Occipito-cervical stabilization system and method

1. Field of the Invention

The present invention generally relates to spinal fixation systems and the like, and in more particular applications, to systems that fixate a portion of the skull to the spine, typically the cervical spine, for correction, fixation, and/or stabilization of a human spine.

2. Description of the Related Art

Spinal fixation, such as lumbar sacral fusion and the correction of spinal deformities such as scoliotic curves, is a well known and frequently used medical procedure. Pedicle, lateral, and oblique mounting devices may be used to secure corrective spinal instrumentation to a portion of the spine that has been selected to be fused by arthrodesis.

A spinal fixation system typically includes corrective spinal instrumentation that is attached to selected vertebra of the spine by screws, hooks, and clamps. The corrective spinal instrumentation includes spinal rods or plates that are generally parallel to the patient's back. The corrective spinal instrumentation may also include transverse connecting rods that extend between neighboring spinal rods. Spinal fixation systems are used to correct problems in the lumbar and thoracic portions of the spine, and are often installed posterior to the spine on opposite sides of the spinous process and adjacent to the transverse process.

Various types of screws, hooks, and clamps have been used for attaching corrective spinal instrumentation to selected portions of a patient's spine. Examples of pedicle screws and other types of attachments are illustrated in U.S. Pat. Nos. 4,763,644; 4,805,602; 4,887,596; 4,950,269; and 5,129,388. Each of these patents is incorporated by reference as if fully set forth herein.

Fixation of the skull to the cervical spine may be used to treat trauma to the neck, degenerative diseases such as rheumatoid arthritis, and pain that is otherwise unresponsive to treatment. Current implantable devices designed to immobilize the skull with respect to the upper cervical spine have to be individually tailored. Often, such devices are assemblies of several components not designed specifically for fusing the cervical spine to the skull. However, devices specifically designed for fusing the cervical spine to the skull are currently being introduced. U.S. Pat. No. 6,146,382 issued to John Hurlbert on Nov. 14, 2000, shows one such device and is incorporated herein by reference as if full set forth herein.

In accordance with one feature of the invention, a system is provided for mechanically fixating a region of a skull to a portion of a spine. The system includes a plate configured to contact the region of the skull and be secured thereto, a spinal rod configured to extend from a location adjacent to the plate for connection thereto to a location adjacent at least one vertebra for connection thereto, the rod forming an angle φ with respect to the plate about a transverse axis, and a variable connection configured to secure the rod to the plate. The variable connection has a first mode connecting the rod and the plate wherein the angle φ can be freely varied without requiring deformation of the rod and the plate and a second mode connecting the rod and the plate wherein the rod and the plate are locked at a particular value of the angle φ selected to maintain a desired curvature of the spine.

As one feature, the connection is configured to also allow the rod to be adjusted laterally with respect to the plate in the first mode without requiring deformation of the rod and the plate, and to be locked at a lateral position relative to the plate in the second mode.

According to one feature, the connection is configured to also allow the rod to be adjusted longitudinally with respect to the plate in the first mode without requiring deformation of the rod and the plate, and to be locked at a longitudinal position relative to the plate in the second mode.

In one feature, the connection is configured to allow a second angle formed between the rod and the plate to be adjusted in the first mode without requiring deformation of the rod and the plate, and for the rod and the plate to be locked at a particular value of the second angle in the second mode.

In accordance with one feature, the variable connection includes a lateral arm integral with the plate and extending laterally along the transverse axis relative to the spine, and a connector including a body having a transverse opening configured to receive the arm and a longitudinal opening configured to receive a proximate portion of the rod adjacent the plate. The transverse opening is configured to pivot freely about the transverse axis in the first mode and to lock to the arm in the second mode.

As one feature, the lateral arm and the transverse opening are configured to also allow the connector to be adjusted laterally with respect to the plate in the first mode without requiring deformation of the rod and the plate, and to be locked at a lateral position relative to the plate in the second mode.

