Abstract:
A method of preparing an intervertebral disc space between a pair of vertebral bodies to receive an implant comprises engaging a portion of a surgical instrument with at least one of the vertebral bodies. The surgical instrument has a passage therethrough. The method further comprises generating one or more images of the surgical instrument in the surgical field and visualizing the passage through the surgical instrument on the one or more images. The method further comprises aligning the surgical instrument with a surgical plane through the intervertebral disc space by maintaining visualization of the through passage on the one or more images while adjusting the surgical instrument.

Description:
BACKGROUND  
       [0001]     Technical advances in the design of joint reconstructive devices have revolutionized the treatment of degenerative joint disease, moving the standard of care from arthrodesis to arthroplasty. Reconstruction of a damaged joint with a functional joint prosthesis to provide motion and to reduce deterioration of the adjacent bone and adjacent joints is a desirable treatment option for many patients. For the surgeon performing the joint reconstruction, specialized instrumentation and surgical methods, particularly improved instrument alignment tools, may be useful to facilitate precise placement of the prosthesis.  
       SUMMARY  
       [0002]     In one embodiment, a method of preparing an intervertebral disc space between a pair of vertebral bodies to receive an implant comprises engaging a portion of a surgical instrument with at least one of the vertebral bodies. The surgical instrument has a passage therethrough. The method further comprises generating one or more images of the surgical instrument in the surgical field and visualizing the passage through the surgical instrument on the one or more images. The method further comprises aligning the surgical instrument with a surgical plane through the intervertebral disc space by maintaining visualization of the through passage on the one or more images while adjusting the surgical instrument.  
         [0003]     In another embodiment, a surgical instrument comprises an instrument body at least a portion of which is adapted for interposition between a pair of vertebral bodies and a first through opening in the instrument body. The first through opening defining a first axis through the instrument body. The first through opening is adapted for visualization with an imaging device when the first axis is generally perpendicular to a first image plane generated by the imaging device.  
         [0004]     In another embodiment, a method for assessing an orientation of a surgical instrument in a surgical field comprises positioning at least a portion of the surgical instrument in the surgical field. The surgical instrument has first and second passages therethrough. The method further comprises generating a first image of the surgical instrument, visualizing an axis of sight through the first passage in the surgical instrument on the first image, and generating a second image of the surgical instrument. The method further comprises visualizing an axis of sight through the second passage in the surgical instrument on the second image. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is a side view of a vertebral column having a damaged disc.  
         [0006]      FIG. 2  is a perspective view of an alignment guide according to an embodiment of the current disclosure.  
         [0007]      FIG. 3  is a perspective view of an anchoring device according to an embodiment of the current disclosure.  
         [0008]      FIG. 4  is an environmental view of the assembled alignment guide and anchoring device of  FIGS. 2 &amp; 3 .  
         [0009]      FIG. 5  is a cross sectional view of a surgical instrument according to another embodiment of the present disclosure.  
         [0010]      FIG. 6  is an environmental view of the surgical instrument of  FIG. 5 .  
         [0011]      FIG. 7  is a perspective view of an implantable prosthesis according to another embodiment of the present disclosure. 
     
    
     DETAILED DESCRIPTION  
       [0012]     The present disclosure relates generally to the field of orthopedic surgery, and more particularly to instrumentation and methods for spinal surgery. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to embodiments or examples illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alteration and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0013]     Referring first to  FIG. 1 , the numeral  10  refers to a human anatomy having a joint location which, in this example, includes an injured, diseased, or otherwise damaged intervertebral disc  12  extending between vertebrae  14 ,  16 . The damaged disc may be replaced by an intervertebral disc prosthesis  18  which may be a variety of devices including any of the prostheses which have been described in U.S. Pat. Nos. 5,674,296; 5,865,846; 6,156,067; 6,001,130; 6,740,118 and in U.S. Patent Application Pub. Nos. 2002/0035400; 2002/0128715; and 2003/0135277; 2004/0225366 which are incorporated by reference herein.  
         [0014]     A variety of surgical techniques may be used to repair the damaged joint. First, all or a portion of the damaged tissue including disc  12  may be excised. This procedure may be performed using an anterior, anterolateral, lateral, or other approach known to one skilled in the art, however, the following embodiments will be directed toward a generally anterior approach unless otherwise specified. Generally, the tissue removal procedure may include positioning and stabilizing the patient. Fluoroscopic, x-ray and/or other imaging methods may be used to assist with vertebral alignment and surgical guidance. The tissue surrounding the disc space may be retracted to access and verify the target disc space. Imaging techniques may also be used to determine the proper sizing of the intervertebral prosthesis  18 . In one embodiment, a sizing template may be used to pre-operatively determine the correct prosthesis size. The area of the target disc may be prepared by removing excess bone, including osteophytes which may have developed, and other tissues which may include portions of the annulus and all or portions of the nucleus pulpous. The tissue removal procedure, which may include a discectomy procedure, may alternatively or additionally be performed after alignment and/or measurement procedures have been taken.  
