Abstract:
A spinal implant ( 40 ) including first spinal attachment member ( 44 ) for attaching to a first spinal portion ( 41 ), second spinal attachment member ( 46 ) for attaching to a second spinal portion ( 42 ), and a post-implantation variable dimension device disposed between the first and second spinal attachment members, which is operable after completing surgery in which said spinal implant was installed into a patient, to cause relative movement between the first and second spinal attachment members.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority benefit from U.S. patent application Ser. No. 11/937,019, filed Nov. 8, 2007, and incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to spinal implants and prostheses, and particularly to a spinal implant having a post-operative adjustable dimension. 
       BACKGROUND OF THE INVENTION 
       [0003]    Spinal stenosis, as well as spondylosis, spondylolisthesis, osteoarthritis, scoliosis and other degenerative phenomena may be the cause of back pain, and may be caused by a narrowing of the spinal canal or foramina that result in stress acting on the spinal cord and/or nerve roots. 
         [0004]    One of the methods for resolving back pain involves decompression, the removal of bony elements causing the pain, and fusion of two or more adjacent vertebrae. Unfortunately, fusion tends to have significant shortcoming and may cause the problem to migrate to adjacent vertebral components. Among the non-fusion solutions are disc replacement, dynamic stabilization systems and inter-spinous process implants. 
         [0005]    Spinal implants with the capability of height adjustment are known. For example, U.S. Pat. Nos. 6,045,579, 6,080,193 and 6,576,016 to Hochshuler et at (issued Apr. 4, 2000, Jun. 27, 2000 and Jun. 10, 2003, respectively) describe an adjustable height fusion device for promoting a spinal fusion between neighboring vertebrae. The device is located within the intervertebral disc space and includes a pair of engaging plates for contacting the vertebrae. An alignment device is used to alter the vertical distance between the engaging plates to customize the apparatus to fit a given patient. In one embodiment, the alignment device includes a pair of struts having a predetermined height and extending between the engaging plates from an anterior end to a posterior end of the apparatus. In another embodiment, the alignment device includes a rotatable connector and cam pins for adjusting the distance between the engaging plates. The alignment device is preferably adapted to vary the distance between the engaging plates such that the height of the apparatus proximate the anterior end is greater than that proximate the posterior end whereby the natural lordosis of the spine is maintained after the apparatus is installed. 
         [0006]    However, these prior art devices must be adjusted prior to or during the installation and are not capable of post-operative adjustment. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention seeks to provide an improved spinal implant (or prosthesis, the terms being used interchangeably) having a post-operative adjustable dimension, such as an inter-spinous process spinal implant, as described in more detail further below. 
         [0008]    In one embodiment, at least one of its dimensions of the spinal implant can be modified post-implantation by means of remote control or a mechanical feature that can be connected to an adjustable portion of the implant, such as via a small puncture in the soft tissues. In one example, the adjustable portion (also referred to as a variable dimension mechanism) can have a piston-like configuration hydraulically or pneumatically activated by a small pressure tube. Other mechanical devices may be used and deployed, such as but not limited to, by a shaft, cable or other mechanical features. In another example, the adjustable portion can be electrically powered, such as by an electric motor (powered by electric cord, battery or remote induction), and controlled via remote control. 
         [0009]    The prosthesis is configured to bridge between two vertebrae, most preferably but not limited to, adjacent vertebrae. The prosthesis includes a plurality of attachment members (end features) configured to be attached to a plurality of bone attachment points, such as but not limited to, spinous process, vertebral end plates or pedicles (via pedicle screws). 
         [0010]    There is thus provided in accordance with a non-limiting embodiment of the present invention a spinal implant including first spinal attachment member for attaching to a first spinal portion, second spinal attachment member for attaching to a second spinal portion, and a post-implantation variable dimension device disposed between the first and second spinal attachment members, which is operable after completing surgery in which said spinal implant was installed into a patient, to cause relative movement between the first and second spinal attachment members. 
         [0011]    In accordance with an embodiment of the present invention the first and second spinal attachment members include pedicle screws. 
         [0012]    In accordance with an embodiment of the present invention the post-implantation variable dimension device changes a distance between the first and second spinal attachment members. 
         [0013]    In accordance with an embodiment of the present invention the post-implantation variable dimension device changes a location of the first and second spinal attachment members both in vertical and sagittal planes. 
         [0014]    In accordance with an embodiment of the present invention the first and second spinal attachment members include first and second support plates fitted with threaded shafts which are turned by a gear train, wherein rotation of the gear train changes a distance between the first and second support plates. 
