Abstract:
The present invention generally relates to methods and device for treatment of spinal deformity, wherein at least one tether is utilized to maintain the distance between the spine and the an ilium to (1) prevent increase in abnormal spinal curvature, (2) slow progression of abnormal curvature, and/or (3) impose at least one corrective displacement and/or rotation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application is a continuation-in-part of U.S. application Ser. No. 14/039,660, filed Sep. 27, 2013, which claims priority to U.S. Provisional Application Ser. No. 61/744,525 filed on Sep. 28, 2012, the contents of which are hereby incorporated by reference in their entireties for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to methods and devices for treatment of spinal deformity. 
       BACKGROUND OF THE INVENTION 
       [0003]    Scoliosis is a spinal deformity characterized by an abnormal curvature of the spine in the coronal plane. Adolescent idiopathic scoliosis (AIS) is the most prevalent type of scoliosis which develops during adolescence in an otherwise healthy patient and typically ceases at the onset of skeletal maturity. The cause of the disease is presently unknown. 
         [0004]    Current surgical treatment of scoliosis involves manipulation of the spinal column and attachment of corrective devices for fusion of a portion of the spine. One such system, the Cotel-Dubousset system utilizes rigid metal rods attached to the spine. The rods are manipulated during surgery in an attempt to reduce abnormal curvatures and rotations of the spinal column. Large loads are exerted on the spine for correction which risks the patient&#39;s neurological condition. Recovery from these procedures can be lengthy and painful. Also, if normal lordosis and kyphosis are not restored, a condition called “flat back syndrome” may occur causing chronic pain. Even a successful procedure rarely results in a normal spinal curvature and the patient is left with an immobile spinal section. The discs above and below the fusion zone are at risk of future degeneration due to the increased mechanical demands placed on them. 
         [0005]    It is therefore evident that there are flaws in prior art methods and devices. Most prior art devices are part of the load path of the spinal column. For example, it is understood that the Cotel-Dubgousset system rigidly attaches stiff metal rods to the spine. A structure having two roughly parallel support members relies primarily on the stiffer of the two members for transmission of loads. Therefore, loads exerted on an instrumented spine are transferred through the implant instead of through the spine. Spinal loads can be significantly large, and the implants will not support such loads indefinitely. Fatigue failure of the implant will occur if fusion is delayed. 
         [0006]    Therefore, there is an unaddressed need that exists to provide a new and better system for correcting spinal deformities. 
       SUMMARY OF THE INVENTION 
       [0007]    The current invention describes methods and devices for treating spinal deformity which offer significant improvements over prior art methods and devices. In general terms the present invention is used to secure the distance between an ilium and the spine to either correct or maintain spinal curvature. There are many embodiments of the invention which will achieve the stated objectives, some of which will be presented in the following summary. 
         [0008]    In one embodiment of the invention, at least one device is attached between the spine and the pelvis which incorporates at least one flexible tether. Attachment of the flexible tether to the spine and ilium involves implantation of anchoring means and then attachment of the tether to the anchoring means. For example, at least one bone screw, pedicle screw, cannulated bone screw, clamp, plate, bone anchor, or shackle might be anchored to at least one vertebra and another to a portion of the ilium and the flexible tether may be attached to both. Other means of attachment will be clear to one practiced in the art. Alternatively, a loop of material may be placed around a bony structure (e.g. spinous process, transverse process, lamina or pars) or a hole through a bony structure through which the flexible tether is passed. 
         [0009]    It should be noted that the present invention enables manipulating the vertebral column to correct the deformity by securing the tether to a portion of the ilium and a portion of the vertebral column; the ability to correct deformity by correcting the effective length of the tether between the ilium and vertebra over time; and correcting deformity by the natural growth of the spine by allowing the tether to maintain effective length between the vertebral column and the ilium. 
         [0010]    Adjustment of the distance between the spine and ilium is achieved by varying the location at which the tether is attached to the anchoring means. The tether does not change lengths during the adjustment process, but the distance between the attachment points does, much like adjusting a belt around your waist. Taking advantage of the inherent viscoelasticity of spinal structures, the curvature may be gradually corrected by small incremental corrections over a protracted period of time, whereby the original incision is re-opened, or a new incision next to the original incision is created and the attachment means is disengage and then reengaged at a different location along the tether. Alternatively the patient&#39;s growth may be used to achieve correction. 
