Abstract:
A method for fusing a spinal sacroiliac joint The method includes the steps of locating the sacroiliac joint, retracting the soft tissue to expose the graft site, removing any bone obstructions and preparing a relatively smooth graft site horizontal to the immediate sacroiliac joint, creating a therapeutic cavity by creating a first cavity in the ilium and a second cavity in the sacrum to a predetermined depth that spans the sacroiliac joint, inserting a stabilization implant into the therapeutic cavity, and seating the implant within the therapeutic cavity at a predetermined depth.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to surgical methods and apparatus in general, and more particularly to surgical methods and apparatus for fusing sacroiliac joints. 
     2. Description of the Related Art 
     Lower back pain is a common ailment among the population and results in pain and suffering as well as loss of work time. Effective treatments for lower back pain will alleviate considerable patient suffering and provide economic benefits by reducing employee absenteeism. Until recently, many complaints of lower back pain and leg pain have been attributed to herniated discs or other injuries to the spinal column. However, extensive therapy and treatment has often been unsuccessful in alleviating such pain. Recently, it has been found that some of this lower back and leg pain can be attributed to symptomatic sacroiliac joint dysfunction or instability. 
     The sacroiliac joint is located at the juncture of the ilium, the upper bone of the pelvis, commonly called the hip bone, and the sacrum at the base of the lumbar spine, where it connects with the L5 vertebra. The function of the sacroiliac joint is the transmission of forces from the spine to the lower extremities and vice-versa. The joint is supported by a range of ligaments, including the sacroiliac ligament at the base of the joint and the anterior sacroiliac ligament at the top of the joint. 
     The sacroiliac joint has a limited range of motion. Nutation, the relative movement between the sacrum and ilium, is typically one to two degrees. Despite the limited range of motion, a patient&#39;s sacroiliac joint can become damaged resulting in hypermobility of the joint. Hypermobility is very difficult to diagnose due to the small range of motion. Therefore, lower back pain or leg pain caused by sacroiliac joint dysfunction, e.g. degenerative sacroiliitis, inflammatory sacroiliitis, iatrogenic instability of the sacroiliac joint, osteitis condensans ilii, or traumatic fracture dislocation of the pelvis, often goes misdiagnosed or undiagnosed. 
     In patients where sacroiliac joint pain is unresponsive to non-operative treatments, e.g. medication, physical therapy, chiropractic care and steroid injections, surgical stabilization is prescribed. Fusion is a surgical treatment to relieve pain generated from joint dysfunction. 
     Accordingly, it is a general objective of this invention to provide a method to deliver a device for correcting symptomatic sacroiliac joint dysfunction or instability, for enhancing stability for purposes of immobilizing a joint, and for fusing two opposed bone structures across the joint. 
     SUMMARY OF THE INVENTION 
     The long-standing but heretofore unfulfilled need for improved devices and methods for effecting sacroiliac joint fusion is now met by a new, useful, and nonobvious invention. 
     The present invention includes a surgical kit for use in a method for fusing a sacroiliac joint, preferably including a stabilization implant, a guide pin, a joint locator, dilation tubes, cutting tools such as a reamer or cannulated reamer, a drill bit, a cutter, and a punch, a novel directional cannula, a novel taping cap, a novel drill guide, and a novel implant positioner. 
     The invention further includes a method for fusing a sacroiliac joint with an implant, preferably comprising the steps of locating the sacroiliac joint, inserting a guide pin or a joint locator into the sacroiliac joint normal to the immediate bone surfaces on either side of the joint, retracting soft tissue via dilation tubes, sliding a cannulated reamer over the guide pin or the joint locator until a distal end of the reamer engages the sacroiliac joint creating a relatively flat graft site, removing the reamer and guide pin or joint locator, inserting a directional cannula into the sacroiliac joint aligning the teeth located on the distal end of the cannula with the plane of the joint, tapping a proximal end of the directional cannula to reversibly secure the alignment teeth into the sacroiliac joint, inserting the drill guide into the directional cannula, inserting a drill bit through the drill guide and drilling a cavity within the sacroiliac joint to a predetermined depth, removing the drill bit from within the drill guide, removing the drill guide from within the directional cannula, inserting the implant through the directional cannula until the distal end of the implant engages the cavity, inserting an implant positioner to seat the implant at a prescribed depth completely within the cavity, proportionately distributed in the sacrum and ilium, removing the implant positioner from within the directional cannula, removing the directional cannula, and removing the dilation tube. 
