Abstract:
The invention discloses methods, devices, systems and kits for repairing, replacing and/or augmenting natural facet joint surfaces and/or facet capsules. An implantable facet joint device of one embodiment comprises a cephalad facet joint element and a caudal facet joint element. The cephalad facet joint element includes a member adapted to engage a first vertebra, and an artificial cephalad bearing member. The caudal facet joint element includes a connector adapted for fixation to a second vertebra at a fixation point and an artificial caudal bearing member adapted to engage the cephalad bearing member. The artificial caudal bearing member is adapted for a location lateral to the fixation point. In another embodiment, an implantable facet joint device comprises a cephalad crossbar adapted to extend mediolaterally relative to a spine of a patient, the crossbar having opposite first and second ends, a connector element adapted to connect the crossbar to a first vertebra, a first artificial cephalad bearing member adapted for connection to the first end of the crossbar and adapted to engage a first caudal facet joint element connected to a second vertebra, and a second artificial cephalad bearing member adapted for connection to the second end of the crossbar and adapted to engage a second caudal facet joint element connected to the second vertebra.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 11/800,895, filed May 7, 2007, now issued as U.S. Pat. No. 8,496,686, and entitled “Minimally Invasive Spine Restoration Systems, Devices, Methods and Kits,” which is a continuation-in-part of U.S. application Ser. No. 11/277,223, filed Mar. 22, 2006, now abandoned, and entitled “Minimally Invasive Spine Restoration Systems, Devices, Methods and Kits”, which claims the benefit of U.S. Provisional Application No. 60/664,441, filed Mar. 22, 2005, and entitled “Minimally Invasive Facet Replacement”; U.S. Provisional Application No. 60/719,427, filed Sep. 22, 2005, and entitled “Prosthesis, Tools and Methods for Replacement of Natural Facet Joints with Artificial Facet Joint Surfaces”; and U.S. Provisional Application 60/752,277, filed Dec. 20, 2005, and entitled “Spinal Joint Replacement Systems”. U.S. application Ser. No. 11/800,895 also claims the benefit of U.S. Provisional Application No. 60/797,879, to Philip Berg et al, filed May 5, 2006, and entitled “Facet Replacement Systems,”. The disclosures of the above applications are incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to devices and surgical methods for the treatment of various types of pathologies of the spine. More specifically, the present invention is directed to several different types of minimally invasive devices, methods, systems and kits for treating injured or diseased facet joints, intervertebral joints and adjacent anatomy of the spine. 
     BACKGROUND OF THE INVENTION 
     Back pain, particularly in the “small of the back” or lumbosacral (L4-S1) region, shown in  FIG. 1 , is a common ailment. In many cases, the pain severely limits a person&#39;s functional ability and quality of life. Such pain can result from a variety of spinal pathologies. Through disease or injury, the laminae, spinous process, articular processes, or facets of one or more vertebral bodies can become damaged, such that the vertebrae no longer articulate or properly align with each other. This can result in an undesired anatomy, loss of mobility, and pain or discomfort. 
     In many cases, the vertebral facet joints can be damaged by either traumatic injury or by various disease processes. These disease processes include osteoarthritis, ankylosing spondylolysis, and degenerative spondylolisthesis. Moreover, the facet joint has been implicated as a potential cause of neck pain for persons having whiplash. Aside from pain coming from the facets themselves, such damage to the facet joints can often result in eventual degeneration, abrasion, or wearing down of the facet joints, eventually resulting in pressure on nerves, also called “pinched” nerves, or nerve compression or impingement. The result is further pain, misaligned anatomy, and a corresponding loss of mobility. Pressure on nerves can also occur without an anatomic or functional manifestation of a disease, or pathology, at the facet joint, e.g., as a result of a herniated disc. 
     Many spinal pathologies mandating repair and/or replacement of an intervertebral disc (including many of those that may be currently treated through spinal fusion, nucleus replacement, vertebral end-plate/body augmentation and/or reconstruction, interspinous distraction and/or dynamic stabilization), can often be traced back to degeneration, disease and/or failure of the facet joints. Alteration of the facet joint biomechanics resulting from an anatomic or functional manifestation of a disease can adversely affect the loading and biomechanics of the intervertebral disc, eventually resulting in degeneration, damage and/or failure of the intervertebral disc. 
     One type of conventional treatment of facet joint pathology is spinal stabilization, also known as intervertebral stabilization. Intervertebral stabilization desirably prevents relative motion between vertebrae of the spine. By preventing movement, pain is desirably reduced. Stabilization can be accomplished by various methods. One method of stabilization is spinal fusion. Another method of stabilization is fixation of any number of vertebrae to stabilize and prevent movement of the vertebrae. In addition, where compression or subsidence of the disc and/or facet joints has occurred, the physician can utilize fusion devices such as pedicle screw and rods systems, or interbody fusion cages, to elevate or “jack up” the compressed level, desirably obtaining a more normal anatomical spacing between the vertebral bodies. 
     Various devices are known for fixing the spine and/or sacral bone adjacent the vertebra, as well as attaching devices used for fixation, are known in the art, including: U.S. Pat. No. 6,290,703, to Ganem, for Device for Fixing the Sacral Bone to Adjacent Vertebrae During Osteosynthesis of the Backbone; U.S. Pat. No. 6,547,790, to Harkey, 111, et al., for Orthopaedic Rod/Plate Locking Mechanisms and Surgical Methods; U.S. Pat. No. 6,074,391, to Metz-Stavenhagen, et al., for Receiving Part for a Retaining Component of a Vertebral Column Implant; U.S. Pat. No. 5,569,247, to Morrison, for Enhanced Variable Angle Bone Bolt; U.S. Pat. No. 5,891,145, to Morrison, et al., for Multi-Axial Screw; U.S. Pat. No. 6,090,111, to Nichols, for Device for Securing Spinal Rods; U.S. Pat. No. 6,451,021, to Ralph, et al., for Polyaxial Pedicle Screw Having a Rotating Locking Element; U.S. Pat. No. 5,683,392, to Richelsoph, et al., for Multi-Planar Locking Mechanism for Bone Fixation; U.S. Pat. No. 5,863,293, to Richelsoph, for Spinal Implant Fixation Assembly; U.S. Pat. No. 5,964,760, to Richelsoph, for Spinal Implant Fixation Assembly; U.S. Pat. No. 6,010,503, to Richelsoph, et al., for Locking Mechanism; U.S. Pat. No. 6,019,759, to Rogozinski, for Multi-Directional Fasteners or Attachment Devices for Spinal Implant Elements; U.S. Pat. No. 6,540,749, to Schafer, et al., for Bone Screw; U.S. Pat. No. 6,077,262, to Schlapfer, for Posterior Spinal Implant; U.S. Pat. No. 6,248,105, to Schlapfer, et al., for Device for Connecting a Longitudinal Support with a Pedicle Screw; U.S. Pat. No. 6,524,315, to Selvitelli, et al., for Orthopaedic Rod/Plate Locking Mechanism; U.S. Pat. No. 5,797,911, to Sherman, et al., for Multi-Axial Bone Screw Assembly; U.S. Pat. No. 5,879,350, to Sherman, et al., for Multi-Axial Bone Screw Assembly; U.S. Pat. No. 5,885,285, to Simonson, For Spinal Implant Connection Assembly; U.S. Pat. No. 5,643,263, to Simonson for Spinal Implant Connection Assembly; U.S. Pat. No. 6,565,565, to Yuan, et al., for Device for Securing Spinal Rods; U.S. Pat. No. 5,725,527, to Biederman, et al., for Anchoring Member; U.S. Pat. No. 6,471,705, to Biederman, et al., for Bone Screw; U.S. Pat. No. 5,575,792, to Errico, et al., for Extending Hook and Polyaxial Coupling Element Device for Use with Top Loading Rod Fixation Devices; U.S. Pat. No. 5,688,274, to Errico, et al., for Spinal Implant Device having a Single Central Rod and Claw Hooks; U.S. Pat. No. 5,690,630, to Errico, et al., for Polyaxial Pedicle Screw; U.S. Pat. No. 6,022,350, to Ganem, for Bone Fixing Device, in Particular for Fixing to the Sacrum during Osteosynthesis of the Backbone; U.S. Pat. No. 4,805,602, to Puno, et al., for Transpedicular Screw and Rod System; U.S. Pat. No. 5,474,555, to Puno, et al., for Spinal Implant System; U.S. Pat. No. 4,611,581, to Steffee, for Apparatus for Straightening Spinal Columns; U.S. Pat. No. 5,129,900, to Asher, et al., for Spinal Column Retaining Method and Apparatus; U.S. Pat. No. 5,741,255, to Krag, et al., for Spinal Column Retaining Apparatus; U.S. Pat. No. 6,132,430, to Wagner, for Spinal Fixation System; U.S. Publication No. 2002/0120272, and to Yuan, et al., for Device for Securing Spinal Rods. 
     Another type of conventional spinal treatment is decompressive facetectomy/laminectomy. Where spinal stenosis (or other spinal pathology) results in a narrowing of the spinal canal and/or the intervertebral foramen (through which the spinal nerves exit the spine), and neural impingement, compression and/or pain results, the tissue(s) (hard and/or soft tissues) causing the narrowing may need to be resected and/or removed. A procedure which involves excision of part or all of the laminae and other tissues (including some or all of the facets themselves) to relieve compression of nerves is called a decompressive facetectomy/laminectomy. See, for example, U.S. Pat. No. 5,019,081, to Watanabe, for Laminectomy Surgical Process; U.S. Pat. No. 5,000,165, to Watanabe, for Lumbar Spine Rod Fixation System; and U.S. Pat. No. 4,210,317, to Spann, et al., for Apparatus for Supporting and Positioning the Arm and Shoulder. Depending upon the extent of the decompression, the removal of support structures such as the facet joints and/or connective tissues (either because these tissues are connected to removed structures or are resected to access the surgical site) may result in instability of the spine, necessitating some form of supplemental support such as spinal fusion, discussed above. 
