Abstract:
Method and apparatus for performing osteotomies using an osteotomy plate having locking washers. A bone is resected to form an opening that is held open by a tooth projecting from a bone plate. The bone plate is secured to the outer surface of the bone with self-tapping bone plate screws. Screws are inserted through holes into the bone plate which contain washers that are rotatable in the holes. The outwardly-tapered head of the screw spreads the split sleeve washer as it advances and locks the washer. Slots in the split-sleeve washer can be engaged by a driver in order to adjust the bone plate so that lays properly against the resected bone.

Description:
[0001]     This application claims the benefit of U.S. Provisional Application No. 60/536,706 filed Jan. 16, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to osteotomies, and more specifically to methods and apparatus for performing osteotomies using an osteotomy plate having locking washers.  
       BACKGROUND OF THE INVENTION  
       [0003]     Osteotomies are procedures that surgically reorient the alignment of a deformed bone. The aim of an osteotomy is to realign the bearing surfaces of a joint to allow normal areas to articulate, moving abnormal areas away from the load-bearing axis. In the leg, a femoral or tibial osteotomy may be indicated. High tibial osteotomies (HTO), for example, are indicated by early, medial joint-space narrowing, by early arthritis in patients who have had previous medial meniscectomy, or following rupture of the anterior cruciate ligament (ACL) in patients with pre-existing varus deformity, for example.  
         [0004]     There are two schools of thought regarding osteotomy methods: the closing wedge method, and the opening wedge method. In the closing wedge method, removal of a bone wedge creates an angled gap in the bone. Part of the bone is left as a hinge at the apex of the angle. The hinge allows the gap to narrow, and the bone material on either side of the closed gap joins together.  
         [0005]     In the opening wedge method, a cut is made across the bone. Part of the bone is left as a hinge, as in the closing wedge method. In contrast to the closing wedge method, however, the hinge allows the cut gap to open. The open wedge is filled with graft material.  
         [0006]     The two methods are performed on opposite sides of the bone to give equivalent results. For example, when a given deformity would be corrected by performing the opening-wedge procedure on the medial side of a bone, an equivalent closing-wedge correction would be performed laterally.  
         [0007]     The closing wedge method is the current standard, although several disadvantages are associated with the technique. The most significant disadvantages of the closing wedge method are: (i) disruption of the tibial-femoral joint; (ii) possible damage to neurovascular structures; and, (iii) disruption of the medial cortex, resulting in instability and nonunion between the upper and lower bone because of possible soft tissue interference. It is also difficult to compute the correct amount of bone to remove, and, therefore, several extra cuts may be required.  
         [0008]     The opening wedge technique avoids or limits many of the disadvantages associated with the closing wedge method. Additionally, the medial, open-wedge HTO has the following advantages over the closed, lateral-wedge HTO: (i) speed; (ii) simplicity; (iii) ability to quickly change angle at any time during the procedure; and (iv) no fibular osteotomy is required.  
         [0009]     Apparatus and methods for performing opening wedge osteotomies are disclosed in U.S. Pat. Nos. 5,620,448 and 5,749,875 issued to Puddu and assigned to Arthrex, Inc., the disclosures of which are incorporated herein by reference, particularly as they relate to operative method and insertion tools. A similar system is disclosed in U.S. patent application Ser. No. 09/872,100, filed Jun. 1, 2001, the disclosure of which is incorporated herein by reference, particularly as it relates to grafts and graft materials developed for insertion into osteotomy openings. The present invention represents improvements on prior art systems.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention provides a system for performing opening wedge osteotomies in which a bone is resected to form an opening on one side governed by a bony hinge on the other side. The system includes a bone plate having a projection in the form of a tooth extending from the plate. The tooth on the bone plate is provided to maintain the bone opening. The edges of bone at the bone opening engage opposed edges of the bone plate tooth to keep the resected bone propped open. The bone plate extends outwardly on either side of the tooth for engaging the outer surface of the bone. Holes through the extended portions of the bone plate receive cancerous or cortical plate screws for securing the bone plate in place against the bone. The bone plate preferably is formed of a metal, such as titanium alloy.  
