FR2660856A1 - Lower radioulnar prosthesis - Google Patents

Abstract

The present invention relates to orthopaedic prostheses. The prosthesis 1 according to the invention is characterised essentially by the fact that it comprises two parts 2, 3 forming a ball and socket, namely a female part 2 having an open cavity 4, and a male part 3 having a spherical head 5, means 6 for fixing the female part on a first portion of bone, and means 7 for fixing the male part on a second portion of bone. The open cavity 4 is formed by a well 10 which is cylindrical in revolution having a radius equal to that of the head 5, and a hemispherical base 11 having a radius equal to that of the spherical head, and of which the centre 12 is situated on the axis of revolution 13 of the well 10, the opening 14 of the open cavity being in a plane 15 which forms, together with the axis of revolution 13, an angle equal to 135 DEG . Application in particular to the formation of a lower radioulnar prosthesis.

Description

Lower radio-cubital prosthesis
The present invention relates to lower radio-cubital prostheses for treating patients who have had trauma or who suffer from bone degeneration at the joint between the lower extremities of the ulna and the radius, in the case where one of the 'they or even both would have been the site of a degradation.

 There are many types of prostheses intended, in particular, to replace all or part of certain joints, for example between the bone of the femur and the bone of the pelvis or in the shoulder, when these joints can no longer function normally.

 Such prostheses comprise two main parts forming a ball joint, one of the "female" type generally of hemispherical hollow shape, the other of the "male" type generally substantially spherical capable of being contained and retained in the female part.

 In addition, each of these two parts are associated with means for securing it to the bone, the defective portion of which it must replace in order to correctly reconstruct the joint. These means are for example constituted by fixing lugs or the like, the shape of which is adapted to that of the bone in which or on which they are intended to be implanted, for example of elongated oblong shape for the part of a coxo prosthesis. -femoral intended to be inserted into the medullary canal of the femur, or in the form of a plurality of protuberances or orifices for the part of this same prosthesis intended to be fixed on the pelvic bone, depending on the method of fixation chosen for this part. Indeed, joint prostheses are divided into two groups: prostheses fixed in the bone by sealing with a "cement", for example methyl metacrylate, and prostheses fixed in the bone by means mechanical, without sealing, say "unsealed prostheses".

 The techniques well known for this kind of prostheses cannot however be used such as, for example, in the case of the replacement of the lower articulation existing between the ulna and the radius, in particular by the fact that they cannot reconstitute the totality of the complex relative movements existing between these two bones when the wrist and the hand are put in movement.

 The object of the present invention is to produce a prosthesis which finds a particularly advantageous application as a lower radio-cubital prosthesis allowing the patient to regain the rotational movements around the longitudinal axis of the forearm, wrist and hand. , called 'pronation' and "supination", while having a simple enough structure so that its realization is easy and that its implantation without sealing poses no difficulty to the operator.

 More specifically, the subject of the present invention is a prosthesis, in particular a lower radio-cubital prosthesis comprising two parts forming a ball joint, a first female part comprising an open cavity and a second male part comprising a substantially spherical head capable of cooperating with said open cavity. means for fixing the female part to a first portion of bone and second means for fixing the male part to a second portion of bone, characterized in that the said open cavity is composed of a cylindrical well of revolution d '' a radius substantially equal to that of said substantially spherical head and a substantially hemispherical bottom of a radius equal to that of said spherical head and the center of which is located on the axis of revolution of said well, the opening of said open cavity being defined in a plane making with the axis of revolution an angle substantially equal to 135 degrees.

Other characteristics and advantages of the present invention will appear during the following description given with reference to the drawings annexed by way of illustration, but in no way limitative, in which
FIG. 1 is a diagram representing the different bones constituting the lower part of the forearm and the wrist of the human body,
FIG. 2 shows, in exploded view and in perspective in the same assembly, two embodiments of the prosthesis according to the invention,
FIG. 3 represents a first embodiment of the prosthesis according to the invention implanted in a ulna, the lower end of which has been preserved, and
FIG. 4 represents a second embodiment of the prosthesis according to the invention implanted in a ulna whose lower end has been eliminated.

