WO1992013496A1

WO1992013496A1 - Frame for rigidifying a bone or a bone assembly

Info

Publication number: WO1992013496A1
Application number: PCT/FR1992/000085
Authority: WO
Inventors: Michel Maestro; Lucien Faustin Tomasoni
Original assignee: Biostab
Priority date: 1991-02-01
Filing date: 1992-01-31
Publication date: 1992-08-20
Also published as: EP0569497A1; FR2672203B1; FR2672203A1

Abstract

Frame for rigidifying a bone or a bone assembly, such as the rachis, of the type having two plates (21) intended to be fixed on either side of a bone or a group of bones and at least two yokes (22, 23) in order to firmly join the plates (21) to each other in the transverse direction so as to form the frame (20), the plates having a shape, and particularly a bending which generally adapt them to the bone or bone assembly considered (S1, L3-L5), the frame being characterized in that each yoke (22, 23) has at least one mounting section (35) presenting a mounting surface (30), while each plate (21) has at least one mounting post, presenting a mounting surface (41), one (30) of said mounting surfaces being concave, the other mounting surface (41) being convex with a mean curvature radius equal to or smaller than the radius of said concave surface (35) so that the convex mounting surface (41) is appropriate to cooperate with the concave mounting surface (30).

Description

FRAME FOR RIGIDIFICATION OF A BONE OR A SET OF BONES

1

The present invention relates to a frame for stiffening a bone or set of human or animal bones. The present invention finds a preferred application during osteosynthesis operations of the spine vertebrae and arthrodesis with osteosynthesis of spine joints. It also finds other applications in restorative surgery of bones and joints.

We know in particular from FR-A-2,612,070 and FR-A-2,612,762, a stiffening frame intended for arthrodesis of one or more spinal joints. such a frame comprises, in general, two plates fixed on either side of the spine and on either side of the joint considered. These plates, which have a shape and, in particular a bending adapted to the shape and the curvature of the zone considered of the spine, are joined transversely by means of two bridges or crosspieces screwed onto these plates, so as to constitute a rigid frame. In this way, the joint considered is stiffened and a natural calcification process leading to the welding of the two vertebrae considered (arthrodese) can then take place. This frame can be removed during a second operation, if the arthrodesis is successful.

However, this known framework has various drawbacks. Indeed, the geometry of the frame is predetermined once and for all by the dimensions of the plates and crosspieces used, because the fixing points of the crosspieces on the plates are predetermined and leave no room for play except, in certain cases, a play transverse (see for example FR-A-2.612.762). It follows that the framework of the prior art lacks flexibility and is difficult to install. Indeed during the particularly delicate implantation operation, the surgeon must position the plates on the vertebrae considered of the spine, such so that the means of securing the sleepers with the plates arranged on these elements coincide.

It follows that in practice, there can be no offset of any kind whatsoever between the plates, with respect to the geometry of the frame which is defined once and for all, which in particular requires mounting the plates on spinal supports belonging to the same flat or cylindrical surface, so as to avoid any offset.

It therefore appears that it is desirable to be able to have a stiffening frame whose geometry is not unique and fixed once and for all, which during the setting-up operation of the frame, makes it possible to shift within certain limits, the plates relative to each other, according to one or more degrees of freedom, in particular angular.

The present invention overcomes the above drawbacks and solves the problem posed because it aims at a framework for stiffening a bone or set of bones, such as the spine, of the kind comprising two plates intended to be fixed from one side and the other of a bone or set of bones considered and at least two crosspieces intended to secure the plates to one another in the transverse direction, so as to constitute the frame, the plates having a shape, and in particular a bending, generally adapted to the bone or set of bones considered, characterized in that each crosspiece comprises at least one mounting section comprising a concave mounting surface, while each plate comprises at least one mounting stud, having a convex mounting surface, the mean radius of curvature of which is equal to or smaller than that of said concave surface, so that the convex mounting surface of the stud is able to cooperate with the surface co mounting cross member.

In a preferred embodiment of the invention, the mounting stud has a spherical convex mounting surface, while each crosspiece comprises at minus a concave toroidal mounting surface, capable of cooperating with the spherical mounting surface of the studs.

