Osteosynthesis screw comprising an angular index in relation to the screwdriver

Abstract

A tightening screw for osteosynthesis, including a screw thread that is arranged along a main axis, and including, at its distal end, a recess that has regular shapes about the main axis which are distributed angularly and are suitable for receiving complementary shapes of a screwdriver engaging therewith; the rear face of the screw is inclined in relation to a transverse plane of the screw, the screw being characterized in that the recess in the screw includes at least one specific shape that is different from the other, regular shapes.

Claims

1. A tightening screw for osteosynthesis comprising: a thread disposed along a main axis; a rear end having an inclination with respect to a transverse plane of the screw; and a hollow in the rear end, the hollow having: a plurality of radially distributed identical lobes disposed on a crown centered on the main axis and disposed between an internal circle with a smaller radius and an external circle with a larger radius; and at least one particular shape which has a design different from a design of the plurality of lobes, the plurality of lobes and the at least one particular shape being adapted to receive complementary shapes of a screwdriver fitting thereupon.

2. The tightening screw according to claim 1, wherein the plurality of lobes includes five lobes.

3. The tightening screw according to claim 1, wherein the particular shape covers an angular sector about the axis equivalent to that of one of the plurality of lobes.

4. The tightening screw according to claim 1, wherein the plurality of lobes include a first circular arc centered on the axis, then a second circular arc projecting outwardly with respect to the first circular arc.

5. The tightening screw according to claim 1, wherein the particular shape has a constant radius which is centered on the axis.

6. The tightening screw according to claim 1, wherein the hollow includes a generally cylindrical shape disposed parallel to the axis, comprising a slightly conical portion.

7. The tightening screw according to claim 1, wherein its thread extends over an entire length of the screw, and has a larger diameter at a rear side of this screw.

8. The tightening screw according to claim 1, wherein it includes a front thread extending over a front portion of a length of the screw, and a head thread disposed at a rear of the screw, separated from the front thread, having a larger diameter than the front thread.

9. A screwdriver provided to tighten screws according to claim 1 including at a front a tip having shapes complementary with those of the hollow enabling fitting thereupon, including a visual angular marker, wherein the tip includes a generally cylindrical shape disposed parallel to the axis, comprising a slightly conical portion.

Description

(1) Other features and advantages of the invention will appear on reading the following description, provided only as example, with reference to the following appended figures:

(2) FIGS. 1a, 1b and 1c have successively on a foot in top view, three steps of a surgery for reducing a hallux valgus of the big toe;

(3) FIG. 2 is a side view of this foot after the procedure;

(4) FIG. 3 shows a screw according to the invention used for this procedure;

(5) FIG. 4 is an external view of the foot after the insertion of the screw;

(6) FIG. 5 is an overview of the bones of the foot showing the insertion of the screw on the metatarsus;

(7) FIG. 6 is a rear view of the screw showing its drive imprint;

(8) FIG. 7 shows a screwdriver provided for this screw; and

(9) FIG. 8 shows a screw according to one variant.

(10) For more clarity, identical or similar elements are marked with identical reference signs on all the figures.

(11) FIG. 1a shows a foot including successively forwards of the big toe, a metatarsus 2, a proximal phalanx 4 and a distal phalanx 6.

(12) The internal side of the foot is that facing the axis of the body. The metatarsus 2 has an abnormal inward inclination, and the proximal phalanx 4 has an abnormal outward inclination.

(13) The first step of the surgery provides for a cut 8 of the metatarsus 2 at the front portion thereof, formed at a slant, and a double cut 10 of the proximal phalanx 4 at the rear portion thereof in order to remove a portion of the bone forming a corner.

(14) FIG. 1b shows the displacement of the front portion of the metatarsus 2 outwardly relative to the rear portion, and a recovery of the proximal phalanx 4 inwardly by having removed the portion of the bone forming the corner. A substantially alignment along the axis of the foot, the metatarsus 2 and the proximal phalanx 4 thus modified is obtained.

(15) FIG. 1c and FIG. 2 show the insertion of a first tightening screw 20 into the two portions of the metatarsus 2 and of a second screw into the two portions of the proximal phalanx 4, each time to fix together these two portions.

(16) Each tightening screw 20 comes into the internal side of the foot from the rear, after having made a minimum incision on the tissues disposed in the axis A of the screw.

(17) FIG. 3 shows a screw 20 including a tapping 22 over its entire length, comprising a diameter which increases gradually at a rear portion. The front end of the screw 20 ends in a shape 24 ensuring the formation of the tapping in the bone portions.

