Abstract:
Provided is a novel surgical instrument having an adjustable distal end that can securely engage an interbody for introduction of the interbody into an intervertebral space, can be adjusted before and during the surgical procedure to vary the angle of the distal end of the device and the angle of introduction of the interbody, and after positioning that interbody at the surgical site, can be easily disengaged and removed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The present invention relates to devices and methods for use in orthopedic spine surgery. In particular, the present invention relates to a device having at least two distinct articulating surfaces, the device being useful as an artificial disc replacement and a method of implanting that device using a posterior approach.  
         [0003]     2. Background Art  
         [0004]     The human spine is comprised of thirty-three vertebrae at birth and twenty-four as a mature adult. Between each pair of vertebrae is an intervertebral disc, which maintains the space between adjacent vertebrae and acts as a cushion under compressive, bending and rotational loads and motions. A healthy intervertebral disc has a great deal of water in the nucleus pulposus—the center portion of the disc. The water content gives the nucleus a spongy quality and allows it to absorb spinal stress. Excessive pressure or injuries to the disc can cause injury to the annulus—the outer ring that holds the disc together. Generally, the annulus is the first portion of the disc that seems to be injured. These injuries are typically in the form of small tears. These tears heal by scar tissue. The scar tissue is not as strong as normal annulus tissue. Over time, as more scar tissue forms, the annulus becomes weaker. Eventually this can lead to damage of the nucleus pulposus. The nucleus begins to lose its water content due to the damage—it begins to dry up. Because of water loss, the discs lose some of their ability to act as a cushion. This can lead to even more stress on the annulus and still more tears as the cycle repeats itself. As the nucleus loses its water content it collapses, allowing the two vertebrae above and below to move closer to one another. This results in a narrowing of the disc space between the two vertebrae. As this shift occurs, the facet joints located at the back of the spine are forced to shift. This shift changes the way the facet joints work together and can cause problems in the facet joints as well.  
         [0005]     When a disc or vertebrae is damaged due to disease or injury standard practice is to remove part or all of the intervertebral disc, insert a natural or artificial disc spacer or interbody and construct an artificial structure to hold the effected vertebrae in place to achieve a spinal fusion.  
         [0006]     A major challenge of spine surgery is in the development of surgical instruments for the surgeon to use during the implantation of the devices such as an artificial disc replacement or interbody. The instrumentation must be easy to use, effective, durable and most importantly, must not interfere with or cause further damage to the patient&#39;s anatomy.  
         [0007]     There is a particular need to provide a specifically designed surgical instrument that can safely be used in the process of implanting a disc spacer or interbody between adjacent vertebrae and then easily disengage the instrument from the implanted interbody.  
       SUMMARY OF THE DISCLOSURE  
       [0008]     The present invention meets the above identified need by providing a novel surgical instrument device that effectively engages an interbody for introduction of the interbody into an intervertebral space and after positioning that interbody can be easily disengaged and removed from the surgical site.  
         [0009]     Also provided is a device having an adjustable angle distal end for introducing an interbody into an intervertebral space wherein the distal end of the device is provided with an interbody grasping unit that can securely grasp the interbody for the process of implanting the interbody and, upon completion of the introduction, can be easily disengaged from the implanted interbody.  
         [0010]     Also provided is a device having an adjustable angle distal end for introducing an interbody into an intervertebral space wherein the adjustable angle distal portion of the elongated device can be selectively directed to at least one angle away from the longitudinal axis of the device and locked in that configuration.  
         [0011]     Also provided is a device having an adjustable angle distal end for introducing an interbody into an intervertebral space wherein the distal portion of the elongated device can be selectively directed to at least one angle away from the longitudinal axis of the device, locked in that configuration, and repeatedly unlocked and readjusted to other angles as required.  
         [0012]     Also provided is a method of introducing an interbody into an intervertebral space using a device having an adjustable angle distal end, the distal end being capable of securely connecting to the interbody prior to the implantation of the interbody and easily releasing from the interbody after the interbody is implanted in a subject.  
         [0013]     Also provided is a kit containing at least one adjustable angle interbody introducing device as disclosed herein and at least one other orthopedic device or tool used in spine surgery procedures. The kit can include at least one interbody device.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The foregoing and other features of the adjustable interbody introducer device will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of exemplary embodiments with reference to the accompanying drawings, wherein:  
         [0015]      FIG. 1  shows an isometric view of the device having an adjustable angle distal end for introducing an interbody into an intervertebral space. The adjustable angle distal end of the device is shown positioned at an angle that is slightly elevated above the longitudinal axis of the device.  