         [0011]    Alternatively, the tether may branch into multiple tethers to provide multiple attachments to the spine and/or ilium. If more than one tether is used, each can be attached to a different vertebra, or multiple tethers can be attached to the same vertebra. Tethers can be attached to either or both sides of the vertebral column and either opposing sides of ilium as needed to generate correction of the spinal deformity. A crossing pattern whereby a tether is attached to the right side of the vertebra (e.g. the right pedicle) and left ilia, or vice versa, is possible. Also, a tether may be attached to a vertebra and then passed through an eye screw or other guiding device which is attached to the ilium (or both ilia) and then attached to a second vertebra with a pedicle screw or other means. In can be envisioned by one skilled in the art that guiding devices may be utilized on a number of vertebrae or one the ilium or ilia. The tether may also originate with an attachment to the pelvis, pass through any number of guide members attached to the spine, and then terminate at the pelvis again. 
         [0012]    According to another embodiment, a spinal system for correcting a deformity in the spine includes a tether, an anchor, an elongate rod and two bone fasteners, a clamp, and a fastener. The clamp is securable to the elongate rod. The clamp includes a clamp body and a hasp body hingedly connected to the clamp body. The clamp body has a first opening extending through the clamp body, and the hasp body has a second opening extending through the hasp body. When the clamp is closed, the first and second openings are aligned with one another, and the fastener is configured to be received through the first and second openings to securely lock the tether within the clamp. The hasp body may include a hinge sleeve portion having an opening extending therethrough, and a pivot pin received in the opening and connected to the clamp body to allow for pivotal movement of the hasp body relative to the clamp body. The tether may be temporarily secured to the clamp body, before the clamp is closed, by first and second elongate slots extending through the clamp body, which are configured to receive the tether. Alternatively, the clamp body may include an elongate pin member with opposing ends configured to be received in the clamp body so that the tether wraps around the elongate pin to temporarily secure the tether in the clamp. 
         [0013]    These and other aspects of the present invention will become apparent from the following description of the embodiments taken in conjunction with the following drawings, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure. 
         [0014]    The present invention provides an improved method of arresting a spinal deformity whereby at least one device is surgically attached between the spine and the ilium. Also, the present invention provides a system and a method for correcting a spinal deformity whereby at least one device is surgically attached between the spine and the ilium. One method of adjusting the curvature of the spine without fusion may include, for example, installing an anchor into a portion of the ilium; installing two bone fasteners into the pedicles of a vertebra and connecting an elongate rod between the two bone fasteners; attaching a first end of a tether to the anchor; attaching a second end of the tether to a clamp, the clamp having a clamp body and a hasp body hingedly connected to the clamp body, the clamp body having a first opening extending through the clamp body, and the hasp body having a second opening extending through the hasp body; closing the clamp such that the first and second openings are aligned with one another; inserting a fastener through the first and second openings to securely lock the tether within the clamp; and connecting the clamp to the elongate rod. Another method of adjusting the curvature of the spine without fusion may include axially rotating one or more vertebra to produce a lateral shift in the spine. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0016]      FIG. 1  is an illustration of a posterior view of a deformed human spine with an implanted device according to one embodiment of the present invention; 
           [0017]      FIG. 2  is an illustration of a posterior view of a corrected human spine with the implanted device shown in  FIG. 1 ; 
           [0018]      FIG. 3  shows a spinal anchoring means in the form of two pedicle screws and a rod onto which is secure an attachment mechanism and the tether; 
           [0019]      FIG. 4  illustrates an attachment mechanism and the method of attaching it to the spinal anchoring mechanism; 
           [0020]      FIG. 5  shows the anchoring mechanism of the ilium (not shown) and the method of attaching the tether to it; 
           [0021]      FIG. 6  shows a long pair of forceps to be used for passing the tether beneath the skin; 
           [0022]      FIG. 7  illustrates the use of the forceps of  FIG. 6  in passing the tether beneath the skin; 
           [0023]      FIG. 8  illustrates an alternative embodiment of the tether clamp and elongate rod according to the present invention; 
           [0024]      FIG. 9  illustrates another embodiment of a clamp or anchor according to the present invention; 
           [0025]      FIG. 10  shows a cross-sectional view of the device shown in  FIG. 9 ; 
           [0026]      FIG. 11  shows another embodiment of a clamp or anchor according to the present invention; 
           [0027]      FIGS. 12 and 13  shows a closed head clamp according to the present invention; 
           [0028]      FIGS. 14 and 15  shows yet another embodiment of a closed head clamp according to the present invention; 
           [0029]      FIGS. 16-18  illustrate various methods of coupling the tether to portions of the spine and/or ilium; 
           [0030]      FIGS. 19-21  illustrate an alternative embodiment of a tether clamp; 
           [0031]      FIGS. 22 and 23  provide yet another alternative for a tether clamp; 
           [0032]      FIGS. 24 and 25  depict a posterior view of a deformed human spine and a corrected human spine, respectively, with an implanted device according to one embodiment; 
           [0033]      FIGS. 26 and 27  show a method and device for correcting scoliosis by de-rotating the vertebra in the axial plane; and 
           [0034]      FIG. 28  depicts an alternative version of coupling the tether to the spine by looping the tether around the lamina. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. 
