Abstract:
A spinal implant ( 200 ) including first spinal attachment member ( 201 ) for attaching to a first spinal portion, second spinal attachment member ( 202 ) for attaching to a second spinal portion, and a post-implantation variable dimension rod 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 
     This application claims priority under 35 USC §119 to U.S. Provisional Patent Application, Ser. No. 61/272969, filed Nov. 25, 2009. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to spinal implants and prostheses, and particularly to a spinal fusion cage having a post-operative adjustable dimensions. 
     BACKGROUND OF THE INVENTION 
     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 . 
     A 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 . Post-implantation variable dimension device  22  includes a post arranged for linear motion, such as by means of a miniature linear actuator which is remote controlled. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide an improved spinal rod (or implant, or prosthesis, the terms being used interchangeably) having a post-operative adjustable dimensions, to be placed between two adjacent vertebras, with the ability to adjust the distance between the vertebras. 
     In one embodiment, at least one of its dimensions of the spinal implant can be modified post-implantation by means of remote control. 
     The adjustment of the length of the spinal rod, can be electrically powered, such as by an electric motor (powered by a battery or remote induction), and controlled via remote control. 
     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 pedicles. 
     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 rod 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. 
     In accordance with an embodiment of the present invention the first and second spinal attachment members include pedicle screws. 
     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. 
     In accordance with an embodiment of the present invention the post-implantation variable dimension device is connected to mechanical elements connected to rods attached to the pedicle screws. 
     In accordance with an embodiment of the present invention the post operative adjusted rod includes a rotating element having at least one internal thread and at least one shaft engaged with this thread. The rotating element and the shaft are disposed between the attachment members such that when the rotating element is turned the shaft moves in or out, thereby changing the distance of first attachment member from the second attachment member. 
     In accordance with an embodiment of the present invention the rotating element has two threads in two different directions, left and right, and two threaded shafts are engaged in these threads. 
     In accordance with an embodiment of the present invention the post-implantation variable dimension rod is hydraulically or pneumatically operated. 
     In accordance with an embodiment of the present invention the post-implantation variable dimension device is electrically operated. 
     In accordance with an embodiment of the present invention the post-implantation variable dimension rod 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. 
     In accordance with an embodiment of the present invention the post-implantation variable dimension rod 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 
       The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
         FIG. 1  is a simplified pictorial illustration of a prior art spinal implant including a post-implantation variable dimension device, connected to pedicle screws so that actuating the variable dimension mechanism can change the distance between the screws; 
         FIG. 2  is a simplified semi-cross section pictorial illustration of a spinal implant including a post-implantation variable dimension rod, constructed and operative in accordance with an embodiment of the invention; 
         FIG. 3  is a simplified pictorial illustration of one arrangement of rods and pedicle screws, including a post-implantation variable dimension rod, constructed and operative in accordance with an embodiment of the invention; 
         FIG. 4  is a simplified pictorial illustration of an arrangement of rods and pedicle screws, including a post-implantation variable dimension rod, constructed and operative in accordance with another embodiment of the invention; 
         FIG. 5  is a simplified pictorial illustration of an arrangement of rods and pedicle screws, including a post-implantation variable dimension rod, constructed and operative in accordance with yet another embodiment of the invention; and 
         FIG. 6  is a simplified pictorial illustration of an arrangement of rods and pedicle screws, including a post-implantation variable dimension rod, constructed and operative in accordance with still another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Reference is now made to  FIG. 2 , which illustrates a spinal implant  200 , constructed and operative in accordance with a non-limiting embodiment of the invention. 
     Spinal implant  200  includes a first (e.g., upper) rod  201  and a second (e.g., lower) rod  202  both threadingly received in a sleeve  203  mounted in a housing  209 . The threaded connection between sleeve  203  and first rod  201  is opposite in direction to the threaded connection between sleeve  203  and second rod  202 ; one is right-handed, the other left-handed. In this manner, rotating sleeve  203  in one direction (e.g., clockwise) causes the rods to move apart whereas rotating sleeve  203  in the opposite direction causes the rods to move towards each other, when the rods are connected to different spinal structure. (The term “spinal structure” encompasses not just anatomical parts of the spine, but also spinal mounting structure, such as, but not limited to, cross-connector rods or pedicle screws and the like). Sleeve  203  may be journaled in bearings  217  in housing  209 . 
