Patent Publication Number: US-2015066094-A1

Title: Orthopedic implant in the form of a plate to be fixed between two bone parts

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 12/918,116, filed Nov. 1, 2010, which is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/FR2009/051878, filed Oct. 2, 2009, which claims priority from French Patent Application 0856693, itself filed Oct. 2, 2008, all of which are herby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to the technical field of orthopedic implants. 
     More particularly, the invention relates to a plate for arthrodesis or osteosynthesis adapted to be fixed between two bone parts. 
     In a manner known to one having ordinary skill in the art, this type of plate generally has holes for anchor screws, allowing arthrodesis between two bones or an osteosynthesis between two bone fragments. This is, for example, the case for the bones of the hand or foot, without however excluding other applications, particularly in the field of the spine. Depending on the pathological case to be treated, these plates can have a general rectilinear shape or have other geometric shapes. 
     From this state of the art, one of the objects the invention proposes to attain is to improve, in a sure and efficient manner, the compression in a precise direction between the bone parts held by the plate. 
     To attain this object, an orthopedic implant has been invented and designed in the form of a plate adapted to be fixed between two bone parts by screws engaged in throughgoing holes extending through the entire thickness of the plate. 
     According to the invention, the formations of the plate adapted to ensure, under a screwing effect, an adjustable compression force to bring the two bone parts closer together, are formed by at least one seat having a cross-section defining several distinct regions adapted to cooperate with a screw in order to generate a progressive straight-line displacement of the screw during the screwing action corresponding to a displacement of at least one of the bone parts, causing the compression force. 
     To attain the given object of obtaining a controlled and adjustable compression, one of the regions is constituted of a hole having a diameter D1 adapted to receive the screw head, whereas another region is a hole having a diameter D2 less than the diameter D1, and having, over a determined height, a slope between 40° and 60°, the regions being connected by an intermediate region having a slope in the direction of the region constituted by the hole having the diameter D1. 
     Advantageously, the slope of the intermediate region is comprised between 15° and 30°. 
     Another problem that the invention proposes to resolve is to ensure a temporary fixation of the plate so as to facilitate the fixation of the latter by the operator by means of pins and to allow, after the pins are set in place in one of the bone parts, sliding under the plate at the time of screwing while ensuring a compression according to a precise direction. 
     To solve such a problem, the plate has, in a known manner, a guide hole for the insertion of a pin on the side of one of the bone parts, and another guide hole for the insertion of a pin on the side of the other bone part. 
     According to the invention, one of the guide holes is a circular hole whose diameter corresponds substantially to that of the pin, and the other guide hole is an elongated slot. 
     To solve the given problem of respecting the anatomy, particularly in the case of an MTP arthrodesis plate, the axis of the elongated slot extends relative to the longitudinal axis of the plate at an angle between about 1° and 10°. 
     Generally, the plate has smooth and/or threaded holes adapted to receive anchor screws to the bone parts. 
     According to this base-design of the plate and of the pathological case to be treated:
         Either the different holes are aligned;   Or some of the holes are arranged according to the apex of a triangle or of a quadrilateral.       

     In one embodiment, the plate is longitudinally centered so as to adapt to the curvature of the bone parts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described hereinafter in more detail with reference to the attached drawings, in which: 
         FIG. 1  is a perspective view of an embodiment of a plate according to the invention; 
         FIG. 2  is a partial, large-scale, perspective view showing the compression seat; 
         FIG. 3  is a longitudinal cross-section corresponding to  FIG. 2 ; 
         FIGS. 4 ,  5 , and  6  are partial, cross-sectional, schematic, perspective views showing the compression obtained as the screw is pressed into the compression seat; 
         FIG. 7  is a perspective view of another embodiment of the plate, particularly for MTP arthrodesis; 
         FIGS. 8 ,  9 , and  10  are perspective views of embodiments of plates of other shapes; 
         FIG. 11  shows an embodiment of a plate longitudinally shaped to fit to the curvature of the bone; 
         FIGS. 12 to 18  are perspective views showing the installation and fixation of the plate on two bone parts for compressing same together, the bone parts being schematically shown as parallepipedal blocks; 
         FIG. 19  is a partial view of the plate showing, schematically, two extreme positions of the initial boring to obtain maximum compression (position 1) or no compression (position 0). 
     