         [0036]      FIG. 1  is an illustration of a posterior view of a deformed spine  104  whereby the preferred embodiment of the device  200  is attached to an ilium  102  and a vertebra  100 . Device  200  includes a tether  204  having a free end  206  and that is configured to be attached to the ilium and a portion of the vertebra. Specifically, in one embodiment, two attachment mechanisms such as pedicle screws  300  are anchored to the vertebra of the spine by insertion into opposing pedicles, and a transverse rod  311  is attached to the pedicle screws  300 . It should be noted that although pedicle screws are provided in this particular embodiment, any other type of anchoring mechanism such as hooks may also be used. A tether clamp  310  is attached to rod  311  and the tether  204  is passed though tether clamp  310  and then passed down to the ilium  102  thereby securing a connection between the attached vertebra and the ilium. To attach the tether  204  to the ilium  102 , an ilium anchor  210  is provided. The ilium anchor  210  includes a bore  211  and is configured to be attached to the ilium by inserting the anchor  210  (threading) into a hole which has been drilled or punched through the ilium  102 . It should be noted that any other similar mechanism to attach anchor  210  to the ilium  102  may also be utilized. Tether  204  is passed through hole or bore  211  in the ilium anchor  210  and then brought back to the vertebra  100  and passed again through the tether clamp  310 . In other embodiments, the tether  204  may only be passed once through the tether clamp and ilium anchor  210 . 
         [0037]      FIG. 2  illustrates the correction of the spine of  FIG. 1  using device  200 . As illustrated in  FIG. 2 , the free end  206  of tether  204  is pulled and the spine is manually manipulated during the surgery to achieve a correction of the deformity. When a satisfactory curve magnitude is achieved, tether  204  is tightened within the tether clamp, effectively locking the distance between vertebra  100  and the ilium  102 . 
         [0038]    It should be noted that various levels of manipulation of the vertebral column can be coordinated using the device. For instance, different curvatures of the spine can be achieved by changing the position of the anchor and the clamp on the tether with respect to the vertebral column and the ilium. The locations along the tether where the clamp and anchor are attached determine an effective length of the tether, which in turn maximizes the distance that the attached vertebra may move relative to the position where the tether is attached at in the ilium. The scoliotic curve is corrected (or maintained) by adjusting the clamping and anchoring locations along the tether. 
         [0039]      FIG. 3  shows a detailed view of pedicle screws  300 , transverse rod  311 , tether clamp  310  and tether  204 . In a preferred embodiment tether clamp  310  includes locking screw  312  which clamps tether clamp  310  onto rod  311  as well as locking the tether  204  within the clamp  310 . 
         [0040]      FIG. 4  shows a detailed view of the tether clamp  310  coupled to the transverse rod. The tether clamp  310  is configured with a slot  501  which is provided through the tether clamp  310  and tether  204  is passed through slot  501 . It should be noted that the tether may be passed through the slot multiple times, if necessary. Locking screw  312  is used to secure the transverse rod  311  onto the tether clamp  310  and applies a compressive force upon the rod  311  onto the tether  204 , thereby clamping the tether  204  securely in place. It should be noted that although a threaded set screw is utilized in the present embodiment, any type of locking element know in the art for securing the tether within tether clamp may be used. 
         [0041]      FIG. 5  shows a detailed view of an ilium anchor  210 . Ilium anchor  210  includes threads  212  for engagement with ilium  102  (not shown). Tether  204  is passed through bore  211  and then passed back to the vertebral column. A collar  215  is shown which keeps tether  204  adjacent to itself. 
