Growth directed vertebral fixation system with distractible connector(s) and apical control

Growth directed correction of a spine via apical vertebral control includes securing a correction system to a first vertebra and a second vertebra of the spine, the correction system defining a correction axis extending between the first and second vertebra and securing the correction system to a third vertebra intermediate the first and second vertebra, the correction system securing the third vertebra at a fixed distance from the correction axis. The correction system is secured to the first and second vertebra such that the first and second vertebra are able to grow away from one another in a direction substantially parallel to the correction axis.

BACKGROUND

Early onset scoliosis and scoliosis in the growing spine poses a great challenge in their treatment. In progressive cases, the spine cannot usually be controlled by bracing or even casting and it will grow accentuating the deformity with all its known consequences. On the other hand, correction, fixation, and fusion of the spine will prevent further growth of the fused spine with serious effects on the development of the cardiovascular and pulmonary system, physical appearance, and psychological impacts.

Early onset scoliosis has more recently been treated surgically either by serial distractions or growth directed mechanisms. Serial distractions using “growing rod” systems have been more reliable and have achieved a more predictable outcome. These “growing rod” systems use tandem or domino connectors designed to allow periodic distractions (e.g., every few months) via surgical approach under anesthesia. Growth directed mechanisms have been used in “Luque Trolley” techniques applying segmental wires attached to the vertebrae and rods longer than the instrumented segment to allow for directed growth of the spine by forcing the spine to follow the rods. Some recent trials have used pedicle screws instead of wires—again allowing the heads of the screws attached to the vertebrae to slide along the longer rods with growth.

Both the “growing rod” and the “growth directed” mechanisms, in current systems, are far from being fully satisfactory in the treatment of early onset scoliosis. For example, the “growing rods” have to be distracted surgically every few months for many years with all the disadvantages of multiple surgeries and anesthetic administration in the pediatric age group. In addition to the problems arising from skin and soft tissue opening, the frequent force applied to distract these systems can cause implant failures in addition to the potential negative effects of forceful spinal cord distractions.

The “growth directed” and Luque Trolley type of segmental instrumentations do not require frequent distractions. These systems, however, have not been satisfactory, mainly due to their inability to control rotation, the loss of correction, and spontaneous fusion, which have led to their failure. Even after trials to replace the wires with pedicle screws, there are still many potential problems, including auto fusion after segmental exposure to insert the pedicle screws and a high possibility of jamming between the screw rod junctions preventing smooth gliding of the screws on the rod. Another problem includes the increased risk, time consumption, and radiation exposure needed to insert the large number of multilevel pedicle screws in this very young age group. Furthermore, in these systems, the amount of growth possible before another surgery is limited to the parts of the rod left protruding from the top and bottom screws.

SUMMARY

The present invention, according to some embodiments, relates to a system designed to avoid the disadvantages of the prior art and to make the best use of the power of the growth of the spine by controlling and redirecting spinal growth as well as deforming forces of the spine to allow for longitudinal growth and to correct the residual deformity. Attaching vertebral fixation points proximal and distal to the deformed area of the spine, while strongly fixing the apex of the curve, allows this system to have the maximum control of the curve, while allowing all the vertebrae included in the curve above and below the apex to grow freely. This growth is permitted and directed by one or more connectors which are inserted between these fixation points by sliding of the rods attached to the fixation points within the connectors. Apical control should be strong and reliable to counteract the main deforming forces at the apex, thereby preventing its rotation and angulation. In some embodiments, the main correction of the curve occurs at the time of insertion of the system. Then, with time and growth, the system will allow for longitudinal growth of the spine with additional correction of the curve. As the distance between the rod and the apex of the deformity is fixed, any increase in the distance between the proximal and distal fixation points of the system will lead to a proportional decrease in the scoliosis angle.

Some embodiments address a vertebral fixation system to be used in spinal deformities in the growing spine for the pediatric and adolescent age groups. In some embodiments, the system corrects the scoliosis and allows spinal growth without frequent surgeries or complex technology by directing and controlling the forces that otherwise cause the spine to deform while growing. The system is inserted, or implanted, and includes proximal, distal, and apical vertebral fixation with the use of distractible connectors between the proximal and apical vertebrae and the distal and apical vertebrae.

After insertion, the connectors, or connector assembly, of the system permit the rod, which is fixed to the vertebrae at both ends of the curve, to slide inside one or more cylindrical members to allow for spinal growth. Meanwhile, apical vertebral fixation to the system prevents the spine from rotation or angulation, thereby preventing further deformity and even inducing more correction with time. In some embodiments, the growth directed corrective process will continue until the rod(s)/connector(s) sliding limit is exhausted (e.g., after many years).

As previously indicated, this description of the drawings is not meant to be limiting in nature.

DETAILED DESCRIPTION

FIG. 1is a schematic view of a system10for growth directed correction of a spine12via control of one or more apical vertebrae. The system10is secured to a spine12along a concave aspect of its defective curvature. In some embodiments, the system10includes a hosting connector assembly16including a first connector18, a second connector20, and a middle assembling segment22. In the various embodiments, the system10further includes a first rod24, a second rod26, and an intermediate connector assembly28.FIG. 2shows the first connector18and portions of the first rod24and the middle assembling segment22.

