FR2805151A1 - TRAPEZO-METACARPIEN PROSTHESIS WITH IMPROVED MOBILITY - Google Patents

Abstract

The present invention relates to a trapezo-metacarpal prosthesis comprising a first element (2) intended to be inserted into the metacarpus of the hand of a patient, a second element (6) intended to connect this first element to a third element (7) intended to be inserted into the trapezium of the patient's hand. According to the invention, the coupling between the second element and the first element allows the radial clearance between the first element and the second element.

Description

The present invention relates to a trapezo-metacarpal prosthesis with

mobility

  liorée. More specifically, the invention relates to a trapezometacarpal prosthesis which

  almost fully recover the functions of the trapezoid joint

patient's metacarpal.

  As we know, following arthritis pathologies affecting the hand, the functions of the thumb, that is to say of the joint between the trapezius and the metacarpus of the hand, can

  be greatly compromised to the point that the patient, in addition to suffering from severe pain

  its, no longer has the optimal functions of the thumb and that, therefore, even when

  completely normal gripping attempts he cannot succeed in completing this operation.

  To cope with a situation of the aforementioned type, there are currently different

  your techniques which aim to recover the functions of the trapezius and metacarpus.

  A first technique, known, is to weld the trapezius and the metacarpus between them, with the result that the patient no longer suffers, but with the disadvantage of losing

hand functions.

  A second technique, also of the surgical type, involves taking ligaments.

  elements of a different body region of the hand and implant these ligaments between the trapezius and the metacarpus in order to be able to recover their functions. However, this second

  technique is not favored by specialists because unsatisfactory results are obtained.

  A third operating technique involves inserting an appropriate prosthesis between the trapezius and the metacarpus. The insertion of the prosthesis must take place by resecting portions

  of the two bones so as to be able to define housings for the prosthesis.

  Prostheses of known type provide a rod intended to be inserted into the meta-

  carp, a collar which is inserted on one side into the rod and ends at the opposite end with a spherical head which engages in a complementary housing defined in a cup

  which is itself blocked in the trapezium of the hand.

  However, the use of the type of prosthesis described suffers from certain disadvantages, mainly

  due to the fact that the alignment between the rod inserted in the metacarpus and the acetabulum

  inserted in the trapezoid, is not always optimal, either due to a difference in leave

  between the trapezius and metacarpus from patient to patient, either because the definition of the em-

  placement in the metacarpus and trapezius may not be precise enough to

  allow perfect alignment between the rod and the corresponding cup.

  In addition, the flexion of the thumb in opposition to the palm of the hand provo-

  that an effect of rotation of the acetabulum in the corresponding housing which can lead to dislocation of the acetabulum out of the housing, thus compromising the prosthetic implantation.

  The main function of the present invention is to produce a trapezoid prosthesis

  metacarpal which eliminates the need for perfect alignment between the portion of prosthesis inserted in the metacarpus and the portion of prosthesis intended to be inserted in

the trapeze.

  Within the framework of this function, one of the aims of the present invention is to produce a trapezo-metacarpal prosthesis which allows to have a certain clearance between the portion of

  prosthesis inserted in the metacarpus and the portion of prosthesis inserted in the trapezium.

  Another object of the present invention is that of producing a trapezoidal prosthesis.

  metacarpal which allows optimal flexion of the thumb in opposition to the palm of the hand.

  Another object of the present invention is to produce a trapezoidal prosthesis.

  metacarpal which allows a mobility, as well in the rotatory direction as in a direction

  radial between the portion of prosthesis inserted into the metacarpus and the portion of prosthesis inserted

rée in the trapeze.

  Another aim, which is not the last, of the present invention is to produce a trapezo-metacarpal prosthesis which is of high reliability, of relatively low production

  easy and at competitive costs.

  This function, as well as these goals and others which will become clearer later, are

  obtained thanks to a trapezo-metacarpal prosthesis comprising a first element of-

  intended to be inserted into the metacarpus of a patient's hand, a second element intended to connect this first element to a third prosthetic element intended to be inserted into the trapezium of the patient's hand, said prosthesis being characterized in that the coupling between this second element and the first element allows a radial clearance between the

  first element and the second element.

  Other characteristics and advantages of the invention will emerge better from the description.

  description of an adopted, but not exclusive, embodiment of the prosthesis according to the invention, illustrated by way of non-limiting illustration, in the appended drawings, o: FIG. 1 is an exploded perspective view of the trapezo-metacarpal prosthesis according to the present invention;

  Figure 2 is a cross-sectional view illustrating the coupling between a pre-

  mier and a second element of the prosthesis according to the present invention;

  Figure 3 is a cross-sectional view illustrating the first and second elements.

  ment of the prosthesis according to the invention in the coupling position; Figure 4 is a perspective view of the third element of the prosthesis according to the present invention; Figure 5 is a sectional view of the substitute component of the trapezium in the event of revision. With reference to the aforementioned figures, the prosthesis according to the invention, overall

  indicated by the reference numeral 1, comprises a first element 2, of essential form-

  tapered, intended to be implanted in the metacarpus of a patient's hand. The first element 2 is purposely provided, at the end opposite to that which is intended to be inserted into the metacarpus of the patient, with a collar element 3, circular, on which is fixed an annular element 4, raised relative to on the surface of the element 3, so as to define a coupling cavity 5 for a second element of the prosthesis, indicated by the number

6.

  In detail, the second element 6 of the prosthesis, for example made of polyethylene

  lene, constitutes an intermediate coupling element between the first element 2 and a third element 7 of the prosthesis which is intended to be implanted in the trapezium of the hand

of the patient.