         [0042]      FIG. 6  shows an extra-long pair of forceps  900 .  FIG. 7  shows the preferred method of passing the tether through an incision  845  and underneath skin and other soft tissues. The forceps  900  are used to pass the tether though the openings in the tether clamp and used to tension the tether to correct the deformity of the curvature in the spine. 
         [0043]      FIG. 8  illustrates another embodiment of a tether clamp  320  according to the present invention. In this embodiment, the tether clamp  320  is configured with a through hole  322  that is configured to correspond to a through hole  324  in an elongate rod  326  that is fixated to a portion of the spinal column. A fastening element  328  such as a set screw is provided to couple the tether clamp  320  and the elongate rod  326  together. The tether clamp  320  also includes openings  330 ,  332  which are dimensioned to receive and securely couple a tether  334  to the clamp  320 . The tether  334  is pulled through each of the openings  330 ,  332  to securely attach the tether  334  to the clamp  320  and the elongate rod  326 . 
         [0044]      FIGS. 9 and 10  illustrate an alternative embodiment of a clamp and/or anchor  250  that can be used to secure a tether  252  to either the vertebral column or a portion of the ilium. More specifically, the anchor  250  of  FIGS. 9 and 10  may be configured and dimensioned to be attached to a portion of the vertebral column or may be configured be secure the tether to the ilium. The anchor  250  is configured as a plate  251  having at least two openings  254 ,  256  to receive fasteners  258 ,  260  capable of fixating the plate to bone. The plate  251  includes a middle portion  262  having an opening  264  that is capable of receiving the tether  252 . The middle portion  262  of the plate  251  is further provided with a fastening element  266  to secure the tether  252  to the plate  251 . As more clearly illustrated in  FIG. 10 , the fastening element  266  may be a set screw which directly contacts the tether  252  when tightened to secure the tether  252  to the plate  251 . It should be noted that any other type of fastening element which is capable of securing the tether to the anchor may be used, such as a pin. 
         [0045]      FIG. 11  illustrates yet another embodiment of a clamp or anchor  400  according the present invention. In this embodiment, the clamp and/or anchor  400  includes a first plate  402  and second plate  404  that are secured to one another via a fastening element  406 . The first and second plates  402 ,  404  are may also include spikes  408  or similar type of features that bite into bone. Either the first or second plate  402 ,  404  or both also includes an opening  410  for receiving a tether. The first and second plates  402 ,  404  are positioned so that bone is in between, such as the ilium or a portion of the vertebral column. As the first and second plates  402 ,  404  are compressed into bone, the tether which is positioned through the opening  410  and in between the first and second plates  402 ,  404 , is also securely locked between the plates and the bone thereby securing the tether to the plates  402 ,  404 . In an alternative embodiment, the tether is passed through the opening and secured to the anchor  400  by a clamp device such a belt clamp or secured by knotting the tether around the edge of the anchor  400 . It should be noted that any type of mechanical mechanism to attach the tether to the anchor may be used. 
         [0046]      FIGS. 12-15  illustrate yet another embodiment of a clamp according to the present invention. The closed head clamp  420 , as illustrated in  FIGS. 12 and 13 , includes a first opening  422  extending through the clamp  420  in a first direction and a second opening  424  extending in a second direction. The first and second directions are generally perpendicular to one another. The first opening  422  is configured to receive an elongate rod  426  and the second opening  424  is configured to receive a tether  428 . The clamp  420  is further provided with a fastening element  430  that is used to secure both the rod  426  and the tether  428 . In this embodiment,  FIGS. 12 and 13  also illustrates that the second opening  424  is positioned at a bottom portion of the clamp  420 , thus, as the fastening element  430  is tightened, the fastening element  430  contacts the rod  426  which is pushed against the tether  428  thereby securing the tether  428  and rod  426  within the clamp. 
         [0047]    In an alternative embodiment of the closed head clamp as illustrated in  FIGS. 14 and 15 , the closed head clamp  432  includes a first opening  434  and a second opening  436 . The first opening  434  and the second opening  436  are configured to be generally transverse to one another. The first opening  434  is dimensioned to receive an elongate rod  438  and the second opening  436  is dimensioned to receive a tether  440 . The clamp  432  also includes a fastening element  442 , such as a set screw, which when tightened secures and locks the tether  440  and the elongate rod  438  within the clamp  432 . In this particular embodiment, the second opening  436  is positioned between the fastening element  442  and the elongate rod  438 . When the fastening element  442  is tightened, the fastening element  442  directly contacts the tether  440  which contacts the elongate rod  438  thereby securely locking the tether  440  and the elongate rod  438  within the closed head clamp  432 . 