In one feature, the longitudinal opening is configured to also allow the rod to be adjusted longitudinally with respect to the plate in the first mode without requiring deformation of the rod and the plate, and to be locked at a longitudinal position relative to the plate in the second mode.

According to one feature, the lateral arm and the transverse opening are configured to allow a second angle formed between the rod and the plate to be adjusted in the first mode without requiring deformation of the rod and the plate, and for the rod and the plate to be locked at a particular value of the second angle in the second mode.

In accordance with one feature, the body has a lock opening connecting the transverse and longitudinal openings and extending normal to the transverse and longitudinal openings. The connector further includes a clamp plug configured to be received in the lock opening at a location between the transverse and longitudinal openings, and a lock configured to engage the lock opening and clamp the clamp plug, the lateral arm, and the rod in the second mode.

As one feature, the lateral arm has a first set of spline teeth and the plug has a second set of spline teeth, the first and second sets of spline teeth being disengaged in the first mode and engaged in the second mode.

In one feature, the lock has external threads and the locking opening has internal threads that mate with the lock in both the first and second modes.

According to one feature, the body has first and second lock openings, with the first lock opening extending into the transverse opening, and second lock opening extending into the longitudinal opening. The connector further includes first and second locks. The first lock is configured to engage the first lock opening and clamp the lateral arm to the body, and the second lock is configured to engage the second lock opening and clamp the rod to the body.

As a further feature, each of the locks have external threads and each of the locking openings has internal threads that mate with the corresponding lock in both the first and second modes.

In accordance with one feature, the system further includes a second spinal rod and a second variable connection. The second spinal rod is configured to extend from a location adjacent to the plate for connection thereto to a location adjacent at least one vertebra for connection thereto. The first and second rods are positioned on laterally opposite sides of the plate from each other. The second variable connection is configured to secure the second rod to the plate, with the second connection having a first mode connecting the second rod and the plate wherein an angle formed between the second rod and the plate can be freely varied without requiring deformation of the second rod and the plate, and a second mode connecting the second rod and the plate wherein the second rod and the plate are locked at a particular value of the angle selected to maintain a desired curvature of the spine.

In accordance with one feature of the invention, a system is provided for mechanically fixating a region of a skull to a portion of a spine. The system includes a plate configured to contact the region of the skull and be secured thereto, a spinal rod configured to extend from a location adjacent to the plate for connection thereto to a location adjacent at least one vertebra for connection thereto, and a variable connection configured to secure the rod to the plate. The connection has first and second modes connecting the rod and the plate. In the first mode, a relative position of the rod and the plate is adjustable with respect to at least four degrees of freedom of motion without requiring deformation of the rod and the plate. In the second mode, the rod and the plate are locked in a particular relative position with respect to the at least four degrees of freedom of motion to maintain a desired curvature of the spine.

As one feature, the variable connection is configured to allow adjustment of the relative position for the rod and the plate with respect to a fifth degree of freedom of motion in the first mode without requiring deformation of the rod and the plate.

According to one feature, one of the degrees of freedom of motion is a rotation about a laterally extending axis.

In one feature, another one of the degrees of freedom of motion is a rotation about an axis that is perpendicular to both a laterally extending axis and a longitudinally extending axis.

As one feature, another one of the degrees of freedom of motion is a translation along the laterally extending axis.

In accordance with one feature, another one of the degrees of freedom of motion is a translation along a longitudinally extending axis.

According to one feature, another one of the degrees of freedom of motion is a rotation about a longitudinally extending axis.

As one feature, the variable connection includes a lateral arm integral with the plate and extending laterally relative to the spine, and a connector including a body having a transverse opening configured to receive the arm and a longitudinal opening configured to receive a proximate portion of the rod adjacent the plate. The transverse opening is configured to pivot about the arm and slide along the arm in the first mode and to lock to the arm in the second mode. The longitudinal opening is configured to allow the rod to rotate about a longitudinal axis defined by the rod and to slide along the longitudinal axis in the first mode and to lock to the rod in the second mode.