         [0015]    In accordance with an embodiment of the present invention the first and second spinal attachment members include first and second support plates inclined with respect to each other. 
         [0016]    In accordance with an embodiment of the present invention the post-implantation variable dimension device is hydraulically or pneumatically operated. 
         [0017]    In accordance with an embodiment of the present invention the post-implantation variable dimension device includes hinged arms which are pivotally connected to and moved by a screw mechanism. 
         [0018]    In accordance with an embodiment of the present invention the post-implantation variable dimension device is electrically operated. 
         [0019]    In accordance with an embodiment of the present invention the post-implantation variable dimension device includes an internal, implanted portion. The internal portion may include at least one of an electrical piston, an electric motor, a microprocessor, an RF emitter/transmitter, an LVDT, a strain sensor, an electric coil, a battery, and a capacitor. 
         [0020]    In accordance with an embodiment of the present invention the post-implantation variable dimension device includes an external control portion. The external control portion may include at least one of a control panel, a processor, an RF transmitter/emitter, a magnetic power source, an electric coil and a cellular communication device. The communication between the external control portion and the implanted portion may be controlled by a code or password to protect against undesired operation of the internal device. 
         [0021]    In accordance with an embodiment of the present invention the post-implantation variable dimension device is inflatable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
           [0023]      FIG. 1  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with an embodiment of the invention, implanted between two adjacent spinous processes; 
           [0024]      FIG. 2  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with another embodiment of the invention, connected to pedicle screws so that actuating the variable dimension mechanism can change the distance between the screws; 
           [0025]      FIG. 3  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with yet another embodiment of the invention, inserted in between two adjacent vertebrae; 
           [0026]      FIG. 4  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with still another embodiment of the invention, used to create an optimal distraction between two adjacent spinous processes; 
           [0027]      FIG. 5  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with yet another embodiment of the invention, used to change the location of adjacent vertebrae; 
           [0028]      FIG. 6  is a simplified pictorial illustration of a hydraulically or pneumatically operated post-implantation variable dimension device, constructed and operative in accordance with an embodiment of the invention; 
           [0029]      FIG. 7  is a simplified pictorial illustration of a mechanically operated post-implantation variable dimension device, constructed and operative in accordance with an embodiment of the invention; 
           [0030]      FIG. 8  is a simplified pictorial illustration of an electrically operated post-implantation variable dimension device, constructed and operative in accordance with an embodiment of the invention; 
           [0031]      FIG. 9  is a simplified pictorial illustration of an inflatable post-implantation variable dimension device, constructed and operative in accordance with an embodiment of the invention; 
           [0032]      FIG. 10  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with still another embodiment of the invention, used to create an optimal distraction between two adjacent spinous processes using two bilateral, identically threaded lifting screws; 
           [0033]      FIG. 11  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with yet another embodiment of the invention, used to create an optimal distraction between two adjacent spinous processes using two bilateral right handed and left handed lifting screws; 
           [0034]      FIG. 12  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with still another embodiment of the invention, used to create an optimal distraction between two adjacent spinous processes using multiple concentric lifting screws; 
           [0035]      FIG. 13  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with yet another embodiment of the invention, used to create an optimal distraction between two adjacent spinous processes using two bilateral identically threaded lifting screws with electric motor and gear train; and 
           [0036]      FIG. 14  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0037]    Reference is now made to  FIG. 1 , which illustrates a spinal implant  10 , constructed and operative in accordance with an embodiment of the invention. 
         [0038]    Spinal implant  10  is shown implanted between two adjacent spinous processes of the lumbar spine (in this example, spinal implant  10  is an interspinous process device). Spinal implant  10  includes a post-implantation variable dimension device  12  disposed between a first (upper) support end plate (spinal attachment member)  14  and a second (lower) support end plate (spinal attachment member)  16 . The post-implantation variable dimension device  12  may include a post arranged for linear motion (slightly tilted from vertical in the sense of the drawing), such as by means of a miniature linear actuator which is remote controlled. In general, post-implantation variable dimension device  12  may be constructed in accordance with any of the embodiments described below with reference to  FIGS. 6-9 . 
         [0039]    Reference is now made to  FIG. 2 , which illustrates a spinal implant  20 , constructed and operative in accordance with another embodiment of the invention. Spinal implant  20  includes a post-implantation variable dimension device  22 , and is connected to pedicle screws  24  (spinal attachment members  24 ). Actuation of variable dimension device  22  changes the distance between screws  24 . Here too, post-implantation variable dimension device  22  may include a post arranged for linear motion, such as by means of a miniature linear actuator which is remote controlled. In general, post-implantation variable dimension device  22  may be constructed in accordance with any of the embodiments described below with reference to  FIGS. 6-9 . 
