FR2722975A1 - Surgical implant for fastening ligament against bone surface - Google Patents

Abstract

The fastener has a W-shaped body defining a series of five-arm sections. A central vertical arm (1) is linked to a pair of upwardly-inclined outer arms (2,3) by intermediate arms (4,5), the outer and intermediate arm portions meeting at acute-angled bends (7,8). The central arm has a longitudinal through passage whose upper opening (11) is higher than the ends (9,10) of the two outer arm portions. The lower opening (12) of the through passage is flush with the lower surface of the junction between the two intermediate arm portions. The fastener is formed of a biocompatible shape-memory material, which has a martensitic transformation temperature below the temperature of the human body.

Description

Unstable sysin for stent fixation including a ligament implant
The present invention relates to implantable stent fixation systems, in particular of ligament implant.

The present invention can moreover be used in a unique manner, in particular for the production of staple-type prosthetic material.

Finally, the present invention can be fixed by welding to another rigid part such as joint reconstruction prostheses used in various orthopedic pathologies, in particular prostheses of the femur, knee, ankle, feet and hands (inter-phalangeal and metatarsal and metacarpal arthroplasty). phalangeal), elbow, shoulder, spine.

All types of rigid surgical prosthesis and ligament implants having a rigid part face the essential problem of their fixation.

The invention relates to a self-locking fixation technique for a ligamenial implant, it also relates to a technique for carrying out such a fixation technique. The technique of this fixation can be used in a unique way when it is coupled to a ligament implant connected to a shape memory system, or be an integral part of an articular prosthesis by allowing
optimal fixation.

In the following description and in the claims, reference will be made more particularly to this shape memory system used in a unique manner so as to allow optimal fixation of a ligament implant, it being understood that this exemplary embodiment is not in no way limitative, the invention can be used in other applications whether articular or in the context of the consolidation of any kind.

As we know, the fixation of a ligament implant can be done by different techniques: the ligament implant can be fixed to the bone structure by a screw, a staple. It can be done routinely by a rigid structure which is embedded in the cancellous bone after creation of a suitable hole. This technique is commonly used in the case of knee ligament prostheses. A rigid structure of variable cylindrical shape, conical or V, allows the attachment of one end of the ligament prosthesis and its anchoring, we have also proposed in the case of orthopedic joint prostheses, such as hip, knee or inter prostheses
phalangeal anchoring means with cement, in particular based on acrylic polymer such as polymethyl methacrylate. The problems of this fixing means are well known. Cement does not age well over time. The cement bone interface and the cement prosthesis interface cause stresses promoting mobility and therefore loosening of the implant with its procession of painful symptomatology and surgical recovery. In addition, during the polymerization of the cement at temperatures reaching 60 and above, phenomena of bone necrosis may occur.

Other anchoring systems use self-locking material, adding the use of a madreporic surface promoting bone rehabitation.

In the latter two cases with cement or cementless implants, if it is necessary to consider changing the prosthesis, the operation becomes difficult or even impossible.

In the case in particular of the implants used in knee reconstruction ligamentosplasties, these implants require for their fixation the use of screws or staples which can weaken the implant and which moreover often require their removal given their large volume. In the case of smaller implants used in particular in foot surgery, reconstruction ligaments have appeared which require the rigid part of the ligament implant to be anchored in the cancellous bone, this device is made essential by the small size of the bones considered which do not not allow the use of larger materials such as screws, postoperative can occur phenomena of migration of the anchored part.

In Patents FR k2 483 218; EPs0050533 have been proposed to make a longitudinal slit in the rod of an articular implant in order to give it elasticity and
favor its installation, but the latter must always be done in force with the risks of bone decay especially in the elderly.

Extraction is likewise very difficult or even impossible in the event of problems and therefore limits the use of this type of implant, particularly in children or adolescents since, depending on growth, the prosthesis in question cannot be easily removed.

The implant with shape memory system according to the invention which is made of a compatible biological material is split discontinuously over its width into 4 parts and over its length so as to form 5 distinct parts, 2 internal branches (4) and (5) and 2 external branches (2) and (3) and a central part (1), is characterized in that the material has a shape memory and a transformation temperature
martensitic below the temperature of the human body.