In one feature, the transverse opening is configured to pivot relative to the arm about an axis perpendicular to both the longitudinal axis and a laterally extending axis defined by the arm in the first mode.

According to one feature, the system further includes a second spinal rod and a second variable connection. The second rod is configured to extend from a location adjacent to the plate for connection thereto to a location adjacent at least one vertebra for connection thereto, with the first and second rods positioned on laterally opposite sides of the plate from each other. The second variable connection is configured to secure the second rod to the plate, the second connection having first and second modes connecting the second rod and the plate. In the first mode, a relative position of the second rod and the plate is adjustable with respect to at least four degrees of freedom of motion without requiring deformation of the second rod and the plate. In the second mode, the second rod and the plate are locked in a particular relative position with respect to the at least four degrees of freedom of motion to maintain a desired curvature of the spine.

In accordance with one feature of the invention, a method is provided for coupling a plate to a rod in a system where the plate is to be secured to a region of a skull and the rod is to be secured to at least one vertebra of a spine. The method includes the steps of:

connecting the rod to the plate so that there is a relative angle φ formed between the rod and a plane defined by the plate;

adjusting the relative angle φ to a particular value of the angle φ selected to maintain a desired curvature of the spine without requiring deformation of the rod or the plate; and

the rod and the plate to prevent movement from the particular value of the angle φ.

As one feature, the method further includes the step of adjusting a lateral position of the rod relative to the plate without requiring deformation of the rod or the plate.

In one feature, the method further includes the step of adjusting a longitudinal position of the rod relative to the plate without requiring deformation of the rod or the plate.

According to one feature, the method further includes the step of adjusting an angular position of the rod relative to the plate about an axis that is perpendicular to both a laterally extending axis and a longitudinally extending axis without requiring deformation of the rod or the plate.

As one feature, the method further includes the step of adjusting an angular position of the rod relative to the plate about a longitudinal axis defined by the rod without requiring deformation of the rod or the plate.

According to one feature, the method further includes at least three of the following steps:

adjusting a lateral position of the rod relative to the plate without requiring deformation of the rod or the plate;

adjusting a longitudinal position of the rod relative to the plate without requiring deformation of the rod or the plate;

adjusting an angular position of the rod relative to the plate about an axis that is perpendicular to both a laterally extending axis and a longitudinally extending axis without requiring deformation of the rod or the plate; and

an angular position of the rod relative to the plate about a longitudinal axis defined by the rod without requiring deformation of the rod or the plate.

In accordance with one feature of the invention, a method is provided for coupling a plate to a rod in a system where the plate is to be secured to a region of a skull and the rod is to be secured to at least one vertebra of a spine. The method includes the steps of:

connecting the rod to the plate;

adjusting a relative position of the rod and the plate with respect to at least four degrees of freedom of motion; and

locking the rod and the plate at a particular relative position with respect to the at least four degrees of freedom of motion to maintain a desired curvature of the spine.

As one feature, one of the degrees of freedom of motion is a rotation about a laterally extending axis.

In one feature, another one of the degrees of freedom of motion is a rotation about an axis that is perpendicular to both a laterally extending axis and a longitudinally extending axis.

According to one feature, another one of the degrees of freedom of motion is a translation along the laterally extending axis.

As one feature, another one of the degrees of freedom of motion is a translation along a longitudinally extending axis.

In accordance with one feature, another one of the degrees of freedom of motion is a rotation about a longitudinally extending axis.

In one feature, the adjusting step is performed after the connecting step and before the locking step.

Other features, objects, and advantages of the invention will become apparent after a detailed review of the entire specification, including the appended claims and drawings.