Thanks to these provisions, the surgeon has a stiffening frame that is much easier to implant. Indeed, thanks to the cooperation of the convex surface of the mounting studs with the concave surface of the crosspieces, the surgeon has a certain freedom of implantation because the mounting surfaces of the studs of the plates and of the crosspieces can be moved l '' in relation to each other in the longitudinal and / or transverse direction, while their orientation in relation to each other, in relation to the three axes of rotation, can vary within limits determined by the convex and concave geometries considered. In the preferred embodiment, said mounting surfaces are ridged.

Thanks to this arrangement, there is cooperation between certain ridges of the two mounting surfaces, which has the following advantages: - during the implantation operation, before the operation of fixing the crosspieces to the plates, these can be immobilized in the right position by simple pressure, which facilitates said fixing operation,

- And, subsequently, the streaks help prevent accidental movement of a crosspiece relative to the plate on which it is secured, and contributes., thereby, to the good performance of the assembly over time.

In the preferred embodiment, the mounting stud has a threaded hole, opening into said mounting spherical, capable of cooperating with a locking screw.

These provisions allow the use as locking means of the crosspieces to the plates, locking screws, which contributes to facilitating the implantation operation.

However, the use of locking screws to secure the sleepers to the plates is not the only mode possible binding for those skilled in the art in the context of the present invention.

According to another characteristic of the invention, advantageously implemented in the preferred embodiment of the latter, the concave mounting surface of the cross member extends generally along a predetermined axis, the mounting section of the cross member comprising a oblong mounting opening extending along said axis and passing through said concave mounting surface. Thanks to this arrangement, the surgeon has, in particular in the case of use of locking screws, a degree of freedom of positioning of the crosspiece relative to the plate, along said predetermined axis, the latter being, in this mode preferred embodiment, orientation parallel to that of the crosspiece.

The present invention also makes it possible to solve another problem which arises for surgeons when implanting frames of the state of the art referred to above. Indeed, the sleepers of the state of the art consist essentially of cylindrical rods. When a thorny spine is placed across the passage of a rod, taking into account the optimal implantation of the plates chosen by the surgeon, the latter must either perforate. the thorny, either proceed to cut it, which is not without presenting various drawbacks for the patient. In any event, this aspect of the operation is particularly delicate to implement because of the structure of the frames of the prior art. The present invention overcomes this drawback by proposing a cross member having an openwork intermediate part to allow the passage of the thorny. In a preferred embodiment, the aperture results from the conformation of the intermediate part of the crosspiece, in a horseshoe, so as to allow the passage of a thorny spine.

Thanks to these provisions, and more particularly thanks to the horseshoe part of the crossmember, we avoid cutting or drilling the thorn because the cross "bypasses" the thorn in question.

The frame according to the invention can also be used in other orthopedic restorative surgery operations. It can thus be used in particular for blocking certain joints such as the hip, knee or elbow.

The present invention also relates, on the one hand, to a plate and, on the other hand, to a cross member for a stiffening frame having the characteristics succinctly set out above.

The characteristics and advantages of the invention will become apparent from the description which follows with reference to the accompanying drawings in which: - Figure 1 is a plan view of a frame according to the invention, located on the lower part spine,

FIG. 2 is a sectional view along the axis II - II of FIG. 1, - FIG. 3 is a detail view of the mounting surface of the cross member illustrated in FIG. 1, the cross member being turned over,

- Figure 4 is a partial perspective view of the frame illustrated in Figure 1, - Figures 5a, 5b are detail views showing the cooperation of a mounting pad with the mounting surface of a cross member, allowing adjustment the range of the plates relative to an axis, and

- Figures 6a and 6b are detail views showing the cooperation of a mounting pad with the mounting surface of a cross member for adjusting the position of the plates relative to another axis.

The embodiment chosen and described in support of Figures 1 to 4, of the frame according to the invention, is intended to stiffen the lumbo-sacral hinge of the spine. In Figure 1, we recognize the sacrum S1 and the vertebrae L3-L5 lower back. The frame 20 comprises, here, a plate 21 and two crosspieces referenced at 22, 23. It is observed that crosspieces 22, 23 have a different transverse dimension, so that the plates 21, which are identical, can advantageously take an orientation oblique to each other, so as to be implanted in the appropriate places of the sacrum S1 and the lumbar vertebrae L3, L4 and L5.

