Abstract:
A method for treating back pain by stabilizing the sacroiliac joint. The method includes fusing a sacrum bone to an ilium bone or otherwise mechanically immobilizing the sacroiliac joint by inserting at least two implants into voids formed within or between the articular surfaces of each sacroiliac joint of a patient without substantially distracting the joint. The voids are arranged within each joint at either a converging orientation or a diverging orientation. A kit containing the implants and tools required to insert the implants into the joint are also described.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed to a sacroiliac joint stabilization method for treating back pain, and more particularly, to a surgical procedure for fusing the sacroiliac joint, the procedure including inserting a pair of implants between the articular surfaces of the sacroiliac joint at converging or diverging orientations in a manner that does not substantially distract the joint. 
       BACKGROUND OF THE INVENTION 
       [0002]    The sacroiliac joint is a diarthrodial joint that joins the sacrum to the ilium bones of the pelvis. In the sacroiliac joint, the sacral surface has hyaline cartilage that moves against fibrocartilage of the iliac surface. The spinal column is configured so that the weight of the upper body rests on the sacroiliac joints at the juncture of the sacrum and ilia. Stress placed on the sacroiliac joints in an upright position of the body makes the lower back susceptible to injury. 
         [0003]    Disorders of the sacroiliac joint can cause low back and radiating buttock and leg pain in patients suffering from degeneration and/or laxity of the sacroiliac joint. In some cases, the sacroiliac joint can undergo degeneration of the cartilaginous surfaces of the joint, similar to other articulating joints, which causes significant pain. The sacroiliac joint is also susceptible to trauma, with resulting degeneration, fracture or instability. It is estimated that disorders of the sacroiliac joint are a source of pain for millions of people suffering from back and radicular symptoms. 
         [0004]    Non-surgical treatments, such as medication, injection, mobilization, rehabilitation and exercise can be effective. However, they may fail to permanently relieve the symptoms associated with these disorders. Surgical treatment of these disorders includes stabilization and/or arthrodesis. Stabilization can include the use of bone screws that are directly threaded across the joint. Arthrodesis may include immobilization of a joint and the removal of all of part of the cartilage from within the joint, permitting bone growth across the joint and resulting in a permanent fusion. The present disclosure describes an improvement over these prior art technologies. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is directed to a method for treating back pain by stabilizing the sacroiliac joint. The sacroiliac joint is stabilized by fusing a sacrum bone to an ilium bone or otherwise mechanically immobilizing the sacroiliac joint. The method includes inserting at least two implants into voids formed within or between the articular surfaces of each sacroiliac joint of a patient without substantially distracting the joint. The voids are arranged within each joint at either a converging orientation or a diverging orientation. The converging or diverging orientation of the implants permits translation of the joint along the path of one of the implants, as would be possible with implants oriented in a parallel fashion. A kit containing the implants and tools required to insert the implants into the joint are also described. 
         [0006]    According to one aspect of the invention there is provided a method of stabilizing a sacroiliac joint including forming a first void and a second void within the articular surfaces of the sacroiliac joint and placing a first implant within the first void and a second implant within the second void. Each void is formed by inserting a wire into the posterior aspect of the sacroiliac joint, inserting a number of dilation tubes over the wire thereby dilating tissue and creating a posterior access to the sacroiliac joint. A drill guide having a distal end with a pair of opposing teeth is slid over or through the dilation tube and the teeth inserted into a space between the ilium bone and the sacrum bone for stabilizing the drill guide. A drill bit is then inserted through the drill guide and into the sacroiliac joint and rotated for removing a portion of the cartilaginous articulating surfaces between the ilium bone and the sacrum bone. 
         [0007]    After a void is formed, the drill bit and drill guide are removed from the dilation tube and an implant inserter device is provided. The inserter device includes a grasping member for holding an implant, a rotatable knob member and a screw member extending between the knob member and the grasping member. To insert the implant into the void, the insert and implant are passed through the dilation tube and the implant is placed at least partially within the void. The knob member is rotated to release the implant from the grasping member. A tamping device can be inserted through the dilation tube to fully seat or countersink the implant within void. A fusion promoting substance may also be passed through the dilation tube into the void. 
