Patent Publication Number: US-2013245695-A1

Title: Veterinary plate

Description:
PRIORITY CLAIM 
     The present application claims priority to U.S. Provisional Appln. Ser. No. 61/610,707 entitled “Veterinary Plate” filed on Mar. 14, 2012, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND INFORMATION 
     Triple Pelvic Osteotomy (TPO) is typically performed on immature canines to treat coxofemoral joint subluxation, changing the orientation of the acetabulum to allow improved congruity and coverage of the femoral head to increase coxofemoral joint stability. Increasing this stability of the joint helps to maintain normal joint mechanics and minimizes the subsequent development of osteoarthritis. The TPO procedure is performed by first performing an osteotomy of the pubis with a ventral approach to the hip. A second osteotomy of the ischium is then performed with a caudal approach directly caudal to the ischium, followed by a third osteotomy of the ilium with a craniolateral approach to the hip and ilial shaft. Once all three osteotomies have been made, the acetabulum is rotated to improve the congruity of the joint and ensure adequate capture the femoral head. A TPO plate is used to secure the rotation. The TPO procedure is subject to several potential complications, including sacral screw loosening, pelvic narrowing and excessive head coverage. In another procedure known as a Double Pelvic Osteotomy (DPO), only the pubic and ilial osteotomies are performed, without performing the ischial osteotomy, thus relying on the flexibility of the pubic symphysis and the ischiatic table. The DPO technique reduces issues of pelvic narrowing post-operation due to the continued integrity of the ischium, which maintains the pelvic width and prevents ventral displacement of the pelvic floor as seen with bilateral DPO. More importantly, maintaining ischial integrity increases the overall stability of the fixation, which results in better patient comfort and function early postoperatively. The DPO technique is more difficult to perform than the TPO because the acetabulum is significantly more difficult to rotate with the ischium intact. Furthermore, the DPO procedure also is subject to the additional complication of ilial screw pullout because of the elastic memory of the pelvis (and intact ischium) of the rotated acetabular segment. Regardless of the method utilized to rotate the acetabular segment, the surgeon must perform an accurate rotation and be able to secure this bone segment rigidly, which requires the appropriate implant. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a bone fixation device comprising a plate body having a first body portion lying in a first plane, a second body portion lying in a second plane and an interface body portion lying in a third plane. The first plane is angled relative to the second plane an angle fixed relative to the first plane and the third plane is angled relative to the first and second planes. A longitudinal axis of the first body portion is angled with respect to a longitudinal axis of the second body portion. The first body portion has first and second openings extending therethrough and the second body portion has third and fourth openings extending therethrough. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a first perspective view of a exemplary bone plate according to the present invention implanted in an ilial shaft portion; 
         FIG. 2  shows a second perspective view of the bone plate of  FIG. 1 ; 
         FIG. 3  shows a third perspective view of the bone plate of  FIG. 1 ; 
         FIG. 4  shows a first perspective view of a bone plate according to a first alternate embodiment of the invention; 
         FIG. 5  shows a second perspective view of the bone plate of  FIG. 4 ; 
         FIG. 6  shows a first view of cranial screw trajectories of the bone plate of  FIG. 1 ; 
         FIG. 7  shows a second view of cranial screw trajectories of the bone plate of  FIG. 1 ; 
         FIG. 8  shows a first view of caudal screw trajectories of the bone plate of  FIG. 1 ; 
         FIG. 9  shows a second view of caudal screw trajectories of the bone plate of  FIG. 1 ; 
         FIG. 10  shows another view of the screw trajectories of the bone plate of  FIG. 1   
         FIG. 11  shows a perspective view of a bone plate according to a second alternate embodiment of the invention; 
         FIG. 12  shows a perspective view of a bone plate according to a third alternate embodiment of the invention; 
         FIG. 13  shows a first perspective view of a bone plate according to a fourth alternate embodiment of the invention; 
         FIG. 14  shows a second perspective view of the bone plate of  FIG. 13 ; 
         FIG. 15  shows a first perspective view of a bone plate according to a fifth alternate embodiment of the invention; and 
