Patent Publication Number: US-8523864-B2

Title: Instrumentation for the preparation and transplantation of osteochondral allografts

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a divisional application of copending U.S. patent application Ser. No. 11/259,749, filed Oct. 26, 2005, the disclosure of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     In humans and many other animals, cartilage is present on the surface of bones that form articular joints to facilitate articulation of the joint and protect and cushion the bones. However, defects may develop in the cartilage from various causes such as abrupt trauma or prolonged wear. A number of techniques have been attempted to treat such cartilage defects. One such technique is the transplantation of fresh osteochondral allografts. 
     In this procedure, an allograft plug, also known as a osteochondral plug or core, is harvested from a condyle or rounded joint-forming portion of a donor bone. Intact on the surface of the allograft plug, on a portion of the bone known as the cartilage plate, is healthy cartilage. The allograft plug may also have attached to the cartilage plate cancellous tissue, which is the porous inner material that is present in many bones. In the recipient patient, the cartilage defect and the corresponding portion of underlying bone are cutaway and removed from the joint. The allograft plug is then inserted and attached to the cutaway portion so that the cartilage plate and healthy cartilage of the allograft plug align with the cartilage on the surface of the host bone. 
     One problem that arises with osteochondral allografts is that the recipient may adversely respond or reject the allograft plug. This can happen primarily because of the antigenic material contained in the cancellous bone of the allograft plug. Occurrence of such an adverse response may result in the recipient site reforming or healing in such a manner that the allograft plug becomes walled off from the host bone thereby delaying or preventing incorporation of the allograft. In addition, physically attaching and securing the allograft plug to the recipient site presents difficulties. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides methods and instruments for preparing and transplanting osteochondral allografts to repair articular cartilage defects. According to one aspect of the invention, an allograft plug having a cartilage plate and cancellous bone tissue attached thereto is removed from a donor bone. The allograft plug is further shaped by removing or cutting away cancellous bone tissue to form a cancellous stalk extending from the cartilage plate. The formed cancellous stalk can have any suitable shape including cylindrical, conical, and rectilinear. According to another aspect of the invention, in what will become the host bone of the patient, a recipient site is prepared by forming a cutout corresponding to the cartilage defect. The shape of the cutout generally corresponds to the shape of a provided allograft plug from which cancellous material has been removed to form a cancellous stalk. The allograft plug is inserted into the cutout such that the cancellous stalk is retained in the host bone and the cartilage plate aligns with the condyle surface of the host bone. Removing and shaping the allograft plug can be performed separately or together with preparing a recipient site by forming a cutout and inserting the allograft plug into the cutout. 
     To prepare the recipient site, a template can be attached to the host bone in a location corresponding to the cartilage defect. In an aspect of the invention, the template can include a guide aperture disposed therein. To facilitate alignment of subsequent operations, an elongated guide pin is inserted through the guide aperture and into the host bone. Cannulated drill bits having the desired shape can be slid over the guide pin and driven into the host bone to form the shaped cutout. In another aspect of the invention, the template can include a plurality of cut slots disposed therein. A cutting device can then be inserted through the cut slots and into the host bone to form the shaped cutout. 
     To remove and shape the allograft plug from the donor site, a second template specially adapted to attach to the donor bone can be used. One advantage of employing a template to remove the allograft plug is that template may facilitate simultaneous shaping of the allograft plug at the time of removal. In other embodiments, the allograft plug can initially be a piece of cylindrically or otherwise shaped bone material removed from the donor bone and subsequently shaped to produce the finished allograft plug. 
     It should be recognized that various aspects of the invention may also be applicable to preparing and transplanting an osteochondral autograft plug, a process which involves removing a plug from a first location and transplanting the plug into a second location within the same patient. 
