FR3010304A1 - PROSTHESIS OF FINGER JOINTS, ESPECIALLY INTER-PHALANGIAN OR METACARPO-PHALANGIAN - Google Patents

Abstract

This prosthesis (1) comprises two bony pieces (2, 3) and a pin (4) connecting these bones (2, 3) pivotally. According to the invention, - one of the bone parts (2) form a cage (7) internally defining three or four planar faces (7a) forming between them reentrant angles; - the other of these bone parts (3) is secured to a pin (4) intended to be engaged through said cage (7), having a number of planar faces equal to that defined by the cage (7) , which form between them outward angles, this pin (4) being arranged in this cage (7) so that a flat face of the pin (4) is facing a re-entrant angle of the cage (7). ), and reciprocally ; and the prosthesis (1) includes a number of pieces (5) of elastically deformable material equal to the number of planar faces delimited by the cage (7) or the pin (4), fittingly taking place between a re-entrant angle of the cage (7) and a corresponding flat face of the spindle (4).

Description

The present invention relates to a finger joint prosthesis, in particular an inter-phalangeal or metacarpophalangeal prosthesis. A known interphalangeal prosthesis comprises a single piece of silicone, comprising two longitudinal extensions tapered, intended to be inserted into the medullary channels of the bones to be treated, and a central pad, intended to extend between these bones and to ensure a certain depreciation of their movements. Such a prosthesis has the advantage of not having parts in friction with each other, and return naturally to its extended position, rest, which is important since during implantation, the surgeon is frequently forced to cut the extensor tendon of the phalanx; However, it has the disadvantage of not being perfectly resistant in time, and not to allow a limitation of the articular movements of the bones, which results, being a distal interphalangeal prosthesis, a difficulty of grasping, even an impossibility of grasping.

Another type of known interphalangeal prosthesis comprises two bone pieces connected by a hinge pin, or two bony pieces connected by a ball joint, that is to say a ball head received in a corresponding spherical cavity. This type of prosthesis, made of metallic material, has an improved wear resistance but also has the drawbacks of an absence of return of the joint in its neutral position and of an absence of limitation of the articular movement. The present invention aims to remedy these drawbacks, by providing a finger joint prosthesis, in particular an inter-phalangeal or metacarpophalangeal prosthesis, which is perfectly resistant over time, which allows a perfect restitution of the natural movement of the bones. , in particular of the gripping capacity, and which is able to return itself to the neutral position in the absence of stress on the flexion joint. The prosthesis concerned comprises, in a manner known per se, two bone parts, one of which is intended to be fixed to a bone to be treated and the other is intended to be fixed to the other bone to be treated, and a pin connecting these Bone parts pivotally. According to one embodiment of the invention, - one of the bony parts form a cage defining internally three or four planar faces, these planar faces forming between them reentrant angles; the other of these bony pieces is secured to a pin intended to be engaged through said cage, having a number of plane faces equal to that defined by the cage, which form between them outward angles, this pin being disposed in this cage so that a flat face of the pin is facing a re-entrant angle of the cage, and vice versa; and the prosthesis includes a number of pieces of elastically deformable material equal to the number of planar faces delimited by the cage or the pin, these pieces of elastically deformable material being dimensioned so as to fitly fit between a re-entrant angle of the cage and a corresponding flat face of the spindle. The pivotal movement of a bone piece relative to the other bone piece, from the neutral position of alignment of the bone pieces, has the effect of moving the pin relative to the cage, and therefore to move the different flat faces of the spindle relative to those of the cage, thus simultaneously compressing the elastically deformable material pieces placed in the re-entrant angles of the cage, and thus achieving a gradual damping of the pivoting movement of the bony parts, up to a maximum pivoting position determined by the elastic limit of the material of the pieces of elastically deformable material. This progressive damping and this limitation of the bending movement make it possible to perfectly restore the natural movement of the bones of the phalanges, in particular with regard to the gripping ability found in the treated finger. When the bending stress ceases, the prosthesis according to the invention returns to its neutral position of alignment of the bone parts, as a result of the resilient return of the material of the pieces of elastically deformable material. This prosthesis also allows a slight possibility of lateral movement and / or torsion of a bone component relative to the other bone part, which is also favorable to the perfect restitution of the natural movement of the bones and the longevity of the prosthesis . This prosthesis is capable of miniaturization required, and also has a low risk of wear over time because the pieces of elastically deformable material are stressed only in compression, without friction or shear. Each piece of elastically deformable material is preferably dimensioned so as to be slightly compressed when it is inserted between the cage and the corresponding flat face of the spindle so that it can be held in this insertion position by friction. Preferably, each piece of elastically deformable material is formed by a cylinder of material, for example biocompatible silicone.