     SUMMARY OF THE INVENTION 
     While spinal fusion has become the “gold standard” for treating many spinal pathologies, including pathologies such as neurological involvement, intractable pain, instability of the spine and/or disc degeneration, it would be desirable to reduce and/or obviate the need for spinal fusion procedures by providing devices and systems that stabilize, or preserve motion of the spinal motion segment (including, but not limited to, facet joint repair or replacement, intervertebral disk replacement or nucleus replacement, implantation of interspinous spacers and/or dynamic stabilization devices, and/or facet injections). 
     The present invention includes the recognition that many spinal pathologies eventually requiring surgical intervention can be traced back, in their earlier stage(s), to some manner of a degeneration, disease and/or failure of the facet joints and/or interspinous disc. Moreover, spinal fusion procedures can eventually require further surgical intervention. For example, degeneration of facet joints can result in an unnatural loading of an intervertebral disc, eventually resulting in damage to the disc, including annular bulges and/or tears. Similarly, degeneration and/or failure of a facet joint can potentially lead to slipping of the vertebral bodies relative to one another, potentially resulting in spondylolisthesis and/or compression of nerve fibers. In addition, degeneration of the facet joints themselves can become extremely painful, leading to additional interventional procedures such as facet injections, nerve blocks, facet removal, facet replacement, and/or spinal fusion. Thus, if the degenerating facet joint can be treated at an early stage, the need for additional, more intrusive procedures, may be obviated and damage that has already occurred to spinal structures such as the intervertebral disc of the treated level (as well as the disc and/or facets of other spinal levels) may be slowed, halted or even reversed. 
     Further, the invention includes the ability to accommodate anatomical variability to treat all vertebral levels, including the various cervical, thoracic, lumbar and/or sacral levels, as well as L3-L4, L4-L5 and L5-S1, across a majority of the patient population. 
     The various embodiments disclosed and discussed herein may be utilized to restore and/or maintain varying levels of the quality or state of motion or mobility and/or motion preservation in the treated vertebral bodies. Depending upon the extent of facet joint degradation, and the chosen treatment regime(s), it may be possible to completely restore the quality or state of motion across the entire spinal motion segment, across one or more of the facet joints, or restore limited motion (and/or allow greater-than-normal ranges of motion) across the facet joint(s) to reduce or obviate the need for further treatment of the spinal motion segment. 
     In one embodiment of the invention, an implantable facet joint device for use in restoring spinal facet joint function comprises a cephalad facet joint element and a caudal facet joint element. The cephalad facet joint element comprises a member adapted to engage a first vertebra, and an artificial cephalad bearing member. The caudal facet joint element comprises a connector adapted for fixation to a second vertebra at a fixation point, and an artificial caudal bearing member adapted to engage the cephalad bearing member. The artificial caudal bearing member can be adapted for a location lateral to the fixation point. The caudal bearing member may be adapted for a location directly lateral to the fixation point. In some embodiments, the fixation point is located on a pedicle of the second vertebra. The caudal bearing member may be generally cup-shaped, and may be configured to have an opening that generally faces medially, posteriorly and superiorly when implanted. 
     In some embodiments of the invention, the facet joint device described above further comprises a second cephalad facet joint element and a second caudal facet joint element. In these embodiments, the second cephalad facet joint element comprises a second member adapted to engage a first vertebra, and a second artificial cephalad bearing member. Similarly, the second caudal facet joint element comprising a second connector adapted for fixation to a second vertebra at a second fixation point, and a second artificial caudal bearing member adapted to engage the second cephalad bearing member. The second artificial caudal bearing member can be adapted for a location lateral to the second fixation point. The first and second fixation points may be on opposite pedicles of the same second vertebra. In some embodiments, the first and second connectors are inter-connected by a crossbar. In some embodiments, the first and second members adapted to engage the first vertebra are inter-connected by a crossbar. 
     In some embodiments of the invention, an implantable facet joint device comprises a cephalad crossbar, a connector element, a first artificial cephalad bearing member and a second artificial cephalad bearing member. In these embodiments, the cephalad crossbar can be adapted to extend mediolaterally relative to a spine of a patient, and the crossbar has opposite first and second ends. The connector element is adapted to connect the crossbar to a first vertebra. Additionally, the first artificial cephalad bearing member is adapted for connection to the first end of the crossbar and adapted to engage a first caudal facet joint element connected to a second vertebra. The second artificial cephalad bearing member is adapted for connection to the second end of the crossbar and adapted to engage a second caudal facet joint element connected to the second vertebra. 
     In some of the embodiments described immediately above, the connector element comprises two stems. These stems may each comprise a bend. In other embodiments, the connector element comprises a single stem. This single stem may be generally U-shaped. The connector element may comprise two cephalad anchors adapted for mounting in the pedicles of the first vertebra. In some embodiments, the cephalad anchors are poly-axial anchors. The device may include at least one stem interconnecting the two anchors and the crossbar. The first and the second caudal facet joint elements may each comprise a generally textured, curved and/or cup-shaped artificial caudal bearing. 
     In some embodiments of the invention, an implantable facet joint device comprises a caudal cross-member, a first artificial caudal bearing member and a second artificial caudal bearing member. In these embodiments, the caudal cross-member is adapted to extend mediolaterally relative to a spine of a patient and adapted to connect to a first vertebra. The first artificial caudal bearing member is adapted for connection to the caudal cross-member, and adapted to engage a first cephalad facet joint element connected to a second vertebra. The second artificial caudal bearing member is adapted for connection to the caudal cross-member at a predetermined spacing from the first bearing member. The second bearing member is also adapted to engage a second caudal facet joint element connected to the second vertebra. 
     In some of the embodiments described immediately above, the device further comprises a pair of pedicle screws adapted to connect the cross-member to the pedicles of the first vertebra. The device may further comprise a cephalad cross-member adapted to extend mediolaterally relative to the spine and adapted to connect to a second vertebra, the cephalad cross-member adapted to support a pair of cephalad bearing members for inter-engaging with the first and the second caudal bearing members. In some embodiments, the cephalad cross-member is adapted to be located generally posteriorly to the caudal cross-member. The device may include an adjustment element adapted to span between the cephalad cross-member and the caudal cross-member for adjusting the relative spacing therebetween. 
     In some of the embodiments described above, the device further comprises a second caudal cross-member, a third artificial caudal bearing member and a fourth artificial caudal bearing member. In these embodiments, the second caudal cross-member is adapted to extend mediolaterally relative to the spine and is adapted to connect to the second vertebra. The third artificial caudal bearing member is adapted for connection to the second caudal cross-member, and is adapted to engage a third cephalad facet joint element connected to a third vertebra. Additionally, the fourth artificial caudal bearing member is adapted for connection to the second caudal cross-member at a predetermined spacing from the third bearing member. The fourth bearing member is also adapted to engage a fourth caudal facet joint element connected to the third vertebra. 
     In some of the embodiments described above, the predetermined spacing between the first and the second caudal bearing members is substantially different than the predetermined spacing between the third and the fourth caudal bearing members. In other embodiments, the predetermined spacing between the first and the second caudal bearing members is substantially the same as the predetermined spacing between the third and the fourth caudal bearing members. In some embodiments, the device comprises at least one member rigidly spanning between a third vertebra and one of the first and the second vertebra to inhibit relative motion therebetween. The first and the second caudal bearing members may comprise laterally facing, generally cup-shaped bearing surfaces. 
     According to some embodiments of the invention, a kit is provided for restoring a functional spine unit at a vertebral level in a spine. The kit may comprise a caudal cross-member, a first artificial caudal bearing member and a second artificial caudal bearing member. In these embodiments, the caudal cross-member is adapted to extend mediolaterally relative to a spine of a patient and is adapted to connect to a first vertebra. The first artificial caudal bearing member is adapted for connection to the caudal cross-member, and is adapted to engage a first cephalad facet joint element connected to a second vertebra. Additionally, the second artificial caudal bearing member is adapted for connection to the caudal cross-member at a predetermined spacing from the first bearing member. The second bearing member is also adapted to engage a second caudal facet joint element connected to the second vertebra. 
     In some of the embodiments described immediately above, the kit further comprises a pair of pedicle screws adapted to connect the caudal cross-member to the pedicles of the first vertebra. The kit may comprise a cephalad cross-member adapted to extend mediolaterally relative to the spine and adapted to connect to a second vertebra. This cephalad cross-member is also adapted to support a pair of cephalad bearing members for inter-engaging with the first and the second caudal bearing members. In some embodiments, the kit comprises an adjustment element adapted to span between the cephalad cross-member and the caudal cross-member for adjusting the relative spacing therebetween. The kit may comprise a second caudal cross-member adapted to receive a third and a fourth caudal bearing member at a predetermined spacing substantially different than the predetermined spacing on the first caudal cross-member. 
