Abstract:
Disclosed is an instrument to assist in installing bottom loading orthopedic devices. The orthopedic devices are used to fix and stabilize bones to correct anomalies in skeletal structure occurring naturally or by trauma. Bone screws are anchored and tulips by the disclosed instrument wherein push/pull forces are equalized to eliminate the imposition of stress on the skeletal of individual.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application is related to U.S. patent application Ser. No. 14/643,448, the contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     This invention relates to orthopedic surgery and, in particular, to an instrument for securing a modular head assembly. 
     BACKGROUND OF THE INVENTION 
     Chronic back problems are caused by intervertebral disc disease and deterioration and loss of stability of the intervertebral joints. Examples of these spinal conditions include degenerative disc disease, scoliosis, spondylolisthesis, spinal stenosis, etc. Stabilization and/or arthrodesis of the intervertebral joint can reduce the pain associated with movement of a diseased or deteriorated intervertebral joint. In order to allow for development of a solid intervertebral fusion, the spine has to be stabilized. Severe trauma to the back can further cause conditions wherein the spine needs to be stabilized. There are many instances in which it is necessary to stabilize and fix bones and bone fragments in a particular spatial relationship to correct the location of skeletal components due to injury or disease. One group of devices employ a number of bone screws placed across a discontinuity in adjacent vertebrae and connected by a rod to maintain a predetermined spatial location. 
     Spinal stabilization systems have been developed to stabilize the vertebrae to allow for fusion or stabilization of diseased intervertebral joints. One type of spinal stabilization system includes connectors and rods that are used to stabilize the spine. Some examples of such spinal stabilization systems are disclosed in U.S. Pat. Nos. 6,613,050; 6,371,957; 6,050,997; 5,879,350; 5,725,527; 5,628,740; and 5,545,165, the disclosures of which are incorporated herein by reference. In these systems, connectors are anchored to the vertebral bodies desired to be stabilized by anchoring structures such as screws or hooks. One or more connecting rods are then secured to the connectors to form a connector/rod construct that stabilizes the vertebral bodies to which the connectors are secured. 
     The inventors implants includes U.S. Pat. Nos. 7,105,029; 7,118,303; 7,334,961; 7,335,201; 7,438,715; 7,658,582; 7,678,138; 7,862,281; 7,981,143 and RE42,715, the disclosures of which are incorporated herein by reference. In normal practice a screw and modular head are assembled in a factory before being anchored to a bone. Alternatively a screw is anchored to the bone and the modular head then secured to the screw. The modular heads, which are commonly referred to as a tulip, are then connected together by a rod having sufficient stiffness to maintain the desired skeletal orientation. The problem with mounting a tulip onto a bone screw is the pressure necessary during the installation step. Thus, what is needed in the art is an instrument to mount a tulip to an anchored bone screw wherein the instrument has a force canceling effect. 
     SUMMARY OF THE INVENTION 
     An instrument to assist in installing orthopedic devices used to fix and stabilize bones to correct anomalies in skeletal structure occurring naturally or by trauma. Bone screws are anchored into bones and a module head, commonly referred to as a tulip, is attached to the anchored bone screw by use of the instant instrument wherein push/pull forces are equalized. 
     The instrument works with bone screws that have an internal relief groove added to the shank. The instrument is first loaded with a tulip wherein grip fingers hold the tulip in a mounting position. A tip of the instrument includes a collet that protrudes through the tulip. The collet is sized for insertion into the shank of the bone screw and includes an expanding pin to expand the collet into a relief groove located in the shank thereby securing the instrument to the bone screw. In operation, a handle of the instrument is squeezed about 5° of motion for control of the expanding collet tip by pushing an expander pin forward to block the collet area from collapsing thereby locking the instrument tip on to shank. The handle is then squeezed about 20° wherein a cam controls a push sleeve which pushes on the tulip at the same time the collet pulls on the bone screw in equal force but opposite direction wherein the shank head is captured by the tulip. As the handle is squeezed about 5° further, lever handle fully cycled, the cam controlling the collet pulls the expander pin back which unblocks the collet area so that the collet tip collapses and can be removed from the shank. 
     An objective of the invention is to provide a modular head (tulip) inserter that can cancel out forces necessary when installing tulip on an anchored bone screw using a PUSH-PULL design. 
     Another objective of the invention is to provide an instrument capable of holding a tulip in position for mounting to a bone screw. 
     Still another objective of the invention is to provide a modular head inserter permitting one handed use. 
