FR2875127A1 - Right hand wrist prosthesis, has plate with side cooperating with pad`s side, and metacarpal part with side cooperating with pad`s another side, to obtain pad translation relative to plate and two rotations of part relative to pad - Google Patents

Abstract

The prosthesis has a pad with sides (23, 24), and placed between a radial plate (1) and a metacarpal part (10). The plate`s side (2) and the side (23) cooperate via translational sliding, and the part`s side (11) and the side (24) cooperate in relative rotation. The cooperation of the sides allows to obtain a translation of the pad relative to the plate and two rotations of the part relative to the pad around two orthogonal axes.

Description

Wrist prosthesis

  The present invention relates to so-called "wrist" prostheses able to replace the articulation between the radius and at least one metacarp relating to a finger of a hand.

  It is already known wrist prostheses. However, none of the currently known embodiments of the Applicant can reproduce the movements of a hand that are substantially equivalent to two rotations respectively about two substantially perpendicular axes, one perpendicular to the plane defined by the hand when it is deployed flat. , for example on a table, an amplitude of about forty five degrees outwards (as opposed to the other hand, that is to say away from this other hand) and in general less than ten degrees inwards, and the other content in the plane of the hand. These two movements are well known and will not be more fully described here.

  Also, the present invention is intended to provide a wrist prosthesis that reproduces the natural movements of the hand of a human whose wrist has not been damaged by an illness. or an accident.

  More specifically, the subject of the present invention is a so-called "wrist" prosthesis capable of replacing the articulation between the radius and at least one metacarp relating to a finger of a hand substantially defining a so-called "hand" plane when it is deployed flat, characterized in that it comprises: É a radial plate having a first face, É first means for securing the radial plate with the distal end of the radius, É a metacarpal piece having a second face, É des second means for securing the metacarpal piece with the metacarp relating to a finger of the hand, É a pad having a third face and a fourth face, said pad being interposed between the radial plate and the metacarpal piece so that the first and third faces cooperate by translational sliding on one another and that the second and fourth faces cooperate in rotation with respect to each other, for to obtain a translation of the pad relative to the radial plate and two rotations of the metacarpal piece relative to the pad around two substantially orthogonal axes.

  Other features and advantages of the invention will become apparent from the following description given with reference to the accompanying drawings for illustrative but not limiting purposes, in which: FIG. 1 represents, in schematic form, such a prosthesis implanted on a right hand of a human being, in order to clearly highlight its implantation with respect to the bones constituting such a hand, FIGS. 2 and 3 respectively represent two sectional views along two orthogonal planes, of a first preferred embodiment of FIG. a wrist prosthesis according to the invention for the right hand, FIG. 2 illustrating different lateral rotations that can be obtained with a hand in which a prosthesis according to the invention is implanted, FIG. 3 further comprising an insert for representing, at a larger scale, part of the prosthesis shown as a whole in this FIG. 3, FIG. section of a second preferred embodiment of an improved wrist prosthesis according to the invention, also for right hand, illustrating different lateral rotations that can be obtained with a hand in which is implanted a prosthesis according to the invention, and FIG. 5 represents a diagrammatic view, on an enlarged scale, of a portion of the wrist prosthesis according to the invention applicable to the two embodiments according to FIGS. 2 to 4, this part actually corresponding to that represented in FIG. inset of Figure 3, but on an even larger scale to bring out all its structural features.

  It is first of all specified that, in the figures, the same references designate the same elements, whatever the figure on which they appear and whatever the form of representation of these elements. Similarly, if elements are not specifically referenced in one of the figures, their references can be easily found by referring to another figure.

  It is also stated that the figures represent two embodiments of the object according to the invention, but that there may be other embodiments that meet the definition of this invention.

  It is furthermore specified that, when, according to the definition of the invention, the object of the invention comprises "at least one" element having a given function, the embodiment described may comprise several of these elements. Conversely, if the embodiments of the object according to the invention as illustrated comprise several elements of identical function and if, in the description, it is not specified that the object according to this invention must obligatorily comprise a number particular of these elements, the object of the invention may be defined as comprising "at least one" of these elements.

  Finally, it is specified that when, in the present description, an expression alone defines, without specific specific mention concerning it, a set of structural characteristics, [for example E = E (p, ti, s, ...)] these characteristics can be taken, for the definition of the object of the protection requested, when technically possible, either separately, [eg g, and / or i, and / or p,

  .], either in total and / or partial combination, [eg E (s, i, p), and / or E (g, -r), and / or E (t, p), and / or E ( s, p)] ... DTD: With reference to the figures appended to the present description, the so-called "wrist" prosthesis Po;. is able to replace, in FIG. 1, the articulation between the radius Rad and at least one metacarp Met relative to a finger Said with a hand substantially defining a plane called "hand" when it is deployed flat.