The first and second rods24,26are adapted to extend along the spine12and optionally differ in length as shown inFIG. 1, although in other embodiments the first and second rods are substantially similar in length. In some embodiments, rod length is selected to allow a desired degree of growth of the spine12. The rods24,26each optionally include an enlarged stop feature30,32having a larger diameter than adjacent portions of the respective rods24,26. In some embodiments, the stop features30,32of the rods24,26are thicker, shorter portions (e.g., with smooth rounded outline) which are hosted by wider areas of the connectors18,20and are allowed to slide within the respective connectors18,20until they abut narrower parts of the connectors. Each of the rods24,26also includes thinner longer portions36,38.

As shown schematically inFIG. 1, the spine12generally includes five portions, where a defective segment of the spine12includes a proximal, or upper portion40; a distal, or lower portion42; and an apical portion, or apex44. Above and below the defective segment40,42,44, the spine12has a first portion46including one or more stabilizing vertebrae (e.g., a first vertebra46A) and a second portion48including one or more stabilizing vertebrae (e.g., a second vertebra48A). In some embodiments, the stabilizing vertebrae are substantially aligned and are optionally fused during, prior to, or after assembly of the system10. In turn, the apical portion44includes one or more vertebrae at the apex of the defect (e.g., a third vertebra44A, a fourth vertebra44B, and a fifth vertebra44C).

The thinner portions36,38of the rods24,26are adapted to host means of spinal fixation34,35, such as pedicle screws or hooks, to the first and second portions46,48of spine12at both ends of the defective segment40,42,44. For example, in some embodiments, the means of spinal fixation34,35include pedicle screws or hooks used to secure the thinner longer portions36,38of the rods24,26to one or more vertebrae in each of the first and second portions46,48, respectively, of the spine12. If desired, each of the thinner longer portions36,38is secured to the first and second vertebrae46A,48A, respectively, of the first and second portions46,48. In some embodiments, one or both of the thinner longer portions36,38are secured to multiple vertebrae, such as two adjacent stabilizing vertebrae of the first and second portions46,48, respectively (e.g., to provide additional support to the system10).

In some embodiments, the middle assembling segment22includes a body portion22A, such as a rod, a plate, or other structure for spanning between the first and second connectors18,20and to which a vertebra (e.g., a third vertebra44A in the apical portion44) can be tensioned. The middle assembling segment22also optionally includes an interconnect portion22B, such as a collar or a head of a pedicle screw, for connecting to the body portion22A.

In some embodiments, the intermediate connector assembly28includes one or more elongate members, such as first elongate member28A, second elongate member28B, and third elongate member28C. The elongate members28A,28B,28C optionally include one or more cables, wires, pedicle screws, hooks, rods, and/or other means for spanning between the interconnect portion22B of the middle assembling segment22and the apical portion44. The elongate members28A,28B,28C are optionally connected to the third, fourth, and fifth vertebrae44A,44B,44C of the apical portion44, respectively, by fastening means49, such as threaded fasteners, adhesives, hooks, sublaminar wires, and/or others.

The first and second connectors18,20optionally differ in length as shown inFIG. 1, although in other embodiments the connectors18,20are substantially similar in length. The first and second connectors18,20are adapted to extend along a desired spinal segment (e.g., including the upper and lower portions40,42). In some embodiments, the lengths of the first and second connectors18,20are selected to allow a desired amount of longitudinal growth of the spine12, where the connectors18,20are each optionally cylindrical, having inner bores50,52that have narrowed, neck portions54,56and wider portions58,60such that the inner bores50,52include two parts with different diameters.

In some embodiments, the diameters of the wider portions58,60of the bores50,52are larger than the diameters of the thicker, stop features30,32of the rods24,26to allow introduction of the rods24,26into the bores50,52, starting with the thinner portions36,38of the rods24,26which are first introduced through the openings into which the body portion22A of the middle assembling segment22is subsequently inserted and secured. The stop features30,32of the rods24,26help retain the rods24,26in the inner bores50,52by engaging the narrowed or necked portions54,56of the connectors18,20and help prevent inadvertent ejection of the rods24,26from the connectors18,20.

In some embodiments, each of the connectors18,20includes two means of fixation (e.g., set screws, pins, or others) for selectively locking a longitudinal position of the rods24,26with respect to the first and second connectors18,20, respectively. As used herein, “selectively locking” indicates that the longitudinal position is locked and unlocked as desired using the means of fixation of the first and second connectors18,20. According to some embodiments, independent control of each of the upper and lower portions40,42of the deformity is achieved by preselecting a desired amount that each of the first and second rods24,26is allowed to travel in the respective first and second connectors18,20(e.g., by selecting a length of the connectors18,20and rods24,26) and/or by selectively locking the rods24,26using the means of fixation once a desired amount of growth is achieved.

FIG. 2shows a first means of fixation70and a second means of fixation72of the first connector18, where according to some embodiments the second connector20includes similar means of fixation that operate similarly to the first and second means of fixation70,72(seeFIGS. 4 and 5). In the embodiment shown inFIG. 2, the first and second means of fixation70,72are located at each end of the connector18. The second means of fixation72(e.g., a set screw) is optionally used to fix the connector18to the middle assembling segment22, the middle assembling segment22being received in the central bore50of the connector18. The first means of fixation70is a temporary fixation point to fix the connector18to the thinner portion36of the rod24as desired. The means for fixation of the second connector20optionally operate similarly and, by fixing the rods24,26to the connectors18,20, the rods24,26, and connectors18,20can be handled as one piece for ease of use during their insertion in the index surgery. Following insertion, the first means of fixation70of the first connector18and the first means of fixation (not shown) of the second connector20are released (e.g., unscrewed and/or removed) at the end of the procedure to disengage the connectors18,20from the rods24,26to allow for gradual sliding of the rods24,26within the connectors18,20with growth of the spine12.

