Abstract:
Tools for positioning an implant into the sacroiliac joint. A directional cannula includes a main body having a bore that receives the implant. A cut-out, allowing access to the joint, is formed in a leading end of the main body. A pair of parallel prongs extend from the leading end of the main body in transversely spaced apart relation to one another. A drill guide has a main body of rectangular transverse cross-section and a cylindrical head formed integrally with the main body. A transverse width-reducing step is formed in the main body near its distal end. First and second bores are formed in the cylindrical head and in the main body. Both bores are eccentric relative to the drill guide longitudinal axis of symmetry. The drill guide is rotated 180° after first and second drilling operations, prior to third and fourth drilling operations.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates, generally, to surgical instruments and methods. More particularly, it relates to a tool for introducing a fusion device, also known as an implant or fusion implant, into a sacroiliac joint. 
     2. Description of the Prior Art 
     Placing a fusion implant into the sacroiliac area is difficult because the ilium protrudes and blocks easy access to the site. Part of the ilium can be cut and removed to improve access, but such cutting weakens the ilium, extends the time required for surgery and recovery from surgery, and increases the patient&#39;s pain. 
     New tools are needed that would eliminate the need to cut the ilium. 
     However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the art how the needed tools could be provided. 
     SUMMARY OF THE INVENTION 
     The long-standing but heretofore unfulfilled need for a device that facilitates the insertion of an implant into the sacroiliac joint is now met by a new, useful, and non-obvious invention. 
     The inventive structure includes a directional cannula having a main body of elongate cylindrical extent. A bore having the shape of a spinal fusion implant is formed in the main body. That bore is also configured to receive a drill guide therein, if needed. 
     A cut-out is formed in a leading end of the main body by a radial cut, i.e., a cut that is normal to a longitudinal axis of said main body. The radial cut extends less than half-way through the main body. The cut-out is also formed by a second longitudinally-extending cut that extends from a leading end of the main body to the radial cut at a point of deepest penetration of the radial cut. 
     The implant is captured within the bore even when the implant travels to the cut-out or notch formed in the main body and is exposed to view. Since the notch has a radial depth less than the diameter of the bore, the implant is more than half-surrounded by the lumen and cannot fall therefrom. 
     A pair of parallel prongs extends longitudinally from the leading end of the main body in transversely spaced apart relation to one another. The prongs are adapted to enter the sacroiliac joint, which is the space between the ilium and sacrum. 
     The novel drill guide includes an elongate main body having a rectangular transverse cross-section, an enlarged cylindrical head formed integrally with the main body at a proximal end of the main body, and a transverse width-reducing step formed in the main body near a distal end of the main body. 
     A first longitudinally-extending bore is formed in the enlarged cylindrical head and in the main body. The first bore is eccentric relative to a longitudinal axis of symmetry of the drill guide. 
     A second longitudinally-extending bore is also formed in the enlarged cylindrical head and in the main body. The second bore is also eccentric relative to the longitudinal axis of symmetry of the drill guide and the second bore is parallel to the first bore. 
     A drill bit is sequentially placed within the first and second bores to create clearance space in the ilium when the drill guide is received within the bore of the directional cannula. The drill guide is then removed from the bore of the directional cannula, rotated one hundred eighty degrees (180°), and the drill bit is again sequentially placed within the first and second bores to create clearance space in the sacrum. 
     An important object of this invention is to facilitate the implanting of a fusion implant in the sacroiliac area. 
     A more specific object is to accomplish the first object in the absence of removing substantial parts of the ilium. 
     Another important object is to provide tools that produce consistent results from patient to patient. 
     These and other important objects, advantages, and features of the invention will become clear as this disclosure proceeds. 