  By observing FIG. 1, and more particularly FIGS. 2 and 3, it is noted that the second element 6 is of essentially cylindrical shape, with a surface intended to mate

  with the third element of the prosthesis profiled in the saddle, and indicated by the reference figure

rence 8.

  FIG. 2 and FIG. 3 illustrate the coupling between the second element 6 of the prosthesis and the first element 2 and more particularly the coupling between the annular element 4 of the first element 2 and its cavity 5, with an adequate annular housing. 10

  defined on the surface of the second element 6 which is intended to mate with the element an-

  nular 4. In detail, the annular element 4 is provided with rounded edges with an inclined plane 11 which

  mates with an inclined plane 12 defined correspondingly on the side wall of the housing

ment 10 of the second element 6.

  The edge of the housing 10 has a diameter smaller than that of the annular element 4 of

  so that element 6 can be forcibly mounted on element 2.

  The housing 10 of the second element 6 has a dimension greater than that of the portion

  annular element 4 which is intended to mate in this housing.

  This allows, as shown in the illustration in Figure 3, to have a coupling

  with clearance between the second element 6 and the first element 2.

  The coupling with play, in which one can therefore have a radial movement between

  the second element 6 and the first element 2, makes it possible to avoid the need to have a supply

  perfect fit between the first prosthetic element 2 inserted in the metacarpus of the hand

  and the third prosthetic element secured to the trapezium.

  In addition, the second prosthetic element 6 can rotate 360 around

  of the annular element 4 of the first prosthetic element 2.

  This also makes it possible to improve the functions of the patient's thumb, because the prosthesis according to the invention, by allowing movement both radially between the first 2 and the third 7 element of the prosthesis, and rotary between the two, makes it possible to provide in the absence of

  mobility which is a typical drawback affecting prostheses of known type.

  In addition, the third prosthetic element 7 has, on its surface intended to mate with the saddle surface 8 of the prosthetic element 6, a profiled surface also saddle, 15, complementary to the saddle surface 8, of so as not to allow

  rotation between the second element 6 and the third element 7.

  This choice of a mating surface between the second element 6 and the third

  element 7 carried out in saddle is dictated by the fact that one thus intends to copy the natural form

  as presented by the metacarpus and the trapezius in their coupling.

  The third prosthetic element is provided, on the face opposite the face 15 s for coupling with the saddle surface 8 of the second prosthetic element 6, with a pair of

  protruding pivots 16, 17 intended to allow the coupling of the third prosthetic element

  only 7 with the trapezium of the patient's hand. By design, the third prosthetic element 7 is further provided with at least one fin 18 on which is defined at least one hole 19 for the insertion of a screw for fixing the third prosthetic element 7 to the trapezium of the hand.

of the patient.

  FIG. 5 illustrates, with a section view, the substitute component of the trapezium in

  in case of revision or when the trapezium is irreparably damaged.

  In this case, an articulation element 20, with a spherical head and an intermediate zone

  threaded is fixed to the annular element 4 of the element 2 by a hoop 21 provided with an opening

  lateral ture 22 for its introduction on the annular element 4. By tightening the hoop 21, the articulation element 20 is blocked on the element 2 thanks to a conical coupling surface 23. On the spherical head of the articulation element 20 is articulated a substitute trapezoid 24 which can rotate relative to the spherical head of element 20 and is produced

  preferably polyethylene contained in a metal shell.

  In practice, it has been found that the prosthesis according to the invention fully fulfills the fixed role because it makes it possible to obtain an optimal articulation of the thumb of the patient, namely

  between the metacarpus and trapezius of the hand, essentially reproducing the existing articulation

  so naturally between these two bones.

  The prosthesis thus designed is susceptible to numerous modifications and variants, all of which fall within the scope of the concept of the invention; furthermore all the elements of

  detail may be replaced by other technically equivalent elements.

  In practice, the materials used, provided that they are compatible with the specific use, as well as the dimensions, may be of any kind depending on the

needs and state of the art.

Claims (8)

  1. Trapezo-metacarpal prosthesis, comprising a first element (2) intended to be inserted into the metacarpus of the hand of a patient, a second element (6) intended to connect the first element to a third element (7) intended to be inserted into the trapezoid of the hand   of the patient, said prosthesis (1) being characterized in that the coupling between the   cond element (6) and the first element (2) allows a radial clearance between the first element and the second element.   2. Prosthesis according to claim 1, characterized in that the coupling between the first element and the second element allows rotation of the second element relative to the first element.   3. Prosthesis according to any one of the preceding claims, characterized by   the fact that the first element comprises a body of essentially frustoconical shape, terminated at one end by a collar (3) on which is coupled an annular element (4) defining between its lower surface and the collar a cavity (5) intended to allow the coupling of the second element.   4. Prosthesis according to any one of the preceding claims, characterized by   the fact that the second element (6) has, on its surface intended to couple with the   first element an annular housing (10) of dimensions greater than those of the door   tion of the annular element intended to engage in this housing, to allow play   radial between the first and the second element of the prosthesis.   5. Prosthesis according to any one of the preceding claims, characterized by   the fact that the second element has, on the surface opposite the mating surface   with the first element, a surface (8) profiled in the saddle.   6. Prosthesis according to any one of the preceding claims, characterized by   the fact that the third element (7) comprises a surface (15) profiled in complete saddle   of the saddle surface of the second element.   7. Prosthesis according to any one of the preceding claims, characterized by   the fact that the third element (7) has a pair of projecting pivots (16, 17) capable of engaging in the trapezoid, and at least one fin (18) provided with a hole (19) for the passage   a fixing screw to fix this third element to the trapezoid.   8. Prosthesis according to any one of the preceding claims, characterized by   the fact that the second element (6) is made of polyethylene.