FR3001630A1 - Truncated pyramid-shaped prosthesis for replacing trapezoid bone between metacarpal bone and scaphoid of right or left hand of patient, has recesses emerging on side faces by openings occupying about specific percentage of surfaces of faces - Google Patents

Abstract

The prosthesis (1) has articular surfaces (6, 7) on distal and proximal sides of the prosthesis for cooperating with metacarpal bone and articulating with scaphoid, respectively. One of the surfaces is provided at a base wall (2), and the other surface is provided at a top wall (3) opposite to the base wall. Side faces of the prosthesis are arranged in a symmetrical manner with respect to proximal-distal axis (A). Recesses provided in each of sidewalls (4) emerge on each of the side faces by openings (8) occupying about 50-70% of surfaces of the side faces.

Description

The present invention relates to a replacement prosthesis of the trapezoid bone. It also relates to instruments for placing this prosthesis. The trapezoid bone, located between the first metacarpal and the scaphoid, and located near the trapezoid bone and the second metacarpal, has an important role in the mobility of the thumb and in the grip force that it allows to 'exercise. This trapezius bone can undergo different affections making it necessary to replace it completely. This replacement may be necessary in the first intention, by primary osteoarthritis, in particular trapezio-metacarpal, scapho-trapezoidal isolated or peritrapezian, or by inflammatory rheumatism and polyarthritis, or by a bone tumor of the trapezium, or by osteoarthritis secondary, post-traumatic, for example as a result of the treatment of a Bennett fracture. The replacement of the trapezial bone may also be necessary in second intention, that is to say in the case of surgical revisions due to various complications, for example in cases of scapho-trapezoid-trapezoidal disarthrodesis, trapezial metacarpal or inter-metacarpal, recovery after total or partial trapeziectomy, when collapse of the thumb column appears, recovery after placement of a prosthesis interposition or recovery after placement of a prosthesis total trapeziometacarpal, or after hemiarthroplasty. Of the existing prosthetic bones of trapezius, none alone can cover all the indications mentioned above. The main object of the present invention is to provide a replacement prosthesis for the trapezoid bone which alone can cover all the indications mentioned above, and which is therefore universal. Another objective of the invention is to provide a prosthesis of pseudoanatomical shape of a single size allowing an implantation indifferently on a right hand or a left hand, and having an adaptability answering any anatomical morphological situation but also any anatomical situation degraded by a pathology . In a manner known per se, the prosthesis concerned forms a first articulation surface, on a distal side intended to cooperate with the first metacarpal, and a second articulation surface on a proximal side, intended to articulate with the scaphoid. .

According to the invention, - said first and second joint surfaces are concave, and the axis running from the bottom of one of these surfaces to the bottom of the other surface is called "proximal-distal axis"; the prosthesis has a truncated pyramid shape, comprising said first articulation surface at its base wall and said second articulation surface at its top wall opposite said base wall, the four lateral faces of this prosthesis being arranged in pairs symmetrically with respect to said proximal-distal axis; the prosthesis has an internal cavity and comprises recesses in each of its lateral walls, opening on each of its lateral faces by apertures occupying between approximately 50% and 70% of the surfaces of these lateral faces. Due to its aforementioned pyramid shape and its concave articulation surfaces on its base (distal in anatomical situation) and on its side opposite to this base 15 (proximal vertex in anatomical situation), this prosthesis proves to be perfectly adapted to a replacement complete trapezoidal bone, allowing reconstitution of the thumb column, without peripheral conflict with the trapezoid bone or with the second metacarpal. The inventor has indeed been able to note that the existing anatomical implants presented a risk of rotation along their proximal-distal axis, thus generating, due to their non-symmetrical shape with respect to this axis, mechanical conflicts with the peripheral bones. These conflicts can cause instabilities, subluxations or even expulsion of the implant out of its anatomical housing. Due to its pyramidal shape, with four lateral faces separated by edges, the prosthesis according to the invention prevents this risk of peripheral conflicts by a lack of direct contact of the four faces and the four edges. In addition, the symmetrical shape of the prosthesis around the proximal-distal axis allows rotational movements of the implant around the same axis without generating conflicts. This same truncated pyramid shape, combined with the hollow structure of this prosthesis and said recesses, furthermore gives the prosthesis according to the invention a structure in essentially two end walls (those forming said articulation surfaces) and in four corner pillars delimited by the internal cavity of the prosthesis and said recesses. This structure makes it possible to give the prosthesis a very slight flexibility along said proximal-distal axis, similar to that which a natural trapezoid bone presents, making the prosthesis perfectly suitable for replacing a natural trapezium. This structure is also able to withstand the exercise of repeated efforts. The material of the prosthesis has indeed a module close to that of the bone, and is non-absorbable, inert and biocompatible, being intended to fill the trapezian box in a permanent and permanent way. As a result, the prosthesis according to the invention, while being implantable by a conventional total trapeziectomy operative technique, which is a known and well-coded proven technique, constitutes a mechanical support with more void than material, and which is rehabilitable by the patient's own tissue. This prosthesis can thus be seen as a "bio-prosthesis", allowing, after implantation, to combine at best the artificial (the prosthesis) and the natural (the soft tissues). The deep healing, biological and physiological, drowns and flows the prosthesis in the trapezian box, allowing the maintenance of the height of this trapezian box in a perennial way and stabilizing definitely this implant. If this is necessitated by the dimensions of said recesses and openings, the prosthesis may comprise an internal reinforcement. This internal reinforcement may in particular be in the form of a single oblique amount, or "X", that is to say comprising two oblique amounts crossing one another, or in the form of an axial amount unique. The wide recesses made in the four lateral walls of the prosthesis allow a fibroblastic recolonization inside the latter. The prosthesis can thus be perfectly integrated into its implantation site, being embedded in the mass of the soft tissues, which confers on it a definitive secondary stability, by bio-integration, on the contrary the existing massive implants surrounded by a hull. fibrous, which do not bind and do not interfere with surrounding tissues. These large recesses and ridges also allow, if necessary, a primary fixation by tendinous ligamentoplasty and / or capsulo-ligament suture.