FIGS. 1 and 2 depict an occipito-cervical spinal fixation system embodying the present invention in use, with FIG. 1 being a view looking upward along a portion of a spinal column toward an occiput of a skull, and FIG. 2 being a lateral view;

FIG. 3 is a perspective view showing selected components of the fixation system of FIGS. 1 and 2 ;

FIG. 4 is a plan or posterior view of the fixation system of FIG. 3 ;

FIG. 5 is a bottom view taken from line 5 - 5 in FIG. 4 ;

FIG. 6 is a side or lateral view taken from 6 - 6 in FIG. 4 ;

FIG. 7 an exploded, perspective view showing selected components of the fixation system of FIGS. 1-6 ;

FIG. 8 is a section view taken from line 8 - 8 in FIG. 4 ;

FIG. 9 is a perspective view showing alternate embodiments for selected components of the fixation system;

FIG. 10 is a perspective view showing another alternate embodiment for selected components of the fixation system; and

FIG. 11 is a side or lateral section view taken from line 11 - 11 in FIG. 10 .

With reference to FIGS. 1 and 2 , an occipito-cervical spinal fixation system 10 is shown for mechanically fixating a region of a skull 12 to a portion of a spinal column 14 . The system 10 includes a plate 20 , at least one spinal rod 22 , (but more typically two of the spinal rods 22 ) and a variable connection, shown generally by arrow 24 , for each spinal rod 22 .

The plate 20 is configured to contact the occiput or occipital bone 16 of the skull and be secured thereto. The spinal rod 22 is configured to extend from a location adjacent the plate 20 for connection thereto to a location adjacent at least one of the vertebra 30 of the spine 14 for connection thereto. The variable connection 24 is configured to connect the rod 22 to the plate 20 in first and second modes, with the first mode connecting the plate 20 and rod 22 while allowing the relative position of the rod 22 to the plate 20 to be adjusted without requiring deformation of the rod 22 and the plate 20 , and the second mode locking the plate 20 and the rod 22 at a particular relative position to maintain a desired positioning of the skull 20 and spine 14 . In this regard the components of the fixation system are preferably configured to substantially immobilize the skull 12 with respect to the spinal column 14 during use with the connection 24 in the second mode. The components of the fixation system 10 are preferably made from a suitable biocompatible material, such as titanium or stainless steel.

The plate 20 preferably includes a plurality of openings 36 formed therein for receiving connecting members 38 . During use, connecting members 38 may be inserted into holes formed in the skull 12 to secure the plate 20 to the occiput 16 such that movement of the skull 12 with respect to a portion of the spine is inhibited. In this regard, connecting members 38 preferably are a suitable bone screw, many of which are known.

While any shape may be used for the plate 20 , it is preferred that the plate 20 have a shape that generally conforms to the occiput 16 , with the illustrated horseshoe shape being highly preferred because it offers multiple options for placement of the openings 36 and the associated connecting members 38 and is compatible with the use of two laterally positioned rods 22 , which is typical of most spinal fixation systems. It is also preferred that the plate 20 include a central portion 40 that extends longitudinally to provide multiple possible locations for the openings 36 and the associated connecting members 38 central to the occiput 16 .

The rod 22 supports and preferably immobilizes one or more levels of the spine 14 and can be of any suitable construction, many of which are known. Typically, as shown in the illustrated embodiment, the rod 22 will be in the form of a straight, cylindrically shaped metallic rod extending along a longitudinal axis 42 and formed of a suitable biocompatible material that can be deformed along its length as required to conform to the patient morphology. However, it should be understood that pre-bent or pre-deformed rods and/or noncylindrical rods can also be used in the system 10 . The rod 22 has a proximate end portion 44 that is adjacent the plate 20 for connection thereto, and a length extending to a distal end portion 46 adjacent at least one of the vertebra 30 . Typically, at least the distal end 46 of the rod 22 , and potentially other portions of its length, will be affixed to at least one of the vertebra 30 using a suitable anchoring system, many of which are known and which will typically include a bone screw or bolt and some sort of rod connector that is either integral with the bone screw or otherwise connectable to the bone screw.

The variable connection 24 includes a lateral arm 50 and a connector 52 . Preferably, the lateral arm 50 is formed integral with the plate 20 and extends laterally along a transverse axis 54 relative to the spine. Preferably, in use, the arm 50 and axis 54 are normal to the mid-sagittal plane, shown schematically by dashed line 56 in FIG. 1 and to the longitudinal axis, shown schematically at 58 in FIG. 1 , of the spine 14 lying in the mid-sagittal plane. The connector 52 connects the arm 50 and the rod 22 and allows for adjustment of the relative position between the arm 50 and the rod 22 while the rod 22 and the arm 50 are connected in the first mode.

