US20090287250A1 - Method and apparatus for replacing the function of facet joints - Google Patents

Abstract

A system and method is provided for replacing the functions of a facet joint between a superior vertebra and an inferior vertebra without necessarily requiring an anatomical implant. The method includes: providing one or more flexible posterior devices to replace main functions of the facet joint; and adapting a first one of the one or more posterior devices for a first attachment to a first pedicle, and a second attachment to a second pedicle.

Description

• The present disclosure relates to spinal devices and methods, and more particularly, to a system and method for replacing the functions of a facet joint between a superior vertebra and an inferior vertebra without necessarily requiring an anatomical implant.
BACKGROUND
• A vertebrae includes a vertebral body and posteriorly extending structures including pedicles, a lamina, articular processes, and a spinous process. The articular processes include superior and inferior processes that join to form zygapophyseal, or facet joints, with adjacent vertebrae. The facet joints are formed by the articular processes of adjacent vertebrae—the inferior articular process of a vertebra articulates with the superior articular process of the vertebra below. Facet joints perform several functions, including stabilizing the spine and earring approximately 20% of the compressive load on the spine. Accordingly, their anatomic position and orientation affect the mobility of each spinal region. For example, in the cervical region, facet joints are oriented in the coronal plane and are capable of a significant range of motions in the six degrees of freedom. In the lumber area, facet joints are oriented parasagittal and thereby limit rotation.
• Major trauma or repetitive minor trauma may cause a facet joint to be damaged or otherwise degenerate. As a result, the hyaline cartilage that lines the joint can lose its water content, and eventually become worn. When this happens, the articular processes begin to override each other as the joint capsules become stretched, resulting in the malalignment of the joints and abnormal biomechanical function of the motion segment.
• The current treatment for degenerated or otherwise damaged facet joints is to provide prosthetic facet joints. The prosthetic facet joints are shaped and positioned similar to the original facet joint, and must be constructed to withstand the required movement and weight handling functions of the original facet joint. Such requirements are difficult to achieve while also meeting requirements of reliability and durability. What is needed is a system and method for reducing and/or eliminating the need for anatomical prosthetic facet joints.
SUMMARY
• The present invention provides a system and method for replacing the functions of a facet joint between a superior vertebra and an inferior vertebra without necessarily requiring an anatomical implant.
• In one embodiment, a surgical implant for replacing functions of a facet joint between adjacent vertebrae is provided. The surgical implant includes a first biocompatible attachment device for attaching to a first pedicle of a superior vertebrae and a second biocompatible attachment device for attaching to a second pedicle of an inferior vertebrae. The surgical implant also includes a flexible member attached to the first and second biocompatible attachment devices. The first and second biocompatible attachment devices are positioned, and the flexible member is adapted, so that the surgical implant applies a distracting force between the superior and inferior vertebrae sufficient for selectively maintaining the first and second pedicles at a predetermined distance.
• In another embodiment, a facet replacement system is provided. The facet replacement system includes a first posterior device having first and second attachment mechanisms and a compression-resistant member connected there between, and a second posterior device having first and second attachment mechanisms and an expansion-resistant member connected there between. The first attachment mechanisms are adapted to connect to respective portions of a superior spinous process, and the second attachment mechanisms are adapted to connect to respective portions of an inferior spinous process.
• In another embodiment, a method for replacing functions of a facet joint between adjacent vertebrae is provided. The method includes: providing one or more flexible posterior devices to replace main functions of the facet joint; and adapting a first one of the one or more posterior devices for a first attachment to a first pedicle, and a second attachment to a second pedicle.
