Patent Abstract:
A method and apparatus for repairing isolated chondral defects using synthetic implants. Lesions in articular tissue are corrected by forming a recipient socket in the tissue. A donor graft of a size corresponding to the recipient socket is harvested from a synthetic specimen made of a synthetic tissue material, such as poly (vinyl) alcohol hydrogel. The donor graft is implanted into the recipient socket.

Full Description:
The present application claims the benefit of U.S. provisional application No. 60/403,472, filed Aug. 15, 2002, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the surgical treatment of isolated articular chondral defects and, more specifically, to methods and instruments for replacement of articular cartilage in the knee using grafts harvested from a synthetic tissue specimen. 
     2. Description of the Related Art 
     Methods and apparatus for surgical treatment of isolated articular chondral defects by autograft and allograft transplantation are known. See, for example, U.S. Pat. Nos. 5,919,196, 6,591,581, and 6,592,588, having common assignment with the present application. 
     Various synthetic biomaterials are known. One of these, Salubria™, is an elastic biomaterial sold by Salumedica of Atlanta, Ga. Salubria™ is a poly (vinyl) alcohol hydrogel composition which is similar to human tissue in its mechanical and physical properties. See U.S. Pat. Nos. 5,981,826; 6,231,605; and published Application No. U.S. 2001/0029399, the disclosures of which are incorporated herein by reference. 
     The Salubria™ organic polymer-based material is highly biocompatible and hydrophilic (water loving); it contains water in similar proportions to human tissue. Although Salubria is soft and compliant like human tissue, it has proven to be exceptionally wear resistant and strong, making it an ideal implant material. 
     Salubria™ can withstand millions of loading cycles, yet it is soft enough to match the compliance of normal biological tissue. These properties allow Salubria™ to be molded into anatomic shapes and sterilized, making it usefuil for orthopedic applications. 
     It would be advantageous to have methods and systems for utilizing synthetic grafts in the repair of isolated chondral defects. 
     SUMMARY OF THE INVENTION 
     The present invention provides methods and apparatus for repair of isolated chondral defects using a synthetic substance, preferably a synthetic osteochondral graft material, such as Salubria™. The procedure can be utilized, for example, to anatomically re-establish a structural load-bearing surface to a damaged load bearing surface of the femoral condyle using implants harvested from synthetic anatomical specimens. Partial and full-thickness osteochondral lesions, 1.5-3.5 centimeters in diameter, are particularly amenable to treatment according to the methods of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a surgical step of sizing a lesion according to the present invention; 
         FIG. 2  illustrates a surgical step of marking an articular surface according to the present invention; 
         FIG.3  illustrates a surgical step of drilling a guide pin into bone according to the present invention; 
         FIG. 4  illustrates a surgical step of marking a synthetic hemi-condyle according to the present invention; 
         FIG. 5  illustrates a surgical step of scoring peripheral cartilage according to the present invention; 
         FIG. 6  illustrates a surgical step of boring into bone to form a recipient socket site according to the present invention; 
         FIG. 7  illustrates a surgical step of securing the synthetic hemi-condyle in a workstation according to the present invention; 
         FIG. 8  illustrates a surgical step of harvesting a core from the synthetic hemi-condyle secured in the workstation according to the present invention; 
         FIG. 9  illustrates a surgical step of transferring depth measurements to the core according to the present invention; 
         FIG. 10  illustrates a surgical step of cutting the harvested core to length according to the present invention; 
         FIG. 11  illustrates a surgical step of dilating the recipient socket site according to the present invention; 
         FIG. 12 . illustrates a surgical step of placement of the harvested core into the recipient socket using a delivery tube according to the present invention; and 
         FIG. 13  illustrates a complete core implant according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the present invention, a synthetic tissue specimen, such as an entire artificial distal femur, condyle, or hemi-condyle is created from synthetic biomaterial, such as Salubria™, and is delivered to a surgeon along with a set of surgical socket-forming and donor graft harvesting instrumentation. The tissue specimen is formed to closely approximate the anatomical tissue being repaired. The surgeon uses the instrumentation to fashion donor graft from the tissue specimen for osteochondral repair. The procedure is described below, with reference to the accompanying drawings. 
     Referring first to  FIG. 1 , following standard pre-operative examination and diagnostic studies confirming the size and extent of the lesion  2  on an articular surface of femoral condyle  3 , a standard para-patellar arthrotomy is carried out to expose the defect. Cannulated sizers  4  in various diameters are selected to estimate and approximate coverage of the lesion  2 . Sizers  4  preferably are provided in 15, 18, 20, 25, 30, and 35 mm sizes. 