 Although the figures represent two embodiments of a prosthesis according to the invention, it is specified that, for the sake of simplification, identical means in the two modes bear the same references, whatever their representation in the different figures .

 The illustrated prostheses are more particularly adapted to be implanted in the lower region of an ulna 100 to replace, when damaged, the connection 150 between this ulna and the radius 200 which is associated with it at the wrist 151 of a hand 152, as illustrated in FIG. 1, thus constituting what surgeons call a lower radio-cubital prosthesis 1.

 The prosthesis 1 comprises two parts 2, 3 forming a ball joint, a first female part 2 comprising an open cavity 4 and a second male part 3 comprising a substantially spherical head 5 capable of cooperating with the open cavity, first fixing means 6 of the female part on a first portion of bone 101, of the ulna 100, and second fixing means 7 of the malt part on a second portion of bone, 102 of the ulna 100 or 201 of the radius 200.

 According to an advantageous characteristic of the prosthesis, the open cavity 4 is composed of a cylindrical well 10 of revolution with a radius substantially equal to that of the spherical head 5 and of a bottom 11 substantially hemispherical with a radius equal to that of the spherical head and whose center 12 is located on the axis of revolution 13 of the well 10. In addition, the opening 14 of the cavity is defined in a plane 15 making with the axis of revolution 13 a substantially equal angle at 135 degrees.

 In an advantageous embodiment, the fastening means 6 of the female part 2 on a first portion 101 of the ulna 100, in this case its upper portion called "proximal", comprise at least one tail 20 capable of being inserted in a housing 21 produced in this first portion of bone, and means 22 for securing the tail 20 with the portion of bone 101, these means advantageously comprising at least one lateral counterplate 23 capable of being placed against the external surface 24 of the end of the first portion 101 of the ulna and at least one fixing screw 25, advantageously two as illustrated, passing through, through a pair of orifices 26, 27 produced on the same axis 28 respectively in the tail 20 and the counter -side plate 23, at least the part 103 of the bone portion 101 between the tail 20 and the counter plate.

 Given the problem posed by the implantation of such a radio-cubital prosthesis, the prosthesis 1 also comprises means 30 for controlling the orientation in rotation of the female part 2 relative to the bone portion 101. In an advantageous embodiment, these means 30 comprise a connecting piece 31 disposed between the open cavity 4 and the tail 6 and comprising two flats 32, 33 located substantially in two planes parallel to the axis of revolution 13 of the well 10, and a control fork 34 with two branches 35, 36 separated from the distance separating the two flats 32, 33. In addition, in a particularly advantageous manner, the fork 34 is integral with the side counter plate 23 so that its plane does with that of the counter-plate a non-zero angle and even advantageously substantially equal to 90 degrees.

 As mentioned above, the prosthesis 1 comprises means 7 for fixing the male part 3 to a second portion of bone, the lower portion 102, called "distal", of the ulna 100, that is to say its lower epiphysis. These means comprise at least one tail 40 capable of being inserted into a housing 48 produced in the second bone portion 102 of the ulna 100 and means 41 for securing the tail 40 with this portion of bone. The means 41 are advantageously constituted by at least one lateral counter-plate 42 able to be placed against the external surface 43 of the bone portion 102 and at least one fixing screw 44 called "spongy screw", advantageously two, passing through , through a pair of orifices 45, 46 produced on the same axis 47 respectively in the tail 40 and the counter plate 42, at least the portion 104 of the bone portion 102 between the tail 40 and the counter plate, coming to bear on the opposite wall of the bone.

 The prosthesis 1 also comprises means 50 for controlling the orientation in rotation of the male part 3 with respect to the bone portion 102 of the ulna 100, these latter means 50 being able to be produced as the means 30 described above.