• In another embodiment, a prosthetic device for replacing functions of a facet joint between adjacent vertebrae comprises: means for providing one or more flexible posterior devices to replace main functions of the facet joint; and means for adapting a first one of the one or more posterior devices for a first attachment to a first transverse process, and a second attachment to a second transverse process.
• In another embodiment, a method for replacing functions of a facet joint between adjacent vertebrae comprises: providing one or more flexible posterior devices to replace main functions of the facet joint; and adapting a first one of the one or more posterior devices for a first attachment to a first articular process, and a second attachment to a second articular process.
• In another embodiment, a method for replacing functions of a facet joint between adjacent vertebrae comprises: providing one or more flexible posterior devices to replace main functions of the facet joint; and adapting a first one of the one or more posterior devices for a first attachment to a first spinous process, and a second attachment to a second spinous process.
• In another embodiment, a method for replacing functions of a facet joint between adjacent vertebrae comprises: providing one or more flexible posterior devices to replace main functions of the facet joint; and adapting a first one of the one or more posterior devices for a first attachment to a first lamina, and a second attachment to a second lamina.
• In another embodiment, a method for replacing functions of a facet joint between adjacent vertebrae comprises: attaching one or more posterior devices to the adjacent vertebrae to replace main functions of the facet joint without utilizing any anatomical facet joint implant.
• In another embodiment, a posterior device for replacing functions of a facet joint comprises: a first component comprising an elongated body; and a first joint having a first opening wherein the first opening contains an elastic material; a second component comprising: an elongated body; and a second joint having a second opening wherein the second joint is coupled with the first joint, and the second opening contains the elastic material; and a connector covering the first joint and the second joint wherein the connector comprises the elastic material.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 illustrates a posterior device and an anterior device for replacing functions of a facet joint according to one embodiment of the present invention.
• FIG. 2A illustrates a posterior device and an anterior device for replacing functions of a facet joint according to one embodiment of the present invention.
• FIGS. 2B and 2C illustrates exemplary posterior devices.
• FIG. 3 illustrates posterior devices and an anterior device for replacing functions of a facet joint according to one embodiment of the present invention.
• FIG. 4 illustrates components of a posterior device for replacing functions of a facet joint according to one embodiment of the present invention.
• FIG. 5 illustrates an assembled posterior device ofFIG. 4.
• FIGS. 6-8 illustrate exemplary usages of the posterior device ofFIG. 5.
DETAILED DESCRIPTION
• For the purposes of promoting an understanding of the principles of the invention, references will now be made to the embodiments, or examples, illustrated in the drawings, and specific languages will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Furthermore, reference numerals are repeated for the sake of simplicity, and do not, by themselves, designate any combination of elements discussed in the different embodiments. Any alterations and further modifications in the described embodiments, and any 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.
• Referring now toFIG. 1, for the sake of example, two adjacent vertebrae V1 and V2 are shown with a damaged or degeneratedfacet joint110. The present embodiment attempts to replicate the functions (or some functions) of thefacet joint110 without necessarily requiring an anatomical implant such as a prosthetic facet joint device. It is understood, however, that an anatomical implant can still be used in some embodiments, as desired. To replace the functions of thefacet joint110, aposterior device100 and/or ananterior device120 are utilized. Theposterior device100 may be utilized alone or may be combined with theanterior device120 to replicate the functions of thefacet joint110. Conversely, a stand along anterior device (without a posterior device) could be used to replicate the functions of the facet joint.
• To implement the functions of thefacet joint110 in theposterior device100 and/or theanterior device120, many methods may be employed to evaluate the functional requirements of thefacet joint110. For example, the spinal load carried by thefacet joint110 can be determined. Alternatively or in addition, motion analysis methods, which utilize design devices to reproduce the motions of thefacet joint110, may be utilized.