     These and other features of the invention will become apparent from the following detailed description of the preferred embodiments of the invention. 
     The present invention includes a novel apparatus for effecting sacroiliac joint fusion. The novel structure includes a sacroiliac joint stabilization implant for disposition between the opposing articular surfaces of a sacroiliac joint to immobilize the sacroiliac joint and facilitate fusion between the sacrum and ilium. 
     More particularly, in one form of the present invention, the novel sacroiliac joint stabilization implant includes an elongated body having a distal end, a proximal end and a longitudinal axis extending between the distal end and the proximal end. The elongated body has a cross-sectional profile characterized by a primary axis and a secondary axis, and at least one stabilizer extending radially outwardly from the elongated body in the secondary axis. 
     The elongated body has a length along the primary axis which is less than the combined width of the sacrum and ilium making up a sacroiliac joint, and at least one stabilizer has a width that is sized to make a press fit into the gap between the sacrum and ilium making up a sacroiliac joint. 
     A novel method for fusing a sacroiliac joint includes the steps of providing a sacroiliac joint stabilization implant having an elongated body having a distal end, a proximal end and a longitudinal axis extending between the distal end and the proximal end. The method further includes the steps of providing the elongated body with a cross-sectional profile characterized by a primary axis and a secondary axis and providing at least one stabilizer that extends radially outwardly from the elongated body in the secondary axis. 
     The method steps further include the steps of forming the elongated body so that it has a length along the primary axis which is less than the combined width of the sacrum and the ilium making up a sacroiliac joint and forming the at least one stabilizer so that it has a width sized to make a press fit into the gap between the sacrum and ilium making up a sacroiliac joint. 
     Further method steps include the steps of deploying the sacroiliac joint stabilization implant in the sacroiliac joint so that the elongated body is simultaneously positioned within the sacrum and ilium of the sacroiliac joint and so that the at least one stabilizer is positioned within the gap between the sacrum and ilium and maintaining the sacroiliac joint stabilization implant in such position while fusion occurs. 
     Still further steps include deploying the stabilization implant in the joint so that the elongated body is simultaneously positioned within both of the bones of the joint and at least one stabilizer is positioned within the gap between the bones and maintaining the stabilization implant in this position while fusion occurs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and features of the present invention will be more fully disclosed by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
         FIG. 1  illustrates a stabilization implant formed in accordance with the present invention; 
         FIG. 2  is a perspective view of a sacroiliac joint; 
         FIG. 3A  is a close-up perspective view of said sacroiliac joint and a drilled, bored, punched, or cut cavity; 
         FIG. 3B  is a close-up perspective view of said sacroiliac joint and said stabilization implant in the final position in the sacroiliac joint; 
         FIG. 4  is a perspective view of a guide pin; 
         FIG. 5  is a perspective view of a joint locator; 
         FIG. 6  is a perspective view of four dilation tubes of increasing diameters; 
         FIG. 7  is a perspective view of a cannulated reamer; 
         FIG. 8  is a perspective view of a novel directional cannula; 
         FIG. 9  is a perspective view of a novel tapping cap; 
         FIG. 10  is a perspective view of a novel drill guide; 
         FIG. 11  is a perspective view of a drill bit; 
         FIG. 12  is a perspective view of a novel implant positioner; 
         FIG. 13  is a perspective view of said dilation tubes positioned over said sacroiliac joint; 
         FIG. 14  is a perspective view of a said dilation tubes with said joint locator ensleeved within a lumen of the smallest diameter dilation tube; 
         FIG. 15  is a perspective view of said cannulated reamer ensleeved within the lumen of the largest diameter dilation tube, sliding over said joint locator; 
         FIG. 16  is a perspective view of a relatively flat graft site created horizontal to said sacroiliac joint; 
         FIG. 16A  is a longitudinal sectional view of said graft site of  FIG. 16 ; 
         FIG. 17  is a perspective view of said directional cannula ensleeved within the lumen of said largest diameter dilation tube; 
         FIG. 17A  is a longitudinal sectional view of the distal end of the said directional cannula positioned in the sacroiliac joint of  FIG. 17 ; 
         FIG. 18  is a perspective view of said drill guide ensleeved in the lumen of said directional cannula with a non-centered guide hole positioned over an ilium bone; 
         FIG. 19  is a perspective view of said drill guide rotated 180 degrees and subsequently ensleeved in the lumen of said directional cannula with said non-centered guide hole now positioned over a sacrum bone; 
         FIG. 20  is a perspective view of said sacrum and ilium bones and a drilled, bored, punched, or cut cavity formed in said sacroiliac joint; 
         FIG. 21  is an exploded perspective view of said stabilization implant being loaded into said directional cannula; 
         FIG. 22  is a perspective view of said implant and said implant positioner ensleeved in the lumen of the directional cannula prior to final position; and 
         FIG. 23  is a perspective view of said stabilization implant in the final position in said sacroiliac joint. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , it will there be seen that the novel sacroiliac stabilization implant, disclosed further in U.S. Pat. No. 8,162,981 to Vestgaarden, entitled “Method and Apparatus for Spinal Facet Fusion,” incorporated herein by reference, is denoted as a whole by the reference numeral  5 . Stabilization implant  5  generally includes body  10  and at least one stabilizer  15 . 