(18) The planar rear end face 28 of the screw 20 has an inclination with respect to a transverse plane of the screw, forming a bevel which may be of 45°. This end face 28 includes an axially directed hollow imprint, centered on the axis of the screw A, provided to receive a shape complementary with a screwdriver in order to drive it in rotation.

(19) Alternatively, the screw may be a compression screw including a front tapping extending over a front portion of its length, then a smooth portion, and finally a head tapping disposed at the rear of this screw, having a larger diameter than the front tapping.

(20) FIGS. 4 and 5 have a small incision 30 formed on the internal side of the foot, enabling fitting of the tools to cut the tissues and insert a screw 20 on the metatarsus 2. Other incisions enable cutting of the bones 2, 4, and the insertion of the second screw 20. In this way, a minimum of trauma on the tissues is achieved.

(21) At the end of tightening of the screws 20, the angular position of each screw is adjusted so as to substantially align its beveled rear face 28 on the external surface of the bone, in order to ensure minimum stress or trauma to the surrounding tissues.

(22) FIG. 6 shows the hollow imprint 40 formed on the rear face 28 of the screw 20, constituting a cylinder parallel to the axis of the screw A, comprising a succession of five identical shapes which consist of regular lobes 42 disposed on a crown centered on the axis, comprised between an internal circle with a small radius R1 and an external circle with a large radius R2.

(23) Each of the five lobes 42 of the recess of the imprint 40 disposed at an angle of 60° with respect to the center O, successively includes a concave radius Re then a convex radius Ri. An angle of 60° includes a particular circular arc shape 44, devoid of any lobe, which follows the internal circle with a small radius R1.

(24) The star-shaped imprint 40 may in particular replicate an imprint known under the trade name <<Torx>>, with one lobe less.

(25) FIG. 7 shows a screwdriver 50 including, at the front of a metal cylindrical rod 54, a tip 52 constituting a cylinder centered on the axis, provided to fit with a minimum clearance in the imprint 40 of the rear face 28 of the screw 20.

(26) In particular, the front tip 52 includes a succession of five shapes constituting regular lobes, each extending at an angle of 60°. Over the remaining 60°, we have a circular portion devoid of any lobe, which follows the internal circle with a radius R1.

(27) A unique positioning of the screw 20 on the screwdriver 50 is obtained, which is provided by the adjustment of the two circular portions on one another. For the initial mounting of the screw 20 on the screwdriver 50, or after beginning the insertion if the surgeon disengages the screwdriver off the screw and then want to put it back, the unique angular positioning is necessarily obtained.

(28) In particular, the imprint 40 of the screw 20 or the front tip 52 of the screwdriver 50 may include on some lobes a slightly conical shape opening at the rear of the screw or closing at the front of the screwdriver, in order to ensure after an axial thrust, a holding of the screw on the screwdriver, as disclosed in the document of the prior art mentioned hereinabove.

(29) The screwdriver 50 includes at the rear a connection area for a handle 56, having a front face 58 forming a bevel inclined at 45°, disposed parallel to the beveled rear face 28 of the screw 20 when it is fixed on the screwdriver. In this way, the surgeon visualizes directly by looking at the handle the angular position of the beveled rear face 28 of the screw 20.

(30) FIG. 8 alternatively has an imprint 40 formed on the rear face 28 of the screw 20, constituting a cylinder parallel to the axis of the screw A, comprising a succession of five identical regular shapes each covering an angle of 60°, comprised between the circles centered on the axis A, with the small radius R1 and the large radius R2.

(31) Each regular shape includes a circular arc that follows the small radius R1, then a lobe 42 formed by a circular arc with a convex radius Re turned, which extends up to the external circle with a large radius R2.

(32) One of the lobes is absent leaving instead over a 60° angle a particular shape in form of a circular arc 44 which follows the internal circle with a small radius R1.

(33) A method for manufacturing the imprint 40 of the screw 20, simple to implement, includes a succession of five drillings to form the lobes 42, then a milling centered on the axis along the small radius R1, to complete the cylindrical shape of this imprint.

(34) The screw 20 according to the invention as well as the specific screwdriver 50 ensure to the surgeon easiness, safety and speed in the execution of surgeries using this type of screw.

(35) Alternatively, the imprint 40 of the screw 20 may have other shapes. In particular, standardized shapes can be used, such as a hexagonal shape which is easier to make but has a reduced torque transmitting capacity.