Patent Abstract:
Methods and apparatus for arthroscopic tenodesis using sockets in bone created by retrograde cutting. A cannulated pin is drilled through bone and into a joint space in the normal, antegrade direction, guided by a drill guide. A strand provided through the cannulated pin is used to draw a retrodrill cutter into the joint space. The retrodrill cutter is threaded onto the cannulated pin, which is turned for retrograde cutting of a socket into the bone. The method is used to form a pair of sockets in the joint, which accept the respective ends of a replacement graft. The graft is brought into position in the joint space using loops formed in the strands, in a manner similar to introduction of the retrodrill cutter. The reconstruction is completed by securing suture attached to the graft ends with a button implant installed at the bone surface.

Full Description:
This application claims the benefit of U.S. Provisional Application No. 60/455,391 filed Mar. 18, 2003, and U.S. Provisional Application No. 60/465,221, filed Apr. 25, 2003. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of surgery and, more particularly, to methods of reconstructive knee surgery. 
     BACKGROUND OF THE INVENTION 
     Methods of anterior cruciate ligament (ACL) reconstruction (tenodesis) using interference screw fixation are described, for example, in U.S. Pat. Nos. 5,211,647 and 5,320,626. In general, these methods of tenodesis involve drilling a tunnel through the tibia, drilling a closed tunnel (socket) into the femur, inserting a substitute ACL graft into the tunnels, and securing the grafts to the walls of the tibial and femoral tunnels using interference screws or the like. Accurate positioning of the tibial and femoral tunnels is accomplished using a drill guide, examples of which are disclosed in U.S. Pat. Nos. 5,269,786 and 5,350,383, incorporated herein by reference. 
     One drawback of the described tenodesis methods is that forming the tibial tunnel involves removal of significant amounts of bone material. U.S. Pat. No. 5,603,716 to Morgan et al. discloses a technique for ACL reconstruction that avoids the above-noted problem by forming sockets in both the femur and the tibia using a coring bone harvester. The harvester is impacted into bone to a desired depth so that bone material collects as a bone core within the harvester tube. The bone core is extracted from the bone socket using a simultaneous twisting and pulling motion. Such harvesting of bone cores in the joint is technically difficult. 
     Accordingly, the need exists for a method of ACL reconstruction that provides tibial socket formation without the need for extracting a bone core to form a bone socket. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages of the prior art and fulfills the needs noted above by providing techniques and apparatus for creating bone sockets by drilling in a retrograde manner. 
     According to one embodiment of the present invention, an apparatus for anterior cruciate ligament (ACL) reconstruction in a retrograde manner is provided in the form of a retrodrill cutter detachable from a retrodrill pin. The retrodrill cutter has a cannulated body provided with a plurality of cutting flutes. The retrodrill pin has a proximal end and a distal end, and a body provided with depth calibration markings. The distal end of the retrodrill pin is threaded for engagement with corresponding threads in the cannulation of the retrodrill cutter. 
     According to one embodiment of the present invention, anterior cruciate ligament (ACL) reconstruction is performed by creating femoral and tibial sockets created using a retrograde drilling technique. Retrodrill cutters are applied in a retrograde manner to drill into the femur and the tibia and create the femoral and tibial sockets, respectively. 
     The cutters are driven using thin (3 mm) retrodrill pins provided with depth markings. The proper anatomical positions inside the joint for creating the sockets are located, and precise alignment of the sockets is achieved using a C-ring drill guide. The cannulated retrodrill pin is inserted into a guide sleeve of the drill guide and drilled through the bone in the normal direction (antegrade) until contact is made with a marking hook of the drill guide, thus forming a narrow transosseous tunnel. A trocar is inserted into the cannulated retrodrill pin to form a pointed drill tip. The drill guide marking hook ends in a hook tip that is placed in the joint, and a mark 5 mm proximal of the hook tip is used to align the retrodrill pin. 
     A strand inserted through the cannulated retrodrill pin is retrieved through a surgical portal. The strand is attached to the retrodrill cutter, which is drawn into the joint by pulling the strand, assisted by a grasper or a shoehorn cannula. The retrodrill cutter is placed into the anatomical joint space and positioned so that the cannulated retrodrill pin can be threaded into the retrodrill cutter. Once secured to the retrodrill cutter, the retrodrill pin is rotated and retracted through the joint surface and into bone to the proper depth as measured on the outside of the knee by the depth markings on the retrodrill pin. After each socket is formed, the retrodrill cutter is removed from the retrodrill pin by applying a reverse drilling motion to the retrodrill pin while grasping the cutter. The retrodrill pins are left in position for use in subsequent surgical steps. 