     INCORPORATION BY REFERENCE 
     All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: 
         FIG. 1  is a lateral elevation view of a normal human spinal column; 
         FIG. 2A  is a superior view of a normal human lumbar vertebra; 
         FIG. 2B  is a lateral elevational view of two vertebral bodies forming a functional spinal unit; 
         FIG. 2C  is a posterior view of two vertebral bodies forming a functional spine unit and illustrating a coronal plane across a facet joint; 
         FIG. 2D  is a cross-sectional view of a single facet joint in a spinal column taken along a coronal plane; 
         FIG. 2E  is a posterolateral oblique view of a vertebra from a human spinal column; 
         FIG. 3  is a perspective view of the anatomical planes of the human body; 
         FIGS. 4A-B  illustrate an implanted facet replacement device according to one embodiment of the invention from a posterior and lateral perspective; 
         FIGS. 4C-D  illustrate details of a caudal portion of the facet replacement device illustrated in  FIGS. 4A-B ; 
         FIGS. 5A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective; 
         FIGS. 6A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective; 
         FIGS. 7A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective, with the two vertebrae shown schematically; 
         FIG. 7C  illustrates an exemplary inventory kit useful in constructing the facet replacement device illustrated in  FIGS. 7A-B ; 
         FIGS. 8A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective; 
         FIGS. 9A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and inferior perspective; 
         FIGS. 10A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and inferior perspective; 
         FIGS. 11A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective; 
         FIGS. 12A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective; 
         FIG. 12C  illustrates an exemplary inventory kit useful in constructing the facet replacement device illustrated in  FIGS. 12A-B ; 
         FIGS. 13A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective; 
         FIG. 13C  illustrates an exemplary inventory kit useful in constructing the facet replacement device illustrated in  FIGS. 13A-B ; 
         FIGS. 14A-B  illustrate a multilevel implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective; 
         FIGS. 15A-B  illustrate a multilevel implanted facet replacement device according to another embodiment of the invention from a posterior and lateral perspective; 
         FIG. 16  is a perspective view showing a caudal portion of a facet replacement device according to another embodiment of the invention; 
         FIGS. 17A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from an oblique and posterior perspective; 
         FIGS. 18A-B  illustrate an implanted facet replacement device according to another embodiment of the invention from an oblique and posterior perspective; 
         FIG. 19  illustrates an implanted facet replacement device according to another embodiment of the invention from a posterior perspective; 
         FIGS. 20A-C  illustrate an implanted facet replacement device according to another embodiment of the invention from various perspectives; 
         FIGS. 21A-C  illustrate an implanted facet replacement device according to another embodiment of the invention from various perspectives; 
         FIG. 22  illustrates an implanted facet replacement device according to another embodiment of the invention from a posterior perspective; 
         FIG. 23  illustrates an implanted facet replacement device according to another embodiment of the invention from a posterior perspective; 
         FIGS. 24A-C  illustrate a multilevel implanted facet replacement device according to another embodiment of the invention from various perspectives; 
         FIGS. 25A-B  illustrate a multilevel implanted facet replacement device according to another embodiment of the invention from a lateral and posterior perspective; 
         FIG. 26  illustrates an exemplary inventory kit useful in constructing the facet replacement devices illustrated in  FIGS. 22-23 ; 
         FIGS. 27-30  illustrate an implanted facet replacement device attached to a sacrum according to another embodiment of the invention from various perspectives; 
         FIGS. 31-33  illustrate an implanted facet replacement device according to another embodiment of the invention from various perspectives; 
         FIGS. 34A-D  illustrate a caudal bearing assembly according to another embodiment of the invention from a various perspectives; 
         FIGS. 35A-B  are a cross-section and an exploded perspective view showing a caudal bearing housing assembly according to another embodiment of the invention; and 
         FIGS. 36-39  illustrate various translaminar pin to bearing connections according to other embodiments of the invention from side elevational perspectives. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention relates generally to implantable devices, apparatus or mechanisms that are suitable for implantation within a human body to restore, augment, and/or replace hard tissue, soft tissue and/or connective tissue, including bone and cartilage, and systems for treating the anatomic or functional manifestation of injury or diseases, such as spinal pathologies. In some instances, the implantable devices can include devices designed to reinforce, augment and/or replace missing, removed, or resected body parts or structure (and/or some or all of the functions of those body parts or structures). The implantable devices, apparatus or mechanisms are configured such that the devices can be formed from parts, elements or components which alone or in combination comprise the device. The implantable devices can also be configured such that one or more elements or components are formed integrally to achieve a desired physiological, operational or functional result such that the components complete the device. Functional results can include the surgical restoration and functional power of a joint, controlling, limiting or altering the functional power of a joint, and/or eliminating the functional power of a joint by preventing joint motion. Portions of the device can be configured to replace or augment existing anatomy and/or implanted devices (and/or their anatomical functions), and/or be used in combination with resection or removal of existing anatomical structure. 
     The devices of the invention are designed to interact with the human spinal column  10 , as shown in  FIG. 1 , which is comprised of a series of thirty-three stacked vertebrae  12  divided into five regions. The cervical region includes seven vertebrae, known as C1-C7. The thoracic region includes twelve vertebrae, known as T1-T12. The lumbar region contains five vertebrae, known as L1-L5. The sacral region is comprised of five normally-fused vertebrae, known as S1-S5, while the coccygeal region contains four fused vertebrae, known as Co1-Co4. 
     An example of one vertebra is illustrated in  FIG. 2A  which depicts a superior plan view of a normal human lumbar vertebra  12 . Although human lumbar vertebrae vary somewhat according to location, the vertebrae share many common features. Each vertebra  12  includes a vertebral body  14 . Two short boney protrusions, the pedicles  16 ,  16 ′, extend dorsally from each side of the vertebral body  14  to form a vertebral arch  18  which defines the vertebral foramen  19 . 
     At the posterior end of each pedicle  16 , the vertebral arch  18  flares out into broad plates of bone known as the laminae  20 . The laminae  20  fuse with each other to form a spinous process  22 . The spinous process  22  provides for muscle and ligamentous attachment. A smooth transition from the pedicles  16  to the laminae  20  is interrupted by the formation of a series of processes. 
     Two transverse processes  24 ,  24 ′ thrust out laterally, one on each side, from the junction of the pedicle  16  with the lamina  20 . The transverse processes  24 ,  24 ′ serve as levers for the attachment of muscles to the vertebrae  12 . Four articular processes, two superior  26 ,  26 ′ and two inferior  28 ,  28 ′, also rise from the junctions of the pedicles  16  and the laminae  20 . The superior articular processes  26 ,  26 ′ are sharp oval plates of bone rising upward on each side of the vertebrae, while the inferior processes  28 ,  28 ′ are oval plates of bone that jut downward on each side. See also  FIGS. 2B and 2D . 
     The superior and inferior articular processes  26  and  28  each have a natural bony structure known as a facet or facet surface. The superior articular facet  30  faces medially upward, while the inferior articular facet  31  (see  FIGS. 2B-E ) faces laterally downward. When adjacent vertebrae  12  are aligned, the facets  30  and  31 , capped with a smooth articular cartilage and encapsulated by ligaments, interlock to form a facet joint  32 . The facet joints are apophyseal joints that have a loose capsule and a synovial lining. 
     As discussed above, the facet joint  32  is composed of a superior facet and an inferior facet. The superior facet is formed by the vertebral level below the joint  32 , and the inferior facet is formed in the vertebral level above the joint  32 . For example, in the L4-L5 facet joint shown in  FIG. 2B , the superior facet of the joint  32  is formed by bony structure on the L5 vertebra (i.e., a superior articular surface and supporting bone  26  on the L5 vertebra), and the inferior facet of the joint  32  is formed by bony structure on the L4 vertebra (i.e., an inferior articular surface and supporting bone  28  on the L4 vertebra). The angle formed by a facet joint located between a superior facet and an inferior facet changes with respect to the midline of the spine depending upon the location of the vertebral body along the spine  10  ( FIG. 1 ). The facet joints do not, in and of themselves, generally substantially support axial loads unless the spine is in an extension posture (lordosis). As would be appreciated by those of skill in the art, the orientation of the facet joint for a particular pair of vertebral bodies changes significantly from the thoracic to the lumbar spine to accommodate a joint&#39;s ability to resist flexion-extension, lateral bending, rotation and/or shear forces. 
     An intervertebral disc  34  between each adjacent vertebra  12  (with stacked vertebral bodies shown as  14 ,  15  in  FIGS. 2B , C, E) permits gliding movement between the vertebrae  12 . The structure and alignment of the vertebrae  12  thus permit a range of movement of the vertebrae  12  relative to each other.  FIG. 2E  illustrates a posterolateral oblique view of a vertebrae  12 , further illustrating the curved surface of the superior articular facet  30  and the protruding structure of the inferior facet  31  adapted to mate with the opposing superior articular facet. As discussed above, the position of the inferior facet  31  and superior facet  30  varies on a particular vertebral body to achieve the desired biomechanical behavior of a region of the spine. 
     Thus, the overall spine comprises a series of functional spinal units that are a motion segment consisting of two adjacent vertebral bodies (e.g.,  14 ,  15  of  FIGS. 2B , C, E), the intervertebral disc (e.g.,  34  of  FIGS. 2B , C, E), associated ligaments and soft tissues, and facet joints (e.g.,  32  of  FIG. 2D ). See, Posner, I, et al. A biomechanical analysis of the clinical stability of the lumbar and lumbosacral spine. Spine 7:374-389 (1982). 
     As previously described, a natural facet joint, such as facet joint  32  ( FIGS. 2B-D ), has a superior facet  30  and an inferior facet  31  (shown in  FIG. 2B , C, E). In anatomical terms, the superior facet of the joint is formed by the vertebral level below the joint, which can thus be called the “caudad” portion of the facet joint because it is anatomically closer to the tail bone or feet of the person. The inferior facet of the facet joint is formed by the vertebral level above the joint, which can be called the “cephalad” portion of the facet joint because it is anatomically closer to the head of the person. Thus, a device that, in use, replaces the caudad portion of a natural facet joint (i.e., the superior facet  30 ) can be referred to as a “caudad” device. Likewise, a device that, in use, replaces the cephalad portion of a natural facet joint (i.e., the inferior facet  31 ) can be referred to a “cephalad” device. 
     As will be appreciated by those skilled in the art, it can be difficult for a surgeon to determine the precise size and/or shape necessary for an implantable device until the surgical site has actually been prepared for receiving the device. In such case, the surgeon typically would desire to quickly deploy a family of devices and/or device components possessing differing sizes and/or shapes during the surgery. Thus, embodiments of the spinal devices of the present invention include modular designs that are either or both configurable and adaptable. Additionally, the various embodiments disclosed herein may also be formed into a “kit” or system of modular components that can be assembled in situ to create a patient specific solution. As will be appreciated by those of skill in the art, as imaging technology improves, and mechanisms for interpreting the images (e.g., software tools) improve, patient specific designs employing these concepts may be configured or manufactured prior to the surgery. Thus, it is within the scope of the invention to provide for patient specific devices with integrally formed components that are pre-configured. 