 As specified above, the figures, in particular 2, 3 and 4, illustrate two embodiments of the prosthesis. your part of the preceding description relates to a first embodiment more particularly suitable for the case where the lower end of the ulna could have been preserved and fused, by arthrodesis 80, with the lower end 201 of the radius 200. In this case, the Placement of prosthesis 1 requires prior preparation of the ulna consisting of resection of a short segment 155 of its diaphysis, equal to the place that the prosthesis will take. The second, more particularly suitable for the case where this end has already been removed by a previous operation, differs from the first only as regards the structure of the means 7 making it possible to fix the male part 3 on the second portion of bone constituted, in this case, by the lower end 201 of the radius 200. These means 7 are then advantageously constituted by at least one lug 60 and means 61 for securing this lug 60 with the lower end 201 of the radius 200, these latter means may be constituted by screws, advantageously of the cancellous bone type ".

 The lower radio-cubital prosthesis described in the two embodiments above is particularly advantageous in terms of its installation and in terms of its function.

 The installation of a lower radio-cubital prosthesis is generally made necessary by the degradation of the articulation 150. If the state of this degradation nevertheless allows the extremity of the ulna to be preserved, the surgeon will use prosthesis 1 under the first embodiment. For its installation, it must first separate the upper part 153 of the ulna 100 from the lower part 154 by removing, over a given length, the portion 155 of the ulna located just above the joint 150, its experience allowing him to determine the exact location and the length of this portion 155. By shifting the two upper and lower portions 153, 154 from their axis, he then realizes by means of a medical auger the two housings 21 and 48 according to the same axis direction 13, the original direction of the axis of the ulna.

 The two parts 2 and 3 of the prosthesis 1 are placed by plugging each tail into its corresponding housing. The establishment is however easier if one starts by placing the male part 3 on the lower part 154 of the ulna. Then, slightly pulling apart the upper part 153 of the ulna in relation to the lower part, the female part 2 of the prosthesis is plugged in so that the open face 14 of the well 10 is turned towards the radius 200 (position not shown on the figures). This position of the inclined slope of the opening 14 makes it easy to introduce the spherical head 5 therein to plunge it into the well 10 so that it comes into contact with the hemispherical bottom 11 when the traction on the upper part 153 of the ulna is deleted.

 Then, by means of the fork 34 placed in contact with the two flats 32, 33, the female part 2 of the prosthesis is pivoted by about half a turn to make it take the position illustrated in FIGS. 3 and 4, c that is to say so that the opening 14 is turned opposite to the radius 200.

 The fork 34 secured to the counter plate 23 is held so that its branches 35, 36 remain in contact with the two flats 32, 33, which makes it possible to position the orifices 27 opposite the orifices 26 made in the tail 20. The screws 25 can then be inserted into the holes 27 perpendicular to the plane of the counter plate, and will automatically fall into the holes 26 of the tail 20 to cause a rigid attachment of the tail 20 relative to the part 103 of the portion of bone 101 by pressing the counterplate against the external surface of this portion of bone.

 It is the same for fixing the tail 40 on the bone portion 102: the fork 50 is slid over the two flats of the male part 3 to possibly rotate it on the axis 13 until the counter plate 42 is placed, on the external surface of the portion 102 of the ulna, so that the screws 44 introduced into the facing orifices 45 and 46 can bite into the lower epiphysis 201 of the radius 200 according to the optimal orientation determined by the professional experience of the operator. However, in the particular case of this part of the prosthesis, to obtain the arthrodesis 80 of the lower part 154 of the ulna with the lower part 201 of the radius 200, the fixing means 7 must include at least one screw 44, and advantageously two, long enough to completely cross the lower part 154 of the ulna and come to be screwed in the lower part 201 of the radius to its opposite wall, and thus secure the two por bone, lower epiphysis 201 of the radius and lower epiphysis 154 of the ulna, after cutting their articular surfaces in region 150.

 FIG. 4 represents another embodiment of the prosthesis 1 more particularly suitable for the case where the lower part 154 of the ulna has been removed by a previous operation.

In this case, it is the fixing lug 60 which is secured directly to the lower part 201 of the radius 200.