As best seen in FIG. 7 , the connector 52 includes a body 62 having a transverse opening 64 configured to receive the arm 50 , a longitudinal opening 66 configured to receive the proximate end portion 44 of the rod 22 , and a lock opening 68 , preferably extending along an axis 69 that is aligned with and perpendicular to both the transverse and longitudinal openings 64 , 66 to connect the transverse and longitudinal openings 64 , 66 . Preferably, the transverse opening 64 is oversized at each end with respect to the outer surface of the lateral arm 50 in order to allow pivoting of the body 62 on the arm 50 about the axis 69 in the first mode. The connector 52 further includes a clamp plug 70 and a lock 72 that are received in the lock opening 68 and preferably are configured to operate in the opening 68 to allow free rotational and translational movement of the arm 50 and the rod 22 in the respective openings 64 and 66 in the first mode, and to clamp the arm 50 and the rod 22 against rotational and translational movement in the respective openings 64 and 66 in the second mode.

As best seen in FIG. 8 , the clamp plug 70 is configured to be received in the lock opening 68 at a location between the transverse and longitudinal openings 64 , 66 , and the lock 72 is configured to engage the lock opening 68 and clamp the clamp plug 70 , the lateral arm 50 , and the rod 22 in the second mode. As best seen in FIG. 7 , the lock 72 is preferably a threaded fastener, such as set screw, that has external threads 74 which engage internal threads 76 formed in an upper portion of the lock opening 68 , and a drive feature 78 that can be engaged by a tool to rotate the lock 72 relative to the body 62 . The clamp plug 70 preferably has a surface 80 that abuts the outer surface of the rod 22 in the second mode, and further has a U-shaped surface 82 for receiving the lateral arm 50 , with the surface 82 being shaped to conform to the outer periphery of the lateral arm 50 . As best seen in FIGS. 7-8 , in a preferred embodiment, the surface 82 includes a plurality of spline teeth 84 that mate with corresponding spline teeth 86 that are preferably provided on the lateral arm 50 . In this regard, the spline teeth 86 can be provided over a limited extent of the circumferential periphery of the arm 50 , or can be provided around the entire circumferential periphery of the arm. Preferably, the spline teeth 86 extend parallel to the axis 54 over the length of the arm 50 . It will be appreciated that in the second mode, as shown in FIG. 9 , the mating engagement of the spline teeth 84 , 86 serves to react torsional loading about the axis 54 and maintain the rod 22 in its desired position relative to the plate 20 when the system 10 is in use.

In the first mode, the lateral arm 50 is received in the transverse opening 64 and the proximate end of the rod 22 is received in the longitudinal opening 66 , with the clamp plug 70 received in the lock opening 68 at a position between the arm 50 and the rod 22 . The lock 72 is engaged in the lock opening 68 at a position wherein the spline teeth 84 , 86 are disengaged to allow the body 62 to freely rotate and translate about and along the arm 50 and to freely pivot about the axis 69 , and wherein the rod 22 can freely rotate and translate about and along the longitudinal axis 42 in the longitudinal opening 66 .