         [0048]      FIGS. 16-18  illustrate alternative embodiments of the inventive device. Specifically,  FIG. 16  illustrates the use of clamp to attach the tether to the lamina of a vertebra. As illustrated, the tether may encircle the lamina and may be tightened using a belt clamp. In an alternative version shown in  FIG. 28 , the tether  204  may be looped around the lamina  106  and a force F applied to the tether  204 . The other end of the tether is as shown in the earlier embodiments coupled to a portion of the ilium. Using this mechanism, the deformity of the spine may be corrected by manipulating the tether as well as the positioning of the clamp, as needed. 
         [0049]      FIG. 17  shows a tether that includes a loop which is used to for coupling the tether to the transverse rod to fixate the tether to the transverse rod.  FIG. 18  illustrates the coupling of the tether directly to the ilium using another type of tether clamp. It should be noted that in the examples provided of both anchor and clamps, these mechanical devices may be interchangeable. 
         [0050]    It should also be noted that the tether of the present invention may be composed of fabric, polymer, such as PET, or any other biocompatible materials. The tether can be a cable and can be dimensioned to be a wide elastic band which advantageously reduce the risk of damage to tissue lacerations or injury. In some embodiments, the tether can be is between 2 and 900 mm. Also, to ensure that proper correction of deformities, a tensioner can be included as part of the system to make sure that the tether is in proper tension and tightness. 
         [0051]      FIGS. 19-21  show an alternative version of a tether clamp  520 . Similar to tether clamp  320 , tether clamp  520  is configured to couple a tether  204  to an elongate rod  326 .  FIG. 19  shows the clamp  520  in an open configuration.  FIG. 20  shows the clamp  520  in a closed configuration with a fastener  528 .  FIG. 21  depicts the clamp  520  attached to an elongate rod  326  with fastener  528 . The tether clamp  520  is in the form of a hinged clamp configured to clamp the tether  204  and connect the tether  204  to the rod  326 . The hinged tether clamp  520  includes a main clamp body  524 , a hasp body  526  hingedly connected to the clamp body  524 , and a fastener  528  (such as a screw) configured to secure the hasp body  526  to the clamp body  524  and the clamp  520  to the elongate rod  326 . The hasp body  526  is able to pivotally move with respect to the clamp body  524  to allow for the open and closed configurations. 
         [0052]    The clamp body  524  may extend from a distal end to a proximal end. The clamp body  524  may include a through hole  522  extending through the clamp body  524 . The through hole  522  may be positioned closer to the distal end of the clamp body  524 . The through hole  522  may by generally spherical in cross-section and sized and dimensioned to receive at least a portion of the fastener  528 . The inner surface of the through hole  522  may be non-threaded or threaded. Preferably, the inner surface of the through hole  522  is threaded to mate with corresponding threads on the fastener  528 . 
         [0053]    The clamp body  524  further includes a first elongate opening  530  extending through the clamp body  524  and a second elongate opening  532  extending through the clamp body  524 . The second elongate opening  532  may be positioned closer to the proximal end of the clamp body  524 , and the first elongate opening  530  may be positioned between the through hole  522  and the second elongate opening  532 . The first elongate opening  530  may be separate and distinct from the through hole  522 , as shown in the embodiment  FIG. 19 , or may join to form a single irregular opening, as shown in the embodiment in  FIG. 22 . The second elongate opening  532  may be defined by the clamp body  524  or the second elongate opening  532  may be created by the hinge of the clamp  520 . The first and second elongate openings  530 ,  532  may be substantially parallel to one another. The first and second elongate openings  530 ,  532  are preferably sized and dimensioned to receive the corresponding width and thickness of the tether  204 . Thus, the tether  204  is configured to be received by and through the first and second elongate openings  530 ,  532  in any suitable configuration to at least temporarily hold the tether  204  in the clamp body  524 . 
         [0054]    A preferred way of threading the tether  204  to the clamp body  524  is shown in  FIG. 19  by arrow A. As shown by arrow A, a free end  206  of the tether  204  is passed through the first elongate opening  530  in the clamp body  524  and back through the second elongate  532  such that the tether  204  substantially folds back onto itself. When the tether  204  is passed through the clamp body  524  (as shown by arrow A), the clamp  520  will temporarily hold the position of the tether  204  when the tether  204  is tensioned. Thus, the tether  204  may be appropriately tensioned by pulling on the free end  204  of the tether  204  and advancing the tether  204  through the first and second elongate openings  530 ,  532 . Similarly, the tension may be reduced by allowing the tether  204  to retract back through the first and second elongate openings  530 ,  532 . 