     The invention provides one or more of the following advantages: An advantage of the invention is that it provides a osteochondral allograft plug that has a reduced amount of cancellous tissue and is therefore less likely to be rejected by a recipient. Another advantage is that it provides a specially shaped osteochondral allograft plug that can be fit and anchored into a correspondingly shaped cutout at the recipient site. These and other advantages and features of the invention will be apparent from the detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view of a device for removing from a donor bone a transplantable osteochondral allograft plug for repairing a cartilage defect. 
         FIG. 2  is a perspective view of an allograft plug shaped in accordance with an embodiment of the invention, the allograft plug having a cartilage plate and a cylindrical cancellous stalk. 
         FIG. 3  is a perspective view of another embodiment of an allograft plug having a cartilage plate and a conical cancellous stalk. 
         FIG. 4  is a perspective view of another embodiment of an allograft plug having a rectangular shape. 
         FIG. 5  is a perspective view of another embodiment of an allograft plug having a triangular shape. 
         FIG. 6  is a front elevational view of a template for preparing a recipient site in accordance with the teachings of the invention, the template including a central guide aperture. 
         FIG. 7  is a side elevational view of the template shown in  FIG. 6  and further illustrating a detachable handle engaged to the template. 
         FIG. 8  is a perspective view of the template of  FIG. 6  attached to the condyle of host bone in accordance with an embodiment of the invention, the handle being engaged to the template and a guide pin being inserted through the template 
         FIG. 9  is a perspective view of the guide pin inserted into the condyle of the host bone after removal of the template. 
         FIG. 10  is a side elevational view of another embodiment of a cannulated drill bit for forming a cutout in a recipient site in accordance with an embodiment of the invention, the drill bit having a counter-bore forming element and a conical cutting body with a central cannula shown in cutaway. 
         FIG. 11  is a side elevational view of another cannulated drill bit for forming a cutout in a recipient site in accordance with an embodiment of the invention, the drill bit having a counter-bore forming element and a cylindrical cutting body. 
         FIG. 12  is a perspective view of the drill bit of  FIG. 9  being driven into the condyle of the host bone to form the cutout. 
         FIG. 13  is a cross-sectional view taken generally along line A-A of  FIG. 12  illustrating cutout formed into a recipient site of a condyle of a host bone. 
         FIG. 14  is a perspective view of the condyle of a host bone illustrating a method of inserting an shaped allograft plug into a cutout formed at a recipient site using a tamp. 
         FIG. 15  is a front elevational view of the condyle of a host bone illustrating another method of inserting a shaped allograft plug into a cutout formed at a recipient site using a suture. 
         FIG. 16  is a perspective view of a guide plate with a removable guide cylinder for assisting in removing and shaping a cylindrically shaped allograft plug from a donor bone. 
         FIG. 17  is a top perspective view of a cannulated burring shell for removing cancellous material and shaping a conically shaped allograft plug. 
         FIG. 18  is a cross-sectional view of a sleeve placed about an allograft plug having a cylindrical shaped cancellous stalk and a guide pin inserted through the sleeve and partially into the cancellous stalk. 
         FIG. 19  is a perspective view of a pair of specially configured forceps for handling and manipulating a shaped allograft plug. 
         FIG. 20  is a front elevational view of a template having cut slots for removing and shaping a rectilinear allograft plug from a donor bone. 
         FIG. 21  is a cross-sectional view of the template taken along line B-B of  FIG. 20 . 
         FIG. 22  is a cross-sectional view of another embodiment of a template, similar to the template shown in  FIGS. 20 and 21 , but adapted for preparing a recipient site on a host bone to receive a rectilinear allograft plug. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now referring to the drawings, wherein like reference numbers refer to like elements, there is illustrated various processes and instruments for preparing and transplanting an osteochondral allograft in accordance with the various embodiments of the invention. Referring first to  FIG. 1 , there is shown a device  100  suitable for cutting and forming a cylindrically shaped allograft plug  124  from a donor bone  120  in accordance with one aspect of the invention. The device  100  itself includes a clamp assembly  102  and a tubular crown saw  104 . The clamp assembly  102  includes two vertically extending clamp pads  106 ,  108 , that can be moved with respect to each other by rotation of a linear screw mechanism  110 . The crown saw  104  is directed towards and linearly movable with respect to the clamp assembly  102 . To align the clamp assembly  102  and crown saw  104 , the crown saw can pass through a vertical alignment plate  112  joined to a base  114  onto which the clamp assembly is also mounted. 