• Once the functional requirements of thefacet joint110 are evaluated, the composition of theposterior device100 may be selected to meet these requirements. Examples include flexible biocompatible devices, such as devices constructed of shape memory alloys, cables, or springs. In the illustration ofFIG. 1, theposterior device100 is a flexible cable. In the present embodiment, theposterior device100 may reside in a variety of physical locations, so that the device can be sized to meet the functional requirements instead of meeting the space and shape requirements of thefacet joint110. In this illustration ofFIG. 1, theposterior device100 is attached to the pedicles of the vertebrae V1 and V2 bybiocompatible attachment devices102 and104, such as pedicle screws. Other examples of attachment devices include staples, rivets, and locking grooves formed within the vertebrae for receiving a securing portion of thedevice100. It is contemplated that theposterior device100 may also be attached to other parts of the vertebrae V1 and V2, such as articular processes, transverse processes, spinous processes, or laminae. It is further contemplated that tethers, staples, and other anchoring devices can be used.
• Theposterior device100 may be a flexible cable that is made of shape memory materials, which may be polymer-based or Nitinol. For example, theposterior device100 may comprise approximately half Ni and half Ti, and may be treated in hot air and then cold water to produce an austenite finish temperature that is lower than the temperature range of a human body. In this example, theposterior device100 may have an austenite finish temperature of approximately 34° C. Accordingly, at above 34° C., theposterior device100 becomes superelastic.
• Prior to implanting theposterior device100 into a human body, it may be cooled to below 34° C. to maintain a predefined shape for easy insertion. Alternatively, it may remain at a temperature of above 34° C., so that its superelasticity may assist the insertion.
• Theanterior device120 may be inserted into a disc space between the vertebrae V1 and V2. In the illustration ofFIG. 1, theanterior device120 is a disc replacement device, such as disclosed in U.S. Pat. No. 6,402,785 (assigned to SDGI Holdings, Inc., and hereby incorporated by reference). Other examples ofanterior devices120 include flexible biocompatible devices, such as a cable, a spring, or a device made of shape memory alloys.
• Depending on the condition of the facet joint110, it may or may not be surgically removed. For example, if the facet joint110 causes severe pain, then it may warrant removal. Alternatively, the facet joint110 may be left in place and may even be utilized to a limited extent.
• Referring now toFIG. 2A, in another embodiment, a facet joint204 between vertebra V3 and V4 may be damaged or degenerated. As a result, aposterior device200, which may be used alone, or combined with an anterior device202, may replace the functions (or main functions) of the facet joint204.
• Referring now toFIG. 2B, in one embodiment, theposterior device200 may be a biocompatible spring that includes a pair ofattachment devices206 and208, abias member210, and ahousing attachment212.
• Theattachment devices206 and208 may comprises any conventional attachment device, such as pins, connectors, cotters, rivets, spikes, keys, couplings, or bushings. In this illustration, theattachment devices206 and208 are biocompatible screws that may be inserted into the vertebrae V3 and V4 to secure theposterior device200.
• Thebias member210 may reshape in response to spinal motions. Similar to the function of a conventional spring, thebias member210 responds to spinal movements by replicating the functions of the facet joint204. For example, thebias member210 may be compressed as a load is imposed upon the spine, but become extended during a flexion motion. It is contemplated that thebias member210 may operate within its elastic range as determined by its chosen material and structure. It is further contemplated that thebias member210 may comprise any biocompatible material, such as titanium, carbon fiber, polymers, or shape memory alloys.
• Thehousing attachment212 may be used to protect thebias member210 from the interference of surrounding tissues, so that the tissues will not inadvertently clog thebias member210 and impede its proper function. It is contemplated that thehousing attachment212 may comprise any biocompatible material, such as rubber or shape memory alloys.
• It is contemplated that theposterior device200 and its components may comprise a variety of shapes, such as the one illustrated inFIG. 2C. It is further contemplated that theposterior device200 may include a plurality of bias members, or that may simply be a conventional spring. It is also contemplated that theposterior device200 may be any flexible biocompatible device, such as a cable, or a device made of shape memory alloys.
