Abstract:
Tools for resecting the femur include an anchoring device, a three-way alignment guide and a six way alignment guide attachable to the anchoring device, a resection guide attachable to the three-way alignment guide and equipped with couplings for trackers, an A-P sizer, a femoral sizing block bushing attachable to the six-way alignment guide, a 4-in-1 femoral cutting block, a 5-in-1 positional alignment guide attachable to the six-way alignment guide, a pair of diodes, and a 5-in-one cutting block. Methods of utilizing the apparatus are also disclosed

Description:
[0001]    This application is related to patent application Ser. No. 09/811,272, filed Mar. 17, 2001, entitled “Tools Used In Performing Femoral And Tibial Resection In Knee Surgery”; patent application Ser. No. 09/811,043, filed Mar. 17, 2001, entitled “Methods Used In Performing Femoral And Tibial Resection In Knee Surgery”; patent application Ser. No. 09/811,042, filed Mar. 17, 2001, entitled “Systems Used In Performing Femoral And Tibial Resection In Knee Surgery”; patent application Ser. No. 09/811,318, filed Mar. 17, 2001, entitled “Apparatus Used In Performing Femoral And Tibial Resection In Knee Surgery” and patent application Ser. No. 09/746,800 filed Dec. 23, 2000, entitled “Methods and Tools For Femoral Resection In Primary Knee Surgery”, the complete disclosures of which are hereby incorporated by reference herein.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to methods and tools used in knee arthroplasty. More particularly, the invention relates to methods and tools used in knee surgery where artificial femoral and tibial components are installed.  
           [0004]    2. Brief Description Of The Prior Art  
           [0005]    Total knee arthroplasty involves the replacement of portions of the patellar, femur and tibia with artificial components. In particular, a proximal portion of the tibia and a distal portion of the femur are cut away (resected) and replaced with artificial components.  
           [0006]    As used herein, when referring to bones or other body parts, the term “proximal” means closest to the heart and the term “distal” means more distant from the heart. When referring to tools and instruments, the term “proximal” means closest to the practitioner and the term “distal” means distant from the practitioner.  
           [0007]    There are several types of knee prostheses known in the art. One type is sometimes referred to as a “resurfacing type”. In these prostheses, the articular surface of the distal femur and proximal tibia are “resurfaced” with respective metal and plastic condylar-type articular bearing components.  
           [0008]    The femoral component is a metallic alloy construction (cobalt-chrome alloy or 6A14V titanium alloy) and provides medial and lateral condylar bearing surfaces of multi-radius design of similar shape and geometry as the natural distal femur or femoral-side of the knee joint.  
           [0009]    One important aspect of these procedures is the correct resection of the distal femur and proximal tibia. These resections must provide planes which are correctly angled in order to properly accept the prosthetic components. In particular, the resection planes must be correctly located relative to three parameters: proximal-distal location, varus-valgus angle, and flexion-extension angle.  
           [0010]    Moreover, following distal resection, the femur must be shaped with the aid of a cutting block. The cutting block must be correctly located relative to internal-external rotation, medial-lateral position, and anterior-posterior position.  
           [0011]    Recently, various computerized systems have been introduced to aid the practitioner during different surgical procedures. A typical system is described in the attached Appendix.  
           [0012]    These systems include multiple video cameras which are deployed above the surgical site and a plurality of dynamic reference frame (DRF) devices, also known as trackers, which are attached to body parts and surgical instruments. The trackers are generally LED devices which are visible to the cameras. Using software designed for a particular surgical procedure, a computer receiving input from the cameras guides the placement of surgical instruments.  
           [0013]    The prior art instruments used for determining the correct planes for tibial and femoral resection in total knee arthroplasty are not well suited for use with computerized systems. The known tools utilize either intra-medullary alignment or extra-medullary alignment and adjustment of the degrees of freedom simultaneously is difficult or impossible. Moreover, in order to be useful with computer aided navigation systems, trackers must be attached to the tools. Existing tools do not permit the attachment of trackers.  
         SUMMARY OF THE INVENTION  
         [0014]    It is therefore an object of the invention to provide methods and tools for performing femoral resection.  
           [0015]    It is also an object of the invention to provide methods and tools for femoral resection which allow location of a cutting guide relative to six parameters.  