     To produce an allograft plug, a donor bone  120  or a portion thereof having on its surface healthy cartilage is received between the clamp pads  106 ,  108  and the clamp pads are moved together to grasp and hold the donor bone in alignment with the crown saw  104 . Preferably, the donor bone  120  can be received in the clamp assembly  102  such that a condyle  122  corresponding to a donor site on the donor bone  120  is positioned towards the crown saw  104 . The rotating tubular crown saw  104  is moved towards and into the donor site  122  to form a cylindrical cut into the donor bone  120 , after which the crown saw can be removed. The cylindrically shaped bone material  124  produced by the cylindrical cut and that will correspond to the allograft plug can then be removed from the remainder of the donor bone  120  by, for example, transecting the donor bone with a saw or by propagating a crack through the donor bone with a tamp or similar device. 
     The removed cylindrical shaped bone material  124  has a cartilage plate  126  corresponding to the outer surface of the donor bone  120  and on which healthy cartilage is located. Extending from the cartilage plate  126  is cancellous bone tissue  128  from the interior portion of the donor bone  120 . As will be appreciated by those of skill in the art, when making the cut into the donor site  122 , the donor bone  120  and the crown saw  104  are preferably arranged so that the contour of the cartilage plate  126  corresponds to the portion of the host bone which is to be repaired. 
     Once the cylindrically cut bone material has been removed, it can be shaped by any variously suitable subsequent shaping operation to remove cancellous bone tissue and form a cancellous stalk extending from the cartilage plate. Removing cancellous bone tissue results in the cancellous stalk having a reduced cross section compared to the cross-section of the cartilage plate. 
     Because the cancellous bone tissue on the allograft plug could contain antigenic material, reducing the amount of cancellous bone tissue transplanted to the host reduces the possibility of an adverse reaction within the host. Another advantage of shaping the allograft plug to form a cancellous stalk is that the stalk provides an anchor-like structure that assists in anchoring the allograft plug into a recipient site on the host bone. A related advantage is that, by removing cancellous tissue from the cancellous stalk, the amount of cancellous tissue that must be accommodated by the host bone during transplantation is reduced. Accordingly, the size of the cutout that must be formed into a recipient site on the host bone is likewise reduced thereby requiring less trauma to the host bone. 
     The finished allograft plug can have any suitable shape. For example, referring to  FIG. 2 , there is illustrated an allograft plug  130  having a circular cartilage plate  132  and a cylindrical cancellous stalk  134  of cancellous bone tissue extending therefrom. The cartilage plate  132  has a generally circular perimeter of a first diameter and includes healthy cartilage from the donor intact on subchondral bone tissue  136 . On the underside of the cartilage plate  132  there may also be a thin layer of cancellous bone tissue  138  which corresponds to the first diameter. The cylindrically shaped cancellous stalk  134  extends from the thin layer of cancellous bone tissue  138  and has a second perimeter or second diameter reduced in size with respect to the first diameter. The reduction in size of the second perimeter compared to the first perimeter is the result of removing cancellous bone tissue to form the stalk. Preferably, the circular cartilage plate  132  and the cylindrical cancellous stalk  134  are coaxial. 
     Referring to  FIG. 3 , there is illustrated another embodiment of an allograft plug  140  having circular cartilage plate  142  and a generally conical cancellous stalk  144  extending therefrom. The cartilage plate  142  again has a first perimeter of a given first diameter while the conical perimeter of the cancellous stalk tapers so as to progressively reduce in diameter as the stalk extends from the cartilage plate. Preferably, the circular cartilage plate  142  and the conical cancellous stalk are coaxial. In other embodiments, the cancellous stalk may have a stepped shape with each step having a reduced perimeter or diameter compared to the first perimeter of the cartilage plate. 