It will be appreciated from the foregoing that the variable connection 24 allows the relative position of the rod 22 to the plate 20 to be adjusted with respect to five degrees of freedom of motion in the first mode if required to fit patient morphology during a surgical procedure. One degree of freedom of motion is the rotation or pivoting of the body 62 about the arm 50 and transverse axis 54 , which allows adjustment of an angle φ that is formed between the rod 22 and a plane 90 defined by the plate 20 , as best seen in FIG. 2 . In anatomical terms, the angle φ can be said to lie in a sagittal plane, and is critical in positioning the skull 12 relative to the spine 14 and defining the curvature of the spine 14 . Depending on patient morphology, the angle φ will most often be between 100° and 150°, but can be any angle required to provide the desired or natural curvature of the spine 14 . Another degree of freedom of motion is the translation of the body 62 along the lateral arm 50 and transverse axis 54 , shown by arrows A in the Figs., which allows for the lateral position of the rod 22 to be adjusted relative to the spine 14 to fit patient morphology. Pivoting of the body 62 about the axis 69 provides another degree of freedom of motion and allows for adjustment of an angle Ψ formed between the rod 22 and the arm 50 and axis 54 . Another degree of freedom is the translation of the rod 22 in the longitudinal opening 66 along the longitudinal axis 42 relative to the body 62 , which allow for adjustment of the longitudinal position of the rod 22 relative to the plate 20 and the spine 14 . Finally, rotation of the rod 22 about the axis 42 provides yet another degree of freedom of motion and allows for adjustment of an angle α that can be critical if the rod 22 had been deformed along its length to better conform to patient morphology or if the rod 22 requires a particular angle α so as to more easily mate with a corresponding anchoring system for the rod 22 to the spine 14 . It should be appreciated that with the system 10 in the first mode, all of the foregoing adjustments can be made during a surgical procedure with the system 10 positioned in its desired location relative to the skull 12 and spine 14 , thereby allowing a surgeon to more easily adjust the system 10 to the patient morphology.

After the desired relative position of the rod 22 to the plate 20 has been selected by the surgeon in order to provide the desired positioning of the spine and skull (i.e., after the system 10 has been fitted to the patient), the variable connection 24 is placed in the second mode by further engaging the lock 72 in the lock opening 68 so as to clamp the lateral arm 50 against the clamp plug 70 (with the spline teeth 84 , 86 engaged), the clamping plug 70 against the rod 22 , and the rod 22 against the inner surface of the longitudinal opening 66 , thereby locking the rod 22 and the plate 20 in the desired relative position, as best seen in FIG. 8 .

While all of the above adjustments can be important, it is believed that the ability to adjust the angle φ in the first mode and then to lock the angle φ in the second mode so as to resist the torsion placed on the system 10 in use provides a unique advantage over current known fixation systems. Furthermore, it is also believed that the ability to adjust the relative position of the rod 22 to the plate 20 with respect to at least four degrees of freedom in the first mode provides another unique advantage over current known fixation systems.

The system 10 according to the invention may be used in minimally invasive surgery (MIS) procedures or in non-MIS procedures, as desired, and as persons of ordinary skill in the art who have the benefit of the description of the invention understand. MIS procedures seek to reduce cutting, bleeding, and tissue damage or disturbance associated with implanting a spinal implant in a patient's body. Exemplary procedures may use a percutaneous technique for implanting longitudinal rods and coupling elements. Examples of MIS procedures and related apparatus are provided in U.S. patent application Ser. No. 10/698,049, filed Oct. 30, 2003, U.S. patent application Ser. No. 10/698,010, filed Oct. 30, 2003, and U.S. patent application Ser. No. 10/697,793, filed Oct. 30, 2003, incorporated herein by reference.

The system 10 according to the invention is suitable for use with MIS procedures because the locks 72 are tightened or fastened from above. In such an MIS procedure, the surgeon may percutaneously position and place the system 10 using the same technique and through the same wound exposure as with other spinal implants, then tighten or fasten the locks 72 . Because locks 72 can be accessible through the wound, one may couple the components 20 , 22 and 24 together by tightening the locks 72 , as described above in detail, without using additional incisions or wounds.

