Abstract:
Osteochondral sockets are formed using a retrograde drill assembly. The retrograde drill assembly includes a guide pin having a fluted tip and an externally threaded portion. A removable cutter head has internal threads that engage the threads of the guide pin. The guide pin is drilled through bone, exposing the external threads in a joint space requiring repair. The cutter is threaded onto the guide pin, and the assembly is retrograded with rotation to form a socket in the bone. The cutter is disengaged from the guide pin for disassembly and removal from the bone, making way for an implant to be installed in the pocket. The implant can be drawn into the socket using an attached strand threaded through the bone socket and out of the bone.

Description:
RELATED APPLICATIONS 
     This application is a divisional of application Ser. No. 10/792,780, filed Mar. 5, 2004 now U.S. Pat. No. 7,160,305, which claims the benefit of U.S. provisional application No. 60/452,527, filed Mar. 7, 2003, the disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of surgery and, more particularly, to methods and apparatus for retrograde repair of osteochondral defects. 
     BACKGROUND OF THE INVENTION 
     Methods and apparatus related to arthroscopic osteochondral transplantation for repairing chondral defects are known in the art. For example, U.S. Pat. No. 5,919,196, the disclosure of which is incorporated by reference herein, involves autograft transplantation using matched graft harvesters and recipient site harvesters, in the form of tubes with collared pins, to create and transplant donor graft osteochondral cores into correspondingly sized recipient sockets. 
     Although the above-described procedure is a significant improvement over prior art techniques for osteochondral transplantation, it is difficult to access defects on the tibial plateau using donor and recipient harvesters, as required in the technique of the &#39;196 patent. 
     Accordingly, it would be desirable to provide apparatus and methods for creating the recipient site socket from the inside out, i.e., using a retrograde technique. It would also be desirable to provide a technique for inserting the replacement osteochondral core or implant in a retrograde manner to obviate inserting a harvester into the joint. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages of the prior art and fulfills the needs noted above by providing a retrograde osteochondral system by which a grafted healthy bone or synthetic implant is implanted into the recipient site in a retrograde manner. 
     The retrograde osteochondral system of the present invention employs a retrodrill device for osteochondral reconstruction. The retrodrill device is provided with a retrograde cutter that is detachable from a guide pin. The cutter has a cannulated body provided with a plurality of cutting flutes on a proximal face and disposed radially. The guide pin includes a cannulated body with a proximal end and a distal end, and a trocar disposed in the lumen of the cannulated body. The exterior of the cannulated body is provided with graduated depth markings. The cannulated body of the guide pin has threads toward the distal end for receiving corresponding threads in the cannulation of the retrodrill cutter. 
     According to one embodiment of the present invention, retrograde osteochondral reconstruction is conducted using the retrodrill cutter in a retrograde manner to form a recipient socket at the location of an osteochondral lesion developed on the head of the tibia, for example. Socket depth is gauged using by employing depth markings on the cannulated retrodrill guide pin. More specifically, formation of the recipient socket begins by using the retrodrill guide pin with the inserted trocar to drill a tunnel through an upper portion of the tibia, from behind and through the osteochondral lesion, and into the tibial joint space. A drill guide with a marking hook placed on the lesion is used to ensure accurate placement of the guide pin. The retrodrill cutter is then inserted into the joint space and oriented perpendicularly to the tibial lesion so that the guide pin can be inserted into, and threadingly engaged with, the retrodrill cutter. Once secured to the retrodrill cutter, the guide pin is retracted until the proximal cutting face of the retrodrill cutter contacts the tibial osteochondral lesion. The retrodrill cutter is then rotated and further retracted through the osteochondral lesion and into the tibia to the proper depth as measured on the outside of the knee by the depth markings on the guide pin. The retrodrill cutter is advanced out of the completed socket, and disengaged from the retrodrill guide pin by applying a reverse drilling motion to the guide pin while holding the cutter stationary. 
     A core, such as a graft bone core or a synthetic implant, is fitted with a length of suture to provide a means for pulling the core into the tibial recipient socket described above. The length of suture preferably passes through a longitudinal cannulation in the core, made available by removing the trocar, and is secured to the core using either a knot at the back end, an adhesive, insert molding, or equivalent securing methods. The suture extends through the leading tip of the core a sufficient length to allow the suture to pass through the cannulated retrodrill guide pin and be grasped for pulling the core into the tibial socket. 
     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-2B  illustrate a retrodrill guide pin including a cannulated body and a trocar according to the present invention. 
         FIG. 3  schematically illustrates the formation of a socket at a tibial recipient site according to the present invention. 
         FIG. 4  schematically illustrates the formation of a tibial recipient socket at a stage subsequent to that shown in  FIG. 3 . 
         FIG. 5  schematically illustrates the formation of a tibial recipient socket at a stage subsequent to that shown in  FIG. 4 . 
