Abstract:
Apparatus for performing an open wedge, low femoral osteotomy, the apparatus comprising an osteotomy guide, a hinge pin and an osteotomy implant, the osteotomy guide comprising: anterior and posterior tissue shields having (i) openings for receiving the hinge pin and defining the hinge pin axis, and (ii) profiles configured to enable fluoroscopic alignment of the hinge pin axis parallel to the sagittal plane of the patient, a cutting guide comprising a cutting slot for defining a cutting plane extending parallel to, and through, the hinge pin axis, and a drill guide comprising a hole for forming a guide hole in the femur which extends substantially perpendicular to the cutting plane, the hinge pin comprising an elongated body, and the osteotomy implant for positioning in a wedge-shaped opening formed about the cutting plane and for receiving a screw extending through the guide hole.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
       [0001]    This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 60/872,116, filed Dec. 1, 2005 by Justin R. Taber for METHOD, INSTRUMENTATION AND FIXATION FOR LATERAL OPENING WEDGE OSTEOTOMY OF THE DISTAL FEMUR (Attorney&#39;s Docket No. NOVAK-21 PROV), which patent application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to surgical methods and apparatus in general, and more particularly to surgical methods and apparatus for performing open wedge osteotomies of the knee. 
       BACKGROUND OF THE INVENTION 
       [0003]    Osteotomies of the knee are an important technique for treating knee osteoarthritis. In essence, knee osteotomies adjust the geometry of the knee joint so as to transfer weight bearing load from arthritic portions of the joint to the relatively unaffected portions of the joint. 
         [0004]    Knee osteotomies are also an important technique for addressing abnormal knee geometries, e.g., due to birth defect, injury, etc. 
         [0005]    Most knee osteotomies are designed to modify the geometry of the tibia, so as to adjust the manner in which the load is transferred across the knee joint. 
         [0006]    There are essentially two ways in which to adjust the orientation of the tibia: (i) the closed wedge technique; and (ii) the open wedge technique. 
         [0007]    With the closed wedge technique, a wedge of bone is removed from the upper portion of the tibia, and then the tibia manipulated so as to close the resulting gap, whereby to reorient the lower portion of the tibia relative to the tibial plateau and hence adjust the manner in which load is transferred from the femur to the tibia. 
         [0008]    With the open wedge technique, a cut is made into the upper portion of the tibia, the tibia is manipulated so as to open a wedge-like opening in the bone, and then the bone is secured in this position (e.g., by screwing metal plates to the bone or by inserting a wedge-shaped implant into the opening in the bone), whereby to reorient the lower portion of the tibia relative to the tibial plateau and hence adjust the manner in which load is transferred from the femur to the tibia. 
         [0009]    As noted above, it is also possible to modify the geometry of the femur, so as to adjust the manner in which load is transferred across the knee joint. 
         [0010]    The present invention is directed to open wedge osteotomies of the femur. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention comprises a novel method and apparatus for performing an open wedge, low femoral osteotomy. More particularly, the present invention comprises the provision and use of a novel method and apparatus for forming an appropriate osteotomy cut into the lower portion of the femur, manipulating the femur so as to open an appropriate wedge-like opening in the femur, and then inserting an appropriate wedge-shaped implant into the wedge-like opening in the femur, so as to stabilize the femur with the desired orientation, whereby to reorient the lower portion of the femur relative to the tibia and hence adjust the manner in which load is transferred from the femur to the tibia. 
         [0012]    In one form of the present invention, there is provided apparatus for performing an open wedge, low femoral osteotomy, the apparatus comprising: 
         [0013]    an osteotomy guide, a hinge pin and an osteotomy implant;
       the osteotomy guide comprising:
           anterior and posterior tissue shields, wherein the distal ends of the anterior and posterior tissue shields comprise openings for receiving the hinge pin and defining the hinge pin axis, and further wherein the proximal ends of the anterior and posterior tissue shields comprise profiles configured to enable fluoroscopic alignment of the hinge pin axis parallel to the saggital plane of the patient;   a cutting guide and a drill guide connected to the proximal ends of the anterior and posterior tissue shields, wherein the cutting guide comprises a cutting slot for defining a cutting plane extending parallel to, and through, the hinge axis, and further wherein the drill guide comprises a drill guide hole for forming a guide hole in the femur, wherein the guide hole extends substantially perpendicular to the cutting plane;   
               
 
         [0017]    the hinge pin comprising an elongated body sized to be received in the openings in the distal ends of the anterior and posterior tissue shields; and 
         [0018]    an osteotomy implant for positioning in a wedge-shaped opening formed in the femur about the cutting plane and for receiving a screw extending through the guide hole. 
