Abstract:
An orthosis for correcting spinal deformities by urging spinal vertebrae toward a vertical axis. The orthosis includes a series of retaining clamps fixed onto the spinous process of said vertebrae, each of said retaining clamps having guides for retaining at least one elastic rod.

Description:
CROSS-RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. Ser. No. 11/656,314, filed Jan. 19, 2007, which is fully incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is directed to apparatus which is designed to be implanted within a patient exhibiting spinal disorders such as scoliosis in a way that requires less invasive surgery than prior devices of this kind and which do not involve fusion of the spinal column while achieving results which compare favorably to competitive apparatus. 
       BACKGROUND 
       [0003]    Scoliosis is a disease which deforms the spine affecting more girls than boys and manifesting itself during the teen years when significant growth is experienced. Scoliosis generally combines a horizontal torsion and flexion in a frontal plane and develops in three spatial dimensions. As noted, the disease generally begins with the growth phase as it is hypothesized that this is probably due to the rotation of one or two vertebral bodies. 
         [0004]    Sufferers of scoliosis are generally treated initially with a rigid corset-like orthopedic brace. If this treatment proves unsuccessful, surgery is oftentimes resorted to. This involves the use of implantable apparatus including one and oftentimes two rods mounted on either side of the spinal column. If two rods are employed, anchoring means are provided positioning the rods in spaced-apart parallel alignment. Hooks or screws are employed to anchor the rods along the selected portion of the spinal column requiring intervention. Once installed, the anchors are rigidly locked to the associated rod to prevent relative motion there between and the entire arrangement supplemented with bone grafts causing fusion of the vertebrae in the area in which scoliosis has manifested itself. 
         [0005]    Although spinal fusion can oftentimes largely correct a spinal deformity, such procedure is not without serious drawbacks. Spinal fusion can result in complications as the patient advances into adult life. Also, the surgery requiring the application of bone grafts and permanent fixation of supporting clamps to the transverse process is significantly invasive. 
         [0006]    Others have suggested improvements to the orthosis described above. For example, U.S. Pat. No. 6,554,831 suggests a system that allows for intra-operative correction and micro-movement of the vertebrae despite implantation of a corrective rod. The &#39;831 patent suggests use of a rigid rod that does not allow a patient to flex or extend post-operatively until the corrective rod is removed requiring additional surgery. Anchoring to the transverse process is also taught thus requiring significant invasive surgery and consequent fusion. 
         [0007]    U.S. Pat. No. 5,672,175 suggests another approach which theoretically provides a patient with close to normal range of motion of the vertebrae by instrumenting the spine with elastic members pre-curved to correct the spinal deformity. Anchoring to the transverse process is also employed which, again, is a major drawback in performing the techniques suggested in the &#39;175 patent. Further, this device theoretically overcomes the deformity with constant force applied by pre-curved correction members but this does not allow for resultant changes in the deformity or tissue relaxation. Because of the use of these pre-curve rods, the technique suggested in the &#39;175 patent may actually result in a final deformity completely opposite to the original deformity due to tissue growth and relaxation. 
         [0008]    U.S. Pat. No. 4,697,582 suggests a correction apparatus which employs an elastic rod or a pair of elastic rods exhibiting a memory shape of the corresponding part of a normal rachis, the rods being immobilized in rotation in each of its guidance openings. However, the mechanical assembly suggested in the &#39;582 patent is appended to an area on each vertebrae between the spinal process and transverse process which again results in significant invasive surgery and results in fusion between vertebrae being established in the to be corrected region. 
         [0009]    It is thus an object of the present invention to provide an appliance to correct spinal deformities while eliminating or significantly reducing the drawbacks of the prior art. 
         [0010]    The present invention is further directed to an appliance to correct spinal deformities which does not result in spinal fusion and which significantly reduces the extent of invasive surgery and which substantially eliminates post operative drawbacks such as those exhibited by competitive apparatus. 
         [0011]    These and further objects will be more readily apparent when considering the following disclosure and appended claims. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention is directed to an orthosis for correcting spinal deformities by urging spinal vertebrae towards a vertical axis, said orthosis comprising a series of retaining clamps fixed to the spinal (spinous) process of the vertebrae, each of the retaining clamps having guides for retaining at least one elastic rod. Ideally, the rod so implanted is immobilized in rotation within one of the guides. Two such rods can be employed to apply a corrective moment to rotational deformity of the spine in its axial plane. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0013]      FIG. 1  is a perspective view of a portion of a spine bearing the orthosis of the present invention. 