Preferably, the bone piece secured to the spindle has a stirrup-shaped portion, comprising two side walls which delimit between them a yoke, these side walls comprising holes or notches for engaging the spindle; said cage is intended to be engaged in this yoke, and the pin is intended to be attached to these side walls.

These side walls not only allow the mounting of the spindle but also close the cage laterally, at least partially, thereby protecting the pin and the parts of elastically deformable material. Fixing the pin to said side walls can be achieved by any appropriate means, including welding or crimping.

According to another embodiment of the invention: the prosthesis comprises a central part forming two cages, each cage internally defining three or four planar faces, these planar faces forming between them reentrant angles; the prosthesis comprises two pins, one of which is intended to be engaged through one of said cages and the other is intended to be engaged through the other of said cages, each pin having a number of faces planes equal to that defined by the corresponding cage, which form between them outward angles, this pin being disposed in this cage so that a flat face of the pin is facing a re-entrant angle of the cage, and Reciprocally; the prosthesis includes a number of pieces of elastically deformable material equal to the number of planar faces delimited by each cage or the spindle, these pieces of elastically deformable material being dimensioned so as to fitly fit between a re-entrant angle of the cage and a corresponding flat face of the spindle; - One of the pins is secured to one of the bone parts, and the other pin is secured to the other bone. This embodiment makes it possible, by means of the two cage-pin-piece assemblies of elastically deformable material, to obtain an increased articular deflection.

The invention will be better understood, and other features and advantages thereof will become apparent, with reference to the appended diagrammatic drawing, showing, by way of nonlimiting examples, three possible embodiments of the finger joint prosthesis. concerned.

Figure 1 is an exploded side view of the prosthesis according to a first embodiment; Figure 2 is a top view, also exploded; Figure 3 is a side view similar to Figure 1, in the mounted state; Figure 4 is a top view similar to Figure 2, in the mounted state; Figure 5 is a side view similar to Figure 3, one of the bone parts that includes this prosthesis being rotated relative to the other bone; Figure 6 is a side view similar to Figure 3, according to an alternative embodiment; Figure 7 is a top view according to this variant; Figure 8 is a side view according to a second embodiment; Figure 9 is a side view according to a third embodiment, and Figure 10 is a top view according to this third embodiment.

FIGS. 1 to 4 show a finger joint prosthesis 1, in particular an inter-phalangeal or metacarpophalangeal prosthesis, comprising two bone pieces 2, 3, a pin 4 intended to pivotally connect these pieces of bone, and four parts 5 in elastically deformable material.

The bone piece 2 is intended to be fixed to one of the bones to be treated and comprises for this purpose a tapered anchoring rod 6 intended to be inserted into the medullary canal of this bone. This rod 6 is integral with a cage 7 of square shape, open laterally, which internally delimits four flat faces 7a forming between them reentrant angles.

The bone part 3 is intended to be fixed to the other bone to be treated, and comprises for this purpose a tapered anchor rod 8 similar to the rod 6. This rod 8 is integral with a stirrup-shaped portion 9 , comprising two side walls 9a which delimit between them a clevis 10. These side walls 9a comprise notches 11 for engagement of the spindle 4.

The latter has a square cross section, so that it has four planar faces forming between them outward angles. The bone parts 2 and 3 and the pin 4 are made of a biocompatible metallic material, for example stainless steel or titanium or an alloy including titanium. Each part 5 is formed by a biocompatible silicone cylinder. As can be understood with reference to these Figures 1 to 4, the cage 7 is intended to be engaged through the yoke 10, the pin 4 is intended to be fixed to the side walls 9a so that a flat face of the pin 4 is opposite a re-entrant angle of the cage 7, and vice versa, and each part 5 is dimensioned so as to take place, in an adjusted manner, while being slightly compressed, between a re-entrant angle of the cage 7 and a corresponding flat face of the spindle 4. This slight compression allows each piece 5 to be held in its insertion position by friction.

In the embodiment shown in these Figures 1 to 4, the pin 4 takes place in the slots 11, the latter having the appropriate triangular shape, and is welded to the walls 9a. As shown in FIG. 5, from the neutral alignment position of the bone pieces 2, 3 shown in FIG. 3, the pivotal movement of one bone piece with respect to the other bone piece has the effect of to move the pin 4 relative to the cage 7, and thus to move the different planar faces of this pin 4 relative to those of the cage 7, thereby simultaneously compressing the parts 5 and thus achieving a gradual damping of the movement of pivoting of the bone parts 2, 3 to a maximum pivoting position determined by the elastic limit of the material of the parts 5. This progressive damping and this limitation of the bending movement make it possible to perfectly restore the natural movement of the bones of the phalanges, in particular as regards the grip capacity that the treated finger finds.

