FIELD

The present disclosure relates to spinal alignment, and more particularly to a segmented alignment rod assembly for performing a gradual three-dimensional alignment of a spine which has deviated from a normal attitude for pathologic reasons.

BACKGROUND

Scoliosis is a disorder that causes an abnormal curve of the spine, or backbone. Patients with scoliosis develop abnormal curves to either side of the body's median line (lateral curve) and the bones of the spine twist on each other like a corkscrew.

The Greek physician Hippocrates coined the term scoliosis and devised various forms of external braces and benches to support or stretch the abnormally curved spine. Since animals can also suffer from scoliosis, there is little doubt it is an anomaly that has been around since the dawn of vertebrates. It is estimated that about 3% of humans are afflicted, meaning over 200 million people worldwide are living with this anomaly.

Females are much more likely to suffer from scoliosis than males and for idiopathic scoliosis the ratio is 10:1. It can be seen at any age, but it is most common in those over ten years old. Present knowledge suggests a genetically predisposed growth asymmetry at the level of the vertebral body endplates as a potential underlying cause.

Minor degrees of scoliosis are treated with bracing or stretching of the spine, not that dissimilar to the prescriptions and descriptions dating back to the time of Hippocrates. While the materials and techniques have changed, the principals have evolved very little.

Severe degrees of scoliosis are largely treated by a major operation known as segmental instrumented spinal fusion, a lengthy procedure where the muscles are flayed from the spinal bone and metal rods are then implanted to straighten the spine and hold it in position until grafted bone products fuse the spinal vertebrae together into a solid tower of bone. Since the normal spine is segmented to permit functional motion, fusion in and of itself sets the stage for life long corollary problems directly related to the administered cure which precludes normal movement, and at times, even normal growth.

Because of the magnitude of the surgery, complications include death, paralysis, infection, and hardware failure. Late complications include stiffness, chronic back pain, late hardware failure, and breakdown of adjacent normal segments because of stress provided by the long fused spinal segment. This list of complications is illustrative and not exhaustive.

Since major scoliosis surgery is such a cataclysmic event, it is often employed as a last resort, meaning that simple curves are followed until major curves develop thereby increasing not only the magnitude of the surgery, but the potential risk of complications as well.

Present scoliosis treatment is rather eclectic, employing everything from techniques of bracing, essentially outlined in the time of Hippocrates, to the major robotic surgeries of present day. As with anything in medicine, whenever multiple solutions exist for a particular disease process, it generally means that no single solution is sufficiently effective.

FIG. 1is a stylized posterior view of a person P with a spine afflicted with scoliosis. Spinal column1is shown to have two lateral curves—upper curve2and lower curve3. Often the presence of one lateral curve generates the formation of a second curve to compensate for the reduced spinal support of the body caused by one lateral curve.FIGS. 2 and 3depict two different types of prior art braces4and5, respectively, used to prevent further deterioration of spinal alignment. In some cases, braces such as braces4and5may improve the condition, but they rarely enable the wearer to achieve a full recovery to a correct spinal alignment.

Clearly, there is a need in the art to have a treatment that is simple and safe enough to employ such that spinal curvatures can be treated early in the pathologic process so that progression to major curvature can be avoided along with the attendant major interventional surgery required when the curves are extreme.

There is also a need in the art to diminish or eradicate the requirement for fusing the spine such that normal motion can be maintained, and the deleterious consequence of a spinal fusion avoided.

SUMMARY

According to aspects illustrated herein, there is provided a segmented rod assembly for aligning a spine including a plurality of vertebrae, comprising a rod, including a plurality of segments, the plurality of segments having at least a first segment arranged to be connected to a first vertebra of the spine, the first segment including a first body and at least one tang extending from the first body, and a second segment arranged to be connected to a second vertebra of the spine, the second segment including a second body and at least one channel arranged in the second body, wherein the at least tang is operatively arranged to engage the at least one channel, and at least one tensioning member arranged within the plurality of segments, the at least one tensioning member having a first end secured to the first segment and a second end.

According to aspects illustrated herein, there is provided a segmented rod assembly for aligning a spine including a plurality of vertebrae, comprising a rod, including a plurality of segments, the plurality of segments having at least a first segment arranged to be connected to a first vertebra of the spine, a second segment arranged to be connected to a second vertebra of the spine, and a third segment arranged to be connected to a third vertebra of the spine, a first tensioning member arranged at least partially within the first segment and the second segment, and a second tensioning member arranged at least partially within the second segment and the third segment.