         FIG. 16  shows a second perspective view of the bone plate of  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates generally to devices and methods for the stabilization of joints. Specifically, the present invention relates to methods and devices for changing an orientation of a shallow acetabulum to allow better coverage of the head of a femur of a cat or dog in connection with a TPO procedure. However, the exemplary bone plate according to the invention may also be used in conjunction with a DPO procedure. Specifically, the exemplary bone plate according to the invention may be used in either a DPO or a TPO procedure, with a surgeon selecting the procedure to conform to the requirements of the animal to be treated. The exemplary bone plate according to the invention has been designed to provide a stable and reliable fixation for both TPO and DPO procedures. The exemplary system and method according to the invention are configured increase a strength of the sacrum after implantation thereover by increasing a purchase of bone screws within the sacrum. Additionally, since the exemplary device according to the invention is configured for use with locking screws, the possibility of loosening of screws after implantation is minimized. As would be understood by those skilled in the art, the exemplary system and method disclosed herein may be employed in conjunction with bone fixation procedures for any animal by modifying the dimensions and shape of the apparatus to suit the particular anatomy. It is noted that directional terms assigned to components of the device of the present invention are labeled in accordance with a position of the device when in an operative configuration, as shown in  FIG. 10  and described in greater detail below. However, those skilled in the art will understand that these terms are used to describe an exemplary procedure and are not intended to limit the invention. That is, the device may be oriented in other directions if so desired—e.g., when employed in different animals—as would be understood by those skilled in the art. 
     As shown in  FIGS. 1-10 , a device  100  according to an exemplary embodiment of the invention comprises a substantially elongated plate body  102  extending from a first end  104  to a second end  106  along a longitudinal axis  107 . The plate body  102  comprises a first body portion  108  and a second body portion  110  axially offset from each other, as will be described in greater detail below. The plate body  102  is formed of a biocompatible material such as a metal or metal alloy (e.g., Stainless Steel, etc.) or a polymer (e.g., “PEEK”, etc.) having a rigidity selected to provide a desired degree of stability to the performed osteotomies when implanted, as those skilled in the art will understand. The first body portion  108  has a substantially rectangular cross-section with a caudal relief  112  formed adjacent the first end  104 . The caudal relief  112  defines an arc-shaped cutout from the first body portion  108  configured to avoid interfering with the tuberosity of the rectus femoris muscle in an operative configuration, as those skilled in the art will understand. The first body portion  108  is angled at an angle of α 1  relative to the longitudinal axis  107  of the second body portion  110  of the plate body  102 . In an exemplary embodiment, the angle α 1  is approximately 15°, although any other angular offset may be used as dictated by the anatomy without deviating from the scope of the invention. As those skilled in the art will understand, the angle α 1  is selected to provide a better fit of the first body portion  108  against the bone—i.e., to conform to a shape and dimension of the bone after it has been rotated to a corrected alignment in accordance with a DPO procedure. The first body portion  108  also comprises a plurality of bone fixation holes  114 ,  116  extending therethrough and configured to permit insertion of bone fixation screws  130  therethrough. The bone fixation holes  114 ,  116  may be threaded or unthreaded as those skilled in the art will understand. In one embodiment, the first body portion  108  comprises three bone fixation holes  114  disposed adjacent a dorsal wall  118  thereof. Each of the fixation holes  114  has a substantially conical shape and includes a chamfer relief  119  configured to seat a head of the bone fixation element  130  inserted therethrough. However, those skilled in the art will understand that any or all of the holes  114  may have any other desired configuration. Each of the fixation holes  114  extends through the first body portion  108  at an angle selected to ensure that a bone fixation element  130  inserted therethrough enters a target location relative of the bone, as will be described in greater detail with respect to  FIGS. 6-10 . Specifically, the fixation holes  114 ,  116  may be angled so that bone fixation screws  130  inserted therethrough advance into portions of bone having increased density, thereby increasing a holding strength of the plate body  102  with the bone, as those skilled in the art will understand. The fixation hole  116  of this embodiment is a combination hole configured to permit a physician to select a position and angle of the bone fixation element  130  inserted therethrough, as those skilled in the art will understand. It is noted that although the first body portion  108  is depicted with three fixation holes  114  and one combination hole  116 , any number and combination of the above may be employed without deviating from the scope of the invention. Furthermore, the fixation holes  114 ,  116  may be positioned in any arrangement over the first body portion  108  without deviating from the scope of the invention. 
