Patent Abstract:
A meniscal allograft with a bone block having a trapezoidal shape in cross-section and a technique for using a meniscus allograft having a trapezoidal shaped bone block are disclosed. A groove is formed initially in the bone using drill bits. Dilators are used to increase the size of the drilled groove. The orthogonal corner at the bottom of the groove is shaped using a rasp. A smooth dilator compacts the bone in the acute angle at the bottom of the groove opposite the orthogonal corner to create the final trapezoid shape of the bone groove. A meniscal allograft having a bone block of corresponding trapezoidal shape is prepared using a workstation and three cutting jigs to make three corresponding cuts. The trapezoidal bone block of the meniscal allograft is then installed within the bone groove.

Full Description:
This application claims the benefit of U.S. Provisional Application Ser. No. 60/403,438, filed Aug. 15, 2002, the entire disclosure of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to the field of surgery reconstruction and, in particular, to a meniscal allograft technique and system using a meniscal allograft having a dovetail notch. 
   BACKGROUND OF THE INVENTION 
   A known method of performing an anatomical reconstruction of the meniscus is the so-called meniscal allograft “keyhole” technique using instrumentation sold by Arthrex, Inc. of Naples, Fla. In this technique, the bone block of a meniscal allograft is formed in the shape of a keyhole plug, to match a corresponding keyhole groove prepared through the cortical and cartilagenous surface of the tibial plateau. The bone plug for the meniscal allograft is then fed into the keyhole groove, such that the meniscal allograft is mounted on the tibial plateau and secured without transosseous sutures. 
   Although the above-described technique is a vast improvement over prior meniscal allograft technique, the “keyhole” shape of the allograft implant is difficult to reproduce and necessitates a long preparation time, typically about 45 minutes. Thus, although the “keyhole” technique described above is a vast improvement over prior meniscal allograft techniques, it would be desirable to provide a meniscal transplant system and technique that is quicker, easier and more reproducible. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes the disadvantages of the “keyhole” technique by providing a meniscal allograft technique using a meniscus allograft having a trapezoidal shape in cross-section, as opposed to a “keyhole” shape. The trapezoidal shape is more easily reproducible than a “keyhole” shape. Preferably, the dovetail meniscus allograft has a trapezoidal shape with a 90 degree angle and is formed as a pre-cut meniscal allograft. 
   The dovetail meniscus allograft of the present invention is advanced into a same-size dovetail groove of a bone by impaction. The dovetail groove is formed initially using drill bits. Dilators are used to increase the size of the drilled openings. The orthogonal corner at the bottom of the groove is shaped using a rasp. A smooth dilator compacts the bone in the acute angle at the bottom of the groove opposite the orthogonal corner to create the final dovetail shape. 
   These and other features and advantages of the invention will be more apparent from the following detailed description that is provided in connection with the accompanying drawings and illustrated exemplary embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates an exemplary dovetail allograft implant according to the present invention at an initial stage of fabrication. 
       FIG. 2  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 1 . 
       FIG. 3  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 2 . 
       FIG. 4  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 3 . 
       FIG. 5  illustrates another view of the dovetail allograft implant of  FIG. 5 . 
       FIG. 6  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 4 . 
       FIG. 7  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 6 . 
       FIG. 8  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 7 . 
       FIG. 9  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 8 . 
       FIG. 10  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 9 . 
       FIG. 11  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 10 . 
       FIG. 12  illustrates another view of the dovetail allograft implant of  FIG. 11 . 
       FIG. 13  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 11 . 
       FIG. 14  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 13 . 
       FIG. 15  illustrates the dovetail allograft implant of  FIG. 1  at a stage of fabrication subsequent to that shown in  FIG. 14 . 
       FIG. 16  illustrates another view of the dovetail allograft implant of  FIG. 15 . 
       FIG. 17  illustrates yet another view of the dovetail allograft implant of  FIG. 15 . 
       FIG. 18  illustrates a tibia for forming a dovetail tibial groove that accommodates the dovetail allograft implant of  FIGS. 15–17 . 
       FIG. 19  illustrates a method of forming a dovetail tibial groove that accommodates the dovetail allograft implant of  FIGS. 15–17  according to the present invention and at an initial stage of formation. 
       FIG. 20  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 19 . 
       FIG. 21  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 20 . 
       FIG. 22  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 21 . 
       FIG. 23  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 22 . 
       FIG. 24  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 23 . 
       FIG. 25  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 24 . 
       FIG. 26  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 25 . 
       FIG. 27  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 26 . 
       FIG. 28  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 27 . 
       FIG. 29  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 28 . 
       FIG. 30  illustrates the dovetail tibial groove of the present invention at a stage of formation subsequent to that shown in  FIG. 29 . 
       FIG. 31  illustrates another view of the dovetail tibial groove of  FIG. 30 . 
