Abstract:
A device for fixing an implant in a patient&#39;s bone which includes an expanding element which is limited in it&#39;s plastic deformation when a force is applied for fixing the implant in the bone, such that the expanding element is reversible when another force is applied for removing the implant from the bone.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase Application of International Application PCT/FR99/00940, filed Apr. 21, 1999 which claims priority from French Patent Application 98 05202, filed Apr. 21, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a reversible device for the fixation of an implant in the bone of a patient. 
     2. Brief Description of the Related Art 
     U.S. Pat. No. 5,501,695 discloses a device for the fixation of a suture anchor in the bone, which device consists of two separate parts. 
     The fixation device comprises a first firmly attached external, cylindrical element affixed to fixation prongs that are separated from each other by grooves running parallel to the longitudinal axis of said device. The first element accommodates on its inside a second element of deformation that interacts with the free extremity of the fixation prongs. 
     The second element of irreversible deformation is firmly affixed through a fracture zone to a tie rod which enables the surgeons, after having inserted the suture anchor into a hole previously drilled in the bone, to have the second element slide inside of the first one to axially deform the fixation prongs in the area of the spongy bone. 
     Since the tractile force is sufficient to deform the fixation prongs, the rod separates from the second element by an irreversible break. 
     It can be noted that the prongs deform laterally following a direction essentially perpendicular to the longitudinal axis of the suture anchor in order to permanently fasten the latter inside of the bone. 
     Lastly, to the first element is firmly affixed at one its extremities a flange that comes to rest against the cortical bone and into which are drilled a number of holes for the fastening of the suture threads by the surgeon. 
     The above-described fixation device presents some disadvantages, namely, that it does not allow the removal of the suture anchor from the bone without causing a complete destruction of the bone and of the bone to which it is attached. In fact, the suture anchor is not provided with any means of removal that would allow it to be disengaged from the bone without causing any damage to it. 
     Moreover, beyond the fracture zone of the second element, the fixation device is not provided with means that limit the displacement of said element to prevent the fixation prongs from breaking in an abnormal manner under the effects of the tractile force. 
     Also, U.S. Pat. No. 5,472,452 discloses a fixation device for a suture anchor provided with expansion means that are plastically deformed by means of an appliance. 
     This fixation device is provided with expansion means that are reversible within the direction of the stress of the appliance and, in particular, of the structure of the implement whose thruster presents an inclined plane allowing the means of expansion to descend into the body of the suture anchor in order to be able to remove it. 
     This fixation device relates to a suture anchor that is not provided with means to delimit the plastic deformation of the expansion means when a tractile force is applied, in order to prevent an abnormal rupture or an excessive plastic deformation which would render the fixation device irreversible. 
     Also known are other anchor fixation devices, either by force or by screws, that do not allow a removal of the implant without causing damage to the bone. 
     The present invention has the aim to specifically remedy these disadvantages. 
     SUMMARY OF THE INVENTION 
     The fixation device in accordance with the present invention has as object that of being reversible, thus allowing its removal from the bone without having to drill a hole of greater diameter than that of the deformed prongs. 
     The fixation device in accordance with the present invention is provided with expansion means that are reversible in the direction of the force in order to allow either the fixation of the implant to the bone or its removal. 
     The fixation device in accordance with the present invention comprises expansion means whose plastic deformation is limited by stop means when a force is applied for the fixation of the implant to the bone, so that said expansion means become reversible when another force is applied enabling the removal of the implant from the bone. 
     The fixation device in accordance with the present invention comprises expansion means that are limited by stop means in their plastic deformation when a force is applied that allows the fixation of the implant to the bone, so that these expansion means be reversible when another force is applied that allows the removal of said implant from the bone. 
     The fixation device in accordance with the present invention is provided with expansion means that consist, on the one hand, of a cylindrical section provided with an internal threaded borehole, at least two fixation prongs arranged parallel to the longitudinal axis and on the extension of the cylindrical section, and at least two stops inserted between each prong that limit the plastic deformation of said prongs, and a conical point with a threaded blind hole on its inside. 
     The fixation device in accordance with the invention is provided at the level of its conical point with a threaded blind hole intended for a threaded rod of an attachment to deform the fixation prongs subjected to a tractile force in a direction essentially parallel to the longitudinal axis. 
     The fixation device in accordance with the present invention is provided in its cylindrical section with a threaded borehole that is intended for a threaded hollow rod of another attachment, while another rod sliding inside the first one comes to rest against the bottom of the threaded blind hole to open, under the effect of a thrust force, the fixation prongs in a position essentially identical to the original one in order to be able to remove the implant from the bone. 
     The below description, taking into account the accompanying drawings, given as not limiting examples, allows a better understanding of the invention, of its characteristics and the advantages it may provide. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view illustrating an implant of whatsoever shape provided with a fixation device in accordance with the present invention. 
     FIGS. 2 a  to  2   c  are diagrammatic views illustrating the placing of the implant in a bone by means of the fixation device in accordance with the invention. 
     FIGS. 3 a  to  3   c  are diagrammatic views illustrating the removal of the implant from the bone due to the reversibility of the fixation device in accordance with the present invention. 