     Another objective of the invention is to provide a modular head inserter having a single stroke lever handle to capture the shank head, mount the tulip, and disengage from the bone screw. 
     Yet still objective of the invention is to provide a modular head inserter with cam type motion control. 
     Other objectives and further advantages and benefits associated with this invention will be apparent to those skilled in the art from the description, examples and claims which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of the modular head inserter; 
         FIG. 2  is a cross-sectional view thereof; 
         FIG. 3  is a right side view thereof; 
         FIG. 4  is a front view of a bone screw shank portion; 
         FIG. 5  is a top view of a bone screw; 
         FIG. 6  is a cross-sectional view of a bone screw; 
         FIG. 7  is an enlarged view of the head of a bone screw showing a radial relief grip groove; 
         FIG. 8  is an enlarged view of the head of a bone screw with a collet tip inserted and expander pin deployed; 
         FIG. 9  is a front view of the tip end of a push sleeve illustrating a modular head nest area and pinch fingers; 
         FIG. 10  is a side view of the collet tip; 
         FIG. 11  is a side view of the inserter tip fully inserted into a bone shank; 
         FIG. 12  is a cross-sectional view of the inserter tip shown with expander pin deployed; 
         FIG. 13  is a cross-sectional view of the inserter tip with push sleeve fully deployed and capturing a bone screw; 
         FIG. 14  is a cross-sectional view of the inserter tip shown with expander pin pulled back; 
         FIG. 15  is a plane view of inserted tip collapsed; 
         FIG. 16  is a plane view of an assembled modular head; 
         FIG. 17  is a plane view of the body element; 
         FIG. 18  is a cross-sectional view of  FIG. 17 ; 
         FIG. 19  is an enlarged isometric mid-section view of the body element; 
         FIG. 20  is an enlarged view of the collet; 
         FIG. 21  is an front view of the push sleeve; 
         FIG. 22  is a side view of  FIG. 21 ; 
         FIG. 23  is a cross-sectional view of  FIG. 21 ; 
         FIG. 24  is a perspective view of the expander pin; 
         FIG. 25  is a plane view of the expander pin reduced diameter end; 
         FIG. 26  is a plane view of the expander pin head; 
         FIG. 27  is a side view of the lever handle; 
         FIG. 28  is an isometric view of the lever handle; 
         FIG. 29  is an isometric view of a pivot pin; 
         FIG. 30  is a top perspective view of an end cap; 
         FIG. 31  is a bottom perspective view of the end cap; 
         FIG. 32  is a plane view of a compression spring; and 
         FIG. 33  is an isometric view of a pivot pin retainer ring. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Detailed embodiments of the instant invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific functional and structural details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representation basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
     Referring to  FIGS. 1-3 , set forth is the modular head inserter instrument  10 , having a body  12  with a lever handle  14  and push sleeve  16 . At a distal end  18  of the push sleeve  16  is a collet tip  20  used for temporary coupling to a relieve groove in a bone screw. The push sleeve  16  houses an expander pin  24  for insertion through the collet tip  20 . The collet tip  20  is driven by the expander pin head  110  that can slide within the cavity passageway  30 . The expander pin head  110  includes an aperture  114  for receipt of cam pin  31 . The cam pin  31  is operatively associated with lever handle  14  for movement of expander pin  24 . Upon movement of the lever handle  14 , the cam pin  31  travels within cam track  44  causing the expander pin  24  to extend into the collet tip  20 . To provide an equal push/pull action, the body  12  which forms the collet tip  20  is pulled back at the same time the expander pin  24  is moved. The springs  32  and  32 ′ are compressed to provide a bias against the lever handle  14  movement. The lever handle  14  operating in conjunction with cam track  44  to operate the expander pin  24  and body  12  movement. The body  12  is attached to the push sleeve  16  with attachment pin  38 . The cam track  44  is operated in conjunction with cam pin  40 , wherein the cam track  44  is pivoted along pivot pin  39  for pushing of the push sleeve  16  through cam pin  40 , while cam track  44  is operated in conjunction with cam pin  31  for pulling of the inserter pin  24 . 
     Referring to  FIGS. 4 through 8 , the shank  61  of a screw  60  includes a head  62  with a Hexalobe drive receptacle  64  used for rotation of the screw  60  for installation into a bone. Along the bottom of the receptacle  64  is a cavity  68  having a relief groove  66 . The relief groove  66  is larger than the diameter of the cavity  68  by a distance X. The relief groove  66  is sized to receive lobe  88  when the expander pin  24  causes the tip section of the collet to expand. Once the lobe  88  of the collet tip  20  is expanded into the relief groove  66 , the screw  60  is temporarily secured to the instrument. Insertion of the collet tip  20  and expansion by the expander pin  24  secures the instrument to the screw  60 , which allows a “pull” against Hexalobe drive feature of the shank head  62  while the push sleeve engages the tulip  80 . 