When the bending stress ceases, the prosthesis 1 returns to its neutral alignment position of the bone parts 2, 3, as a result of the elastic return of the material of the parts 5. This prosthesis 1 also allows a slight possibility of lateral movement and / or in torsion of a bone piece relative to the other bone part, which is also favorable to the perfect restitution of the natural movement of the bones and the longevity of the prosthesis. This prosthesis is capable of miniaturization required, and also has a low risk of wear over time because the parts 5 are stressed only in compression, without friction or shear. In the exemplary embodiment shown in FIGS. 6 and 7, the walls 9a have lengths greater than those of the walls 9 of the previous embodiment and have, in place of the notches 11, holes for receiving the pin 4, the latter being crimped into these holes.

Figure 8 shows another embodiment of the prosthesis 1, similar to the previous one, except that the cage 7 has a triangular shape, defining three flat walls 7a, and the pin 4 has a triangular cross section, forming three flat walls. Figures 9 and 10 show another embodiment of the prosthesis 1, in which the prosthesis 1 comprises a central piece 15 forming two cages 7 side-by-side as mentioned above, and two pins 4, respectively engaged through of these two cages 7. Each bone part 2, 3 comprises a stirrup-shaped part 9, and the pins 4 are respectively integral with these parts 9. The other parts or elements are found, designated by the same reference numerals. As can be seen from the foregoing, the invention provides a finger joint prosthesis, in particular an interphalangeal or metacarpophalangeal prosthesis, which provides, in comparison with homologous prostheses according to the prior art, significant advantages, mentioned above. .

The invention has been described above with reference to exemplary embodiments. It goes without saying that it is not limited to these embodiments but that it extends to all other embodiments covered by the appended claims.

Claims (5)

CLAIMS1 - Finger joint prosthesis (1), in particular inter-phalangeal or metacarpophalangeal prosthesis, comprising two bone parts (2, 3), one of which is intended to be fixed to a bone to be treated and the other is intended to to be fixed to the other bone to be treated, and a pin (4) connecting these bones (2, 3) pivotally, characterized in that: - one of the bone parts (2) forms a cage (7 ) internally delimiting three or four planar faces (7a), these planar faces forming between them reentrant angles; - the other of these bone parts (3) is secured to a pin (4) intended to be engaged through said cage (7), having a number of planar faces equal to that defined by the cage (7) , which form between them outward angles, this pin (4) being arranged in this cage (7) so that a flat face of the pin (4) is facing a re-entrant angle of the cage (7). ), and reciprocally ; and - the prosthesis (1) includes a number of parts (5) of elastically deformable material equal to the number of flat faces delimited by the cage (7) or the pin (4), these parts (5) of elastically deformable material being dimensioned in such a way as to take place, in an adjusted manner, between a re-entrant angle of the cage (7) and a corresponding flat face of the spindle (4). 2 - prosthesis (1) according to claim 1, characterized in that each piece (5) of elastically deformable material is dimensioned so as to be slightly compressed when inserted between the cage (7) and the corresponding flat face of the pin (4). 3 - prosthesis (1) according to claim 1 or claim 2, characterized in that each piece (5) of elastically deformable material is formed by a cylinder of material, for example biocompatible silicone. 4 - Prosthesis (1) according to one of claims 1 to 3, characterized in that the bone piece (3) integral with the pin (4) has a portion (9) in the form of stirrup, comprising two side walls ( 9a) which delimit between them a yoke (10), these side walls (9a) comprising holes or notches (11) for engagement of the spindle (4); said cage (7) is intended to be engaged in this yoke (10), and the pin (4) is intended to be fixed to these side walls (9a). Finger joint prosthesis (1), in particular inter-phalangeal or metacarpophalangeal prosthesis, comprising two bone pieces (2, 3), one of which is intended to be fixed to a bone to be treated and the other is intended to to be attached to the other bone to be treated, these bone parts (2, 3) being pivotally connected, characterized in that: - the prosthesis (1) comprises a central part forming two cages (7), each cage ( 7) internally delimiting three or four planar faces (7a), these planar faces forming between them reentrant angles; - The prosthesis (1) comprises two pins (4), one of which is intended to be engaged through one of said cages (7) and the other is intended to be engaged through the other of said cages (7), each pin (4) having a number of plane faces equal to that defined by the corresponding cage (7), which form outward angles between them, this pin (4) being arranged in this cage (7) of such so that a flat face of the spindle (4) is facing a re-entrant angle of the cage (7), and vice versa; the prosthesis (1) includes a number of pieces (5) of elastically deformable material equal to the number of planar faces delimited by each cage (7) or the pin (4), these pieces (5) of elastically deformable material being sized in order to take place, in an adjusted manner, between a re-entrant angle of the cage (7) and a corresponding flat face of the spindle (4); - One of the pins (4) is integral with one of the bone parts (2), and the other pin (4) is integral with the other bone part (3).