     Referring to  FIG. 4 , there is illustrated another embodiment of an allograft plug  150  having rectangular cartilage plate  152  with a tapering or rectangular pyramid-shaped cancellous stalk  154 . As will be appreciated, the tapering of the cancellous stalk  154  results in a progressive reduction of its cross-section with respect to the cross-section of the rectangular cartilage plate  152 . Referring to  FIG. 5 , there is illustrated an allograft plug  160  having a triangular cartilage plate  162  and a tapering triangular pyramid-shaped cancellous stalk  164  extending therefrom. In other embodiments, the rectangular and triangular cartilage plates can have respective rectangular and triangular cross-sectioned stalks extending therefrom. 
     To prepare a recipient site in a host bone for receiving the allograft plug, special instruments can be used to form a cutout corresponding in shape to the allograft plug. Such special tools can include, for example, a template  170  as illustrated in  FIGS. 6 and 7 . The template  170  includes a flat, circular template plate  172  through the center of which is disposed a guide aperture  174 . From one surface of the template plate  172  there projects a short distance a plurality of sharp teeth  176 . The teeth  176  are preferably arranged in a circular pattern concentric with the circular template plate  172 . To enable manipulation of the template  170 , the template preferably also includes a detachable handle  180  that engages a corresponding engagement structure  182  on the opposite surface of the plate  172  from which the teeth  176  project. The handle  180  and plate  172  can be engaged by, for example, a twist lock mechanism. In various embodiments, the guide aperture  174  can continue through the detachable handle  180  as well. The guide aperture  174  is adapted to receive a guide pin  184  in a sliding fit such that the guide pin  184  can be inserted through the center of the plate  172 . 
     When preparing a recipient site with the template, referring to  FIG. 8 , a joint such as a knee joint of the patient being treated is first manipulated to expose the cartilage defect on the surface of a condyle  192  of a host bone  190 . Once the cartilage defect is suitably exposed, the template  170  is attached via the sharp, projecting teeth to the condyle  192  at a location corresponding to the defect. Preferably, to minimize damage, the circular pattern of the teeth projecting from the template corresponds to the area of the defect. Once the template  170  is attached, the detachable handle  180  can be removed and the guide pin  184  inserted through the guide aperture  174  and into the host bone  190  at the location of the defect. Once the guide pin  184  is driven into the host bone  190 , the handle  180  can be reattached to the template  170  and the template pull over the guide pin and removed from the condyle  192 . In other embodiments, the guide pin can be inserted with the handle remaining attached to the template. Thereafter, the guide pin  184  remains inserted into the condyle  192  as illustrated in  FIG. 9 . 
     To form the cutout that removes the cartilage defect and receives the shaped allograft plug, a shaped drill bit, burr, or cutting disc can be employed. The shape and dimensions of the drill bit, burr or cutting disc, which will determine the shape and dimension of the formed cutout, may correspond to the allograft that is to be transplanted. An embodiment of such a drill bit  200  is illustrated in  FIG. 10 . Disposed along the central axis of the drill bit  200  is a tube or cannula  202  adapted to receive the guide pin. The drill bit  200  also includes a circular counter-bore forming element  204  and a conical-shaped cutting body  206  extending from the counter-bore forming element. The surface of the counter-bore forming element  204  and the cutting body  206  can include flutes or other suitable cutting structures. In other embodiments, to produce differently shaped cutouts, a different drill bit, burr, or cutting disc can be utilized. For example, referring to  FIG. 11 , there is illustrated a cannulated drill bit  210  having a circular counter-bore forming element  214  and a cylindrical cutting body  216 . 