The invention therefore consists in producing an anchoring system in a shape memory material and a temperature Ms lower than the temperature of the human body, so that by raising it to a temperature close to that of the human body, the branches internal and external 1 and 3 take a slightly spaced form compared to their
initial position form of which they have acquired the memory by a method known in the art.

In the case of digestive surgery the same problem arises as in orthopedic surgery of small joints, it is necessary to bury in the bone the rigid part of the ligament implant, thus in particular in the case of the surgical treatment of hernias it is necessary to practice ligament anchoring at the level of the pubis and also the low volume of the material used promotes its subsequent migration.

The present invention with shape memory and non-deformable longitudinal axis allows the
precise placement of a ligament implant, since the non-deformable part serves as a traction axis, and therefore serves as a guide during the introduction of the implant into the implanted tissue.

The present invention makes it possible, by its shape memory character and by its design, to ensure better support on the bone cortex in the case of joint prostheses and better anchoring in the cortex and cancellous bone in the case of ligament implants.

In another form of the present invention, it should be noted that the material used can
not to be in shape memory. The central part (1) then serving as the traction axis during the rMse in place of the system.

The present shape memory system is presented with 5 branches which can be of cylindrical, round or rectangular cut, these branches can present on their
surface all types of grooves which would ensure better anchoring.

The 5 parts (2; 4; 5; 3; 1) can be performed by any known technique such as
as molding, forging, rubbing, machining. Other patent applications recommend
the use of 2 branches especially in the case of prosthesis with cortical support.

This is true in this type of indication because an increase in the number of branches
would lead to an increase in cost and a weakening during their use in the case of small joints.

But this patent application does not allow anchoring in a spongy bone tissue
eliminating mobility of the anchor. The shape according to the invention makes it possible, by its portions (2; 8; 4; 5; 7; 3; 10; 9; 11) to prevent these displacements.

The manner in which the invention may be produced, will emerge from the following exemplary embodiments, are given for information and are not limiting in support of the attached figures.

Referring to the accompanying schematic drawings, the present invention will be described.

- Figure 1 is a front view according to the invention arranged in the position of
ready to use presentation before cooling.

- Figure 2 is a front view according to the invention arranged in position during
cooling.

- Figure 3 is a front view according to the invention arranged in its final position after implantation and warming up to room temperature.

The present invention resembles:
- Substantially a W with a straight central branch (1), comprising two ends (11) and (12) and two lateral V-shaped branches (10) and (4) and (5) and (3) bent at their lower parts in (8) and (7) respectively.

By machining, a hole (6) with a diameter of about 0.5 mm is cut in the right central part (1). This hole is circular but can have any shape in the transverse direction. This orifice is present along the longitudinal axis of the part (1).

The material constituting the present invention is a Titanium Nickel alloy (49.3 atomic% of Titanium and 50.7% of Nickel) whose martensitic transformation Ms is close to 15 C.

Mechanically, at room temperature, a corner is spread in the bent spaces (8), (7) as well as in the space between the portions (4) and (5) and (10) room temperature T1 so as to spread the branches (2), (4), (5) and (3). This operation is carried out at a temperature higher than Ms (15). The invention (A) acquires a first memory of spread shape, the corners are removed, The implant is soaked in ice water while tightening the ends (2) and (3), The implant thus acquires this memory of folded form since the temperature T2 of 00C is lower than the temperature Ms, the operation is repeated ten times at temperatures T1 and T2.

Thus is obtained a shape memory implant with a longitudinal orifice having the shapes separated at the temperature T1 and folded back at the temperature T2, but which at room temperature is in the form of branches (2). (4). (5) (3) discarded.

The implant has on its surface alveoli or micro porosities or any other
reliefs allowing the proliferation of bone tissue.

At the level of the cancellous bone, when the surgeon wishes to place a shape memory implant (A), he prepares an osteotomy in a known manner. To fold the branches a component such as a cooling spray, or ice water can be used.

The ends of the branches (2) and (3) are folded, the width of the implant is then 7 mm. Then this implant is introduced into the spongy tissue, with the temperature
of the bone, the branches move apart without the need for artificial, for example electrical, warming of the implant. Given the substantially W shape, the implant is blocked in the spongy tissue in all directions. If the surgeon wishes to remove the implant, by reverse traction it is removed.

