Assembly comprising an implantable part designed to be fastened to one or more bones or bone portions to be joined, and at least one screw for fastening the implantable part to said bone(s)

Abstract

An assembly including an implantable part designed to be fastened to at least one bone or bone portions to be joined and at least one screw for fastening the implantable part to the at least one bone or bone portions. The implantable part includes at least one tapped hole and the screw includes a head designed to be engaged in the tapped hole. The tapped hole is cylindrical and includes at least one radial notch emerging in a surface of the implantable part through which the screw is designed to be engaged in the tapped hole. The radial notch produces an interruption in the tapping included by the tapped hole. The head of the screw is conical, with an apical angle of between 15 and 25°.

Claims

1. An assembly comprising: an implantable part configured to attach to at least one bone or bone portions to be joined, the implantable part includes a first face directly contacting the at least one bone or bone portion when said implantable part is implanted, a second face being opposed to the first face, and at least one tapped hole, each tapped hole extending through an entire thickness of the implantable part connecting the first face and the second face; at least one screw for fastening the implantable part to the at least one bone or bone portions, and each screw of the at least one screw includes a head designed to be engaged in one of said tapped hole; wherein: each tapped hole is cylindrical, internally threaded, and includes a plurality of notches, each notch of the plurality of notches extending through an entire thickness of the tapped hole from the first face to the second face of the implantable part, each notch of the plurality of notches emerging in a surface of the tapped hole; said plurality of notches produce an interruption in the internal thread of the tapped hole; the head of the at least one screw forms a main peripheral surface which is conical, with an apical angle comprised between 15 and 25°; said main peripheral surface of the head is externally threaded with a pitch that is between one third and one half of a pitch of the internal thread of the tapped hole, and a depth of the external thread of said main peripheral surface of the head includes between one half and two thirds of a depth of the thread of the tapped hole; each tapped hole of the at least one tapped hole includes a circumference with a first section and a second section opposite to the first section and in the vicinity of 180 degrees, said first section of the circumference of each tapped hole includes the plurality of notches, said second section of the circumference of the tapped hole is free of the plurality of notches.

2. The assembly according to claim 1, wherein said apical angle is 20°.

3. The assembly according to claim 1, wherein the pitch of the thread of the head of the at least one screw is substantially one half of the pitch of the thread of the tapping of the tapped hole.

4. The assembly according to claim 1, wherein said at least one screw comprises a body and a bone screw thread extends along that body substantially to said head of said at least one screw, such that a proximal end of said external thread of the main peripheral surface of the head of said at least one screw is situated inside said tapped hole, when the screw is in place on the implantable part.

5. The assembly according to claim 1, wherein said implantable part is a fastening base for fastening part of a joint prosthesis to a bona the at least one bone or bone portions.

6. The assembly according to claim 1, wherein said implantable part is a fastening base for fastening to a glenoid to shoulder blade in a total shoulder prosthesis.

7. The assembly according to claim 1, wherein said implantable part is a cortical plate, a superior humeral cortical plate, or an inferior radius cortical plate.

8. An assembly comprising: an implantable part configured to attach to at least one bone or bone portions to be joined, the implantable part includes a first face directly contacting the at least one bone or bone portion when said implantable part is implanted, a second face being opposed to the first face, and at least one tapped hole, each tapped hole extending through an entire thickness of the implantable part connecting the first face and the second face; a central anchor lug placed on the implantable part, the central anchor lug having an axis; at least one screw for fastening the implantable part to the at least one bone or bone portions, and each screw of the at least one screw includes a head designed to be engaged in one of said tapped hole; wherein: the tapped holes are distributed around the central anchor lug and each tapped hole includes an axis; the axis of the tapped holes is not parallel to the axis of the central anchor lug; each tapped hole is cylindrical, internally threaded, and includes a plurality of notches, each notch of the plurality of notches extending through an entire thickness of the tapped hole from the first face to the second face of the implantable part, each notch of the plurality of notches emerging in a surface of the tapped hole; said plurality of notches produces an interruption in the internal thread of the tapped hole; the head of the at least one screw forms a main peripheral surface which is conical, with an apical angle comprised between 15 and 25°; said main peripheral surface of the head is externally threaded with a pitch that is between one third and one half of a pitch of the internal thread of the tapped hole, and a depth of the external thread of said main peripheral surface of the head includes between one half and two thirds of a depth of the thread of the tapped hole; each tapped hole includes a circumference with a first section and a second section opposite to the first section and in the vicinity of 180 degrees, said first section of the circumference of each tapped hole includes the plurality of notches, said second section of the circumference of the tapped hole is free of the plurality of notches.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be well understood, and other features and advantages thereof will appear, in reference to the appended diagrammatic drawing, showing, as non-limiting examples, several possible embodiments of the implantable part-screw assembly to which it pertains.

