Abstract:
The present invention generally relates to methods and devices for treatment of spinal deformity, and in particular to the utilization of at least one implant to either maintain the position of at least one vertebra of a patient to prevent increase in abnormal spinal curvature, to slow progression of abnormal curvature, or to impose at least one corrective displacement and/or rotation on at least one vertebra of a patient so as to incrementally correct abnormal spinal curvature.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 11/215,725, filed Aug. 30, 2005, entitled “IMPLANT FOR CORRECTION OF SPINAL DEFORMITY,” by Jeffrey D. Gordon, which claims the benefit, pursuant to 35 U.S.C. §119(e), of provisional U.S. patent application Ser. No. 60/605,548, filed Aug. 30, 2004, entitled “IMPLANT FOR CORRECTION OF SPINAL DEFORMITY,” by Jeffrey D. Gordon, the contents of which are incorporated herein in their entireties by reference, respectively. 
     
    
     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 and is often associated with an abnormal rotation in the axial plane causing ribs to protrude posteriorly into what is commonly referred to as “rib hump”. 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, disclosed in U.S. Pat. No. 5,147,360 to Dubousset, 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. Typically, extensive discectomies are necessary, as well as removal of the spinous processes and injury to the spine itself to induce bleeding to aid bone fusion. The spine is then fused with bone graft harvested from the patient&#39;s illium or from a bone bank.  
         [0005]     The surgery is arduous, invasive, and has an array of potential complications. Large loads are exerted on the spine for correction [1] which risks the patient&#39;s neurological condition. A long incision is required and extensive bone graft is harvested, therefore excessive blood loss can occur. Recovery can be a lengthy and painful process. If normal lordosis and kyphosis are not restored, a condition called “flat back syndrome”, the patient may have 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 in jeopardy of degeneration due to the increased biomechanical demands placed on them. In general, it is a major surgery with the possibility of major complications.  
         [0006]     Therefore, it is evident 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-Dubousset system rigidly attaches stiff stainless steel 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 geometry of the implants used is such that they will not support such loads indefinitely. Fatigue failure of the implant will occur if fusion is delayed.  
         [0007]     The mechanical properties of spinal structures such as the intervertebral discs, ligaments, nerves and muscles have a time-dependent relationship between force and displacement, a characteristic called viscoelasticity. Viscoelastic structures increase strain under the action of an applied constant stress (creep) and decrease internal stress under the action of an applied constant strain (stress-relaxation). It has been shown that dramatic stress-relaxation occurs over time in patients who have undergone scoliosis correction surgery involving stiff metal rods [1]. However, the stiffness of the rods prevents them from taking advantage of this phenomenon.  
         [0008]     U.S. Pat. No. 5,490,851 to Nenov et al. describes a pelvis alignment device which rigidly attaches to the pelvis to align the pelvic girdle. After alignment with this device, artificial joints are used to hold the pelvis and sacrum in the aligned position. Flexible cords with worm gear drive members are attached so that “force is applied to the distorted spine so that it does not tend to act against the effects of the joints”. Therefore, the flexible cords work in conjunction with the artificial joints to maintain alignment correction achieved with a pelvis alignment device.  
         [0009]     U.S. Pat. No. 6,849,076 to Blunn et al. describes a group of magnet driven devices for surgical distraction. A device for correction of scoliosis is described which is attached to two vertebrae and is non-invasively distracted by an external changing magnetic field.  
         [0010]     U.S. Pat. No. 6,299,613 to Ogilvie et al. describes a tether connected to points on the spine to maintain a curvature, or to constrain growth of the convex side of the spine.  
         [0011]     Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.  
         [0012]     U.S. Patent Documents  
                                                           4448191   May 15, 1984   Rodnyansky et al.           5147360   Sep. 15, 1992   Dubousset           5290289   Mar. 1, 1994   Sanders et al           5490851   Feb. 13, 1996   Nenov et al.           6299613   Oct. 9, 2001   Ogilvie et al.           6849076   Feb. 1, 2005   Blunn et al.                      
