Abstract:
A surgical procedure according to which a cutting blade is positioned over an area of the bone to be cut and indicia is projected onto the area. The blade is adjusted relative to the area until the indicia takes a predetermined configuration on the area corresponding to the desired position of the blade relative to the area. Then the blade can be driven to cut an opening in the bone.

Description:
BACKGROUND  
       [0001]     This invention relates to an improved osteochondral implant procedure and device, and more particularly, to such a procedure and device in which a recipient opening is prepared for receiving a graft.  
         [0002]     In the human body, the knee consists of three bones—a femur, a tibia, and a patella—that are held in place by various ligaments. The corresponding chondral areas of the femur and the tibia form a hinge joint, and the patella protects the joint. Portions of the latter areas, as well as the underside of the patella, are covered with an articular cartilage, which allow the femur and the tibia to smoothly glide against each other without causing damage.  
         [0003]     The articular cartilage often tears, usually due to traumatic injury (often seen in athletics) and degenerative processes (seen in older patients). This tearing does not heal well due to the lack of nerves, blood vessels and lymphatic systems; and the resultant knee pain, swelling and limited motion of the bone(s) must be addressed.  
         [0004]     Damaged adult cartilages have historically been treated by a variety of surgical interventions including lavage, arthroscopic debridement, and repair stimulation, all of which provide less than optimum results.  
         [0005]     Another known treatment involves removal and replacement of the damaged cartilage with a prosthetic device. However, the known artificial prostheses have largely been unsuccessful since they are deficient in the elastic, and therefore in the shock-absorbing, properties characteristic of the cartilage. Moreover, the known artificial devices have not proven able to withstand the forces inherent to routine knee joint function.  
         [0006]     In an attempt to overcome the problems associated with the above techniques, osteochondral transplantation, also known as “mosaicplasty” has been used to repair articular cartilages. This procedure involves removing injured tissue from the damaged area and drilling openings in the underlying bone. One or more plugs, consisting of healthy cartilage overlying bone, are obtained from another area of the patient, typically from a lower weight-bearing region of the joint under repair, or from a donor patient, and are implanted in the openings. In order to insure a precise fit between the plug and the opening, it is important that the opening is perpendicular to the plane of the bone. However, the curvature of the condyle of the fibia makes this difficult.  
         [0007]     An embodiment of the present invention involves a technique for insuring that the opening formed in the bone to receive the plug extends perpendicularly to the plane of the bone. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0008]      FIG. 1  is an elevational view of a human knee with certain parts removed in the interest of clarity.  
         [0009]      FIG. 2  is an exploded, partial sectional-partial elevational view of a chisel extending over the femur of the knee of  FIG. 1  and depicting a laser beam projecting from the chisel onto the femur.  
         [0010]      FIG. 3  is an isometric view of the chisel and femur of  FIG. 2 .  
         [0011]      FIGS. 4   a  and  4   b  depict two different projections of the laser beam onto the surface of the femur. 
     
    
     DETAILED DESCRIPTION  
       [0012]     Referring to  FIG. 1  of the drawing, the reference numeral  10  refers, in general, to a knee area of a human including a femur  12  and a tibia  14  whose respective chondral areas are in close proximity. A cartilage  16  extends over a portion of the chondral area of the femur  12 , and a meniscus  18  extends between the cartilage and the tibia  14 . The patella, as well as the tendons, ligaments, and quadriceps that also form part of the knee, are not shown in the interest of clarity.  
         [0013]     Referring to  FIG. 2  which depicts the femur  12  of  FIG. 1  in an inverted position, it will be assumed that a portion of the cartilage  16  extending over a chrondral area of the femur  12 , has been damaged and removed by the surgeon, or has worn away, leaving a damaged area, or defect  12   a . It will also be assumed that it is desired to create an opening, or series of openings, extending from the condyle of the defect  12   a  into the corresponding chondral area of the femur  12  to receive a graft or grafts.  
         [0014]     It is understood that one or more grafts are harvested from another area of the patient/recipient, such as an undamaged non-load bearing area of the femur or tibia, or from a corresponding area of a donor, in accordance with known techniques. These grafts are sized so as to be implantable in the above openings in accordance with the following.  
         [0015]     Referring to  FIGS. 2 and 3 , a chisel system is referred to, in general, by the reference numeral  20  and includes a hollow cylindrical body member  22  having a handle  24  formed integrally with the body member, or attached to the body member in any conventional manner.  