According to aspects illustrated herein, there is provided a segmented rod assembly for aligning a spine including a plurality of vertebrae, comprising a rod, including a plurality of segments, wherein a first segment of the plurality of segments includes a protruding tang, a second segment of the plurality of segments includes an outward facing channel, the protruding tang is operatively arranged to engage the outward facing channel to rigidly connect the first and second segments, and at least one segment of the plurality of segments is connected to a first vertebra of the spine, and at least one tensioning member arranged at least partially within the plurality of segments, wherein the at least one tensioning member is operatively arranged to force the plurality of segments into engagement.

According to aspects illustrated herein, there is provided a segmented rod assembly for aligning a spine having a plurality of vertebrae, comprising a rod, including a plurality of segments, the plurality of segments having at least a first segment arranged to be slidingly secured to a first vertebra of the spine, a second segment arranged to be fixedly secured to a second vertebra of the spine, and a third segment arranged between the first and second segments to be connected to a third vertebra of the spine, a tensioning member arranged within the plurality of segments, the tensioning member having a first end secured to the first segment and a second end.

According to aspect illustrated herein, there is provided a segmented rod assembly for aligning a spine having a plurality of vertebrae, comprising a first clamp arranged to be secured to a first vertebra of the spine, a second clamp arranged to be secured to a second vertebra of the spine, a third clamp arranged to be secured to a third vertebra of the spine, the third vertebra located between the first vertebra and the second vertebra, a rod, including a plurality of segments, the plurality of segments having at least a first segment slidingly engaged with the first clamp a second segment fixedly secured to the second clamp, and a third segment connected to the third clamp, and a line arranged within the plurality of segments, the line having a first end secured to the first segment and a second end, and a winding mechanism arranged proximate the second segment and connected to the second end.

A segmented rod assembly for aligning a spine having a plurality of vertebrae, comprising a first clamp arranged to be secured to a first vertebra of the spine, a second clamp arranged to be secured to a second vertebra of the spine, a third clamp arranged to be secured to a third vertebra of the spine, the third vertebra located between the first vertebra and the second vertebra, a rod, including a plurality of segments, the plurality of segments having at least a first segment slidingly engaged with the first clamp, a second segment fixedly secured to the second clamp, and a third segment connected to the third clamp, and a flexible shaft arranged within the plurality of segments, the flexible shaft having a first end secured to the first segment and a second end connected to the second segment, wherein when the flexible shaft is rotated in a first circumferential direction the plurality of segments are drawn toward each other to engage.

The present disclosure broadly comprises an assembly for performing a gradual three-dimensional alignment of a spine which has deviated from a normal attitude for pathologic reasons. The assembly includes a hollow segmented rod, having segments which, when drawn together, form a contoured rod whose reconfigured shape approximates an ideal or non-pathologic spinal configuration. A cable, or cables, is housed within the hollow segments that comprise the rod. In an example embodiment, a flexible shaft assembly is housed within the hollow segments that comprise the rod. The cable, cables, and flexible shaft is designed to draw the hollow segments together such that when the segments are intimately mated, they form a rigid rod that approximates an ideal spinal alignment. The cables or flexible shaft can be drawn taut by a turnbuckle at either or both ends. The cable or turnbuckle/flexible shaft assembly, in turn, are connected to a ratcheting worm drive assembly operated by a mechanically depressible subcutaneous paddle such that gradual spinal alignment can occur as the turnbuckle shortens the intersegmental distance between rod segments and rigid rod alignment is reestablished.

The present disclosure broadly comprises an assembly for performing gradual lateral alignment of a spine, gradual sagittal alignment of a spine, or a combination of the two, as well as correcting the rotation that invariably accompanies these deviations in severe combinations of the above malalignments. In essence, correction of three-dimensional malalignment.

The assembly comprises a hollow rod which is pre-contoured to approximate the normal S-shaped configuration of the human spine. The length of the rod and the approximate curves needed to correct the pathologic alignment of a patient is obtained using Surgimap® simulation software or similar software that provides computerized renderings of individual patient pathologies known in the art and presently utilized to form custom contoured patient-specific spinal rods for scoliosis surgery. Alternatively, a mathematical average for a specific spine length can be chosen and a statistical ideal curvature for the spine selected.

Once the ideal patient-specific rod is formed, it is cut into segments, with each segment being roughly the length of a vertebral body segment. In sections where little curvature is anticipated, a rod segment may span two or more vertebral segments. The preformed hollow rod is cut into segments such that each segment can deviate from the other in regard to their original axial alignment, when separated, but bond intimately in a male/female fashion when drawn together by a cable(s) or flexible shaft.