 
       SUMMARY OF THE INVENTION  
       [0013]     The current invention describes a method and devices for treating spinal deformity which offers significant improvements over prior art methods and devices. Treatment of spinal deformity, such as scoliosis, includes: preventing or reducing progression of an abnormal spinal curvature prior to fusion, preventing or reducing progression of an abnormal spinal curvature without fusion, correction of an abnormal spinal curvature prior to fusion, correction of an abnormal spinal curvature without fusion, or maintenance or improvement of a surgically corrected spinal curvature.  
         [0014]     In general terms the concept behind the present invention is introduction of tension between the pelvis and spine to either correct or maintain spinal deformity. The tension force may take the form of a maintained or incrementally reduced length between at least one point on the spine and at least one point on the pelvis which will consequently produce a resisting tension force when acted against by the patient&#39;s musculature. There are many embodiments of the invention which will achieve the stated objectives, some of which will be presented in the following summary.  
         [0015]     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 such as a twisted (helically wound, or laid) wire rope, braided wire rope, twisted non-metallic rope, braided non-metallic rope, a rope consisting of metallic and non-metallic fibers, multiple strand wire, single strand wire, multiple strand polymer, single strand polymer, Kevlar, link chain, bead chain, or a metallic or non-metallic tape. Alternatively, the tether could be a rigid rod or telescoping tubes which contracts but has an adjustable stop to limit extension.  
         [0016]     Attachment of the flexible tether to the spine and/or pelvis might involve a loop of material placed around a boney structure (e.g. the spineous process), or a hole through a boney structure through which the flexible tether is passed. Alternatively, it may be necessary to implant attachment means at the spine attachment site(s) and/or the pelvis attachment site(s) and then attach the tether to the attachment means. For example, at least one bone screw, cannulated bone screw, clamp, plate, bone anchor, or shackle might be attached to at least one vertebra or pelvic bone and the flexible tether may be attached to it. Other means of attachment will be clear to one practiced in the art.  
         [0017]     The tether can branch into multiple tethers to provide multiple attachments to the spine and/or pelvis. 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 vertebra and either or both pelvic bones 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 pelvic bone, 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 pelvic bones and then attached to a second vertebra with a pedicle screw or other means. It can be envisioned by one skilled in the art that guiding devices may be utilized on a number of vertebrae or on the pelvis. 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.  
         [0018]     In another embodiment of the invention, any of the above described devices may incorporate a means to shorten the overall length of the device. Taking advantage of the inherent viscoelasticity of spinal structures, the curvature is gradually corrected by small incremental corrections over a protracted period of time. In one embodiment, the means to shorten the device is a changing magnetic field. In another embodiment, the means to shorten the device is a toggle which can be manipulated by pressing on the patient&#39;s skin. In another embodiment, shortening the device requires an incision so that the device can be manipulated directly.  
         [0019]     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.  
       OBJECTS OF THE PRESENT INVENTION  
       [0020]     It is an object of the present invention to provide an improved method of arresting the progression of spinal deformity whereby at least one device is surgically attached to the spine and to a boney structure other than the spine, such as the pelvis.  
         [0021]     It is another object of the present invention to provide an improved method of correcting a spinal deformity whereby at least one device is surgically attached to the spine and to another boney structure other than the spine, such as the pelvis; the device being capable of being shortened to impose at least one incremental correction over a period of time.  
         [0022]     It is another object of the present invention to provide an improved method of correcting a spinal deformity with at least one device which is surgically attached to the spine and to another boney structure other than the spine, such as the pelvis, the device being capable of being shortened to impose at least one incremental correction over a period of time and which is actuated by a non-invasive method such as with a changing magnetic field or by pressing on the exterior surface of the patient&#39;s skin. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  shows schematically a posterior view of a deformed human spine with an implanted device according to one embodiment of the present invention.  
         [0024]      FIG. 2  shows schematically a posterior view of a corrected human spine with the implanted device shown in  FIG. 1 .  
         [0025]      FIG. 3  shows schematically a posterior view of a deformed human spine with an implanted device according to another embodiment of the present invention.  
         [0026]      FIG. 4  shows schematically a posterior view of a deformed human spine with multiple implanted devices according to another embodiment of the present invention.  
         [0027]      FIG. 5  shows schematically a posterior view of a deformed human spine with an implanted device according to another embodiment of the present invention.  
         [0028]      FIG. 6A  is an exploded, detail view of one embodiment of a guide means.  