     The second body portion  110  extends substantially parallel to the longitudinal axis of the plate body  102  and comprises a plurality of bone fixation holes  120 ,  122  extending therethrough. Specifically, the second body portion  110  may comprise three fixation holes  120  and one combination hole  122 . Each of the fixation holes  120  may extend through the second body portion  110  at a predetermined angle selected to permit the bone fixation element  130  inserted therethrough to be positioned at a desired location relative to the bone. Although the second body portion  110  is depicted with three fixation holes  120  and one combination hole  122 , any number and combination of the above may be employed without deviating from the scope of the invention. Furthermore, the fixation holes  120 ,  122  may be positioned in any arrangement over the second body portion  110  without deviating from the scope of the invention. As those skilled in the art will understand, the use of combination fixation holes  116 ,  122  on each of the first and second body portions  108 ,  110  allows for compression of the bone regardless of whether a TPO or DPO technique is used. Specifically, by placing a combination hole in each of the first and second body portions  108 ,  110 , a veterinarian or other user may secure either of the first or second body portions  108 ,  110  to the bone in a first step of a bone fixation procedure, as will be described in greater detail later on. The bone fixation holes  114 ,  116 ,  120 ,  122  according to the invention may be configured and dimensioned to receive locking or cortical screws (e.g, 3.5 mm screws, 2.7 mm. screws, etc.). In an exemplary embodiment, each of the first and second body portions  108 ,  110  comprises four fixation holes extending therethrough. 
     As shown in  FIG. 3 , the second body portion  110  resides in a plane axially offset from a plane housing the first body portion  108  by an angle α 3 , as will be described in greater detail later on. Furthermore, the planes housing the first and second body portions  108 ,  110  extend along longitudinal axes angled relative to one another at an angle selected to conform to the anatomy of the bone. Specifically, the planes of the first and second body portions  108 ,  110  are oriented to permit the plate  102  to be seated substantially flush against the bone in an operative configuration. 
     The first body portion  108  is connected to the second body portion  110  by an interface portion  109  lying in a plane substantially perpendicular to the plane housing the second body portion  110 . The interface portion  109  extends at an angle α 2  relative to an orthogonal axis  111  of the plate body  102 . In an exemplary embodiment, the angle α 2  is approximately 5°. However, any other measurement for the angle α 2  may be used without deviating from the scope of the invention. In one example, the angle α 2  may be in the range of approximately 0-15°. In an exemplary embodiment, the angle α 3  corresponds to a desired angle of rotation required to stabilize a hip joint of the animal being treated. As shown in  FIG. 3 , a lateral wall  113  of the interface portion  109  is angled at an angle of α 3  relative to the plane housing the second body portion  110 . In an exemplary embodiment, the angle α 3  may be one of approximately 20°, 25° and 30° although any angle in the range of 15-40° may be used without deviating from the scope of the invention. 
     The first and second body portions  108 ,  110  comprise Kirschner-wire (“K-wire”) holes  124 ,  126 , respectively, positioned substantially centrally on the corresponding one of the first and second body portions  108 ,  110  to aid in placement thereof over the bone. Alternatively, the K-wire holes  124 ,  126  may be positioned anywhere else on the plate body  102  without deviating from the scope of the invention as long as each of the first and second body portions  108 ,  110  comprises one K-wire hole. In another embodiment, only one of the first and second body portions  108 ,  110  may be provided with a K-wire hole. 
