Abstract:
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.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to spinal implants and prostheses, and particularly to a spinal fusion cage having post-operative adjustable dimensions. 
       BACKGROUND OF THE INVENTION 
       [0002]    Spinal implants with the capability of height adjustment are known. One device is shown and described in PCT Patent Application PCT/IL2008/001423 (WO 2009/060427), to the present applicant. One of the devices shown therein uses an inclined, threaded interface between first and second support plates, as is now described with reference to  FIG. 1 . 
         [0003]    The prior art device is a spinal implant  50  that includes a post-implantation variable dimension device  52 , 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. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention seeks to provide an improved spinal implant (or prosthesis, the terms being used interchangeably) having post-operative adjustable dimensions, to be placed between two adjacent vertebras, with the ability to adjust both the height between the vertebras and also the sagittal position of one in respect to the other. In contradistinction to the above prior art, in the present invention, the inclined interface is not threaded; rather the vertebral attachment members slide over each other by means of inclined alignment rails. 
         [0005]    In one embodiment, at least one of the dimensions of the spinal implant can be modified post-implantation by means of remote control. The adjustable mechanism (also referred to as a variable dimension mechanism) can have an inclined alignment rail. The adjustment of the height and sagittal location of the parts of the cage, in respect to each other, can be electrically powered, such as by an electric motor (powered by a battery or remote induction), and controlled via remote control. 
         [0006]    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, vertebral end plates. 
         [0007]    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. 
         [0008]    In accordance with an embodiment of the present invention the first and second spinal attachment members include an inclined alignment rail. 
         [0009]    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. 
         [0010]    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. 
         [0011]    In accordance with an embodiment of the present invention the first spinal attachment members include a slot (channel) and a pulling element disposed in this slot pulls or pushes this first attachment member in respect to the second attachment member. 
         [0012]    In accordance with an embodiment of the present invention the pulling element is actuated by a threaded shaft which is turned by a gear train, wherein rotation of the gear train changes the distance between the first and second support plates. 
         [0013]    In accordance with an embodiment of the present invention the first and second spinal attachment members include first and second alignment rails inclined with respect to each other. 
         [0014]    In accordance with an embodiment of the present invention the post-implantation variable dimension device is hydraulically or pneumatically operated. 
         [0015]    In accordance with an embodiment of the present invention the post-implantation variable dimension device is electrically operated. 
         [0016]    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 a piston, a pump, a microprocessor, an RF emitter/transmitter, an LVDT (linear variable differential transducer), a strain sensor, an electric coil, a battery, and a capacitor. 
         [0017]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
           [0019]      FIG. 1  is a simplified pictorial illustration of a spinal implant including a post-implantation variable dimension device of the prior art; 
           [0020]      FIG. 2  is a simplified, partially cross-sectional illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with an embodiment of the invention; 
           [0021]      FIG. 3  is a simplified pictorial illustration of inclined alignment rails of the device of  FIG. 2 , in accordance with an embodiment of the invention; 
           [0022]      FIG. 4  is a simplified illustration of a spinal implant including a post-implantation variable dimension device, constructed and operative in accordance with another embodiment of the invention; 
           [0023]      FIG. 5  is a simplified illustration of a spinal implant including a post-implantation variable dimension device constructed and operative in accordance with still another embodiment of the present invention; and 
           [0024]      FIG. 6  is a simplified illustration of a fluid-actuated piston in the configuration of the embodiment of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0025]    Reference is now made to  FIG. 2 , which illustrates a spinal implant  100 , constructed and operative in accordance with a non-limiting embodiment of the invention. 
         [0026]    Spinal implant  100  is shown implanted between two adjacent vertebras  101  and  102 . Spinal implant  100  includes a first (e.g., upper) spinal attachment member  104  arranged for sliding over a second (e.g., lower) spinal attachment member  103 . More specifically, first and second attachment members  104  and  103  include at least one inclined alignment rail  110  that slides over at least one inclined channel  109  (the rail or rails are formed in one of the attachment members and the channel or channels are formed in the other attachment member). (The rails and channels are not visible in the section of  FIG. 2 , but an example of them is shown in  FIG. 3 ). The first attachment member  104  slides over the second attachment member  103  by being pulled or pushed by a pulling element  107 . The first and second attachment members  104  and  103  form a spinal fusion cage having post-operative adjustable dimensions. 