     The devices of the present invention are configurable such that the resulting implantable device is selected and positioned to conform to a specific anatomy or desired surgical outcome. The adaptable aspects of embodiments of the present invention provide the surgeon with customization options during the implantation or revision procedure. It is the adaptability of the present devices and systems that also provides adjustment of the components during the implantation procedure to ensure optimal conformity to the desired anatomical orientation or surgical outcome. An adaptable modular device of the present invention allows for the adjustment of various component-to-component relationships. One example of a component-to-component relationship is the rotational angular relationship between an anchoring device and the device to be anchored. Other examples of the adaptability of modular device of the present invention are as described in greater detail below. Configurability may be thought of as the selection of a particular size of component that together with other component size selections results in a “custom fit” implantable device. Adaptability then can refer to the implantation and adjustment of the individual components within a range of positions in such a way as to fine tune the “custom fit” devices for an individual patient. The net result is that embodiments of the modular, configurable, adaptable spinal device and systems of the present invention allow the surgeon to alter the size, orientation, and relationship between the various components of the device to fit the particular needs of a patient during the actual surgical procedure. 
     To prepare the anatomy for implantation of the devices and systems disclosed herein, it may be desirable to alter or remove anatomy from the patient. For example, common ligaments, such as capsular ligaments, anterior longitudinal ligaments, interspinous ligaments, super-spinous ligaments and/or ligamentum flavum may be altered or removed, as well as portions of the cephalad and/or caudad vertebra, including inferior/superior facets, or portions thereof. Alternatively, less-invasive and/or minimally-invasive surgical tools and techniques are provided that, among other things, limit the need for resection and/or alteration of such anatomy, which desirably allows for greater retention of natural anatomical features that can (1) stabilize the spine, thereby desirably reducing loads experienced by the facet replacement device, (2) load-share with the facet joint replacement device in bearing physiological loads, and/or (3) reduce or obviate the need for motion limiters or soft or hard “stops” on the facet replacement devices (as the retained natural anatomy may provide such motion limiting features). 
     In order to understand the configurability, adaptability and operational aspects of the invention, it is helpful to understand the anatomical references of the body  50  with respect to which the position and operation of the devices, and components thereof, are described. There are three anatomical planes generally used in anatomy to describe the human body and structure within the human body: the axial plane  52 , the sagittal plane  54  and the coronal plane  56  (see  FIG. 3 ). Additionally, devices and the operation of devices are better understood with respect to the caudad  60  direction and/or the cephalad direction  62 . Devices positioned within the body can be positioned dorsally  70  (or posteriorly) such that the placement or operation of the device is toward the back or rear of the body. Alternatively, devices can be positioned ventrally  72  (or anteriorly) such that the placement or operation of the device is toward the front of the body. Various embodiments of the spinal devices and systems of the present invention may be configurable and variable with respect to a single anatomical plane or with respect to two or more anatomical planes. For example, a component may be described as lying within and having adaptability in relation to a single plane. For example, an anchoring device may be positioned in a desired location relative to an axial plane and may be moveable between a number of adaptable positions or within a range of positions. Similarly, the various components can incorporate differing sizes and/or shapes in order to accommodate differing patient sizes and/or anticipated loads. 
     Turning back to  FIG. 2D , a vertebral body  14  is depicted in at least partial cross-section along, for example a sagittal plane  54  and a facet joint  32  is depicted in a coronal plane  56 . As will be appreciated, the orientation of a facet joint  32  in any plane of the body changes depending upon the location of a particular joint within the spinal column, this example is provided for illustration purposes only. 
     The facet joint  32 , is formed from a superior articular facet  30  and an inferior articular facet  31 . The inferior articular facet  31  has a cephalad facet surface and the superior articular facet  30  has a caudad facet surface. When healthy and normal, each of these surfaces has an articulating cartilage layer positioned adjacent the facet surfaces to improve the movement of the facet joint  32  in operation. In addition to the caudad facet surface and the cephalad facet surface that comprise the opposing joint surfaces, each of the superior articular facet  30  and the inferior articular facet  31  may have additional surfaces on the sides of the facets. A facet capsule  86  is also provided that surrounds the facet joint  32  and to communicate with the various surfaces on the sides of the superior articular facet  30  and the inferior articular facet  31 . Where the anatomic or functional manifestations of a disease has resulted in a spinal pathology, facet joint degradation can occur, which includes wear of the articulating surface of the facet joint. Normally, the peripheral, cortical rim of the joint is not affected, or is minimally affected. With hypertrophic facets, the mass of cortical bone and action of the osteophytes can make the facet larger than normal as the facet degenerates. When a facet begins to wear, the biomechanics of the functional spine unit are altered, which can cause further damage to the facet joint as well as pain. Moreover, such alteration of the biomechanics can compromise the integrity of the remainder of the functional spinal unit, and lead to intervertebral disc degradation and damage, further facet joint degradation and damage, spondylolisthesis and/or reductions/changes in disc height, as well as the potential occurrence of spinal stenosis (all of which could occur not only in the affected spinal level, but in other spinal levels as well). 
     Turning now to  FIGS. 4A and 4B , isometric views of a modular, configurable and adaptable implantable spinal arthroplasty device  100  are depicted. The spinal arthroplasty device  100  is illustrated implanted into and spanning between cephalad vertebral body  14  and caudal vertebral body  15 . Device  100  is configured to replace the natural facet joints for retaining movement between cephalad vertebral body  14  and caudal vertebral body  15 . 
     The spinal arthroplasty device  100  includes a pair of cephalad anchors  105 ,  105 ′ which attach the cephalad portion of the device to the pedicles of the cephalad vertebral body  14 . Device  100  also includes a pair of caudal anchors  110 ,  110 ′ which attach the caudal portion of the device to the pedicles of the caudal vertebral body  15 . The caudal pedicle anchors  110 ,  110 ′ are supplemented with a caudal crossbar  115 , which can serve to provide extra rigidity to caudal anchors  110 ,  110 ′ and prevent them from being rotated by caudal stem moments. In this exemplary embodiment, crossbar  115  is bendable and has a diameter of 4 mm. Cephalad anchors  105 ,  105 ′ are configured to support cephalad bearing arms or stems  117 ,  117 ′, respectively. Cephalad stems  117 ,  117 ′ in turn support spherical cephalad bearing surfaces  120 ,  120 ′ mounted on their lower distal ends. Cephalad bearing surfaces  120 ,  120 ′ are positioned adjacent to caudal bearing surfaces  125 ,  125 ′. A cephalad crossbar  127  may be provided as shown between cephalad stems  117 ,  117 ′ for extra rigidity and to prevent rotation of cephalad anchors  105 ,  105 ′ and stems  117 ,  117 ′. Cephalad crossbar housings  122 ,  122 ′ may be used as shown to adjustably clamp the ends of crossbar  127  to mid-portions of cephalad stems  117 ,  117 ′. Caudal pedicle anchors  110 ,  110 ′ each support a concave caudal bearing surface  125 ,  125 ′ adjacent to the cephalad bearing surfaces  120 ,  120 ′. With this arrangement, the natural facet joints of the spine ( FIG. 3, 32 ) are replaced by the cooperative metal-on-metal (e.g. cobalt chromium) operation of the cephalad bearing surfaces  120 ,  120 ′ with the caudal bearing surfaces  125 ,  125 ′. 
     Referring to  FIGS. 4C and 4D , details of the caudal portion of device  100  are shown. Caudal bearing surfaces  125 ,  125 ′ are formed on modular bearing elements  230 ,  230 ′. Modular bearing elements  230 ,  230 ′ in turn are connected to pedicle anchors  110 ,  110 ′, such as with mating tapered dovetail surfaces  235 ,  240  as shown. Alternatively, bearing elements may be integrally formed with the pedicle anchors to reduce part count. 
     Pedicle anchors  110 ,  110 ′ are configured to be mounted to pedicles with pedicle screws  245 . Pedicle screws  245  include a driver portion  250  to allow the screw to be rotatably driven into the vertebra with a mating driving tool (not shown). Once a pedicle screw  245  is placed in the vertebra, pedicle anchor body  255  may be slidably attached to the head of screw  245 , such as by a T-shaped slot  260  in body  255  inter-engaging with a flange  265  on the screw head as shown. Crossbar lock  270  may then be placed in the bore of pedicle anchor body  255 . Crossbar lock  270  may include a groove  275  formed in one end for receiving crossbar  115 . The entire pedicle anchor assembly  110  may be secured by inserting threaded fastener  280  in the bore of pedicle anchor body  255  over crossbar  115  and tightening it down. As fastener  280  is turned in the threaded upper portion of the bore of body  255 , fastener  280  bears down on crossbar  115 . Crossbar  115  in turn bears down on crossbar lock  270 , which bears down on the head of screw  245 , thereby locking the crossbar  115 , anchor body  255 , and bearing element  230  onto the pedicle screw  245 . 
     The components of the spinal facet arthroplasty device  100  depicted in  FIGS. 4A-4D  are designed to provide appropriate configurability and adaptability for the given disease state, patient specific anatomy and spinal level where the implant occurs. For example, crossbars  115  and  127  may be selected from a variety of straight, curved or complex shaped crossbars of different lengths depending on the particular application and anatomy of the patient. Cephalad stems  117 ,  117 ′ may also be selected from a variety of lengths or other configurations. Pedicle mounts  105 ,  105 ′  110 ,  110 ′ can be uniaxial as shown. Alternatively, one or more polyaxial mounts (such as shown in  FIGS. 5A-5B ) can be used to provide more positioning options for cephalad bearing surfaces  120 ,  120 ′ and/or caudal bearing surfaces  125 ,  125 ′. Cephalad bearing surfaces  120 ,  120 ′ and/or caudal bearing surfaces  125 ,  125 ′ themselves may be selected from a variety of sizes or configurations. As shown and described, caudal pedicle anchors  110 ,  110 ′ and cephalad pedicle anchors  105 ,  105 ′ may be attached without the use of cement. Alternatively, a bone cement may be used with screws or stems to mount pedicle anchors  110 ,  110 ′ and/or  105 ,  105 ′. 