         [0055]    Once the tether  204  is appropriately tensioned, the hasp body  526  may be closed into contact with or close into contact with the clamp body  524 . The hasp body  526  also extends from a distal end to a proximal end. The distal end of the hasp body  526  forms a hinge sleeve portion  534 . The hinge sleeve portion  534  may have an opening extending longitudinally therethrough sized and configured to receive a pivot pin  536 . The opposing ends of the pivot pin  536  are each configured to be received in and engage one or more openings extending through the clamp body  524 . Thus, the pivot pin  536  enables the hasp body  526  to pivot or angulate with respect to the clamp body  524 . For example, the hasp body  526  may be positioned at an angle ranging from about 45-180°, about 50-120°, about 60-110°, about 70-100°, or about 90° relative to the clamp body  524 , when in an opened position. 
         [0056]    The hasp body  526  includes a through hole  538  extending through the hasp body  526 . The through hole  538  may be positioned closer to the distal end of the hasp body  526 . The through hole  538  may by generally spherical in cross-section and sized and dimensioned to receive at least a portion of the fastener  528 . The inner surface of the through hole  538  may be non-threaded or threaded. When the hasp body  526  is aligned with the clamp body  524 , the through hole  538  of the hasp body  526  aligns with the through hole  522  of clamp body  524 . As shown in  FIG. 20 , when the through holes  522 ,  538  are aligned, fastener  528  may be inserted therethrough to lock the tether  204  to the clamp  520 . The through hole  538  of the hasp body  526  may be substantially the same size or larger than the through hole  522  of clamp body  524 . The through hole  538  is preferably sized larger to receive a head portion  540  of the fastener  528  when recessed into the hasp body  526 . 
         [0057]    Referring to  FIG. 21 , the fastener  528  is attachable to the clamp  520  and the rod  326  in order to compress the tether  204  between the hasp body  526  and the clamp body  524 , thereby providing a more substantial, permanent hold. The fastener  528  may include a head portion  540  and a shaft portion extending therefrom. The head portion  540  may include a recess sized and configured to receive a driving instrument, such as a hex driver, in order to rotate and insert the fastener  528  through the through holes  538 ,  522  and into an opening  324  in the elongate rod  326 . Thus, the fastener  528 , when tightened, causes the hasp body  526  including the hinge sleeve portion  534 , which may be enlarged relative to the rest of the hasp body  526 , to squeeze the tether  204  between the clamp body  524  and the hasp body  526  and/or hinge sleeve portion  534  to permanently secure the tether  204  in position. The hinge sleeve portion  534  is preferably sized and dimensioned to apply an appropriate force to the tether  204  to secure the tether to the clamp  520 . As shown, the hinge sleeve portion  534  may have a generally cylindrical or partially spherical shape, which is enlarged relative to the rest of the hasp body  526 , to further tighten the tether  204  when the hasp body  526  is rotated to the closed position. 
         [0058]    Referring now to  FIGS. 22 and 23 , another version of a tether clamp  620 , in the form of a hinged clamp, configured to clamp the tether  204  with the clamp  620  is shown. Similar to tether clamp  520 , the hinged tether clamp  620  includes a main clamp body  624 , a hasp body  526  hingedly connected to the clamp body  624 , and a fastener  628  configured to secure the hasp body  626  to the clamp body  624  and the clamp  620  to the elongate rod  326 .  FIG. 22  shows the clamp  620  in an open configuration, and  FIG. 23  shows an exploded view of the clamp  620 , elongate rod  326 , and fastener  628 . 
         [0059]    As shown in  FIG. 22 , the clamp body  624  may have a generally U-shaped body. The clamp body  524  may include a through hole  622  extending through the clamp body  624 . The through hole  622  may have a partial-spherical cross-section and sized and dimensioned to receive at least a portion of the fastener  528 . The inner surface of the through hole  622  may be threaded to mate with corresponding threads on the fastener  628 . The clamp body  624  further includes an enlarged opening  630  extending through the clamp body  624 . The enlarged opening  630  and through hole  622  may join to form a single irregular opening (e.g., a key-shaped opening defined by the outer U-shaped clamp body  624 ). An elongate pin member  642  may connect a first side to a second side of the U-shaped clamp body portion  624 . In particular, opposing ends of the pin member  642  are each configured to be received in and engage one or more openings extending through the clamp body  624 . The tether  204  is configured to be received around the elongate pin member  642  in any suitable configuration to at least temporarily hold the tether  204  in the clamp body  624 . The tether  204  may be looped around the pin member  642  and in direct contact with the pin member  642  for temporary attachment. 