           [0016]    It is another object of the invention to provide methods and tools for femoral resection which are infinitely adjustable.  
           [0017]    It is still another object of the invention to provide methods and tools for femoral resection which are adapted to be used with computer aided navigation systems.  
           [0018]    In accord with these objects which will be discussed in detail below, the tools according to a first embodiment of the present invention include an anchoring device for attachment to the femur and, a three-way alignment guide attachable to the anchoring device and adjustable relative to three parameters, a resection guide attachable to the alignment guide and equipped with couplings for trackers, an adjustable anterior-posterior sizer, a distal-proximal medial-lateral positioning guide, a medial-lateral cam lock, an anterior-posterior positioning guide, a femoral sizing block bushing, and femoral cutting guide.  
           [0019]    The tools according to a second embodiment of the present invention include an anchoring device for attachment to the femur and, a six-way alignment guide attachable to the anchoring device and adjustable relative to six parameters, a pivotal 5-in-1 positional alignment jig attachable to the alignment guide and equipped with couplings for trackers, a pair of mounting diodes attachable to the epicondylar region of the femur, and a 5-in-1 cutting guide mountable on the diodes.  
           [0020]    A first embodiment of the methods of the invention includes operating the computer aided navigation apparatus in the conventional manner including attaching one or more trackers to the bone to be resected; choosing a location for the anchoring device with or without guidance from the computer and installing the anchoring device; attaching the three-way alignment guide to the anchoring device; attaching a resection guide to the alignment guide; attaching one or two trackers to the resection guide; locating the resection guide with the aid of the alignment guide and the computer; fixing the resection guide to the bone with pins through the rotatable pin guides; and resecting the bone.  
           [0021]    After the bone is resected, the adjustable anterior-posterior sizer is used to size the femur.  
           [0022]    Next, the distal-proximal medial-lateral positioning guide, medial-lateral cam lock, anterior-posterior positioning guide, and femoral sizing block bushing are attached to the alignment guide.  
           [0023]    The distal-proximal medial-lateral positioning guide, medial-lateral cam lock, and anterior-posterior positioning guide, when attached to the three-way guide, convert the three-way guide into a six-way guide. A tracker is preferably attached to the femoral sizing block bushing. The position of the bushing is adjusted in proximal-distal, varus-valgus, medial-lateral, and anterior-posterior directions. Two holes are drilled using the bushing as a guide. The femoral cutting guide is attached to the holes and the anterior and posterior cuts and chamfer cuts are made.  
           [0024]    A second embodiment of the methods of the invention includes operating the computer aided navigation apparatus in the conventional manner including attaching one or more trackers to the bone to be resected; choosing a location for the anchoring device with or without guidance from the computer and installing the anchoring device; attaching the six-way alignment guide to the anchoring device; attaching the pivotal 5-in-1 positional alignment jig to the alignment guide; attaching a tracker to the jig; positioning the jig in the varus-valgus, flexion-extension, internal-external rotation, distal-proximal, and anterior-posterior directions; drilling four holes in the epicondylar region using the jig as a guide; removing the jig, the alignment guide, and the anchoring device; installing a pair of diodes in the epicondylar region with screws in the holes; and mounting the 5-in-1 cutting guide on the diodes.  