    
    
     DETAILED DESCRIPTION 
     The osteosynthesis and/or arthrodesis plate is indicated generally at 1. In a known manner, this plate  1  has smooth and/or threaded holes  1   a  for anchor screws  2  screwed into bone parts O 1  and O 2 , as described below. 
     According to a characteristic of the invention, the plate  1  has at least one compression seat or formation  1   b.    
     As shown, in particular in  FIGS. 2 and 3 , this seat  1   b  has several distinct regions  1   b   1 ,  1   b   2 , and  1   b   3  that allow the desired compression to be set, particularly as a function of the bone quality and as a function of the start position of a screw  3  in the seat. 
     More particularly, the seat  1   b  is formed by three distinct regions having the following characteristics: 
     The region  1   b   1  is a hole having a diameter D1, adapted to receive the head  3   a  of the screw  3 . 
     The region  1   b   2  is a hole having a diameter D2 less than the diameter D1 and having, over a determined height, comprised between about 1 and 2 mm, a slope on the order of 40° to 60° relative to a base plane of the plate. 
     The regions  1   b   1  and  1   b   2  are connected by an intermediate transition region  1   b   3  having a down slope, that is, angled downward in the direction of the region  1   b   1 . This slope is between about 15° and 30°. 
     Considering these characteristics, compressing together the two bone parts O 1  and O 2  is carried out as follows, with reference, in particular, to the  FIGS. 4 ,  5 ,  6 ,  15 , and  16 . 
     A pilot hole is first made in one of the bone parts being considered according to the region  1   b   2  or  1   b   1  as a function of the compression one wants to obtain. 
     The screw  3  is inserted into the hole until its head  3   a  contacts the plate  1  ( FIGS. 4 and 5 ). 
     Since the hole of the region  1   b   2  has a diameter smaller than that of the screw head  3 , this head immediately slides so as to be offset from the axis of the region  1   b   1 , causing a first, rapid compression. 
     With continued screwing action, the screw head  3   a  is slides along the slope of the intermediate region  1   b   3  causing a second compression until it reaches a stable position fitting in the hole  1   b   1  whose diameter is the same as that of the screw head  3   a . Naturally, it is possible to stop at any intermediate position in order to precisely adjust the compression. 
     It must be noted also that the extent of compression generated is on the order of 0 to 3 mm and can be controlled as a function of the position of the initial passage. Therefore, it is possible to obtain maximum compression at a seat in position 1 and no compression at a seat in a position 0 ( FIG. 19 ). 
     According to another characteristic, the plate  1  has at least one guide hole  1   c  for the insertion of a guide pin  4  for temporarily fixing the plate  1 . Advantageously, the plate  1  has a guide hole  1   c  for the insertion of a pin  3  on the side of one of the bone parts O 1  and another guide hole  1   d  for the insertion of another guide pin  5  on the side of the other bone part O 2 . 
     Considering the effect of the desired compression, such as previously mentioned, the guide hole  1   c  is a circular hole whose diameter corresponds substantially to that of the pin  4 , whereas the other guide hole  1   d  is an elongated slot, located on the side of the compression seat  1   b.    
     These provisions therefore enable the bone to slide relative to the plate  1  at the time of screwing, while ensuring compression in a precise direction generally along the axis of the plate. The pins  4  and  5  are of any known and appropriate type, and perfectly know to one having ordinary skill in the art. 
     The elongated slot  1   d  for temporary fixation is particularly well adapted in the case of an MTP arthrodesis plate in order to take into account the anatomy according to which the angle between the phalange P1 and the metatarsus  1  is on the order of 10°. Indeed, a plate according to the state of the art makes it difficult to ensure the compression while keeping the above-described angle. According to the invention, the slot  1   d  only has to be angularly oriented relative to the median axis of the plate  1  according to an angle of about 5° ( FIG. 7 ). 
     As shown in the figures of the drawings, the plate  1  can have different shapes, with the holes  1   a  aligned as in  FIG. 1  or arranged, all or in part on the corners of a triangle or of a quadrilateral ( FIGS. 8 ,  9 , and  10 ). More particularly, in  FIG. 8 , the plate is adapted to be used in the case of a Lapidus arthrodesis, in  FIG. 9 , for a basal osteotomy of the first metatarsus and for a ⅔ Lisfranc arthrodesis ( FIG. 10 ). These provisions of the screw, in a triangle or in a quadrilateral, improve the mounting stability. 
     It must be noted also that the plate  1 , no matter its geometric shape, can be bent longitudinally so as to adapt to the curvature of the bone ( FIG. 6 ) making it possible, as a consequence, for the screws  2  to form an angle relative to one another ( FIG. 11 ). 
     With reference to  FIGS. 12 to 18  that show the setting in place of the plate according to the invention: 
     After the osteotomies have been carried out, the plate  1  is positioned between the two bone parts O 1  and O 2  ( FIG. 12 ). 
     The surgeon stabilizes the plate  1  with the two temporary pins  4  and  5 , one of which is engaged in the hole  1   c  and whereas the other one in the slot  1   d  ( FIG. 13 ). 
     At least one screw  2  is engaged through the hole  1   a  and screwed into the bone part O 1  where there is no compression formation  1   b  is not positioned ( FIG. 14 ). 
     The surgeon then screws the screw  3  in the compression lug  1   b , choosing the extent of compression as previously indicated ( FIG. 15 ). 
     Once the compression is done ( FIG. 16 ), the surgeon can screw in one or more additional screws  2  ( FIG. 17 ), then remove the guide pins  4  and  5  ( FIG. 18 ). 
     The advantages are readily apparent from the description.