         [0029]      FIG. 6B  is a detail view of one embodiment of a guide means.  
         [0030]      FIG. 7A  is an exploded, detail view of another embodiment of a guide means.  
         [0031]      FIG. 7B  is a detail view of another embodiment of a guide means.  
         [0032]      FIG. 8A  is an exploded, detail view of another embodiment of a guide means.  
         [0033]      FIG. 8B  is a detail view of another embodiment of a guide means.  
         [0034]      FIG. 9A  shows a perspective exploded view of a device according to one embodiment of the present invention.  
         [0035]      FIG. 9B  shows a perspective view of the device shown in  FIG. 9A .  
         [0036]      FIG. 10A  shows a sectioned view of the device shown in  FIGS. 9A and 9B  in an extended or “lengthened” configuration.  
         [0037]      FIG. 10B  shows a sectioned view of the device shown in  FIGS. 9A and 9B  in a retracted or “shortened” configuration.  
         [0038]      FIG. 11A  shows an exploded, perspective view of a spinal attachment member according to one embodiment of the present invention.  
         [0039]      FIG. 11B  shows a perspective view of the spinal attachment member shown in  FIG. 11A .  
         [0040]      FIG. 12  shows a perspective view of an actuator and a device according to one embodiment of the present invention.  
         [0041]      FIG. 13  shows a side view of the actuator and the device shown in  FIG. 12 .  
         [0042]      FIG. 14  is a cross-section of the actuator and the device shown in  FIGS. 12 and 13  showing magnetic flux lines for both the actuator magnet and the implanted magnet.  
         [0043]      FIG. 15  shows schematically a posterior view of a deformed human spine with an implanted device according to another embodiment of the present invention.  
         [0044]      FIG. 16  is a detail, perspective view of an alternative embodiment of the spinal attachment member.  
         [0045]      FIG. 17A  is an exploded, perspective view of a device according to another embodiment of the present invention.  
         [0046]      FIG. 17B  is a perspective view of the device shown in  FIG. 17A .  
         [0047]      FIG. 18A  shows a sectioned view of the device shown in  FIGS. 17A and 17B  in an extended or “lengthened” configuration.  
         [0048]      FIG. 18B  shows a sectioned view of the device shown in  FIGS. 17A and 17B  in a retracted or “shortened” configuration.  
         [0049]      FIG. 19A  shows an exploded perspective view of one embodiment of an instrument used for implantation of the device.  
         [0050]      FIG. 19B  shows a perspective view of the instrument shown in  FIG. 19A  in use during implantation surgery.  
         [0051]      FIG. 20A  shows an exploded perspective view of an alternative embodiment of an instrument used for implantation of the device.  
         [0052]      FIG. 20B  shows a perspective view of the instrument shown in  FIG. 20A  in use during implantation surgery. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0053]     The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.  
         [0054]     The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings. In accordance with the purposes of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to an implant for surgical treatment of abnormal spinal curvature by imposing restraints or corrective displacements to spinal vertebrae. For ease of understanding, the present invention is described with specific reference to scoliosis. However, the present invention disclosed herein is generally applicable to all classifications of spinal curvature disorders, including but not limited to hyper-lordosis, hyper-kyphosis, sagittal imbalance, and coronal imbalance.  
         [0055]      FIG. 1  is a schematic representation of a posterior view of a deformed spine  104  whereby one embodiment of the device  200  is attached to a pelvic bone  102  and a vertebra  100  of a patient. The device  200  includes an actuation means  201 , and a connection means  204 . Attachment of actuation means  201  to pelvic bone  102  is shown with a shackle  202  attached through a hole  210  created in pelvic bone  102 . Attachment of connection means  204  to vertebra  100  is shown with a pedicle screw  412 , a ball  404  and a crimp  406 . The initial angle of device  200  relative to horizontal is shown as R and the initial length of the exposed portion of connection means  204  is shown as L. More detailed drawings and descriptions follow.  
         [0056]      FIG. 2  is a schematic representation of a posterior view of the patient&#39;s spine  104  after correction of the abnormal spinal curvature with the implanted device  200 . In this figure, actuation means  201  has shortened the overall length of device  200  by pulling connection means  204  into actuation means  201  so that the exposed length L′ of connection means  204  is significantly shorter than the original exposed length L shown in  FIG. 1 . Also, the angle of device  200  relative to horizontal, represented by R′, is greater than the original angle R in  FIG. 1 .  