         [0040]    Reference is now made to  FIG. 3 , which illustrates a spinal implant  30  including a post-implantation variable dimension device  32 , constructed and operative in accordance with yet another embodiment of the invention, inserted in between two adjacent vertebrae (e.g., L 4  and L 5 ). Spinal implant  30  includes a first (upper) support plate  34  connected to and supporting an upper vertebra, and a second (lower) support plate  36  connected to and supporting a lower vertebra. The variable dimension device  32  is installed between first and second support plates (spinal attachment members)  34  and  36 . Actuation of variable dimension device  32  changes the distance between first and second support plates  34  and  36 , and can change the location between the two adjacent vertebrae both in the vertical and the sagittal planes. The post-implantation variable dimension device  32  may be constructed in accordance with the embodiment described below with reference to  FIG. 5 . 
         [0041]    Reference is now made to  FIG. 4 , which illustrates a spinal implant  40  including a post-implantation variable dimension device  42 , constructed and operative in accordance with still another embodiment of the invention. Implant  40  can be used to create an optimal distraction between two adjacent spinous processes, such as the superior spinous process  41  and inferior spinous process  43 . 
         [0042]    Spinal implant  40  includes first and second support plates (spinal attachment member)  44  and  46  that respectively support the superior spinous process  41  and inferior spinous process  43 . First and second support plates  44  and  46  are each tapped with threaded holes to accept threaded shafts  45 L and  45 R, and  47 L and  47 R, respectively. Threaded shafts  45 L and  47 L have left-handed threads, while threaded shafts  45 R and  47 R have right-handed threads. 
         [0043]    Gear pulleys  48 A and  48 B are connected to threaded shafts  45 L,  45 R,  47 L and  47 R, and are driven by a worm gear  49 . Rotation of worm gear  49  changes the distance between first and second support plates  44  and  46  and the supported spinous processes. 
         [0044]    Reference is now made to  FIG. 5 , which illustrates a spinal implant  50  including a post-implantation variable dimension device  52 , constructed and operative in accordance with yet another embodiment of the invention. 
         [0045]    Spinal implant  50  may be used to change the location of adjacent vertebrae  51  and  53 . Spinal implant  50  includes a first (upper) support plate  54  having a threaded slot in which a threaded screw  55  is threadedly received. Spinal implant  50  includes a second (lower) support plate  56  that includes a recess in which an electrical motor (or actuator)  57  is mounted. The electrical motor  57  (which may be remote controlled) turns screw  55 , which causes first support plate  54  to slide with respect to second support plate  56 . The inclined mating between first and second support plates (spinal attachment members)  54  and  56  causes a change in the adjacent location between the two vertebras, both in the vertical and the sagittal planes. 
         [0046]    Reference is now made to  FIG. 6 , which illustrates a hydraulically or pneumatically operated post-implantation variable dimension device  60 , constructed and operative in accordance with an embodiment of the invention. Variable dimension device  60  includes two end plates (spinal attachment members)  61  and  62 , both attached to a piston  63 . Piston  63  is fluidly actuated (that is, either hydraulically or pneumatically), such as by means of compressed liquid (e.g., water) or gas (e.g., air). The compressed fluid is introduced to piston  63  by means of a tube  64  which is connected to a fluid inlet  65 . 
         [0047]    Reference is now made to  FIG. 7 , which illustrates a mechanically operated post-implantation variable dimension device  70 , constructed and operative in accordance with an embodiment of the invention. Variable dimension device  70  includes hinged arms  72  which are pivotally connected to and moved by a male/female screw mechanism  74  operated by a turn-handle  76 . 
         [0048]    Reference is now made to  FIG. 8 , which illustrates an electrically operated post-implantation variable dimension device  80 , constructed and operative in accordance with an embodiment of the invention. Variable dimension device  80  includes hinged arms  82  which are pivotally connected to and moved by an electrical piston (electrical actuator or solenoid)  84 , which may be externally operated by an inductance coil  86 . 
         [0049]    The electrically operated post-implantation variable dimension device  80  may have an internal, implanted portion and/or an external, control portion. The internal portion may include, without limitation, electrical piston  84 , an electric motor, microprocessor, RF emitter/transmitter, LVDT (linear variable differential transducer), strain sensor, electric coil for direct energy transfer into the motor from an external coil, battery, capacitor to accumulate energy, or any combination thereof. 
