Abstract:
A holder is provided which couples to the spine. In an embodiment, the holder has two conduits into which sleeves may be inserted during a spinal fusion procedure. The holder may have a distractor extending from the bottom of the holder. The distractor secures the holder to the spine and maintains a proper separation distance between adjacent vertebrae. The sides of the distractor may be serrated to better secure the holder to the spine. The sleeves and conduits serve as alignment guides for instruments and implants used during the procedure. In an embodiment, the holder may include holes for fasteners that fixably secure the holder to vertebrae adjacent to a disk space. A flange may be placed around the holder to shield surrounding tissue and to provide a placement location for adjacent blood vessels during the spinal fusion procedure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to spinal fixation and fusion systems. The invention also generally relates to an insertion guide used during the insertion of a spinal implant system, wherein the implant system is used for correction, fixation, and/or stabilization of the spine. 
     2. Description of the Related Art 
     Intervertebral disks that become degenerated due to various factors such as trauma or aging typically have to be partially or fully removed. Removal of an intervertebral disk can destabilize the spine, making it necessary to replace the vertebral disk to maintain the height of the spine and to fuse the spine. Spinal implants are often used to prevent collapse of the spine. In a typical spinal fusion procedure, an intervertebral disk is removed and implants are inserted in the disk space between neighboring vertebrae. The implants maintain normal disk spacing and help restore spinal stability. 
     The implants may be constructed of any biocompatible materials sufficiently strong to maintain spinal distraction including, but not limited to, bone, stainless steel, or inert metals. Implants are typically packed with bone graft or a synthetic bone graft substitute to facilitate spinal fusion. Implants may have a variety of shapes, which include, but are not limited to, threaded cylinders, unthreaded cylinders, and parallelepipeds. 
     An anterior spinal fusion procedure is often preferred to a posterior spinal fusion procedure. An anterior spinal fusion procedure may require less bone removal and muscle distraction than a posterior spinal fusion procedure. Also, an anterior spinal fusion procedure may involve less risk of nerve damage than a posterior spinal fusion procedure. In an anterior spinal fusion procedure, a surgical opening in the abdomen may be up to ten inches deep. A protective sleeve may be used during preparation and insertion of a spinal implant. The protective sleeve may serve to protect abdominal organs, blood vessels and other tissue during the spinal implant procedure. The sleeve typically extends above the surgical opening during use. The sleeve may maintain distraction of the vertebrae. Also, the sleeve may serve as an alignment guide for tool and implant insertion during the surgical procedure. 
     Protective sleeves typically have distractors on a distal end. Distractors are projections that may be inserted into a disk space during a spinal fusion procedure. The distractors may serve to achieve and maintain distraction of adjacent vertebrae. Distractors may also help to secure the protective sleeve to the spinal column during the procedure. Protective sleeves may have one tube or two parallel tubes. FIG. 1 shows a single-tube protective sleeve, and FIG. 2 shows a dual-tube protective sleeve. 
     FIG. 1 illustrates a single-tube protective sleeve  30  used in a spinal fusion procedure. A spinal fusion procedure involves the insertion of one or more implants in a disk space between two vertebrae. Protective sleeve  30  includes a substantially long, hollow tube  32 , two distractors  34  on opposite sides of an end of the tube, and two spikes  36  (only one shown) on opposite sides of the end of the tube. Protective sleeve  30  is typically sufficiently long to allow access to a spinal column of a large patient during an anterior procedure. Protective sleeve  30  may also be used in a posterior spinal fusion procedure. 
     A spinal fusion procedure using implants typically involves the insertion of two implants that are bilaterally positioned in an intervertebral disk space. During an anterior procedure, the disk space is prepared by performing a discectomy and by distracting the vertebrae adjacent the disk space. A cap (not shown) is placed on end  38  of the protective sleeve  30  opposite distractors  34  to protect the end of the sleeve during insertion. Distractors  34  may then be hammered into the disk space by striking the cap with a mallet (not shown). Spikes  36  are hammered into disk bone on the vertebrae and help to stabilize protective sleeve  30  during the procedure. Distractors  34  serve to separate the adjoining vertebrae to approximately normal spacing. 
     After insertion, a hole is drilled in the disk space by inserting a tool with a reaming head attachment through tube  32  and rotating the tool until a predetermined depth is reached. In some procedures, the hole is then tapped by inserting a tool with tap head attachment through tube  32  and rotating the tool until a predetermined depth is reached. The top and bottom of the reamed and tapped hole may extend into the end plates of the adjacent vertebrae. After the hole is prepared, an implant may be inserted in the hole by attaching the implant to an implant insertion tool and inserting the implant through tube  32 . For untapped holes, the implant may be hammered into the hole by striking the implant insertion tool with a mallet. For tapped holes, the implant may be threaded into the hole by turning the implant insertion tool. Then, the protective sleeve  30  may be removed. 