(2) FIG. 1 is a perspective view of the plate comprising a series of holes in which anchor screws for anchoring that plate are designed to be received;

(3) FIG. 2 is an enlarged perspective view of one of the holes;

(4) FIG. 3 is a front view of the hole;

(5) FIG. 4 is a side view of a screw;

(6) FIG. 5 is an enlarged perspective view of the head of said screw;

(7) FIG. 6 is an enlarged side view of said head;

(8) FIGS. 7 to 9 are partial cross-sectional views of the plate and the screw, during three successive phases of placing the screw in the hole;

(9) FIG. 10 is a developed view of the hole, with a diagrammatic indication of the position of the turn of the thread of the screw according to three angulations, showing an absence of screw thread jump;

(10) FIG. 11 is a front cross-sectional view of part of a shoulder blade in which a base for receiving a glenoid has been implanted;

(11) FIG. 12 is a sagittal view of the portion of the shoulder blade, along the axis of said base;

(12) FIGS. 13 to 18 are front views of six possible embodiments of a hole comprised by the implantable part according to the invention;

(13) FIGS. 19 and 20 are sagittal and anterior views, respectively, of the upper portion of the humerus on which a plate according to the invention has been placed;

(14) FIG. 21 is a top view of a plate for the lower end of the radius, and

(15) FIGS. 22 and 23 are top and side views, respectively, of said plate, after placement on a radius.

DETAILED DESCRIPTION OF THE EMBODIMENT OF THE INVENTION

(16) FIG. 1 shows an assembly 1 comprising an implantable part 2 designed to be fastened to one or more bones or bone portions to be joined, and several screws 3 for fastening said implantable part 2 to said bone(s).

(17) For the purposes of a purely diagrammatic illustration, the implantable part 2 has been shown in FIG. 1 as a rectangular plate with any shape whatsoever. FIGS. 11 and 12 show that this implantable part may be a base 2 for fastening a glenoid to a shoulder blade 100 or a part forming a convex joint surface called “metaglene” or “glenosphere” (not shown); this implantable part may also be a humeral cortical plate 2 (cf. FIGS. 19 and 20) or cortical plate for the lower end of the radius (cf. FIGS. 21 to 23).

(18) The plate 2 shown in FIG. 1 comprises a plurality of aligned holes 4, each of which is designed to receive a screw 3.

(19) As shown more particularly in FIGS. 2 and 3, each hole 4 is cylindrical and tapped, and comprises six notches 5 extending radially, regularly distributed around its circumference. These notches 5 extend over the entire thickness of the plate 2 and consequently interrupt the screw pitch of the tapping of the hole 4 over the entire height thereof. They are substantially U-shaped, i.e. each one forms two radial surfaces opposite one another and a rounded bottom connecting those two surfaces.

(20) In reference to FIGS. 4 to 6, it appears that the screw 3 comprises a conical and threaded head 3a, and a body 3b provided with a screw thread 3c adapted for bearing in a bone.

(21) The apical angle of the cone defining the head 3a is 20° (cf. FIG. 6). The pitch of the screw thread of that head 3a is in the vicinity of one third of the pitch of the tapping of a hole 4, and the depth of the screw thread is in the vicinity of one half that of the pitch of the tapping of a hole 4.

(22) The screw thread 3d of the head 3a is symmetrical, has flanks that may be inclined between 45° and 75°, and has an identical depth over the entire length of the head. The screw thread may be a dual entry screw thread.

(23) The bone screw thread 3c comprised by the body 3b of the screw extends along said body into the immediate vicinity of the head 3a, and is interrupted immediately below that head 3a.

(24) Each screw 3 is designed to be engaged in a hole 4 and to be screwed in the bone(s) to which the plate 2 is designed to be fastened. The screws 3 may be engaged in the holes 4 perpendicular to the plate 2, as shown by FIG. 1, or maybe placed in said holes 4 not perpendicular to the plate 2, as appears in FIGS. 7 to 9.

(25) This possibility for the angulation of the screw 3, and therefore of a plurality of possible implantation directions of that screw, results (i) from the presence of the notches 5, which locally interrupt the tapping of the hole 4 and allow a slight deformation of the part 2 at that hole 4, (ii) the aforementioned conical shape of the head 3a, and (iii) the absence of narrow engagement of the respective screw threads of the head 3a of the screw 3 and the hole 4 during the first part of the screwing phase, i.e. substantially at the position of the screw 3 shown in FIG. 8.

(26) From this position, and in a second portion of the screwing phase going as far as the end of screwing position shown in FIG. 9, progressive and effective jamming of the head 3a occurs in the hole 4, of a nature to oppose any risk of unscrewing of the screw 3. This jamming results from (i) said possibility of slight deformation allowed by the notches 5, and (ii) the aforementioned conical shape of the head 3a, which allows the gradual interlocking of the respective threads of the head 3a and the hole 4 during said second portion of the screwing phase, and which performs the complete interlocking at the end of screwing.

(27) It will also be understood in reference to FIG. 9 that the portion of the first turn of the bone screw thread 3c can be located, in that end-of-screwing position, inside the hole 4, thus contributing to the jamming of the screw 3 in said hole 4.

(28) FIG. 10 shows the development of the hole 4 with three lines 10, 11, 12 each representing the development of a turn of the screw thread 3d of the head 3a, for respective angulations of the screw 3 of 0°, 6° and 12°. It shows that there is no screw thread jump.

