FR2971138A1 - Self-compressive surgical implant bone screw for reduction of non-displaced fractures of bone segments during osteosynthesis, has fixtures succeeding one another at minimum frequency, and distal end provided with autoperforator arrangement - Google Patents

Abstract

The present invention relates to a surgical implant of the self-compressive osteosynthesis screw type such that the compression is caused by a thread with an asymmetric profile of variable angle and which varies continuously over its entire length. The present invention comprises on the one hand a conical body of revolution (1) which comprises at its periphery a thread (2), on the other hand a cylindrical part, or compression head (3), located at the proximal end ( 22) of the body (1) and equipped with a rotational drive member (4). The thread (2) has an asymmetrical profile formed of alternately concave / convex surfaces, the angle of which increases continuously from the distal end (21) to the proximal end (22), thus ensuring increasing compression in both the longitudinal direction only in the radial direction. The screw is provided with self-tapping arrangements (7) and its distal end (21) is provided with a self-piercing arrangement (10). The present invention is intended for the surgical field, in particular for the reduction of non-displaced fractures of small bone fragments.

Description

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OSTEOSYNTHESIS PROSTHESIS FOR REDUCING NON-MOVING FRACTURES

The present invention relates to a surgical screw type osteosynthesis implant for the reduction of non-displaced fractures of small bone fragments. More specifically, it is a self-compressive screw such that the compression is caused by an asymmetrical profile thread whose ridge angle varies continuously over its entire length.

Fracture reduction involving small bone fragments has long been the subject of screw developments to improve bone fusion. Many models have been developed and each has its own qualities and disadvantages. The first screws for approximating and compressing two bone fragments had a distal portion provided with a "wood screw" thread, followed by a smooth portion without a thread and a larger proximal head to provide compression. These screws do not play their role when the fracture profile is not properly positioned relative to the thread and do not ensure good stability between the fragments. They also have the major disadvantage of having no progressivity in the compression and the result depends directly on the good bone quality. Another type of screw is the screw type of Herbert. These screws are provided with a threaded distal portion, followed by a smooth cylindrical portion of smaller diameter, then a third proximal portion, which may be sometimes conical, and which is also provided with a thread, whose thread pitch is generally smaller than that of the distal portion. The screws described in patents FR2760628A1 (BIOTECH), FR2787989A1 (DEPUY), FR2841764A1 (NEWDEAL), FR2941859A1 (MEMOMETAL) belong to this category. Most of these screws require the use of a drill to make a pilot hole, which weakens bone capital and promotes the risk of instability before consolidation. In addition, the compression mechanism, as in the previous ones, only works if the fracture profile is well located between the threads. Regardless of the shape of the proximal portion, conical or not, and whatever the difference in thread pitch between the proximal portion and the distal portion, the compressive force depends on the number of turns of the screw made as soon as the head 2971138 - 2

proximal comes into contact with the bone. The practitioner must evaluate the tightening torque needed to obtain a sufficient compression force without the risk of destroying the bone around the nets. Any evaluation error therefore results in the loss of compressive and stability effort, which is the opposite of the desired effect. Another disadvantage is that the heads of these screws on the proximal portion have only a few flutes and the clamping force can be obtained if the bone on which they rely is of good quality. It is therefore impossible to obtain a compression of the fragments if the cortical bone is not sufficiently solid or if it is cracked. Furthermore, the presence of a smooth intermediate portion of small diameter promotes undesirable bone colonization, likely to prevent any subsequent removal of the screw, or cause bone removal in case of forced withdrawal. A type of screw with two threads of the same axis of revolution is also known, patents FR2855391A1 (RENARD), FR2916624A1 (SBI), WO9300518A1 (MATHYS), in which the compression force is caused by both the difference of pitch and the difference in height and / or diameter between the two threads. These materials require the drilling of a pilot hole to accommodate a cylindrical thread profile metric type. This type of profile does not provide good grip in the cancellous bone and the absence of screw head makes non-existent a final compression. It is therefore impossible for the practitioner to estimate the moment when the compression is optimum, at the risk of losing any compression if the screw makes a revolution too much by deteriorating the bone around. There is also known a type of thread with continuous thread, the thread pitch may vary or not, in the patents FR2932975A1 (FH), WO9416636A1 (HUEBNER).