     If a second implant is to be inserted, the protective sleeve  30  is hammered in the disk space opposite the first implant and the procedure is repeated. Alternatively, the protective sleeve  30  may remain inserted in the disk space, and a second single-tube protective sleeve  30  may be inserted adjacent to the protective sleeve. 
     The optimal alignment and spacing of implants in a spinal fusion procedure may be determined before surgery. Achieving the predetermined alignment and spacing during surgery is often important for optimal fusing of the adjacent vertebrae. Protective sleeve  30  has characteristics that may make achieving alignment difficult. First, each of the two holes is aligned, reamed, and tapped in a separate procedure. It is often difficult to align and space the holes correctly. Second, the alignment of protective sleeve  30  must be maintained after insertion. Any slight movement of protective sleeve  30 , which may act like a lever arm, may result in misalignment of the hole. 
     FIG. 2 illustrates a dual-tube protective sleeve  40  used in a spinal fusion procedure involving the insertion of two implants into a disk space. Protective sleeve  40  includes substantially long, hollow tubes  32 , one or more distractors  34  and one or more spikes  36 . Protective sleeve  40  is typically long enough to allow access during an anterior procedure to an intervertebral disk in a large patient. Spinal fusion using implants with protective sleeve  40  involves the insertion of two implants, bilaterally positioned in parallel in an intervertebral disk space. During an anterior procedure, the disk space is prepared by performing a discectomy and by distracting the vertebrae adjacent the disk space. A cap (not shown) is placed on the end  42  of protective sleeve  40  opposite distractor  34  to protect the sleeve during insertion. Distractor  34  is then hammered into the disk space by striking the cap with a mallet (not shown). Spikes  36  are hammered into disk bone on the adjacent vertebrae to help stabilize protective sleeve  40  during the procedure. Distractor  34  serves to separate the adjoining vertebrae to approximately normal spacing. After insertion, holes are reamed in the disk space by inserting a tool with a reaming head attachment through tubes  32  and rotating the tool until a predetermined depth is reached. In some procedures, the holes are tapped by inserting a tool with a tap head attachment through tubes  32  and rotating the tool until a predetermined depth is reached. The top and bottom of the reamed and tapped holes may extend into the end caps of the adjacent vertebrae. After the holes are prepared, implants are inserted in the holes by attaching the implants to an implant insertion tool and inserting the implants through tubes  32 . For untapped holes, the implants are hammered into the hole by striking the implant insertion tool with a mallet. For tapped holes, the implants are threaded into the holes by turning the implant insertion tool. After both implants are inserted, protective sleeve  40  is removed. 
     FIG. 3 shows a representation of implants inserted into disk space  44  using a dual-tube protective sleeve  40 . Spinal nerves in the spinal canal  46  are protected by dura  48 . Nerves  50  extend from the spinal canal  46 . Implants  52  are inserted between two vertebrae  54  (one shown). Care must be taken during insertion of the implants  52  to make sure that the implants do not impinge on the nerves  50 . 
     Like single-tube protective sleeve  30 , dual-tube protective sleeve  40  has characteristics that make it difficult to align the implants correctly. First, the alignment of protective sleeve  40  must be maintained after insertion. Any slight movement of sleeve  40 , which may act like a lever arm, may result in misalignment of the hole. Second, the long parallel tubes make it difficult to angulate the two implants  52  relative to each other. Angulated implants may be the desired alignment in some spinal fusion procedures. Using a dual-tube protective sleeve  40  has the advantage that the surgical procedure is simplified because there is only one insertion procedure, as opposed to two insertion procedures for a single-tube protective sleeve  30 . 
     Single- and dual-tube protective sleeves share some disadvantages. First, the sleeves are typically unitary members that are long enough to extend out of a ten-inch deep surgical opening after being hammered into place. To maintain alignment after insertion, the sleeve must be kept as motionless as possible. The sleeve tends to act like a lever arm, and any slight motion of the sleeve during the procedure may result in misalignment of the implants. The sleeve acting as a lever arm is particularly problematic when the sleeve is handed off during the surgical procedure from one member of the surgical team to another member of the surgical team. 
     A second disadvantage of protective sleeves is related to the first disadvantage. The sleeve is held in place only by the distractors and the spikes inserted in the disk space. This connection may not be very secure. Because the connection is not secure, the sleeve may have to be held by the members of the surgical team throughout the entire procedure to maintain proper alignment. As noted above, any slight movement can result in the misalignment of the implants. 
     A third disadvantage of protective sleeves is that they may afford minimal protection to surrounding tissues during a spinal fusion procedure. Major blood vessels, parallel the anterior surface of the spine for much of the spine&#39;s lower length. These vessels may be retracted during the procedure. The interface between the distal end of the sleeve and the spinal column is typically not a perfect fit. Gaps may exist between the sleeve and the vertebrae. The presence of gaps creates the risk of drill bits, taps, and implants coming into contact with the blood vessels or other surrounding tissues during the procedure. Also, the blood vessels may be pinched between the sleeve and the vertebrae. A nick or cut to either the aorta or the blood vessels can be life threatening. 