     The distal end  18  of the push sleeve  16  includes pinch fingers  50  and  52  to provide frictional engagement for securing a tulip  80  to the instrument during a preloading step. Referring to  FIG. 9 , the pinch fingers are formed integral to the push sleeve  16  with a width W that allows the edges of a tulip to be pinched providing a temporary securement to the instrument. The spacing between the rest area  54 ,  55  and the pinch fingers  50  and  52  is tapered to allow ease of mounting the tulip  80  to the push sleeve  16 . As the tulip  80  is being pushed onto the push sleeve  16 , the pinch fingers  50  and  52  provide an increasing tightened grip on the tulip  80 . As further illustrated in  FIGS. 10 and 11 , pinch finger  52  is illustrated capturing tulip  80 , the finger  52  providing a biasing force and frictional engagement against an edge  81  formed by the U-shaped opening of tulip  80 . The upper edge  83  of the tulip  80  is flush against a lower edge  85  of the push sleeve  16 . The tulip rest area  54  and  55  are configured to the U-shaped opening of a tulip for maintaining the tulip in position during the installation step. 
       FIG. 12  is a cross-sectional view of  FIG. 11 , further depicting the collet tip  20  within the cavity  68  of the screw  60 , with the expander pin  24  expanding the collet  20  causing the lobe  88  to fit within the relief groove  66 . The pinch fingers  50  and  52  hold the tulip  80  in position during the installation steps. Referring to  FIG. 13 , as the collet tip  20  is pulled upward, the push sleeve  16  pushes downward providing a cancelling of forces wherein attachment of the tulip  80  to the screw  60  places no pressure on the skeletal of the body. FIG. illustrates the collet tip  20  with the expander pin  24  partially withdrawn so as to collapse the collet tip  20  for removal from the cavity  68 . The tulip  80 , is a bottom loading tulip which is secured to an anchored screw  60 . 
       FIG. 15  illustrates the inserter instrument  10  removed from the tulip  80  wherein the collet tip  20  is relaxed and the expander pin  24  has been withdrawn. The collet tip  20  includes spaces  21  formed by removed material that allows for the diameter of the collet to be reduced in size when the expander pin is removed to allow for ease of inserting into a screw or removal therefrom. Further, the diameter of the collet can be expanded in diameter wherein the lobe  88  may engage the relief groove  66  when the expander pin  24  is inserted.  FIG. 20  illustrates the distal end  96  of the collet tip  20  with the spaces  98 ,  100 ,  102 , and  104  providing relief around the diameter of the collet tip  20  to allow for the expansion and contraction of the collet tip  20  based upon the position of the expander pin  24 . The spaces consist of removed material along a line parallel to a central axis of the collet. The spaces may consist of one or more to allow for expansion and contraction. The expander pin  24  being inserted into the collet tip  20  causes the expansion wherein lobe  88  will conform to the relief groove  66  of the shank head  62 . Removal of the expander pin  24  allows the collet tip  20  to collapse along the spaces providing a relief line for reducing the diameter of the collet. 
       FIG. 16  illustrates the tulip  80  attached to the head  62  of the screw  60 . In this position the screw  60  is anchored to the bone and the tulip  80  is securely attached to the screw  60 , the installation of the tulip  80  did not require any pressure being applied to the bone. The tulip  80  has a U-shaped receptacle  91  for receipt of a connecting rod, not shown, for securing to adjoining modular screw head assemblies. 
       FIG. 17  and  FIG. 18  illustrates the body element  12  formed from a unitary piece of material having the collet tip  20  formed along one end and a passageway  30  for receipt of the head of the expander pin  24 . The passageway  30  is accessed by use of access opening  29  formed at the proximal end of the body element  12 . A cap  132  is threaded to the end  33  of the access opening  29 .  FIG. 19  depicts a sectional view of the body element  12  having a first recess  90  and handle attachment element  92  and a spring receptacle  94 . The first recess  90  operates in combination with the handle attachment element  92  to maintain alignment of the push sleeve  16 . A second recess can be located on the opposite side of the body element, not shown, forms a mirror image for the handle attachment. The spring receptacle  94  houses springs  32  and  32 ′ illustrated in  FIG. 2  providing a spring bias for the movement of the lever handle  14 . 