These screws also require pre-drilling which tends to destabilize the fracture site. In addition, they have a constant net profile and the evolution of the pitch is harmful to the attachment in the bone, in that the threads of the proximal portion deteriorate the passage made by the nets of the disc portion. In addition, these screws are arranged with a more or less conical proximal portion and the proximal end has aggressive edges that prohibit their use in front of a joint; moreover, outside a joint, angular edges can cause pain and discomfort for the patient. 2971138 -3

Consequently, existing screws are not entirely satisfactory as regards the osteosynthesis of small bone fragments and the present invention aims to remedy these disadvantages.

The technical problem underlying the invention is therefore the production of a self-compressive and totally atraumatic osteosynthesis screw during the application, intended for the reduction of fractures and more especially those of small bone fragments, of manipulation. simple and easy during the establishment by the practitioner, while ensuring perfect bone consolidation without pain or discomfort for the patient, and allowing a possible extraction without causing damage to the bone.

The object of the present invention is to provide a self-compressive osteosynthesis screw, the structure of which gives it the characteristic of being atraumatic, in that the placement causes a minimal deterioration of the bone. Consecutively, another aim is to confer on the present invention the faculty of being implanted percutaneously.

The invention is hereinafter described with reference to the accompanying drawings in which:

Figure 1 shows a general view of an embodiment of the invention. FIG. 2 shows a view of the proximal portion of the invention and a possible embodiment of the drive member. FIG. 3 is a side view of an embodiment of the invention which illustrates the continuous variation of FIG. 4 is a view of the distal portion of the invention and a possible embodiment of the self-piercing arrangement. FIG. 5 is a sectional view of the invention. which illustrates a possible embodiment of the axial recess

For this purpose, the present invention relates to an osteosynthesis screw characterized in that it consists on the one hand of a conical body of revolution (1) which

has at its periphery a protruding part in a helix, or thread (2), on the other hand a cylindrical part, or compression head (3), located at the proximal end (22) of the body (1) and of diameter equal to the largest diameter of the protruding part of the helix, which compression head (3) is equipped with a drive member (4) rotated about its axis of revolution, the thread (2) comprising an axial guide surface (5) of the body (1) and an axial bearing surface (6) of the body (1) on the bone, characterized in that said surfaces form between them on the periphery of the body (1) an acute angle (alpha) which progressively increases from the distal end (21) to the proximal end (22): distal alpha <proximal alpha, thus achieving an asymmetric profile whose angle increases continuously from the end distal (21) to the proximal end (22) preferably in an amount of between 5% and 6.8%, and thus increasing compression, both in the longitudinal direction and in the radial direction, during the penetration of said screw, which surfaces are obtained by the inscription of said propeller on a conical surface, of conicity superior and concentric to the conicity of the body (1), thus causing a variation of the thread pitch (2) of the body (1) preferably of the order of 41% between the distal pitch and the proximal pitch, characterized in that the axial guide surface (1) 5) of the body (1) is locally concave radius of curvature R1 greater than at least 5 times the mean radius of the body (1) and that the axial bearing surface (6) of the body (1) 20 is locally convex of radius of curvature R2 smaller than the mean diameter of the body (1), which rays make it possible to ensure, over the entire length of the body (1), a constant, preferably obtuse, bottom threading angle (beta) (8). order of 100 °. Mean diameter (respectively radius) means the body (1) diameter (respectively radius) of the latter taken in its axially median zone. In addition, the invention is characterized in that the body (1) is provided with self-tapping arrangements (7) regularly spaced along its length, said self-tapping arrangements (7) succeeding each other at a frequency of one per revolution minimum, and characterized in that the distal end (21) is provided with a self-piercing arrangement (10). The self-piercing arrangement (10) avoids the prior use of a drill and thus eliminates the risk of destabilization before insertion of the screw. As a result, the self-tapping arrangements (7) prevent any accumulation of bone debris during the penetration of the screw and thus ensure a gradual and regular compression, both in the longitudinal direction and radiai. -5

The screw according to the invention comprises a thread (2) whose pitch gradually decreases from the distal end (21) to the proximal end (22), thereby allowing continuous and regular axial compression, along the axis of body revolution (1), throughout the penetration of the screw into the bone. In addition, the depth of the threading (2) decreases progressively from the distal end (21) towards the proximal end (22) preferably from 24.3% to 28.50%, thus ensuring radial compression. increasing caused by increasing the diameter of the core of the screw, relative to the axis of revolution, as the penetration of the screw in the bone. This double compressive effect ensures excellent progressivity of compression effort and maximum stability between bone fragments. The configuration of the screw according to the invention is characterized in that the axial guide surface (5) of the thread (2) is oriented towards the distal end (21) and the axial bearing surface (6) of the thread ( 2) is oriented towards the proximal end (22).