     The above-mentioned methods and systems inadequately address the need to angulate implants in some spinal fusion procedures, the need to maintain precise alignment throughout the procedure, and the need to protect surrounding tissues during the procedure. It is therefore desirable that an improved method and system be derived for inserting spinal implants during a spinal fusion procedure. 
     SUMMARY OF THE INVENTION 
     A holder or base may be used to insert instruments and/or spinal implants into a disk space during a spinal fusion procedure. In an embodiment, distractors and tangs of a holder may be driven into an intervertebral disk space. The distractors and tangs may secure the holder to the spine during. In an embodiment, fasteners extending through a holder into the adjacent vertebrae may be used fix the holder to the spine. In another embodiment, distractors, tangs, and fasteners secure a holder to the spine. A flange may be placed around the holder to protect the surrounding tissue and blood vessels. Protective sleeves may be inserted into and may be removed from conduits in the holder. A portion of the sleeve may have a slot or a window, located adjacent to the top of the holder. The slot or window may serve as a view-port to provide increased visibility near the procedure site. Surgical instruments may be inserted through the protective sleeves and through the holder conduits to prepare the intervertebral space for an implant. 
     An embodiment of a holder includes a body, one or more conduits passing through the body from the top to the bottom, one or more distractors on the bottom of the body, and one or more tangs on the bottom of the body. The body may have a smooth outer surface with no sharp comers. In some embodiments, the body may be flared near the bottom to provide shielding for surrounding tissue. The flared bottom may provide room for optional fasteners to extend at oblique angles from the body of the holder. The flared body may also provide the holder with a stable base against the spinal column. 
     An optional flange may be provided that fits around the outer surface of the holder. The flange may provide shielding of soft tissue, such as blood vessels and organs, from cutting tools at the junction of the holder and the vertebral bodies. The flange may also prevent damage to soft tissues due to pinching of the soft tissue between the holder and the vertebral bodies. The flange may be made of a rigid or semi-rigid material. A portion of the flange may be made of an elastic material so that the flange may stretch over and slide down the holder. In one embodiment, the holder may include a rim for holding the flange in place after installation. In another embodiment, the holder may include a groove for holding the flange in place. In another embodiment, the flange has an elastic collar, which holds the flange in place against the holder. 
     In some embodiments, the inner surfaces of the conduits may contain shoulders to limit the insertion distance of protective sleeves in the conduits. Above a shoulder, a conduit may be sized to match the outer diameter of a protective sleeve. Below the shoulder, the conduit may be sized to match the outer diameter of instrument heads and implants to be used in the procedure. In some embodiments, the shoulder may include slots configured to engage distractors on protective sleeves; thus allowing the holder to be used with single-tube protective sleeves having distractors. 
     Embodiments of the holder may have non-circular conduits. The cross sectional shape of the holder conduits and the protective sleeves inserted into the holder may be any desired shape that allows for the insertion of spinal implants into a disk space. For example, the cross sectional shape of the conduits may be rectangular if the cross sectional shape of the spinal implants are generally rectangular. Other embodiments of the holder may have circular conduits or conduits which do not have a regular geometric shape. Embodiments of holders that have circular conduits may be constructed with conduits of different diameters to accommodate protective sleeves and implants of different diameters. 
     Embodiments of holders may be provided with non-parallel angled conduits. Non parallel conduits allow the insertion of implants at oblique angles to improve spinal fusion and to protect nerves posterior to the disk space. Other holder embodiments may have parallel conduits. 
     The distractors on the bottom of the holder body are projections that insert into a disk space during a spinal fusion procedure. The distractors may serve to achieve and/or maintain distraction of the adjacent vertebrae. The distractors may also secure the holder to the spinal column during the procedure. The distractors may be substantially wedge-shaped, and may include curved surfaces. The tangs on the bottom of the holder body may serve to maintain distraction, and may also maintain a parallel orientation of the vertebrae during the procedure. The tangs may also be substantially wedge-shaped, and may also include curved surfaces. Outer surfaces of the distractors and tangs may be serrated to secure the holder to adjacent vertebrae during a spinal fusion procedure. 
     In one embodiment, there is one distractor centrally located between two conduits; and two tangs, with one next to each conduit opposite the distractor. Curved inner surfaces on the tangs and curved surfaces on the distractor may serve as partially enclosed extensions of the conduits, and may help maintain alignment of the implant during a spinal fusion procedure. 
     In some embodiments, the body includes one or more fastener holes for the insertion of fasteners into vertebrae. The fastener holes may be angled so that fasteners inserted through the holes extend obliquely into adjacent vertebrae without damaging the vertebral endplates. The fasteners may pass through the end caps of the vertebrae into cancellous bone in the interior of the vertebrae. The fasteners may serve to substantially anchor the holder to the spine during the spinal fusion procedure. 