     The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the disclosure set forth hereinafter and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed disclosure, taken in connection with the accompanying drawings, in which: 
         FIG. 1A  is an X-ray view depicting the first guide wire placed on the skin to identify the location of the sacroiliac joint; 
         FIG. 1B  is a diagrammatic view of a mark made on a patient&#39;s skin to indicate the position of the guide wire used to locate the sacroiliac joint in  FIG. 1A ; 
         FIG. 2A  is an X-ray view depicting the second guide wire placed on the skin to identify the superior portion of the sacroiliac joint; 
         FIG. 2B  is a diagrammatic view of a mark made on a patient&#39;s skin to indicate the position of the guide wire used to identify the superior portion of the sacroiliac joint in  FIG. 2A ; 
         FIG. 3A  is an X-ray view depicting the third guide wire placed on the skin to identify the inferior portion of the sacroiliac joint; 
         FIG. 3B  is a diagrammatic view of a mark made on a patient&#39;s skin to indicate the position of the guide wire used to identify the inferior portion of the sacroiliac joint in  FIG. 3A ; 
         FIG. 4  is a diagrammatic view of three incision points that are marked on the patient&#39;s skin after the markings in  FIGS. 1B, 2B, and 3B  have been made; 
         FIG. 5  is an X-ray view depicting a guide wire inserted through the central incision point of the three incision points of  FIG. 4 ; 
         FIG. 6A  is a perspective view of a joint locator; 
         FIG. 6B  is a side elevational view of the joint locator; 
         FIG. 6C  is a top plan view of the joint locator; 
         FIG. 7A  is a perspective view of a novel directional cannula; 
         FIG. 7B  is a top plan view of the directional cannula of  FIG. 7A ; 
         FIG. 7C  is a side elevational view of the directional cannula of  FIG. 7A ; 
         FIG. 7D  is a bottom plan view of the directional cannula of  FIG. 7A ; 
         FIG. 7E  is an end view of the leading end of the directional cannula of  FIG. 7A ; 
         FIG. 7F  is an end view of the trailing end of the directional cannula of  FIG. 7A ; 
         FIG. 7G  is a side elevational view similar to  FIG. 7C , but depicting an implant exposed to view by a notch but captured within a lumen so that it cannot fall; 
         FIG. 7H  is an end view taken along lines  7 H- 7 H in  FIG. 7G ; 
         FIG. 8A  is a perspective view of a novel drill guide; 
         FIG. 8B  is a side elevational view of the drill guide of  FIG. 8A ; 
         FIG. 8C  is an end elevational view of the leading end of the drill guide of  FIG. 8A ; 
         FIG. 8D  is an end elevational view of the trailing end of the drill guide of  FIG. 8A ; 
         FIG. 9  is a perspective view of a drill bit; 
         FIG. 10  is a perspective view of a fusion implant device; 
         FIG. 11  is a perspective view of a tamp; 
         FIG. 12A  is a front elevational diagrammatic representation of a sacrum flanked by a pair of iliums, showing two (2) sacroiliac joints; 
         FIG. 12B  is a first perspective view of the diagrammatic representation of  FIG. 12A , indicating how the iliums protrude forwardly relative to the sacrum; 
         FIG. 12C  is a second perspective view of the diagrammatic representation of  FIG. 12A ; 
         FIG. 12D  is a view like  FIG. 12C  but adding a notched cannula, showing how the notch accommodates a protruding ilium; 
         FIG. 12E  depicts the same parts as  FIG. 12D  but taken from a left perspective; 
         FIG. 12F  is the same view as  FIG. 12E  but including the drill bit; 
         FIG. 12G  is the same as  FIG. 12F  but taken from a right perspective; 
         FIG. 12H  depicts the cavity after drilling is complete and the cannula and drill bit have been withdrawn; 
         FIG. 12I  is a like  FIG. 12H  but from a different perspective; 
         FIG. 12J  depicts an implant in the drilled cavity; and 
         FIG. 12K  depicts the same structure as  FIG. 12J  but from a different perspective. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 1A-8D  depict an illustrative embodiment of the novel instrument and the novel method steps with which it is used. The sacroiliac (SI) joint of a patient is denoted as a whole by the reference numeral  10 . 
     The novel method steps include the steps of taking anterior, posterior, and lateral X-ray views of the sacroiliac (SI) area to identify the anatomy that is causing pain in a patient. 
     An entry point is established to gain access to the SI joint with an oblique (approximately thirty five degree (35°) angle) and a Ferguson angle measurement of curvature which is approximately ten to fifteen degrees (10-15°). 
     As depicted in  FIG. 1A , first guide wire  12  is placed on top of the SI joint and as depicted in  FIG. 1B , the patient&#39;s skin is marked with a first straight line  14  to indicate the position of first guide wire  12 . First straight line  14  is drawn through SI joint  10  from the superior position of the joint to the inferior position of the joint. 
     As depicted in  FIG. 2A , a second guide wire  16  is then placed over the superior section of joint  10  in intersecting relation to first guide wire  12 . As depicted in  FIG. 2B , the patient&#39;s skin is marked with a second straight line  18  to indicate the position of second guide wire  16 . 
     A third guide wire  20 , as depicted in  FIG. 3A , is then placed over the inferior section of the joint in intersecting relation to first guide wire  12 . The patient&#39;s skin, as depicted in  FIG. 3B , is marked with a third straight line  22  to indicate the position of third guide wire  20 . 
     Three incision points are then marked on the skin, as depicted in  FIG. 4 . 
     Center incision point  24  is midway between the points where the second and third lines  18  and  22  cross first line  12  and is spaced in the medial direction about three to five millimeters (3-5 mm) from first line  12 . 
     Superior incision point  26  is spaced in the medial direction about three to five millimeters (3-5 mm) from the intersection of first line  12  and second line  14 . 