           [0014]      FIG. 2  is a partial perspective view showing a portion of the spinous process of a vertebrae bearing a clamp for use in applying the orthosis of the present invention. 
           [0015]      FIG. 3  is a perspective view, partially in cross section, showing a preferred embodiment of a correction rod useful in practicing the present invention. 
           [0016]      FIG. 4  is a perspective view of a clamp bearing a correction rod illustrating one of the embodiments of the present invention. 
           [0017]      FIG. 5  is a perspective view of clamping plates used as an alternative to the clamp shown in  FIG. 4 . 
           [0018]      FIGS. 6 and 7  illustrate a healthy spine in the sagittal and anterior/posterior views, respectively, in conjunction with correction rods contemplated for use herein. 
           [0019]      FIG. 8  is a perspective view of the clamping plates of  FIG. 5  showing their application to the spinous process of a vertebrae bearing correction rods for use herein. 
           [0020]      FIG. 9  is a side plan view of a series of vertebrae employing the clamping plate of  FIG. 8 . 
           [0021]      FIG. 10  is a partial plan view of a correction rod for use herein showing one of the several ways to constrain motion of the rod once installed. 
           [0022]      FIG. 11  is a perspective view of a corrective rod assembly proposed as a preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Referring first to  FIG. 1 , a portion of the human spine  10  is depicted having a series of vertebrae  11 . Each vertebrae includes the spinous process  12  that transitions to the transverse process  13  through vertebral arch  18 . It is important to note in carrying out the present invention that retaining clamps  14  are applied only to the spinous process thus significantly reducing the extent of invasive surgery and elimination or significantly reducing resultant spinal fusion. As noted previously, the prior art either applies retaining clamps to the transverse process  13  or at least to the vertebral arch  18  which for the reasons expressed herein, provides for spinal fusion, relatively significant invasive surgery and consequent patient discomfort and potentially long term physiological disadvantages. 
         [0024]    Retaining clamp  14  can be seen in greater detail by making reference to  FIG. 2 . Specifically, retaining clamp  14  is shown embracing spinous process  12 . Retaining clamp  14  remains positioned thereon through the use of fixation screw  22  passing through opening  23  in retaining clamp  14  which thus passes within the body of the vertebrae at spinous process  12 . A correction rod, the details of which will be discussed hereinafter, is intended to pass within and be carried by retaining clamp  14  at axial opening  21 . When two correction rods are employed, a complimentary axial opening  21  a can be configured within clamp  14 . 
         [0025]    The present invention is intended to correct spinal deformities by generating corrective forces on any vertebrae in deviation from its anatomic or healthy position. This is done by providing corrective rods  16 / 17  within an axial openings  21 / 21   a.  In referring to  FIG. 3 , as a preferred embodiment, these elastic corrective rods can be designed to offer differing bending moments of inertia for each plane. This is important when dealing with a lateral deformity, such as scoliosis whereby rod  16  ( FIG. 3 ) would generate lower forces on the vertebrae during flexion-extension of the spine but greater corrective forces on the lateral deformity. Such a feature would allow for easier or less painful natural motion while still providing sufficient force for reduction of the deformity. In referring to  FIG. 3 , rod  16  would thus be much stiffer and resistant to bending in the direction of arrow  28  than in the direction of arrow  29 . 
         [0026]    Again referring to rod  16 , reference is made to  FIGS. 6 and 7  showing rod  16  preconfigured in the shape of a healthy spine. Rod  16  is elastic or super elastic and can be made from a metal alloy, such as stainless steel, titanium or shaped memory alloy, or from a plastic such as PEEK. Rod  16  is fabricated to closely follow the contour of the spinous process of a healthy spine with no deformity. Any deformation from the original shape of the corrective rod  16  will result in a corrective force being applied. To generate a larger corrective force, these rods can be made larger or can be fabricated from a material with a higher modulus of elasticity or any combination thereof. Conversely, to generate a smaller corrective force, rod  16  can be made smaller or fabricated from a material with a lower modulus of elasticity or any combination thereof. Corrective rod  16  is also designed so that the spine will be free to move naturally without plastic deformation. As alternative embodiments, corrective rod  16  can generate forces sufficient to immediately reduce spinal deformity or can be sized to generate a force that is not sufficient to instantly reduce a deformity, but which will direct the spine back to a correct form over time, such as shown in  FIGS. 6 and 7 . 