The diameters of the narrower, or thinner portions36,38of the rods24,26allow the thinner portions36,38of the rods24,26to go through the bores50,52, while the thicker stop features30,32prevent the rods24,26from ejecting from the bores50,52and limit sliding of the rods24,26to a desired range. In other words, the rods24,26will slide in the connectors18,20with the thicker parts of the rods24,26moving out into the wider parts58,60of the bores50,52of the connectors18,20until they abut against the narrower, necked portions54,56of the bores50,52, preventing the rods24,26from further sliding. At this point, the length of the rods24,26and more generally the system10will be exhausted and the system10will likely need to be adjusted by exchanging the rods24,26and/or connectors18,20to longer sizes.

In some embodiments, the body portion22A of the middle assembling segment22is introduced into, and fixed to both wider ends of the bores50,52of the connectors18,20. Upon assembly and fixation to the first and second vertebrae46A,48A, the rods24,26, connectors18,20, and middle assembling segment22define a correction axis X extending between the first and second vertebrae46A,48A. The body portion22A of the middle assembling segment22is assembled to the interconnect portion22B which hosts the intermediate connector assembly28. As described above, the intermediate connector assembly28optionally includes elongate members28A,28B,28C that include one or more of cables, wires, pedicle screws, hooks, or other means for spanning between the middle assembling segment22and the intermediate connector assembly28. The distance between the middle assembling segment22and the apical portion44can be decreased by shortening the length of this fixation tool to tension or draw the apical portion44(e.g., the third vertebra44A) toward the correction axis X.

Some methods of assembly includes coupling the first and second rods24,26with the first and second connectors18,20, and then coupling the first and second connectors18,20together with the middle assembling segment22. When assembled, the thinner portions36,38of both rods24,26extend out of the narrower openings or necked portions54,56of the corresponding connectors18,20. The thinner portions36,38may then be attached to the spine12proximal and distal to the spinal deformity via vertebral fixation implants (e.g., hooks, screws, or others) at the first and second vertebrae46A,48A. The bigger end of both rods24,26(stop features30,32) will each be hosted inside the respective bores50,52of one of the connectors18,20near the wider portions58,60of the bores50,52and beside the middle assembling segment22to allow the rods24,26to slide inside the bores50,52during growth of the spine12. Both wider portions58,60of the bores50,52of the connectors18,20receive the body portion22A of the middle assembling segment22which is then secured within the body portion22A. The elongate member(s)28A,28B,28C of the intermediate connector28are secured to the interconnect portion22B of the middle assembling segment22and the elongate member(s)28A,28B,28C are secured to the third, fourth, and fifth vertebrae44A,44B,44C using the fastening means49to thereby fix and control the apical portion44with respect to the middle assembling segment22.

Some methods of growth directed correction of the curvature with the system10proceeds as follows. The system10is applied and secured to the first portion46(e.g., first vertebra46A), the second portion48(e.g., second vertebra48A), and apical potion44(e.g., one or more of the third, fourth, and fifth vertebrae44A,44B,44C), for example, after maximum correction has been achieved by surgery. Then, with growth, both bulkier ends or stop features30,32of the rods24,26will slide outwardly, away from the body portion22A within the first and second connectors18,20allowing for directed growth of the spine until the rods24,26are exhausted and the bulkier parts, or stop features30,32abut against the necked portions54,56of the connectors18,20and/or until the rods24,26are locked at a desired position via the fixation means (e.g., set screws) of the first and second connectors18,20. This interaction allows for spontaneous growth (e.g., several centimeters) and many years of growth while keeping the distance between the middle assembling segment22and the apical portion44. In some embodiments, the distance between the middle assembling segment22and the apical portion44is reduced using a specific instrument, such as a cable or wire tensioner (not shown).

A schematic representation of a method of growth directed correction is provided inFIGS. 3-5, whereFIG. 3shows the spine12having a scoliotic curve (e.g., a severe curve greater than about 90 degrees) prior to application of the system10.FIG. 4shows the spine12and the system10after application of the system10. As shown inFIG. 4, and according to some embodiments, the system10is secured to the spine12with some amount of apical correction during fixation (e.g., to a curve of about 59 degrees). In some embodiments, partial correction is accomplished by drawing the apical portion44toward the system10as part of the apical fixation process.FIG. 5shows the system10and spine12following spinal growth (e.g., a few years later) where the spine12and the system10have elongated causing growth directed correction of the spine12resulting gradually and spontaneously without further intervention (e.g., to a curve of about 19 degrees). In some embodiments, however, further intervention following some growth is contemplated to encourage and/or augment correction. For example, such intervention optionally includes reducing the distance between the system10and the apical portion44by tensioning and/or shortening one or more of associated elongate member(s)28(a single elongate member28A is shown inFIGS. 4 and 5).

Various features and advantages of embodiments of the system10should be apparent from the foregoing. For example, in some embodiments, the system10is easy to fabricate, is low profile such that it is suitable for all ages, and efficient and effective in use. The system10is optionally assembled as a single construct via the temporary means of fixation between the rods24,26and connectors18,20, promoting ease of insertion and securement to the spine. Once implanted, the system10is optionally designed to work over the course of multiple years without substantial intervention.