In addition, the prosthesis according to the invention, by its aforementioned form, allows implantation indistinctly on left or right hands. It is simple and quick to put in place, and has a versatility making it adaptable to the anatomy of the patient and the habits of the surgeon in terms of operative technique, allowing all types of ligamentoplasties. The universal nature of the prosthesis in terms of indications makes this prosthesis a major asset in the therapeutic arsenal for treating pathologies of the trapezium and its periphery. Preferably, said lateral faces make an angle of the order of 150 with the proximal-distal axis A.

Preferably, the edges that comprise the prosthesis are rounded, both those extending between its base and top walls and its side walls than those extending between its side walls. Said concave articulation surfaces are advantageously cupuliform, that is to say in hollow sphere cap.

This form eliminates the need to shape the distal rounded end of the scaphoid. If necessary, a slight shaping of the base of the first metacarpal can be performed for perfect congruence. The relatively large diameter of said first articulation surface, on the side of the first metacarpal, makes it possible to ensure good articular stability of the prosthesis. The prosthesis may be of any suitable non-resorbable, radio-opaque, biocompatible and inert materials, and in particular polyetheretherketone (PEEK). This material proves perfectly suitable for the realization of this prosthesis, in particular to obtain the very slight flexibility mentioned above. Preferably, the walls of the prosthesis forming said first and second articular surfaces are pierced with a plurality of holes placing said internal cavity in communication with the outside of the prosthesis. These walls can thus be rehabilitated by cartilaginous stem cells and / or can receive autogenous cartilage samples. These 25 samples can be made on the basis of the first metacarpal, on the basis of the second metacarpal, on the trapezoid bone or on the trapezius bone to be replaced by the prosthesis. It should be emphasized, however, that the prosthesis according to the invention can be used with or without the provision of cartilage at its articular surfaces, this prosthesis forming, by its shape and its constituent material, sliding surfaces on its own. perfectly meeting the criteria of hemi-arthroplasties. Preferably, each of these holes is of conical shape, with its largest section opening into the articular surface formed in the wall in which this hole is arranged.

These holes are thus perfectly adapted to receiving autogenous samples of cartilage, these samples being made using the instrument described below. The instruments according to the invention intended to be used during the placement of this conical-hole prosthesis include a punch, making it possible to perform a cylindrical sample of bone cartilage and underlying cancellous bone, according to a diameter corresponding substantially to the largest diameter of a conical hole of the prosthesis. This cutter thus makes it possible to produce a filling of each abovementioned articulation surface by autologous cartilage samples inserted into said conical holes. The cancellous bone present at the bottom of these conical holes is in communication with the interior of the prosthesis and can therefore be "revitalized" by the colonization tissues. Said instruments may also include a hollow conical rasp, adapted to cut the cancellous bone of said sample in a conical shape substantially corresponding to that of said hole. This hollow conical rasp is, however, rather optional: in practice, it is very likely that the friable nature of the cancellous bone and / or the impaction of the samples in said conical holes by means of the punch allows to overcome of the use of this conical rasp. Said instruments may also include a cylindrical bell-shaped cutter, free cutting edge for releasing the first metacarpal and bottom forming a cupuliform rasp of the same shape as said first hinge surface.