         [0016]     FIGS.  2 A-B show a side view and a top view, respectively of the device of  FIG. 1 .  
         [0017]      FIG. 3  shows an enlarged detailed view of the interbody grasping unit extending from a truncated representation of the outer shaft and inner shaft of the device.  
         [0018]      FIG. 4  shows the disassembled components of the device in assembly alignment less the handle and slap hammer connector.  
         [0019]      FIG. 5  shows the components of the device, which are shown in  FIG. 4 , fully assembled with the handle and slap hammer connector in assembly alignment.  
         [0020]      FIG. 6  shows an enlarged cross-sectional side view of the interbody grasping unit extending from a truncated representation of the outer shaft of the device. An interbody device is shown secured in the grasping unit.  
         [0021]      FIG. 7  shows a side view of a threaded interbody connection shaft.  
         [0022]     FIGS.  8 A-C shows side views of the device having an adjustable angle distal end for introducing an interbody into an intervertebral space, wherein FIGS  8 A,  8 B, and  8 C, respectively represent only three examples of the multiple angles to which the distal end of the device can be selectively directed. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]     Detailed embodiments of the present invention are disclosed herein; however, it is understood that the following description and each of the accompanying figures are provided as being exemplary of the invention, which may be embodied in various forms without departing from the scope of the claimed invention. Thus, the specific structural and functional details provided in the following description are non-limiting, but serve merely as a basis for the invention as defined by the claims provided herewith. The device described below can be modified as needed to conform to further development and improvement of materials without departing from the inventor&#39;s concept of the invention as claimed.  
         [0024]     The device, as generally shown at  10  in FIGS  1 ,  2 A-B,  4 ,  5  and  8 A-C is an interbody introducer having an adjustable angle distal end. The device  10  has a proximal first end  12  and a distal second end  14 . As shown in  FIG. 4 , the device  10  includes a tubular inner shaft  16  having a proximal inner shaft first end  18  and a distal inner shaft second end  20  with an inner shaft lumen  22  extending the full length of the inner shaft  16  and having an inner shaft entry portal  24  defined at the inner shaft first end  18  by the circumferential inner shaft wall  26  and an inner shaft exit portal  28  defined at the inner shaft second end  20  by the circumferential inner shaft wall  26 .  
         [0025]     As also shown in  FIG. 4  the device  10  includes a tubular outer shaft  30  having a proximal outer shaft first end  32  and a distal outer shaft second end  34  with an outer shaft lumen  36  extending the full length of the outer shaft  30  and having an outer shaft entry portal  38  defined at the outer shaft first end  32  by the circumferential outer shaft wall  40  and an outer shaft exit portal  44  defined at the outer shaft second end  34  by the circumferential outer shaft wall  40 .  
         [0026]     The inner shaft  16  is sized and configured to easily fit within the outer shaft  30  so as to permit rotational movement about the longitudinal axis of the device. As shown in  FIG. 1 ,  2 A-B,  5  and  8 A-C, the inner shaft  16  is provided with a handle  46  having a handle proximal first end  48  and a handle distal second end  50 . The handle  46  is attached around at least a portion of the proximal first end  18  of the inner shaft  16 . As shown in  FIG. 5  the outer surface  52  of the first end  18  of the inner shaft  16  can be provided with handle attachment threads  54 , which are complimentary to handle threads  56 , which are defined on at least the distal portion of the inner wall  58  of the handle lumen  60 . This threaded attachment of the distal second end  50  of the handle  46  to the proximal first end  18  of the inner shaft  16  is preferred; however, other attachments, as are known in the art can be used without departing from the inventor&#39;s concept. Examples of other handle attachments can include, bayonet fittings, snap fittings, cotter pin attachments, and the like. In addition to using a threaded attachment of the handle  46  to the inner shaft  16 , the handle  46  and the inner shaft  16  can be provided with complimentary dowel holes  64 ,  66  and a securing handle dowel pin  67  at or near the location of the threaded attachment.  
         [0027]     Movement of the inner shaft  16  within the lumen  36  of the outer shaft  30  is initiated by the manual rotation of handle  46 , which is securely connected to the inner shaft  16  so as to directly transfer the rotational movement of the handle  46  to the rotational movement of the inner shaft  16 . This rotational movement of the inner shaft  16  within the lumen  36  of the outer shaft  30  effects the adjustment of the relative angle of the distal second end  14  to the longitudinal axis of the device  10  due to the unique articulating interaction of the slant geometry of an outer shaft cam surface  70  at the distal second end  34  of the outer shaft  30  and the geometry of a grasping unit proximal contact surface  72  of the grasping unit  74  of the device  10 .  