         [0008]    According to another aspect of the invention there is provided a method of stabilizing a sacroiliac joint including forming a first void and a second void within the articular surfaces of the sacroiliac joint with the voids arranged in a converging orientation relative to one another. In particular, the first void is arranged to extend anterocranially within a caudal segment of the articular surfaces of the sacroiliac joint from a first opening formed in a crest of the first posterior margin section of the sacroiliac joint inferior to a level of a posterior superior iliac spine. The second void is arranged to extend anterocaudally within a midsection portion of the articular surfaces of the sacroiliac joint from a second opening formed in a second posterior margin section of the sacroiliac joint at or superior to the level of the posterior superior iliac spine. 
         [0009]    Respective first and second implants are inserted into the first and second voids. The implants may be dense cancellous bone implants, the implants including a tapered distal end portion, a substantially flat proximal end face having a central protuberance extending axially therefrom and a midsection extending between the distal end portion and the proximal end face. The midsection includes a plurality of ridges configured for preventing the bone implant from backing out of the sacroiliac joint. The use of dense cancellous bone as an implant material permits and encourages bony in-growth throughout the body of the implant. When the implants are seated within the voids, it is preferred that the first implant has a longitudinal axis that crosses a longitudinal axis of the second implant at an angle ranging between 35 degrees and 55 degrees, 40 degrees and 50 degrees or 42 degrees and 47 degrees. The method of stabilizing the sacroiliac joint is performed with essentially no distraction of the sacroiliac joint by utilizing instruments provided in a kit containing the guide wire, one or more dilation tubes, a drill guide, a bone implant inserter and a drill bit having a cutting diameter that is substantially the same as the diameters of the bone implants. Preferably, the cutting diameter is about 0.5 mm less than the diameter of each bone implant. 
         [0010]    According to another aspect of the invention there is provided a method of stabilizing a sacroiliac joint including forming a first void and a second void within the articular surfaces of the sacroiliac joint with the voids arranged in a diverging orientation relative to one another. In particular, the first void is arranged to extend anterocaudally within a caudal segment of the articular surfaces of the sacroiliac joint from a first opening formed in a first posterior margin section of the sacroiliac joint at or inferior to a level of a posterior superior iliac spine. The first opening is formed through a superior surface of the caudal segment of the articular surfaces of the sacroiliac joint. The second void extends anterocranially within a cranial segment of the articular surfaces of the sacroiliac joint from a second opening formed in a second posterior margin section of the sacroiliac joint at or superior to the level of the posterior superior iliac spine. The second opening is formed through a posterior surface of the cranial segment of the articular surfaces of the sacroiliac joint. Respective first and second implants are inserted into the first and second voids with essentially no distraction of the sacroiliac joint. 
         [0011]    According to yet another aspect of the invention there is provided a method of stabilizing a sacroiliac joint including forming a first passageway extending anterocranially within the articular surfaces of the sacroiliac joint from a first opening formed in a first posterior margin section of the sacroiliac joint, forming a second passageway extending anterocaudually within the articular surfaces of the sacroiliac joint from a second opening formed in a second posterior margin section of the sacroiliac joint, and placing a first implant within the first void and a second implant within the second void. 
         [0012]    A further understanding of the nature and advantages of the present invention will be realized by reference to the remaining portions of the specification and the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a lateral view of a pelvic region showing a first implant and a second implant operatively positioned between the articular surfaces of a sacroiliac joint in accordance with a first embodiment of the present invention. 
           [0014]      FIG. 2  is a lateral view of a pelvic region showing a first implant and a second implant operatively positioned between the articular surfaces of a sacroiliac joint in accordance with a second embodiment of the present invention. 
           [0015]      FIG. 3  is a schematic view of a kit containing instruments and implants for stabilizing a sacroiliac joint. 
           [0016]      FIG. 4  is an elevational view of an implant of the kit of  FIG. 3 . 
           [0017]      FIG. 5  is a perspective view of the implant of  FIG. 4 . 
           [0018]      FIG. 6  is an elevational view of a guide wire of the kit of  FIG. 3 . 
           [0019]      FIG. 7  is an elevational view of a plurality of dilation tubes of the kit of  FIG. 3 . 