     A graft, such as a composite femoral bone/tendon allograft, is prepared to have a diameter corresponding to the diameter of the femoral and tibial sockets. The length of the graft equals the sum of the lengths of the femoral and tibial sockets plus the joint space distance between the two socket openings. Loops formed in the strands are pulled out through a surgical portal and connected to the ends of the graft. The strands are pulled, drawing the ends of the graft into the joint. The loops of the strands will not pass through the cannulated retrodrill pins and instead are drawn out as the retrodrill pins are retrograded by hand with a Jacob&#39;s chuck handle, for example, pulling the strands through the respective transosseous tunnels. The graft is drawn into the joint, with the assistance of a shoehorn slotted cannula or an ACL grasper, until the ends of the graft are positioned fully into the sockets. 
     Once the graft has been pulled fully into the femoral and tibial sockets, graft tensioning and fixation are carried out. Fixation preferably is carried out by securing the strands using a button implant inserted into the openings of the narrow tunnels at the bone surface. 
     Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A–1C  illustrate a retrodrill cutter according to the present invention; 
         FIGS. 2A and 2B  illustrate a retrodrill pin according to the present invention; 
         FIG. 3  schematically illustrates an initial stage in the formation of a femoral socket according to the present invention; 
         FIG. 4  schematically illustrates the formation of a femoral socket at a stage subsequent to that shown in  FIG. 3 ; 
         FIG. 5  schematically illustrates the formation of a femoral socket at a stage subsequent to that shown in  FIG. 4 ; 
         FIG. 6  schematically illustrates the formation of a femoral socket at a stage subsequent to that shown in  FIG. 5 ; 
         FIG. 7  illustrates a grasper employed in connection with the retrodrill cutter of the present invention; 
         FIG. 8  schematically illustrates the formation of a femoral socket at a stage subsequent to that shown in  FIG. 6 ; 
         FIG. 9  schematically illustrates the formation of a femoral socket at a stage subsequent to that shown in  FIG. 8 ; 
         FIG. 10  schematically illustrates an initial stage in the formation of a tibial socket according to the present invention; 
         FIG. 11  schematically illustrates the formation of a tibial socket at a stage subsequent to that shown in  FIG. 10 ; 
         FIG. 12  illustrates a graft to be employed in connection with a femoral and tibial sockets of the present invention, and in accordance with a method of graft fixation of the present invention; 
         FIG. 13  illustrates a schematic view of a knee joint undergoing graft insertion according to an embodiment of the present invention; 
         FIG. 14  is a close-up illustration of the knee joint of  FIG. 13  at a stage of graft insertion and fixation subsequent to that shown in  FIG. 13 ; 
         FIG. 15  is a close-up illustration of the knee joint of  FIG. 13  at a stage of graft insertion subsequent to that shown in  FIG. 14 ; 
         FIG. 16  is a close-up illustration of the knee joint of  FIG. 13  at a stage of graft insertion subsequent to that shown in  FIG. 15 ; 
         FIG. 17  is a close-up illustration of the knee joint of  FIG. 13  at a stage of graft insertion subsequent to that shown in  FIG. 16 ; 
         FIG. 18  illustrates a schematic view of a knee joint having undergone graft insertion and prior to graft fixation according to an embodiment of the present invention; 
         FIG. 19  illustrates a schematic view of a knee joint having undergone graft insertion and fixation according to an embodiment of the present invention; and 
         FIGS. 20A–20C  illustrate a button implant and driver used to securely fixate the inserted graft. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides retrodrill techniques and apparatus for forming femoral and tibial bone sockets in a retrograde manner during ligament reconstruction, for example, anterior cruciate ligament (ACL) reconstruction. The present invention also provides methods of graft preparation, insertion and fixation employed in connection with the femoral and tibial sockets of the present invention. 
     Referring now to the drawings, where like elements are designated by like reference numerals,  FIGS. 1–2  illustrate a retrodrill cutter  10  ( FIGS. 1A–1C ) which is adapted to be threadingly engaged with a cannulated retrodrill pin  50  ( FIGS. 2A–2C ). 