In view of the foregoing, various embodiments provide a vertebral system10for correction and controlled growth of the spine12compromising rod(s)24,26, a hosting connector assembly16, and an intermediate connector assembly28. Embodiments include rods24,26with different diameters of its both ends, where the bigger ends of the rods24,26are optionally smooth to allow sliding in first and second connectors18,20having end openings of different diameters. The connectors18,20optionally have a wider openings to allow introduction of the rods24,26starting with their thinner then thicker parts inside the connectors18,20. The wider opening can accommodate and be fixed to a middle assembling segment22of the system10via any stable means of fixation (e.g., set screws, threads, or others). In some embodiments, the system10includes a middle assembling segment22that includes a rod or plate which is attached to the intermediate connector assembly28, which is in turn secured to the apical portion44via vertebral fixation means (e.g., hooks, screws, wires, or other fastening means). The connectors18,20provide temporary fixation (e.g., using set screws, pins, or others) to the rods24,26during assembly and insertion of the system10. The system10is optionally to correct spinal deformities by allowing for growth of the spine12and promoting further gradual correction of the deformity with growth.

In some embodiments, the system10is used for acute and gradual correction of spinal deformity which allows for spinal growth of the instrumented segment by elongating automatically with growth without the need for any intervention after insertion and connection to the spine12. The system10includes a hosting connector assembly or assemblies16, special rod(s)24,26and intermediate connector(s)28. The rods24,26are allowed to slide inside the hosting connector assembly16, in turn allowing for elongation of the whole system10and hence the instrumented part of the spine12. A middle assembling segment22is fixed to the apex44of the deformity using an intermediate connector assembly28including one or more elongate members28A,28B,28C secured to the apex44using fastener means (e.g., pedicle screws, hooks, wires, cables, adhesives, and/or other means) to help prevent progressive rotation, angulation, or other deformity progression.

The distance between the two ends of the system10are able to independently increase with time and growth, while the distance between the apex44of the deformity and the system10is fixed or can be shortened by mean of continuous tension of the apical fixation (e.g., by tensioning the elongate member(s)28A,28B,28C) thereby allowing for gradual spinal deformity curve correction with growth. For example, in some embodiments, first and second connector(s)18,20each have a cavity made of two parts with different diameters and lengths—a longer wider part and shorter narrower one. The connector(s)18,20each have one opening at each end, each opening has a different diameter which corresponds to its adjacent cavity. In some embodiments, each rod24,26has a thicker (bigger diameter) shorter part at the end of the rod24,26with the aim of preventing the rod24,26from dislodging from the smaller end opening of the corresponding connector18,20when the system10reaches its maximal length. Each wider cavity of the connector(s)18,20can host and allow the passage of both parts of the rod(s)24,26while the narrower cavity of the connector(s)18,20can host only the thinner part of the rod(s)24,26, thereby preventing the thicker end of the rod(s)24,26from passing through the corresponding end opening of the connector(s)18,20.

In some embodiments, the middle assembling segment22connects the two hosting connectors18,20together by being inserted into and secured within the wider openings and cavities of the connectors18,20. The rod(s)24,26are introduced—their thinner parts first—into the wider openings of the connectors18,20and are fixed temporarily therein. The body portion22A of the middle assembling segment22is then inserted into the wider ends and fixed therein to interconnect the two connectors18,20together. In some embodiments, the body portion22A of the middle assembling segment22is a rod shaped, or contoured to conform with a desired shape of the spine12in order to promote a proper sagittal contour of the spine12and decrease an incidence of implant failure, for example. The middle assembling segment22is secured to the apical portion44by the intermediate connector28, which includes fastening means such as pedicle screws, hooks, wires, cables, and/or other fastening means for fastening to the vertebrae at the apex44of the deformity. The connector(s)18,20have means of fixation (e.g., set screw, pins, and/or others) proximate each end—at the wider end to fix the connectors18,20to the middle assembling segment22and at the narrower end to fix the thinner part of the rods24,26temporarily during assembly and insertion and attachment of the system10to the spine12. In some embodiments, the temporary means of fixation, or selective locking means, are removed at the end of the procedure to allow one or both of the rods24,26to slide in the connectors18,20and to allow the system10to elongate.

As referenced above, the system10optionally facilitates independent, separate control of each of the upper and lower portions40,42of a deformity, those upper and lower portions40,42being situated proximal and distal to an apical portion44of the deformity. For example, a distance between each end of the system10and the apical portion44increases independently with time and growth of the spine12, while the distance between the apical portion44and the system10is generally fixed or selectively adjusted (e.g., by tensioning the apical portion44toward the hosting connector assembly16) allowing for gradual or gross spinal deformity curve correction. The first and second connectors18,20optionally have different lengths, (e.g., to facilitate differing, independent, and preplanned control of the permissible growth and correction of the upper and lower portions40,42of the spine12). In some methods of differing, independent, and preplanned control, a deformity angle and number of vertebrae included in each of the upper and lower portions40,42are taken into consideration in determining an appropriate amount of travel between the first rod24and the first connector18and between the second rod26and the second connector20, where each of the first and second rods24,26is able to slide independently of the other rod inside its corresponding connector to facilitate independent elongation of the system10along the instrumented portions of the spine12above and below the apical portion44. In some methods of correction, the second mean of fixation of each of the first and second connectors18,20can, at any time after the application of the system10, be tightened to limit further elongation of the corresponding upper or lower portion40,42of the spine12. By including means for selectively limiting growth of the upper or lower portions40,42of the spine12, the system10is further adapted to promote independent correction of each of the upper and lower portions40,42as desired.

Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, a second system (not shown) substantially similar to the system10is optionally secured on an opposite side of the spine12for additional control. Moreover, while the system10is shown secured on a concave lateral aspect of the spine12, it should be understood that, in some embodiments, the system10is secured on a convex lateral aspect of the spine12.

FIG. 6shows another system110for growth directed correction of a spine112(schematically represented by a single line) via control of one or more apical vertebrae. As shown, the system110includes a cascaded, or laterally offset feature, as subsequently described. As indicated schematically inFIG. 6, in some embodiments the system110is secured to the spine112along a concave aspect of its defective curvature. In some embodiments, the system110includes a hosting connector assembly116including a first connector118, a second connector120, and a middle assembling segment122. In the various embodiments, the system110further includes a first rod124, a second rod126, and an intermediate connector128.

The first and second rods124,126are adapted to extend along the spine112and optionally differ in length as shown inFIG. 6, although in other embodiments the first and second rods124,126are substantially similar in length. Regardless, in some embodiments, rod length is selected to allow a desired degree of growth of the spine112.

As indicated, the spine112generally includes five portions, where a defective segment of the spine112includes a proximal, or upper portion140; a distal, or lower portion142; and an apical portion, or apex144. Above and below the defective segment140,142,144, the spine112has a first portion146including one or more stabilizing vertebrae and a second portion148including one or more stabilizing vertebrae. In some embodiments, the stabilizing vertebrae are substantially aligned and are optionally fused during, prior to, or after assembly of the system110. In turn, the apical portion144includes one or more vertebrae at the apex of the defect.

In some embodiments, the rods124,126are adapted to host means of spinal fixation134,135for securing the first and second portions146,148of spine112at both ends of the defective segment140,142,144. In some embodiments, the means of spinal fixation134,135include pedicle screws, hooks, adhesive, or other fastening means used to secure the rods124,126to one or more vertebrae in each of the first and second portions146,148.

In some embodiments, the middle assembling segment122includes a body portion122A, such as a rod, a plate, or other structure for spanning between the first and second connectors118,120and to which one or more vertebrae in the apical portion144is tensioned. The middle assembling segment122also optionally includes an interconnect portion122B, such as a collar or a head of a pedicle screw or hook, for connecting to the body portion122A.

In some embodiments, the intermediate connector128includes one or more elongate members, such as a first elongate member128A. The elongate member(s) optionally include one or more cables, wires, pedicle screws, rods, and/or other means for spanning between the middle assembling segment122and the apical portion144.

In some embodiments, the first and second connectors118,120are substantially shorter than the connectors18,20of the system10. For example, the first and second connectors118,120are optionally about 10 mm in length (i.e., a direction substantially parallel to the longitudinal axes of the respective rods124,126) or less. The first connector118is adapted to slidably receive the first rod124and the middle assembling segment122. The second connector120is adapted to slidably receive the second rod126and the middle assembling segment122. The connectors118,120are optionally substantially similar and thus are described with reference to the first connector118, whereFIGS. 8 and 9are top and front views, respectively, of the first connector118.

As shown inFIGS. 8 and 9, the first connector118has a dual-ring shape, having a first ring portion150and a second ring potion152, the second ring portion152being interconnected with the first ring portion150. The first and second ring portions150,152are optionally alternatively secured together by a rod or other connector. Indeed, although the two portions150,152are shown as a single piece, in other embodiments the two portions150,152are separate, connected components.

The ring portions150,152include central bores150A,152A for receiving the first rod124and the middle assembling segment122, respectively. As shown, the central bores150A,152A have entries and exits that are rounded to facilitate rod sliding and/or to avoid binding, for example. As shown, the central bores150A,152A are substantially circular and smooth. In other embodiments, the central bores150A,152A include a prominence, or chase feature (such as chase feature138shown inFIGS. 12 and 13) for inhibiting longitudinal rotation of the rod124and/or the body portion122A in the central bores150A,152A. For example, in some embodiments, the rod124and/or body portion122A include a complementary chase feature (such as chase139shown inFIG. 14) to the prominence so that the rod124and/or body portion122A and the bores150A,152A interlock, stopping longitudinal rotation of the rod124and/or body portion122A. In other embodiments, the rod124and body portion122A and the bores150A,152A have complementary, non-circular cross-sections (square, octagonal, or D-shaped, for example) that mate to inhibit rotation of the rod124and body portion122A in the bores150A,152A, respectively.

As shown inFIG. 6, each of the connectors118,120includes two means of fixation (e.g., set screws, pins, or others)118A,118B and120A,120B, respectively, for selectively locking a longitudinal position of the connectors118,120relative to the rods124,126and the middle assembling segment122. As shown inFIGS. 8 and 9, the means of fixation118A,118B are set screws secured into the two portions150,152, respectively, such that adjustment of the first means of fixation118A selectively locks the first rod124in the first ring portion150and adjustment of the second means of fixation118B selectively locks the middle assembling segment122in the second ring portion152. For reference, in the schematic views ofFIGS. 6 and 7, an open hexagon is indicative that the means of fixation is in an unlocked configuration and a solid hexagon is indicative that the means of fixation is in a locked configuration.