         [0028]     The grasping unit  74  of the device, as shown in detail in  FIG. 3 , is connected to the distal second end  20  of the inner shaft  16  by an articulating hinge  76  as shown in  FIGS. 1, 2A ,  3 ,  4 ,  5 ,  6  and  8 A-C. The articulating hinge  76  includes complimentary grasping unit hinge arms  78  that are attached to corresponding inner shaft hinge arms  80  by opposing grasping unit hinge pins  82 ,  84 . The articulating hinge  76  allows movement of the inner shaft  16  and the grasping unit  74  in multiple planes in the same way as is commonly found in a universal type joint, which is well known in the art.  
         [0029]     The outer shaft  30  is circumferentially disposed around the at least a portion of the inner shaft  16 . The inner shaft  16  is sized and configured to freely rotate within the lumen  36  of the outer shaft  30 . The distal second end  34  of the outer housing  30  is approximate to the location of the distal second end  20  of the inner shaft  16 . Outer shaft gripping surfaces  31  are provided on the outer shaft to facilitate ease of operation of the device. The proximal first end  32  of the outer shaft  30  is abutted against a proximally disposed angle locking ring  68 . As shown in  FIG. 4 , the locking ring  68  is secured to the inner shaft  16  by a locking ring dowel pin  86 . Disposed between the distal inner surface of the locking ring  68  and the surface of the proximal first end  32  of the outer shaft  30  is a biased bearing assembly, generally shown at  88  in  FIG. 4 . As is well known in the art, the biased bearing assembly  88  includes multiple ball bearing units  90 , each bearing  90  having a corresponding biasing element  92 , a preferable example of which is a coil spring. As is well known in the art, the components of the assembly  88 , under compression from the biasing elements  92 , are held in relative position one to the other by the securely affixed locking ring  68 . Multiple indentations  94  (not directly shown) that correspond in number, in size and in arc radius to the multiple bearings  90  in the assembly  88  can be defined in the inner surface of the locking ring  68 . As is known in the art, operation of the biased bearing assembly  88  requires rotation of the outer shaft  30  around the inner shaft  16 , that rotation being punctuated by movement of the biased bearings  90  from one indentation  94  to the next such that the rotational movement is naturally paused as each bearing  90  is biased into the next indentation  94 . The tactile feedback of this momentarily interrupted rotation attendant to the biased bearing assembly  88  is similar to a ratcheting effect. In addition to a tactile sensation in the device  10 , it is common for biased bearing assemblies to also produce an audible indication of movement of the bearings  90  from one indentation  94  to the next. When the movement is momentarily halted by the user, the biasing elements  92  provide measured resistance to further movement and thus tend to hold the bearings in their respective indentations thereby serving to hold or lock the device  10  in its last selected position.  
         [0030]     The grasping unit  74  at its proximal edge is provided with a cam surface  96  that is configured to be in contact with the at least a portion of the distal edge  98  of the outer shaft  30  as the inner shaft  16  is selectively rotated within the lumen of the outer shaft  30 . As best shown in FIGS.  8 A-C, the slant geometry of the distal edge  98  of the outer shaft varies in relative position to the grasping unit  74  cam surface  96  as the inner shaft  16  is rotated. The effect of this contact between the slant geometry of the distal edge  98  and the cam surface  96  of the grasping unit  74  is to alter the angle of the grasping unit  74  relative to the longitudinal axis of the device  10 . With reference to the discussion of the halting movement effect that results from rotation of the inner shaft  16  against the bias of the bias bearing assembly  88 , it is apparent that as the inner shaft  16  is selectively rotated within the lumen of the outer shaft  30 , the angle of the grasping unit  74  will vary in a corresponding and predictable fashion. As the relative rotation progresses, the biased bearing assembly  88  will momentarily halt and lock the angle of the grasping unit in place until additional rotational force is manually applied to the device  10 . The user can be provided with tactile and audible feedback of all rotational movement of the device. Further, as shown in  FIG. 1 , indicia  100  of the degrees of the selected angle can be provided on the proximal portion of the outer surface of the outer shaft. For example, grasping unit angle values indicating the variance from the longitudinal axis of the device  10  of −10 degrees to +50 degrees can be provided. However, the range of possible angles of which the device  10  is capable of achieving is determined by the amount of slant formed along the distal edge  98  of the outer shaft  30  and therefore, the disclosed device  10  can be manufactured to be capable of a wide range of angles.  