     Referring to  FIGS. 1A–1C , the retrodrill cutter  10  features a cylindrical body  11  having a plurality of cutting teeth  12  radiating symmetrically. A cannulation  13  through body  11  is provided with internal screw threads  14 . Cutting teeth  12  have edges extending radially from cannulation  13  on a proximal cutting face  15 , seen in plan view in  FIG. 1A . The edges of cutting teeth  12  continue axially along the side of the retrodrill cutter  10 , which is oriented orthogonally to proximal cutting face  15 . The edges end at a smooth, rounded distal end  16  of retrodrill cutter  10 . Retrodrill cutter  10  is provided in a selected diameter corresponding to graft size as discussed further below. 
     Referring to  FIGS. 2A–2B , retrodrill pin  50  features a fluted region  51  formed on distal end  52  of cannulated body  53 , as shown in detail in  FIG. 2B . Cannulated body  53  has a proximal end  54 . The cannulated body  53  is provided with screw threads  55  at distal end  52 . The screw threads  55  are fashioned to engage corresponding threads  14  of retrodrill cutter  10 . Accordingly, the outer diameter of threaded region  55  closely approximates the diameter of cannula  13  of the retrodrill cutter  10 , to allow secure engagement of the outer threaded region  55  with the inner threads  14  of retrodrill cutter  10 . 
     Retrodrill pin  50  features visible calibrated depth markings  56  lazed onto the cannulated body  53 . Between threads  55  and depth markings  56 , a shoulder  57  is formed to provide a stop where threads  55  end. The lumen of cannulated body  53  accepts a trocar  58  having a pointed tip  59 . When the trocar is removed, a strand can be passed through the lumen of the cannulated body  53 , as described below in greater detail. The proximal end  54  of cannulated body  53  is configured for chucking into a rotary driver (not shown). The distal end  52  of cannulated body  53  is open at the tip to expose the pointed end  59  when the trocar  58  is inserted into the cannulated body  53 , as when drilling the assembled retrodrill pin  50  into bone. Retrodrill pin  50  includes a setscrew collar  62  for securing the trocar  58  in the cannulated body  53 . 
     An exemplary method of using the retrodrill pin  50  and the retrodrill cutter  10  to create a femoral socket  100  of the present invention is described below with reference to  FIGS. 3–9 , which illustrate a schematic anterior view of a knee in which ACL reconstruction is performed according to the present invention. In the following embodiment, a femoral socket  100  (shown completed in  FIG. 9 ) is formed in a femur  66 . 
     Referring to  FIG. 3 , femoral tunnel alignment is obtained using a long adapter drill guide  70 , such as an Arthrex C-Ring cross-pin drill guide, which is disclosed in U.S. Pat. Nos. 5,350,383 and 5,918,604, the disclosures of which are incorporated by reference. The drill guide  70  is secured to the lateral thigh, over femur  66  and lateral to intercondylar notch  67 , as shown in  FIG. 3 . Sleeve  78  of the adapter drill guide  70  is placed through a lateral portal A and marking hook  72  is hooked in the “over-the-top” position. Hook  72  includes a laser mark  74  located 5 mm proximate (anterior) to tip  73  of the marking hook  72 , to ensure placement of the retrodrill pin  50  anterior to the intercondylar notch  67 . 
     Once the anatomical position in the joint for the femoral socket has been identified, and the appropriate drilling angle has been selected on the drill guide  70 , femoral retrodrill pin  50 , with the installed trocar  58 , is inserted through sleeve  78 , as shown in  FIG. 3 . The femoral retrodrill pin  50  is drilled through the lateral femur until contact is made with the marking hook  72  of long adapter drill guide  70 . 
     Referring to  FIG. 4 , drill guide  70  is removed, and a strand  63 , preferably a stiffened suture such as FiberStick (a high strength suture product with a stiff tip, sold by the assignee, Arthrex, Inc.), or a wire, is inserted through the retrodrill pin  50  into the joint space  68 . A suture retriever is introduced to retrieve the inserted end of the strand  63  and pull it out through a medial portal. The strand  63  is placed through the cannula  13  of the retrodrill cutter  10  and retained using a Mulberry knot  19  tied in the strand on the rounded distal side  16  of the retrodrill cutter  10 , as shown in  FIG. 5 . The strand  63  is pulled in the direction of arrow “P” of  FIG. 5  to draw the retrodrill cutter  10  through the medial portal and into the joint space  68 . Proper orientation of the retrodrill cutter  10  can be achieved using a grasper  44  ( FIG. 7 ) or a shoehorn cannula. The retrodrill cutter  10  is positioned to be threaded onto the femoral retrodrill pin  50  by turning and advancing the retrodrill pin  50  in the relative direction of arrow F ( FIG. 6 ) (antegrade) into the cannulation  13  of retrodrill cutter  10 . 