         [0019]    In another form of the invention, there is provided a method for performing an open wedge, low femoral osteotomy, the method comprising: 
         [0020]    deploying a hinge pin within the femur so that the hinge pin extends anterior-to-posterior, parallel to the sagittal plane of the patient; 
         [0021]    forming an osteotomy cut through the femur, wherein the osteotomy cut extends parallel to, substantially contacts, the hinge pin; 
         [0022]    opening the femur along the osteotomy cut so as to form a wedge-shaped opening in the femur; 
         [0023]    positioning an osteotomy implant within the wedge-shaped opening in the femur. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0024]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0025]      FIGS. 1 and 2  are schematic views showing the tibia and femur of a knee joint; 
           [0026]      FIG. 3  is a schematic view of an osteotomy guide which may be used to perform an open-wedge, low femoral osteotomy in accordance with the present invention; and 
           [0027]      FIGS. 4-24  are schematic views illustrating an open wedge, low femoral osteotomy performed in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]    Looking first at  FIGS. 1 and 2 , there is shown a knee joint  5  upon which an open wedge, low femoral osteotomy is to be performed. Knee joint  5  generally comprises a tibia  10  and a femur  15 . 
         [0029]    In accordance with the present invention, the open wedge, low femoral osteotomy is preferably performed using the osteotomy guide  100  shown in  FIG. 3 . Osteotomy guide  100  generally comprises an anterior tissue shield  105 A having a hole  110 A formed on one end thereof and a wishbone segment  115 A formed on the other end thereof; a posterior tissue shield  105 P having a hole  110 P formed on one end thereof and a wishbone segment  115 P formed on the other end thereof; a cutting guide  120  having a cutting slot  125  formed therein and a drill guide  130  having a pair of drill guide holes  135 A and  135 P formed therein, with cutting guide  120  and drill guide  130  being formed so as to mount to wishbone segments  115 A,  115 P of tissue shields  105 A,  105 P; a guide bushing  137  for mounting to anterior tissue shield  105 A; and a hinge pin  140 . 
         [0030]    Looking next at  FIGS. 4-24 , the open wedge, low femoral osteotomy is preferably performed as follows. 
         [0031]    (1) First, using a fluoroscope set up in Anterior-Posterior (AP) view, the desired location of the osteotomy hinge is marked on the skin (not shown). 
         [0032]    (2) Next, a lateral incision (also not shown) is made in the skin and then anterior tissue shield  105 A and posterior tissue shield  105 P are inserted, anteriorly and posteriorly, respectively, alongside femur  15 . See  FIGS. 4 and 5 . 
         [0033]    (3) Next, cutting guide  120  and drill guide  130  are snapped into wishbone segments  115 A,  115 P of tissue shields  105 A,  105 P, so that tissue shields  105 A,  105 P, cutting guide  120  and drill guide  130  assume the configuration shown in  FIG. 3 . 
         [0034]    (4) Then an incision is made at the boney hinge tissue mark and guide bushing  137  is mounted into hole  110 A in anterior tissue shield  105 A. See  FIGS. 4 and 5 . 
         [0035]    (5) Next, the desired location of the hinge pin boney entrance is marked by drilling approximately 5 mm into the bone with a hinge pin drill D. See  FIGS. 6  and  7 . This forms a pivot point for hinge pin drill D in the following alignment step (Step  6 ) which will determine the orientation of the hinge pin hole. 
         [0036]    (6) During the alignment step, the surgeon holds hinge pin drill D and an alignment handle (not shown) connected to osteotomy guide  100 , pushing a reference edge on cutting guide  120  against the lateral aspect of the femur. The surgeon&#39;s other hand holds hinge pin drill D in the boney pivot created in the preceding step (Step  5 ). Looking in the lateral fluoroscope view, the hinge pin axis is made parallel with the patient&#39;s sagittal plane by aligning the arms of the two wishbones  115 A,  115 P in the fluoroscope view. 
         [0037]    (7) When the aforementioned alignment is achieved, a hinge pin hole  143  ( FIGS. 9 and 14 ) is drilled into the femur, using hinge pin drill D. On account of the foregoing procedure, the hinge pin hole will extend anterior-to-posterior, parallel with the patient&#39;s sagittal plane. 
         [0038]    (8) Next, hinge pin  140  is inserted into hinge pin hole  143 , passing through guide bushing  137 , through anterior tissue shield  105 A and threading into hole  110 P in posterior tissue shield  105 P. See  FIGS. 8 and 9 . A collet nut (not shown) may be used to lock guide bushing  137  and hinge pin  140  together. 