(29) In reference to FIGS. 11 and 12, it appears that the aforementioned base 2 comprises a central anchor lug 15 and four holes 4 distributed around said lug 15, designed to receive screws 3 (only two of the four screws 4 are placed on the illustrated base 2, for which placement is in progress).

(30) It appears that the axes of the holes 4 are not parallel to the axis of the lug 15, but rather inclined in relation to the axis, by 10° in the illustrated example. This angulation of the holes 4 is thus added to the angulation of the screws 3 made possible by those holes, so as to allow a significant angulation of the screws 3 in relation to a reference plane perpendicular to the axis of the lug 15. In the illustrated example, the total angulation of the lower screw 3 is 20° (10° angulation of the hole 4 in relation to said axis, and 10° angulation of the screw 3 in the hole 4). Owing to this possibility of significant angulation, the upper screw 3 and the lower screw 3 can be oriented optimally for anchoring respectively in the pillar 101 of the coracoid and the pillar 102 of the shoulder blade.

(31) FIGS. 13 to 16 show holes 4 having shapes and numbers of notches 5 different from those described above. The hole 4 shown in FIG. 13 comprises notches identical to those described above, but comprises eight instead of six. The hole 4 shown in FIG. 14 comprises only four notches 5, also U-shaped, but much wider than those described above. The hole 4 shown in FIG. 15 comprises six notches 5 with a half-circle section. The hole 4 shown in FIG. 16 comprises eight such notches 5 with a half-circle section.

(32) The hole 4 shown in FIG. 17 comprises five notches 5 regularly arranged on a first sector in the vicinity of 240° and is provided without notches on a second sector in the vicinity of 120°. Similarly, the hole 4 shown in FIG. 18 comprises four notches 5 regularly arranged on the first sector in the vicinity of 180° and is provided without notches on the second sector in the vicinity of 180°. The absence of notches 5 on said second sectors amounts to a rigidity of the implantable part 2 and continuity of the screw thread of the tapping of the hole 4 at said second sectors, which results in an impossibility of orienting the screw 3 on the sides of the holes 4 opposite those on which said second sectors are located.

(33) Implantable parts 2 may thus be designed whereof the risk of defective implantation of a screw 3 is eliminated.

(34) Thus, in reference to FIG. 19, it appears that a humeral plate 2 may comprise, in the epiphyseal portion thereof, two side-by-side holes 4 whereof the sectors facing the side opposite the epiphyseal end of said plate 2 are provided without notches. Then, an excessive orientation of the screws 3 toward the epiphyseal cortical bone of the humeral head 103 is prevented, as shown in FIG. 20, which avoids the risk of said screws 3 emerging on the joint surface of the humerus. The third hole 4 comprised by said epiphyseal portion also has a sector provided without notches on the side of that hole opposite the epiphyseal end of the plate 2; said sector thus prevents the orientation of the screw 3 engaged in that hole toward the humeral diaphysis. However, the possibility remains of choosing the implantation direction of the screws 3 in the other directions mentioned above.

(35) FIG. 21 shows a plate 2 for a lower end of the radius, traditionally having a widened distal portion 2a. In that distal portion 2a, a proximal series 21 of four holes 4 and a distal series 22 of three holes 4 are arranged transversely. The holes 4 of the proximal series 21 each comprise six notches as described above, allowing a multidirectional orientation of the screws 3. Each hole 4 of the distal series 22 comprises a first sector having four notches 5, turned toward the distal end of the plate 2, and a second sector provided without notches, situated on the side of the hole 4 turned toward the side of said proximal series 21.

(36) As will be understood in reference to FIGS. 22 and 23, the screws 3 engaged in the holes 4 of the distal series 22 may not be oriented toward the distal end of the radius 104, which prevents any risk of said screws 3 emerging at the joint surfaces comprised by said radius 104.

(37) It appears from the preceding that the invention provides an assembly 1 including an implantable part 2 and at least one screw 3, having the decisive advantages of making it possible to engage the screw 3 in a hole 4 of the part 2 in a plurality of implantation directions, and of achieving, at the end of screwing, effective jamming of the head 3a of the screw in the hole 4, of a nature to oppose any risk of unscrewing. Another decisive advantage of this assembly 1 is making it possible to eliminate the risk of defective positioning of the screw 3.

(38) The assembly 1 according to the invention can be used on all anatomies other than those previously mentioned, such as femur, tibia, elbow or foot, and works irrespective of the material used, for example stainless steel or titanium.

(39) The invention was described above in reference to embodiments provided as examples. It is of course not limited to these embodiments, but on the contrary encompasses all other embodiments covered by the appended claims. In particular, the base 2 shown in FIGS. 11 and 12 can comprise middle holes 4 (i.e. the two holes 4 other than the upper hole and the lower hole visible in FIG. 12) provided without notches 5 on the sectors thereof turned toward the outside of the base 2, thereby prohibiting the screws from being oriented in implantation directions that risk causing those screws to emerge outside the bone.