The plates 21 have a shape, and in particular a bending visible in Figure 2, adapted a. the general geometry of the three lumbar and sacrum considered. In other embodiments, the plates 21 may have another bend, or even be rectilinear, taking into account the vertebrae or the bones on which they are intended to be implanted. Optionally, these plates can be made to measure, taking into account the spinal geometry and other particulars of the patient to be operated on.

The plates 21 comprise several series of openings 24, having a shape resulting from the longitudinal juxtaposition of several intersecting holes, so as to allow the passage of fixing screws 25, intended to secure the plates with the vertebrae concerned or the sacrum. These screws, called pedicle screws, are intended to be mounted, in a manner known per se, in the pedicle of the vertebrae, with an orientation such that the vertebral canal is not reached. At the level of the sacrum, the lights have the form of simple holes 28.

These arrangements are well known in the art and do not need to be described in more detail here.

In accordance with the invention, each crosspiece 22, 23 comprises at least one mounting section 35 comprising a mounting surface 30 of concave shape (not visible in FIG. 1), while each plate comprises at least one mounting pad 40, itself comprising a convex mounting surface 41, the mean radius of curvature of which is equal to or smaller than that of the concave surface 30 (Figures 3 and 4).

In the embodiment chosen and shown, the mounting surface 30 is a toroidal concave surface, substantially symmetrical with respect to a so-called "transverse" axis, parallel to the largest dimension of the crosspieces and bearing the reference 31 in the figures. The mounting surface 41 of the mounting studs 40 is substantially spherical in this embodiment, the radius of the sphere being substantially smaller here than the smallest radius of curvature of the toric surface 31.

Each plate here has two mounting pads

40, while each cross member 22, 23 has a mounting surface 30 arranged at each of its two ends. Generally, according to the invention, the mounting surface of the mounting section or sections of the sleepers is a concave surface which can have various geometric shapes. In the preferred embodiment, it has been seen that it is toroidal, and symmetrical with respect to the transverse axis 31; it can have any other concave shape. It can thus be, for example, a surface resulting from the spatial displacement of a portion of a concave generating plane curve, preferably circular or elliptical, parallel to itself along an epi-cycloidal guiding curve, the direction of the generatrices being generally perpendicular to that of the directing curve. It can also be spherical.

Similarly, in general, the mounting surface 41 associated with each pad 40, is convex but of any kind. In particular, it can be of the same nature as the three curved surfaces defined above, it being specified that its mean radius of curvature is equal to or less than that of said concave mounting surface associated with the crosspieces. In the embodiment chosen and shown, each mounting stud 40 has a tapped blind hole 42 opening into the convex surface 41, capable of cooperating with a locking screw 43. The O-ring mounting surfaces 30 associated with each cross member 22, 23 extend generally along the transverse axis 31. Each mounting section 35 of the cross members 22 , 23 comprises an oblong opening 33, which extends along the axis 31, and crosses the toric surface 30. These oblong openings have a width substantially greater than the diameter of the body of the locking screws 43.

It is also observed that, in accordance with another characteristic of the invention, the mounting surfaces 30 and 41 are ridged, the ridges on the convex mounting surface 41 of the pads 40 being of substantially radial orientation, while those of the surface mounting toroid 30 having an orientation substantially perpendicular to the transverse axis 31.

The studs have a height of the order of 7 mm in the embodiment chosen and shown.

The characteristics which have just been described allow the following cooperation: During the osteosynthesis operation of the lumbo-sacral hinge illustrated in FIG. 1, the surgeon begins by fixing the plates 21 by means of pedicle screws 25, as illustrated in Figure 1. The position of the plates is determined by the surgeon in accordance with the geometry of the vertebrae, so as to have the best possible support of the plates 21 on the lumbar vertebrae as well as on the sacrum. During this implantation, the surgeon does not have to look for supports for the plates belonging to the same cylindrical surface whose director would correspond to the bending of said plates. He only has to be interested in a good arrangement of the plates, so as to obtain the best possible stiffening of the assembly, and ensuring that the implantation of the pedicle screws 25 is done without risk for the patient. Then, to secure the frame in the transverse direction, the surgeon then presents the crosspieces 22, 23 as illustrated in the drawings.