In an alternative embodiment, the adjacent segments are hinged together at a specific point at or near the circumference of the perimeter of the rod, such that the original curvilinear shape of the rod is approximated once the segments are drawn tautly together by an integrated connecting cable.

The hollow rod, once segmented, can be passed along the external surface of the spine and assume any of a myriad of pathologic configurations. The segmented rod is then affixed to the spine at the proximal and distal ends, and at the apex of the curvature, should complex rotatory curves be encountered. Individual segments are maintained in close juxtaposition by an interconnecting cable, which permits limited polyaxial movement of the segments. These segments are like beads on a string, render the construct flexible, but stiffen the construct when the string is drawn taut and the beads are pulled into close apposition. By varying the shape of the contact surfaces between the bead elements, different longitudinal shapes can be formed when the string is tautened.

The fixation of the rod to the spine will be through traditional methods known in the art such as hooks, clamps, screw, or combinations thereof. The preferred embodiment utilized a spinous process clamp which clamps two or more adjacent spinous processes. In an example embodiment, the spinous process clamp clamps only one spinous process. In the case of pedicle screws and the like, expansion screws are preferred and will be described infra.

Once the segmented rod is drawn subfacially along the pathologic spine and its curves, ideally along the spinous process/lamina junction, and affixed to the spine at two or more strategic locations, the segments are gradually drawn together to assume their original pre-segmented attitude, including the built-in contours necessary to restore perfect spinal alignment. By tensioning the cable over time, gradual spinal alignment can be achieved thereby mitigating traction injury to the spinal cord.

Drawing the segments of the rod together is accomplished in one of two ways. In highly flexible spines where forces are less likely to be extreme, the hinge and cable iteration would be chosen because it would utilize a thinner rod approximating a 5-6 mm diameter. Hinging of the segments would occur along the ventral portion of the rod where sagittal curve correction would be required and laterally where lateral curve correction is anticipated. While a round rod could be used, the hinged version may utilize an oval, or square cross-sectional shape to allow a greater surface area to employ a hinge linkage. In this version, the tautening cable would be located along the perimeter opposite the hinge, insofar as possible, to maximize the mechanical advantage. In stiffer spines, a larger 8-10 mm diameter segmented rod with a single large internal cable capable of withstanding greater force could be employed.

Once the cable rod is positioned along the spine, the hinged connection allows intimate contact of a particular rod segment with a corresponding vertebral element. The cranial and caudal segments are intimately secured via clamp, hook, or pedicle screw fixation, while the apex segment may be fixated via clamp, hook, pedicle screw, or also a cable to allow better relative movement between the alignment assembly and the spine while restoration of the spine to a normal attitude occurs. The rod segment assembly would be enclosed in a flexible sheath of biocompatible material to prevent tissue ingress or growth between rod segments, e.g., polyethylene.

Tautening of the cables occurs in the caudal segment, which houses a turnbuckle attached to the cable. A subcutaneous ratcheting worm drive mechanism is implanted in, on, or adjacent to the caudal segment and connected to a turnbuckle assembly such that when a subcutaneous paddle is digitally compressed transcutaneously through intact skin, the turnbuckle draws the cable taut thereby pulling the segments together and restoring ideal rod configuration. Since the spine is affixed to the rod, spinal movement mirrors rod movement until rigid configuration of the rod is restored. While one rod should be sufficient to restore alignment, a second rod could be employed to provide greater support of the scoliotic spine during straightening. Certain segments could connect in a ball and socket configuration to allow for limited movement of the spine thereby permitting some normal movement.

In another embodiment, a cable is replaced with a flexible rotary shaft capable of imparting both tensile and rotary forces. This shaft lies in roughly the center of the segments of the rod and is connected to a turnbuckle located at each end. Initially, the caudal turnbuckle is rotated, tensioning the system, and once it reaches maximal tensioning, it begins to rotate the flexible shaft which turns a second turnbuckle located at the cranial end. By employing two turnbuckles, even greater cable shortening and rod tensioning can occur.

To implant the segmented contoured cable rod assembly for gradual spinal alignment, the anesthetized patient is positioned prone on the operating table. After appropriate prepping and draping, fluoroscopy is used to identify the spinal curve apex as well as the cranial and caudal transition to normality. Each position is marked and a small incision is made to expose two spinous processes at each of the three indicated levels. To these exposed spinous processes, a special clamp is affixed serving to attach the segmented cable assembly to the spine. To pass the segmented cable rod assembly from one clamp to the other in subfacial location, a catheter passer is employed. Once the catheter passer is slid subfacially from one incision to another, a cable is slid through the hollow plastic sheath when the malleable trochar is removed. The wire is placed from one incision to the next entering the caudal incision, passing through the apex incision and emanating from the cranial incision. Alternatively, the cable can be passed from the cranial incision to the caudal incision, if desired. The catheter passer is removed leaving the cable behind.