     Referring to  FIG. 2 , once the appropriate size for the recipient socket is determined, a marker  5  is used to form a circumferential mark  6  on the condyle  3  around the cylinder of sizer  4 . As shown in  FIG. 3 , a guide pin  8  is drilled through the sizer  4  past the lesion  2  and into bone. The sizer  4  is removed and a reference mark  10  is placed in a superior 12:00 o&#39;clock position. See  FIG. 3 . 
     Referring to  FIG. 4 , markings are placed on a synthetic hemi-condyle  11  using the sizer  4  which was previously utilized to establish the recipient defect size and mark the condyle  3 . The sizer  4  is placed over the synthetic hemi-condyle  11  and is used to circumferentially mark  12  the surface of the hemi-condyle  11  in an area corresponding to that of the lesion  2  on the damaged articular surface of condyle  3 . The sizer is removed and a reference mark  13  is placed in a superior 12:00 o&#39;clock position on the inside of the circle mark  12  on the hemi-condyle  11 . 
     Referring to  FIG. 5 , the sizer is replaced with an appropriately sized recipient harvester  14 . The peripheral cartilage on the condylar surface is scored to the underlying subchondral bone. Scoring the peripheral cartilage obviates ancillary damage to the undamaged, peripheral articular surface. The harvester  14  is removed, leaving the guide pin  8  in place. 
     Referring to  FIG. 6 , a cannulated calibrated recipient counterbore  16  is secured to the drill and placed over the drill pin  8 . Recipient socket  17  ( FIG. 9 ) is drilled into the lesion  2  and subchondral bone to a depth of 8 to 10 mm. Bleeding subchondral surfaces should be confirmed. 
     Preparation of the donor graft is described with reference to  FIGS. 7-10 . Referring to  FIG. 7 , donor condyle  11  is secured in a workstation  18 . As shown in  FIG. 8 , a workstation bushing  20  of corresponding size is placed into a top housing  21  over the donor hemi-condyle  11  and set to the exact angle necessary to match the recipient&#39;s contour. The housing  21  is fastened securely. 
     A calibrated donor harvester  22  is connected to a drill and passed through the bushing  20  into the proximal graft housing  21  and rested upon the surface of the donor condyle  11 . The harvester  22  is drilled through the entirety of the donor hemi-condyle  11 . The harvester  22  is removed from the graft housing, securely holding the corresponding cylindrical donor graft core  24 , which can be visualized through slot  25 . Donor graft  24  is extracted gently from the harvester  22  so as not to disturb the articular surface or underlying subchondral bone. 
     Referring to  FIG. 9 , a depth measurement guide  26  is used to measure the recipient depth in four quadrants: north, south, east and west. The depth measurements. are transferred to the synthetic graft core  24 , which is appropriately measured and marked  27  by referencing the four quadrant depths recorded from the recipient socket  17  that was created. 
     Referring to  FIG. 10 , the donor graft  24  is secured in holding forceps  28  and trimmed by a reciprocating saw  30  to achieve the appropriate press fit accommodation of the recipient socket depth. The donor graft  24  is positioned with the articular surface inferior to cut. 
     Referring to  FIG. 11 , a calibrated dilator  32  is inserted into the recipient socket site  17  to achieve a one half mm socket dilation. The end of the dilator is lightly tapped with a mallet. Dilation will also smooth the recipient socket surfaces. 
     Referring to  FIG. 12 , once the precise depth of the donor plug (matching the recipient socket) is obtained, the donor plug  24  is line to line fitted with reference to the marks  10  and  13  into the recipient socket. Cancellous graft is inserted into the bed prior to insertion of the donor plug, if necessary. The donor graft  24  is inserted into a slotted, transparent, calibrated delivery tube  29  for insertion into the recipient socket  17 . A tamp corresponding to the graft&#39;s size is positioned against the plug. Gentle taps are recommended for seating the graft  24  into the socket  17 . Referring to  FIG. 13 , the plug  24  is implanted until all edges are flush with the surrounding cartilage rim. 
     In situations necessary for plug removal, a graft retriever may be secured into the plug to facilitate extraction. At the conclusion of the procedure, the wound is closed in a routine fashion. Sterile dressing and a protective brace are applied during the initial wound-healing phase. Ambulation with the use of crutches and weight-bearing allowances are determined based on the size and the extent of the weight-bearing lesion reconstructed. 
     Although the present invention has been described in connection with preferred embodiments, many modifications and variations will become apparent to those skilled in the art.

Technology Classification (CPC): 0