In some embodiments, the system110includes stop features130,132that help prevent the rods from sliding toward one another, which could otherwise lead to reduction in the length of the system110in the longitudinal direction and loss of correction of the scoliosis angle. For example, the stop features130,132optionally help limit the rods124,126to sliding in a single direction—the direction of growth—and help prevent sliding in an opposite direction that would otherwise reduce overall system length. In some embodiments, the stop features130,132are rings, or collars, that include set screws130A,132A for securing the stop features130,132longitudinally along the first and second rods124,126, respectively.

In some embodiments, the system110also includes stop features136,137that help prevent inadvertent ejection of the rods124,126from the connectors118,120. For example, the stop features136,137help ensure that the system110does not inadvertently disassemble after sufficient growth is achieved to cause the connectors to reach the ends of the rods124,126and/or under sufficient flexing of the spine112.

Generally, the stop features130,132,136,137are substantially similar to the first and second connectors118,120, but rather than first and second ring portions, only a single ring portion is present, according to some embodiments.FIGS. 10 and 11show the stop feature130from top and front views, respectively, the stop features132,136,137being substantially similar to the stop feature130according to some embodiments.

As shown inFIG. 6, each of the stop features130,132,136,137includes a means of fixation (e.g., set screws, pins, or others)130A,132A,136A,137A, respectively, for selectively locking a longitudinal position of the stop features relative to the rods124,126. The means of fixation130A,132A,136A,137A are set screws secured into the stop features130,132,136,137, respectively. For example, as shown inFIGS. 10 and 11, adjustment of the means of fixation130A selectively locks the first rod124in the stop feature130. For reference, in the schematic views ofFIGS. 6 and 7, an open hexagon is indicative that the means of fixation is in an unlocked configuration and a solid hexagon is indicative that the means of fixation is in a locked configuration.

As shown inFIGS. 10 and 11, the stop feature130has a single-ring shape, although multi-ring shapes are contemplated. The stop feature130includes a central bore130B for receiving the first rod124. As shown, the central bore130B has an entry and an exit that are rounded to facilitate rod sliding and/or to avoid binding, for example. As shown, the central bore130B is substantially circular and smooth, although non-rotational features are contemplated as described below.

For example,FIGS. 12 and 13show the stop feature130according to some other embodiments, whereFIG. 12is a cross-sectional view along line12-12inFIG. 13. As shown, the central bore130B includes a prominence, or chase feature138for inhibiting longitudinal rotation of the rod124in the central bore130B. The chase feature138is optionally a hemi-spherical bump or protrusion into the bore130B. As shown inFIG. 14, in some embodiments, the rod124includes a chase feature139, such as a longitudinal groove or chase, that is complementary to the chase feature138such that that the rod124and the bore130B are adapted to interlock, helping prevent longitudinal rotation of the rod124in the bore130B. In other embodiments, the rod124and the bore130B have complementary, non-circular cross-sections (square, octagonal, or D-shaped, for example) that mate to inhibit rotation of the rod124in the bore130B. Although the chase features138,139are shown on the stop feature130and rod124, respectively, it should be understood that the chase features138,139are optionally reversed, with the chase feature139on the stop feature130and the chase feature138on the rod124.

Regardless, according to some embodiments, independent control of each of the upper and lower portions140,142of the deformity is achieved by preselecting a desired amount that each of the first and second rods124,126is allowed to travel in the respective first and second connectors118,120. In some embodiments, the amount of travel is determined by selectively locking the stop features130,132,136,137longitudinally along the first and second rods124,126at a desired position to set limits of travel for the first and second rods124,126, respectively.

Some methods of assembling the system110include coupling the first and second rods124,126with the first and second connectors118,120, and then coupling the first and second connectors118,120to the middle assembling segment122. When assembled, the rods124,126extend out of the corresponding connectors118,120, with respective portions of the rods124,126being secured to the spine112proximal and distal to the spinal deformity via vertebral fixation implants (e.g., hooks, screws, or others) at the first and second portions146,148of the spine112. The first rod124and the second rod126are hosted, or received, inside the bores of the respective connectors118,120and are allowed to slide inside the bores of the corresponding connectors118,120during growth of the spine112.

Adjacent bores of the connectors118,120receive the middle assembling segment122and are selectively locked to the body portion122A to provide system stability. In the configuration shown inFIG. 6, the middle assembling segment defines a second axis of correction Y that is laterally offset, toward the spine112, relative to a first axis of correction X defined by the longitudinal axes of the rods124,126, the two rods124,126being coaxially aligned to one another according to some embodiments. In some embodiments, this offset brings the middle assembling segment122closer to the spine112reducing the length needed for the intermediate connector128. The intermediate connector128is then secured to the apex144using fastening means such as those previously described (e.g., similar to fastening means49). The respective stop features130,132,136,137are received over the first and second rods124,126and are selectively locked thereto in order to help prevent the rods124,126from sliding toward one another (e.g., to avoid losing an amount of correction already achieved with the system110) as well as help prevent the rods124,126from sliding out of the connectors118,120(e.g., after sufficient spinal growth and/or during flexing of the spine112). In some embodiments, an additional set of stop features (not shown) are secured inwardly along the rods (e.g., toward the apical portion144of the spine112) to set limits on the allowed longitudinal expansion of the system110.