     Inferior incision point  28  is spaced in the medial direction about three to five millimeters (3-5 mm) from the intersection of first line  12  and third line  22 . 
     As depicted in  FIG. 5 , a fourth guide wire  30  is inserted through center incision point  24 , with a superior/inferior angle perpendicular to the patient. The medial/lateral angle is the same as the oblique angle on the C-arm, which is approximately thirty-five degrees (35°). Fourth guide wire  30  is guided into the SI joint and an incision is made when guide wire  30  is properly positioned. 
     Joint locator  50 , depicted in  FIGS. 6A-C , is then placed over guide wire  30 , i.e., in ensleeving relation to said guide wire  30 . A surface of joint locator  50  is etched black and that black-etched surface is positioned so that it faces the ilium. 
     Directional cannula  52 , depicted in  FIGS. 7A-7G , is then placed over joint locator  50 , i.e., in ensleeving relation to said joint locator. A surface of directional cannula  52  is etched black and that black-etched surface matches the black-etched surface of joint locator  50 , i.e., the black-etched surface of directional cannula  52  is also positioned so that it faces the ilium. 
     Directional cannula  52  has a cylindrical main body  52   a  having longitudinally-extending central bore  52   b  formed therein. Central bore  52   b  has a transverse profile that matches the transverse profile of a fusion implant. A leading end of central bore  52   b  is exposed to view by cut-out or notch  52   c . Two prongs  52   d  and  52   e  extend from said leading end in transversely spaced, parallel relation to one another. Prongs  52   d  and  52   e  enter the sacroiliac joint when directional cannula  52  is in use. Barb  52   f  is formed in the leading end of main body  52   a  as depicted in  FIGS. 7B-7E . Barb  52   f  engages the sacrum to prevent slippage when prongs  52   d  and  52   e  enter into sacroiliac joint  10 . 
       FIG. 7G  depicts implant  58  that is captured within bore  52   b . Implant  58  is exposed to view because it is in the region of bore  52   b  where notch  52   c  is formed. Since the radial depth of notch  52   c  is less than half the diameter of bore  52   b , implant  58  cannot fall from bore/lumen  52   b . In other words, as indicated in  FIG. 7H , notch  52   c  creates a “C”-shaped bore where the two (2) spaced apart points of the “C” are closer together than the widest part of implant  58 , thereby retaining the implant within bore  52   b.    
     Joint locator  50  and guide wire  30  are then retracted, leaving directional cannula  52  in position. When so positioned, prongs  52   d ,  52   e  are disposed in sacroiliac joint  10 . Barb  52   f  engages the sacrum to hold directional cannula  52  in position as aforesaid. 
     Drill guide  54 , depicted in  FIGS. 8A-8D , has longitudinally extending eccentric bores  54   a ,  54   b  formed therein. Head  54   c  is enlarged relative to main body  54   d  that is rectangular in transverse section. Step  54   e  is formed where the transverse extent of main body  54   d  is reduced. Drill bit-accommodating semi-circular grooves  54   f  and  54   g  are the continuation of bores  54   a ,  54   b  and are formed in opposite sides of the leading end of drill guide  54 , said leading end being the part of main body  54   d  that extends distal of said step  54   e.    
     Drill guide  54  is inserted into the central bore or lumen of directional cannula  52  towards the sacrum to verify placement of directional cannula  52  into the SI joint. The lumen of directional cannula  52  has a profile that enables it to slidingly receive drill guide  54  in the center of the larger implant-receiving lumen. 
     Drill bit  56 , depicted in  FIG. 9 , having positive stop  56   a  is then inserted into eccentric bore  54   a  and said drill bit  56  is slid towards the sacrum until it abuts the sacrum. 
     The distance from the proximal end of head  54   c  of drill guide  54  to the lower side of positive stop  56   a  is then measured. Directional cannula  52  is properly seated in the SI joint if the measured distance is between twenty-five to thirty millimeters (25-30 mm). The proper seating can also be confirmed with a lateral X-ray view that shows the leading end of directional cannula  52  disposed flush with the sacrum. 
     Drill bit  56  is then inserted into eccentric drill guide bore  54   a  and a first cavity is created in the ilium by a first drilling, until positive stop  56   a  abuts the proximal end of directional cannula  52 . Drill bit  56  is then withdrawn from bore  54   a , placed into bore  54   b , and a second cavity is formed in the ilium by a second drilling. The second drilling continues until drill bit  56  reaches positive stop  56   a.    
     Drill guide  54  is then retracted from directional cannula  52  and rotated one hundred eighty degrees (180°). Drill bit  56  is then inserted into eccentric drill guide bore  54   a  and a first cavity is created in the sacrum by a third drilling that continues until drill bit  56  reaches positive stop  56   a . Drill bit  56  is then withdrawn from bore  54   a , placed into bore  54   b , and a second cavity is formed in the sacrum by a fourth drilling. The fourth drilling continues until drill bit  56  reaches positive stop  56   a . Drill bit  56  is then removed. 