         FIG. 6  schematically illustrates the formation of a tibial recipient socket at a stage subsequent to that shown in  FIG. 5 . 
         FIG. 7  schematically illustrates a completed socket formed at the tibial recipient site. 
         FIG. 8  schematically illustrates the installation of an osteochondral core within the tibial socket formed according to the present invention. 
         FIG. 9  schematically illustrates the installation of osteochondral core at a stage of processing subsequent to that shown in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides a retrodrill technique and apparatus for providing a recipient bone site or socket that is formed in a retrograde manner during retrograde osteochondral repair. A core, such as a grafted healthy bone or a synthetic implant, is installed into the recipient bone socket in a retrograde manner. 
     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 threadedly engaged by a retrodrill guide pin  50  ( FIGS. 2A and 2B ). The retrodrill cutter  10  is formed of a cannulated body  11  surrounded by a plurality of cutting flutes formed by longitudinal teeth  12 . Cannulation  13  has internal threads  14 , discussed further below. 
     The retrodrill guide pin  50  has a proximal end  54 , a distal end  52 , and a cannulated body  53 , which is lazed with calibrated depth markings  56 . The lumen of the cannulated body accepts a trocar  58  having a pointed tip  59 . When the trocar is removed, a strand of suture can be passed through the lumen of the cannulated body. The proximal end  54  of the cannulated body of retrodrill guide pin  50  is configured for chucking into a rotary driver (not shown) and includes a setscrew collar  62  for securing an axial position of the trocar  58  in the cannulated body  53 . The distal end  52  of the retrodrill guide pin  50  is open at the tip to expose the pointed end  59  of the trocar  58 . Distal end  52  also features a fluted region  51  and a threaded region  55  ( FIG. 2B ). Threaded region  55  is designed to engage corresponding threads  14  provided in the cannulation  13  of the retrodrill cutter  10 . Accordingly, the diameter of the cannula  13  of the retrodrill cutter  10  closely approximates the diameter of outer threaded region  55  of the retrodrill guide pin  50 , to allow engagement of the outer threaded region  55  with the inner threads  14  of retrodrill cutter  10 . 
     The threaded region  55  has an outer diameter that closely approximates, and preferably is less than, the diameter of shaft  53 . Threaded region  55  terminates proximally to meet a shoulder  57  established by the remaining portion of shaft  53 , the shoulder  57  providing a stop for the inner threads of cutter  10 . Threaded region  55  and fluted tip  51  partially overlap. A portion of the fluted tip extends distally beyond threaded region  55 , preferably substantially the length of the threaded cannula of the cutter. Accordingly, the cutter can be positioned conveniently over an unthreaded portion of the fluted tip as an initial step of assembling the cutter onto the guide pin. 
     A preferred method of forming a tibial socket using the retrodrill guide pin  50  and the retrodrill cutter  10  of the present invention, and then installing core  46  within the formed tibial socket, is described below with reference to  FIGS. 3-9 . 
       FIG. 3  illustrates a schematic anterior view of a knee  60  in which osteochondral lesion or defect  69  is located on tibial plateau  63  of tibia  66 . Standard diagnostic arthroscopy is employed to evaluate the location and extent of the osteochondral lesion  69 , as well as the defect pathology. As described below, the osteochondral lesion  69  is drilled out by employing a retrodrill technique in connection with a retrograde osteochondral repair method of the present invention. 
     A long adapter drill guide  70 , for example an Arthrex C-Ring cross-pin drill guide such as those disclosed in U.S. Pat. Nos. 5,350,383 and 5,918,604, the disclosures of which are incorporated by reference herein, is secured to the lateral thigh, as shown in  FIG. 3 . Marking hook  72  of the adapter drill guide  70  is inserted into the joint space near intercondylar notch  71  and positioned over the osteochondral lesion  69  of the tibial plateau  63 . Hook  72  includes a laser mark located anterior to tip  73  of the marking hook  72 , to ensure placement of a guide pin  50  at a ninety-degree retrograde entry relative to the osteochondral lesion  69 . The marking hook is held in position on the drill guide  70  by tightening knurled knob  75 . 
     Once the drill guide  70  is properly positioned, cannulated retrodrill guide pin  50  is placed through sleeve  78  of the drill guide  70 . Referring to  FIG. 2A , trocar  58  is inserted in the cannulation of guide pin  50  and secured in place using setscrew collar  62  to provide the guide pin  50  with a pointed tip. As shown in  FIG. 4 , the guide pin  50  is installed through the bone in an anterior-to-posterior direction relative to the osteochondral lesion  69 , forming a narrow (3 mm) tunnel  67  through the bone and perpendicular to the osteochondral lesion  69 . The cannulated retrodrill guide pin  50  is drilled through the lesion toward the tibial joint space until contact is made with the marking hook  72  of long adapter drill guide  70 . 