Once the cable is positioned subfacially in a preferred location, the segmented cable rod assembly is attached to one end of the cable and pulled beneath the fascia along the contours of the spinal curvature. The cable rod assembly is then affixed to the spinous process clamps located at the cranial, caudal, and apex incisions.

In the preferred embodiment, the segmented cable rod assembly is securely affixed to the caudal clamp so that no relative motion, apart from segment apposition, can occur. To the caudal end of the caudal clamp, a ratcheting turnbuckle assembly is affixed and is used to draw the cable taut when a subcutaneous paddle is depressed.

In the apex incision, the segmented cable rod is affixed to the clamp such that it can slide relative to the clamp in an axial or longitudinal plane, but is restricted circumferentially by a collar. As the segmented cable rod assembly gradually straightens, it brings the spinous process clamp and spine along with it toward its new attitude. Since the rod can slide unrestricted, and has a sloppy fit, unrestricted spinal growth can occur along with some limited spinal movement. These features buffer the extremes of forces that cause failure in present day fixed scoliosis instrumented constructs, and permits a modicum of normal spinal movement for the child that rigid bracing or fusion deny.

At the superior end, the final segment of the cable rod construct affixes to the cranial clamp via a distal protuberance that engages the clamp in a piston/rod configuration. This association, similar to the collar fixation at the apex, allows for limited lateral/medial and dorsal/ventral movement while permitting linear axial movement as the child grows or whenever the child bends. The length of this slideable component is 5-7 cm to permit normal spinal growth elongation without having to lengthen the rod.

Once the assembly is affixed to the spine via the clamps the incisions are closed and allowed to heal.

Gradual spinal alignment is carried out by depressing a subcutaneous paddle beneath the skin at the level of the caudal clamp. This paddle activates a ratcheting worm drive turnbuckle assembly which tautens the cable, thereby drawing the segments of the rod closer together. As the segments approximate gradually, relative motion is restricted until a solid contoured rod assembly is formed, whereupon tightening is ceased. The rigid rod then serves to maintain normal contoured spinal alignment until mature spinal growth has been achieved. At this point, the cable is loosened and the patient is observed to ensure the mature spine does not lapse into misalignment. If it does not, the device assembly is removed, leaving a normal functioning spine. If deviation does occur, the cable assembly is retightened and fusion of the apex is carried out.

It is clear that the ratcheting worm drive mechanical activator of the present disclosure could be replaced with a magnetic, ultrasonic, or piezoelectric motor if desired. The manually operated activator is preferred in this invention so as to decrease the costs associated with this form of instrumented surgery.

Should pedicle screws be required or desired as a means of anchoring the assembly to the spine, a pedicle screw with an expansile shaft is preferred. The shaft is expanded once the screw is placed to increase surface area and mitigate “toggling” or “windshield wipering” of the shaft in softer cancellous bone when axial or perpendicular forces are applied to the shaft.

In some embodiments, the present disclosure uses motors (e.g., servo motors) similar to those used in robotics. For example, motors can be placed at various strategic locations along the segmented rod assembly to tighten various sections of the rod at different times. The motors may be triggered by slackness in its respective tensioning member or cable. Thus, a sensor detecting slackness in a tensioning member would trigger the motor connected thereto to activate and tighten the tensioning member. The motor may turn a threaded screw connected to the tensioning member to tighten the section of the rod.

In some embodiments, a servo motor may be arranged in each segment (i.e., every two segments is connected by a tensioning member). In some embodiments, the segmented rod assembly is separated into strategic sections according to the normal S-curve of a spine (e.g., based on vertebral height, the extent of the curvature of the deviated portion of the pathologic spine, etc.) and servo motors are assigned to each of those sections. Thus, tensioning members are arranged in series, rather than one long cable biased at the end of the segmented rod, which allows for better control of the corrective spinal alignment process. Springs could also be used instead of or in addition to the motors to bias the tensioning members of the segmented rod assembly.

The motors may be activated/controlled by sensing slackness in the tensioning members or may be controlled wirelessly via a wireless control and transducers. In some embodiments, muscle wire or bio metal is used for the tensioning members in order to tighten the sections of the segmented rod assembly.

These and other objects, features, and advantages of the present disclosure will become readily apparent upon a review of the following detailed description of the disclosure, in view of the drawings and appended claims.