         [0011]     The holes in the bone plate are provided with internally-threaded, split-sleeve washers that are pivotable or rotatable within the holes. The plate screws are installed through the threaded openings in the split-sleeve washers. The plate screws feature an outwardly-tapered head that spreads the split sleeve washers with screw advancement. The plate screw heads are threaded to complement the internal threads of the split sleeve washers. A bone screw portion of each screw is self-tapping and threaded appropriately to provide optimal purchase in bone.  
         [0012]     An opening wedge osteotomy is performed by resecting bone laterally to form an opening governed by a hinge of cortical bone. The resected bone is wedged apart, and the bone plate is installed such that the bone plate tooth maintains the bone opening. The plate screws are installed to secure the bone plate in position, the rotatable washers allowing the screws to be oriented at an angle other than perpendicular to the bone plate while allowing a finished position with the screw head flush with an outer surface of the bone plate. During advancement, the outwardly tapered head of the plate screws urges the split-sleeve washers to spread radially and thereby exhibit a locking capability by way of frictional interference between the radially outer surface of the washer and an inner wall of the bone plate. Slots formed in the outward face of the split-sleeve washers can be engaged by a driver to turn the washer in the event that adjustments are required.  
         [0013]     Other features and advantages of the present invention will become apparent from the following description of exemplary embodiments of the invention with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  illustrates a plan view of a tibial opening wedge osteotomy plate according to the present invention;  
         [0015]      FIG. 2  illustrates an elevation view of the tibial opening wedge osteotomy plate of  FIG. 1  taken along lines A-A;  
         [0016]      FIG. 3  illustrates a split sleeve locking washer according to the present invention;  
         [0017]      FIG. 4  is a perspective illustration of the bone plate of  FIG. 1  with a mal-rotated washer according to the present invention;  
         [0018]      FIG. 5  illustrates a plan view of the anterior/posterior sloped opening wedge osteotomy plate according to the present invention;  
         [0019]      FIG. 6  illustrates an elevation view of the anterior/posterior sloped opening wedge osteotomy plate of  FIG. 5  taken along lines B-B;  
         [0020]      FIG. 7  illustrates a plan view of a femoral opening wedge osteotomy plate according to the present invention;  
         [0021]      FIG. 8  illustrates an elevation view of the femoral opening wedge osteotomy plate of  FIG. 7  taken along lines C-C;  
         [0022]      FIG. 9  illustrates a cancerous plate screw according to the present invention;  
         [0023]      FIG. 10  illustrates the cross-section of the cancerous screw of  FIG. 9  taken along lines D-D;  
         [0024]      FIG. 11  illustrates the cross-section of the notched tip of the cancerous screw of  FIG. 9  taken along line E-E;  
         [0025]      FIG. 12  illustrates a top view of the head of the cancellous plate screw of  FIG. 9 ;  
         [0026]      FIG. 13  illustrates a cortical plate screw according to the present invention;  
         [0027]      FIG. 14  illustrates the cross-section of the cortical screw of  FIG. 13  taken along lines F-F;  
         [0028]      FIG. 15  illustrates the cross-section of the notched tip of the cortical plate screw of  FIG. 13  taken along lines G-G;  
         [0029]      FIG. 16  illustrates a top view of the head of the cortical plate screw of  FIG. 13 ;  
         [0030]      FIG. 17  is a schematic representation of the resecting and measuring step in an osteotomy procedure using a tibial opening wedge osteotomy plate, such as that of  FIGS. 1 and 2 ;  
         [0031]      FIG. 18  is a schematic representation of the locking and drilling steps in the osteotomy procedure of  FIG. 17 ;  
         [0032]      FIG. 19  is a schematic representation of the drilling and screw measuring steps in the osteotomy procedure of  FIG. 17 ;  
         [0033]      FIG. 20  is a schematic representation of a screw insertion step in the osteotomy procedure of  FIG. 17 ;  
         [0034]      FIG. 21  is a schematic representation of positioning and locking a bone screw and washer in the osteotomy procedure of  FIG. 17 ;  
         [0035]      FIG. 22  is a schematic representation of inserting the locking guide into the washer slots in order to rotate the washer in the osteotomy procedure of  FIG. 17 ;  
         [0036]      FIG. 23  is a schematic representation of loosening and tightening of a screw in the osteotomy procedure of  FIG. 17 ; and  
         [0037]      FIG. 24  is a schematic representation of a completed installation of a tibial bone plate according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0038]     The present invention provides techniques and apparatus for open wedge osteotomies. For simplicity, the methods described herein are with reference to, but not limited to, one type of osteotomy, the tibial opening wedge osteotomy.  