     Once the guide pin is drilled into the tibial space, the trocar  58  is removed, and a strand  43  is inserted in its place through the cannulated body and into the joint space. An end of the strand is placed through the cannulation of retrodrill cutter  10  and secured, and the retrodrill cutter  10  is drawn into the joint space and aligned perpendicularly with the tibial lesion  69  and the guide pin  50 . The threaded retrodrill guide pin  50  is inserted and engaged with the threads of the cannulated retrodrill cutter  10  by rotating and advancing the guide pin  50  in the direction of arrow F ( FIG. 4 ) with respect to the retrodrill cutter  10 . Optionally, placement of retrodrill cutter  10  employs a grasper or a similar device (not shown), for example. 
     Once engaged within the retrodrill cutter  10 , the cannulated retrodrill guide pin  50  is chucked into a rotary driver and retracted until the proximal face of retrodrill cutter  10  contacts the tibial plateau  63  and lesion  69 . At this point, a first reading of the markings  56  on the cannulated retrodrill guide pin  50  is recorded relative to anterior tibial skin surface  61 . 
     The cannulated retrodrill guide pin  50  is then rotated and retracted so that the proximal cutting face of retrodrill cutter  10  cuts through the surface of osteochondral lesion  69  and into the underlying bone, thereby forming a tibial recipient socket  100  as shown schematically in  FIG. 7 , in which representations of the surgical apparatus having been omitted for clarity. A second reading of the markings  56  on the retrodrill guide pin  50 , recorded relative to the anterior tibial skin surface  61 , is used to gauge the depth D of the retrodrill cutter  10  into the tibia  66 . For example, once the first reading of the markings has been recorded, the surgeon could count about thirty markings  56  to the second reading, which would correspond to a depth D of about 5 to about 10 millimeters depending upon the mark spacing. 
     After drilling the retrodrill cutter  10  into the tibia  66  and completing the socket, the retrodrill guide pin remains in place, and is advanced to urge cutter  10  out of the socket. The retrodrill cutter  10  is disengaged from the retrodrill guide pin  50  by a reverse drilling motion, in the direction of arrow R of  FIG. 6 . The retrodrill cutter  10  is disengaged from the end of stand  43 , by cutting the strand, for example. The end of strand  43  is secured to remain in place and available in the joint space by tying a knot, for example, to prevent the strand from being pulled back through cannulated body  53 . 
     Reference is now made to  FIG. 8 , which shows the retrograde insertion of an osteochondral core or plug  46  into the recipient socket  100  of tibia  66 . The core  46  is developed, for example, as a cannulated plug formed of a translucent or transparent polymer material, and preferably made of bioabsorbable materials such as polyglycolic or polylactic acid polymers. Optionally, core  46  is an autograft or autogenous bone core, or an allograft core, harvested by known methods of the art and subsequently employed in the retrograde osteochondral repair method of the present invention. Alternatively, the core  46  is a synthetic implant plug formed from a synthetic hydrogel, preferably Salubria™, having various shapes, preferably a cylindrical shape with one end being curved to match a portion of an articular surface. Salubria™ is a hydrogel composition, which is similar to human tissue in its mechanical and physical properties, and is sold by Salumedica of Atlanta, Ga. 
     Strand  43  is inserted through an opening formed through core  46 , and is secured to the back end of the core by a ball or knot  44  ( FIG. 8 ). If desired, the knot  44  is countersunk into the core  46  for permanent suture fixation. Alternatively, strand  43  is attached to core  46  by insert molding or adhesive. 
     The suture strand or wire  43  extending from the core  46  is passed outside the tibia, preferably through the lumen of cannulated body  53  of guide pin  50 , the trocar  58  having been removed. Optionally, when using a non-cannulated guide pin, for example, strand  43  passes directly through the tunnel  67 . The free end of strand  43  is captured outside the body and retracted to draw the suture or wire  43  through the guide pin  50 . As the strand  43  is drawn, the core  46  is pulled into the joint space and pivoted into axial alignment with the tibial recipient socket  100 . Continued tension on strand  43  draws core  46  into the tibial socket  100  in a retrograde fashion. One skilled in the art will realize that the amount of force for advancing the core  46  into the tibial recipient site  100  is directly proportional to the diameter and length (L) of the core  46 , as well as the depth of the tibial socket  100 . 
     Once the core  46  is secured within the tibial socket  100 , the strand  43  exiting the lateral opening of the tibia can be secured with a button or a small diameter T-screw provided over or in the hole and substantially flush with the cortical bone. Alternatively, the strand  43  is removed, for example, by grasping the ball or knot  44  with a grasper or a similar device and drawing the strand out through the joint space. If complications occur, such as over-insertion of the core  46 , the cannulated retrodrill guide pin  50  is employed to push the core out of the tibial site for corrections. 
     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.