Some methods of growth directed correction of the curvature with the system110proceeds as follows. The system110is applied and secured to the first portion146, the second portion148, and the apical portion144, for example, after maximum correction has been achieved via surgery. Then, with growth, both of the rods124,126will slide outwardly, away from one another and adjacent to the body portion122A. During growth, the rods124,126will continue to slide within the first and second connectors118,120, allowing for growth-directed correction of the spine112until the rods124,126are exhausted and/or until the rods124,126are locked at a desired position via the fixation means of the first and second connectors118,120. This interaction allows for spontaneous growth and/or movement (e.g., several centimeters) and many years of growth while maintaining a constant distance between the middle assembling segment122and the apical portion144. In some other embodiments, the distance between the middle assembling segment122and the apical portion144is periodically reduced during growth using a specific instrument, such as a cable or wire tensioner (not shown).

The system110, and in particular the relatively short connectors, help facilitate placement of the system110in relatively compact areas of the spine112(e.g., in scoliotic curved regions which provide little area for longer, more bulky connectors). For example, a dorsal curve or an asymmetric curve regularly exhibits a relatively small distance between the stabilizing vertebrae and the apex in which a connector of about 50 mm in length may not fit. The dual-ring connector is deployable in a very short segment of the spine112while allowing for considerable length of rod bending and sliding and, thus, growth directed correction. Moreover, in some embodiments, the stop features130,132are optionally used to direct the force in a single, expanding direction by preventing compression and shortening of the system110without interfering with elongation thereof.

FIG. 7is a schematic of another system210for growth directed correction of a spine212(schematically indicated by a single line) via control of one or more apical vertebrae. In some embodiments the system210is secured to the spine212along a concave aspect of its defective curvature. In some embodiments, the system210includes a hosting connector assembly216including a first connector218, a second connector220, and a middle assembling segment222. In the various embodiments, the system210further includes a first rod224, a second rod226, and an intermediate connector228.

The first and second rods224,226are adapted to extend along the spine212and optionally differ in length as shown inFIG. 7, although in other embodiments the first and second rods224,226are substantially similar in length. Regardless, in some embodiments, rod length is selected to allow a desired degree of growth of the spine212.

As indicated, the spine212generally includes five portions, where a defective segment of the spine212includes a proximal, or upper portion240; a distal, or lower portion242; and an apical portion, or apex244. Above and below the defective segment240,242,244, the spine212has a first portion246including one or more stabilizing vertebrae and a second portion248including one or more stabilizing vertebrae. In some embodiments, the stabilizing vertebrae are substantially aligned and are optionally fused during, prior to, or after assembly of the system210. In turn, the apical portion244includes one or more vertebrae at the apex of the defect.

In some embodiments, the rods224,226are adapted to host means of spinal fixation234,235for securing the first and second portions246,248of spine212at both ends of the defective segments240,242. In some embodiments, the means of spinal fixation234,235include pedicle screws or hooks used to secure the rods224,226to one or more vertebrae in each of the first and second portions246,248.

In some embodiments, the middle assembling segment222includes a body portion222A, such as a rod, a plate, or other structure for spanning between the first and second connectors218,220and to which one or more vertebrae in the apical portion244is tensioned. The middle assembling segment222also optionally includes an interconnect portion222B, such as a collar or a head of a pedicle screw or hook, for connecting to the body portion222A.

In some embodiments, the intermediate connector228includes one or more elongate members, such as a first elongate member228A. The elongate member(s) optionally include one or more cables, wires, pedicle screws, hooks, rods, and/or other means for spanning between the middle assembling segment222and the apical portion244.

In some embodiments, the first and second connectors218,220are substantially similar to the first connector118shown inFIGS. 8 and 9, the first and second connectors218,220being substantially shorter than the connectors18,20of the system10. In particular, the first connector218is adapted to slidably receive the first rod224and the middle assembling segment222and the second connector220is adapted to slidably receive the second rod226and the middle assembling segment222, each of the first and second connectors218,220including first and second ring portions250,252and254,256, respectively.

The ring portions250,252include central bores for receiving the first rod224and the middle assembling segment222, respectively, and the ring portions254,256include central portions for receiving the second rod226and the middle assembling segment222, respectively. As shown inFIG. 7, each of the connectors218,220includes two means of fixation (e.g., set screws, pins, or others)218A,218B and220A,220B, respectively, for selectively locking a longitudinal position of the connectors218,220relative to the rods224,226and the middle assembling segment222. The means of fixation218A,218B are optionally set screws secured into the ring portions250,252and254,256, respectively. Activation of the first means of fixation218A selectively locks the first rod224in the first ring portion250and activation of the second means of fixation218B selectively locks the middle assembling segment222in the second ring portion252. Activation of the first means of fixation220A selectively locks the second rod226in the first ring portion254and activation of the second means of fixation220B selectively locks the middle assembling segment222in the second ring portion256. For reference, in the schematic views ofFIGS. 6 and 7, an open hexagon is indicative that the means of fixation is in an unlocked configuration and a solid hexagon is indicative that the means of fixation is in a locked configuration.