  In a preferred embodiment, as shown in FIG. 1, the finger Said relative to the Met metacarp associated with the wrist prosthesis is the central finger, that is to say the "major finger".

  The wrist prosthesis according to the invention comprises a radial plate 1 comprising a first face 2, first means 3 for securing the radial plate 1 with the distal end 4 of the radius Rad, a metacarpal piece 10 comprising a second face II, second means 12 for securing the metacarpal piece 10 with the metacarp Met, a pad 20 comprising a third face 23 and a fourth face 24, the pad 20 being interposed between the radial plate 1 and the metacarpal piece 10.

  With such a wrist prosthesis structure, it is possible to reproduce all the original movements of a hand having a healthy wrist, that is to say so that the first 2 and third 23 faces cooperate by sliding in translation on one another and that the second 11 and fourth 24 faces cooperate in rotation with respect to one another, to obtain a translation of the pad 20 relative to the radial plate 1 and two rotations of the metacarpal piece 10 with respect to the pad 20 around two orthogonal axes.

  The movements that can be obtained and their amplitude are more particularly illustrated in FIGS. 2 to 4 which represent, on a scale, two embodiments of the wrist prosthesis according to the invention.

  In a more advantageous embodiment than the one whose structural definition is given above, the first 2 and third 23 faces are substantially defined in a sliding plane 30 forming a non-zero angle with the plane of hand, and one of the two second 11 and fourth 24 faces is constituted by a first surface 31 having one of two forms: circular crown sector, circular chute, the other of these second 11 and fourth 24 faces being constituted by a second surface 32 having other of the two forms.

  The circular trough and ring have transverse sections substantially complementary to one another so that the first and second surfaces 31, 32 cooperate in rotation with one another, on the one hand with a first axis 33 substantially perpendicular to the plane of hand, and secondly around a second axis 34 substantially orthogonal to this first axis 33.

  Although either of these two solutions is possible, it is however preferable, especially to obtain the smallest possible footprint, as shown in Figures 2 to 5, that the second face 11 is constituted by the first surface 31 in the shape of circular ring sector, and that the fourth face 24 is itself formed by the second surface 32 in the form of a circular chute.

  According to one embodiment which gives good results, in particular for obtaining movements of the hand as close as possible to the movements of origin with a healthy wrist, the sliding plane 30 defined above makes with the axis 39 of the radius a angle of about 85. In one embodiment of the Applicant which gave very good results, this angle was equal to 85.77.

  Preferably, the wrist prosthesis further comprises means 40 for guiding the first and third faces 2, 23 in translation along a line 41 defined by the intersection of the sliding plane 30 and the hand plane. These means 40 for guiding the first and third faces 2, 23 in translation are advantageously constituted by two slides, as shown in Figures 2 to 5.

  Advantageously, as more particularly visible in the schematic figure 5, to avoid a tailgating effect when the hand is rotated substantially around the second axis 34 contained in its plane as defined before, FIG. 3, when the metacarpal piece pivots between two positions corresponding to the positions of the hand in extension Pe and flexion Pf, the first surface 31 defined above has a cross section comprising a first arc 51 of radius of value s2, whose center 35 is substantially located on the second axis 34, and two second and third arcs of circles 52, 53, or the like, advantageously respectively of two non-coinciding centers 36-1 and 36-2 and of radius 522, 522 being less than S21, these second and third arcs circles being located in continuity of the first arc and symmetrically on either side of this first arc. As for the second surface 32, it then advantageously has a cross section consisting of a fourth arc of radius of radius equal to QI.

  In fact, for relatively small rotational amplitudes of the hand around the second axis 34 contained in its plane, this axis 34 is relatively fixed with respect to the pad 20 and passes through the center 35. For higher rotation amplitudes, this second axis 34 tends to move in translation parallel to itself in a space substantially defined by three axes parallel thereto and passing respectively through the centers 35, 36-1 and 36-2 arcs of circles defined above.

  In addition, to optimize the operation of the wrist prosthesis according to the invention, it is advantageous that the value 0) 2 of the angle at the center of the fourth arc corresponding to the second surface 32 is greater than the value wi of the angle at the center of the first arc 51.

  FIG. 5 shows, in thick lines, the position Pe of the metacarpal piece 10 relative to the pad 20 when the hand is in an extended position, that is to say in the plane of hand defined above. and, in fine lines, the position Pf of this same metacarpal piece 10 when the hand is in a bending position. The comparison of these two positions makes it quite clear that the metacarpal piece 10 does not come into contact with the edge of the pad 20 and even allows a rotation of almost ninety degrees on each side of its extended position Pe as shown in FIG.

