint formed by adjacent articular surfaces of the cervical vertebra and an adjacent bony structure; and positioning an elongated stabilization device through the opening and along the curved pathway to link the cervical vertebra with the adjacent bony structure.

These and other aspects will also be apparent from the following description.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the illustrated embodiments thereof and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications in the invention, and any such further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.

Stabilization of adjacent vertebrae is provided with placement of a stabilization device through adjacent articular surfaces of bony structures, such as the cervical vertebrae and occiput, linking one or more of the vertebrae and/or occiput to one another. The stabilization device includes a curved profile along its longitudinal axis to facilitate its placement along a pathway that includes a joint formed by adjacent articular surfaces while minimizing the invasiveness of the procedure required to accommodate placement of the stabilization device. Furthermore, placement of the stabilization device through the joint reduces moment loads on the stabilization device since the stabilization device is located along or adjacent to an axis of movement of the adjacent bony structures. The systems and procedures contemplate application in the cervical region of the spine and the occiput, although application in other regions of the spine are also contemplated. Stabilization can be targeted to the vertebral level or levels desired while motion of the adjacent, non-instrumented vertebral level or levels can be preserved. Stabilization can be completed along one or more vertebral levels in the same surgical procedure with one stabilization device, or with multiple stabilization devices. It is further contemplated that multiple stabilization devices can be positioned to stabilize a particular vertebral level.

Referring toFIG. 1, there is shown a spinal column segment10including the upper cervical vertebra C1 designated at12and the next lower cervical vertebra C2 designated at30. Occiput50, shown inFIG. 2, resides at the superior end of C1 vertebra12. Occiput50includes foramen magnum52and occipita condyles54on opposite sides of foramen magnum52.

Occipita condyles54are supported on and form a joint with respective ones of the superior articular facets18of C1 vertebra12, shown in further detail inFIG. 3, a superior view, and inFIG. 4, an inferior view. The skull can articulate relative to C1 vertebra12about the joints formed between occipita condyles54and superior articular facets18. C1 vertebra12includes posterior tubercle14and anterior tubercle26. Laminae16extend from posterior tubercle14to respective lateral masses of the C1 vertebra12. C1 vertebra12further includes transverse processes20and transverse foramen22. Inferior articular facets24are supported on superior articular facets44of C2 vertebra30.

C2 vertebra30is further shown inFIG. 5in a posterior view, and includes odontoid process32along an anterior portion thereof. Spinous process38projects posteriorly from vertebra C2 and laminae42extend in opposite directions therefrom to lateral masses40. Lateral masses40include a bony structure that forms superior articular facet44and inferior articular facet46, which is oriented anteriorly for engagement with the superior articular facet of the C3 vertebra (not shown.)

A pair of insertion pathways for receiving stabilization devices is shown inFIGS. 1-5. A first insertion pathway60is provided from C2 vertebra30, through C1 vertebra12, and into occiput50. A second insertion pathway70is shown from C1 vertebra12to occiput50. It should be understood that surgical procedures are contemplated which employ identical insertion pathways60or70on each side of spinal column segment10and occiput50; or a single insertion pathway60or70on one of the sides of spinal column segment10and occiput50. It is further contemplated that insertion pathway60can terminate at a blind end in C1 vertebra12to provide stabilization only for the C1-C2 vertebral level. In any form, insertion pathways60,70extend through the adjacent articulating surfaces of the facet joints to provide an avenue for insertion of a stabilization device. Insertion pathways60,70are curved to accommodate the proper positioning of the stabilization devices relative to the anatomy of spinal column segment10and occiput50, and to minimize the invasiveness of the procedure into the tissue in the approach to spinal column segment10for formation of pathways60,70.

In the illustrated embodiment, first insertion pathway60includes an inferior opening62in lateral mass40of C2 vertebra30. Insertion pathway60extends from opening62through the bony structure of C2 vertebra30, where it opens at the superior articular facet44of C2 vertebra30. Insertion pathway60further extends through the facet joint into the inferior articular facet24of C1 vertebra12. Insertion pathway60can terminate at a blind end in the lateral mass of C1vertebra12for a single level stabilization of the C1 and C2 vertebrae12,30. In a further form, insertion pathway60can continue through the lateral mass of C1 vertebra12and through opening64at the superior articular facet18of C1 vertebra12. Insertion pathway60extends through the joint between C1 vertebra12and occiput50into the aligned receptacle66formed in occiput condyle54, where insertion pathway60terminates in a blind end.