           [0020]      FIG. 8  is a distal end, perspective view of a drill guide of the kit of  FIG. 3 . 
           [0021]      FIG. 9  is a proximal end, perspective view of the drill guide according to claim  FIG. 8 . 
           [0022]      FIG. 10  is a perspective view of a drill bit of  FIG. 3 . 
           [0023]      FIG. 11  is a proximal end, perspective view of an implant inserting device of the kit of  FIG. 4 . 
           [0024]      FIG. 12  is a distal end, perspective view of the implant inserting device of  FIG. 11 . 
           [0025]      FIG. 13  is an elevational view of the implant inserting device of  FIG. 11  showing the implant grasper, retracted in a grasping arrangement. 
           [0026]      FIG. 14  is an elevational view of the implant inserting device of  FIG. 11  showing the implant grasper, extended in a releasing arrangement. 
           [0027]      FIG. 15  is a perspective view of a joint locator device of  FIG. 3 . 
           [0028]      FIG. 16  is a perspective view of placement of a k-wire into a sacroiliac joint. 
           [0029]      FIG. 17  is an elevational view of the k-wire and sacroiliac joint of  FIG. 16 . 
           [0030]      FIG. 18  is a perspective view of a first dilator inserted over the k-wire of  FIG. 16 . 
           [0031]      FIG. 19  is a perspective view of a second dilator inserted over the first dilator of  FIG. 18 . 
           [0032]      FIG. 20  is a perspective view of a third dilator inserted over the second dilator of  FIG. 19 . 
           [0033]      FIG. 21  is a perspective view of a fourth dilator inserted over the third dilator of  FIG. 20 . 
           [0034]      FIG. 22  is a perspective view of the fourth and third dilators of  FIG. 21  with the first and second dilators removed. 
           [0035]      FIG. 23  is a perspective view of a joint locator partially inserted over the k-wire of  FIG. 22 . 
           [0036]      FIG. 24  is a perspective view of the joint locator of  FIG. 23  inserted over the k-ware with a drill guide inserted between the joint locator and the fourth dilator. 
           [0037]      FIG. 25  is a perspective view of a drill guide inserted into the fourth dilator of  FIG. 22  with the k-wire and the third dilator removed. 
           [0038]      FIG. 26  is a perspective view of a drill bit being inserted into the drill guide of  FIG. 25 . 
           [0039]      FIG. 27  is a perspective of an implant inserting device engaged with a sacroiliac joint implant. 
           [0040]      FIG. 28  is a perspective view of a distal end of the implant inserting device of  FIG. 27 . 
           [0041]      FIG. 29  is a perspective view of a proximal end of the drill guide of  FIG. 25  with the implant inserting device partially inserted therein. 
           [0042]      FIG. 30  is a perspective view of the proximal end of the drill guide of  FIG. 25  with the implant inserting device fully inserted therein. 
           [0043]      FIG. 31  is a perspective view of the sacroiliac joint implant of  FIG. 27  implanted within a sacroiliac joint. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    The present invention is generally directed to a surgical procedure for stabilizing or immobilizing the sacroiliac joint. The procedure includes positioning a pair of implants within the articular surfaces of the sacroiliac joint in either a converging orientation or a diverging orientation. The procedure is carried out in a manner that minimizes distraction of the sacroiliac joint during insertion of the implants so that essentially no distraction of the joint occurs. By “essentially no distraction” it is meant less than 1 mm of distraction, preferably less than 0.6 mm of distraction, and more preferably less than about 0.5 mm of distraction, occurs between the articular surfaces of the sacroiliac joint of a patient. 
         [0045]      FIG. 1  depicts a pair of implants arranged in the converging orientation  11  within the articular surfaces of a sacroiliac joint.  FIG. 2  depicts a pair of implants arranged in the diverging orientation  13  within the articular surfaces of a sacroiliac joint.  FIGS. 3 through 15  illustrate a surgical kit  15  and the various instruments of the kit used to carry out the sacroiliac implant procedure.  FIGS. 16 through 31  illustrate the surgical steps of the procedure and, in particular, the manner in which the implants are introduce into the joint so to minimize distraction of the sacroiliac joint. 