       FIG. 32  illustrates the dovetail allograft implant of  FIGS. 15–17  inserted into the dovetail tibial groove of  FIG. 31 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention provides a meniscal allograft technique for forming a longitudinal groove in a bone, the groove having a trapezoidal or dovetail cross-section, and providing a pre-cut meniscal allograft also having a trapezoidal or dovetail cross-section. The trapezoidal shape of the pre-cut meniscal allograft is more easily reproducible than a “keyhole” shape. 
   Referring now to the drawings, where like elements are designated by like reference numerals,  FIGS. 1–17  illustrate an exemplary embodiment of a dovetail meniscal allograft implant  100  ( FIGS. 15–17 ) fabricated according to the present invention, while  FIGS. 18–31  illustrate the formation of a longitudinal dovetail tibial groove  99  ( FIG. 31 ) that accommodates the dovetail meniscal allograft implant  100 .  FIG. 32  illustrates the dovetail meniscal allograft implant  100  of  FIGS. 15–17  inserted into the dovetail tibial groove  99  of  FIG. 31 . 
   The dovetail meniscus implant  100  can be machined from allograft cortical bone using known techniques, and is preferably a single piece of harvested material with the meniscus on a bone block. Alternatively, the implant can be formed of a synthetic material, preferably a synthetic cortical bone material. A preferred synthetic bone material is tricalcium phosphate (TCP) and/or hydroxyapatite (HA), or a biodegradable polymer, preferably a polylactide, such as PLLA. 
     FIG. 1  illustrates a meniscus  10  formed of allograft cortical bone. As shown in  FIG. 1 , meniscus  10  is first mounted on a graft workstation, where bone block  14  is marked and trimmed to a length “L” corresponding to the longitudinal length of dovetail tibial groove  99  (the formation of which will be described in more detail below with reference to  FIGS. 17–30 ). Referring to  FIG. 2 , any additional bone that is anterior or posterior to the sides of horns  12  of meniscus  10  is removed.  FIG. 3  shows the marking of dovetail configuration A onto both the anterior and posterior facets of the bone block  14 , so that the horns  12  are centered on side A 4  of the trapezoid or dovetail configuration A. The dovetail configuration A is a cross-sectional trapezoidal shape with four edges A 1  (height), A 2  (base), A 3  and A 4  (small base), edges A 1  and A 2  forming a ninety degree angle and edges A 2  and A 3  forming an acute dovetail angle α, as shown in  FIG. 3 . The acute dovetail angle α is about 25 degrees to about 75 degrees, more preferably about 45 degrees. 
     FIGS. 4 and 5  illustrate meniscus  10  secured between two grafting holding posts and positioned upside down. As shown in  FIGS. 4 and 5 , meniscus  10  hangs freely and away from the bone block  14 , so that the edge A 1  of the dovetail configuration A is aligned with the holding posts. As also illustrated in  FIG. 4 , base A 2  is aligned with the bottom of the holding posts. 
   Referring now to  FIGS. 6–8 , a first cutting jig  21  is aligned ( FIGS. 6 ,  7 ) to the edge A 1  of the of the meniscus  10 , so that bone from the bone block  14  is vertically cut ( FIG. 8 ) along the edge A 1  of the dovetail configuration A. A second cutting jig  22  ( FIG. 9 ) is then aligned with the flat base A 2  so that bone from the block  14  is horizontally cut along the base A 2  of the dovetail configuration A of the bone block  14 , as shown in  FIG. 10 . The length of the edge A 1  of the dovetail configuration A is of about 8 mm to about 12 mm, more preferably of about 10 mm. The length of the base A 2  of the dovetail configuration A is of about 8 mm to about 12 mm, more preferably of about 10.5 mm. 
     FIGS. 11–14  illustrate cutting of bone from the bone block  14  along edge A 3  of the dovetail configuration A using a third cutting jig  23 , to define the length of the edge or small base A 4  and to complete the fabrication of body  15  of the dovetail meniscal allograft implant  100 . The length of the small base A 4  is of about 5 mm to about 10 mm, more preferably of about 7 mm. As illustrated in  FIGS. 15 ,  16  and  17 , which are more detailed illustrations of the dovetail meniscal allograft implant  100  fabricated as described above, body  15  is defined by the four edges (A 1 , A 2 , A 3  and A 4 ) of the dovetail or trapezoid configuration A, with the horns  12  of the meniscus  10  attached to the surface defined by the small base A 4  and the length L of the body  15 . 
   A method of forming longitudinal dovetail tibial groove  99  ( FIG. 30 ) is now described with reference to  FIGS. 18–31  and by using known techniques of drilling through the tibia  50 , shown in  FIG. 18 . The longitudinal tibial groove  99  of the present invention has a dovetail configuration and a size that accommodates the insertion of the dovetail meniscal allograft implant  100  fabricated as described above. 