         [0057]      FIG. 3  is a schematic representation of an alternative embodiment of the invention, whereby a tether  280  is attached to vertebra  100  and to pelvic bone  102 , but does not have an actuation member. This embodiment can be used to prevent progression of spinal deformity, or can be shortened manually with an incision at either the pelvic bone  102 , or vertebra  100  attachment sites, or both, to correct a curvature. Preferably tether  280  is a wire rope, a cord or other such device as stated earlier. Alternatively, tether  280  can be a rigid member.  
         [0058]      FIG. 4  is a schematic representation of another alternative embodiment of the invention whereby multiple tethers  280  are utilized. Each tether  280  can be attached to a different vertebra  100  as shown, or multiple tethers  280  can be attached to the same vertebra  100 . Alternatively, each tether  280  may branch into multiple tethers at one or both ends to provide multiple attachment means for each tether. Tethers  280  can be attached to either or both sides of the vertebra  100  and either or both pelvic bones  102  as needed to generate correction of the spinal deformity. A crossing pattern whereby a tether  280  is attached to the right side of the vertebra  100  (e.g. the right pedicle) and left pelvic bone  102 , or vice versa, is possible. Attachment to the spineous process is also possible. Also, tethers  280  may be attached to a pelvic bone  102 , passed through a guiding device (e.g. an eye screw or other guiding device through which tethers  280  may slide) which is attached to a vertebra  100 , and then attached to a second vertebra  100  with a pedicle screw or other means, or it may terminate at the same or the opposite pelvic bone  102 . It can be envisioned by one skilled in the art that guiding devices may be utilized on a number of vertebrae to correct spinal deformity.  
         [0059]      FIG. 5  is a schematic representation of another alternative embodiment of the invention whereby a first flexible member  915  is attached to a first vertebra  100  with a vertebral anchoring means  920 ; a second flexible member  917  is attached to a second vertebra  100  with a vertebral anchoring means  920 ; and a sheath  910  is attached to at least one pelvic bone  102  with at least one bracket  912  secured with at least one bone screw  914 . First flexible member  915  is attached to an actuation means  201  which is capable of invasively, or non-invasively contracting as described above. Second flexible member  917  is passed through sheath  910  and then attached to actuation means  201 . Second flexible member can preferably slide within sheath  910  with minimal friction, thereby reducing or eliminating abrasion to second flexible member  917  and/or pelvic bone  102  and the sacrum. Actuation of actuation means  201  will shorten the overall length of the entire device by pulling either first flexible member  915  or second flexible member  917  into its housing. This shortening will impose a corrective displacement and/or force on the deformed spine, while preferrably allowing some motion of the spine for daily activities. Multiple first flexible members  915 , second flexible members  917 , sheaths  910  and/or actuation means  201  can be utilized to correct the deformity.  
         [0060]      FIGS. 6A through 8B  show alternative embodiments of guide means for the pelvic bone attachment.  FIG. 6A  is an exploded, perspective view of the preferred embodiment of the pelvic guide means  900  showing sheath  910  with second flexible member  917  passed through it, and bracket  912  securing sheath  910  to pelvic bone  102  with bone screw  914 .  FIG. 6B  shows the assembled pelvic guide means  900 .  FIG. 7A  is an exploded, perspective view of an alternative embodiment of the pelvic guide means  901 , whereby the sheath is replaced by a bracket guide means  960  which guides second flexible member  917 . Bracket guide means  960  is attached to pelvic bone  102  with bone screw  914 .  FIG. 7B  shows the assembled pelvic guide means  901 .  FIG. 8A  is an exploded, perspective view of an alternative embodiment of the pelvic guide means  902  whereby a pulley  952  is attached to pelvic bone  102  with a bone screw  914 . Pulley  952  will rotate and guide second flexible member  917 .  FIG. 8B  shows the assembled pelvic guide means  902 .  