     The height of the holder, when inserted in a spine, may be substantially less than the length of a protective sleeve. During the spinal fusion procedure, a protective sleeve may be inserted into a holder conduit when needed and removed when not needed without affecting alignment. Removal of a protective sleeve from the holder decreases the likelihood of a protective sleeve being inadvertently used as a lever arm during the procedure. Removing a protective sleeve from the holder may increase visibility at the procedure site. Removing a protective sleeve may also allow for easy irrigation of the entire surgical site, including the holes being prepared for the implants. 
     The ability to remove the protective sleeves when not in use, the short profile of the holder, and the fastener anchoring system all help to maintain proper alignment during the insertion of implants in a spinal fusion procedure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the present invention will become apparent to those skilled in the art with the benefit of the following detailed description of embodiments and upon reference to the accompanying drawings in which: 
     FIG. 1 illustrates a single-tube protective sleeve; 
     FIG. 2 illustrates a dual-tube protective sleeve; 
     FIG. 3 is a representation of implants inserted into a disk space with a dual-tube protective sleeve, or with an embodiment of a holder of the present invention that has parallel conduits; 
     FIG. 4 is a perspective view of a first embodiment of a holder; 
     FIG. 5 is a front view the first embodiment holder; 
     FIG. 6 is a side view the first embodiment holder; 
     FIG. 7 is a cross-sectional view of the first embodiment holder taken substantially along line  7 — 7  of FIG. 6; 
     FIG. 8 is a cross-sectional view of the first embodiment holder taken substantially along line  8 — 8  of FIG. 5; 
     FIG. 9 is a top view of the first embodiment holder; 
     FIG. 10 is a bottom view of the first embodiment holder; 
     FIG. 11 is a top view of an embodiment of a holder flange; 
     FIG. 12 is a top view of another embodiment of a holder flange; 
     FIG. 13 is a perspective view of an embodiment of a holder flange with a collar; 
     FIG. 14 is a perspective view of an embodiment of a holder flange; 
     FIG. 15 is a perspective view of an embodiment of a holder without conduit extenders; 
     FIG. 16 is a cross sectional view of an embodiment of a holder having a flange groove; 
     FIG. 17 is a cross sectional view of an embodiment of a holder without body flare; 
     FIG. 18 is a cross sectional view of an embodiment of a holder with an alternative fastener hole arrangement; 
     FIG. 19 is a perspective view of an embodiment of a holder having serrated distractors and tangs; 
     FIG. 20 is a perspective view of an embodiment of a holder having an extended upper opening and an insertion tool slot. 
     FIG. 21 is a perspective view of the embodiment shown in FIG. 20; 
     FIG. 22 is a perspective view of an insertion tool for an embodiment of a holder; 
     FIG. 23 is a perspective view of an alternate embodiment holder having overlapping conduits; 
     FIG. 24 is a top view of a possible arrangement of implants inserted into a disk space using the holder of FIG. 23; 
     FIG. 25 is a perspective view of a holder having one conduit; 
     FIG. 26 is a perspective view of a holder with an inserted protective sleeve and tool; 
     FIG. 27 is a front view of a holder with an alternate protective sleeve; 
     FIGS. 28 a - 28   e  illustrate steps included in a spinal fusion procedure using an embodiment of a holder; 
     FIG. 29 illustrates the positioning of major blood vessels around one embodiment of a holder during a typical L 5 /S 1  fusion procedure; 
     FIG. 30 illustrates the positioning of major blood vessels around one embodiment of a holder during a typical L 4 /L 5  fusion procedure; and 
     FIG. 31 illustrates the angulation of implants inserted using one embodiment of a holder. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, a holder or base for use as an insertion guide during a spinal implantation procedure is designated generally as  100 . A holder may be used to support a sleeve during a spinal fusion procedure, and a base may be used with or without a sleeve during a spinal fusion procedure. For illustrative purposes only, the following description will describe a holder. A person having ordinary skill in the art will understand that a holder may be used as a base, and a base may be used as a holder. 
     FIGS. 4-10 show views of a first embodiment of the holder  100 . The holder  100  may include unitary body  102 , conduits  104  through the body, conduit extenders  106 , flared portion  108 , flange rim  110 , holes  112 , distractor  114 , and tangs  116 . The height of the holder body may be less than about six inches. Preferably, the holder height is less than four inches, and more preferably, less than 2 inches. 
     The conduits  104  may have circular cross sections. Alternatively, the conduits  104  may have any desired cross sectional shape, such as rectangular or ellipsoid, to correspond to instruments and implants used during a spinal fusion procedure. 