     Due to the eccentricity of the bores and the rotation of the drill guide, all four cavities merge into a single cavity that accommodates the fusion implant. 
     When the drilling is completed, drill guide  54  is retracted from directional cannula  52  and fusion implant  58 , depicted in  FIG. 10 , is inserted into the lumen of directional cannula  52 . The chamfer is inserted downward. 
     Fusion implant  58  may take many forms and may be as simple as a dowel having a circular cross-section, i.e., the oval shape of main body  58   a , upper and lower fins  58   b ,  58   c , and the swept back leading edge  58   d  of said fins are not critical parts of the fusion implant. 
     Implant tamp  60 , depicted in  FIG. 11 , includes head  60   a  and flat, elongate main body  60   b . A positive stop, not numbered, is formed where main body  60   b  meets head  60   a . Main body  60   b  is inserted into the lumen of directional cannula  52  to advance the implant. Head  60   a  is repeatedly tamped lightly with a hammer or other suitable tool, not illustrated, until the aforesaid positive stop abuts directional cannula  52 . This should fully seat implant  58  in the SI joint, i.e., implant  58  should be countersunk into the SI joint by a distance of about three to five millimeters (3-5 mm). A lateral X-ray view is taken to confirm full deployment of implant  58 . 
     As perhaps best understood in connection with  FIGS. 7B and 7C , implant  58  emerges from bore  52   b  at cut-out or notch  52   c . Notch  52   c  has an extent or depth less than half the diameter of cylindrical main body  52   a  as depicted in  FIGS. 7C and 7E . Implant  58  is thus supported from below by the part of main body  52   a  that is not removed to form notch  52   c . The dimensions of implant  58  allow it to be inserted into bore  52   b , but prevent it from falling out upon exiting bore  52   b , i.e., upon exposure to or open communication with notch  52   c , i.e., implant  58  is supported from below by the longitudinally-extending part of notch  52   c  as perhaps best understood in connection with  FIG. 7C . Implant  58  is inside the cavity drilled into the sacrum and ilium when said implant extends beyond leading end  52   g  of cylindrical main body  52   a.    
     A guide wire is then inserted through superior incision point  26  at a superior/interior angle about forty-five degrees (45°) towards superior. The medial/lateral angle is the same as the oblique angle on the C-arm, which is approximately thirty-five degrees (35°). 
     The guide wire is then guided into the SI joint. A second incision is made when the guide wire is properly positioned. The steps that follow the first incision are then repeated, i.e., joint locator  50  is inserted over the guide wire, directional cannula  52  is paced over the joint locator, and so on. 
     The procedure is concluded by inserting a guide wire through inferior incision point  28  at a superior/interior angle about forty-five degrees (45°) towards inferior. The medial/lateral angle is the same as the oblique angle on the C-arm, which is approximately thirty-five degrees (35°). 
     The guide wire is then guided into the SI joint. A third incision is made when the guide wire is properly positioned. The steps that follow the first and second incisions are then repeated, i.e., joint locator  50  is inserted over the guide wire, directional cannula  52  is paced over the joint locator, and so on. 
       FIGS. 12A-K  provide a simplified overview of the procedure.  FIG. 12A  is a front elevational diagrammatic representation of a sacrum  70  flanked by a pair of iliums  72   a ,  72   b , showing two (2) sacroiliac joints  74   a ,  74   b  and  FIG. 12B  is a first perspective view of the diagrammatic representation of  FIG. 12A , indicating how iliums  72   a ,  72   b  protrude forwardly relative to sacrum  70 .  FIG. 12C  is a second perspective view of the diagrammatic representation of  FIG. 12A  and  FIG. 12D  is a view like  FIG. 12C  but adding notched cannula  52 , showing how notch  52   c  accommodates a protruding ilium.  FIG. 12E  depicts the same parts as  FIG. 12D  but taken from a left perspective and FIG.  12 F is the same view as  FIG. 12E  but including drill bit  56 .  FIG. 12G  is the same as  FIG. 12F  but taken from a right perspective.  FIG. 12H  depicts cavity  76  after drilling is complete and the cannula and drill bit have been withdrawn.  FIG. 12I  is a like  FIG. 12H  but from a different perspective,  FIG. 12J  depicts implant  58  in drilled cavity  76 , and  FIG. 12K  depicts the same structure as  FIG. 12J  but from a different perspective. 
     It will thus be seen that the objects set forth above, and those made apparent from the foregoing disclosure, are efficiently attained and 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 disclosure or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.