Abstract:
Osteoarticular allografts are transplanted by techniques which ensure substantial surface contour matching. Specifically, surgical techniques are provided whereby a plug from an osteochondral allograft may be transplanted to a cavity site which remains after a condylar defect is removed from a patient&#39;s condyle. In this regard, the present invention essentially includes placing an osteochondral allograft in substantially the same orientation as the patient condyle, and then removing the transplantable plug therefrom and forming the cavity site in the patient condyle while maintaining their relative same orientation. In this manner, the surface of the transplanted plug is matched to the contour of the excised osteochondral tissue.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to surgical transplant techniques. More specifically, the present invention relates to techniques by which donor osteochondral allografts may be transplanted to a patient recipient.  
         BACKGROUND AND SUMMARY OF THE INVENTION  
         [0002]    Bone transplantation has been a common surgical procedure for a number of years. In this regard, conventional bone transplantation typically involves removing a bone plug from another site from the same patient (i.e., an autograft) and then inserting the plug at a different site in need of the same. Transplantation of bone from another donor (i.e., an allograft) has also been used where autograft bone is not available. Allograft bone is processed in several ways and is available in solid, paste, or particulate matter.  
           [0003]    In recent years, surgeons have been using osteoarticular autografts to repair small defects in the femoral condyle. Small plugs are taken from remote areas of the condyle and transplanted to areas which have defects and are more critical. Osteoarticular allografts, however, have not typically been used because osteoarticular cartilage cells do not survive the freezing or cryopreservation process. Recent advances in preservation of fresh articular cartilage have, however, made the use of osteoarticular cartilage allografts more common.  
           [0004]    Instrumentation for bone plug transplantation has yielded plugs of a specified diameter. See in this regard, U.S. Pat. Nos. 5,782,835 and 5,919,196, the entire content of each being incorporated expressly hereinto by reference. The surface characteristics of autograft plugs have not been a consideration in selection or harvesting. In transplanting articular allografts, however, these surface characteristics are critical. In order for the allograft to be successful, the surface of the transplanted plug must have the same contour as the excised osteochondral tissue. If this contour is not correct, the articular surfaces of both the femur and tibia are at risk for damage.  
           [0005]    According to the present invention, osteoarticular allografts are transplanted by techniques which ensure substantial surface contour matching. Broadly, the present invention is embodied in surgical techniques whereby a plug from an osteochondral allograft may be transplanted to a cavity site which remains after a condylar defect is removed from a patient&#39;s condyle. In this regard, the present invention essentially includes placing an osteochondral allograft in substantially the same orientation as the patient condyle, and then removing the transplantable plug therefrom and forming the cavity site in the patient condyle while maintaining their relative same orientation. In this manner, the surface of the transplanted plug is matched to the contour of the excised osteochondral tissue.  
           [0006]    These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.  
       
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
       [0007]    Reference will hereinafter be made to the accompanying drawings, wherein like reference numerals denote like structural elements, and wherein  
         [0008]    FIGS.  1 - 15  collectively depict in a schematic fashion a particularly preferred transplantation technique according to one embodiment of the present invention; and  
         [0009]    FIGS.  16 - 19  collectively depict in a schematic fashion a transplantation technique according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]    One particularly preferred technique for transplanting osteoarticular allografts according to the present invention is depicted schematically in accompanying FIGS.  1 - 15  In this regard, the patient is prepared initially by the surgeon making an incision along the lateral border of the patella. The patella is drawn back medially in order to expose the patient&#39;s condyle  10 . The condylar defect  12  is visually identified by the attending surgeon and a bone cutter/guide  14  selected which is of sufficient size so as to bound entirely the identified defect  12 . Conventional sizes of the bone cutter/guide  14  that may be selected include, for example, 20, 25, 30 or 35 mm diameter cutters.  
         [0011]    As shown in FIG. 2, the cutter/guide  14  is initially simply rested upon (not pushed against) the surface of the condyle  10 . While in such an initial position (e.g., with the aid of a surgical assistant holding the cutter/guide  14  in place), the Steinmann pin  16  may then embedded into the condyle  10  to a depth of about 25 mm using a conventional surgical drill  18 . Thus, the initial placement of the cutter/guide  14  is to orient the pin  16  perpendicular to the condylar surface. The cutter/guide  14  is thus removed from its contact with the condylar surface to leave the pin projecting outwardly therefrom as shown in FIG. 3.  