Thanks to the cooperation of the mounting surfaces, and in particular to the fact that the mean radius of the convex surface for mounting the studs is smaller than or, at most equal to that of the concave mounting surface of the crosspieces

(in the embodiment this radius is smaller), said mounting surfaces can cooperate so that the cross member can be moved relative to the plates, keeping between the mounting surfaces concerned an at least "linear" contact. Indeed, the contact between the mounting surfaces is made at least along a portion of the curve and not punctually, which gives a good quality temporary support, at least during the mounting of the locking screws.

In practice, in the embodiment shown, by virtue of an aspect of the invention, this portion of the curve is materialized, on the side of the concave mounting surface of the crosspieces, by one of the striations of orientation perpendicular with respect to the axis 31, and, on the side of the convex surface of the studs, by two radial ridges, being at this moment opposite the considered rib of the concave mounting surface of the crosspiece. It is the same on each of the studs with which the cross member under consideration cooperates (22 or 23).

This cooperation of the ridges makes it possible, as long as a certain pressure is applied, to avoid a relative displacement of the crosspiece relative to the plates. The screwing of the locking screws 43 can then take place, without risk of displacement of the cross-member. This screwing causes a permanent immobilization of the crosspiece 22, 23 considered with respect to the plates 21.

In the embodiment shown, it has been chosen to fix the crosspieces 22, 23 to the plates 21 by means of locking screws 43. This characteristic makes it impossible to only to secure the crossbeams 22, 23 to the plates 21, but it also has the following advantages:

- During the mounting phase of the crosspieces on the plates, after mounting the plates on the bones in question, we can, initially, said to "adjust" do not tighten the screws 43. We can thus move the crosspieces relative to plates, while maintaining linear contact between the mounting surfaces, so as to obtain the best possible support and the relative position of the various elements most suited to the patient. We can then lock the screws when the optimal position is found,

- the use of screws makes it possible to obtain a particularly high clamping pressure. This latter advantage is combined with that of the use of ridges on the mounting surfaces. Indeed, it should be noted first of all that, in a conventional manner, the various elements of the frame, including the pedicle screws are made of pure titanium in accordance with the AFNOR T 40 standard. This metal has qualities well known in surgery restorative and it is relatively soft. Consequently, by tightening the locking screw 43, the surgeon forces the various ridges of the ridges, which do not interpenetrate during the adjustment time mentioned above, to interpenetrate during tightening, which promotes ie good maintenance of the assembly, and contributes, in particular during the tightening time, to preventing any accidental movement of the crosspieces relative to the plates. It is observed that at the end of tightening the contact between the mounting surfaces has become "surface".

Advantageously, the titanium constituting the crosspiece or the plate can be chosen so that it is harder than the other element, which makes it possible to promote the interpenetration of the striations during the tightening time, the hard edges of the striations penetrating. relatively easily in the material constituting the ridges of the streaks of the other element made of softer metal. The locking of the elements during the delicate clamping operation is thus even better ensured.

It is observed that the geometry of the mounting surfaces considered and the oblong openings 33 allow the following adjustments:

- as the oblong openings 33 have a dimension, in the direction perpendicular to the axis 31, substantially greater than the diameter of the screw body 43, a relative displacement of the crosspiece 22 relative to the plates 21, in the longitudinal direction (axis II ) can take place. Figures 6a and 6b illustrate, among other things, this adjustment,

- A relative displacement of the crosspiece 22 or 23 relative to the plates 21 in the direction of the axis 31 can also take place within limits imposed by the length of the oblong openings 33. Figures 5a and 5b illustrate among other things this adjustment.

the concave (toric here) and convex (spherical here) geometries of the mounting surfaces 30 and 41 allow angular deflections in the three directions between the crosspieces 22, 23 on the one hand, and the plates 21.

In fact, thanks to the respective geometry of the mounting surfaces, the crosspieces 22, 23 can assume almost any angular position around the axis of the locking screws, no theoretical limit being imposed in this embodiment on this adjustment.

In addition, the crosspiece can take relative to the plate various angular positions relative to the other two axes of rotation, which in reconstructive surgery, especially of the spine, is particularly important.