         [0050]    The external portion may include, without limitation, a control panel, processor, RF transmitter/emitter, magnetic power source, electric coil to transfer energy to the internal unit, or any combination thereof. The external portion may also include a cellular communication device to allow remote control by the physician. A code or password may be incorporated into the control system to prevent unwanted operation. 
         [0051]    Reference is now made to  FIG. 9 , which illustrates an inflatable post-implantation variable dimension device  90 , constructed and operative in accordance with an embodiment of the invention. Variable dimension device  90  includes an inflatable pillow or cushion  92  inflatable via a small tube  94 . 
         [0052]    Reference is now made to  FIG. 10 , which illustrates a post-implantation variable dimension device that can be placed between two adjacent spinous processes, constructed and operative in accordance with an embodiment of the invention. The variable dimension device includes a first supporting element  95  and a second supporting element  96 . Two bilateral, identically threaded (same direction of rotation) screws  97  and  98  are used to control the distance between supporting elements  95  and  96 . 
         [0053]    Reference is now made to  FIG. 11 , which illustrates a post-implantation variable dimension device that can be placed between two adjacent spinous processes, constructed and operative in accordance with another embodiment of the invention. This variable dimension device includes a first supporting element  99  and a second supporting element  100 . Two bilateral, differently threaded (e.g., right and left handed threads) screws  101  and  102  are used to control the distance between supporting elements  99  and  100 . The screws are driven by a worm gear  103 . The different threads may be used to better lock the mechanism at any given point. 
         [0054]    Reference is now made to  FIG. 12 , which illustrates a post-implantation variable dimension device that can be placed between two adjacent spinous processes, constructed and operative in accordance with another embodiment of the invention. This variable dimension device includes a first supporting element  104  and a second supporting element  105 . Two concentric screws  106  are used to control the distance between supporting elements  104  and  105 . By using multiple concentric screws, the mechanism can be rotated a greater distance than with a single central screw. 
         [0055]    Reference is now made to  FIG. 13 , which illustrates a post-implantation variable dimension device that can be placed between two adjacent spinous processes, constructed and operative in accordance with another embodiment of the invention. This variable dimension device includes a first supporting element  107  and a second supporting element  108 . Two bilateral, identically threaded screws  110  are used to control the distance between supporting elements  107  and  108 . The lifting screws are driven by a gear train  111  activated by an electric motor  109 . 
         [0056]    Thus, in the embodiments of  FIGS. 10-13 , the spinal implant can be located between two adjacent spinous processes such that the inferior spinous process is supported by a first element of the implant and the superior spinous process is supported by a second element of the implant. The two supporting elements are separated from each other along a generally horizontal plane, and a mechanical or electro-mechanical mechanism can control the distance between the two supporting elements. 
         [0057]    Another option of any of the embodiments of the invention is shown in  FIG. 13 . The spinal implant can include a processor  120  and sensor  122  that control the post-implantation variable dimension device as a function of a load applied on, or a distance between, the first and second spinal attachment members. The post-implantation variable dimension device can be programmable to be activated at any desired time interval for any desired load and travel limits. For conserving power, the post-implantation variable dimension device can include circuitry  124  for operating in a sleep mode. The post-implantation variable dimension device may be powered by a rechargeable battery  126  that is chargeable using remote energy transfer. 
         [0058]    The present invention may also be used for scoliosis correction that includes on-going adjustment, without a need for repeated surgical intervention or for fusion. 
         [0059]    For example, reference is now made to  FIG. 14 , which illustrates a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with another embodiment of the invention. 
         [0060]    The device includes a bone screw  210  that may be curved as part of, or rigidly attached to, a housing  211 . A cable or wire  218  protrudes out of housing  211 . The cable  218  is mounted over a roller  216 . Roller  216  is connected to a screw  215  that can be moved linearly by rotating a gear  214  that meshes with screw  215 . An electrical motor  212  powers a gear train  213  that controls the rotation of gear  214  and thus also the linear motion of screw  215  and the cable  218 . 
         [0061]    The design allows pulling or releasing cable  218  by operating the electrical motor  212  to different directions, at any given time after the implantation. 
         [0062]    The embodiment of  FIG. 14  can be inserted into the pedicles of the spinal vertebra or, alternatively, to the lateral side of the vertebra. Cable or wire  218  protruding from the side of the implant can be connected, using various different methods, to the adjacent implant or to another anchor, inserted into other vertebrae. When the cable or wire  218  is pulled by the abovementioned mechanism, the two vertebrae will be forced on to each other. 
         [0063]    It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of the features described hereinabove as well as modifications and variations thereof which would occur to a person of skill in the art upon reading the foregoing description and which are not in the prior art.