         [0012]    A sterile workstation is set up with a vise  20 . The allograft  22  is positioned within the vise  20  so as to be in the same orientation as the patient&#39;s exposed condyle  10 . Specifically, as shown in FIGS. 4 a  and  4   b , the orientation of the allograft  22  is such that an axis  24  perpendicular to the location of the donor section is parallel to the elongate pin  16  embedded in the patient&#39;s condyle  10 . The cutter/guide  14  is then placed over the identical location on the allograft  22  as compared to the patient&#39;s condyle  10  as shown in FIG. 5 a . A second Steinmann pin  26  is then inserted into the cutter/guide  14  as shown in FIG. 5 b . The angle and location of the pin  26  is carefully compared to the angle and location of the pin  16  already embedded in the patient&#39;s condyle (i.e., compare the orientation of pins  16  and  26  in FIGS. 4 b  and  5   b , respectively) and any orientation adjustments are made to ensure that the pins  16 ,  26  are substantially parallel to one another. The pin  26  may then be embedded in the allograft to a desired depth (e.g., about 26 mm) using the drill  18  (not shown in FIG. 5 b , but see FIG. 2).  
         [0013]    Prior to removing the cutter/guide  14 , its entire circumference is traced with an appropriate marker. The cutter/guide is then removed and hash marks are made through the marked circumference on the allograft  22  as shown in FIG. 6 a  to locate the North, South, East and West poles of the allograft plug  22 - 1 . A similar marking technique is employed to mark the condyle plug  10 - 1  of the patient as shown in FIG. 6 b . The North, South, East and West pole markings will be employed later to ensure proper orientation of the allograft plug  22 - 1 . In this regard, the orientation of the markings on both the allograft  22  and the condyle  10  must be substantially identical to one another. If an orientation discrepancy exists, then the pin  26  may be reset in the allograft  22  and fresh markings for the plug  22 - 1  drawn. Once the orientations have been confirmed, the cutter/guide  14  is rotated by hand to drill through both the articulating surface of the patient&#39;s condyle  10  and the allograft  22  as shown in FIGS. 7 a  and  7   b , respectively, until the cutter/guide  14  is against the cortical bone.  
         [0014]    The same size drill bit and coring reamer  30  is then selected from the instrument kit. The drill bit  30  is mounted on the cannulated drill  18  and placed over the Steinmann pin  16  embedded in the patient condyle  10 . The drill bit  30  is advanced through the articular surface of the condyle  10  while under constant irrigation from irrigator  32  and then through the cortical bone into the cancellous bone as depicted in FIG. 8 a . It is preferably that the surgeon examine advancement of the drill bit  30  after every 2-3 mm of depth. Proper depth of cut is achieved when the minimum of cancellous bone along the perimeter is between about 3 to about 4 mm as shown in FIG. 8 b , for example.  
         [0015]    An apertured push-out: plate (not shown) is first inserted over the pin  26  embedded in the allograft  22 , and the allograft is then cored using the coring/reamer bit  34  attached to the cannulated drill  18 . While under constant irrigation from the irrigator  32 , the bit  34  is advanced into the allograft  22  approximately 25 mm (i.e., as determined by the depth marking  34 - 1  on bit  34 ) as shown in FIG. 8 c . Care should be taken to not advance the bit  34  completely through the allograft  22 . The bit  34  is slowly removed from the allograft  22  while under forward rotation and constant irrigation from the irrigator  32 .  
         [0016]    The once drilled with the bit  34 , the allograft  22  is reoriented substantially vertically and the pin  26  removed therefrom. The plug  22 - 1  is excised by transecting the allograft  22  with an oscillating saw (not shown) approximately 20 mm below the allograft&#39;s surface. The initially drilled plug  22 - 1  should be steadied manually during transection to prevent it from abrupt dislocation.  
         [0017]    The depth locations on the North, South, East and West poles (which may or may not be substantially equivalent to one another) corresponding to the respective depths of the prepared site cavity  10 - 2  (see FIG. 8 b ) on the patient&#39;s condyle are marked on the plug  22 - 1  as shown in the left-hand representation of FIG. 9. The depth markers at the poles may then be connected to form a circumferential mark M at the proper plug depth.  
         [0018]    A set of locking pliers P are then used to grip securely the marked allograft plug  22 - 1  such that the circumferential depth marking M is located immediately above the surface of the jaws of the pliers P as shown in FIG. 10. Thereafter, using the jaw faces of the pliers P as a cutting guide, an oscillating saw blade S is advanced from the outside perimeter inwardly along the depth marking M as shown in FIG. 11.  