In another embodiment, second insertion pathway70includes an inferior opening72in lamina16of C1 vertebra12. Second insertion pathway70extends from opening72through the bony structure of C1 vertebra12, where it opens at opening74in the superior articular facet18of C1 vertebra12. Insertion pathway70extends through the joint between occiput50into the aligned receptacle76in occiput condyle54, where insertion pathway70terminates in a blind end.

Referring now toFIG. 6, there is shown one embodiment of a stabilization device100for insertion in a pathway60,70. Stabilization device100includes a body102having a length extending along and curved along longitudinal axis104. Body102extends between a leading end106and a trailing end108. The curvature of body102between ends106,108can be defined by a radius R to facilitate insertion along a pathway defined by an arc A formed about radius R. In the illustrated embodiment, stabilization device100is a rod or shaft curved at a single radius R along arc A, and longitudinal axis104is co-linear with arc A. However, it is contemplated that stabilization device100can have a curvature that differs from arc A, or can have a curvature that varies or is compounded along its length.

In the illustrated embodiment, body102can include a circular cross-sectional shape; however, other shapes are also contemplated, including oval, polygonal, square, rectangular, non-circular, and irregular cross-sections, for example. The cross-section can be of uniform dimension along the length of body102, or can be tapered, stepped or otherwise varied to provide regions of greater and lesser dimension. Body102can be sized with a cross-section along at least a portion of the length thereof that is slightly greater than size of pathway60,70to provide frictional engagement with the surrounding bony tissue. Body102can also be provided with a cross-sectional size that is about the same or less than the opening formed by pathway60,70. In still another form, body102can be provided with a cross-section, such as a non-circular cross-sectional shape, that differs from the shape of the opening formed by pathway60,70. Body102can include surface features extending along body102and/or transversely to longitudinal axis104that enhance engagement of body102with the adjacent bony tissue. Examples of surface features include knurlings, teeth, barbs, spikes, ridges, and/or grooves.

Stabilization device100can be rigid or semi-rigid, at least during placement, to facilitate placement through the pathways60,70by pushing on the trailing end thereof to advance the leading end. In another form, body102is flexible and is mounted to a carrier for insertion through pathways60,70. Body102can be solid, or can include any one or combination of fenestrations, dimples, longitudinal passages, transverse passages, and through-holes. Body102can be comprised of a metal or metal alloy, such as stainless steel, titanium, or other suitable biocompatible metal material. In other forms, stabilization device can be an elastic or super-elastic member made from a super-elastic metal alloy, such as nitinol, or a polymer material.

Stabilization device100can be in the form of a cable, band or artificial ligament made from any suitable bio-compatible material, and employed to tether the bony structures to one another through pathways60,70. In still further forms, body102can be comprised entirely or partially of resorbable material, or of porous material, to facilitate integration with the bony tissue surrounding body102. In still a further form, body102can be comprised of ceramic material, or bone material, for example. Body102can be coated, impregnated, or otherwise be a carrier for bone growth promoting material and/or therapeutic substances to promote or provide bone growth and healing. In another form, body102is formed by placing a material in a first form in the formed pathway60,70, and then allowing the material to cure in situ to form a stabilization device.

InFIG. 7there is shown another embodiment stabilization device120, which can include any of the features and forms discussed above with respect to stabilization device100. Stabilization device120includes an outer member122and an inner member150. Outer member122includes a passage130extending along a longitudinal axis124thereof. Outer member122includes a leading insertion end126and an opposite trailing end128. Passage130opens at trailing end128, and at least extends adjacent to leading end126. In the illustrated embodiment, passage130opens at leading end126.

Inner member150includes an elongated body152extending between a leading end nose156and an intermediate nose162along longitudinal axis154. An enlarged trailing end portion160extends from intermediate nose162. Intermediate nose162includes a tapered surface profile that transitions between enlarged trailing end portion160and body152. In the illustrated embodiment, a thread pattern164is formed along a portion of the length of body152adjacent intermediate nose162. Leading end nose156includes an enlarged configuration relative to body152, and includes tapered surfaces158extending therefrom toward the tip of inner member150.