     The plate body  102  according to the invention is configured and dimensioned to be placed over a target portion of bone. In one embodiment, a length of the plate body  102  along the longitudinal axis  107  is approximately 55 mm. It is noted, however, that any other length of the plate body  102  may be used without deviating from the scope of the invention. A thickness of the plate body  102  is approximately 4 mm and a height of the second body portion  110  is approximately 16 mm. 
     As shown in  FIGS. 4-5 , a device  200  according to an alternate embodiment of the invention, is substantially similar to the device  100 , with like elements referenced with like reference numerals. An angle α 2  extends between the interface portion  109  and the orthogonal axis  111  of the plate body  102 , the angle α 2  being in the range of approximately 0-15°, although any other angle may also be used without deviating from the scope of the invention. Additionally, the device  200  is formed with the angle α 3  between the lateral wall  113  of the interface portion  109  and the plane housing the second body portion  110  which may for example, be between 20° and 35°. More specifically, the angle α 3  may be approximately 20°, 25° or 30°. It is noted however that the angle α 3  may have any other magnitude without deviating from the scope of the invention. The height of the second body portion  110  of the device  200  in this embodiment is approximately 20 mm. 
       FIGS. 6-9  depict the exemplary trajectories of the bone fixation screws  130  inserted through the plate body  102 , which trajectories are defined by the angles along which the bone fixation holes  114 ,  116 ,  120 ,  122  extend through the plate body  102 . The bone fixation screws  130  may be locking screws, cancellous screws or cortex screws. In an exemplary embodiment, the bone fixation holes are angled so that adjacent pairs of bone fixation screws  130  diverge away from one another, as shown in  FIG. 6 . Specifically, a first one of the bone fixation screws  130  may be angled at an angle β 1  of approximately 10° relative to a perpendicular axis (not shown) intersecting the second body portion  110 . A second one of the bone fixation screws may be angled at an angle β 2  of approximately 5° relative to the perpendicular axis (not shown), the angle β 2  extending away from the angle β 1  such that the first and second bone fixation screws diverge away from one another. A third bone fixation screw  130  may be angled at an angle β 3  of approximately 15° relative to a perpendicular axis (not shown) intersecting the second body portion  110 , as shown in  FIG. 8 . As those skilled in the art will understand, the diverging angles provide the opportunity to reduce interference of the bone fixation screws  130  and instruments (e.g., drill guides) with soft tissue. However, in another embodiment (not shown), the bone fixation holes  114  may be substantially parallel to one another or angled so adjacent pairs of the bone fixation screws converge toward one another. As those skilled in the art will understand, this embodiment aids in capturing specific portions of the anatomy (e.g., strong portions of bone) and may also aid in reducing interference with soft tissue and instruments. In yet another embodiment, the plate body  102  may be configured with any combination of converging, diverging and parallel bone fixation holes  114 ,  116 ,  120 ,  122 . 
       FIG. 10  depicts the device  100  in an operative configuration implanted over an ilial shaft  10  and ilial wing  14 , as will be discussed in greater detail below. 
     As shown in  FIG. 11 , a device  300  according to another embodiment of the invention is substantially similar to the device  100  of  FIGS. 1-3  with a length of a plate body  302  along the longitudinal axis  107  being, for example, approximately 55 mm. However, while the first and second body portions  108 ,  110  each includes three standard bone fixation holes and one combination hole, each of the first and second portions  308 ,  310 , respectively, of the device  300  includes only two fixation holes  314  and a single combination hole  316 . This allows the device  300  to be made shorter than the device  100 . For example, the device  300  may be made shorter than 55 mm permitting use in smaller animals, as those skilled in the art will understand. 