           [0025]    The 5-in-1 cutting guide is then used to perform all of the femoral cuts as described in previously incorporated application Ser. No. 09/746,800. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 is a broken perspective view of the distal femur with an anchoring device according to the invention;  
         [0027]    [0027]FIG. 2 is a side elevational view of the anchoring device installed in the distal femur;  
         [0028]    [0028]FIG. 3 is a perspective view of the anchoring device installed in the distal femur with a three-way alignment guide according to the invention not yet attached to the anchoring device;  
         [0029]    [0029]FIG. 4 is a view similar to FIG. 3 showing the alignment guide attached to the anchoring device;  
         [0030]    [0030]FIG. 5 is a perspective view showing a first embodiment of a resection guide according to the invention not yet attached to the three-way alignment guide;  
         [0031]    [0031]FIG. 6 is a perspective view showing a first embodiment of a resection guide according to the invention attached to the three-way alignment guide;  
         [0032]    [0032]FIG. 7 is a side elevational view showing a first embodiment of a resection guide according to the invention attached to the three-way alignment guide;  
         [0033]    [0033]FIGS. 8 and 8A are perspective views of an anterior-posterior sizer;  
         [0034]    [0034]FIG. 9 is an exploded perspective view of the distal-proximal medial-lateral positioning guide, medial-lateral cam lock, anterior-posterior positioning guide, and femoral sizing block bushing;  
         [0035]    [0035]FIG. 10 is a plan view of the distal-proximal medial-lateral positioning guide, medial-lateral cam lock, anterior-posterior positioning guide, and femoral sizing block bushing coupled to the alignment guide;  
         [0036]    [0036]FIGS. 11 and 12 are perspective views of the distal-proximal medial-lateral positioning guide, medial-lateral cam lock, anterior-posterior positioning guide, and femoral sizing block bushing coupled to the alignment guide;  
         [0037]    [0037]FIG. 13 is a side elevation view of the distal-proximal medial-lateral positioning guide, medial-lateral cam lock, anterior-posterior positioning guide, and femoral sizing block bushing coupled to the alignment guide;  
         [0038]    [0038]FIGS. 14 and 15 are perspective views of a femoral cutting guide;  
         [0039]    [0039]FIG. 16 is an exploded perspective view of a pivotal 5-in-1 positional alignment jig and five-way alignment guide;  
         [0040]    FIGS.  17 - 19  are perspective views of the pivotal 5-in-1 positional alignment jig and five-way alignment guide coupled to the anchoring device;  
         [0041]    [0041]FIG. 20 is a perspective view of a pair of diodes coupled to the epicondylar region of the femur; and  
         [0042]    [0042]FIG. 21 is a perspective view of a 5-in-one cutting block mounted on the diodes. 
     
    
     BRIEF DESCRIPTION OF THE APPENDIX  
       [0043]    The attached ten page Appendix describes the parts and assembly of a computer navigation system suitable for use with the invention.  
       DETAILED DESCRIPTION  
       [0044]    Turning now to the Figures, the apparatus of the invention will be best understood by a description of the methods of the invention with reference to the Figures. As shown in FIGS. 1 and 2 an anchoring device  10  is installed in the bone  1  in a region proximal to the lateral anterior cortex and within the incision. The location for the anchoring device may be chosen by eye or with the aid of the tracking/navigation software, with an emphasis on paralleling the anchoring device body to the sagital plane. As shown in the Figures, the anchoring device  10  is a pin which is screwed into the bone. Other anchoring devices such as plates could be used, however.  
         [0045]    With the anchoring device  10  in place, the alignment guide  12  is lowered on to it as shown in FIGS.  3 - 5 . As seen best in FIG. 5, the alignment guide  12  has three cam locks  12   a,    12   b,    12   c.  The cam lock  12   a  allows the alignment guide to be adjusted according to flexion-extension angle relative to the anchoring device  10 . The cam lock  12   b  allows the alignment guide to be adjusted according to varus-valgus angle relative to the anchoring device  10 . The cam lock  12   c  opens the end of the alignment device to receive the resection guide  14  shown in FIGS.  5 - 7  and also allows for distal-proximal adjustment.  
         [0046]    Referring now to FIGS.  5 - 7 , the resection guide  14  has a cutting guide surface  14   a,  an attachment rod  14   b,  a pair of connectors  14   c,    14   d  for connecting trackers (not shown), a pair of rotatable pin guides  14   e,    14   f,  and a pair of fail safe mounting bores  14   g,    14   h.  The resection guide  14  is attached to the alignment guide  12  by opening cam lock  12   c  and inserting the attachment rod  14   b  into the alignment guide. It will be appreciated that the cam lock  12   c  allows proximal-distal positioning of the resection guide  14 . After the resection guide  14  is attached to the alignment device  12 , a tracker is attached to the guide  14 .  
         [0047]    With the tracker attached, the first cam lock  12   a  is opened and the resection guide is moved in the varus-valgus plane until the navigation software indicates the proper alignment. The cam lock  12   a  is then locked. Cam lock  12   b  is unlocked and the resection guide is moved in the flexion-extension plane until the navigation software indicates the proper alignment. The cam lock  12   b  is then locked.  