         [0060]    Similar to the threading of the tether  204  shown in  FIG. 19 , a free end  206  of the tether  204  may be passed through the space between the through hole  622  and the pin member  642  in the clamp body  624  and back through the space between the pin member  642  and the hinge sleeve portion  634  such that the tether  204  substantially folds back onto itself The clamp  620  will temporarily hold the position of the tether  204  as the tether  204  is appropriately tensioned to correct the spinal deformity. 
         [0061]    The hasp body  626  includes a through hole  638  extending through the hasp body  626 . When the hasp body  626  is aligned with the clamp body  624 , the through hole  638  of the hasp body  626  aligns with the through hole  622  of clamp body  624  and fastener  628  may be inserted therethrough to lock the tether  204  to the clamp  620 . Once the tether  204  is appropriately tensioned, the hasp body  626  may be closed into contact with or close into contact with the clamp body  624 . The distal end of the hasp body  626  forms an enlarged hinge sleeve portion  634  including an opening extending longitudinally therethrough sized and configured to receive a pivot pin  636 . The opposing ends of the pivot pin  636  are each configured to be received in and engage one or more openings extending through the clamp body  624 . Thus, the pivot pin  636  enables the hasp body  626  to pivot or angulate relative to the clamp body  624  and allows for open and closed configurations of the clamp  620 . 
         [0062]    The fastener  628  may include a head portion  640  and a shaft portion extending therefrom. A portion of the shaft portion may be threaded, as shown in  FIG. 23 . The shaft portion may be threaded along the entire length or any suitable portion thereof. Preferably, at least the portion of the shaft in contact with the through hole  622  in the clamp body  624  and the opening  324  in the elongate rod  326  is threaded. The head portion  540  may include a recess sized and configured to receive a driving instrument, such as a hex driver, in order to rotate and insert the fastener  628  through the through holes  638 ,  622  and into an opening  624  in the elongate rod  626 . 
         [0063]    As best seen in  FIG. 23 , the elongate rod  626  and clamp  620  may further include a clutch feature in the form of radial grooves  325  and corresponding radial grooves (not visible) on the back of the clamp  620  so that no counter-torque instrument is needed to prevent rotation of the clamp  620  during tightening of the fastener  628 . The radial grooves  325  may be in the form of radial slots, protrusions, or the like extending around the opening  324  in the elongate rod  326 . The corresponding radial grooves include mating radial slots, protrusions, or the like extending around the opening  622  in the clamp body  624 . The fastener  628  is attachable to the clamp  620  and the rod  626  in order to compress the tether  604  between the hasp body  626  and the clamp body  624 , thereby providing a more substantial, permanent hold. Thus, the fastener  628 , when tightened, squeezes the tether  204  between the clamp body  624  and the hasp body  626  to permanently secure the tether  604  in position. 
         [0064]    Referring now to  FIGS. 24 and 25 , correcting a spinal deformity, such as scoliosis, is described further.  FIG. 24  depicts a posterior view of a deformed human spine  104  with an implanted device, and  FIG. 25  depicts a posterior view of a corrected human spine  104  after the tether  204  has been tensioned. As described elsewhere in this document, the implanted device may include two attachment mechanisms, such as pedicle screws  300 , which are anchored to the vertebra of the spine by insertion into opposing pedicles, and a transverse rod  311  connected between the pedicle screws  300 . 
         [0065]    An ilium anchor  210  is attached to the ilium  102  to secure one end of the tether  204 . The ilium anchor  210  may be in the form of a bushing inserted through a hole drilled in the ilium  102 . The anchor  210  may have threads on its exterior surface to bite into the bone. The exterior surface may also include a coating of porous material, hydroxyapatite, bioconductive material, and/or bioinductive material. The tether  204  may be passed through the anchor  210  and secured, for example, with a buckle, a loop, or other connection mechanism. The free end  206  of the tether  204  is passed through a tether clamp, for example, tether clamp  320  described elsewhere herein or any other suitable tether clamp. The tether clamp  320  may be attached to the transverse rod  311  at any suitable location along its length. For example, the tether clamp  320  may be connected to the transverse rod  311  at one end of the transverse rod  311 . The tether  204  may be tensioned until the deformity is corrected as shown in  FIG. 25 . 