  FIG. 4 shows another embodiment of the prosthesis, improved with respect to the embodiment described above, for the case where it is necessary to produce a total wrist prosthesis able to replace the entire articulation between the hand, and the ulna and the radius. In this embodiment, the wrist prosthesis further comprises a first 60 of the two parts of a patella 61 of radio-cubital prosthesis 62, this first part of ball 60 being integral with the radial plate 1 and the other being able to to be secured to the distal end 64 of the cubitus Cub.

  The radio-ulnar prosthesis 62 may for example be of the type described in FR-A-2660856 in the name of Mr. Kapandji Adalbert.

  In the embodiment according to FIG. 4, the first ball portion 60 which is integral with the radial plate 1 is the female part of the ball 61, the male part of the ball joint being integral with the distal end 64 of the ulnar Cab. Of course, a reverse realization is just as possible.

  It is finally specified that, preferably, the radial plate 1 and the metacarpal piece 10 are made of a material such as stainless steel, and the pad 20 of polyethylene or the like.

  With a wrist prosthesis structure as described above, it is possible to obtain all the rotations of the hand, both lateral, Figures 2 and 4, in flexion, Figures 3 and 5.

  These movements are easily deduced from this structure and, consequently, in order to simplify the present description, these movements will not be more fully explained here.

Claims (1)

7 CLAIMS   1. Prosthesis called "wrist" (Po;) capable of replacing the articulation between the radius (Rad) and at least one metacarp (Met) of a finger (Dgt) of a hand substantially defining a plane called "de hand "when it is deployed flat, characterized in that it comprises: E a radial plate (1) having a first face (2), É first means (3) for securing the radial plate (1) with the distal end (4) of the radius (Rad), É a metacarpal piece (10) having a second face (11), É second means (12) for securing the metacarpal piece (10) with the metacarp (Met) of a finger (Dgt) of the hand, É a shoe (20) having a third face (23) and a fourth face (24), said shoe (20) being interposed between the radial plate (1) and the metacarpal piece (10). ) so that the first (2) and third (23) faces cooperate by translational sliding on one another and the second (11) and fourth (24) faces coo rotate relative to each other, to obtain a translation of the shoe (20) relative to the radial plate (1) and two rotations of the metacarpal piece (10) relative to the pad (20) around two substantially orthogonal axes (33, 34).   2. Prosthesis according to claim 1, characterized in that É the first (2) and third (23) faces are substantially defined in a sliding plane (30) forming a non-zero angle with the plane of hand, that Él one of the two second (11) and fourth (24) faces is constituted by a first surface (31) having one of the following two forms: circular crown sector, circular chute, the other of these second (11) and fourth (24) faces being constituted by a second surface (32) having the other of the two forms, E said circular trough and ring having cross-sections substantially complementary to each other so that the first and second surfaces (31) , 32) cooperate with each other in rotation about a first axis (33) substantially perpendicular to the plane of hand.   3. Prosthesis according to claim 2, characterized in that the second face (11) is constituted by the first surface (31) shaped circular ring sector, and the fourth face (24) is constituted by the second surface (32) shaped circular chute. 4. Prosthesis according to one of claims 2 and 3, characterized in that said sliding plane (30) made with the axis (39) of the radius an angle of about 85.   5. Prosthesis according to one of claims 2 to 4, characterized in that it comprises means (40) for guiding the first and third faces (2, 23) in translation along a line (41) defined by the intersection of the sliding plane (30) and the plane of hand.   6. Prosthesis according to claim 5, characterized in that the means (40) for guiding the first and third faces (2, 23) in translation are constituted by two slides.   7. Prosthesis according to one of claims 2 to 6, characterized in that the first surface (31) has a cross section having a first arc (51) radius value S2, and two second and third arcs of circles (52, 53) of radius of value 522, Q2 being smaller than n, the second and third arcs being located in continuity with the first arc and symmetrically on either side of this first arc.   8. Prosthesis according to claim 7, characterized in that the second surface (32) has a cross section consisting of a fourth arc of radius of radius 52.   9. Prosthesis according to claim 8, characterized in that the value 02 of the angle at the center of the fourth arc is greater than the neck value of the angle at the center of the first arc (51).   10. Prosthesis according to one of claims 1 to 9, characterized in that it further comprises a first (60) of the two parts of a ball joint (61) of radio-ulnar prosthesis (62), said first part ball joint (60) being integral with the radial plate (1) and the other part of the ball joint being able to be secured to the distal end (64) of the ulna (C b).