         [0046]    Referring to  FIGS. 1 and 2 , there is depicted a sacroiliac joint including an ilium  10 , a sacrum  12  and articular surfaces  14  of ilium  10  and sacrum  12 . Ilium  10  includes a posterior superior iliac spine  16  and a posterior inferior iliac spine  18 . Articular surfaces  14  are generally L-shaped and include a caudal segment  20  having a first posterior or superior margin  22  with a first posterior crest  23  and a cranial segment  24  having a second posterior margin  26  with a second posterior crest  27 . 
         [0047]    As illustrated in  FIG. 1 , when arranged in converging orientation  11 , a first or inferior implant  28  is positioned within a first void which extends from a first opening formed through posterior crest  23  of articular surfaces  14  of caudal segment  20  at a level inferior to posterior superior spine  16 . First implant  28  is countersunk into the first void and extends anterocranially within caudal segment  20 . A second or superior implant  30  is positioned within a second void which extends from a second opening formed in second posterior margin  26  of articular surfaces  14  at or superior to the level of posterior superior iliac spine  16 . Second implant  30  extends anterocaudally within a midsection portion  32  of articular surfaces  14  that is formed between caudal segment  20  and cranial segment  24 . Preferably, second implant  30  is embedded within articular surfaces  14  such that a posterior portion of the second implant is countersunk from at least about 1 mm to about 100 mm between the articular surfaces. 
         [0048]    As illustrated in  FIG. 2 , when arranged in diverging orientation  13 , first or inferior implant  28  is positioned within a first void which extends from a first opening formed in first posterior margin  22  of articular surfaces  14  at or inferior to a level of posterior superior iliac spine  16 . First implant  28  extends anterocaudally within caudal segment  20  and is embedded within articular surfaces  14  such that a posterior portion of the first implant is countersunk from at least about 1 mm to about 100 mm between the articular surfaces. Second implant  30  is positioned within a second void which extends from a second opening formed in second posterior margin  26  of articular surfaces  14  at or superior to the level of posterior superior spine  16 . Second implant  30  extends anterocranially within cranial segment  24  and, like first implant  28 , is only partially embedded within articular surfaces  14 . 
         [0049]    Referring to  FIG. 3 , there is illustrated surgical kit  15  and the various instruments of the kit used to carry out the sacroiliac joint fusion procedure of the present invention. Kit  15  includes an enclosure  32  having a base and a removable lid. Contained within enclosure  32  are a set of at least four dilation tubes  36 , a drill guide  38 , a drill  40 , a k-wire  42 , an implant inserter  44 , and optionally, a joint locator  41 . Kit  15  may also include a bone fusion promoting substance such as bone morphogenetic protein-2 (BMP-2) or stem cell-containing material. Kit  15  may further include at least four sacroiliac joint implants or dowels  34  (including a pair of implants  28  for inferior insertion and a pair of implants  30  for superior insertion); however, in most instances, dowels  34  are stored and transported separately from kit  15 . 
         [0050]    Referring to  FIGS. 4 and 5 , each implant  34  has a generally bullet-shaped appearance with a tapered first end  46  ending in a flat portion  47  and a substantially flat second end  48  having a cylinder-shaped protuberance  50  extending axially therefrom. Implant  34  further includes a midsection having a plurality of ridges  52  extending radially out therefrom. Each ridge  52  includes a first end side  54  which slopes inwardly and toward first end  46  and a second end side  56  which is arranged normal to the axis of the implant. Plurality of ridges  52  are provided to inhibit or prevent the implants from backing out of the articular surfaces of the sacroiliac joint once inserted there between. 
         [0051]    Referring to  FIG. 6 , k-wire  42  is a sterilized, sharpened, smooth stainless steel pin. K-wires are typically used in orthopedics to hold bone fragments together or to provide an anchor for skeletal traction. K-wires are often driven into the bone through the skin using a power or hand drill. In the present invention, k-wire  42  is used in combination with a direct A-P fluoroscopic view to locate pathways through the articular surfaces of the sacroiliac joint where implants  34  are to inserted by acting as a guide for insertion of dilation tubes  36 , joint locator  41  and drill guide  38 . 