     As shown in  FIG. 12 , a device  400  according to yet another embodiment of the invention is substantially similar to the device  100  of  FIGS. 1-3  except that fixation holes  414 ,  416  extending through the plate body  402  are smaller in diameter. For example, the holes  414 ,  416  may be configured and dimensioned to receive screws having a diameter of approximately 2.7 mm, permitting the device  400  to be made smaller than the device  100 . This makes possible the production of a device  400  which is shorter than 55 mm permitting the use thereof in smaller animals, as those skilled in the art will understand. 
     As shown in  FIGS. 13-14 , a device  500  according to another embodiment of the invention is substantially similar to the device  100  of  FIGS. 1-3  with the exception of the placement of bone fixation holes  514 ,  516 . Furthermore, a point of intersection of first and second body portions  508 ,  510  may be altered as necessary to conform to a particular anatomy of a target bone, as those skilled in the art will understand. It is therefore noted that the illustrations depicted herein are exemplary only and that any other point of intersection of the first and second body portions  508 ,  510  may be used without deviating from the scope of the invention. The first and second body portions  508 ,  510  may also comprise deflected wall portions  509 ,  511 , respectively, configured to conform to the anatomy of the ilial shaft  10  when positioned thereover. Each of the wall portions  509 ,  511  deflects away from the plane housing the corresponding one of the first and second body portions  508 ,  510  by an angle selected to match the corresponding bone geometry. In one exemplary embodiment, the deflection may be approximately 10° relative to a plane housing the second body portion  510 . It is noted that any of the devices disclosed herein may comprise any number and arrangement of deflected wall portions without deviating from the scope of the invention. 
     In accordance with an exemplary method according to the invention, two or three osteotomies are made in the bone in accordance with one of a TPO and a DPO procedure, wherein the surgeon may determine, prior to the surgery, which method is most suitable for the animal. Specifically, if the surgeon determines a TPO procedure is necessary, a first osteotomy is made in the pubic bone, a second osteotomy in the ischium and a third osteotomy in the ilium The osteotomies may be made via any known device, as those skilled in the art will understand. Once the osteotomies have been made, the surgeon rotates the acetabulum sufficiently to seat the head of the femur into a desired orientation within the acetabulum. The device  100  may then be positioned as shown over the ilial shaft  10  under guidance of K-wires inserted through the K-wire holes  124 ,  126 . As those skilled in the art will understand, if a DPO procedure is used, only two osteotomies are performed, one in the pubis and the other in the ischium. The device  100  is positioned caudally over the osteotomy in the ilium, as those skilled in the art will understand. In an exemplary method, the first body portion  108 , located caudally along the device  100 , may then be secured to the bone first. However, those skilled in the art will understand that regardless of the orientation (e.g., right or left), in this example, a caudally located portion of the device  100  is secured to the bone first. Furthermore, as those skilled in the art will understand, the order of the steps of the surgical steps disclosed herein is exemplary only. Any other order of the steps may be employed to conform to the requirement of a particular application, surgeon preference, etc. without deviating from the scope of the invention. 
       FIGS. 15-16  depict a device  600  having a plate body  602  in accordance with another embodiment of the invention, the device  600  being formed substantially similar to the device  100  of  FIGS. 1-3  with the exception of the number and placement of bone fixation holes  614 ,  616 . That is, the first body portion  108  of the device  600  includes three fixation holes  614  while the second body portion  110  includes three fixation holes  614  and one combination hole  616 . The second body portion  110  further comprises a recess  618  extending between the combination hole  616  and an adjacent one of the fixation holes  614 . As those skilled in the art will understand, the recess  618  serves to prevent the formation of sharp edges on an outer surface of the plate body  602  after performing a milling procedure therethrough. A nominal separation of 1 mm. is provided between the holes  614 ,  616 . It is therefore noted that the illustrations depicted herein are exemplary only and that any other size, shape and position of the recess  618  may be used without deviating from the scope of the invention. 
     It will be apparent to those skilled in the art that various other modifications and variations may be made in the structure and the methodology of the present invention, without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of the invention provided that they come within the scope of the appended claims and their equivalents.