     As shown in FIG. 6, the body  102  may have flared portion  108 . The flared portion  108  may allow for angulation of fastener holes  112 , as shown in FIG.  8 . Fastener holes  112  may be located in slot  118 . Angulated fastener holes  112  allow is fasteners  120  inserted through the fastener holes to penetrate adjacent vertebrae  54  through end caps  122  of the vertebrae and into cancellous bone  124 , as shown in FIG. 28 c . Attaching the holder  100  to the vertebrae  54  with fasteners  120  placed through end caps  122  may minimize weakening of the end plates  126  of the vertebrae. Shoulders  128  limit the insertion depth of the fasteners  120  into the holder  100 . Fasteners  120  may be any type of fastening device including, but not limited to, screws, nails, rivets, trocars, pins, and barbs. 
     The flared portion  108  of the body  102  may shield blood vessels, nerves, and other soft tissue from damage by the body and tools used during the spinal fusion procedure. In addition, the flared portion  108  increases the circumference of holder  100  to a maximum near flange rim  110 . Optional flange  130  may slip over the top of holder  100  and reside against the rim  110 . The flared portion  108  may also provide a stable base on the end caps  122  of the vertebrae  54  for holder  100 . 
     The perimeter of the conduit  104  at a top end of the holder  100  may match the outer perimeter of protective sleeve  132  inserted into the conduit. The conduits  104  may include shoulders  134 . A shoulder  134  prevents insertion of a protective sleeve  132  into a conduit  104  beyond a certain depth. As shown in FIG.  9  and in cross section in FIG. 7, a conduit  104  may include slots  136 . The slots  136  correspond to the shape of the distractors  34  on the ends of single-tube protective sleeves  30 . Slots  136  allow a holder  100  to be used with a single-tube protective sleeve  30  having distractors  34 , such as the sleeve shown in FIG.  1 . In other embodiments, conduits  104  may be configured to receive protective sleeves  132  without distractors  34  by having shoulders  128  which extend fully around the diameter of the conduits  104 . A protective sleeve  132  may be slid into a conduit  104  without the use of an insertion tool. 
     FIG. 7 shows a cross sectional view of the first embodiment holder  100  with the conduits  104  angulated toward one another. Having the conduits angled relative to one another allows for the angulation of implants  52 . Angulated implants  52  may provide a more stable fusion of vertebrae  54 . In addition, angulated implants  52  may be less likely to protrude from posterior side  138  of the disk space to press on nerves  50  exiting the spinal canal  46 . The angle A, located between a center line of a first conduit  104  and a centerline of an adjacent conduit, may vary from 0 to about 30 degrees, preferably the angle A is less than about 20 degrees, and more preferably, the angle A is less than about 10 degrees. If the angle A is 0 degrees, then the adjacent conduits  104  are parallel. 
     Flange rim  110  may support flange  130 . The flange  130  may serve to protect blood vessels and other tissue placed upon the flange  130  and near the body  102  of the holder  100 . FIGS. 11-14 show some flange embodiments. In one embodiment, ends  140  of the flange  130  are relatively wide to provide extra protection and a support area on the sides of the holder  100  where the blood vessels are most likely to be placed. As shown in FIG. 14, the flange  130  may have flexible collar  142  to more securely attach the flange to the body  102  of a holder  100 . The shape of the flange  130  during use may correspond to the anterior surface of the spine so that a snug fit against the spine is established during a spinal fusion procedure. The snug fit may help prevent tools used during the procedure from contacting and potentially damaging adjacent tissue. The flange  130  may be made of a semi-rigid elastic or plastic material so that an inner edge of the flange conforms to the shape of the holder body  102  after the flange has been stretched over and slid down the body. As shown in FIG. 14, the flange may have narrow brims  144 , and relatively short ends  140 . The ends  140  of the flange  130  are long enough to be easily positionable under adjacent vessels and tissue. 
     The distractors  114  and tangs  116  are protrusions, which may extend from the bottom of the holder body  102 . Distractor  114  may serve to maintain distraction of adjacent vertebrae  54  during a spinal fusion procedure. The distractor  114  may establish a separation distance between the vertebrae during the procedure. Tangs  116  may also serve to maintain distraction. The tangs may maintain a parallel orientation of the vertebrae  54  during the procedure. Distractor  114  and tangs  116  may be substantially wedge-shaped to facilitate insertion into the disk space  44 . Surfaces of distractor  114  and tangs  116  may be curved to match the curvature of the conduits  104 , so that the distractor and tangs serve as partially enclosed extensions of conduits. 
     Bottom  146  of the holder  100 , as seen in FIG. 5, may conform to the general shape of a vertebra  54 . When the holder is inserted into a disk space  44 , portions of the bottom  146  of the holder  100  may reside on end caps  122  of adjacent vertebrae  54 . Having the bottom  146  of the holder  100  shaped to conform to the shape of the vertebrae  54  may help to protect adjacent soft tissue and vessels from being pinched between the holder and the vertebrae during the spinal fusion procedure. 