The screw according to the invention has a body (4) for driving the body (1) in rotation, consisting of a recessed relief of conical shape on the depth of the compression head (3), which conical shape makes it possible to gripping the body (1) by a tool of concomitant shape to said recessed relief. Advantageously, the conically-shaped recessed relief also makes it possible to grip the body (1) in case of possible extraction, the extraction being able to be performed without creating bone damage around the extraction site. The configuration of the screw according to the invention is such that the body has an internal axial recess (9), opening on the proximal (22) and distal (21) ends, coaxial with the rotational drive member (4). . This axial recess (9) is arranged to cooperate with a guide pin. The screw according to the invention has a compression head (3) with a proximal end foam (11) allowing a total burial atraumatic in the bone, and thus to safeguard the functionality of the joint facing the landfill . The prosthesis can be implanted percutaneously or openly. 2971138 -6-

The prosthesis is made of bio-implantable material (polymer, titanium, alloys, stainless steel, mixed metal-polymer), of mineral or synthetic material for example PEEK (polyetheretherketone) or PEKK (polyetherketoneketone), or any other material accepting them. constraints.

Claims (8)

REVENDICATIONS1. Screw for surgical use more particularly intended for the reduction of non-displaced fractures, constituted on the one hand by a conical body of revolution (1) which comprises at its periphery a helical protruding part, or thread (2), on the other hand part of a cylindrical part, or compression head (3), located at the proximal end (22) of the body (1) and of diameter equal to the largest diameter of the protruding part of the helix, which compression head (3) is provided with a member (4) driving in rotation about its axis of revolution, the thread (2) having an axial guide surface (5) of the body (1) and an axial bearing surface (6) of the body (1) on the bone, characterized in that said surfaces form between them on the periphery of the body (1) an acute angle (alpha) which increases progressively from the distal end (21) towards the proximal end (22): alpha-discal <alpha proximal, thus achieving an asymmetrical profile the angle increases continuously from the distal end (21) to the proximal end (22) preferably by an amount of between 5% and 6.8%, thus providing increasing compression both longitudinally and in the radial direction, during the penetration of said screw, which surfaces are obtained by the inscription of said helix on a conical surface, of superior conicity and concentric to the conicity of the body (1), thus causing a variation of the thread pitch ( 2) of the body (1) preferably of the order of 41 ° / o between the distal pitch and the proximal pitch, characterized in that the axial guide surface (5) of the body (1) is locally concave radius of curvature R1 greater than at least 5 times the mean radius of the body (1) and that the axial bearing surface (6) of the body (1) is locally convex of radius of curvature R2 less than the mean diameter of the body (1), which rays make it possible to ensure throughout the length of the body (1) a constant and preferably obtuse netting (beta) netting (8) of the order of 100 °, characterized in that the body (1) is provided with self-tapping arrangements (7) regularly spaced along its entire length, said self-tapping arrangements succeeding each other at a frequency of one per revolution minimum, and characterized in that the distal end (21) is provided with a self-piercing arrangement (10), 2. Screw according to claim 1, characterized in that the pitch of the thread (2) decreases progressively from the distal end (21) towards the proximal end (22), thereby allowing a continuous and regular axial compression, according to the axis of revolution of the body (1), throughout the penetration of the screw into the bone 5 3. Screw according to claim 1, characterized in that the depth of the thread (2) decreases progressively from the distal end (21) to the proximal end (22) preferably from 24.3 ° / 8 to 28.5%, thereby providing increasing radial compression caused by increasing the diameter of the screw core relative to the axis of revolution as the screw penetrates into the bone. 4. Screw according to claim 1, characterized in that the axial guide surface (5) is oriented towards the distal end (21) and the axial bearing surface (6) is oriented towards the proximal end (22). 5. Screw according to claim 1, characterized in that the drive member 15 in rotation (4) of the body (1) consists of a recessed recessed conical shape on the depth of the compression head (3). ), which conical shape makes it possible to grip the body (1) by a tool of concomitant shape to said recessed relief 6. Screw according to any one of the preceding claims, characterized in that the body (1) has an internal axial recess (9) 20 7. Screw according to claim 6, characterized in that said axial recess (9) is opening at the distal end (21) and in the rotary drive member (4), being furthermore coaxial with said body member. 'training 8. A screw according to any one of the preceding claims, characterized in that the compression head (3) has a foam proximal end (11) allowing a total burial atraumatic in the bone, and thus allowing to safeguard the functionality of the joint facing the landfill