         [0027]    Surfaces of the attachment members in contact with bone may be coated to promote osseous integration. 
         [0028]    In accordance with a non-limiting embodiment of the invention, pulling element  107  includes a distal tongue  111  that is received in a recess  112  formed in first attachment member  104 . A proximal end  113  of pulling element  107  is internally threaded to mate with a threaded rod  105  (also called screw  105 ). First attachment member  104  is sufficiently hollow to allow threaded rod  105  to enter and advance into first attachment member  104 . 
         [0029]    The threaded rod  105  can be rotated by a gear system  108 , actuated by a gear train powered by an actuating motor, not shown here but shown in  FIG. 4 . A seal  106  can be disposed between components located in a closed compartment and elements exposed to the human body. 
         [0030]    In accordance with a non-limiting embodiment of the present invention, pulling element  107  and threaded rod  105  are disposed completely or partially in attachment member  103 . A bearing element, such as any kind of bearing, lubrication, surface treatment and the like, can be used to reduce the friction between the pulling element  107  and/or threaded rod  105  and attachment members  103  and/or  104 . 
         [0031]    In accordance with an embodiment of the present invention the gear system  108  can be spur gear, worm gear, belt, chain or other known mechanisms to transmit motion. 
         [0032]    Reference is now made to  FIG. 3 , which illustrates inclined alignment rails  110 , in accordance with a non-limiting embodiment of the invention. The alignment rails  110  can have a predesigned angle to create different relations between the sagittal and the vertical translations. The at least one alignment rail  110  can be located symmetrically about the center of the device or not symmetrically about the center (e.g., off-center). The sliding surface of channels  109  may include a bearing element  117 , such as any kind of bearing, lubrication, surface treatment and the like, to reduce friction. 
         [0033]    The illustrated embodiment shows the at least one alignment rail  110  with a generally rectangular shape; however, different contours can be used as well to carry out the invention, such as but not including, dove tail, rounded shape, T shape or any other shapes. 
         [0034]    Reference is now made to  FIG. 4 , which illustrates a cross section of a spinal implant including a post-implantation variable dimension device constructed and operative in accordance with an embodiment of the present invention. 
         [0035]    A pulling element  305  is pulled by a threaded rod  304 . Threaded rod  304  is connected to a gear train  309 , powered by an actuating motor  303 . A battery  306  and a printed circuit  307  are used to control the motor  303 . A seal  308  is used to separate between encapsulated elements and the human body, not shown. 
         [0036]    In accordance with an embodiment of the present invention, printed circuit  307  can include at least one of a micro-controller, a radio system, a remote switch, a capacitor, and an induction coil. The electrical components may be controlled by an external unit via remote control (radio, light, voice etc). Instead of being electrically actuated, actuating motor  303  can be hydraulic or pneumatic. 
         [0037]    Reference is now made to  FIG. 5 , which illustrates a cross section of a spinal implant including a post-implantation variable dimension device constructed and operative in accordance with another embodiment of the present invention. In this embodiment, the pulling element includes a piston  320  with a rod  321 . A tongue  322  at a distal end of rod  321  is received in a recess  323  formed in first attachment member  104 . Piston  320  may be electrically, pneumatically or hydraulically (i.e., fluidly) operated. 
         [0038]      FIG. 6  illustrates an example of a hydraulic or pneumatic piston  320  in the configuration of the embodiment of  FIG. 4 . The pulling element  305  is at the distal end of rod  321 . Piston  320  is operated by a pneumatic or hydraulic (i.e., fluid) pump  324 , connected thereto by a tube  325 . 
         [0039]    The embodiments of  FIGS. 2-6  can be interchanged and/or integrated with one another in different combinations.