         [0048]    Lastly, the cam lock  12   c  is opened and the resection guide is positioned in the proximal-distal plane until the navigation software indicates the proper alignment. The cam lock  12   c  is then locked. With the resection guide properly located, it may be affixed to the bone with pins (not shown) via the rotatable pin guides  14   e,    14   f.  The pin guides are rotatable so that the practitioner may choose the best site for inserting a pin. The next step in the procedure is to resect the distal end of the femur using the resection guide  14 .  
         [0049]    Those skilled in the art will appreciate that if the anchor pin  10  is not substantially parallel to the sagital plane, the steps may need to be repeated to tune out error introduced by the misaligned anchor pin. One possible solution is to install the pin with a drill having an attached tracker thereby allowing the navigation software to guide the placement of the pin.  
         [0050]    Following distal femoral resection, the femur is sized using either of the following methods:  
         [0051]    1) Conventional sizing using either the Monogram or X-celerate sizing guides is performed. Surface digitization of the posterior condyles must be performed by the surgeon using the pointer by running the pointer tip over the posterior condylar bone and/or cartilage. The sizing guide is placed flush on the resected distal femur with the posterior skids against the posterior condyles. Either the sizing stylus or blade runner (or saw blade) is used to measure the most prominent aspect of the femoral lateral cortex. The femoral sizing block bushing can now be navigated.  
         [0052]    An exemplary sizing guide  15  is shown in FIGS. 8 and 8 a.  The adjustable A-P sizer  15  sets internal-external rotation and also allows an AP movement of +/−2 mm. This instrument is used after the femoral distal cut is performed. The feet  15   a,    15   b  are inserted under the posterior condyles. The jig is allowed to move through six degrees either internally or externally as shown by the indicia between the letters “L” and “R”.  
         [0053]    A blade runner is introduced into one of the slots (labeled in 3, 5, 7, 9, 11, and 13 mm). The slot selected is the one that gives the required run-out anteriorly. If the surgeon is in between sizes, if he goes down a size, he will notch the femur, or if he moves up a size he will leave a gap. The jig allows the surgeon to obtain the optimal position.  
         [0054]    2) Alternatively, software algorithms are used to size the femur. Surface digitization of the trochlear groove (patella track) and posterior condyles are performed by the surgeon using the pointer by running the pointer tip over the posterior condylar bone and/or cartilage. Digitized data is analyzed in the sagital plane. Direct correlation to (or matching of) the correct femoral component is achieved via the software coding/algorithms. The surgeon will be able to visualize the matching on the operating room computer monitor (graphical interface). Sizing is complete using solely digitization methods. The femoral sizing block bushing can now be navigated.  
         [0055]    Turning now to FIGS.  9 - 13 , after the distal femur is resected and sizing is completed, the appropriately sized femoral sizing block bushing  16  is attached to the alignment guide  12  using an anterior-posterior positioning guide  18  having a cam lock  18   a,  a medial-lateral cam lock  20 , and a distal-proximal medial-lateral positioning guide  22 . The bushing  16  has a vertical shaft  16   a,  a pair of drill guides  16   b,    16   c,  and a tracker coupling  16   d.  The vertical shaft  16   a  is inserted into the anterior-posterior positioning guide  18  which is coupled to the medial-lateral cam lock  20  which is slidably coupled to the distal-proximal medial-lateral positioning guide  22 .  
         [0056]    A tracker (not shown) is coupled to the coupling  16   d.  Using the cam locks, the distal-proximal position is set by manually presenting the bushing  16  to the resected face of the femur. The internal-external rotation is navigated and the cam lock is locked on the positioning guide. The medial-lateral positioning of the bushing is navigated and locked using the medial-lateral cam lock  20 . Finally, anterior-posterior positioning is navigated and locked with the cam lock  18   a.  Verification of the navigated position is done in conjunction with the screens on the computer. Once satisfied with the navigated position, two holes are drilled through the drill guides  16   b,    16   c.  The complete anchoring mechanism is removed and the appropriate femoral cutting block is attached.  
         [0057]    [0057]FIGS. 14 and 15 illustrate an exemplary cutting block  24 . The cutting block  24  has a pair of pins  24   a,    24   b  which are impacted into the holes drilled with the bushing  16  (described above).  