     The arthroplasty device  100  and the various other devices disclosed herein can be formed of a variety of materials. For example, where the devices have bearing surfaces (i.e. surfaces that contact another surface), the surfaces may be formed from biocompatible metals such as cobalt chromium steel, surgical steel, titanium, titanium alloys, tantalum, tantalum alloys, aluminum, etc. Suitable ceramics and other suitable biocompatible materials known in the art can also be used. Suitable polymers include polyesters, aromatic esters such as polyalkylene terephthalates, polyamides, polyalkenes, poly(vinyl) fluoride, PTFE, polyarylethyl ketone, and other materials that would be known to those of skill in the art. Various alternative embodiments of the spinal arthroplasty device could comprise a flexible polymer section (such as a biocompatible polymer) that is rigidly or semi rigidly fixed to the adjacent vertebral bodies whereby the polymer flexes or articulates to allow the vertebral bodies to articulate relative to one another, as well as combinations of the various metals described herein. 
     Referring now to  FIGS. 5A-5B , another embodiment of an implantable spinal arthroplasty device  500  is shown. Device  500  utilizes similar or identical components to those of device  100  shown in  FIGS. 4A-4D  to span vertebral bodies  14  and  15 , such as cephalad anchors  505 ,  505 ′, caudal anchors  510 ,  510 ′, caudal crossbar  515 , cephalad stems  517 ,  517 ′, cephalad bearing surfaces  520 ,  520 ′, caudal bearing surfaces  525 ,  525 ′, and cephalad crossbar  527 . However, in the embodiment shown in  FIGS. 5A-5B , cephalad crossbar housings  522 ,  522 ′ are mounted in a poly-axial manner to crossbar  527 , and are mounted in a mono-axial manner to cephalad crossbar  527 . Additionally, cephalad bearing surfaces  520 ,  520 ′ are press-fit onto angled studs depending from cephalad crossbar housings  522 ,  522 ′. 
     Referring to  FIGS. 6A-6B , another embodiment of an implantable spinal arthroplasty device  600  is shown. Device  600  utilizes similar or identical components to those of devices  100  and  500  described above: cephalad anchors  605 ,  605 ′, caudal anchors  610 ,  610 ′, caudal crossbar  615 , cephalad stems  617 ,  617 ′, cephalad bearing surfaces  620 ,  620 ′, caudal bearing surfaces  625 ,  625 ′, and cephalad crossbar  627 . In this embodiment, spherical cephalad bearings  620 ,  620 ′ are press fit onto straight studs which depend anteriorly from cephalad crossbar housings  622 ,  622 ′. Cephalad stems  617 ,  617 ′ may be separate rods which interconnect cephalad anchors  605 ,  605 ′ with cephalad crossbar housings  622 ,  622 ′, and may have one or more flat surfaces as shown in  FIGS. 6A and 6B  to inhibit rotation. Alternatively, cephalad anchors  605 ,  605 ′ and cephalad crossbar housings  622 ,  622 ′ may be integrally formed or share common connector components. In this embodiment, cephalad crossbar housings  622 ,  622 ′ are constructed to permit biaxial rotation of cephalad stems  617 ,  617 ′ and cephalad crossbar  627 . As with the previous embodiments, caudal bearing surfaces  625 ,  625 ′ may be mechanically attached to caudal anchor housings  610 ,  610 ′, or may be removably attached thereto, such as with taper locks as previously described. 
     Referring to  FIGS. 7A-7B , another embodiment of an implantable spinal arthroplasty device  700  is shown, with vertebral bodies  14  and  15  shown in a schematic fashion. Device  700  most closely resembles device  500  described above and utilizes similar or identical components: cephalad anchors  705 ,  705 ′, caudal anchors  710 ,  710 ′, caudal crossbar  715 , cephalad stems  717 ,  717 ′, cephalad bearing surfaces  720 ,  720 ′, caudal bearing surfaces  725 ,  725 ′, and cephalad crossbar  727 . In this embodiment, spherical cephalad bearings  720 ,  720 ′ are press fit onto angled studs which depend from cephalad crossbar housings  722 ,  722 ′. Cephalad crossbar  727  has a rectangular cross-section and cylindrical flats on its distal ends. Angled cephalad stems  717 ,  717 ′ may be provided as shown to allow for anterior/posterior adjustment of cephalad bearings  720 ,  720 ′. 
     Referring to  FIG. 7C , a typical inventory set of parts is shown for constructing device  700 . Such an inventory or kit may be provided to a surgical team in the operating room such that appropriate parts may be selected from the kit during an implant procedure to suit the particular situation and anatomy of the patient. 
     Referring to  FIGS. 8A-8B , another embodiment of an implantable spinal arthroplasty device  800  is shown. Device  800  utilizes similar or identical components to those of the devices described above: cephalad anchors  805 ,  805 ′, caudal anchors  810 ,  810 ′, caudal crossbar  815 , cephalad stems  817 ,  817 ′, cephalad bearing surfaces  820 ,  820 ′, cephalad crossbar housings  822 ,  822 ′, caudal bearing surfaces  825 ,  825 ′, and cephalad crossbar  827 . In this embodiment, spherical cephalad bearings  820 ,  820 ′ are press fit onto the distal ends of L-shaped stems  817 ,  817 ′. Caudal bearing cups  825 ,  825 ′ are located laterally outward from caudal anchors  810 ,  810 ′ and may be removably attached thereto with taper locks as shown in  FIG. 8B . 
     Referring to  FIGS. 9A-9B , another embodiment of an implantable spinal arthroplasty device  900  is shown. Device  900  utilizes similar or identical components to those of the devices described above: cephalad anchors  905 ,  905 ′, caudal anchors  910 ,  910 ′, caudal crossbar  915 , cephalad stems  917 ,  917 ′, cephalad bearing surfaces  920 ,  920 ′, caudal bearing surfaces  925 ,  925 ′, and cephalad crossbar  927 . In this embodiment, cephalad crossbar  927  interconnects and extends through cephalad crossbar housings  922 ,  922 ′. Spherical cephalad bearings  920 ,  920 ′ are press fit onto the distal ends of cephalad crossbar  927 . Cephalad crossbar housings  922 ,  922 ′ have poly-axial mounting to cephalad stems  917 ,  917 ′ and fixed mounting to cephalad crossbar  927 . 
     Referring to  FIGS. 10A-10B , another embodiment of an implantable spinal arthroplasty device  1000  is shown. Device  1000  utilizes similar or identical components to those of the devices described above: cephalad anchors  1005 ,  1005 ′, caudal anchors  1010 ,  1010 ′, caudal crossbar  1015 , cephalad stems  1017 ,  1017 ′, cephalad bearing surfaces  1020 ,  1020 ′, crossbar housings  1022 ,  1022 ′, caudal bearing surfaces  1025 ,  1025 ′, and cephalad crossbar  1027 . In this embodiment, cephalad crossbar  1027  has a rectangular cross-section and is integral with cephalad crossbar housings  1022 ,  1022 ′. Cephalad stems  1017 ,  1017 ′ are straight, cylindrical rods having flat portions on their posterior regions. Spherical cephalad bearings  1020 ,  1020 ′ depend anteriorly from caudal crossbar housings  1022 ,  1022 ′. Cephalad anchors  1005 ,  1005 ′ allow for poly-axial adjustment of cephalad stems  1017 ,  1017 ′ relative to cephalad pedicle screws, while caudal anchors  1010 ,  1010 ′ allow for mono-axial adjustment of caudal crossbar  1015  relative to caudal pedicle screws. Caudal bearing cups  1025 ,  1025 ′ may be removably attached to caudal anchors  1010 ,  1010 ′ with taper locks. The arrangement shown in  FIGS. 10A-10B  provides a device  1000  having a low profile. 
     Referring to  FIGS. 11A-11B , another embodiment of an implantable spinal arthroplasty device  1100  is shown. Device  1100  utilizes similar or identical components to those of the devices described above: cephalad anchors  1105 ,  1105 ′, caudal anchors  1110 ,  1110 ′, caudal crossbar  1115 , cephalad stems  1117 ,  1117 ′, cephalad bearing surfaces  1120 ,  1120 ′, caudal bearing surfaces  1125 ,  1125 ′, and cephalad crossbar  1127 . In this embodiment, cephalad crossbar  1127  interconnects and extends through cephalad crossbar housings  1122 ,  1122 ′. Spherical cephalad bearings  1120 ,  1120 ′ are press fit onto the distal ends of cephalad crossbar  1127 . Cephalad stems  1117 ,  1117 ′ are straight, cylindrical rods having flat portions on their posterior regions. Cephalad anchors  1105 ,  1105 ′ allow for poly-axial adjustment of cephalad stems  1117 , 1117 ′ relative to cephalad pedicle screws, while caudal anchors  1110 ,  1110 ′ allow for mono-axial adjustment of caudal crossbar  1115  relative to caudal pedicle screws. In similar embodiments (not shown), the poly-axial features can be removed from cephalad anchors  1105 ,  1105 ′. Caudal bearing cups  1125 ,  1125 ′ may be removably attached to caudal anchors  1110 ,  1110 ′ with taper locks. 
     Referring to  FIGS. 12A-12C , another embodiment of an implantable spinal arthroplasty device  1200  is shown. Device  1200  utilizes similar or identical components to those of the devices described above: cephalad anchors  1205 ,  1205 ′, caudal anchors  1210 ,  1210 ′, caudal crossbar  1215 , cephalad bearing surfaces  1220 ,  1220 ′, caudal bearing surfaces  1225 ,  1225 ′, and cephalad crossbar  1227 . Device  1200  is similar to device  1100  shown in  FIGS. 11A-11B , but has a single, preformed cephalad stem  1217  that spans between cephalad anchors  1205 ,  1205 ′. Cephalad crossbar  1227  is mounted to cephalad stem  1217  by a single, central cephalad crossbar housing  1122 . This central housing arrangement provides a “drop in” cephalad construct and improves the posterior profile of the device by aligning the housing  1122  with the spinous process of the patient.  FIG. 12C  illustrates a typical inventory kit that may be used to construct device  1200  of this embodiment of the invention. 