     Body  10  is an elongated element having structural integrity. Preferably the distal end of body  10  (and the distal end of stabilizer  15  as well) is chamfered as shown at  20  to facilitate insertion of fusion implant  5  into the sacroiliac joint. Preferably, as depicted in  FIG. 1 , body  10  has a rounded rectangular cross-section, or an ovoid cross-section, a laterally-extended cross-section, or some other non-round cross-section, so as to inhibit rotation of body  10  about a longitudinal center axis. 
     At least one stabilizer  15  is received in the gap located between the opposing sacroiliac surfaces to prevent rotation of stabilization implant  5  within the sacroiliac joint. In one preferred embodiment of the invention, two stabilizers  15   a  and  15   b  are provided, one disposed along the upper surface of body  10  and one disposed along the lower surface of body  10 . Stabilizers  15  preferably have a width just slightly larger than the gap between the opposing articular surfaces of a sacroiliac joint so that the stabilizers can make a snug fit therebetween. 
     Stabilization implant  5  is inserted into a sacroiliac joint using a posterior approach. The posterior approach is familiar to spine surgeons, thereby providing an increased level of comfort for the surgeon. 
     In use, and referring now at  FIG. 2 , an instrument is first used to determine plane  40  of sacroiliac joint  60 . Identifying the plane of the sacroiliac joint is important, since this is used to identify the proper position for cavity  45  ( FIG. 3A ) which is to be formed across the sacroiliac joint to receive stabilization implant  5 . 
     At least one of the instruments includes a directional feature which is used to maintain the alignment of the instrumentation with the plane of the sacroiliac joint. A directional cannula may include a flat portion and the remaining instruments may include a flat portion on an opposite portion of the instrument so that the instruments may only be inserted through the cannula at zero degrees (0°), one hundred eighty degrees (180°), or both. 
     The directional cannula provides the passageway for the placement and insertion of a stabilization device, as well as for performing drilling/cutting or other preparatory work for appropriate stabilization device embodiments. 
     The directional cannula can have an interior central passage of a circular cross section, oval cross section, rectangular cross section or other desired shape that provides the desired guide channel to deliver a stabilization device into cavity  45 . 
     After the proper position for cavity  45  has been identified, a drill (or reamer, punch, dremel, router, burr, etc.) is used to form cavity  45  in sacroiliac joint  60 . Cavity  45  is formed across plane  40  so that substantially one-half of cavity  45  is formed in sacrum  50 , and substantially one-half is formed in ilium  55 . In the claims that follow, cavity  45  is referred to as the therapeutic cavity. The part of the therapeutic cavity formed in the ilium is referred to as the first cavity and the part of the therapeutic cavity formed in the sacrum is called the second cavity. The therapeutic cavity is defined as including the first and second cavities as well as the sacroiliac joint space. Accordingly, the first cavity is recited as being in open communication with the sacroiliac joint space and the second cavity is recited as being in open communication with the sacroiliac joint space as well. The provision of the therapeutic space enables the insertion of a stabilizer in the therapeutic space while maintaining the iliac and the sacrum in their natural positions, thereby eliminating the prior art method of forcing the sacrum and iliac to move away from one another by employing a wedge-like device that forcibly increases the sacroiliac joint space. 
     After cavity  45  has been formed in (or, perhaps more literally, across) the sacroiliac joint  60 , and now referring to  FIG. 3B , stabilization implant  5  is inserted into cavity  45 . More particularly, stabilization implant  5  is inserted into cavity  45  so that (i) main body  10  spans the gap between opposing sacrum  50  and ilium  55 , and (ii) stabilizers  15  extend between the opposing sacrum and ilium surfaces. Preferably, stabilization implant  5  is slightly oversized relative to cavity  45  so as to create a press fit. Stabilization implant  5  provides the stability and strength needed to immobilize the sacroiliac joint  60  while fusion occurs. Due to the positioning of stabilizers  15  between the opposing sacrum and ilium surfaces, and due to the non-circular cross-section of main body  10 , stabilization implant  5  is held against rotation within cavity  45 , which will in turn holds sacrum  50  and ilium  55  stable relative to one another. 