     In use, referring to  FIG. 12 , the conically cannulated drill bit  200  (or burr or cutting disc when used) is slid onto the guide pin  184  and placed proximate the host bone  190  such that the cutting body  204  is proximate the cartilage defect. The drill bit  200  can be rotated as indicated, either by hand or by a powered device, to cut into and remove the cartilage defect and the associated bone material thereby forming the cutout. Where desirable, lubrication can be supplied to facilitate cutting. Referring to  FIG. 13 , the shape of the cutout  220  formed into the host bone  190  will correspond to the shape of the drill bit used including having a conical void  222  and a circular counter bore  224  proximate the surface of the condyle  192 . As will be appreciated, when the cannulated drill bit  210  illustrated in  FIG. 11  is used, the formed cutout will have a corresponding shape including a circular counter-bore and a cylindrical void. In various embodiments, the shaped drill bits, burrs, and cutting disc can be used to make finishing cuts with different devices used to make initial cuts into the recipient site. 
     Referring to  FIG. 14 , a correspondingly shaped conical allograft plug  140  can be inserted into the shaped cutout  220  at the recipient site using a tamp  228  if necessary. Preferably, the allograft plug  140  and cutout  220  are sized to provide a close fit and, more preferably, a slight press fit, when engaged. Once property inserted, the shaped cancellous stalk  144  is received deep into the cutout  220  and thus functions to anchor the allograft plug  140  to the host bone  190 . Additionally, the cartilage plate  142  will be accommodated in the counter bore  224  such that the healthy cartilage of the allograft plug  140  aligns with the healthy cartilage on condyle  192  of the host bone  190 . Overtime, the cancellous tissue and cartilage plate will permanently graft with the healthy bone tissue. 
     While inserting the allograft with a tamp is a common method, any other suitable method can be employed. For example, referring to  FIG. 15 , a method of implanting a conically shaped allograft plug  140  by the use of sutures is illustrated. According to the method, a pair of parallel holes  230  are cut into the outline of the cutout  220  and through to the opposite side of the host bone  190 . A third hole  232  is cut transversely across the cancellous stalk  144  of the conical allograft plug  140 . A flexible suture  234  or line can be run through the hole  232  in the cancellous stalk  144  with the ends of the suture run through holes  230  in the cutout  220  and out the opposite side of the host bone  190 . As will be appreciated, pulling the ends of the suture  234  through holes  230  will draw the allograft plug  140  tightly into the cutout  220 . It will be appreciated that any of the foregoing implantation procedures can work for any of the various shaped allograft plugs and corresponding cutouts. 
     Preparing the recipient site and removing and shaping an allograft plug for transplanting into the recipient site can occur simultaneously or, in some embodiments, the allograft plug can be removed and shaped in advance of preparing the recipient site. Moreover, the preparation of an allograft plug can occur at a different location than the where the insertion of the allograft plug is to occur. To preserve an allograft plug prior to insertion, the allograft plug can be cryogenically preserved. This is an alternative to preparing and transplanting a fresh allograft plug. 
     Though the foregoing procedures for preparing and transplanting a shaped allograft plug can be conducted with any common medical instruments, in a further aspect of the invention, various special instruments and tools, in addition to the template and the shaped drill bit, burr, or cutting discs, are provided. For example, to produce the shaped allograft plug illustrated in  FIG. 2  from a donor bone, a guide plate  240  as illustrated in  FIG. 16  can be used to guide various crown saw cuts into a donor bone  242 . The guide plate includes a generally rectangular base plate  244  that is curved or cambered to fit on a condyle of the donor bone and from one surface of which projects a circular guide cylinder  246 . The guide cylinder  246  defines a hollow bore  248  of a first diameter that is disposed through the base plate  244 . Slidably receivable in the guide cylinder  246  is a smaller second guide cylinder  250  through which is disposed a second hollow bore  252  of a second, smaller diameter. The guide plate  240  also includes a plurality of short sharp teeth  254  projecting from a surface of the base plate  244  opposite the guide cylinder  246 . 