• Theposterior device200 may be attached to the transverse processes of the vertebrae V3 and V4 by any conventional biocompatible attachment devices, such as pins, connectors, cotters, rivets, spikes, keys, couplings, bushings, washers, or other anchoring devices. It is also contemplated that theposterior device200 may be attached to pedicles, articular processes, spinous processes, or laminae of the veterbrae V3 and V4.
• The anterior device202, which may be a nucleus device, may be inserted into a disc space between the vertebrae V3 and V4, and work together with theposterior device200 to replace the functions of the facet joint204. The anterior device202 may comprise any conventional nucleus replacement devices. Alternatively, it may comprise any flexible biocompatible device, such as a cable, a spring, or a device made of shape memory alloys. It will be understood that conventional nucleus replacement devices are known in the art, and will not be described further herein.
• Depending on the condition of the disc joint204, it may or may not be surgically removed. For example, if the disc joint204 causes severe pain, it may be surgically removed. Alternatively, without substantially relying on its functions, it may be left in the animal body.
• Referring now toFIG. 3, in yet another embodiment, a combination of aposterior device302 and aposterior device304 may be used to replace the functions (or main functions) of a damaged facet joint (not shown) between vertebrae V5 and V6. It is also contemplated that ananterior device310, which may be similar to previously described devices108 or202, may function together with theposterior devices302 and304 to replace the facet joint functions.
• Theposterior device302 and theposterior device304 may compliment each other in replicating the functions of the facet joint. For example, theposterior device302 may be a biocompatible spring that regulates the capacity of the replaced facet joint functions, while theposterior device304 may be a damper that regulates the movement of the replaced facet joint functions. Theposterior device302 may be any of the previously describedposterior device100 or200, or a biocompatible damper. Likewise, theposterior device304 may be any of the previously describedposterior device100 or200. In one example, theposterior device304 may be a damper identical or similar to the embodiments disclosed in the U.S. Pat. No. 2,235,488 entitled “Shock-Absorbing Device”, which is hereby incorporated by reference.
• In this example, theposterior device302 is attached to pedicles via pedicle screws, while theposterior device304 is attached to transverse processes of the vertebrae V5 and V6. Alternatively, each of theposterior devices302 and304 may be attached to any of articular processes, transverse processes, spinous processes, laminae, or pedicles of the vertebrae V5 and V6. It is contemplated that one or more additional posterior devices may be added to theposterior devices302 and304, and all of them may work together to replace the facet joint functions.
• Even though previous embodiments are directed toward replacing the functions of a single facet joint, it is contemplated that this invention may be applied to replace the functions of a plurality of facet joints. For example, a bilateral approach may be adopted to replace damaged facet joints on both sides of a disc.
• Referring now toFIG. 4, in another embodiment, aposterior device400 may comprise aconnector418, afirst component420, and ansecond component422. Theposterior device400 may be used alone, or in combination with one or more additional posterior and/or anterior devices described previously, to replace the functions of a facet joint without any anatomical facet joint implant. It is contemplated that theposterior device400 may be used to replace any of theposterior devices100,200,302 or304 in the previously described embodiments.
• Theconnector418 provides elasticity for theposterior device400 to allow motions that imitate the functions of a facet joint. Theconnector418 may comprise any elastic biocompatible material, such as rubber, silicon or shape memory alloys. It may comprise any suitable shape, which may be a hollowed olive or a partial sphere.
• Thefirst component420 may comprise atip408, anelongated body406, which may be a rod or shaft, and a joint402. Thetip408 may be pointed, and adapted for a percutaneous insertion of theposterior device400, which may entail pushing theposterior device400 through tissues of an animal body. The joint402 comprises anopening402, which may contain any biocompatible elastic material, such as rubber, silicon or shape memory alloys, to facilitate motions of theposterior device400.
