Method of osteosyntheses or arthrodeses of two- bone parts, in particular of the hand and / or foot

Abstract

In one embodiment, the present invention is a method of arthrodeses or osteosyntheses of a first bone part and a second bone part, including the steps of positioning a first fixation zone of an implant in the first bone part and a second fixation zone of the implant in the second bone part, both the first and second zones made of shape-memory material and, prior to positioning the bone parts, are in an inner position; and while the first fixation zone is within the first bone part and the second fixation zone is within the second bone part, fixating the respective first and second fixation zones within the respective bone parts through shape-memory action at body temperature.

Description

FIELD OF THE INVENTION

The invention relates to the technical field of orthopaedic implants, particularly for arthrodeses and osteosyntheses.

It may be recalled that the object of an arthrodesis is to obtain very good stability both primary and secondary, and to place, or to maintain, in compression, two bone parts or bone fragments that should be consolidated. Stability is a critical factor for obtaining consolidation, while minimizing the attendant problems such as pain, swelling, etc. The compressive action serves to consolidate the osteotomy more rapidly in the position selected by the surgeon during the operation.

Various technical solutions have been proposed for carrying out an arthrodesis, particularly in the foot, the hand, the wrist, etc. Mention can be made, for example, of basic staples without shape memory which do not produce a compression, as opposed to memory staples which serve to place the two bone parts to be consolidated in compression, which corresponds to the objective.

However, to obtain satisfactory stability, it is necessary to place two, or even three staples, in different planes. This increases the dimensions considerably, thereby limiting applications (metacarpo-phalangeal joint, for example).

Extramedullary plates and screws have also been proposed, requiring an alternatively large dimension. In this respect, their miniaturization is difficult to conceive, because this could raise problems of strength and stiffness. Some types of screws can be used in intramedullary osteosynthesis, but they raise positioning difficulties (passage through the pad in particular).

Use can also be made of pins which have a smaller size. However, the stability obtained is unsatisfactory and it is necessary to withdraw them.

Intramedullary nails are also known, but they require supplementary stapling in order to prevent the bone parts to be joined from rotating relative to each other.

OBJECT OF THE INVENTION

It is the object of the invention to remedy these drawbacks simply, safely, effectively and efficiently.

The problem that the invention proposes to solve is to permit the fixation of two bone parts to one another, rigidly with dynamic and retentive compression, in order to obtain a reliable and rapid osteosynthesis.

SUMMARY OF THE INVENTION

To solve such a problem, an intramedullary arthrodesis element has been designed and developed which consists of a body with an elongated shape having, in succession, from one of its ends, a fixation zone cooperating with one of the bone parts to be immobilized, a median zone suitable for withstanding shear and bending stresses, and a fixation zone in the other bone part to be immobilized, each of the fixation zones being profiled and made from a material suitable for enabling introduction into the bone parts without a finger- or toe-tip approach, followed by a fixation in the bone parts, while avoiding any rotational movement, withstanding the tensile stresses, and maintaining a compressive force.

The invention has a particularly advantageous application, which can however not be considered as limiting, for the preparation of arthrodesis in the proximal and median phalanges, for proximal interphalangeal joints and distal interphalangeal joints, in the hand or foot.

To solve the problem of taking account of the anatomy, and particularly of the internal shrinkage of the bone, the median zone is linked to at least one of the fixation zones by a connecting zone.

To solve the problem of permitting implantation of the element followed by compression of the bone fragments, the fixation zones are made from a shape-memory material to be deformed by thermal and/or mechanical action.

To produce the fixation zones, which may be identical or not, various technical solutions are feasible, according in particular to the type of arthrodesis performed and the joints to be treated.

For example:

one of the fixation zones has two tabs or wings separable under the action of the shape memory;

one of the fixation zones has a tab or rod which can be curved under the action of the shape memory;

one of the fixation zones has, in its thickness, a slot for permitting deformation by elasticity, or memory, under the action of the shape memory.

In one embodiment, the overall body has a flat cross-section.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described below in greater detail in conjunction with the figures of the drawings appended hereto in which:

FIG. 1 is a schematic plan view showing the placement of the intramedullary arthrodesis element of the invention between a proximal phalange and a median phalange to consolidate the proximal interphalangeal joint;

FIG. 2 is a plan view of an embodiment of the arthrodesis element at the time of its introduction;

FIG. 3 is a view corresponding to FIG. 2 showing the arthrodesis element after its implant to produce the compression;

FIG. 4 shows the placement of the element of the invention in a toe.