   Osteotome  55  and alignment guide  53  are assembled, as shown in  FIG. 18 , after debriding the remaining meniscus just to the periphery, leaving only a thin cartilaginous peripheral rim attached to the capsule. Using a high speed bur, the lateral tibial eminence is shaved down until there is a bleeding vascular bed. Removal of the tibial eminence enhances exposure and ensures proper placement of the drill guide, as described in more detail below. Alignment rod  54  ( FIG. 19 ) is then positioned in an anterior to posterior plane, entered through the anterior and posterior horns  57  and  58 , respectively, of the tibial meniscus.  FIG. 20  illustrates osteotome  55  and alignment rod  54  positioned so that the osteotome  55  can advance into the proximal side of tibia  50  through the horns  57 ,  58  so that the top of the osteotome  55  is flush with tibial plateau  51  and stops at the posterior horn  58 , as shown in  FIG. 21 . 
   The handle of osteotome  55  is then removed, leaving its blade  55   a  into position. A first Drill Guide  60  is subsequently positioned over the blade  55   a , flush to the anterior tibia, as shown in  FIG. 22 . Using a 6 mm drill bit  61  ( FIG. 23 ), the tibial plateau  51  is cut through and drilled through the first Drill Guide  60 , from the anterior horn  57  to the posterior horn  58  for a distance “L” which illustrates the length of the dovetail meniscal implant  100  ( FIG. 17 ).  FIG. 24  illustrates the 6 mm drill bit  61  cutting through the plateau channel and advancing through into the tibia under direct visualization until it contacts the posterior tibial cortex. 
   The first Drill Guide  60  that accommodates the 6 mm drill bit  61  is then removed from the osteotome  55 , so that a second Drill Guide  70  is attached to the osteotome  55 , as shown in  FIG. 25 . The second Drill Guide  70  accommodates an 8 mm drill bit  71  ( FIG. 25 ) to drill through the tibial plateau  51  from the anterior horn  57  to the posterior horn  58 , in a way similar to that using the 6 mm drill bit  61 . A curette may be optionally used to further debride the groove subsequent to the drilling operation.  FIG. 26  illustrates tibial groove  90  formed within tibia  50  at the end of the drilling operation with both the 6 mm drill bit 61 and 8 mm drill bit  71 . 
   A rasp  75  is subsequently used to create the orthogonal angle of the dovetail configuration A ( FIGS. 15 ,  16  and  17 ) into the tibial groove  90 , as shown in  FIG. 27 . The rasp  75  must remain flush to the articular surface of the tibia and may be slowly advanced with a combination of maletting and hand rasping until it reaches the posterior tibial cortex. A dilatator  80  ( FIGS. 28 ,  29 ) may be also inserted in the tibial groove  90  to increase the size of the drilled channel and to form the dovetail acute angle α of the dovetail configuration A ( FIGS. 15 ,  16  and  17 ), using gentle taps of a mallet if necessary, and to complete the formation of the longitudinal dovetail tibial groove  99 , as shown in  FIGS. 30 and 31 . 
   The longitudinal dovetail tibial groove  99  has a size and a length “L” that accommodate the dovetail meniscal allograft implant  100  fabricated as described above. By placing a ruler inside the prepared tibial groove  99 , the length L is properly measured and then transferred onto the allograft bone block  14  of  FIG. 1 , to prepare the formation of the dovetail meniscal allograft implant  100 , as described above with reference to  FIGS. 15–17 . 
   Finally, the dovetail meniscal allograft implant  100  is passed into the recipient dovetail tibial groove  99 , as shown in  FIG. 32 , and the dovetail groove is cleared of any remaining bone debris in the posterior portion of the tibia. As the dovetail meniscal allograft implant  100  is delivered to the tibial groove  99 , the graft passing suture attached to the meniscal allograft implant  100  is lead out the posterior lateral capsule via a standard inside out meniscal suturing technique. A meniscal allograft tamp may be employed to position the meniscal allograft implant  100  into the dovetail tibial groove  99 . 
   As described above, the invention provides an improvement over the “keyhole” technique in that the shapes of the dovetail meniscal allograft implant  100  and of the corresponding longitudinal dovetail tibial groove  99  are more easily reproducible compared to the “keyhole” structures. Further, the invention provides a method of fabricating a meniscal allograft implant, such as the dovetail meniscal allograft implant  100 , in about 5 to 8 minutes, as opposed to about 45 minutes required for the fabrication of the “keyhole” allograft structure. 
   Variations, modifications, and other uses of the present invention will become apparent to those skilled in the art, including the following, non-limiting examples: attachment of bone to bone; attachment of soft tissue to bone; non-medical applications. Thus, 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. 
   The above description and drawings illustrate preferred embodiments which achieve the objects, features and advantages of the present invention. It is not intended that the present invention be limited to the illustrated embodiments. Any modification of the present invention which comes within the spirit and scope of the following claims should be considered part of the present invention.

Technology Classification (CPC): 0