     FIGS. 15-21 show some alternate embodiments of a holder  100 . FIG. 15 shows a holder without conduit extenders on the body  102 . FIG. 16 shows a cross sectional view of a holder  100  with flange groove  148 . The flange groove  148  may support an inner edge of a flange  130  to hold the flange at a desired position on the body  102 . FIGS. 16 and 17 show cross sectional views of holders  100  without fastener holes. FIG. 17 also shows the holder without a flared portion and without a flange rim or a flange groove. 
     FIG. 18 shows a cross sectional view of another embodiment holder with an alternate fastener hole  112  arrangement. In this embodiment, fastener holes  112  extend between conduits  104  from the top of body  102  downwards at an oblique angle relative to a vertical axis of holder  100 . The fastener holes  112  cross at point  150  and then exit near an outer edge of the lower portion of body  102 . The fastener holes  112  include shoulders  128  to limit the insertion depth of fasteners  120  into fastener holes  112 . To use this embodiment, one fastener  120  is inserted into a fastener hole  112  and into a vertebra  54  until the head of the fastener is past the cross point  150 . Then, another fastener  120  is inserted into the remaining fastener hole  112  and the fastener is inserted into the adjacent vertebra  54 . Both fasteners  120  may be further inserted into the vertebrae  54  until the fastener heads contact the shoulders  128 . 
     FIG. 19 shows an embodiment of a holder  100 , which has serrations  154  on outer edges of the distractor  114  and on the outer edges of the tangs  116 . Serrations  154  may maintain proper alignment and the serrations may inhibit the distractor  114  and tangs  116  from backing out of the vertebrae  54  after the holder  100  is inserted during a spinal fusion procedure. 
     FIG.  20  and FIG. 21 show perspective views of an alternate embodiment of a holder  100 . The body  102  may include flat sections  156 , large top opening  158 , undercut tool slots  160 , spring stop  162 , and ball  164 . The flat sections  156  may help to make the holder  100  easier to machine during the manufacturing. The holder may have large top opening  158  with conduits  104  located in a lower section of the body. The body  102  may have undercut tool slots  160  (only one shown). Coil springs (not shown) are placed in the body  102  between the spring stops  162  and the balls  164  (only one shown). The spring stops  162 , coil springs and balls  164  form an assembly that removably connects an insertion tool  166  to the holder  100 . 
     FIG. 22 shows a perspective view of the insertion tool  166  used with the holder shown in FIG.  20  and FIG.  21 . The insertion tool  166  includes attachment head  168 , dimples  170 , shaft  172 , and top member  174 . The attachment head  168  of the insertion tool  166  is inserted into the top opening  158  of the body  102 . The insertion tool  166  is rotated approximately 90 degrees. Rotating the insertion tool  166  forces the balls  164  in the holder body  102  against the coil springs, and compresses the springs. When the dimples  170  align with balls  164 , the springs force the balls into the dimples and attach the insertion tool  166  to the holder  100 . When the holder  100  is attached to the insertion tool  166 , the insertion tool functions as a handle and allows the holder to be positioned at a desired location. A mallet (not shown) may be used to strike upper surface  176  of the top member  174  to insert the holder into a disk space  44  after the holder is positioned at a desired location. To remove the insertion tool  166  from the holder  100 , the insertion tool is rotated approximately 90 degrees, and the attachment head  168  is removed from the opening  158 . 
     FIG. 23 shows a perspective view of an embodiment of a holder  100  wherein the conduits  104  of the holder overlap. The holder has a pair of distractors  114  located at opposite sides of the body  102 . FIG. 24 shows a schematic representation of one possible arrangement of implants  52 ,  53  inserted in a disk space  44  with the embodiment of a holder  100  shown in FIG.  23 . 
     FIG. 25 shows an embodiment of the holder  100  having one conduit  104  extending through the body  102 . The holder  100  may have a pair of distractors  114  located at opposite sides of the conduit  104 . The holder may have fastener holes (not shown) that allow fasteners to attach the holder to vertebrae  54  during a spinal fusion procedure. 
     FIG. 26 illustrates an embodiment of a holder  100  with protective sleeve  132 , driver  180 , and attachment  182 . Tube  32  of protective sleeve  132  may be inserted in one of the conduits  104  of holder  100 . Shaft  184  of driver  180  may be inserted in tube  32 . At least a portion of shaft  184  may have a diameter substantially equal to the inside diameter of tube  32  to maintain alignment of the driver  180  during use. Stop  186  may serve to limit the distance shaft  184  may be inserted into tube  32 . In some embodiments, stop  186  may be adjustable to allow different insertion depths. The driver  180  may have handle  188  for turning shaft  184  located on an end of the shaft. Attachment  182  may be located on an end of the shaft opposite to the handle  188 . Attachments may include, but are not limited to, drilling heads and tapping heads. An implant  52  may also be coupled to the distal end of a driver for insertion into a disk space  44 . 