     Referring now to  FIGS. 21-23 , illustrated is the push sleeve  16  having pinch fingers  50  and  52  abutting the relief areas  54  and  55 . Preferably the push sleeve  16  is formed from a single piece of material with the pinch fingers  50  and  52  constructed and arranged to frictionally engage a tulip  80  so as to maintain the tulip  80  in a fixed position during the installation procedure.  FIG. 22  is a side view of  FIG. 21  depicting the front rest area  54  and the rear rest area  55 . The rest areas receive the U-shaped receptacle section  91  of a tulip with the pinch fingers  50  and  52  and is spaced apart from the passageway  106  which extends the longitudinal length of the push sleeve  16  for receipt of the collet tip  20  and expander pin. 
       FIG. 24  illustrates the expander pin  24  having a pin head  110  used for expanding the tip of the collet for securing to the bone screw, or retracting the collet tip  20  for detaching the instrument from the bone screw. The expander pin  24  has a distal end with a reduced diameter section  112  which allows for the desired expanding of the collet tip  20  when required.  FIG. 25  is an enlarged view of the reduced diameter section  112  allowing for rigidity along the length of the expander pin  24  with only the reduced diameter section  112  used to engage the collet tip  20 .  FIG. 26  is an enlarged view of the expander pin head  110  having aperture  114  for engagement of a pivot pin  31 . 
       FIGS. 27 through 33  are component parts of the inserter instrument  10 .  FIG. 27  is a lever handle  14  with cam track  42  for operation of the expander pin  24  and cam track  44  for operation of the push sleeve  16 .  FIG. 28  is an isometric view of  FIG. 27  illustrating the positioning of the cam track  42 ′ for the expander pin and opposing cam track  44 ′ for receipt of an expander pin. The opposing cam track  44 ′ is used in combination with apertures  118  and  118 ′ for receipt of the pivot pin  39  to allow rotation of the lever handle  14 .  FIG. 29  illustrates pivot pin  39  for insertion into the cam track  44  to engage the expander pin  24 .  FIG. 30  is the end cap  132 , placed on the body element  12  after insertion of the expander pin  24 .  FIG. 31  is the end cap  132  placed on the body element  12  after insertion of the expander pin  24 .  FIG. 32  depicts spring  32 , the second spring  32 ′ is identical.  FIG. 33  is a retainer ring  124  that fits within the grooves  126  and  128  of the pivot pin  39 . 
     Operational steps of the instrument are as follows: First sequence of the inserter instrument  10  is to attach and load the tulip  80  by sliding the U-shaped receptacle  99  of the tulip onto the resting sections  54  and  55  of the end of the push sleeve  16  wherein the pinch fingers  50  and  52  temporarily engage the tulip  80  during the installation steps. The pinch fingers  50  and  52  are machined to create a spring/pinched effect to hold the tulip in place using frictional engagement. 
     The end of the instrument includes a collet tip  20  capable of collapsing during insertion into an anchored bone screw  60 . The collet tip  20  is expanded wherein a lobe  88  on the collet tip  20  is used to engage a relief groove  66  on the bone screw  60 . An expander pin  24  is placed in a stand-by position so to allow the insertion of the collet tip  20  into a cavity which houses the relief groove  66  formed in the head of the bone screw  60 . 
     A lever handle  14  is squeezed from 30° to the 25° (5° of motion), the cam track  44  controlling the expander pin  24  wherein the expander pin  24  is placed into a position to prevent the now expanded collet tip  20  from collapsing wherein the instrument tip is locked onto shank. 
     As the lever handle  14  is squeezed from 25° to the 5° (20° of motion), the cam track  44  pushes the push sleeve onto the shank head to the capture position while the collet tip  20  is being pulled with an equal force but in an opposite direction. The cam for the expander pin  24  is in a 20° of idle position. 
     As the lever handle  14  is squeezed from a 5° to the 0° (5° of motion—lever handle fully cycled), the cam controlling the collet tip pulls the expander pin  24  back to unblock the collet area. The collet tip  20  can then collapse and the instrument is no longer locked onto the screw. The cam controlling the push sleeve is in 5° of idle. Once completed, the surgeon simply pulls the instrument away from the screw to remove the instrument, and the captured tulip  80  remains attached to the shank head. 
     Once the tulip, modular head, is assembled to the bone screw, the assembly is no different than a convention pedicle screw assembly which requires a rod component, a set screw component, and a final tightening of the set screw. 
     All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein. 
     One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.