There is no need to cool the implant to extract as described in
the case of joint prosthesis (patent filing 86420306.2) because in the spaced position the spongy tissue does not offer enough resistance to traction performed in the opposite direction to the direction of implant placement.

A new placement can be practiced, because the osteotomy, makes it possible to place the implant on another level. So this type of shape memory implant substantially in
W, can be used on children or adolescents since depending on the growth, the prosthesis in question can be easily removed.

This shape memory implant with non-deformable longitudinal axis can also be applied in the same way to the tendons, muscles, or ligament.

The first portion (2) extends into a branch of shorter length (4), then the
fixed zone (1) extends to the portion (5) of length less than the following portion (3).

The present invention has a shape substantially in W, but can have another shape made of several W, having a common central part (1).

Different types of length can be considered. According to a characteristic of the invention, the fixed portion (1) has a through hole (6). This through hole (16) therefore has one end (11) protruding, the ends (9) and (10) and at an acute angle shape, allowing its introduction into the implanted tissue, it will be noted that in an advantageous form of the invention, the through hole (6) has another
end (12) conforming to the curvature connecting the parts (8) and (7), but in another form, this end can be drawn on an extension of the fixed part (11) and would therefore be in relief relative to the parts (8 ) and (9). The entire fastening system is therefore in one piece and made of a martensitic material.

We will note that part 1 of the shape memory implant has a greater length than parts 2 and 3 this allows the implantation to be put in place, to exert a trration in the longitudinal axis and to authorize the first entry of the end (11) into the implanted tissue. Part 1 is used as a guide for the entire runplant. This shape therefore allows the implant to be placed in a tendon tissue, such as the Achilles tendon. We note that part (1) can present a
another dimension insofar as it makes it possible to maintain an axis of traction. In the absence of this non-deformable longitudinal fixed part, the traction would not be exerted in a uniform manner and the implant would be mobile in all planes. The shape of the central part (1) can present any modification which will allow the particular fixing of a ligament implant, this one being able in particular to consist of 2 parts soul and sheath of the same, at the level of the internal surface of the through hole any modifications of form are possible.

The developments of the invention are particularly suited to small joints.

The portions (8) and (7) between the portions (2) and (4) on the one hand and (5) and (3) on the other hand have a rounded external shape, which allows easy extraction of the implant.

The ends (10) and (9) have an appropriate shape but preferably they are at acute angles in an advantageous form of the invention but can have any shape.

Claims (5)

 1. Stent fixation system, in particular of a ligament implant, characterized by a substantially W-shaped configuration consisting of 5 branches: 1 central branch (1), 2 lateral branches, composed of segments (2); (4) and (5); (3) bent respectively in (8) and (7). The branch (1) having a longitudinal orifice whose end (11) projects beyond the ends (9) and (10) of the branches (3) and (2) and whose lower end (12) is continuous with the bent portions ( 4) and (5).  2. Stent fixation system according to claim (1), made of a biologically compatible material, characterized in that the material has a shape memory and a martensitic transformation temperature Ms lower than the temperature of the human body.  3. Fastening system according to claim 1 to 2 characterized in that the lateral branches (2); (4) and (3); (5) are symmetrical with respect to the central branch (1).  4. Fastening system according to one of claims 1 to 3 characterized in that the implant is made of an alloy comprising the alloys, titanium, nickel, copper-manganeze, copper zinc, platinum iron, copper aluminum zinc.  5. Method for manufacturing a fixing system with shape memory substantially in W blocking according to claim (2) characterized in that it consists:  - First of all, to carry out a shape memory attachment system in a serially W shape and a martensitic transformation temperature Ms below the temperature of the human body,  - Then to bring this shape memory fixing system substantially in W to a temperature T1 higher than Ms while spreading the branches (2) (4) (5) (3),  - Then to cool the fixing system with shape memory thus removed to a temperature T2 lower than Ms while tightening the ends of these separated branches,  - And finally to repeat several times these last two operations T1 and T2 until the branches of the implant have acquired shape memory: set aside T1 and folded back T2.