• Thesecond component422 may have an identical or similar structure as that of thefirst component420. In this illustration, thesecond component422 may comprise atip416, anelongated body414, which may be a rod or shaft, and a joint410. Thetip416 may be pointed, and adapted for a percutaneous insertion of theposterior device400, which may entail pushing theposterior device400 through tissues of an animal body. The joint410 comprises anopening412, which may contain any biocompatible elastic material, such as rubber, silicon or shape memory alloys, to facilitate motions of theposterior device400. Theopening412 may be coupled to theopening404, so that an elastic material may flow through bothopenings404 and412 to facilitate the functions of theposterior device400. It is also contemplated that thesecond component422 may have a different structure from that of thefirst component420.
• The first andsecond components420 and422 may be coupled together by any conventional means, such as being molded or screwed together through theirrespective joints402 and410, to form a unit. Further, they may be coupled at different angles to simulate the natural anatomy of facet joints. For example, to replace functions of a facet joint in the cervical region, the first andsecond components420 and422 may be coupled at approximately 45° to the horizon to simulate the orientation of a natural facet joint. In another example, to replace functions of a facet joint in the thoracic region, the first andsecond components420 and422 may be coupled at an angle of approximately 60° to the axial plane and 20° to the frontal plane of a human body. In the lumbar area, the first andsecond components420 and422 may be joined at an angle of approximately 90° to the axial plane and 45° to the frontal plane of a human body.
• Each of the first andsecond components420 and422 may comprise any biocompatible material, such as stainless steel, titanium, shape memory alloys, polymers, carbon fiber, and porous material. It is contemplated that theposterior device400 may be attached to any of the pedicles, articular processes, transverse processes, spinous processes, or laminae of vertebrae.
• Referring now toFIG. 5, theposterior device400 may be inserted into the spinal region as a unit by any conventional approach, such as a posterior or lateral approach. It is also contemplated that theposterior device400 may be inserted into the spinal region by the approaches disclosed in the U.S. Pat. No. 6,530,929 (assigned to SDGI Holdings, Inc.).
• Utilization of theposterior devices100,200,302,304, and400 will now be described. The posterior device(s) may be inserted into the spinal region by any conventional approach, such as a posterior or lateral approach. For example, procedures and instruments useable in a posterior approach are disclosed in U.S. Pat. No. 6,241,729 (assigned to SDGI Holdings, Inc.), and a publication by Sofamor Danek© 1996 entitled “Surgical Technique using Bone Dowel Instrumentation for Posterior Approach”, each of which is incorporated herein by reference in its entirety. It is also contemplated that any of theposterior devices100,200,302,304, and400 may be inserted into the spinal region by the approaches disclosed in the U.S. Pat. No. 6,530,929 (assigned to SDGI Holdings, Inc., and hereby incorporated by reference).
• Theanterior devices120,202 and303 may be inserted into the spinal region by any conventional approach, such as an anterior, a posterior or lateral approach. For example, procedures and instruments useable in an anterior approach are disclosed in U.S. Pat. No. 6,428,541 (assigned to SDGI Holdings, Inc.), and the publication by Sofamor Danek© 1996 entitled “Surgical Technique using Bone Dowel Instrumentation for Anterior Approach”, each of which is incorporated herein by reference in its entirety.
• FIGS. 6-8 illustrate exemplary usages of theposterior device400 as it is attached to the vertebrae of an animal body. For example, referring now toFIG. 6, shown therein is theposterior device400 placed between the vertebrae V7, V8 by twomulti-axial screws602 and604 according to one embodiment of the present invention. Further examples of attachment mechanisms that can be used are disclosed in U.S. Pat. Nos. 6,280,442, 5,891,145, 6,485,491, and 6,520,963, which are hereby incorporated by reference.FIGS. 7 and 8 illustrate perspective views ofFIG. 6. from different angles to show the implementation of theposterior device400 according to one embodiment of the invention.
• Although only a few exemplary embodiments of this invention have been described above in details, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Also, features illustrated and discussed above with respect to some embodiments can be combined with features illustrated and discussed above with respect to other embodiments. For example, attachment mechanisms secured to a spinal process can alternatively be secured to a pedicle or lamina, as desired. Accordingly, all such modifications and alternatives are intended to be included within the scope of the claimed invention.