     Detailed Surgical Technique 
     A preferred surgical technique for using stabilization implant  5  employs guide pin  100  ( FIG. 4 ), joint locator  105  ( FIG. 5 ), dilation tubes  110 - 113  ( FIG. 6 ), cannulated reamer  120  ( FIG. 7 ), directional cannula  130  ( FIG. 8 ), tapping cap  135  ( FIG. 9 ), drill guide  140  ( FIG. 10 ), drill bit  150  ( FIG. 11 ), and implant positioner  160  ( FIG. 12 ) 
     First, the sacroiliac joint is localized indirectly by fluoroscopy, or directly by visualization during an open procedure. A path through soft tissue to the sacroiliac joint is then created via surgeon&#39;s preference, such as open, minimally-invasive, percutaneous, or arthroscopic. 
     A set of dilation tubes  110 - 113  ( FIG. 13 ) having increasing diameters is then inserted into the soft tissue opening in sequence of increasing diameters to sufficiently retract the soft tissue exposing a graft site. 
     Next, joint locator  105  ( FIG. 14 ) is slid into a lumen of dilation tube  110  until blade  106  engages sacroiliac joint  60  and is aligned with joint plane  40 . Then joint locator  105  is lightly tapped so as to insert joint locator blade  106  into sacroiliac joint  60  until positive stop  107  is engaged. 
     Next, internal dilation tubes  110 - 112  are removed from within the lumen of dilation tube  113 . 
     Cannulated reamer  120  is then slid over joint locator  105  to remove any bone obstructing the joint and to prepare the graft surface for receiving directional cannula  130  and stabilization implant  5  ( FIG. 15 ). The distal end of reamer  120  is advanced until it sufficiently engages sacroiliac joint  60 , thereby preparing a relatively flat graft surface perpendicular to sacroiliac joint  60  ( FIGS. 16 and 16A ). The position of reamer  120  and joint locator  105  is verified by viewing the coronal and sagittal planes. 
     Reamer  120  and joint locator  105  are then removed from within the lumen of dilation tube  113 . 
     Next, directional cannula  130  is inserted into the lumen of dilation tube  113  until a distal end of cannula  130  engages sacroiliac joint  60  ( FIG. 17 ). Directional cannula teeth  131  are then aligned with plane  40  of sacroiliac joint  60 . Once teeth  131  of cannula  130  are aligned with plane  40 , directional cannula  130  is lightly tapped to insert cannula teeth  131  into sacroiliac joint  60  until positive stop  132  engages sacroiliac joint  60  ( FIG. 17A ). 
     Drill guide  140  is then inserted into a lumen of directional cannula  130  with non-centered guide hole  141  positioned over iliac bone  55  ( FIG. 18 ). Drill guide  140  is advanced within the lumen of directional cannula  130  until drill guide  140  reaches a mechanical stop on directional cannula  130 . Then, with drill guide  140  in place, irrigation fluid (e.g., a few drops of saline) is placed into the drill guide hole  141  positioned over iliac bone  55 . Next, drill bit  150  is inserted into guide hole  141  and used to drill a cavity in iliac bone  55 . Drilling continues until drill bit  150  reaches a mechanical stop on drill guide  140 . Then drill bit  150  is removed from the lumen of guide hole  141 . Next, with drill guide  140  remaining in position, irrigation fluid (e.g., a few drops of saline) is placed into central guide hole  142  of drill guide  140 . Drill bit  150  is then inserted in a lumen of guide hole  142  and used to drill a cavity in sacroiliac joint  60 , between sacrum  50  and ilium  55 . Next, drill bit  150  is removed from the lumen of guide hole  142 . Drill guide  140  is then removed from the lumen of directional cannula  130 . 