Thus, the second rotation is shown diagrammatically in FIGS. 3 and 4 by the arrows in thin lines bearing the reference 50. This rotation is illustrated at the level of the mounting portions 35 of the crosspieces and the mounting pads 40 by FIGS. 5a and 5b. Indeed, these figures illustrate not only the possibility of adjusting the position transverse of the crosspieces, but also the rotation 50. Two positions of the mounting pads relative to the mounting surface of the crosspieces are illustrated. There are in reality an infinite number of intermediate positions, the toroidal geometry of the mounting surface 30 of the mounting section 35 of the cross member and the spherical geometry of the mounting surface 41 of the stud 40 making it possible to adjust the position of the stud relative to to the mounting section 35, in the transverse direction (axis 31) independently of its angular position, in the direction of the arrow 50.

Likewise, a third rotation, transverse to the previous two, is shown diagrammatically in FIGS. 3 and 4 by the arrow 51. FIGS. 6a and 6b illustrate this rotation since they show the cooperation of the convex surface 41 with the concave surface 30 allowing to perform the angular adjustment in the direction of the arrow 51. It can be seen that this adjustment is independent of the adjustment of the longitudinal position of the crosspiece relative to the plate illustrated in these same figures, this independence resulting from the convex geometries (here spherical) and concave (here toroidal) of the mounting surfaces 41, 30 respectively of the stud 40 of the plate 21 and of the section 35 of the crosspieces 22, 23.

It therefore appears, therefore, that the geometry of the frame 20 is in no way fixed once and for all, but can vary in three dimensions, within the limits imposed by the geometry of the mounting surfaces, and, when the fixing of the plates to the crosspieces is made by means of locking screws, by those of the diameter of the body of the locking screw on the one hand, by the two main dimensions of said oblong openings.

The toroidal shape of the mounting surface 30 disposed at each end of the crosspieces 22, 23, was chosen, in this embodiment, taking into account its minimal bulk in a direction perpendicular to the transverse axis 31, and the possibility to have a surface developing along a relatively large length, in the direction of the axis 31. In the embodiment chosen and shown, the mounting surface 30 has a dimension, in the direction parallel to the axis 31, which is 17 mm, while in the transverse direction relative to the axis 31, this dimension is of the order of 1 cm.

The radii of curvature of the toric surface are: in the direction of the axis 31: 20 mm, in the direction transverse to this axis: 6.5 mm. In this embodiment, the convex surface associated with the mounting studs is spherical. The stud having a diameter of 10 mm, while the radius of the sphere is of the order of 8 mm.

Under these conditions, it appears that in the direction of arrow 50, the adjustment range of the cross member relative to the studs is 30 °, while in the direction of arrow 52, the adjustment range is 15 °.

It can be seen, under these conditions, that the surgeon thus has a large adjustment range in crosspieces relative to the plates in space.

The present invention solves another problem which has arisen for surgeons with sleepers of the state of the art. Indeed, it was recalled in the preamble to the present application that these sleepers required either the drilling of a thorny, or the cutting thereof; when the latter is on the passage- of a crosspiece.

The present invention overcomes this drawback by proposing sleepers comprising a portion 60 having an aperture. That is carried out, here, by conforming the portion 60 in horseshoe, which thus constitutes a housing 62, here of 15mm of depth, making it possible to accommodate the thorny 61, in the hypothesis where the axis 31 crosses this thorny. This characteristic is illustrated in particular at the level of the vertebra L4 in FIGS. 1 and. Other advantages of the frame according to the present invention as well as other advantages of the embodiment described and shown will appear to the surgeon readers. Of course, the present invention is in no way limited to the embodiment chosen and shown, but encompasses all variants within the reach of those skilled in the art. In particular, it has been mentioned that the plates can have any length, shape and / or bending capable of allowing their implantation at any level of the spine. Similarly, the shape of the various elements can be adapted to allow the same type of intervention on animal spines. Finally, this frame can be used for osteosynthesis of other bones, or for blocking joints such as the hip, knee or elbow. It can also be used on artificial bones for educational purposes, in particular for demonstrating the surgical method.

Furthermore, the plates which have been illustrated in the figures include passage openings 24 for the pedicle screws 25. On the day of filing of this patent application, it is planned to use, in the future, other modes of fixation of the plates on the bones considered.

Consequently, these plates may not include holes for the passage of pedicle screws illustrated in the drawings, but will nevertheless remain in accordance with the present invention if they have a stud with a convex mounting surface.