     FIG. 27 illustrates an embodiment of a protective sleeve  132  prior to insertion into an embodiment of a holder  100 . The protective sleeve  132  includes widened portion  190  at an end of the sleeve. The widened portion  190  receives a tool (not shown) having a complementary wide portion at an end of the tool. The sleeve  132  may include view-port  192  to provide improved visibility of the surgical site during the procedure. The view-port may be a window, a slot, or other structure that allows increased visibility of the surgical site during the procedure. 
     FIGS. 28 a - 28   e  illustrate steps included in a spinal fusion procedure using an embodiment of a holder  100 . In FIG. 28 a , holder  100  is shown being inserted into disk space  44  between adjacent vertebrae  54 . Distractor  114  may be driven into the disk space  44  by striking insertion device  194  with mallet  196 . Insertion device  194  may fit in the conduits  104 . Alternately, insertion device  194  may fit between conduits  104  in slot  118  to provide a contact surface with the holder  100  for hammering. In the embodiments of the holder  100  shown in FIGS. 20,  21 , and  23 , the insertion device may be an insertion tool  166  as shown in FIG.  22 . The insertion device  194  may be coupled with holder  100  prior to insertion into the surgical cavity, and may be used as a handle for inserting and positioning holder  100  by the surgeon prior to and during hammering. Distractor  114  separates vertebrae  54  as the distractor is hammered in. The distractor widens the disk space  44  to the desired width for the procedure. Holder  100  may be hammered with the mallet  196  until the bottom  146  of body  102  makes substantial contact with the adjacent vertebra  54 . 
     In FIG. 28 b , holder  100  has been hammered into the disk space  44  to an optimal depth. Optional flange  130  may then be slipped over the top of holder  100  to fit snugly against flange rim  110 . After flange  130  is installed, blood vessels  198 , such as the aorta and vena cava, which are retracted to one side during the installation of the holder  100 , may be placed over flange  130  next to body  102 , as shown in FIG.  29  and FIG.  30 . The shape of flange  130  serves to protect the blood vessels  198  from being pinched, nicked or cut during the remainder of the spinal fusion procedure. Body  102  may be formed with smooth, arcuate outer surfaces with no sharp comers to further protect blood vessels  198  and tissue. 
     FIG. 28 c  shows the insertion of optional fasteners  120  in fastener holes  112 , through end caps  122  and into cancellous bone  124  of vertebrae  54 . Angling of fasteners  120  into cancellous bone  124  avoids vertical penetration deep into the end plates  126 ; thus helping to prevent weakening of the endplates near the implants  52 . The head of driver  200  may fit into slot  118  to contact a fastener  120 . The slot  118  may protect surrounding soft tissues should the head of the driver  200  slip off the fastener  120 . Slot  118  may also help contain a fastener  120  should the fastener be dropped during the insertion process. In some embodiments, the heads of fasteners  120  may include hex or star shaped slots for receiving a corresponding driver  200 . In some embodiments, driver  200  may include a bent or bendable shaft to facilitate the angled insertion of the fasteners  120  in the fastener holes  112 . In some embodiments, the shaft of driver  200  may be long enough to allow the surgeon to turn the driver above the surgical cavity while the head of the driver is coupled to the head of a fastener  120 . In some embodiments, a fastener  120  may be coupled to the driving head of driver  200  to help prevent dropping the fastener into the surgical cavity during insertion. 
     In FIG. 28 d , protective sleeve  132  is inserted in one of the conduits  104  of the holder  100 . Shaft  184  of driver  180  is inserted into the protective sleeve  132 . Stop  186  serves to limit the distance shaft  184  may be inserted into sleeve  132 . Drilling head  182  may be coupled to the distal end of driver  180 . A handle (not shown) coupled to the proximal end of driving shaft  184  may be turned while applying downward pressure on driver  180  to drill out a hole in disk space  44 . Drilling the hole may also remove bone from the end plates  126  of adjacent vertebrae  54 . Flange  130  may protect adjacent blood vessels  198  and other soft tissues during the drilling process. 
     In spinal fusion procedures using threaded implants, after the hole is drilled, driver  180  is retracted and a tap (not shown) is attached to the driver. The tap and the driver  180  are inserted into the sleeve  132 . A handle (not shown) coupled to an end of the driving shaft  184  is turned while applying downward pressure on driver  180  to tap a flight of threads in the vertebrae  54 . After a flight of threads is formed in the hole, the driver is removed from the protective sleeve  132 . 
     Referring to FIG. 28 e , a threaded implant  52  is coupled to the distal end of an implant insertion tool  202 . The implant insertion tool  202  is inserted into the sleeve  132 . A handle (not shown) coupled to the proximal end of implant insertion tool  132  is turned while applying downward pressure to screw implant  52  into the threaded hole in disk space  44 . 