Claims (21)

1. A surgical implant comprising:

a first biocompatible attachment device configured to attach to a first pedicle of a superior vertebrae;

a second biocompatible attachment device configured to attach to a second pedicle of an inferior vertebrae; and

a flexible member attached to the first and second biocompatible attachment devices, the flexible member comprising a joint component and a flexible connector covering at least part of the joint component;

wherein the first and second biocompatible attachment devices are positioned, and the flexible member is adapted, so that the surgical implant applies a distracting force between the superior and inferior vertebrae sufficient for selectively maintaining the first and second pedicles at a predetermined distance.

2. The surgical implant ofclaim 1 wherein the flexible member is further adapted to be compressed in response to a second force that exceeds the distracting force.

3. The surgical implant ofclaim 1 wherein the joint component is positionable between the first and second biocompatible attachment devices, and comprises a first element having a first opening and a second element having a second opening, and wherein elastic material is disposed between the first opening and the second opening.

4. The surgical implant ofclaim 1 wherein the flexible member further includes a first member connected between the first biocompatible attachment device and the joint component, and a second member connected between the second biocompatible attachment device and the joint component, and wherein the first and second members are connected together at the joint component.

5.-29. (canceled)

30. A spinal stabilization device comprising:

a first component comprising:

an elongated body; and

a first joint element having a first opening wherein the first opening contains an elastic material;

a second component comprising:

an elongated body; and

a second joint element having a second opening wherein the second joint element is coupled with the first joint element, and the second opening contains the elastic material; and

a connector covering the first joint element and the second joint element wherein the connector comprises the elastic material.

31. The device ofclaim 30 wherein the first component further comprises a pointed tip adapted for percutaneous insertion of the posterior device.

32. The device ofclaim 30 wherein the second component further comprises a pointed tip adapted for percutaneous insertion of the posterior device.

33. The device ofclaim 30 wherein the connector is olive-shaped.

34. The device ofclaim 30 wherein the first component and the second component are coupled at an angle of approximately 45.degree. to the horizon.

35. The device ofclaim 30 wherein the first component and the second component are coupled at an angle of approximately 60.degree. to an axial plane and 20.degree. to an frontal plane of a human body.

36. The posterior device ofclaim 30 wherein the first component and the second component are coupled at an angle of approximately 90.degree. to an axial plane and 45.degree. to a frontal plane of a human body.

37.-39. (canceled)

40. A spinal stabilization implant comprising:

a first biocompatible attachment device configured to attach to a first pedicle of a superior vertebrae;

a second biocompatible attachment device configured to attach to a second pedicle of an inferior vertebrae; and

a flexible member attached to the first and second biocompatible attachment devices, the flexible member comprising a first component and a second component and an elastic connector, the elastic connector covering at least a part of the first component or the second component; wherein when the first and second biocompatible attachment devices are attached to the first and second pedicles, the surgical implant applies a distracting force between the superior and inferior vertebrae sufficient for selectively maintaining the first and second pedicles at a predetermined distance.

41. The implant ofclaim 40, wherein the first component comprises a first joint element and the second component comprises a second joint element, and wherein the first joint element and the second joint element are connected.

42. The implant ofclaim 41, wherein the elastic connector surrounds at least part of the first joint element and the second joint element.

43. The implant ofclaim 40, wherein the first component comprises a tip adapted for percutaneous insertion of the implant.

44. The implant ofclaim 40, wherein the second component comprises a tip adapted for percutaneous insertion of the implant.

45. A flexible spinal stabilization device comprising:

a first biocompatible attachment device,

a second biocompatible attachment device,

a joint component attached to the first and the second biocompatible attachment device, the joint component comprising:

a first elongated body comprising a first joint element having a first opening, and

a second elongated body comprising a second joint element having a second opening, and

a connector comprising a flexible material,

wherein the first and second joint elements are covered by the connector and wherein elastic material is disposed between the first and second openings.

46. The implant ofclaim 45, wherein the first elongated body comprises a tip adapted for percutaneous insertion of the implant.

47. The implant ofclaim 45, wherein the second elongated body comprises a tip adapted for percutaneous insertion of the implant.

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