     Referring to  FIGS. 13A-13C , another embodiment of an implantable spinal arthroplasty device  1300  is shown. Device  1300  utilizes similar or identical components to those of the devices described above: cephalad anchors  1305 ,  1305 ′, caudal anchors  1310 ,  1310 ′, caudal crossbar  1315 , cephalad stem  1317 , cephalad bearing surfaces  1320 ,  1320 ′, caudal bearing surfaces  1325 ,  1325 ′, and cephalad crossbar  1327 . Device  1300  is similar to device  1200  shown in  FIGS. 12A-12B , but uses poly-axial caudal anchors  1310 ,  1310 ′ instead of mono-axial anchors  1210 ,  1210 ′. Such an arrangement allows caudal bearing cups  1325 ,  1325 ′ and caudal crossbar  1315  to be adjusted relative to caudal pedicle screws in a poly-axial manner. This arrangement also improves the inventory potential for caudal construct, as shown in  FIG. 13C . 
     Referring to  FIGS. 14A-14B , a multi-level embodiment of implantable spinal arthroplasty device  1400  is shown. Device  1400  spans across vertebral bodies  14 ′,  14  and  15  and allows for relative movement between them. The lower section  1490  of device  1400  that spans between vertebral bodies  14  and  15  is similar to device  1000  shown in  FIGS. 10A-10B  and described above. Similar reference numerals are used in  FIGS. 14A-14B  to refer to similar or identical elements in  FIGS. 10A-10B , with the reference numerals being incremented by 400. Likewise, the upper section  1495  of device  1400  that spans between vertebral bodies  14  and  14 ′ is also similar to device  1000 , but without a caudal crossbar  1015 . The overlapping central section of device  1400  (affixed to vertebral body  14 ) serves both as the cephalad portion of lower section  1490  and the caudal portion of the upper section  1495 . In other words, central pedicle anchors  1410 ,  1410 ′ mounted to vertebral body  14  support lower cephalad stems  1417 ,  1417 ′, which in turn support lower cephalad crossbar  1427  and lower cephalad bearings  1420 ,  1420 ′. Central pedicle anchors  1410 ,  1410 ′ mounted to vertebral body  14  also support upper caudal bearings  1425 ,  1425 ′. All six vertebral body anchors  1405 ,  1405 ′  1410 ,  1410 ′,  1410 ,  1410 ′ may desirably be of poly-axial construction. Cephalad crossbars  1427  may desirably be integrally formed with their respective cephalad crossbar housings  1422 . 
     With the above arrangement, an arthroplasty device may be constructed to span more than two vertebral bodies using a minimal number of elements. Although three vertebral bodies are shown in  FIGS. 14A-14B , this arrangement may be extended as described to span four, five, six or more vertebral bodies. 
     Referring to  FIGS. 15A-15B , a multi-level embodiment of implantable spinal arthroplasty device  1500  is shown providing inferior and superior spinal fusion. In certain patient conditions, it is desirable to retain relative movement between a pair of vertebral bodies (such as vertebral bodies  14  and  15 , as best seen in  FIG. 15B ) while eliminating relative movement of (e.g. fusing) the vertebral bodies above ( 14 ′) and/or below ( 15 ′) the pair  14  and  15 . The central portion of device  1500  is similar to device  1000  shown in  FIGS. 10A-10B , and serves to replace at least a portion of the natural facet joints between vertebral bodies  14  and  15 . However, instead of employing a caudal crossbar  1015  between caudal anchors  1510 ,  1510 ′ in this embodiment, caudal anchors  1510 ,  1510 ′ instead each support an upper end of a lower bridging stem  1585 ,  1585 ′. Lower bridging stems  1585 ,  1585 ′ depend caudally from caudal anchors  1510 ,  1510 ′ and attach at their lower ends to pedicle anchors  1580 ,  1580 ′ mounted on vertebral body  15 ′. With this arrangement, lower bridging stems  1585 ,  1585 ′ rigidly connect vertebral bodies  15  and  15 ′ and serve to inhibit relative motion therebetween. 
     In a similar fashion to lower bringing stems  1585 ,  1585 ′, upper bridging stems  1575 ,  1575 ′ rigidly connect vertebral bodies  14  and  14 ′ to inhibit relative motion therebetween. The upper ends of upper bridging stems  1575 ,  1575 ′ connect to pedicle anchors  1580 ,  1580 ′ mounted on vertebral body  14 ′. The lower ends of upper bridging stems  1575 ,  1575 ′ connect to stem clamping portions  1570 ,  1570 ′ formed on cephalad anchors  1505 ,  1505 ′ which are mounted on vertebral body  14 . 
     Referring to  FIG. 16 , a fixed-spacing caudal bearing device  1600  is shown. Device  1600  is designed to be mounted to a caudal vertebral body to cooperate with a cephalad bearing device mounted on a cephalad vertebral body, as will be described below. Device  1600  comprises poly-axial pedicle mounting screws  1605 , cross-plate  1610  which spans between screws  1605 , and caudal bearings  1615  and  1615 ′ rigidly mounted to cross-plate  1610  with a predetermined spacing. Alternatively, caudal bearings  1615  and  1615 ′ may be removably mounted to cross-plate  1610  with taper lock joints in a similar manner to embodiments described above. It should be noted that in this embodiment, caudal bearings  1615 ,  1615 ′ are brought closer together medially compared to embodiments disclosed above. A fixed-spacing bearing arrangement such as shown with this embodiment can reduce part inventories and can increase rigidity of the implanted device. 
     Referring to  FIGS. 17A-17B , caudal bearing device  1600  described above is shown mounted on vertebral body  15  in functioning relationship to a cephalad bearing device  1700 . Cephalad bearing device  1700  also comprises a cross-plate  1705  for mounting cephalad bearings  1710  at a predetermined spacing to inter-engage with caudal bearings  1615 ,  1615 ′. Cross-plate  1705  is connected to vertebral body  14  by stems  1715 ,  1715 ′ which span between poly-axial pedicle screws  1720 ,  1720 ′ and cross plate  1705 . Side walls of caudal bearings  1615 ,  1615 ′ are oriented medially to provide clearance for cephalad stems  1715 ,  1715 ′. 
     Referring to  FIGS. 18A-18B , another embodiment of an implantable spinal arthroplasty device  1800  is shown. Device  1800  is similar to device  1700  shown in  FIGS. 17A-17B  and described above, but has caudal bearings  1815 ,  1815 ′ positioned more superiorly. Additionally, cephalad cross-plate  1805  is provided with cross-plate housings  1820 ,  1820 ′ which connect to cephalad stems  1815 ,  1815 ′ with bi-axial degrees of freedom. A removable cap-screw  1825  may be threadedly provided in cephalad cross-plate  1805  to allow device  1800  to be locked in an initial “home position.” 
     Referring to  FIG. 19 , another embodiment of an implantable spinal arthroplasty device  1900  is shown. Device  1900  is similar to device  1800  shown in  FIGS. 18A-18B  and described above, and also has a fixed spacing for caudal bearings  1915 ,  1915 ′. 
     Referring to  FIGS. 20A-20C , another embodiment of an implantable spinal arthroplasty device  2000  is shown. This embodiment has a shortened caudal bearing travel distance as compared to previous embodiments. This embodiment also incorporates flexion stop pegs  2003  between the cephalad cross-plate  2005  and caudal cross-plate  2010 . 
     Referring to  FIGS. 21A-21C , another embodiment of an implantable spinal arthroplasty device  2100  is shown. This embodiment also incorporates fixed bearing spacing, and is a multi-level device, similar to variable bearing spacing multi-level device  1500  shown in  FIGS. 15A-15B . The lower portion  2105  of device  2100  is similar to device  2000  shown in  FIGS. 20A-20B  and permits relative movement between vertebral bodies  14  and  15 . The upper portion  2110  of device  2100  is similar to device  1500  and inhibits relative movement between vertebral bodies  14  and  14 ′. 
     Referring to  FIGS. 22 and 23 , two further embodiments of implantable spinal arthroplasty devices  2200  and  2300  are shown, with vertebral bodies  14  and  15  shown in a schematic fashion. Each of these embodiments is similar to device  2000  shown in  FIGS. 20A-20C . Device  2200  is a more compact arrangement configured for implantation with smaller spinal anatomies, whereas device  2300  is configured for larger anatomies. 
     Referring to  FIGS. 24A-24C , another embodiment of an implantable spinal arthroplasty device  2400  is shown. This embodiment also incorporates a fixed bearing spacing, and is a multi-level device, similar to variable bearing spacing, multi-level device  1400  shown in  FIGS. 14A-14B . With this arrangement, a fixed bearing spacing device may be constructed to span more than two vertebral bodies using a minimal number of elements. Although three vertebral bodies are shown in  FIGS. 24A-24C , this arrangement may be extended to span four, five, six or more vertebral bodies. It can be seen that the components used to construct device  2400  are similar or identical to the components used to construct device  2300  (for larger spinal anatomies) shown in  FIG. 23 . 
     Referring to  FIGS. 25A-25B , another embodiment of an implantable spinal arthroplasty device  2500  is shown. This embodiment is a fixed bearing spacing, multi-level device similar to device  2400  shown in  FIGS. 24A-24C . The upper portion of device  2400  utilizes components similar or identical to those used to construct device  2200  (for smaller spinal anatomies) shown in  FIG. 22 . The lower portion of device  2400  utilizes components similar or identical to those used to construct device  2300  (for larger spinal anatomies) shown in  FIG. 23 . This embodiment exemplifies how the various modular components described herein can be combined in various configurations to suit the anatomy of a particular patient, spinal location and disease state. 