In some embodiments, the system210includes stop features230,233that help retain the middle assembling segment222in the first and second connector assemblies218,220by preventing inadvertent ejection of the middle assembling segment222from the connectors218,220(e.g., after sufficient spinal growth and/or during flexing of the spine212). The system210also includes stop features231,232that help ensure that an achieved amount of correction of the spine212is not lost (e.g., due to compressive forces on the patient's spine—such as during standing). In some embodiments, the stop features230,231,232,233are rings, or collars, that include set screws230A,231A,232A,233A for securing the stop features230,231,232,233longitudinally along the middle assembling segment222. In some embodiments, stop features231,232help prevent collapse, or shortening of the system (e.g., under compressive forces of body weight) while stop features230,233help prevent ejection of the middle assembling segment222from the connector assemblies218,220once a length of the middle assembling segment222has been exhausted from spinal growth.

Generally, the stop features230,231,232,233are substantially similar to the first and second connectors218,220, but rather than first and second ring portions, only a single ring portion is present, according to some embodiments. Regardless, according to some embodiments, independent control of each of the upper and lower portions240,242of the deformity is achieved by preselecting a desired amount that the system210expands, or an amount that each of the first and second rods224,226is allowed to travel along the middle assembling segment222, by selectively locking the stop features230,231,232,233longitudinally at desired positions to set limits of travel for the first and second rods224,226, respectively. For example, as shown inFIG. 7, the stop features230,231are locked on the middle assembling segment222on opposite sides of the first connector218and the stop features232,233are locked on the middle assembling segment222on opposite sides of the second connector220, to limit the travel of first and second connectors relative to the middle assembling segment222.

Some methods of assembling the system210include coupling the first and second rods224,226with the first and second connectors218,220, and then coupling the first and second connectors218,220to the middle assembling segment222. When assembled, the rods224,226extend out of the corresponding connectors218,220, with respective portions of the rods224,226being secured to the spine212proximal and distal to the spinal deformity via vertebral fixation implants (e.g., hooks, screws, or others) at the first and second portions246,248of the spine212. A first end224A of the first rod224and a first end226A of the second rod226are hosted inside the bores of the respective connectors218,220and are selectively locked inside the bores of the corresponding connectors218,220during growth of the spine212.

Adjacent bores of the connectors218,220slidably receive the middle assembling segment222(although the connectors218,220are optionally locked to the middle assembling segment222during implantation to provide a rigid construct that is more readily handled, or to provide system stability). In the configuration shown inFIG. 7, the middle assembling segment222defines a second axis of correction Y that is laterally offset, toward the spine212, relative to a first axis of correction X defined by the longitudinal axes of the rods224,226, the two rods224,226being coaxially aligned to one another according to some embodiments. In some embodiments, this offset brings the middle assembling segment222closer to the spine212reducing the length needed for the intermediate connector228. The intermediate connector228is then secured to the apex244using fastening means such as those previously described (e.g., similar to fastening means49).

The respective stop features230,231,232,233are received over the intermediate connector228and are selectively locked thereto in order to set limits between which the first and connectors218,220slide on the middle assembling segment.

Some methods of growth directed correction of the curvature with the system210proceeds as follows. The system210is applied and secured to the first portion246, the second portion248, and the apical portion244, for example, after maximum correction has been achieved via surgery. Then, with growth, both of the rods224,226will slide outwardly, away from one another and adjacent to the body portion222A. During growth, the rods224,226, and in particular the first and second connectors218,220, will continue to slide along the middle assembling segment222, allowing for growth-directed correction of the spine212until the limit of travel is exhausted and/or until the rods224,226are locked at a desired position via the fixation means of the first and second connectors218,220. This interaction allows for spontaneous growth and/or movement (e.g., several centimeters) and many years of growth while maintaining a constant distance between the middle assembling segment222and the apical portion244. In some other embodiments, the distance between the middle assembling segment222and the apical portion244is periodically reduced during growth using a specific instrument, such as a cable or wire tensioner (not shown).

The system210, and in particular the relatively short connectors, help facilitate placement of the system210in relatively compact areas of the spine212(e.g., in scoliotic curved regions which provide little area for longer, more bulky connectors). For example, a dorsal curve or an asymmetric curve regularly exhibits a relatively small distance between the stabilizing vertebrae and the apex in which a connector of about 50 mm in length may not fit. The dual-ring connector is deployable in a very short segment of the spine212while allowing for considerable length of rod bending and sliding and, thus, growth directed correction. Moreover, in some embodiments, the stop features230,232are optionally used to direct the force in a single, expanding direction by preventing compression and shortening of the system210without interfering with elongation thereof.

Various features and advantages of embodiments of the systems10,110,210should be apparent from the foregoing. For example, in some embodiments, such systems are easy to fabricate, are low profile to be suitable for all ages, and efficient and effective in use. The systems are optionally assembled and implanted as a single construct via the various means of fixation, with subsequent unlocking of the system to permit the desired expansion, promoting both ease of insertion and ready securement to the spine. Once implanted, the systems are designed to work over the course of multiple years without substantial intervention.

The range of indication of embodiments of the systems is wide enough to include any type of early onset spinal deformity of any etiology from the very young ages to the adolescent growth spurt, for example. One exemplary indication is early onset scoliosis where the systems are used in young children to allow for growth of the spine, trunk, chest, and lungs while preventing progression of the scoliotic curve and even correcting the curve spontaneously with growth. The systems can also be used in small and moderate sized curves during the adolescent period before severe progression as a kind of internal bracing to help prevent further progression of these defective curves until a child's growth spurt finishes. In some embodiments, once the growth spurt has ended, the systems are removed, leaving a non-fused, relatively flexible, corrected spine.