In use, inner member150is positioned in passage130of outer member122. Outer member122can include thread pattern144along an inner wall surface thereof configured to threadingly engage thread pattern164of inner member150, although non-threaded engagement between inner member122and outer member150is also contemplated. In the insertion configuration, as shown inFIG. 8, leading end nose156is positioned adjacent to leading end126of outer member122such that nose156is received in passage130adjacent a tapered leading end portion133thereof. Similarly, enlarged trailing end portion160is received in an enlarged trailing end portion131of passage130. In this configuration, stabilization device120includes a reduced profile along the length thereof to facilitate insertion into pathways60,70.

When stabilization device120has been inserted in one of the pathways60,70, inner member150can be advanced in outer member122such that leading end nose156contacts tapered inner surface portion148of outer member122along leading end portion133of passage130as shown in dashed lines inFIG. 8. Leading end portion126includes a slot or relief136that provides at least two fingers132,134. Leading end nose156provides a wedge-effect and pushes on inner surface portion148to bias fingers132,134away from one another and to deploy end nose156into firm engagement with the adjacent bony tissue of the pathway60,70into which stabilization device120has been positioned.

Similarly, trailing end128of outer member122includes a slot or relief142that provides at least two fingers138,140adjacent trailing end portion128. The tapered surface of intermediate nose162contacts and pushes on intermediate tapered portion146of passage130, providing a wedge effect that pushes fingers138,140away from one another as shown in dashed lines inFIG. 8. Trailing end128is then deployed into engagement with the adjacent bony tissue of the pathways60,70into which stabilization device120has been positioned.

In embodiments where inner member150is not threadingly engaged to outer member122, inner member150can be configured to move longitudinally within outer member122to deploy one or more portions of it into engagement with the adjacent bony tissue. For example, inner member150can interface with outer member150via a snap fit, interference fit or other suitable coupling arrangement permitting longitudinal reciprocal movement of inner member150relative to outer member122.

Still other stabilization device embodiments are contemplated. For example, inFIG. 11there is shown stabilization device250including a curved body252and a leading end254. Leading insertion end254includes a threaded nose configuration for engaging the adjacent bony tissue. Body252is sufficiently flexible and sized to permit rotation of body252to rotate leading insertion end254. In another form, body252includes a central passage opening to leading insertion end254. Leading insertion end254is rotatably coupled to body252. A flexible driver can be positioned through the passage.

In another embodiment shown inFIG. 12, a stabilization device270is provided that includes a curved body272extending between a leading insertion end274and a trailing end276. Each of the ends274,276is provided with a threaded nose arrangement for engagement with the adjacent bony tissue. The pitch of the nose threads can be the same at each end, or can be different to provide either a distraction or compression effect as the threaded noses are engaged with the adjacent bony structure. A central lumen or passage can be provided through body272to leading insertion end274to receive a driver instrument. Body272can also be flexible between ends274,276and sized to permit rotation of body252to rotate leading insertion end254.

InFIG. 13another embodiment stabilization device290is provided that includes a curved body292and a threaded leading insertion end294. The trailing end296includes an enlarged contact member298projecting therefrom. Contact member298engages the bone about the entrance to the pathway formed therein when body292and insertion end294are positioned in the pathway. As insertion end294is threadingly engaged in the pathway, contact member298engages the bone to deliver a compression force between the adjacent bony structures along the pathway.

Various techniques and instruments for forming pathways60,70are contemplated. For example, inFIG. 9there is shown a cutting instrument160which includes an outer shaft162defining a passage164therethrough. A cutting head170is located adjacent a leading end166of outer shaft162, and a coupler172is located adjacent to a trailing end168of outer shaft162. A flexible drive member174extends between and interconnects coupler172with cutting head170. A rotary power source (not shown) can be engaged to coupler172, and operated to deliver a rotary force thereto. Rotation of coupler172is transmitted through drive member174to rotate cutting head170. Cutting head170can be configured to drill or ream a pathway through bony material along the desired insertion path.