         [0016]     The chisel system  20  is shown in proximity to the femur and, for the convenience of presentation, the femur  12  is shown inverted from the position shown in  FIG. 1 . The chisel system  20  also includes a hollow blade  26  extending from the other end of the body member  22  which can be of the type disclosed in co-pending U.S. patent application Ser. No. (attorney&#39;s docket no. 31132.437). The blade  26  can be formed integrally with the body member  22 , or it can be attached to the body member in any conventional manner. The cross section of the blade  26  can take any configuration corresponding to the cross-section of the plug to be implanted, and for the purpose of example, it will be assumed that the cross-section of the blade  26  is rectangular.  
         [0017]     Inasmuch as the surface of the defect  12   a  is curved, it is a challenge to insure that the blade  26  extends perpendicularly to the plane of the defect before the above opening is cut by the blade. To this end, a laser system is provided in the body member  22  and consists of a laser beam projector  28  supported at one end of the housing  30  which, in turn, is mounted in the interior of the body member  22 . The housing  30  contains electronics associated with the operation of the projector  28 .  
         [0018]     The projector  28  is located in the end portion of the body member  22  adjacent the blade  26  and, when activated by a simple switch (not shown), or the like, associated with the body member, is adapted to project indicia shown, in general, by the reference numeral  34 , and described in detail later, onto the defect  12   a . The laser system will not be described in any further detail since it is conventional and could be in the form of the model PLS 2  Palm Laser manufactured by Pacific Laser Systems of Sausalito, Calif.  
         [0019]     As better shown in  FIGS. 4   a  and  4   b , the projector projects indicia  34 , which takes the form of a crosshair, consisting of two mutually perpendicular lines  34   a  and  34   b , when projected onto a flat surface that is perpendicular to the axis of the projector.  FIG. 4   a  depicts the lines  34   a  and  34   b  when the axes of the projector  28 , and therefore the blade  26  of the chisel system  20 , are not perpendicular to the plane of the defect  12   a . This is manifested by the line  34   b  not being horizontal and therefore not being perpendicular to the line  34   a , but rather indicates that the blade  34   a  is tilted slightly in one plane from a perfectly perpendicular position.  
         [0020]      FIG. 4   b  depicts the lines  34   a  and  34   b  when the blade  26  is perpendicular to the plane of the femur  12 . This is manifested by the lines  34   a  and  34   b  extending perpendicular to each other, with line  34   a  extending vertically (as viewed in the drawing), and line  34   b  extending horizontally. With this projection, the surgeon is insured that the blade  26  is perpendicular to the plane of the femur so that, when the blade is advanced to the defect  12   a  and driven into the femur, an opening is cut in the femur that is perpendicular to the plane of the defect. Therefore when the above-mentioned graft is inserted in the opening, the cartilage portion of the graft is located in substantially the same position as the original damaged cartilage.  
         [0021]     In operation, the chisel system  10  is positioned near the defect  12   a  with the distal end of the blade extending adjacent the defect. The projector  30  is activated to project the indicia  34  on the defect  12   a . The angular position of the chisel system  20 , and therefore the axis of the projector  28  and the blade  26  relative to the defect  12   a , is adjusted until the lines  34   a  and  34   b  extend perpendicular to each other as shown in  FIG. 4   b . The blade  26  is then driven into the femur  12  to cut an opening in the femur that is perpendicular to the plane of the defect  12   a . Therefore, when the above-mentioned graft is inserted in the opening, it will also extend perpendicular to the plane of the femur with the cartilage portion of the graft located in substantially the same position as the original damaged cartilage.  
       Variations  
       [0022]     1. The shape and dimensions of the blade  26  can vary within the scope of the invention. For example, the blade  26 , and therefore the opening to be cut, can have a circular cross section.  
         [0023]     2. The form of the indicia  34  projected by the projector  28  can vary. Examples include a circle, a single line, two or more parallel lines, a square, two or more concentric circles, a dot matrix, etc.  
         [0024]     3. The desired position of the blade relative to the defect can be a position other than the perpendicular position discussed above. For example, it may be desired to cut an opening in the femur  12  that extends at an angle to the plane of the defect, in which case the indicia would be changed accordingly.  
         [0025]     3. The spatial references mentioned above, such as “upper”, “lower”, “under”, “over”, “between”, “outer”, “inner” and “surrounding” are for the purpose of illustration only and do not limit the specific orientation or location of the components described above.  
         [0026]     Those skilled in the art will readily appreciate that many other variations and modifications of the embodiment described above can be made without materially departing from the novel teachings and advantages of this invention. Accordingly, all such variations and modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.