The strawberry is thus engaged on the first metacarpal, which it frees progressively thanks to its sharp free edge; this engagement is continued until the cupuliform grater bottom meets the end of the first metacarpal; the pivoting of the cutter along its axis then allows to cut this end of the first metacarpal to the shape of said first articulation surface.

The invention will be better understood, and other features and advantages thereof will appear, with reference to the appended schematic drawing, showing, by way of non-limiting example, a preferred embodiment of the prosthesis concerned and three instruments. used during the placement of this prosthesis. Figure 1 is a view of the prosthesis in perspective at a first angle; Figure 2 is a perspective view at another angle; Figure 3 is a side view; Figure 4 is a view from above; Figure 5 is a view of the prosthesis after implantation; Figure 6 is a schematic and simplified view of a first instrument used during the establishment of this prosthesis; Figure 7 is a schematic and simplified view of a second instrument used in the establishment of this prosthesis; Figure 8 is a view of a cartilage sample obtained by means of said first instrument; Figure 9 a view of this sample after size by means of second instrument; and Figure 10 is a schematic and simplified view of a third instrument used in the establishment of this prosthesis. Figures 1 to 4 show, at different angles, a replacement prosthesis 1 of a trapezium bone, having a truncated pyramid shape and forming an internal cavity rendering it hollow internally. The prosthesis 1 comprises a base wall 2, of greater surface area, an apex wall 3 opposite to this base wall 2, of smaller surface area, and side walls 4. It is formed in one piece, in particular in polyetheretherketone (PEEK). The base wall 2 and the top wall 3 are solid, with the exception of a plurality of conical holes 5 pierced therethrough, which place said internal cavity in communication with the outside of the prosthesis 1. These walls 2, 3 respectively form, on the outside of the prosthesis, articular surfaces 6, 7 centered on them, which are cupuliform, that is to say in hollow sphere cap. The axis A from the bottom (or center) of one of these surfaces to the bottom (or center) of the other surface is called "proximal-distal axis". Each of the holes 5 has its largest section opening into the articular surface 6 or 7 formed in the wall 2 or 3 in which this hole is arranged. The side walls 4 are of slightly concave shape and form lateral faces which are arranged in pairs symmetrically with respect to the proximal-distal axis A, making an angle at the top of the order of 150 with the latter. . These walls 4 comprise recesses formed through them, communicating with said internal cavity and opening on each of said lateral faces by openings 8 occupying between about 60% of the surfaces of these lateral faces.

The prosthesis 1 thus has a structure in essentially two end walls 2, 3 and four corner pillars delimited by said internal cavity and said recesses. The edges extending between the different walls 2 to 4 are rounded.

Referring to Figure 5, it appears that the prosthesis 1 is intended to take place in an adjusted manner in the space left free by ablation of the native trapezium, its surface 6 coming into articulation with the base of the first metacarpal 100 and its surface 7 coming into articulation relationship with the distal end of the scaphoid 101, thus ensuring a perfect reconstruction of the thumb column. Because of its pyramid shape, the prosthesis 1 does not come into peripheral conflict with the trapezoidal bone 102 nor with the second metacarpal 103, and has good stability with respect to a risk of rotation along its proximal-distal axis. AT; thanks to its symmetrical shape with respect to this axis A, a possible rotation of this prosthesis prior to its fibroblastic recolonization does not generate mechanical conflicts with the peripheral bones 102 and 103. The structure in essentially two end walls 2, 3 and in four corner pillars also gives the prosthesis 1 a very slight flexibility along the axis A, similar to that presented by a natural trapezoid bone, making this prosthesis perfectly suitable for replacing a natural trapezium. This structure is also able to withstand the exercise of repeated efforts. The wide recesses in the side walls 4 allow fibroblastic recolonization inside the prosthesis, which can be perfectly integrated into its implantation site, being embedded in the soft tissue mass. These large recesses also allow, if necessary, a primary fixation by tendinous ligament and / or capsulo-ligament suture. In addition, the prosthesis 1, by its aforementioned form, allows implantation indistinctly on left or right hands. It is simple and quick to put in place, and has a versatility making it adaptable to the anatomy of the patient and the habits of the surgeon in terms of operative technique.