     Referring to  FIG. 26 , one embodiment of an inventory set of parts is shown for constructing any of devices  2000 ,  2200 ,  2300 ,  2400  and  2500  as described above. Such an inventory or kit may be provided to a surgical team in the operating room such that appropriate parts may be selected from the kit during an implant procedure to suit the particular situation. 
     Referring to  FIGS. 27-30 , a lumbar-sacral embodiment of an implantable spinal arthroplasty device  2700  is shown. In this embodiment, caudal bearing assemblies  2705 ,  2705 ′ are connected to the sacrum by screws  2710 ,  2710 ′,  2715 ,  2715 ′. Caudal bearing cups  2720 ,  2720 ′ are positioned such that face laterally. Spherical cephalad bearings  2725 ,  2725 ′ are press-fit on the distal ends of cephalad stems  2727 ,  2727 ′ and extend medially into caudal bearing cups  2720 ,  2720 ′. Proximal ends of cephalad stems  2727 ,  2727 ′ are adjustably received in poly-axial cephalad anchors  2730 ,  2730 ′. Cephalad anchors  2730 ,  2730 ′ in turn are mounted into the pedicles of vertebral body L5. Cephalad crossbar  2735  spans between cephalad anchors  2730 ,  2730 ′ to provide additional rigidity and anti-rotation forces thereto. Cephalad crossbar  2735  is connected to cephalad anchors  2730 ,  2730 ′ by clamping portions  2740 ,  2740 ′, of cephalad anchors  2730 ,  2730 ′. 
     The arrangement of device  2700  allows caudal bearing cups  2720 ,  2720 ′ to capture cephalad bearings  2725 ,  2725 ′ to limit their anterior and posterior movement. Such limited movement may be desirable to prevent or treat retrolisthesis or spondylolisthesis, and may also reduce or eliminate the dislocation of an artificial disc replacement when used concurrently at the same spinal level. 
     Referring to  FIGS. 31-33 , another embodiment of an implantable spinal arthroplasty device  3100  is shown. In this embodiment, cephalad bearings  3105 ,  3105 ′ are positioned with translaminar anchors  3110 ,  3110 ′. Translaminar anchors  3110 ,  3110 ′ pass through the lamina of the superior vertebral body  14  in an inferior-lateral-anterior direction toward caudal bearings  3115 ,  3115 ′ in this embodiment. Cephalad bearings  3105 ,  3105 ′ are secured against inferior surfaces of the lamina as nuts  3120  located with spring washers on superior surfaces of the lamina are tightened on the anchor pins. 
     Caudal bearings  3115 ,  3115 ′ may be attached to adapters  3125 ,  3125 ′ with taper locks as described below. Adapters  3125 ,  3125 ′ in turn are secured to caudal anchors  3130 ,  3130 ′ with recessed cap-screws as shown. In this embodiment, caudal crossbar  3135  spans between caudal anchors  3130  and  3130 ′ and is secured in place by threaded inserts  3140  tightened against flats located on the distal ends of crossbar  3135 . 
     Referring to  FIGS. 34A-34D , an embodiment of a caudal bearing assembly  3400  is shown. Caudal bearing assembly comprises three main pieces: a housing  3405 , adapter  3410  and bearing  3415 . Bearing  3415  has tapered dovetail features on its backside that are slidably received by mating features on adapter  3410  to attach bearing  3415  to adapter  3410 . Adapter  3410  is secured to housing  3405  with a recessed cap-screw, as best seen in  FIG. 34D . Inter-engaging ridges  3420  on the mating surfaces of adapter  3410  and housing  3405  secure adapter  3410  from translational and rotational movement with respect to housing  3405 . 
     Referring to  FIGS. 35A-35B , an embodiment of caudal anchor  3500  and crossbar  3505  attachment is shown. In this embodiment, caudal anchor  3500  comprises a threaded pedicular screw  3510 , a base  3515 , an adapter  3520 , a bearing  3525 , an adapter mounting screw  3530 , a barrel  3535 , a shim  3540  and a set screw  3545 . An enlarged head portion of pedicular screw  3510  is captured in the bottom of bore  3550  in base  3515 . An upper portion  3555  of bore  3550  is inwardly tapered to capture mating inwardly tapered fingers  3560  depending from barrel  3535 . Tapered portion  3555 , fingers  3560  and shim  3540  cooperate to form an infinitely adjustable compression fitting when assembled, as shown in  FIG. 35A . 
     The distal end of crossbar  3505  is provided with an octagonal profile, and the upper end of shim  3540  is provided with a mating profile for receiving the distal end of crossbar  3505 . Caudal anchor  3500  is assembled as shown in  FIG. 35A . When set screw  3545  is threaded into the top of barrel  3535  and tightened down against one of the flats on the distal end of crossbar  3505 , the entire anchor assembly  3500  is secured in place. The compression fitting formed between barrel  3535  and base  3515  prevents crossbar  3505  from rotating about the axis of pedicular screw  3510 . The octagonal flats on crossbar  3505  prevent the crossbar from rotating about an axis perpendicular to screw  3510 . 
     Referring to  FIGS. 36-39 , various embodiments of translaminar pin and bearing interconnections are shown. As can be seen from the figures, in each embodiment the semi-spherical bearing and translaminar pin have inter-engaging features for retaining the bearing on the pin. In  FIG. 39  a detent mechanism is shown for allowing the bearing to be retained on the pin in one of a plurality of positions along the axis of the pin. A series of grooves are provided around the distal end of the pin for this purpose. 
     The invention includes systems that include a single functional spinal unit joint replacement system. The devices, systems and methods provided herein reduce and/or eliminate replacement, repair and/or displacement of the artificial disc replacement device relative to the vertebral bodies during the life of the implantation. By linking disc replacement to the facet replacement, the added benefit of reducing or redistributing the loading of the spinal anchors (pedicle, lamina, spinous process and/or a combination thereof) can be achieved, as well as reducing or obviating the opportunity for a portion of the natural anatomy (i.e. the natural facet joints remaining after artificial disc replacement at a given spinal level) to deteriorate, degenerate and/or biomechanically alter, thereby necessitating further surgical intervention at an operative level. By replacing the entirety of the articulating surfaces at a given spinal level (intervertebral disc and both facets), the present invention allows a surgeon to completely reconstruct the spinal motion segment at a given level. In addition, the removal and eventual replacement of one or more of the facet structures allows for implantation of one or more components of an artificial disc replacement device through the safe, significantly large access path (created by removal of the facet structures), and into the intervertebral space for the posterior or posterior/lateral implantation of an artificial disc. 
     In some embodiments it may be desirable to incorporate artificial ligaments between the articulating arms and/or the treated vertebral bodies. Additionally, in some embodiments it could be desirable to incorporate a flexible capsule around some or all of the facet/articulating joint or its surfaces. Alternatively, the facet replacement device can be adapted to incorporate multiple attachment points (apertures, holes, hooks, etc.) for attachment of existing ligaments, tendons and/or other soft or hard tissues at the conclusion of the surgical procedure to promote healing and further stabilization of the affected levels. 
     The devices and components disclosed herein can be formed of a variety of materials, as would be known in the art. For example, where the devices have bearing surfaces (i.e. surfaces that contact another surface), the surfaces may be formed from biocompatible metals such as cobalt chromium steel, surgical steel, titanium, titanium alloys (such as Nitinol), tantalum, tantalum alloys, aluminum, etc. Suitable ceramics, including pyrolytic carbon, and other suitable biocompatible materials known in the art can also be used. Suitable polymers include polyesters, aromatic esters such as polyalkylene terephthalates, polyamides, polyalkenes, poly(vinyl) fluoride, PTFE, polyarylethyl ketone, and other materials that would be known to those of skill in the art. Various alternative embodiments of the spinal devices and/or components could comprise a flexible polymer section (such as a biocompatible polymer) that is rigidly or semi rigidly fixed such that the polymer flexes or articulates to allow the vertebral bodies to articulate relative to one another. 
     Various embodiments of the present invention relate to a total spine joint replacement system comprising a modular facet joint replacement in combination with an artificial spinal disc replacement device. Virtually all of the various embodiments disclosed here could be utilized, in various ways, in combination with artificial disc replacement devices, as well as nucleus repair systems and replacement devices, interbody spacers, dynamic stabilization devices, articulating rod and screw systems, posterior ligament or annular repair and/or augmentation devices, interspinous spacers, facet resurfacing devices, and the like, with varying utility. If desired, a given facet joint replacement system may incorporate components that are particularly well suited for use with various other spinal systems, including all those described above. If desired, such components could include articulating bearing surfaces (or other components, including mating features) designed to compliment, reduce, control, increase and/or modify the motions allowed and/or prevented by the various spinal systems, including, in the case of artificial disc replacement devices, modular bearings designed to compliment the motions provided by such disc replacement devices. 
     Various embodiments of the present invention desirably link the facet replacement prosthesis with the artificial disc replacement prosthesis in some manner. This link can be integral, such that the two components are “hard linked” together (either inflexibly, or flexibly—to allow and/or disallow articulation between components), or the components can be “soft linked” together, to allow movement and/or displacement between the components to some desired limit. If desired, at least one end of the linking device can comprise a polyaxial-type connection to connect to one or components of the facet replacement prosthesis. In alternate embodiments, the link may similarly pass through one or more openings formed through the various facet replacement components. 
     Desirably, the limitations and disadvantages inherent with many prior art facet replacement systems, as well as many artificial disc replacement systems, can be reduced, minimized and/or eliminated by the combination of such systems into a single, functional spinal unit joint replacement system. For example, the opportunity for the disc replacement to migrate and/or displace relative to the vertebral bodies during the life of the implantation may be reduced and/or eliminated by linking the disc replacement to the facet replacement prosthesis. Similarly, linking the disc replacement to the facet replacement may confer the added benefit of reducing (or redistributing) loading of the anchors (pedicle, lamina, spinous process and/or some combination thereof) of the facet replacement prosthesis, or visa versa (attachment of the disc replacement to the facet replacement affects loading of the disc replacement). Moreover, the forces acting on one component of the device (i.e., the artificial disc replacement device) may be balanced and/or negated by various forces acting on another component of the device (i.e., the facet joint replacement device), thus reducing and/or balancing the forces acting on the entire construct and/or its anchoring devices. In a similar manner, the types of motion provided by the artificial disc replacement device (i.e., constrained, partially-constrained and/or unconstrained motion), may be altered and/or modified by the facet replacement device. 