         [0052]    Referring to  FIG. 7 , dilation tubes  36  are represented by four hollow, metal tubes each having a tapered end  58 , an inner diameter and an outer diameter. The inner and outer diameters of the respective tubes  36  differ, becoming progressively larger, which allows the tubes to be snuggly arranged coaxially within one another. Dilation tubes  36  are used to progressively enlarge a pathway through the skin and tissue to the articular surfaces of the sacroiliac joint as defined by k-wire  42  by placing the tubes one at a time, starting with the smallest tube, over k-wire  42 . 
         [0053]    Referring to  FIGS. 8 and 9 , drill guide  38  includes a hollow middle section  60  having a distal end terminating in a pair of opposed acutely, pointed teeth  62 . Teeth  62  are configured to locate and maintain the distal end of drill guide  38  within the sacroiliac joint directly posterior to the articular surfaces of the joint where holes are to be drilled therein. To assist with the handling of the instrument, drill guide  38  includes a handle portion  64  having an enlarged diameter relative the outer diameter of middle section  60 . Handle portion  64  includes indentations  66  for receiving a physician&#39;s fingers and a flange portion  68 . 
         [0054]    Referring to  FIG. 10  manual drill  40  includes a shaft  66  having a distal end terminating in a drill bit  68  and a proximal end terminating in a handle  70 . Drill bit  68  has an outer diameter that, at its greatest diameter, is slightly less than the diameter of implants  36 . This ensures that when placed in the holes formed within the articular surfaces by drill bit  68 , the implants fit snuggly within the holes. 
         [0055]    Referring to  FIGS. 11 through 14 , inserter  44  is composed a hollow tube  72  having a rotatable shaft extending there through. The proximal end of the shaft is coupled to a knob  74  contained within a knob housing  76 . At the distal end of the rotatable shaft is a screw driven shaft  78  that is extendable from and retrievable into the distal end of hollow tube  72  upon the rotation of knob  74  and the rotatable shaft. An implant holder  80  having biased arms is coupled to the distal end of screw driven shaft  78 . The biased arms are arranged to spread apart when maintained outside of the confines of the distal end of hollow tube  72 . However, when retrieved into the distal end of hollow tube  72 , a tapered portion  73  of the biased arms is arranged to interact with the inner wall of the hollow tube  72  to cause the biased arm to contract. In this manner, implant holder  80  is caused to selectively hold and release implant  34 . 
         [0056]    Referring to  FIG. 16 , joint locator  41  is composed of a hollow tube  43  having a distal end terminating in a pair of spaced, projections  45 . Projections  45  are flat, generally planar and separated by an opening extending axially through tube  43 . A plurality of ridges are provided on the front and back surfaces of projections  45 . The ridges are provided for assisting a physician to locate the projections between the articular surfaces of the sacroiliac joint by tactile sensation. 
         [0057]    What follows is a detailed explanation of the procedures used to implant dowels  34  within the sacroiliac joint in accordance with the two configurations shown in  FIGS. 1 and 2  utilizing kit  15 .  FIGS. 16 through 31 , which generally illustrate this procedure, are not meant to illustrate the insertion of any particular implant type, such as an inferior implant  28  or superior implant  30 , or either the converging or diverging orientations. Rather, the figures are provided to generally describe insertion of the implants using kit  15 . 
         [0058]    Surgical Zone Identification. Using a direct A-P fluoroscopic view and a radiopaque marker such as a k-wire, the inferior margin of the sacroiliac joint at the level of the posterior inferior iliac spine is identified. This is located at approximately the level of the inferior margin of the S2 foramen and medial and superior to the superior margin of the sciatic notch. A horizontal line (HL1) is drawn through this point marking the inferior edge of the surgical zone. Thereafter, the superior margin of the sacroiliac joint is located, where the anterior and posterior projections of the joint come together. A horizontal line (HL2) is then drawn through the posterior superior iliac spine marking the superior edge of the surgical zone. The most prominent part of the posterior superior iliac spine is located via manual palpation or, if necessary, fluoroscopy, and horizontal line (HL3) is drawn through the posterior superior iliac spine. Lastly, a vertical line (VL1) may be drawn through the posterior superior iliac spine indicating the medial edge of the ilium. 