         [0066]    The tether system may have a number of advantages. Because the tether  204  connects the spine  104  to the ilium  102 , the tether  204  uses the pelvis as a foundation from which to exert corrective forces onto a scoliotic spine. The tether system is not in the axial load path of the spine so forces typically borne by the spine continue to be borne by the spine. There may be no need for fusion during the life of the implant, but the system may be used prior to fusion if desired (e.g., a surgeon may use the tether system to prevent curve progression or correct a curve and then later fuse the spine with a subsequent surgery). The procedure is minimally invasive and may reduce operating room time and/or recovery time. The tether  204  is adjustable with a small incision to accommodate progressive correction and to prevent overcorrection during growth modulation procedures. 
         [0067]    Referring now to  FIGS. 26 and 27 , a method and device for scoliosis correction are shown. In particular, the device and method may include de-rotating the vertebra in the axial plane. While traditional scoliosis correction attempts to laterally shift the spine, this method de-rotates the spine because axial rotation and lateral shift are mechanically coupled in the thoracic spine by the ribcage. In other words, axial rotation of one or more vertebra correlates to a lateral shift in the spine and correction of the scoliotic spine. This method does not need to involve fusion to correct the spinal deformity. 
         [0068]    As shown in  FIG. 26 , a non-fusion implant  700  may be used to impose a de-rotating tension on a pedicle screw  702  by using the posterior-most aspect of the ribs  110  as an anchor point. The implantation may be a minimally invasive surgical procedure, for example, through a small midline incision. The implant  700  may include one or more plates  704  configured to contact the ribs  110  and a pedicle screw  702  extending through the plate  704 . The plate  704  may be substantially straight, curved, or contoured as necessary to extend to the posterior-most aspect of the ribs  110  on either side of the vertebra  108 . 
         [0069]    The plate  704  may be implanted to abut the posterior aspect of the ribs  110  on both sides of the patient. The plate  704  may be coupled to the ribs  110  or may merely contact the ribs  110  without coupling thereto. The pedicle screw  702  with a threaded shank  706  may be passed through a slot  708  in the plate  704 . The slot  708  may be sized to receive the shank  706  or may be elongated to allow for movement of the shank  706  along the length of the plate  704 . A coupling element, such as a nut  710 , may be used to secure the screw  702  to the plate  704 . By rotating the nut  710  onto the threaded shank  706 , the pedicle is pulled closer to the plate  704 . This action causes de-rotation of the vertebra  108  and alignment of the spine. The de-rotation can be performed acutely or progressively over a period of time by re-accessing the nut  710  with a small incision and adjusting at one or more different points in time after the initial surgery. 
         [0070]    In another embodiment, shown in  FIG. 27 , instead of coupling with a nut, the threaded shank  706  may be received in a coupling sleeve  712 . The coupling sleeve  712  may include a threaded opening extending longitudinally therethrough sized and dimensioned to receive the threaded shank  706  of the screw  702 . The coupling sleeve  712  may include an enlarged head portion configured to engage with the slot  708  in the plate  704 . By rotating the coupling sleeve  712  onto the threaded shank  706 , the pedicle is once again pulled closer to the plate  704  in order to de-rotate the vertebra  108  in the axial plane. Although depicted entering one pedicle of the vertebra  108 , it is envisioned that the pedicle screw  702  could enter the opposite pedicle screw to apply torque to the vertebra  108  in the other direction. Alternatively, if pedicle screws cannot be used, for example, in the case of a small pediatric patient, a sublaminar band or wire can be attached to the plate  704  and tensioned as necessary to provide the desired axial movement. Regardless of the mechanism, the axial rotation of one or more vertebrae provides for a lateral shift in the spine and correction of the deformity. 
         [0071]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Moreover, the improved bone screw assemblies and related methods of use need not feature all of the objects, advantages, features and aspects discussed above. Thus, for example, those skilled in the art will recognize that the invention can be embodied or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. In addition, while a number of variations of the invention have been shown and described in detail, other modifications and methods of use, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is contemplated that various combinations or subcombinations of these specific features and aspects of embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the discussed bone screw assemblies. Thus, it is intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of the appended claims or their equivalents.