         [0058]    Additional fixation holes  24   c - 24   f  are provided for optional fixation with pins. The cutting guide has four guiding surfaces: the anterior cut guiding surface  24   g,  the posterior cut guiding surface  24   h,  the anterior chamfer cut guiding surface  24   i,  and the posterior chamfer cut guiding surface  24   j.  After these four cuts are made, the cutting block is removed and the femur is near ready for accepting the prosthesis.  
         [0059]    A second embodiment of the methods and tools of the invention is illustrated with reference to FIGS. 16 through 21. The second embodiment utilized the same anchoring device  10 , alignment guide  12 , and the alignment devices  18 ,  20 ,  22  with a minor alteration. The anterior-posterior alignment device  18 ′ shown in the Figures has its cam lock  18 ′ a  oriented in a slightly different position than the cam lock  18   a  on the alignment device  18 . According to this embodiment, the devices  12 ,  18 ′,  20 , and  22  are assembled to provide what amounts to a six-way alignment guide. Further according to this embodiment, a pivotal 5-in-1 positional alignment jig is provided which includes the components  26 ,  28 , and  30 . Component  26  is a T-bar having a vertical shaft  26   a,  a lateral arm  26   b  and a medial arm  26   c.  Component  28  is a medial drilling guide arm having a mounting hole  28   a,  a set screw  28   b,  and drill guides  28   c.  Component  30  is a lateral drilling guide arm having a mounting hole  30   a,  a set screw  30   b,  and drill guides  30   c.    
         [0060]    After the femur is digitized as described above with reference to the first embodiment, the components are assembled as shown in FIGS.  17 - 19 . A tracker (not shown) is attached to one of the set screws  28   b,    30   b.    
         [0061]    Using the various CAM locks, the medial and lateral drilling guides  28 ,  30  are positioned in the following directions in the following order: varus-valgus, flexion-extension, internal-external rotation, distal-proximal, and anterior-posterior directions.  
         [0062]    More particularly, the sequential locking of the guide begins with flexion-extension. The cam lock  12   b  is opened and the jig is navigated until the recommended position is reached. Once reached, the flexion-extension cam lock  12   b  is engaged.  
         [0063]    Next, varus-valgus lock  12   a  is opened and flexion-extension is navigated. The jig is navigated until the recommended position is reached. Once attained, the varus-valgus cam lock  12   a  is engaged. Next, internal-external rotation is navigated.  
         [0064]    The cam lock  12   c  is opened and the jig is navigated until the recommended positions are reached.  
         [0065]    Once attained, the internal-external rotation and distal-proximal translation are engaged. Next, anterior-posterior positioning is navigated. The cam lock  18   a  is opened and the jig is navigated until the recommended position is reached. Once attained, the anterior-posterior cam lock  18   a  is engaged. The medial-lateral positioning is not performed until the 5-in-1 cutting guide is attached as described below with reference to FIG. 21.  
         [0066]    After the drilling guides are positioned, four holes are drilled into the epicondylar region using the drill guides  28   c,    30   c.  All of the devices are then removed from the femur.  
         [0067]    Referring now to FIG. 21, a pair of diodes  32 ,  34  are installed in the epicondylar region with screws (not shown), in the holes which were drilled in the previous step, using a screwdriver  36 .  
         [0068]    Turning now to FIG. 21, a 5-in-1 cutting guide  38  is mounted on the diodes as described in previously incorporated application Ser. No. 09/746,800. Prior to fixing the cutting guide with pins, the medial-lateral position of the guide is fine tuned by the surgeon. The 5-in-1 cutting block is then pinned in position and is used to perform all of the femoral cuts as described in previously incorporated application Ser. No. 09/746,800.  
         [0069]    There have been described and illustrated herein methods and tools for resection of the distal femur. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. For example, the first two positioning steps may be reversed in sequence, provided that the navigation software is suitable modified. Moreover, the clamps on the alignment guides need not be cam locks, but could be other types of clamps. Although the apparatus has been described as separate pieces (e.g. the anchor, the alignment guide, and the resection guide), it could be two pieces or a single piece. In general, the methods and tools of the invention could be used with other joints other than the knee. It is believed that the methods and tools could be used in arthroplasty of the hip, shoulder, elbow, etc.