It should be appreciated that there are many possible variations for the components of the system 10 . For example, with reference to FIG. 9 , two alternate embodiments are shown for the variable connection 24 . Specifically, the variable connection 24 A shown on the left in FIG. 9 is similar to the variable connection 24 shown in FIGS. 3-8 , but differs in that its lateral arm 50 A is provided with a square spline, as opposed to having a plurality of spline teeth. Furthermore, the longitudinal opening 66 A of the connector 52 A is offset laterally with respect to the axis 69 A of the lock opening 68 A, and is a so-called “open” type construction wherein the structure of the body 62 A has a hook-shaped configuration that only partially encircles the longitudinal opening 66 A. The details of the connector 52 A are more thoroughly described in co-pending U.S. patent application Ser. No. 11/234,706, filed on Nov. 23, 2005 and naming Robert J. Jones and Charles R. Forton as inventors (the contents of this application are incorporated fully herein by reference). The variable connection 24 B shown on the right-hand side of FIG. 9 also utilizes a lateral arm 50 B having a square spline, and has a connector 52 B that differs significantly from the connectors 52 and 52 A. More specifically, the longitudinal opening 66 B in the connector 52 B extends along an axis 42 B that intersects the transverse axis 54 B, rather than being offset as in the connectors 52 and 52 A. Furthermore, the connector 52 B has no clamp plug 70 , but rather utilizes a second locking opening 100 and a second lock 102 that engages in the lock opening 100 to clamp the rod 22 in the longitudinal opening 66 B in the second mode. Also, the lock 72 B engages in the lock opening 64 B to clamp the arm 52 B directly in the lateral opening 64 B. While the variable connector 24 B requires manipulation of the additional lock 102 so as to place the connection 24 B in the second mode, it can provide a more compact construction in the anterior-posterior direction in comparison to the variable connections 24 and 24 B because of the alignment of the axis 42 B with the axis 54 B. It will be appreciated that the square splines for the arms 50 A and 50 B shown in FIG. 9 will significantly limit the adjustment with respect to the angle φ. However, it should be appreciated that the lateral arms 52 of FIGS. 3-6 utilizing the multiple spline teeth could be utilized with the connectors 52 A and 52 B. Furthermore, it should be appreciated that other types of splines and anti-rotation type connections can be utilized with the variable connections 24 , 24 A, 24 B.

As another example, although the connectors 52 are shown so that the longitudinal opening 66 is positioned on the anterior side of the lateral arm 50 , it is possible to modify the connector 52 so that the longitudinal opening 66 is located on the posterior side of the lateral arm 50 . In this regard, it would still be desirable for the lock 72 to be accessible from the posterior side.

As yet another example, FIGS. 10 and 11 show yet another alternate embodiment for the system 10 that differs from the other embodiments in that the body 62 C of the variable connection 24 C has been integrated with the rod 22 C. In this regard, because the rod 22 C and body 62 C are an integrated component, there is no longer a need for the body 62 C to have a longitudinal opening 66 , nor is there a need for a clamp plug 70 or any other component to connect the rod 22 C to the body 62 C. In view of this, the body 62 C has only the transverse opening 64 C, the lock opening 68 C, and the lock 72 C, with the spline teeth 84 C being formed on the body 62 C within the transverse opening 64 C. While this simplifies the construction of the variable connection 24 in comparison to the previously discussed variable connections 24 , 24 A and 24 B, it also eliminates the ability to adjust the longitudinal position of the rod 22 C relative to the plate 20 and spine 14 , as well as the rotational position of the rod 22 C about the longitudinal axis 42 C.

Persons skilled in the art may make various changes in the shape, size, number, and/or arrangement of parts without departing from the scope of the invention as described herein. In this regard, it should also be appreciated that the various relative dimensions of each of the components 20 , 22 and 24 are shown in the figures for purposes of illustration only and may be changed as required to render the system 10 suitable for its intended purpose. For example, the length of the lateral arms 52 may desirably be shorter or longer depending upon how much adjustment of the rods 22 in the lateral direction is desired. As a further example, the length of each of the connecting legs of the horseshoe construction of the plate 20 extending to the lateral arms 52 can be shorter or longer as dictated by patient morphology.

Various other modifications and alternative embodiments of the invention in addition to those described herein will be apparent to persons of ordinary skill in the art who have the benefit of the description of the invention. Accordingly, the description, including the appended drawings, is to be construed as illustrative only, with the understanding that preferred embodiments are shown.