Outer shaft162is curved along its longitudinal axis to conform to the desired shape of the pathway60,70to be formed therewith. Cutting head170removes bone material from the pathway60,70which can deposited in passage164for evacuation. Drill instrument160can be guided through the bony structures to form pathway60,70with image guidance technology employed during the surgical procedure. The pathway60,70can further be defined through pre-operative X-rays or fluoroscopy to determine the appropriate location and trajectory for pathways60,70prior to the surgical stabilization procedure. Outer shaft162can be bent, formed, controlled or manipulated so that the pathway of the desired shape, trajectory and length is formed.

In one embodiment, drive member174includes a central guide lumen176extending therethrough. Guide lumen176extends through cutting head170and also coupler172. Guide lumen176can receive a guidewire or other device along which the cannulated drilling or reaming instrument160is to be moved to form the pathway along the desired trajectory.

After the pathway is formed, the stabilization device can be inserted into the pathway with freehand techniques or instruments, or with instruments that provide for controlled insertion. For example,FIG. 10shows C1 vertebra12and C2 vertebra30in section along pathway60. Although occiput50is not shown, it should be understood that, as discussed above, pathway60may extend into occiput50. Furthermore, it should be understood that the discussion that follows also has application with pathway70.

In the illustrated embodiment, C1 vertebra12and C2 vertebra30each include an anchor222,232, respectively, engaged thereto. A first anchor extension220extends from first anchor222, and a second anchor extension230extends from second anchor232. An insertion instrument200can be provided that is, in one embodiment, configured substantially as described in U.S. Pat. No. 6,530,929, which is hereby incorporated by reference in its entirety. Insertion instrument200includes a first portion202pivotally mounted to the anchor extensions220,230about pivot axis206. Insertion instrument200further includes a second portion204extending from and transversely oriented to first portion202. First portion202is rotatable about the proximal ends of anchor extensions220,230to swing second portion204along an arcuate axis210.

First portion202includes a length extending from pivot axis206that corresponds to the radius or other shape required from pivot axis206to form pathways60,70through the bony structures. Accordingly, the length of first portion202is sufficient to position second portion204and thus the stabilization device coupled thereto adjacent or below anchors222,232and into the bony structure to which insertion instrument200is mounted.

A stabilization device, drill instrument, guidewire or other device can be delivered to the bony structure along the desired pathway. For example, stabilization device100, as shown inFIG. 10, is releasably coupled to and extends from second portion204. In this configuration, it is contemplated that longitudinal axis104of stabilization device100extends along arcuate axis210. Accordingly, as first portion202is pivoted about pivot axis206, second portion204and thus stabilization device100are moved along arcuate axis210.

Other forms for insertion instrument200are contemplated. For example, insertion instrument200can be mounted to a single anchor engaged to the bony structure, or to more than two anchors. Suitable anchors include multi-axial screws, uni-axial screws, staples, tacks, stakes, pins, wires, posts or other device capable of suitably mounting the insertion instrument200to a bony structure.

In one technique, pathways60,70are formed by positioning a guidewire through the bony structure along the desired pathway trajectory through the bony tissue. The guidewire insertion and positioning can be monitored via a surgical navigation system employing fluoroscopy or other suitable viewing instrumentation. Additionally, the guidewire can be coupled to an inserter, such as insertion instrument200, to facilitate positioning along the pathway60,70. After insertion of the guidewire, a cutter or drill with a flexible shaft can be guided along the guidewire to form pathway60,70. In one form, drill instrument160can be provided with guide lumen176therealong to receive the guidewire as it is advanced along pathway60,70. Other embodiments contemplate a drill instrument with a central lumen for receiving the guidewire as the curved drill instrument is advanced therealong.

Various other instruments are also contemplated which can be coupled to drill instrument160to guide formation of pathway60,70. For example, U.S. Pat. No. 6,226,548 to Foley et al., which is hereby incorporated by reference, describes an optically tracked inserter device. Drill instrument160can be coupled to such an inserter device to provide image guided navigation of the drill instrument along the pathways60,70. The stabilization device can further be coupled to such an inserter device and inserted into the pathway60,70to provided image-guided navigation and monitoring of the stabilization device insertion.