         [0061]      FIGS. 9A through 10B  show one embodiment of the device  200  whereby actuation means  201  is actuated by a changing magnetic field. Actuation means  201  is shown to consist of a diametrically magnetized magnet  220  which is bonded or otherwise rotationally constrained within a cavity  234  of a tubular leadscrew  218  which has helical threads  219  on its exterior surface. The ends of tubular leadscrew  218  are plugged with a first end cap  222  and a second end cap  216 , and this assembly is welded or otherwise hermetically sealed to prevent corrosion of magnet  220 . A ball end  214  is swaged onto connection means  204  which is passed through a hole in a bearing cap  208 . Bearing cap  208  is then welded or otherwise permanently attached to second end cap  216 . Connection means  204  should therefore be able to rotate freely relative to the rest of the assembly. A shackle  202  is attached to a housing  203  with a pin  206 . Shackle  202  should be able to rotate about both axes which are orthogonal to the axis of housing  203 , thereby allowing alignment of actuation means  201  between pelvic bone  104  and vertebra  100 . The inside of housing  203  is threaded to match the threads of tubular leadscrew  218  so that the entire assembly attached to tubular leadscrew  218  can be threaded into housing  203 . The assembled device is shown in  FIG. 9B .  
         [0062]      FIGS. 10A and 10B  show a section view of device  200 .  FIG. 10A  shows the ‘as implanted’ configuration and  FIG. 10B  shows the device after it has been significantly contracted or “shortened”. Tubular leadscrew  218  threads down into housing  203  when turned by magnet  220  which is rotationally constrained within it. Bearing cap  208  allows tubular leadscrew  218  to rotate without twisting connection means  204 .  
         [0063]      FIGS. 11A and 11B  show one embodiment of the spinal attachment means  209 . A pedicle screw  402  with screw threads  414  for attachment to a pedicle, has a through hole  410  and a spherical recess  408 . A ball  404  also has a hole. Flexible member  204  is passed through hole  410  and through the hole in ball  404  and a crimp  406  is secured on the end by crimping or swaging. Crimp  406  could easily be replaced with a swaged stop sleeve, a threaded stud, an eye, a clamp, or other means. Therefore, ball  404  articulates with spherical recess  408  when there are movements of connection means  204 .  FIG. 11B  shows the assembled spinal attachment means  209 . This is just one of many possible means to attach connection means  204  to vertebra  100 .  
         [0064]      FIGS. 12 through 14  show the preferred embodiment of the actuation means  300 . A magnet  302 , which is diametrically magnetized as indicated on the figure by the north (N) and south (S) poles, is rigidly fixed to a first axle  316  which rotates within a frame  320 . A handle  304  is connected to frame  320 . A crank  306  is rigidly fixed to a second axle  314  which is also rigidly fixed to a first pulley  312   a . A belt  308  wraps around first pulley  312   a  and a second pulley  312   b  which is rigidly fixed to the same axle  316  to that which magnet  302  is fixed. Rotation of crank  306  will rotate first pulley  312   a  and second pulley  312   b  (by the action of belt  308 ) which rotates axle  316  and therefore magnet  302 . This action is shown schematically by the arrows in the figure. In short, rotation of crank  306  rotates magnet  302 . There are many ways to rotate a magnet and this single example is not meant to limit the scope of the invention.  
         [0065]     Actuation means  300  is positioned so that frame  320  is nearby, or in contact with, the patient&#39;s skin and magnet  302  is aligned approximately parallel to housing  203 . Magnet  302  has a magnetic field shown by magnetic flux lines  500  in  FIG. 14 . This magnetic field interacts with a magnetic field (shown by magnetic flux lines  502 ) generated by magnet  220 . Opposite poles (NS or SN) tend to attract and like poles (NN or SS) tend to repel. Therefore, rotation of one diametrically magnetized magnet situated roughly parallel to a second diametrically magnetized magnet will cause rotation of the second magnet. In short, rotation of crank  306  rotates magnet  302  which rotates magnet  220  within device  200  by magnetic attraction and repulsion. In this way, device  200  can be actuated non-invasively. If external magnet  302  turns without turning the implanted magnet  220 , there will be a significant rotational resistance as like poles of the two magnets pass by each other. Therefore, there is feedback inherent to the system to tell the operator if the device  200  is functioning correctly.  
         [0066]     An electromagnet may be substituted for the permanent magnet  302 . The electromagnet could produce a static magnetic field and then be physically rotated, or the field created could be a dynamic field that does not require physical rotation. Instead of manually turning permanent magnet  302 , a motorized device could be used which might contain a control system to measure the rotational resistance described above and warn the operator in the case of improper operation.  