     Referring to  FIG. 8 , once securely engaged within the retrodrill cutter  10 , the retrodrill pin  50  is rotated with a power driver (not shown) and retracted (retrograde) to cut through the femoral joint surface and into bone to create femoral socket  100 . A desired depth D 1 , preferably 25 mm., is obtained by reading the markings  56  on the femoral retrodrill pin  50 , recorded relative to the skin femoral surface prior to and during socket formation. 
     Once the desired socket depth is achieved, the retrodrill cutter  10  is pushed distally (antegrade) out of the socket and back into the joint space  68 . Using an instrument such as grasper  44  ( FIG. 7 ) to hold the retrodrill cutter  10 , the retrodrill pin  50  is unscrewed from the retrodrill cutter  10  in the direction of arrow R of  FIG. 8 , and the retrodrill cutter  10  removed from the joint space through the medial portal, leaving retrodrill pin  50  in position as illustrated in  FIG. 9 . Strand  63  also remains and, during removal of retrodrill cutter  10 , acts as a safety line should the retrodrill cutter  10  become lost or disengaged from the grasper  44  during removal. 
     Subsequent or prior to the formation of the femoral socket  100 , a tibial socket  200  (shown completed in  FIG. 11 ) is formed by a method similar to that described above for the formation of the femoral socket  100 . Accordingly, anatomical position and alignment are established for creation of the tibial socket  200  using the drill guide  70 . Tibial retrodrill pin  150  is inserted through guide sleeve  78 , as shown in  FIG. 10 . The tibial retrodrill pin  150 , with inserted trocar, is drilled through the tibia  60  until contact is made with the marking hook  72  of long adapter drill guide  70 . With the retrodrill pin in position, the guide  70  is removed from pin  150 , which remains in place in the small tibial tunnel. 
     Creation of the tibial socket  200  continues in a manner similar to that for creating femoral socket  100 . The trocar is removed from retrodrill  150 , and is replaced by a stiffened suture strand  163 , preferably FiberStick. A grasper  44  or a suture retriever is inserted into the joint space  68  to retrieve the inserted end of the strand  163  and pull it out through the medial portal. The strand  163 , passed through the cannula  13  of the retrodrill cutter  10  and retained using a Mulberry knot, is pulled to draw the retrodrill cutter  10  into the joint space  68 . The retrodrill cutter  10  is positioned using a grasper and tibial retrodrill pin  150  is threaded into the cannulation  13  of the retrodrill cutter  10 . 
     Once engaged with the retrodrill cutter  10 , the tibial retrodrill pin  150  is rotated and retracted to drill a socket  200  in the tibia  60  to a desired depth D 2 , preferably 25 mm., as shown in  FIG. 11 . The retrodrill  10  is then pushed distally to exit the socket. A grasper is used to disengage the drill from the pin, and the retrodrill  10  is removed from the joint. The tibial retrodrill pin  150  remains in position, as shown in  FIG. 11 . 
     A soft tissue graft or a composite femoral bone/tendon allograft is prepared for insertion and fixation into the femoral and tibial sockets  100 ,  200 . The graft is selected so that its diameter corresponds to the diameters of the femoral and tibial sockets  100 ,  200 . Alternatively, the correct diameter of the retrodrill cutter  10  may be selected to correspond to the diameter of a previously-prepared graft  300 , illustrated in  FIG. 12 . The graft  300  has a length L ( FIG. 12 ) equal to the summed lengths of the femoral and tibial sockets plus the joint length between the two sockets. For example, assuming that the length D 1  ( FIG. 11 ) of the femoral socket  100  is about 25 millimeters, the length D 2  ( FIG. 11 ) of the tibial socket is about 25 millimeters, and the length D ( FIG. 11 ) between the two sockets is about 28 millimeters, the total length L of the graft  300  is about (25+25+28) millimeters, or about 78 millimeters. 
     Graft  300  is formed from soft tissue according to an exemplary embodiment of the present invention. The graft  300  is folded in half and whip stitched at the graft proximal end  301  and distal bundle ends  302 ,  304 . The graft is marked 25 mm from the graft proximal end  301 , for example, corresponding to the depth D, for the femoral socket  100 . A joint space length L of 28 mm, for example, is marked further down the graft  300 . The two distal graft bundles are measured to 25 mm, for example, corresponding to the depth D 2  for the tibial socket. 