         [0015]     Certain surgical instruments that will be described below are similar to the instrumentation described in U.S. patent application Ser. No. 10/799,178 (“the &#39;178 application”) entitled “Technique and Instrumentation for Intervertebral Prosthesis Implantation Using Independent Landmarks,” filed Mar. 12, 2004 which is incorporated by reference herein.  
         [0016]     Various alignment procedures may be conducted with surgical instrumentation to align the intervertebral space in preparation for the disc prosthesis  18 . The transverse center of the disc space may be determined and marked. Referring now to  FIG. 2 , in one embodiment, a surgical instrument used for alignment may be an alignment guide  30 , comprising an intervertebral portion  32 . The intervertebral portion  32  may be selected to permit insertion between the adjacent vertebrae  14 ,  16  with minimal distraction. The alignment guide  30  may further comprise positioning guides  34 ,  36 . In one embodiment, as illustrated in  FIG. 2 , the positioning guides  34 ,  36  may have differing lengths to facilitate easy coupling to subsequent instrumentation.  
         [0017]     Slots  38 ,  39 ,  40 ,  42  may extend through the body of the alignment guide  30 , providing a radiolucent pathway visible when imaged with imaging equipment such as x-ray or fluoroscopic equipment. These slots, passages, or openings  38 ,  40 ,  42  may allow visualization through the guide  30 , thereby allowing a user to view a generated image to determine whether the alignment guide is oriented properly. On the generated image, the through slots  38 ,  40 ,  42  may appear as a contrasting shade. The slots  38  and  40  may have a generally narrow, elongated shape and may extend in a direction  44  which may be a transverse axis when the alignment guide  30  is in use. The slots  42  may also have a generally narrow, elongated shape and may extend in a direction  46  which may be a sagittal axis when the alignment guide  30  is in use. Slot  38  may have a through axis of sight  48 , and slot  42  may have a through axis of sight  49 .  
         [0018]     Referring now to  FIG. 3 , an anchoring device  50  may include a vertebral body attachment portion  52 , a restraint pin  54 , a seat. 56 , and constraint members  58 . The restraint pin  54  may be retractable or fixed. The anchoring device  50  may further include slots  60 ,  62 ,  64 . These slots may allow visualization through the device  50  when observed with imaging equipment such as x-ray or fluoroscopic equipment. The slots  58 ,  60 ,  62  may have a generally narrow, elongated shape and may extend in the direction  44  when the anchoring device  50  is in use.  
         [0019]     The shape and location of the slots  38 ,  40 ,  42 ,  58 ,  60 ,  62  are merely exemplary and it is understood that in alternative embodiments, the slots may have a circular cross-section, a square cross-section or any other shape. The slots may be empty as shown in the embodiments of  FIGS. 2 and 3 , however the slots may also be filled or plugged with a radiolucent material or other material that provides contrast when viewing the slot on a generated image.  
         [0020]     The anchoring device  50  may attach to surgical instrumentation such as the distracting assembly described in the &#39;178 application. Alternatively, as shown in  FIG. 4 , the anchoring device  50  may attach to the alignment guide  30 . Specifically, in the illustrated embodiment, one set of positioning guides, for example guides  36 , may mate with the constraint portions  58 . The constraint portions  58  may prevent movement of the alignment guide  30  relative to the anchoring device  50  respectively. The alignment guide  30  may also engage with the anchoring device  50  by magnetic or other mechanical connections. As shown in  FIG. 4 , the alignment guide may be connected to a second anchoring device  70 . The anchoring device  70  may be substantially similar to anchoring device  50  and therefore will not be described in detail.  
         [0021]     With the alignment guide  30  coupled to the anchoring devices  50 ,  70  the intervertebral portion  32  may be inserted between the vertebral endplates of vertebral bodies  14 ,  16 . Alternatively, the insertion of intervertebral portion  32  between the vertebral endplates may take place before or as the alignment guide  30  is coupled to the anchoring devices  50 ,  70 . The alignment guide  30  and the anchoring devices  50 ,  70  may be aligned relative to the vertebral bodies  14 ,  16  using the imaging equipment  72 , which may be x-ray or fluoroscopic equipment, and the slots  38 ,  39 ,  40 ,  42 ,  60 ,  62 ,  64 . For example, sagittal alignment of the guide  30  may be accomplished by positioning an imaging device  72  such that the image plane is parallel to a sagittal plane through the surgical field. The position of the alignment guide  30  may be adjusted until the generated image fully shows the open slot  38 . In this position, the axis of sight  48  through the slot  38  may be generally perpendicular to the plane of the image. Further, transverse alignment of the alignment guide  30  may be accomplished by positioning an imaging device (which may be the same or different than imaging device  72 ) such that the image plane is parallel to a transverse plane through the surgical field. The position of the alignment guide  30  may be adjusted until the generated image fully shows the open slot  42 . In this position, the axis of sight  49  through the slot  42  may be generally perpendicular to the plane of the image. The slots  39 ,  40  may also be used to orient the alignment guide  30  using a process similar to that described above. Likewise, the slots  60 ,  62 , and  64  may be used to orient the anchoring device  50  relative to the vertebral bodies  14 ,  16  using a process similar to that described above.  