         [0067]      FIG. 15  shows a schematic representation of a deformed spine with another alternative embodiment of the device  200 .  FIG. 16  shows the spinal attachment means in greater detail. Two pedicle screws  608  are shown locked to a bar  610  with set screws  604  to form a rigid construct that is well anchored to the spine. Connection means  204  is looped around bar  610  and secured by a crimp  606 . A thimble may be incorporated to reduce abrasion of connection means  204 . Alternatively, connection means  204  may be secured to bar  610  with a clamp or other securing means or may be tied with a knot.  
         [0068]      FIGS. 17A through 18B  show an alternative embodiment of the device  700 . A loop is formed in connection means  204  which is held in place with a crimp or swage  703 . A housing  704  has a pin  716  which is pushed through the loop in connection means  204  to permanently secure connection means  204  to housing  704 . The opposite end of connection means  204  is attached to the spine (not pictured) as described above. Housing  704  has wings  705 , a pin hole  717 , a first bore  729  and a second bore  730 . Leadscrew  718  has a head  708 , a shank  710 , and a right-hand threaded portion  712 . Leadscrew  718  is slid into second bore  730  until head  708  abuts the bottom of second bore  730 , and a one-way clutch  714  is slid into first bore  729  over threaded portion  712  and onto shank  710  as shown in  FIGS. 15 &amp; 16 . One-way clutch  714  will allow housing  704  to rotate counter-clockwise, but will rotationally lock housing  704  to leadscrew  718  when housing  704  is rotated clockwise. A threaded housing  706  is threaded onto leadscrew  718 . When one of wings  705  is pressed, housing  705  is rotated. If the resulting rotation is clockwise, leadscrew  718  advances into threaded housing  706 , drawing threaded housing  706  into housing  704 , thereby shortening the overall length of the device  700 . If the rotation is counter-clockwise, housing  704  free-wheels on one-way clutch  714  and leadscrew  718  is not rotated. Therefore, pressing alternately on wings  705  will shorten device  700 . Alternatively, leadscrew  718  may have left-hand threads and one-way clutch  714  may engage when housing  704  is rotated counter-clockwise, achieving the same effect as stated above. Since device  700  is implanted just under the skin, pressing on the patient&#39;s skin from outside the body will cause shortening of device  700  non-invasively.  
         [0069]      FIGS. 19A and 19B  show an instrument means  800  for implanting device  200 , device  700 , or tether  280 . Instrument means  800  consists of an elongated tube  801 , and a cap  810  with threads  812  which engage matching threads within the end of elongated member  801 . A pelvic incision  845  and a spinal incision  850  are made at the site(s) planned for pelvic attachment or guide(s) and site(s) planned for spinal attachment or guide(s), respectively, of device  200 , device  700  or tether  280 . Instrument means  800  is introduced into one of these incisions and is manipulated by the surgeon until it reaches the other incision and has created a tunnel which will accommodate the appropriate implant(s). The cap is then removed and the implant(s) is fed into elongated tube  801  so that the ends of the implant(s) are present at the incisions and can be handled by the surgeon. Instrument  800  may then be removed. Instrument  800  can have any cross-sectional shape, can be curved or straight, and can be made from a surgical grade metal, polymer, ceramic, or composite, and may be a disposable item.  
         [0070]      FIGS. 20A and 20B  show an alternative instrument means for implanting device  200 , device  700 , or tether  280 . A pelvic incision  845  and a spinal incision  850  are made at the site(s) planned for pelvic attachment or guide(s)and site(s) planned for spinal attachment or guide(s), respectively, of device  200 , device  700  or tether  280 . Forceps  900  are introduced into one incision and are manipulated by the surgeon until reaching the other incision. One end of the implant(s) is grabbed with forceps  900  and the implant(s) is pulled to the other incision.  
         [0071]     The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.  
         [0072]     The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.  
         [0000]     [1] Nachemson, A., Elfstrom, G. “Intravital wireless telemetry of axial forces in Harrington distraction rods in patients with idiopathic scoliosis” Journal of Bone and Joint Surgery 1971; 53:445-465