SPECIFIC DESCRIPTION

The arthrodesis element of the invention consists of an elongated body 1. Each of the ends of the body 1 is conformed to produce a fixation zone 1a linked to a fixation zone 1b.

Between the two fixation zones 1a and 1b, at least one median zone 1c is formed capable of withstanding shear and bending stresses. In general, the shear and bending stresses are applied to the bone site to be consolidated. The shape of this median zone 1c is adapted to the internal shape of the bone. Its length is determined in order to allow a slight offset in the centering.

For information, and in a non-limiting manner, this median zone may have a rectangular cross-section measuring about 2 to 3 mm*1 to 1.5 mm and a length of about 3 to 5 mm for the foot and the hand.

The fixation zones 1a and 1b are conformed to prevent any rotational movement, resist tension, and maintain manual compression applied at the time of the implant by the surgeon in order to reduce the site. To obtain this result, the fixation zones 1a and 1b are made from a shape-memory material to be deformed by thermal action (tepid memory) or mechanical action (superelasticity) (see U.S. Pat. No. 5,958,159). The goal, in the fixation zones, considering their profile on the one hand and the type of material on the other, is to permit an introduction into the bone parts, particularly dorsally without a finger- or toe-tip approach, on the one hand, and to produce a fixation in the bone portion in order to obtain or to maintain the desired compressive force, on the other. The fixation zones 1a and 1b are identical or not, according to the type of bone and its morphology.

Depending on the type of arthrodesis performed, that is, the type of interphalangeal joint to be consolidated for example, the fixation zones 1a and 1b may have different embodiments.

For example, one of the fixation zones 1a has two tabs or wings that are separable under a thermal action for example. Otherwise, these fixation zones 1a may have a single tab or rod which can be curved under the action of a memory of the component material. Otherwise, the fixation zone 1b has, in its thickness, a slot to permit deformation by elasticity, under thermal action for example, and to maintain the position by pressing on the length of the bone.

According to another feature of the invention, to take account of the anatomy of the various phalanges for example, that is the internal shrinkage of the bone (hourglass shape), the median zone 1c is linked to at least one of the fixation zones 1b by a thinner connecting zone 1d.

Reference can be made to the figures of the drawings which show an embodiment of an intramedullar arthrodesis element.

In this embodiment, the body 1 has, at one of its ends, a fixation zone 1a in the form of two tabs or wings 1a11a2. This fixation zone 1a is prolonged by a median zone 1c of generally substantially triangular shape in a plan view. The median zone 1c is connected to the other end fixation zone 1b by a connecting zone 1d having a generally rectangular shape in a plan view. The fixation zone 1b has, in its thickness, a slot of generally oblong shape 1b1.

Reference can be made to FIG. 2 which shows the element at the time of its introduction, that is before separation of the tabs 1a1 and 1a2, and the opening of the slot 1b1. For example, this configuration is obtained when the overall element is subject to a temperature much lower than that of the human body for example. Conversely, after implantation (FIG. 3), under the effect of body heat, the tabs 1a1 and 1a2 separate, in the same way as the slot 1b1, concomitantly causing a deformation of the fixation zone 1b.

It should be noted that the profile of the median zone 1c prevents penetration when the site is reclosed.

In an alternative embodiment, the connecting zone 1d can be split to benefit from a swelling effect by shape memory and strengthening of the anchoring in the diaphyseal zone.

It should be recalled that the inventive element is ideal for the treatment of the hammer- or claw-toe syndrome, by performing an arthrodesis in the phalanges P1 and P2 on the radii 2 to 5, while observing that such applications must not be considered as limiting, by means of essentially dimensional adjustments (finger reimplants, arthrodesis of the distal interphalangeal joint and of the proximal interphalangeal joint of the hand, and the arthrodesis of the big toe).

Obviously, the entire arthrodesis element of the invention may have constructive features suitable for improving the fixation and compression in particular.

For example:

notches on the tabs on one of the sides for better fixation in the ethmoid bone;

wavy tabs implanted (straight before implant) to permit shortening and hence an additional compression of the arthrodesis site compared with a simple fixation;

a tapered central zone to avoid undesirable penetration of the implant at the time when the site is to be closed.