     In one embodiment, the connection mechanism between the linkage and the artificial disc replacement can further serve to augment the stability and long-term viability of the artificial disc replacement. In this embodiment, the linkage comprises a longitudinally-extending arm which travels along the endplate of the vertebral body, through an opening formed in the artificial disc replacement, and extending further along the endplate. Desirably, this arm will serve to distribute loading of the disc on the endplate, reducing and/or eliminating subsidence of the disc replacement into and/or through the vertebral endplate (in a manner similar to using a rescue ladder on thin ice to distribute the weight of the rescuer). Various embodiments of the arm can comprise a flattened or half-circular cross-section, with the flattened section (towards the endplate) comprising a bioactive and/or in-growth surface to promote biofixation to the surrounding tissues. The linkage arms could comprise flexible or rigid materials. The artificial disc devices could be of one, two or more piece construction. 
     In one alternate embodiment, the linkage arms are desirably non-parallel and/or non symmetric between the upper and lower linkage arms (which are linked to the upper and lower components of the disc replacement, respectively), so as to provide both lateral and anterior/posterior support to prevent migration of the disc replacement device and/or more easily allow controlled displacement of the disc replacement upon manipulation of the linkage arms. 
     If desired, a displaceable/repositionable disc replacement system (as described in the paragraph above) could incorporate one or more “settings” that would allow the physician to control, limit, reduce, increase or prevent motion of the disc replacement and/or facet replacement devices (to promote some clinical benefit, including inducing spinal fusion, limit articulation to promote healing of spinal tissues, limit or allow micro motion to promote bony in-growth into devices, or some other desired clinical outcome). 
     In various embodiments, the linkage between the facet replacement prosthesis and the disc replacement device facilitates positioning (or repositioning) of the respective prosthesis/device relative to each other, to more easily allow matching (or compatibility) of the kinematics and/or performance characteristics of the prosthesis/devices to each other (desirably, to emulate the natural spinal joint). 
     In various embodiments, the disc replacement device could incorporate openings or other docking features that could be utilized, at a later date (such as, for example, during a subsequent surgical procedure), to attach a facet replacement device (as disclosed herein) to the disc replacement. For example, where the disc replacement has been implanted, and the patient has healed from that surgery, but suffers spinal degeneration in the future (such as, for example, degenerated facets, spinal stenosis and/or spondylolytic slip of the treated spinal level), the level can be reopened, the facet replacement device attached to the existing disc replacement implant, and the surgical procedure completed. A similar arrangement could be contemplated for a facet replacement device that is initially implanted with openings or docking features that are later utilized during subsequent implantation of an artificial disk replacement prosthesis. 
     Various alternative embodiments of the present invention relate to laminar and/or pedicle based systems for replacing natural facets, the systems anchored to the vertebral bodies, with or without using cement and/or bony ingrowth surfaces to augment fixation. 
     As will be appreciated by those skilled in the art, the various embodiments disclosed herein can be adapted to account for location, length and orientation of, for example, the passage created by the surgeon during implantation. The various embodiments can also be adapted to account for an individual patient&#39;s anatomical constraints. Thus, a limited number of component sizes and/or shapes can be configured from a kit to accommodate a large variety of anatomical variations possible in a patient. For example, a kit including a cephalad implant can include cephalad implants having various lengths from 20 mm to 70 mm, in, for example, 5 or 10 mm increments to accommodate passages/lamina having different lengths/thicknesses. Similarly the depth of apertures that accommodate a component can also be adapted to accommodate a patient. 
     Another advantage of various embodiments is that the use of the lamina and/or spinous process as an anchor point for the device enables the device to be implanted while avoiding the pedicles of the vertebral body. Alternatively, it may be desirous to utilize the pedicles of the vertebral body as an anchor point for the device while avoiding the lamina and spinous process (such as where a complete laminectomy has removed some or all of the lamina at a given spinal level). In various embodiments, the combination of translaminar and pedicular attachment (or a hybrid of both) may be most advantageous to the patient. For example, where facet replacement devices are implanted into multiple spinal levels, such as implantation of facet replacement devices across each of the L4-S1 levels, the use of a cephalad translaminar facet replacement device (in the L4 vertebra) in combination with a caudad pedicular-anchored facet replacement device (in the L5 vertebra) may be used in the L4-L5 level, while the use of a cephalad pedicle-anchored facet replacement device (in the L5 vertebra—potentially utilizing the same pedicle anchors as for the caudad components of the L4-L5 level) in combination with a caudad pedicular-anchored device (in the sacrum) may be used in the L5-|S1 level. Such an arrangement would thus obviate the need to use the significantly weaker L5 lamina as an anchoring point, yet allow multiple level replacement of the facet joints. Such a hybrid device could, of course, similarly be used in conjunction with all manner of spinal treatment devices, including artificial disc replacements of one or more spinal levels, annular repair, nucleus replacement, dynamic stabilization, ligament repair and replacement, interspinous spacer, articulating rod and screw systems, and/or adjacent level fusion devices. 
     Various of the systems disclosed herein may be particularly well-suited for less-invasive and/or minimally-invasive insertion. For example, a facet replacement device anchored translaminarly may be implanted into the cephalad lamina utilizing a minimally-invasive or “needle-stick” approach (similar to those utilized in the placement of translaminar facet screws), and the caudad portions of the facet can be accessed through a pair of less-invasive openings or ports to allow removal of resected tissues and/or placement of caudad facet replacement components. Such placement could conceivable be less invasive than the pedicle-based placement of numerous dynamic-stabilization systems, including the Dynesys dynamic stabilization system commercially available from Zimmer Corporation. 
     Additional disclosure useful in understanding the scope and teaching of the invention as it relates to intervertebral discs is in U.S. Patent Pubs. US 2005/0055096 A1 to Serhan et al., for Functional Spinal Unit Prosthetic; and US 2005/0033434 A1 to Berry for Posterior Elements Motion Restoring Device. 
     Further disclosures useful in understanding the scope and teaching of the invention are included in U.S. Pat. No. 6,610,091, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; U.S. Publication Nos. US 2005/0283238 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2005/0234552 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2005/0267579 A1, to Mark A. Reiley, et al., for Implantable Device For Facet Joint Replacement; US 2006/0009849 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2006/0009848 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2006/0009847 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2004/0006391 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2004/0111154 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2004/0049276 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2005/0251256 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2004/0049273 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2004/0049281 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2004/0049275 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; U.S. Pat. No. 6,949,123 B2, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; U.S. Publication Nos. US 2004/0049274 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2004/0049278 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2004/0049277 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2005/0137706 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2005/0137705 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2005/0149190 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2005/0043799 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; US 2002/0123806 A1, to Mark A. Reiley, for Facet Arthroplasty Devices and Methods; U.S. Pat. No. 6,974,478, to Mark A. Reiley, et al., for Prostheses, Systems, and Methods for Replacement of Natural Facet Joints with Artificial Facet Joint Surfaces; US 2005/0240265 A1, to Mark Kuiper, et al., for Crossbar Spinal Prosthesis Having a Modular Design and Related Implantation Methods; US 2005/0119748 A1, to Mark A. Reiley, et al., for Prostheses, Systems, and Methods for Replacement of Natural Facet Joints with Artificial Facet Joint Surfaces; US 2005/0027361 A1, to Mark A. Reiley for Facet Arthroplasty Devices and Methods; US 2005/0240266 A1, to Mark Kuiper, et al., for Crossbar Spinal Prosthesis Having a Modular Design and Related Implantation Methods; US 2005/0261770 A1, to Mark Kuiper, et al., for Crossbar Spinal Prosthesis Having a Modular Design and Related Implantation Methods; US 2004/0230201 A1, to Hansen Yuan, et al., for Prostheses, Systems, and Methods for Replacement of Natural Facet Joints with Artificial Facet Joint Surfaces; US 2005/0143818 A1, to Hansen Yuan, et al., for Prostheses, Systems, and Methods for Replacement of Natural Facet Joints with Artificial Facet Joint Surfaces; US 2005/0010291 A1, to David Stinson, et al., for Prostheses, Systems, and Methods for Replacement of Natural Facet Joints with Artificial Facet Joint Surfaces; U.S. application Ser. No. 11/275,447 to David Stinson, et al., for Prostheses, Systems, and Methods for Replacement of Natural Facet Joints with Artificial Facet Joint Surfaces; US 2004/030304 A1, to Hansen Yuan, et al., for Prostheses, Systems, and Methods for Replacement of Natural Facet Joints with Artificial Facet Joint Surfaces; US 2005/0131406 A1, to Mark A. Reiley, et al., for Polyaxial Adjustment of Facet Joint Prostheses; US 2005/0240264A1, to Leonard Tokish, et al., for Anti-rotation Fixation Element for Spinal Prostheses; US 2005/0235508 A1, to Teena M. Augostino, et al., for Facet Joint Prostheses Measurement and Implant tools; U.S. application Ser. No. 11/236,323, to Michael J. Funk, For Implantable Orthopedic Device Component Selection Instrument and Methods; U.S. application Ser. No. 11/206,676, to Richard Broman, et al., for Implantable Spinal Device Revision System; US 2006/0041211 A1, to Teena M. Augostino, et al., for Adjacent Level Facet Arthroplasty Devices, Spine Stabilization Systems, and Methods; US 2006/0041311 A1, to Thomas J. McLeer for Devices and Methods for Treating Facet Joints; U.S. application Ser. No. 11/140,570, to Thomas J. McLeer, for Methods and Devices for Improved Bonding to Bone; and Ser. No. 11/244,420, to Thomas J. McLeer, for Polymeric Joint Complex and Methods of Use. 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.