     In spinal fusion procedures using unthreaded implants, after the hole is drilled, an unthreaded implant  52  is coupled to an end of an implant insertion tool  202 . The implant insertion tool  202  is inserted into the protective sleeve  132 . A mallet (not shown) is used to strike the proximal end of implant insertion tool  202  to drive implant  52  into the disk space  44 . 
     In all embodiments, inserted implant  52  is then detached from insertion tool  202 . Protective sleeve  132  may then be removed from the conduit  104  of holder  100  and inserted into the adjacent holder conduit  104 . Optionally, a second protective sleeve  132  may be inserted in the adjacent conduit  104 . The steps described for FIGS. 28 d - 28   e  may then be repeated for the installation of the second implant. After the second implant  52  is installed, fasteners  120  may be backed out of vertebrae  54  and holder  100  may be removed from the disk space  44 . 
     An advantage of holder  100  illustrated in FIGS. 28 a - 28   e  is that the tools and protective sleeve  132  may be removed at any time during the procedure without affecting the alignment or spacing of the holder  100 . Fixing the holder  100  to the vertebrae with fasteners  120 , and inserting the protective sleeve  132  into the holder  100  only when necessary may minimize the risk of misalignment of implants  52  during a spinal fusion procedure. 
     FIG. 29 illustrates the positioning of major blood vessels  198  around a dual-conduit holder  100  during an L 5 /S 1  fusion procedure. Holder  100  is shown inserted in disk space  44  (L 5 /S 1 ) between vertebra  54  (L 5 ) and sacrum  204  (S 1 ). The bifurcation of major blood vessels  198  (the aorta and vena cava) typically is proximate vertebra L 5 . The right branch and left branch of major blood vessels  198  are shown separated and placed over holder flange  130 . In some patients, the bifurcation point of the major blood vessels  198  may be located higher or lower than proximate the L 5  vertebra. An irregularly located bifurcation point of the major blood vessels  198  may require the branches of the major blood vessels to be routed around one side of holder  100 . 
     FIG. 30 illustrates the positioning of major blood vessels  198  around a holder  100  during an L 4 /L 5  fusion process. Holder  100  is shown inserted in disk space  44  (L 4 /L 5 ) between adjacent vertebrae  54  (L 4  and L 5 ). The bifurcation of major blood vessels  198  typically is proximate vertebra L 5 . The major blood vessels  198  are shown placed over holder  100  upon flange  130 . The blood vessels may be placed on either side of holder  100 . 
     The configuration of holder  100  and the added protection of flexible flange  130  may serve to protect the blood vessels  198  from being nicked during the spinal fusion procedure. In addition, the body  102  of holder  100  may be curved and may lack sharp corners or edges to further protect the blood vessels  198  and other tissue from abrasion. Protecting the blood vessels  198  is critical in a spinal fusion procedure, as the aorta is a major artery and the vena cava is a major vein. Even a tiny nick in either blood vessel  198  is potentially catastrophic, and must be repaired quickly. A nick in the vena cava is particularly problematic because the vena cava has thinner walls than the aorta, making the vena cava easier to nick and harder to repair than the aorta. 
     FIG. 3 illustrates the orientation of implants  52  inserted using dual-tube protective sleeves  40  or an embodiment of holder  100  that has an angle A value of 0 degrees. Implants  52  are shown inserted in parallel in disk space  44 . Spinal nerves within the spinal canal  46  and protective sheath  48  (also called the dura) are shown posterior to disk space  44 . Nerves  50  exit the sides of spinal canal  46 . An end  206  of an implant  52  may put pressure on nerves  50  if the implant is inserted far enough to allow ends to protrude out the posterior side  138  of disk space  44 . Pressure on the nerves may lead to severe post-operative pain or nerve damage for the patient. 
     FIG. 31 illustrates the angulation of implants inserted using one embodiment of a holder  100 . Implants  52  are shown inserted angled inwards in disk space  44 . Nerves  50  are shown exiting from the sides of spinal canal  46 . If implants  52  are inserted far enough that ends  206  protrude out the posterior side  138  of the disk space  44 , ends  206  may be more likely to put pressure on dura  48  than on nerves  50 . Dura  48  may be less likely to be negatively affected by the pressure than nerves  50 . 
     Also shown in FIG. 31 is an embodiment of a holder  100  inserted in disk space  44 . The curvature of bottom  146  of holder  100  may substantially match the curvature of the anterior surface of the adjacent vertebrae  54 . The close fit between the vertebrae  54  and the holder  100  may help protect blood vessels  198  and other soft tissues from being pinched between the vertebrae and the holder during the spinal fusion procedure. The angulation of conduits  104  is shown as angle A. Different embodiments of holder  100  may be made with a wide range of angles A to be used in spinal fusion procedures requiring different optimal angulations of implants  52 . Most procedures may fall between 0 degrees and 30 degrees. Approximately 8 degrees may be the optimal angulation for implants  52  in many procedures. 
     Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.