         [0031]     In operation, the user can employ a driving instrument, such as a surgical hammer or slap hammer to facilitate placement of the interbody into the proper position in the intervertebral space. To facilitate that likely possibility, the handle  46  of the device  10  is provided with a slap hammer recess  102  in the distal end that is sized and configured to accept a slap hammer connector  104  as is shown in  FIG. 5 . The slap hammer recess  102  can be communicate with and be continuous with the handle lumen  60  so as to provide a through passage along the longitudinal axis of the handle  46 .  
         [0032]     As shown in  FIG. 7 , an interbody connector shaft  106  within the lumen  22  of the inner shaft  16  is sized and configured to easily rotate around the long axis of the device and translate along the long axis of the device  10 . The interbody connector shaft  106  can be manufactured entirely or at least in its most distal portions of materials having good strength but being flexible such that the connector shaft  106  can be repeatedly bent at different angles as shown in  FIG. 7 . The interbody connector shaft has a connector shaft first end  108  and a connector shaft second end  110 . The connector shaft first end  108  is provided with a tool receptacle  112  that preferably corresponds to a standard tool for torque application, such as, for example, a screw driver. The connector shaft second end  110  defines an interbody securing element, which preferably is a threaded protrusion that is sized and configured to correspond to a threaded receptacle defined in the end portion of an interbody, as shown in  FIGS. 3, 6 ,  7  and  8 A-C. The connector shaft  106  can be threaded into the interbody as shown in  FIG. 6  by attaching a tool, such as a screw driver, to the tool receptacle  112  and apply torque at the first end  108  of the connector shaft  106 . Access to the connector shaft tool receptacle  112  within the lumen of the inner shaft  16  can be achieved through the handle lumen  60 . Alternatively, as shown in FIGS.  1 ,  2 A-B,  5  and  8 A-C, rotational force can also be applied to the interbody connector shaft  106  by manually turning a thumb wheel  114  that can be securely fixed to the interbody connector shaft  106  by a thumb wheel dowel pin  116 . Visual and manual access to the thumb wheel  114  is provide through a thumb wheel window  118  defined through a portion of the wall of the inner shaft  16 . As shown in  FIGS. 2, 4 ,  5  and  8 A-C the thumb wheel window  118  can preferably be defined through opposing sides of the inner shaft  16  so as to expose opposite sides of the thumb wheel  114  and thereby optimize the user&#39;s access to the thumb wheel  114 .  
         [0033]     In the exemplary embodiment described herein, the grasping unit  74  is specifically configured to grasp an interbody implanted in a Transforaminal Lumbar Interbody Fusion (TLIF). As such, the grasping unit is provided with an interbody seat  120  having a specific geometry to correspond to the shape of the interbody. In addition to the threaded portion of the connector shaft second end  110 , which is best shown in  FIGS. 3 and 6 , the interbody seat  120  can be provided with a superior arm  122  and an inferior arm  124  that can be configured to provide circumferential grasping of at least a portion of the interbody  126 .  
         [0034]     While the device is described herein as an example adapted for use as an adjustable interbody introducer and particularly is well suited for use in Transforaminal Lumbar Interbody Fusion (TLIF), it is within the inventors&#39;understanding that the grasping element can be configured and adapted to conform to any implantable surgical device.  
         [0035]     In use, a surgeon can employ the disclosed advice by securing the interbody  126  to the grasping unit  74  of the device  10 , making an incision in the subject, defining an approach path to the surgical site, preparing the intervertebral space to receive the interbody  126 , and inserting the interbody  126  by adjusting the angle of the distal end of the device to the desired angle and repeating the insertion efforts as necessary. Upon achieving the proper position for the interbody, releasing the interbody from the grasping unit and removing the device from the surgical site.  
         [0036]     The device  10  can be manufactured as integral components by methods known in the art, to include, for example, molding, casting, forming or extruding, and machining processes. The components can be manufactured using materials having sufficient strength, resiliency and biocompatibility as is well known in the art for such devices. By way of example only, suitable materials cam include implant grade metallic materials, such as titanium, cobalt chromium alloys, stainless steel, or other suitable materials for this purpose. Some components of the device can be made from plastics, composite materials, and the like.  
         [0037]     It is also within the concept of the present invention to provide a kit, which includes the adjustable interbody introducer disclosed herein. Additionally, a kit can include additional orthopedic devices and instruments; such as for example, bone screws or plates, spinal rods, hooks or links and any instruments or tools associated therewith. Such a kit can be provided with sterile packaging to facilitate opening and immediate use in an operating room.  
         [0038]     Each of the embodiments described above are provided for illustrative purposes only and it is within the concept of the present invention to include modifications and varying configurations without departing from the scope of the invention that is limited only by the claims included herewith.