     In use, the guide plate  240  with the second guide cylinder  250  inserted is attached to the donor bone  242  on a surface diametrically opposite of the donor site  243 . The teeth  254  help attach the guide plate to the donor bone  242  and can be inserted into the donor bone by thumb pressure or a light tamp. To produce a first cut into the donor bone  242 , a tubular crown saw  104 ′ having a diameter slightly less than diameter of the second hollow bore  252  of the guide plate  240  is inserted through the second hollow bore and into the donor bone. Preferably, the first cut is made into the donor bone  242  from the location of the guide plate  240  opposite the donor site  243  to a point proximate the cartilage plate of the donor site and more preferably only a few millimeters from the cartilage plate. The second, smaller guide cylinder  250  is then removed from the guide plate  240 . A second crown saw  104 ″, larger than the first crown saw  104 ′ but with a diameter adapted to be slidably received into the first hollow bore  248  of the guide plate  240 , is inserted through the first hollow bore and across the donor bone  242 , thereby detaching a portion of bone tissue  258  from the donor bone. The detached bone tissue can then be trimmed to a desired length, for example, as measured from the cartilage plate to the cancellous tissue, to produce the allograft plug  130  having the cylindrical cancellous stalk  134  as illustrated in  FIG. 2 . Hence, the guide plate helps avoid injury to adjacent normal cartilage on the donor bone. Furthermore, the guide plate  240  can be used in conjunction with a clamping device of the type illustrated and described with respect to  FIG. 1 . In other embodiments, the guide plate  240  can be used with only the first guide cylinder  246  and the second, larger diameter crown saw  104 ″ to produce a cylindrical allograft plug that can be subsequently shaped. 
     To produce an allograft plug having a conical shaped cancellous stalk, as illustrated in  FIG. 3 , a cannulated burring shell can be used in conjunction with a specially adapted sleeve to further remove cancellous tissue from an allograft plug having a cylindrically-shaped stalk. Referring to  FIG. 17 , the cannulated burring shell  260  has a hollow conical shell body  262  with a guide aperture  264  disposed through the tip of the cone to provide the cannulated feature. The cannulated burring shell  264  can also include a circular burring disk  266  that extends annularly outward from the base of the conical shell body  262 . The interior surface of the conical shell body  262  and the underside of the burring disc  266  are adapted to grate or remove cancellous bone tissue. 
     In order to utilize the cannulated feature of the burring shell to facilitate proper shaping of the conical stalk, referring to  FIG. 18 , the specially adapted sleeve  270  is first placed about the cylindrical allograft plug  130 . The sleeve  270  includes a tubular sleeve body  272  and a base plate  274  having a centrally located guide aperture  276  disposed therein. The sleeve  270  is placed about the allograft plug  130  such that the tubular sleeve body  272  receives the cylindrical cancellous stalk  134 . Another elongated guide pin  278  is inserted through the guide aperture  276  and partially into the cancellous tissue of the stalk  134  as illustrated. Due to the concentric relation of the guide aperture and the tubular sleeve body  272 , the guide pin  278  will be concentrically aligned within the cancellous stalk. The sleeve  270  can then be removed and the cannulated burring shell  260  of  FIG. 17 , via its guide aperture  264 , slide onto the guide pin so that the shell body  262  aligns with the cylindrical cancellous stalk. As can be appreciated, rotation of the cannulated burring shell  260  will remove cancellous tissue from the stalk and thereby form the conical shape. Furthermore, the burring disk  266  can remove or smooth the cancellous tissue on the underside of the allograft plug cartilage plate. 