     Each of the ends of the graft  300  is securely whip-stitched independently with one set of strands  303  and another set of strands  305 A and  305 B, as illustrated in  FIG. 12 . Preferably, at least the strands  305 A and  305 B are visually distinguishable. The diameter of the graft is measured, for example using a graft sizing block (not shown), to determine the diameter of the femoral and tibial sockets. 
     Installation of the graft is illustrated schematically in  FIGS. 13–18 . A loop  307  is formed in the femoral strand  63  and pulled out the medial portal to use as a transport for the proximal graft suture strands  303 . The set of graft suture strands  303  is passed through the loop  307  and pulled into the joint, as shown in  FIGS. 13 and 14 , through the femoral socket, and out through the lateral thigh. Referring to  FIG. 15 , graft  300  is pulled into the femoral socket  100  up to the 25 mm mark on the graft  300  to ensure complete seating. 
     Insertion of bundles  302  and  304  of graft  300  into tibial socket  200  proceeds similarly. A loop formed in tibial strand  163  around strands  305 A and  305 B is used to pull the strands  305 A and  305 B into the tibial socket  200 , as shown in  FIG. 16 . Strands  305 A and  305 B are brought out through the tibial portal. Both distal bundles  302 ,  304  of the graft are seated into the tibial socket up to the pre-marked line, as shown in  FIG. 17 . 
     Referring to  FIG. 18 , graft  300  is shown fully inserted, the femoral and tibial retrodrill pins  50 , 150 having been withdrawn and strands  303 ,  305 A, and  305 B extending through the respective transosseous femoral and tibial tunnels  100 ,  200 . With the ends of the graft  300  seated fully into the femoral and tibial sockets  100 ,  200 , graft tensioning and fixation is carried out. A button  310  is attached to the two ends of strand  303 . A Crabclaw knot pusher is used to advance the button  310  through the femoral portal down to the femoral bone surface. Multiple knots are tied to secure the button  310  with the knot pusher instrument. The button  310  includes two through-holes to accommodate the suture, and is made of a biocompatible material, typically a polymer, preferably PEET. 
     A second button  320  is attached to each end of strands  305 A and  305 B. Three non-reversing half hitches are tied and pushed down to the bone with a crabclaw knot pusher. Tension preferably is applied separately to each of the two tibial bundles, one with the knee in flexion and one with the knee in extension, as is known in the art. The post end of strands  305 A is passed through a suture tensioner (not shown). The suture tensioner securely holds the button onto the bone, and the strands  305 A is secured through slots and a holding screw at the end of the suture tensioner. The tensioning screw is turned to tension graft  300  and tighten the knots with the knee in the appropriate flexion/extension. As the surgeon determines the proper tensioning, quantified with load markings on the tensioner handle, a reversing half hitch is tied over the shaft of the tensioner and advanced through to the knot with the knot pusher instrument. The knot is forced over the end of the tensioner to lock the knot. Subsequent reversing half hitches may be added to secure the knot after the tensioner is removed. The procedure is repeated to secure the other bundle under anatomic tension in the appropriate knee extension/flexion. Button  320  includes four holes, for example, to accommodate strands  305 A and B. 
     Referring to  FIGS. 20A–C , a button implant  330  (sold by the assigned, Arthrex, Inc., under the tradename Tension Lok) is illustrated. Implant  330  is used in place of buttons  310  and  320 , for example, in securing tensioned strands at the surface of bone, particularly the femur. Implant  330  includes a ribbed, cannulated body  332  and an angled head  334 . A central cannula  336  extends through the implant  330 . Ribs  335  are tapered. The head  334  features rounded edges and corners, and has a generally triangular shape, as seen in  FIGS. 20A and 20C . Openings  338  formed through the head  334  on either side of the head opening of cannula  336  accommodate suture strands. The openings  338  are formed within a cavity  339  developed in the head  334  to provide a relief for knots tied in suture strands brought through the holes  338 . The head  334  is angled, as seen in  FIGS. 20A and 20B , to sit flush with the surface of the bone into which it is installed. 
     Implant  330  is introduced into a bone hole using a driver  340 , of which only the distal end and head are shown in  FIG. 20B . The head of driver  340  is angled and shaped to complement the head  334  of implant  330 . Head  334  occupies a footprint  342  ( FIG. 20C ) that is narrower than the distance between suture holes  338 , as represented by the hatched area  342 . Alternatively, head  334  occupies a wider footprint  344  and features a notch on either side providing clear access to suture holes  338 . 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art.

Technology Classification (CPC): 0