         [0022]     In an alternative embodiment, if the alignment guide is to be angled with respect to the image plane, the slot may be formed at an angle through the alignment guide such that an axis of sight through the slot is still perpendicular to the image plane. In this way the axis of sight through the slot may be visualized on the generated image. In this embodiment, an opening of the slot may be in a plane that intersects the plane of the image.  
         [0023]     With the alignment verified, a hole may be drilled into the caudal vertebral body  16  through the vertebral body attachment portion  52  of the anchoring device  50 . An anchoring fixture, such as a bone screw (not shown), may be inserted through the vertebral body attachment portion  52  and into the vertebral body  16  thus firmly locking the seat  56  to the vertebral body  16 . As the bone screw descends through the vertebral body attachment portion  52 , the restraint pin  54  may become embedded in the vertebral body  16  to prevent rotation of the anchoring device  50  and the subsequent loosening of the anchoring device  50  from the vertebral body  16 .  
         [0024]     The seat  56  of the anchoring device  50  may be adjustable and thus may be raised, lowered, and/or tilted. With the seat  56  engaged with the vertebral body  16 , the corresponding seat of the cephalad anchoring device  70  may be adjusted to contact the vertebral body  14 , maintaining the alignment guide  30  aligned in a generally anterior-posterior direction. With the seat of anchoring device  70  in position, a second hole may be drilled into the cephalad vertebral body  14  through the vertebral body attachment portion of the anchoring device  70 . Another anchoring fixture, such as a bone screw, may be inserted through the anchoring device  70  and into the vertebral body  14  thus firmly locking the anchoring device to the vertebral body  14 . A restraint pin similar to pin  54  may then deploy into vertebral body  14 . The anchoring devices  50 ,  70  may become directly engaged with the vertebral bodies, and the alignment device may become directly or indirectly engaged with the vertebral bodies. It is understood that in an alternative embodiment, the cephalad anchoring devices  70  may be placed before the caudal anchoring device  50 . With the anchoring devices  50 ,  70  in place, the alignment guide  30  may be removed. The anchoring devices  50 ,  70  may remain in place to anchor additional instruments such as disc space milling tools, distraction instruments, and/or implant insertion tools.  
         [0025]     Referring now to  FIGS. 5 and 6 , an implant insertion guide  80  may have a slot  82  through a distal end  84 . The insertion guide  80  may be used to implant a disc prothesis  86  between the vertebral bodies  14 ,  16 . The slot  82  may provide a radiolucent pathway visible when imaged with imaging equipment such as x-ray or fluoroscopic equipment. The slot  82  may permit visualization through the guide  80 , thereby allowing a user to view a generated image to determine whether the guide  80  is oriented properly. The slot  82  may have a generally narrow, elongated shape and may have a through axis of sight  88 .  
         [0026]     The insertion guide  80  may be used to guide the prosthesis  86  into the intervertebral disc space using an anterior-oblique approach. The slot  82  may be visible on an image generated by the imaging device  72  when the axis of sight  88  is positioned generally perpendicular to the plane of the generated image. The slot  82  may be used to orient both the sagittal and anterior-posterior placement of the guide  80  and consequently the prosthesis  86  within the intervertebral disc space.  
         [0027]     Referring now to  FIG. 7 , alignment slots such as those described above may be used with implantable instrumentation and devices. For example an intervertebral articulating prosthetic joint  90 , similar to that described in U.S. patent application Ser. No. 10/774,157 entitled “Articular Disc Prosthesis for Anterior-Oblique Insertion” and incorporated by reference herein, may have a first articular component  92  and a second articular component  94 . The articular components  92 ,  94  cooperate to form the prosthetic joint  90  which is sized and configured for disposition within an intervertebral space between the adjacent vertebral bodies  14 ,  16 . The articular components  92 ,  94  may have through slots  96  which may be angled such that they are visible with imaging equipment and may be used to assess the intraoperative orientation of the joint  90 .  
         [0028]     In alternative embodiments, other types of surgical instrumentation may be aligned using alignment slots such as those described above. Such instrumentation may include distraction equipment, cutting tools, trial devices, insertion tools, revision tools, and diagnostic tools. Additionally, alignment slots may be used with implantable instrumentation such as vertebral fusion devices or any design of motion preservation implant. In still another alternative embodiment, the alignment slots may be used with instrumentation in other non-spinal surgical procedures. The alignment slots may be used with both orthopedic instrumentation or non-orthopedic instrumentation whenever alignment using imaging techniques such as x-ray or fluoroscope is possible.  
         [0029]     Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Accordingly, all such modifications and alternative are intended to be included within the scope of the invention as defined in the following claims. Those skilled in the art should also realize that such modifications and equivalent constructions or methods do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. It is understood that all spatial references, such as “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” “right,” “cephalad,” and “caudal,” are for illustrative purposes only and can be varied within the scope of the disclosure. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.