         [0039]     Referring now to  FIGS. 1-2 , a tibial opening wedge osteotomy bone plate  10  includes a plate  12  having a projecting tooth  14 . Plate  12  has extensions  16 ,  18  on either side of tooth  14  with holes  20  formed in the extensions. Each of the holes  20  is defined by a radially-curved internal wall  22  formed in the plate extensions  16 ,  18 . A threaded, split-sleeve washer  50  is fitted into each of the holes  20  in the plate  10 . The washers  50  rotate freely in any direction within the hole  20 , but are not removable from the hole  20  by finger pressure.  
         [0040]     Bone plate  10  is formed of a metal, preferably titanium alloy. Preferably, the grain of the metal is oriented parallel with the longer dimension of the bone plate. A threaded central opening  24  is provided to receive an application bar (not shown) to facilitate handling of the bone plate  10 .  
         [0041]     Referring to  FIG. 3 , a visualization mark, such as mark  56 , is provided on each washer  50 . Each washer  50  includes slots  52  formed in one side by toothed projections, and an opposing smooth side  54  ( FIG. 4 ).  FIG. 4  shows three of the washers  14  oriented with the slotted side facing up, and one washer mal-rotated so that the slotted side faces down, such that the smooth side  54  is visible in the drawing. The slots are configured to be engaged by a locking guide  138 , described further below.  
         [0042]     Bone plates of the present invention can be provided in various configurations depending on the indicated osteotomy to be performed.  FIGS. 5-6  illustrate an exemplary embodiment of a tibial anterior/posterior (A/P) sloped osteotomy plate  70 .  FIGS. 6-7  illustrate an exemplary embodiment of a femoral opening wedge osteotomy plate  60 . Each plate features the movable washers  50  described above in connection with  FIGS. 1-3 .  
         [0043]     Referring to  FIGS. 9-16 , plate screws are used to secure a selected bone plate  10 ,  70 ,  80 .  FIGS. 9-12  illustrates a hex-drive cancellous plate screw  100 . Plate screw  100  features a screw body  102  having a threaded bone portion  104  and a threaded screw head  106 . The screw body  102  supports a cancellous bone thread  108  that extends over both the threaded bone portion  104 , and a plate thread  110  that extends over the threaded screw head  106 . The screw body  102  and cancellous bone thread  108  have substantially uniform outer diameters over the threaded bone portion  94 . In the transition between the threaded bone portion  104  and threaded screw head  106 , the outer diameter of plate thread  110  is reduced with respect to that of cancellous bone thread  108 , and then tapers outwardly toward the head end of the plate screw  100 . The reduced outer diameter of plate thread  110  facilitates initial engagement with the internal threads of washers  50  ( FIGS. 1-3 ), followed by spreading of washers  50  by the outwardly tapering threaded screw head  106 , as described further below. The threaded bone portion  104  features about nine thread flights  108 , preferably at a thread pitch of about 0.108, suitable for use in cancellous bone. The threaded screw head  106  features about two thicker thread flights, preferably having a pitch of about 0.133, to complement the internal threads on washers  50 . Referring to  FIG. 11 , preferably, a notch  112  is formed near the tip of screw  100  to facilitate self-tapping installation of screw  90  into bone. Referring to  FIG. 12 , a visual mark, such as black mark  114 , is provided on the head of each screw  100 . Bone screw  100  is made of metal, preferably titanium alloy.  