     Both first and second rods  201  and  202  each have mounting structure  215  (e.g., mounting holes or lugs) at distal ends thereof for attaching to spinal structure. 
     A gear  204  is connected to, or can be part of, the outer contour of sleeve  203 . A gear train  205  is disposed between gear  204  and an actuating motor  206 . In accordance with an embodiment of the present invention the gear system  204 - 205  can be a spur gear, worm gear, belt, chain or other known mechanisms to transmit motion. Actuating motor  206  rotates sleeve  203  through a pre-designed gear ratio and rods  201  and  202  move with respect to one other. Motor  206  can be controlled by a printed circuit  208 , which may include, without limitation, at least one of a micro-controller, radio system, remote switch, capacitor, and induction coil. The power source to activate the motor can be a battery  207 . The electrical components may be controlled by an external unit via remote control (radio, light, voice etc). 
     Alternatively, as shown in the embodiment of  FIG. 6 , second rod  202  does not have to be moved by the actuating motor. Instead, second rod  202  can be attached to, or part of, housing  209 . The actuating motor moves first rod  201  towards or away from second rod  202 . 
     Instead of being electrically actuated, actuating motor  206  can be hydraulic or pneumatic, and this option is illustrated in  FIG. 6 . Actuating motor  206  includes a fluid-operated (hydraulic or pneumatic) piston  220  operated by a fluid (hydraulic or pneumatic) pump  222 , connected thereto by a tube  224 . 
       FIG. 6  also shows the option that at least one of the rods  201  or  202  may be connected directly to a bone (e.g., pedicle) screw  225  inserted at mounting structure  215 . 
     Reference is now made to  FIG. 3 , which illustrates one option of connecting the post operative adjustable rods  201  and  202 , as described in  FIG. 2 , to spinal structure. 
     In this illustrated embodiment, the spinal structure includes a first vertebral body  301  and three other vertebral bodies below body  301 , labeled  301 A,  301 B and  301 C. Two pedicle screws  302  are inserted in each vertebral body. An intervertebral rod  303  connects pedicle screws of adjacent vertebral bodies  301  and  301 A, as well as  301 B and  301 C. There are thus four rods shown. Different types of bone screws, inserted in different locations into the vertebra, can be used. 
     First rod  201  of spinal implant  200  is connected to a first attachment member  304  and a second attachment member  305  is attached to second rod  202  via attachment junctions  307  placed at mounting structures  215 . The attachment junctions  307  between the rods and the attachment members may include, without limitation, a rotatable hinge, a spherical joint, a fixed rigid attachment or any other way known to those skilled in the art. First and second attachment members  304  and  305  are connected to intervertebral rods  303  between adjacent vertebral bodies. 
     Reference is now made to  FIG. 4 , which illustrates another option of connecting the post operative adjustable rods to spinal structure. In this embodiment, first and second rods  201  and  202  of spinal implant  200  are connected to first and second ends of adjacent intervertebral rods  303  via attachment junctions  307 . 
     Reference is now made to  FIG. 5 , which illustrates yet another option of connecting the post operative adjustable rods to spinal structure. In this embodiment, first and second rods  201  and  202  of spinal implant  200  are connected to first and second cross-connector rods  503  with link members  504  via attachment junctions  307 . The cross-connector rods  503  are connected to left and right intervertebral rods  303  via attachment junctions  307 . 
     It is noted that in  FIGS. 3-6  only one post operative variable dimension spinal implant  200  is shown. However, more than one implant can be used in the same segment (e.g. between L 4  and L 5 ) or above and below the segments. 
     The embodiments of  FIGS. 3-6  can be interchanged and/or integrated with one another in different combinations.