     FIG. 1 illustrates an implant  1  that can be of whatsoever shape and that is provided with a fixation device  2  comprising expansion means  21  that are reversible, which fact enables the surgeon to operate anew with the implant  1  without causing much damage to the bone  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The fixation device  2  comprises a hollow cylindrical section  4 , on the inside of which is drilled threaded borehole  5 . 
     The cylindrical section  4  of the fixation device  2  is extended by at least two fixation prongs  6 ,  7  that, prior to deformation, are parallel to the longitudinal axis XX′ of the cylindrical section  4 . 
     The fixation device  2  comprises on the extension of the prongs  6  and  7  a conical point  8 , facilitating the insertion of the implant into the bone  3 . 
     The cylindrical section  4  of the fixation device  2  is provided on its inside with a threaded borehole  9  on the longitudinal axis XX′ that opens, on the one hand, to the outside of the implant  1  and, on the other hand, between the fixation prongs  6  and  7 . 
     Also, the conical point  8  of the fixation device  2  is provided on its inside with a threaded blind hole  9  that opens between the fixation prongs  6  and  7 , which hole is drilled on the same longitudinal axis XX′ as that of the borehole  5 . 
     Further, the diameter of the threaded borehole  5  is greater than that of the threaded blind hole  9 . 
     The prongs  6  and  7  are attached to the cylindrical section  4  and to the point  8  by means of bending fasteners  10  oriented in direction towards the center of the fixation device  2 , allowing the deformation of said prongs under the effects of a tractile force. 
     The prongs  6  and  7  are provided in their center with bending fasteners  11 ,  12 , respectively, that are inverted with respect to the ones  10 , so that each prong is constituted by two segments  6   a ,  6   b  and  7   a ,  7   b.    
     It can be observed that the bending fasteners  10 ,  11  and  12  have an arc of a circle shape of constant radius. 
     Between each prong  6  and  7  is provided a stop  13  attached to the cylindrical section  4  and oriented in direction towards the conical point  8 . Each stop  13  runs parallel to the longitudinal axis XX′ and has a length that depends on the deformation of the prongs  6  and  7  one wishes to obtain. 
     In fact, the deformation of the prongs  6  and  7  is limited by the stops  13  that come to rest against a surface  14  of the conical point  8 . The surface  14  is arranged on a plane that is perpendicular to that of the axis XX′. 
     In FIGS. 2 a  to  2   c  are illustrated the various stages of the placing inside of bone of the implant  1 , provided with the fixation device  2 . 
     In FIG. 2 a  is illustrated the implant  1  to which is affixed an attachment  15  for the setting in place that, by way of example, is constituted by a rod  16  that traverses the inside of the fixation device  2  to be screwed into the blind hole  9  of the conical point  8 . The rod  16  is attached to a sleeve  17  that comes to rest against the cylindrical section  4 . 
     In FIG. 2 b  is illustrated the implant  1  that is inserted into the surgical location by means of the attachment  15 . 
     The setting in place of the implant  1  in the bone  3  is effectuated either by force or by rotation, or with the aid of a preliminary hole drilled into the cortical bone  30  and the spongy bone  31 . 
     In FIG. 2 c  is illustrated the deformation of the fixation device  2  and, in particular, of the prongs  6  and  7  inside the spongy bone  31  when the rod  16  of the attachment  15  is subjected to a tractile force T. Thus, the rod  16  displaces horizontally in the direction of the axis XX′ while the sleeve  17  continues to rest against the cylindrical section  4 . 
     The deformation of the prongs  6  and  7  is limited until the surface  14  of the conical point  8  comes into contact with the stops  13 . 
     The prongs  6  and  7  are deformed, under the effect of the compression stress of the tractile force T applied to the rod  16  of the attachment  15 , according to the shape of the fasteners  10 ,  11  and  12 , so that the segments  6   a ,  6   b  and  7   a ,  7   b  are oriented towards the outside of the implant  1  and in a direction essentially perpendicular to the axis XX′. 
     It can be observed that the fixation of the implant  1  in the spongy bone  31  is effectuated by the deformation of the prongs  6  and  7  until the segments  6   a  and  7   a  come into contact with the internal surface of the cortical bone  30 . 
     Then, the rod  17  is unscrewed from the attachment  16  in order to release the implant  1 . 
     In FIGS. 3 a  to  3   c  are illustrated the various stages of the removal of the implant  1  from the bone  3  by means of another attachment  18  allowing the reversibility of the fixation device  2 . 
     The attachment  18  is provided with a hollow rod  19  that is screwed into the threaded borehole  5  of the cylindrical section  4 , while another rod  20  sliding in the first one comes to rest against the bottom of the blind hole  9  drilled in the conical point  8  (FIG. 3 b ). 
     The rod  20  is subjected to a thrust force P parallel to the axis XX′ in order to open the prongs  6  and  7  (FIG. 3 c ). The shape of the fasteners  10 ,  11  and  12  allows to return the fixation device  2  to a shape similar to the original one. 
     When the fixation device  2  has returned to an elongated position, by means of the attachment  18 , the surgeon can remove the implant  1  from the bone  3  without having to drill a hole with an approximate diameter of the deformed prongs. 
     The above described fixation device has been applied by way of embodiment to a suture anchor. Evidently, and without changing the object of the present invention, it is intended that the reversible fixation device be applied to any type of implant to be inserted into the bone of a patient.