Likewise, in the embodiment described, provision has been made to fix the crosspieces to the mounting studs by means of locking screws 43. Here again, it is planned in the future to fix these plates by another means, in which case the oblong openings in the sleepers and the tapped blind hole in the mounting stud may no longer be useful. Furthermore, in the embodiment described, provision has been made to arrange the concave mounting surfaces 30 on the crosspieces and the convex mounting surfaces 41 on the studs. In other embodiments, it is envisaged to reverse these arrangements and to provide the concave mounting surface on the pads arranged on the plates, and a convex mounting surface on the crosspieces.

Similarly, in the embodiment chosen and shown, provision is made for the mounting surface 30 to be a concave surface of toroidal type, while the mounting surface 41 of the studs is convex, of spherical type. Of course, the present invention is in no way limited to this embodiment. Only the fact that the concave and convex mounting surfaces can cooperate with each other to obtain the desired adjustment latitudes. In particular, it is already planned, in an alternative embodiment, to arrange in the cross-section mounting section, a mounting surface of spherical type in place of the concave mounting surface of toric type.

Claims

CLAIMS 1. Frame for stiffening a bone or set of bones, such as the spine, of the kind comprising two plates (21) intended to be fixed on either side of a bone or set of bones considered and at least two crosspieces (22, 23) intended to secure the plates (21) to each other in the transverse direction, so as to constitute the frame (20), the plates having a shape, and in particular a bending, generally adapted to the bone or set of bones considered (S1, L3-L5), characterized in that each crosspiece (22, 23) comprises at least one mounting section (35) comprising a mounting surface (30), while each plate (21) comprises at least one mounting stud (40), having a mounting surface (41), one (30) of said mounting surfaces being concave, the other (41) being convex with a mean radius of curvature equal to or smaller than that of said concave surface (33), so that the convex mounting surface (41) is apt e to cooperate with the concave mounting surface (30).

2. Frame for stiffening a bone or set of bones, such as the spine ^~ , ^~ dτ-r ^~ kind "compo ^~ r ^~~ two plates (21) intended to be fixed on either side of a bone or set of bones considered and at least two crosspieces (22, 23) intended to join the plates (21) to each other in the transverse direction, so as to constitute the frame (20), the plates having a shape, and in particular a bending, generally adapted to the bone or set of bones considered (51, L3, L5), characterized in that each crosspiece (22, 23) comprises at least one mounting section (35) comprising a mounting surface (30) while each plate (21) comprises at least one mounting stud (40) comprising a mounting surface (41), one (30) of said mounting surfaces being concave and toric, l 'other (41) being convex and spherical with a radius of curvature is equal to or less than that of said concave toric surface (30), so that the convex surface mounting spherical (41) east able to cooperate with the concave O-ring mounting surface (30).

3. stiffening frame according to any one of claims 1, 2, characterized in that the convex mounting surface (41) is arranged on said mounting pad (40), while the concave mounting surface (30) is arranged in said mounting section (35) that includes each crosspiece (22, 23).

4. Frame according to any one of claims 3, 4, in which the plates also include openings (24) adapted to allow the passage of screws (25) intended for fixing said plates on the bone or bones considered (S1 , L3-L5).

5. Frame according to any one of claims 1 to 4, characterized in that said mounting surfaces (33, 41) are striated.

6. Frame according to any one of claims 1 to 5, characterized in that the crosspiece (22, 23) respectively the plate (21), is made of a material having a hardness greater than that of the plate (21) , respectively the crosspiece (22, 23).

7. Frame according to any one of claims 1 to 6, characterized in that the mounting stud comprises a tapped blind hole (42), opening into said convex mounting surface (41), able to cooperate with a locking screw (43).

8. Frame according to any one of claims 1 to 7, characterized in that said concave surface (30) extending generally along a predetermined axis (31), the mounting section (35) of the crosspiece (22, 23 ) has an oblong mounting opening (33), extending along said axis and crossing the concave surface (30).

9. Frame according to any one of the claims

1 to 8, characterized in that the crosspiece has an intermediate portion (60) perforated, so as to allow the passage of a thorny spine (61) of the spine.

10. Frame according to any one of claims 1 to 9, characterized in that the crosspiece comprises an intermediate part (60) having a horseshoe shape, so as to allow the passage of a thorny (61) of the spine .

11. Plate for stiffening frame according to any one of claims 1 to 10.

12. Cross member for a stiffening frame according to any one of claims 1 to 10.