         [0059]    It is important to note that the posterior and anterior edges of the sacroiliac joint should project separately on fluoroscope, with the posterior edge projecting medially and the anterior edge projecting more laterally Preferably, the safe zone identification is made using a straight AP image, confirmed with a lateral view if desired. Angling the x-ray tube cephalad and obliquely assists in visualization of the path of the joint and discrimination of its anterior and posterior edges. 
         [0060]    Converging Implants. Inferior implant  28  insertion is initiated by locating a point on the skin approximately 1.5 cm superior to the inferior edge of the surgical zone (HL1) and 1-1.5 cm medial to the medial edge of the ilium (VL1) located and making a small (˜2.5 cm) vertical skin incision. If a bilateral sacroiliac joint fusion is planned, depending on individual patient anatomy, it is possible to achieve both fusions through a midline incision at the same level. K-wire  42  is placed through this incision and advanced towards the posterior edge of the sacroiliac joint under fluoroscopic guidance, preferably at a slight (˜10 degree) cephalad angle. Once the tip of k-wire  42  contacts bone, the edge of the joint is located and k-wire  42  advanced slightly into the joint, penetrating the ligaments and capsule. While the orientation of the joint varies between individuals, a lateral angle of 10-30% is expected, and approach at the appropriate angle will assist in obtaining access to the joint. 
         [0061]    After the position of k-wire  42  is checked via AP and lateral fluoroscopy, k-wire  42  is advanced further. The path of k-wire  42  is checked via fluorosope to ensure that it passes at least 2 cm superior to the superior margin of the sciatic notch. If not, a more cephalad angle is required or k-wire  42  should be removed so that the process can begin from again from a more superior point. K-wire  42  is then advanced to the desired depth, which may later be checked via markings on the k-wire. Alternatively, k-wire  42  can be stopped once the desired trajectory is established. In this event desired implant depth is estimated so as to ensure that there is no penetration anteriorly into the abdominal space. K-wire  42  should not be advanced past the anterior edge of the sacroiliac joint, as visualized via fluoroscopy. 
         [0062]    Once the desired k-wire depth is reached, dilators  36  are placed sequentially over k-wire  42 , confirming by both feel and fluoroscopy that each one has been advanced as closely as possible into contact with the bony margins of the joint. Once the largest dilator  36  has been placed, the second and third dilators are removed, leaving behind the largest and smallest dilators and k-wire  42 . If desired, utilizing a light source and bayoneted instruments the joint can be visually and manually explored to ensure desired placement and the avoidance of significant structures such as large tendons, nerves and vessels. Optionally, Thereafter, drill guide  38  is placed into the joint. The proper alignment of the drill guide may be determined visually prior to placement, or gentle rotation and advancement of drill guide  38  may be used to identify the appropriate alignment by feel. Once the proper alignment has been achieved, drill guide  38  is tamped firmly into the joint. 
         [0063]    At this point, the positioning of drill guide  38  and k-wire  42  is checked on A-P and lateral images. If the position of k-wire  42  is used to determine desired depth, it is checked via the markings on the k-wire. If not, an appropriate depth is selected. A sound may be used to determine the position of the drill guide vis-à-vis the joint surface, keeping in mind that the surface of the ilium is often elevated above the surface of the sacrum, which therefore marks the true beginning of the joint. To assist with confirming position of the drill guide or k-wire with the joint, a light source can be clipped to the dilation tube or drill guide and directed downward toward the joint to allow visualization of the joint, k-wire and the teeth of drill guide. Flouroscopy may also be used to check depth and placement. Preferably, the drill depth should be approximately 30 mm below the surface of the joint, allowing for an 8-10 mm countersink of the implant. 
         [0064]    Once the positioning of drill guide  38  and k-wire  42  is checked and the desired depth determined, the k-wire and small diameter dilator  36  are removed. Either a manual or power drill bit such as drill  40  is then selected and passed through drill guide  38 . Drill  40  is advanced to the desired depth as determined by the markings on the bit. Particularly with manual drill  40 , several rotations at the desired depth are needed to ensure that there are no uncut connective tissues entangling the bit. Following cutting, the drill bit is removed. If desired, a small amount of an osteoconductive materials such as DBM or ground cancellous bone may be packed into the bottom of the tunnel formed by the drill prior to placement of the implant. 