         [0044]     Referring to  FIGS. 13-16 , a hex-drive cortical plate screw  200  features a screw body  202  having a threaded bone portion  204  and a threaded screw head  206 . The screw body  202  supports a cortical bone thread  208  that extends over the threaded bone portion  204 , and a plate thread  210  that extends over the threaded screw head  206 . The screw body  202  and cortical bone thread  208  have substantially uniform outer diameters over the threaded bone portion  204 . In the transition between the threaded bone portion  204  and threaded screw head  206 , the outer diameters of screw body  202  and plate thread  210  taper outwardly toward the head end of the plate screw  200  to facilitate initial engagement with the internal threads of washers  50  ( FIGS. 1-3 ), followed by spreading of washers  50 , as described further below The threaded bone portion  204  features about fifteen thread flights, preferably at a thread pitch of about 0.069, suitable for use in cortical bone. The threaded screw head  206  features about two thicker thread fights, preferably having a pitch of about 0.133, to complement the internal threads on washers  50 . Referring to  FIG. 15 , preferably, a notch  212  is formed near the tip of screw  200  to facilitate self-tapping installation of screw  200  into bone. Referring to  FIG. 16 , a visual mark, such as black mark  214 , is provided on the head of each screw  200 . Bone screw  200  is made of metal, preferably titanium alloy.  
         [0045]     An exemplary method of using the opening wedge osteotomy plate  10 ,  70 ,  80  and the bone plate screws  100 ,  200  is described below with reference to  FIGS. 17-25 , which illustrate a schematic view of a tibia in which an open wedge osteotomy is performed according to the present invention. In the following embodiment, an opening wedge tibial osteotomy is performed (shown completed in  FIG. 25 ) with a selected bone plate  306  in a resecting tibia  302 .  
         [0046]     Referring to  FIG. 17 , the opening wedge tibial osteotomy begins by resecting tibia  300  so as to leave a bony hinge  302 . A plate trial bar  304  is utilized to estimate the size of the bone plate that is needed for the desired correction  320 .  FIG. 19 , for example, shows a 7.5 mm correction.  
         [0047]     Referring to  FIG. 18 , the selected bone plate  306  (such as tibial osteotomy plate  10 ) having a projecting tooth  14  size equal to that measured by the plate trial bar  304  is positioned into the bone correction  320 , ensuring optimum bone-to-plate contact with tooth  14 . Prior to insertion, all of the washers  50  inside the plate are inspected and the washer teeth  52  are visualized to be on the side of the plate opposite the tooth  14 . A drill guide  308  is inserted into a locking guide  310 , and then into the opening in a washer  50  in plate  306 . The locking guide  310  features complementary teeth which engage slots  52  on washers  50 .  
         [0048]     Referring to  FIG. 19 , a drill  312  is inserted under x-ray in standard fashion and drilled to (but not through) the lateral tibial cortex. The length of a screw may be determined by viewing laser lines formed on the back end of the drill  140 . In  FIG. 19 , for example, a screw having a length of 55 mm is indicated.  
         [0049]     Referring to  FIG. 20 , the drill guide  308  is removed while the position of the locking guide  310  is maintained in the slots  52  of washer  50 . A plate screw  314  (such as cancerous plate screw  100  or cortical plate screw  200 ) with the appropriate diameter and length (for example, as per  FIG. 19 , a length of 55 mm is indicated) is installed through the locking guide  310  and into the bone using a driver  316 .  
         [0050]     Referring to  FIG. 21 , just as the screw head threads contact the washer  50 , the mark  56  on the washer  50  is positioned just clockwise to the black mark  318  on the screw head. Advantageously, the washer  50  can be rotated, if necessary, using the locking guide  310 . Positioning the black marks in this way will ensure that the threads of the screw thread properly into the washer. The screw is advanced until it is tight and flush with the washer. As the screw  314  is advanced, the outward taper of the screw head spreads the split-sleeve washer  50 , causing the assembly of the screw  314  and the washer  50  to become locked from rotation due to the frictional interference between an outer surface of the washer  50  and an inner surface of the bone plate  304  where the washer is inserted. The process is repeated for each of the screws until the bone plate is secured to the bone.  
         [0051]     Referring to  FIGS. 22 and 23 , if the plate  306  is slightly proud from the cortical surface of the bone, the screws  314  can be unscrewed to slightly loosen the screw. In  FIG. 22 , the locking guide  310  is inserted into the slots  52  on the washer  50 , and the washer is rotated clockwise to seat the plate  306  against the bone.  FIG. 23  illustrates that the screw  314  is then advanced with the driver  316  until it is tight and flush with the washer  50 . A completed installation of tibial bone plate  306  is illustrated in  FIG. 24 .  
         [0052]     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.