         [0019]    The severed allograft plug (now identified in FIG. 12 by reference numeral  22 - 2  is removed from the pliers P. The bottom edge  22 - 2   a  is preferably chamfered to assist in fitting the plug  22 - 2  into the cavity site  10 - 2 . In this regard, articular cartilage on the patient&#39;s condyle  10  may slightly migrate to interfere with the press fit dimensions of the plug  22 - 2  within the site cavity  10 - 2 . Thus, the excess cartilage should be removed by reusing the cutter guide  14  along the interior perimetrical edge of the cavity site  10 - 2  as shown in FIG. 13.  
         [0020]    The plug  22 - 2  is oriented so that its North, South, East and West pole markings match the North, South, East and West pole markings on the patient&#39;s condyle  10  as shown in FIG. 14. Any abnormality in shape and/or tissue material that may interfere with the fit of the plug  22 - 2  within the cavity site  10 - 2  should be corrected prior to final insertion. The plug  22 - 2  is press-fit into cavity  10 - 2  by advancing the former into the latter using a cannulated tamping tool T (see FIG. 15). A small mallet may be used in combination with the tamping tool T in order to forcibly push the plug  22 - 2  into the cavity site  10 - 2  on the patient&#39;s condyle  10 . Care should be taken to ensure that all edges of the plug  222  advance substantially equally into the cavity site  10 - 2  and that the plug  22 - 2  does not become angularly canted. Any fragmentary cartilage is then removed around the perimeter of the plug  22 - 2  once seated within the cavity site  10 - 2 . The allograft plug  22 - 2  may then be secured by using a low profile headless surgical screw positioned within the central hole  22 - 2   b  (see FIG. 12) which remains after removal of the pin  26 .  
         [0021]    The various instruments and implements employed in the osteochondral allograft transplant described above are most preferably supplied in kit form. Thus, in accordance with another aspect of this invention, the kit will necessarily include the elongate pins  16 ,  26  which may be inserted into the patient&#39;s condyle  10  and the allograft  22  as described previously. The kit may also contain a sterile clamp  20  so that the allograft  22  with the pin  26  embedded therein may be positionally fixed in parallel to the pin  16  embedded in the patient&#39;s condyle  10 . Multiple coring/reamer bits  30  and/or  34  having different diameters and/or depths may be provided in the kit of this invention to allow the attending surgeon to form a wide range of cavity sites  10 - 2  and/or allograft plugs  22 - 2  to suit the particular patient&#39;s needs.  
         [0022]    As noted previously, the use of the pin  26  in the embodiment described above with reference to FIGS.  1 - 15  will create a central hole  22 - 2   b  (see FIG. 12) which remains after removal of the pin  26  and may be used to provide a site for a low profile headless surgical screw. However, it may be desirable to harvest an allograft plug without such a central hole  22 - 2   b . As shown in accompanying FIGS.  16 - 19 , such an allograft plug may be obtained utilizing an annular guide collar  50  and elongate pins  52  in concert with the drill bit  34  described previously.  
         [0023]    More specifically, as shown in FIG. 16, a drive pin  54  connected operatively to the drill  18  at its proximal end (see FIG. 19) and to the drill bit  34  at is distal end is positioned in substantial parallel alignment with the guide pin  16  (i.e., in a manner similar to that described previously). The drill bit  34  will thus be placed on the surface of the allograft  22  and will circumscribe an area thereon which will match closely the area on the patient&#39;s condyle to be replaced. With the drill bit  34  thereby positioned, an annular guide collar  50  is sleeved over the external surface of the drill bit until it is positioned against the surface of the allograft (see FIG. 17).  
         [0024]    A series of elongate pins  52  may then be passed through respective guide apertures  50 - 1  of the collar  50  and secured into the allograft  22  thereby immobilizing the collar  50  (see FIG. 18). Thereafter, as shown in FIG. 19, the drill  18  may be operatively coupled to the drill bit  34 . The drill bit  34  can then be positioned within the central aperture  50 - 2  of the collar  50  and operated so as to cut a plug of desire depth from the allograft  22 . In such a manner, the central aperture  50 - 2  of the collar serves as a structural guide to the drill bit  32  since their respectively diameters are in close conformance to one another. The allograft plug may then be removed as described above and will not evidence any central hole  22 - 2   b  therein (i.e., since the pin  26  is not employed with this embodiment of the invention.  
         [0025]    Therefore, while the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.