For information, the memory used is preferably a tepid memory, so that heating is unnecessary because of the lack of access. The opening begins at above 15 to 20° C. and stops at about 30 to 35° C.

The operating technique remains conventional.

Claims

1. A method of securing a first bone part to a second bone part, comprising the steps of: obtaining an implant having a body including a flat cross-section, a first fixation zone and a second fixation zone, each fixation zone made of shape-memory material and including a respective pair of tabs displaceable between an outer position in which they diverge from one another and an inner position in which they are closely spaced, wherein the implant is in the inner position;positioning the implant, while in the inner position, such that the pair of tabs of the first fixation zone are within a single opening in the first bone part and the pair of tabs of the second fixation zone are within a single opening in the second bone part; andwhile the first fixation zone is within the first bone part and the second fixation zone is within the second bone part, allowing the pairs of tabs of the respective first and second fixation zones to displace to the outer position through shape-memory action at body temperature.

2. The method of claim 1, wherein the first and second bone parts are in the hand or foot.

3. The method of claim 2, wherein the first and second bone parts are within either a proximal interphalangeal joint or a distal interphalangeal joint.

4. The method of claim 1, wherein the pair of tabs of one of the first or second fixation zones has outer ends that are joined unitarily together forming a slot therebetween, wherein the slot has an elongated shape in the inner position and an O-shape in the outer position.

5. The method of claim 1, further comprising, following the positioning step, manually compressing the first bone part and the second bone part together.

6. The method of claim 1, wherein, in the outer position, the implant is stabilized relative to the first and second bone parts to avoid relative rotation of the implant as to the first and second bone parts, withstand tensile forces, and maintain compression of the first and second bone parts.

7. The method of claim 1, wherein the positioning step includes moving the implant into the first and second bone parts from a dorsal approach.

8. The method of claim 1, wherein as the respective pairs of tabs displace from the inner position to the outer position, the implant compresses the first and second bone parts together.

9. The method of claim 1, wherein with the respective pairs of tabs in the outer position, the implant produces a fixation between the first bone part and the second bone part.

10. A method of arthrodeses or osteosyntheses of a first bone part and a second bone part, comprising the steps of positioning a first fixation zone of an implant within a single opening in the first bone part and a second fixation zone of the implant within a single opening in the second bone part, both the first and second zones having a flat cross-section and being made of shape-memory material and, prior to positioning the bone parts, are in an inner position; andwhile the first fixation zone is within the first bone part and the second fixation zone is within the second bone part, fixating the respective first and second fixation zones within the respective bone parts through shape-memory action at body temperature.

11. The method of claim 10, wherein the fixating step includes displacing the first and second fixation zones from the inner position to an outer position through shape-memory action.

12. The method of claim 10, wherein the first and second fixation zones each include a respective pair of tabs displaceable between the outer position in which the tabs diverge from one another and the inner position in which the tabs are closely spaced.

13. The method of claim 12, wherein the pair of tabs of one of the first or second fixation zones has outer ends that are joined unitarily together forming a slot therebetween, wherein the slot has an elongated shape in the inner position and an O-shape in the outer position.

14. The method of claim 12, wherein, in the inner position, the first and second fixation zones can freely pass into the respective first and second bone parts and in the outer position, the first and second fixation zones are fixated within the respective first and second bone parts.

15. The method of claim 10, wherein the positioning step includes positioning the first fixation zone within an intramedullary canal of the first bone part and positioning the second fixation zone within an intramedullary canal of the second bone part.

16. The method of claim 15, wherein the positioning step includes moving the implant into the intramedullary canals of the first and second bone parts from a dorsal approach.

17. The method of claim 10, wherein the first and second bone parts are within either a hand or a foot, and within either a proximal interphalangeal joint or a distal interphalangeal joint.

18. The method of claim 10, further comprising, following the positioning step, manually compressing the first bone part and the second bone part together.

19. The method of claim 10, wherein as the respective pairs of tabs displace from the inner position to an outer position, the implant compresses the first and second bone parts together.

20. The method of claim 19, wherein with the respective pairs of tabs in the outer position, the implant produces a fixation between the first bone part and the second bone part.