     To handle a shaped allograft plug, especially a cylindrically or conically shaped plug, a pair of specially configure forceps can be provided. Referring to  FIG. 19 , the forceps  280  can include first and second lever arms  282 ,  284  that intersect and are pivotally joined at a pivot point  286 . To grasp and manipulate the forceps, there is formed at the proximal end of each lever arm an eyelet  288  that can accommodate an operators fingers. Traversing the first lever arm  282  is a locking arm  290  that can engage a locking mechanism  292  on the second arm  284  so as to control and fix articulation of the forceps  280 . The forceps  280  can be made from any suitable material such as, for example, stainless steel. 
     Formed at the working ends of the first and second lever arms  282 ,  284  are curved or semicircular clamps  294 ,  296 . The clamps  294 ,  296  can be joined to the respective lever arms  282 ,  284  at any suitable angle such as, for example, in-line with the lever arms or at right angles with the lever arms. To prevent damaging the allograft plug, a suitable soft material  298  such as an elastomer can be coated onto the clamps  294 ,  296 . Preferably the elastomer material can be silicone rubber. Hence, when handling a cylindrical or conical allograft plug, the curved clamps  294 ,  296  can be placed around the cartilage plate or cancellous stalk with the elastomer  298  protecting the bone tissue. 
     To produce a rectilinear shaped allograft plug, such as the rectangular plug illustrated in  FIG. 4 , a special template  300  as illustrated in  FIGS. 20 and 21  can be used. The template  300  includes a plate  302  having a cambered or curved shaped to adapt the plate for attachment to the condyle surface of a donor bone. Protruding from one surface of the plate  302  are a plurality of sharp teeth  304  to assist in attaching the template to the donor bone. The template  300  can further include an engagement structure  306  on the plate surface opposite the protruding teeth  304  to engage a detachable handle as described above. Furthermore, while the illustrated template  300  has a rectangular shape, in other embodiments the template can have other suitable shapes depending upon the shape of the allograft plug desired. 
     To actually remove the allograft plug, there is disposed through the plate  302  and within the perimeter outlined by the sharp teeth  304  a plurality of elongated cut slots  310  that are adapted to accommodate a osteotome, chisel, oscillating saw, or other cutting device. To produce a rectangular allograft plug, the illustrated cut slots  310  are arranged rectangularly. However, in other embodiments, to produce other shaped allograft plugs, such as triangular, the cut slots can be arranged in other patterns, such as triangularly. The cut slots  310  are furthermore disposed into the template  300  on a converging angle such that, when a cutting device is inserted through the cut slots and into the donor bone, the cuts being made will intersect at a point in the cancellous bone tissue. Intersecting the cuts will detach the allograft plug from the donor bone and simultaneously shape the allograft plug and its cancellous stalk. Hence, locating the cut slots  310  within the outline of the teeth  304  enables insertion of the teeth into the donor bone without damaging the healthy cartilage on allograft plug. 
     To prepare a recipient site for receiving an rectilinear allograft plug, a template  320  as illustrated in  FIG. 22  can be used. The plate  322  of the template  320  is similar in shape and configuration to the template  300  of  FIGS. 20 and 21  and also includes a plurality of cut slots  330  disposed angularly there through. To form a cutout in the host bone, the template  320  can be attached to the host bone at a location corresponding to a cartilage defect by utilizing the sharp teeth  324  protruding from the plate  322 . To avoid damaging healthy cartilage on the host bone, the cut slots  330  are preferably located outside of the outline of the teeth  324 . After attachment, various suitable cutting devices can be inserted through the cut slots  330  and into the donor bone to form the cutout. In an embodiment, to enable installation of the guide pin into the recipient site for aligning subsequent operations, the template  320  can have a guide aperture  328  disposed through the plate  322  generally central of teeth  324  and the cut slots  330 . 
     As will be appreciated from the foregoing, the procedures and instruments described may also be applicable to the preparation and transplantation of a shaped autograft plug. For example, the removal, shaping, and insertion of an autograft plug from a host site and into a recipient site within the same patient is readily applicable with respect to rectilinear autograft plugs and can be performed using the same instruments. 
     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.