FIG. 6 shows a punch 10 and FIG. 7 shows a hollow conical rasp 20 that can be used during the placement of the prosthesis 1, to perform bone samples 30 as visible in FIGS. 8 and 9, intended to The punch 10 essentially comprises a tubular body 11, a cylindrical sampling bell 12 and an ejector 13 of the sample 30.

The bell 12 has a diameter substantially corresponding to the largest diameter of a hole 5; it slides in the body 11, being guided by a centering sleeve 14, and is actuated by a rod 12a. It includes a sharp free edge, cutting the cartilaginous cortex.

The ejector 13 has a transverse ejection wall of the sample 30, connected to an actuating rod 13a, this rod 13a extending, in the example shown, inside the rod 12a. The punch 10 makes it possible to perform a sample 30 including a portion of cortical cartilaginosa 30a and a portion of underlying cancellous bone 30b, this sample 30 having, in the raw state, the cylindrical shape visible in FIG. 8. The rasp 20 has a hollow tapered head 21, with internal grating asperities, and a handle 22 integral with the head 21, connected to a handle for actuating the head 21 in rotation. The grater 20 enables the rough sample 30 to be cut in the conical shape shown in FIG. 9, this shape making it possible to insert the sample 30 into a hole 5. FIG. 10 shows an instrument 40 comprising a cylindrical bell mill 41, a handle 42 and a handle 43 for actuating the milling cutter 41 in rotation. The cutter 41 is dimensioned so as to be engaged around the base of the first metacarpal and comprises a sharp free edge 44 for releasing this base. It also comprises a cupuliform bottom 45 of the same shape as the articulation surface 4, with asperities forming a rasp. The cutter 41 is thus engaged around the base of the first metacarpal 103, which it releases progressively thanks to its free cutting edge 44, serrated; this commitment is continued until the bottom 45 meets the end of this first metacarpal, then the strawberry 41 is; pivoted several times along its axis to cut this end to the shape of the hinge surface 4. As apparent from the above, the invention provides a replacement prosthesis of a trapezoid bone, having, compared to homologous prostheses 30 according to the prior art, significant advantages, mentioned above. The invention has been described above with reference to an embodiment provided by way of example. It goes without saying that it is not limited to this embodiment but that it extends to all other embodiments covered by the appended claims.

Claims (8)

CLAIMS1 - Prosthesis (1) for replacing the trapezius bone, forming a first articulation surface (6) on a distal side intended to cooperate with the first metacarpal (100), and a second articulation surface (7). ) on a proximal side, intended to articulate with the scaphoid (101), characterized in that: - said first and second surfaces of joints (6, 7) are concave, and the axis (A) from the bottom one of these surfaces at the bottom of the other surface is called "proximal-distal axis"; the prosthesis (1) has a truncated pyramidal shape, comprising said first articulation surface (6) at its base wall (2) and said second articulation surface (7) at its top wall (3) opposite said base wall (2), the four side faces of said prosthesis (1) being arranged in pairs symmetrically with respect to said proximal-distal axis (A); - The prosthesis (1) has an internal cavity and comprises recesses in each of its side walls (4), opening on each of its lateral faces by openings (8) occupying between about 50% and 70% of the surfaces of these side faces. 2- prosthesis (1) according to claim 1, characterized in that said side faces make an angle of the order of 15 ° with the proximo-distal axis (A). 3- prosthesis (1) according to claim 1 or claim 2, characterized in that it comprises an internal reinforcement, in particular in the form of a single oblique amount, or "X", that is to say comprising two oblique amounts crossing one another, or in the form of a single axial amount. 4- Prosthesis (1) according to one of claims 1 to 3, characterized in that the edges it comprises are rounded, both those extending between its base walls (2) and vertex (3) and its side walls (4) than those extending between its side walls (4). 5. Prosthesis (1) according to one of claims 1 to 4, characterized in that said concave articulation surfaces (6, 7) are cupuliform, that is to say in hollow sphere cap. 6- prosthesis (1) according to one of claims 1 to 5, characterized in that it is polyetheretherketone. 7- prosthesis (1) according to one of claims 1 to 6, characterized in that its walls (2, 3) forming said first and second articular surfaces are pierced with a plurality of holes (5) communicating said cavity internal with the outside of the prosthesis (1). 8- prosthesis (1) according to claim 7, characterized in that each of said holes (5) is conically shaped, the largest section of a hole opening into the articular surface (6, 7) formed in the wall (2 , 3) in which this hole is arranged.