         [0065]    Once the hole is formed, implant  28  is loaded onto inserter  44 , passed through drill guide  38 , and tamped firmly into place. Implant  28  is released by turning knob  74  at the proximal end of inserter  44 , and the inserter removed. If desired, osteoconductive materials such as DBM or ground cancellous bone may be packed in to fill the remainder of the tunnel formed by the drill. With implant  28  in place, drill guide  38  and remaining dilators  36  are removed. 
         [0066]    Optionally, the initial location of the joint for placement of inferior implant  28  can be achieved via arthrogram, using an 18 gauge needle rather than k-wire  42 . Once access to the joint has been obtained, proper placement in the joint can be confirmed via injection of contrast dye. A flexible k-wire can then be advanced through the needle into the joint, following the procedures described above from this point. 
         [0067]    Superior implant  30  insertion is initiated by identifying a point on the skin approximately 1-1.5 cm superior and 1-1.5 cm medial to the posterior superior iliac spine and making a small (˜2.5 cm) vertical incision at that point. K-wire  42  is placed through this incision and advanced towards the sacroiliac joint under fluoroscopic guidance. Depending on individual anatomy, k-wire  42  is inserted at a slight (˜10 degree) caudal angle. Due to the alignment of the sacroiliac joint and the overhanging prominence of the ilium, a 25 to 35% lateral angle of approach is expected. Once bony contact is obtained, k-wire  42  is skyved off the anterior edge of the ilium until the entrance to the joint is located. Once entry into the joint has been obtained and confirmed fluoroscopically, the procedure described above for inferior implant  28  can be used for placement of superior implant  30 . For placement of superior implants  30 , depths greater than 45 mm are not recommended. 
         [0068]    Diverging Implants. Diverging implants  28  and  30  insertion is initiated by identifying the posterior superior iliac spine and making a single, small (˜2.5 cm) midline incision at the posterior superior iliac spine. Following the steps similar to those described above for insertion of inferior implant  28  of the converging implants, k-wire  42  is placed through this incision at a slightly downward angle below the posterior superior iliac spine and advanced towards the posterior margin of the caudal segment of sacroiliac joint under fluoroscopic guidance. Once the tip of k-wire  42  contacts bone, the edge of the joint is located and k-wire  42  advanced slightly into the joint, penetrating the ligaments and capsule. 
         [0069]    After the position of k-wire  42  is checked via AP and lateral fluoroscopy, k-wire  42  is advanced further. The path of k-wire  42  is checked via fluorosope to ensure that it passes at least 2 cm superior to the posterior crest of the caudal segment of the joint. K-wire  42  is then advanced to the desired depth, which may later be checked via markings on the k-wire. Once the desired k-wire depth is reached, dilators  36 , joint locator  41  and drill guide  38  are placed sequentially over k-wire  42 . Once the proper alignment has been achieved, joint locator  41  is removed, and drill guide  38  is tamped firmly into the joint. 
         [0070]    Once the positioning of drill guide  38  and k-wire  42  is checked and the desired depth determined in a similar fashion to that described for converging implants, the k-wire and small diameter dilator  36  are removed. Either a manual or power drill bit such as drill  40  is then selected and passed through drill guide  38 . The drill is advanced to the desired depth as determined by the markings on the bit. Following cutting, the drill bit is removed. Once the hole is formed, implant  28  is loaded onto inserter  44 , passed through drill guide  38 , and tamped firmly into place. Implant  28  is released by turning knob  74  at the proximal end of inserter  44 , and the inserter removed. With implant  28  in place, drill guide  38  and remaining dilators  36  are removed. 
         [0071]    Superior implant  30  insertion is initiated by adjusting upward and inserting k-wire through the same incision in a slight upward angle. The insertion point is basically right above interior implant  28 , offset just enough to avoid drilling out the hole through which implant  28  is implanted. Thus, k-wire  42  is placed through this incision and advanced towards the sacroiliac joint under fluoroscopic guidance. Once entry into the joint has been obtained and confirmed fluoroscopically, the procedure described above for inferior implant  28  can be used for placement of superior implant  30 . 
         [0072]    As will be understood by those familiar with the art, the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosures and descriptions herein are intended to be illustrative, but not limiting, of the scope of the invention which is set forth in the following claims.