         [0027]    An alternative to the clamp of  FIGS. 2 and 4  is shown in  FIGS. 5 and 8 . Specifically, clamp  50  is composed of two implantable clamping plates  51  and  52  which can be made from a metal alloy, such as stainless steel or titanium, or a plastic such as PEEK. These plates are secured onto the spinous process through the use of screws  55  which, together, act to generate a clamping force on the spinous process. 
         [0028]    In installing clamp  50 , a practitioner will position clamping plates  51  and  52  along the spinous process and generate pilot holes through tapped openings intended to receive threaded screws  55 . Plates  51  and  52  are then screwed together and onto the spinous process and tightened to generate the appropriate fixation force enhanced by providing, as an optional expedient, spikes  56 . 
         [0029]    As was the case with clamp  14 , plates  51  and  52  are provided with rod carriers  53  and  54  fabricated from a metal alloy such as titanium or stainless steel, or a plastic such as PEEK. 
         [0030]    In a first embodiment, rod carriers  53  and  54  can be completely constrained to their respective clamping plates and thus not capable of rotational movement thereon. In a second embodiment, however, rod carriers  53  and  54  can be made free to rotate about their axial shafts  53   a  and  54   a.    
         [0031]    Rod carriers  53  and  54  are configured to constrain rods  16  and  17  either partially or completely and to promote the transfer of corrective forces exerted by these rods to the vertebrae through clamping plates  51  and  52  and spinous process. As noted, in a first embodiment, corrective rods  16  and  17  are partially constrained and free to translate axially through rod carriers  53  and  54 . In a second embodiment, corrective rods  16  and  17  are completely restrained to rod carriers  53  and  54 . An example of such constraint is shown in  FIG. 10  whereby set screw  90  is shown passing through rod carrier  53  to constrain rod  16 . Constraint can also be facilitated by other means such as by crimping rod carrier  53  onto rod  16  or, for that matter, by any other means which would be well appreciated by anyone skilled in this art. In this regard, as previously noted, rod  16  can be shaped to provide a reduced bending moment in one direction then another ( FIG. 3 ) and movement constrain can be facilitated by sizing the opening within rod carriers  53  and  54  with regard to this non-circular cross section. 
         [0032]    As noted previously, the present invention contemplates, as one of its embodiments, the ability of corrective rods  16  and  17  to freely translate axially through rod carriers  53  and  54  or in openings  21  and  21   a.  In doing so, however, a constraint must be placed on the unlimited motion of these rods so that they do not slide out from carriers or openings in the clamps and, in this regard, reference is made to  FIG. 4 . Specifically, end cap  19  can be provided at one or both terminal ends of rod  16  preventing rod  16  from inadvertently slipping from within opening  21 . Again, an alternative constraint can be carried out by providing said screw  90  through a rod carrier, the latter completely constraining motion of rod  16  within the rod carrier ( FIG. 10 ). When said screw  90  is employed, it is suggested that clamp  14  be selected as one close to the mid point of the instrumented region such that the relative displacement of the rod carriers on the corrective rod at extreme ends of the instrumented region is minimized during flexion and extension of the spine. As an alternative, one could select a vertebrae at the superior or inferior end of the instrumented region to carry out such constraint. 
         [0033]    As a preferred embodiment, reference is made to  FIG. 11 . As background, it is recognized that as one moves his or her back into flexion, the spinous processes move apart. Ultimately this means that any correction rods should be longer than the original distance between the end points of the instrumentation constituting the present invention. 
         [0034]    The embodiment of  FIG. 11  is based upon the notion that in large-scale deformities with fixation along the spinous process, the difference in resting length and full-flexion is significant. One alternative, which cannot be adopted for obvious reasons, is to provide an extended length of correction rod extending way up and way down along a user&#39;s back. The more preferred alternative to which the  FIG. 11  embodiment addresses is to “piggyback” corrective rods  61  and  62 . Specifically, rod  62  is fixedly secured to fixture  63  by any common means such as by crimping or by set screw (not shown). However, rod  61  is free to slide in and out of fixture  63  noting that end caps will keep rod  61  from extending so far out of fixture  63  that engagement is lost. With this embodiment, one can distribute the excess length necessary for full flexion along the construct. Ideally, fixture  63  would be situated between clamps. It is further noted that fixture  63  could be replaced with a simple sheath that would fit about both rods  61  and  62  while performing the recited function. 
         [0035]    In summary, the improvements in spinal deformity correction employing the present invention are manifest. Such correction, unlike the prior art, can be carried out with minimally invasive surgery while avoiding spinal fusion and the consequent physiological impairment resulting there from.