         [0039]    (9) A reference edge of drill guide  130  is pushed up against the lateral aspect of the femur (see  FIG. 10 ) and then two guide holes  145 A,  145 P are drilled through drill guide holes  135 A,  135 P, respectively. Guide holes  145 A,  145 P are drilled up to the osteotomy plane. See  FIG. 11 . Note that only drill guide hole  135 A, and only guide hole  145 A, are shown in  FIG. 11  due to the angle of view. 
         [0040]    (10) Next, two bolts  150 A,  150 P, equipped with self-cutting threads (to form threads in the femur, to be used later by compression screws, as will hereinafter be discussed) are inserted into the drill guide holes  135 A,  135 P and into guide holes  145 A,  145 P, respectively, tightening the instrumentation against the bone. See  FIG. 12 . 
         [0041]    (11) Then an oscillating saw blade (not shown) is advanced through cutting slot  125  in cutting guide  120  and into the femur. Cutting slot  125  guides the oscillating saw blade so as to restrict the osteotomy cut  155  ( FIG. 13 ) to the zone within the “safety cage” formed by anterior and posterior tissue shields  105 A,  105 P and hinge pin  140 . As a result, the delicate vascular and neurological tissues surrounding the knee joint are fully protected during formation of osteotomy cut  155 . 
         [0042]    (12) At this point, bolts  150 A,  150 P are withdrawn from the femur, hinge pin  140  is withdrawn from the femur, and the remainder of osteotomy guide  5  is removed from the surgical site, leaving osteotomy cut  155  extending from the surface of the femur to hinge pin hole  143 , with guide holes  145 A,  145 P extending to osteotomy cut  155 . See  FIG. 14 . 
         [0043]    (13) Next, the femur is opened along osteotomy cut  155 , so as to create a wedge-like opening  160  in the lower end of the femur. See  FIGS. 15 and 16 . 
         [0044]    (14) Then an appropriate wedge-shaped implant is disposed in wedge-like opening  160  so as to maintain the femur in its proper disposition during healing. Preferably the wedge-shaped implant  200  shown in  FIGS. 17 and 18  is used. Wedge-shaped implant  200  generally comprises a wedge-shaped body  205  having a distal end  210  and a proximal end  215 , with an upper surface  220  and a lower surface  225 . A pair of holes  230 A,  230 P extend through body  205 , from lower surface  225  to upper surface  220 . As seen in  FIGS. 19 and 20 , wedge-shaped implant  200  is positioned in wedge-shaped opening  160  so that the implant&#39;s upper surface  220  engages the upper portion of the femur and the implant&#39;s lower surface  225  engages the lower portion of the femur, and so that implant holes  230 A,  230 P are aligned with guide holes  145 A,  145 P, respectively. 
         [0045]    (15) Next, a pair of extension holes  165 A,  165 P are drilled into the femur on the far side of the implant, with extension hole  165 A being aligned with implant hole  230 A and guide hole  145 A, and with extension hole  165 P being aligned with implant hole  230 P and guide hole  145 P. See  FIGS. 21 and 22 . Note that only extension hole  165 A, and only guide hole  154 A, are shown in  FIG. 21  due to the angle of view. 
         [0046]    (16) Finally, wedge-shaped implant  200  is secured in position by passing a compression screw  235 A through guide hole  145 A, implant hole  230 A and extension hole  165 A, and by passing a compression screw  235 P through guide hole  145 P, implant hole  230 P and extension hole  165 P. See  FIGS. 23 and 24 . Note that only compression screw  235 A is shown in  FIG. 23  due to the angle of view. Significantly, the compression screws engage bone on both sides of the osteotomy cut and, as the compression screws  235 A,  235 B are tightened, the compression screws draw the bone on both sides of the osteotomy closed, against the wedge-shaped implant. 
         [0047]    Furthermore, the closely perpendicular relationship between the osteotomy plane and the compression screws allows for fixation to be maintained with screws in tension rather than in bending. The threads on either end of each compression screw also distribute shear load on the bone more evenly than a conventional locking plate-and-screw fixation that bears load on bone perpendicular to the axes of the screws. Fixation may also be enhanced by incorporating a small washer or plate of metal or plastic between each compression screw head and bone. The washer or plate may be self aligning to accommodate the bone geometry. 
         [0048]    The controlled position and orientation of the compression screws help to locate the implant within the osteotomy. The compression screw axes are controlled through the use of osteotomy guide  100 , which interfaces with the instrumentation which is aligned to anatomical features of the distal femur. 
       Modifications 
       [0049]    It will be understood that many changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art without departing from the principles and scope of the present invention.