 Such a prosthesis makes it possible to repair the joint 150 while preserving on the wrist 151 the natural movements of pronation and supination of the order of 90 degrees in each direction allowed by the rotation of the radius with respect to the ulna with an amplitude of the order of ten to fifteen degrees and, simultaneously, by the relative elongation of the ulna in relation to the radius, or its shortening according to the direction of rotation of the wrist. Indeed, the rotational movement is obtained by that of the spherical head 5 in the bottom of the well 10 and the relative variation in length of the ulna with respect to the radius is given, it, by the longitudinal displacement of the spherical head 5 in the well 10 along its axis of revolution 13, these two movements being transmitted to the lower part 154 of the ulna thanks to its connection with the lower epiphysis of the radius.

 From the above description, it is therefore apparent that the prosthesis according to the invention is as interesting for its ease of implantation as for its function which makes it possible to conserve or restore all the original movements of pronation and supination of a healthy wrist. .

Claims (10)

 1. Lower radio-cubital prosthesis 1 comprising two parts (2, 3) forming a patella, a first female part (2) comprising an open cavity (4) and a second male part (3) comprising a substantially spherical head (5) capable to cooperate with said open cavity, first fixing means (6) of the female part on a first bone portion (101), and second fixing means (7) of the male part on a second bone portion (102,201) characterized in that said open cavity (4) is composed of a cylindrical well (10) of revolution with a radius substantially equal to that of said spherical head (5) and of a bottom (11) substantially hemispherical with a radius equal to that of said spherical head and the center (12) of which is located on the axis of revolution (13) of said well (10), the opening (14) of said open cavity being defined in a plane (15) making with the axis of revolution (13) an angle substantially equal to 135 of sandstone.  2. Prosthesis according to claim 1, characterized in that said first fixing means (6) of said female part (2) on a first bone portion (101) comprise at least a first tail (20) able to be plugged into a first housing (21) produced in said first portion of bone and first means (22) for securing said first tail (20) with said first portion of bone (101).  3. Prosthesis according to claim 2, characterized in that said first means (22) for securing said first tail (20) with said first bone portion (101) comprise at least a first lateral counterplate (23), said first lateral plywood being able to be placed against the external surface (24) of said first portion of bone (101), and at least one first fixing screw (25) passing through, through two orifices (26, 27) made on the same axis (28) respectively in said first tail (20) and said first lateral counterplate (23), at least the part (103) of the first portion of bone (101) included between said first tail (20 ) and said first side counter plate (23).  4. Prosthesis according to one of claims 2 and 3, characterized in that it comprises first means (30) for controlling the orientation in rotation of said female part (2) relative to said first portion of bone (101).  5. Prosthesis according to claim 4, characterized in that said first means (30) for controlling the orientation in rotation of said female part (2) relative to said first bone portion comprise a connecting piece (31) disposed between said open cavity (4) and said first shank (20), said connecting piece comprising two flats (32, 33) located substantially in two planes parallel to the axis of revolution (13) of said well and a control fork (34) with two branches (35, 36) spaced from the distance separating the two said flats (32, 33).  6. Prosthesis according to claim 5, characterized in that said fork (34) is integral with said first lateral counter plate (23) so that the plane of said fork forms with that of the lateral counter plate a non-angle zero and advantageously substantially equal to 90 degrees.  7. Prosthesis according to one of claims 1 to 6, characterized in that said second fixing means (7) of said male part (3) on a second portion of bone (102) comprise at least a second tail ( 40) able to be inserted in a second housing (48) produced in said second portion of bone and means (41) for securing said second tail (40) with said second portion of bone.  8. Prosthesis according to claim 7, characterized in that said means (41) for securing said second tail (40) with said second portion of bone (102) comprise at least a second lateral counterplate (42), said second lateral counter plate being able to be placed against the external surface (43) of said second portion of bone, and at least one second fixing screw (44) passing through, through two orifices (45, 46) produced on a same axis (47) respectively in said second tail and said second lateral counterplate, at least the portion (104) of the second portion of bone included between said second tail and said second lateral plywood.  9. Prosthesis according to one of claims 7 and 8, characterized in that it comprises second means (50) for controlling the orientation in rotation of said male part (3) relative to said second portion of bone (102).  10. Prosthesis according to one of claims 1 to 6, characterized in that said second fixing means (7) of said male part (3) on a second portion of bone (201) comprise at least one fixing lug (60) and means for securing (61) said fixing tab with said second portion of bone.