     Drill guide  140  is rotated 180 degrees, and is reinserted into the lumen of directional cannula  130  in order to drill sacrum  50  ( FIG. 19 ). With drill guide  140  in place, irrigation fluid (e.g., a few drops of saline) is placed into drill guide hole  141 , now positioned over sacrum  50 . Next, drill bit  150  is inserted into the lumen of guide hole  141  and used to drill a cavity in sacrum bone  50 . Drilling continues until drill bit  150  reaches a mechanical stop on drill guide  140 . Then drill bit  150  is removed from the lumen of guide hole  141 . Next, with drill guide  140  remaining in position, irrigation fluid (e.g., a few drops of saline) is placed into central guide hole  142  of drill guide  140 . Next, drill bit  150  is inserted into guide hole  142  and used to drill a cavity in sacroiliac joint  60 , between sacrum  50  and ilium  55 . Next, drill bit  150  is removed from guide hole  142  and drill guide  140  is removed from the lumen of directional cannula  130 . 
     This procedure creates cavity  45  ( FIG. 20 ) that is sufficiently deep and that is proportionately distributed in sacrum  50  and ilium  55  to receive stabilization implant  5 . 
     Stabilization implant  5  is then inserted, distal end first, into the lumen of directional cannula  130  ( FIG. 21 ). Next, implant positioner  160  is inserted into the lumen of directional cannula  130  and advanced until resistance is felt, indicating that the distal end of implant  5  has engaged cavity  45  ( FIG. 22 ). Next, implant positioner  160  is lightly tapped to drive implant  5  into cavity  45  created laterally across sacroiliac joint  60  ( FIG. 23 ). Stabilization implant  5  is preferably countersunk 1-2 mm into sacroiliac joint  60 . 
     Finally, implant positioner  160  and directional cannula  130  are removed from the lumen of dilation tube  113 . Dilation tube  113  is then removed from the soft tissue and the incision is closed. 
     The foregoing steps are repeated for additional locations in the current sacroiliac joint  60  and in contralateral sacroiliac joint  60 . 
     Alternative Surgical Technique 
     First, sacroiliac joint  60  is localized indirectly by fluoroscopy, or directly by visualization during an open procedure. Guide pin  100  is inserted into sacroiliac joint  60 , normal to immediate opposing joint surfaces when sacroiliac joint  60  is exposed, or drilled into joint  60  through the iliac crest when sacroiliac joint  60  is obstructed. The position of guide pin  100  is determined by viewing the coronal and sagittal planes. Guide pin  100  is then lightly tapped to insert guide pin  100  approximately 15-20 mm into sacroiliac joint  60 , along joint plane  40  ( FIG. 3A ) 
     Next, a set of dilation tubes  110 - 113  ( FIG. 6 ) having increasing diameters is slid over guide pin  100  into the soft tissue in sequence of increasing diameters to sufficiently retract soft tissue exposing a graft site ( FIG. 13 ). Once a sufficient surgical area is exposed, internal dilation tubes  110 - 112  are removed from within the lumen of dilation tube  113 . 
     Next, referring to  FIG. 15 , cannulated reamer  120  is slid over guide pin  100  within the lumen of dilation tube  113  to remove any bone obstructing sacroiliac joint  60  and to prepare the graft surface for receiving directional cannula  130  and fusion implant  5 . The distal end of reamer  120  is advanced until it sufficiently engages sacroiliac joint  60 , thereby preparing a relatively flat graft surface perpendicular to sacroiliac joint  60  ( FIGS. 16A and 16B ). The position of reamer  120  is verified by viewing the coronal and sagittal planes. 
     Next, reamer  120  and guide pin  100  are removed from within the lumen of dilation tube  113 . 
     The previously disclosed steps of removing reamer  120  and joint locator  105  from within the lumen of dilation tube  113  through removing implant positioner  160  and directional cannula  130  from the lumen of dilation tube  113 , removing dilation tube  113  from the soft tissue, and closing the incision are followed to complete the procedure. 
     Numerous advantages are achieved by the present invention. For example, the present invention provides a fast, simple, minimally-invasive and easily reproduced approach for effecting sacroiliac joint fusion. 
     While stabilization implant  5  has been disclosed above in the context of fusing a sacroiliac joint, it should also be appreciated that stabilization implant  5  may be used to stabilize and fuse any joint having anatomy similar to the sacroiliac joint, i.e., a pair of opposing bony surfaces defining a gap therebetween, with the stabilizer of the stabilization implant being sized to be positioned within the gap. By way of example but not limitation, the stabilization implant may be used in small joints such as the fingers, toes, etc. 
     It should be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention may be made by those skilled in the art while still remaining within the principles and scope of the invention. 
     It will be seen that the advantages set forth above, and those made apparent from the foregoing description, are efficiently attained. Since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.