WO2009069025A2

WO2009069025A2 - Vertebral osteosynthesis material

Info

Publication number: WO2009069025A2
Application number: PCT/IB2008/054605
Authority: WO
Inventors: Denys Sournac; David Ryan
Original assignee: Medicrea International
Priority date: 2007-11-30
Filing date: 2008-11-05
Publication date: 2009-06-04
Also published as: FR2940041B1; FR2924326B1; FR2924326A1; FR2940041A1; WO2009069025A3

Abstract

This material comprises at least one bone anchoring member (2) whereof a proximal part (10) is connected to a flexible cord (15) serving to guide other members (4, 5), in particular to guide a connection yoke enabling the connection of the bone anchoring member (2) to a rod connecting several bone anchoring members to each other. According to the invention, the material comprises stop means (6) able to engage against one of said other members (4, 5) when these other members (4, 5) are engaged on the flexible cord (15), these stop means (6) being equipped with anti-reversing means (20) presenting an obstacle to their movement along the flexible cord (15) in the direction moving away from the bone anchoring member (2).

Description

VERTEBRAL OSTEOSYNTHESIS MATERIAL

The present invention concerns a vertebral osteosynthesis material. It also concerns an assembly comprising this vertebral osteosynthesis material and advancement means, in particular in the form of an instrument, making it possible to advance the stop means comprised by the material. The invention also concerns a vertebral osteosynthesis method using said vertebral osteosynthesis material or said assembly.

It is well known to perform a vertebral osteosynthesis using a material including anchoring screws in the vertebrae, bars connecting the vertebrae to each other and members connecting these bars to the screws. These connection members comprise in particular yokes intended to be engaged on the connecting bars and on threaded proximal slugs comprised by the screws. These proximal slugs can be fixed in relation to the bodies of the screws (screws then called "monoaxial"), or can be articulated in relation to these screw bodies (screws then called "polyaxial"). Document WO 98/55038 illustrates one example of vertebral osteosynthesis material of this type.

Also known from documents US 2004/147928 and US 2005/043742 is a vertebral osteosynthesis material comprising at least one screw whereof the proximal part is connected to a flexible cord having a length such that it is able to extend, from the implantation site, to a location outside this implantation site. This flexible cord serves to guide other members in the direction of the screw, in particular to guide a connection yoke allowing the connection of the screw to a connecting rod of several members anchoring bones to each other.

These materials make it possible to resolve the drawbacks presented by the known vertebral osteosynthesis materials, in particular the cluttering up of the operating field by the rigid guide rods comprised by these known materials, or the need to break the exceeding parts of threaded proximal slugs comprised by the bone screws used.

These materials do, however, have the drawback of not progressively performing a correction of the position of the treated vertebrae. Indeed, to perform the osteosynthesis, the screws are placed in the pedicles of the vertebrae, then the yokes or other connecting pieces are engaged on the proximal slugs of the screws and nuts are placed. The correction of the position of the vertebrae is done progressively, performing progressive placements of the yokes and nuts on these proximal slugs, the lengths of which are reduced, then performing successive partial tightening of the nuts.

The progressive nature of the assembly of the yokes and nuts on the threaded proximal slugs is limited to the length of these threaded proximal slugs, which can hinder the placement of the material or make it difficult in certain cases, in particular given the correction of the spinal cord to be done.

The present invention aims to resolve this essential drawback.

The material it concerns comprises, in a known manner, at least one bone anchoring member whereof one proximal part is connected to a flexible cord serving to guide other members comprised by the material in the direction of the bone anchoring member, in particular to guide a connection nut enabling the connection of the bone anchoring member to a connecting rod of several members anchoring bones to each other, this flexible cord having a length such that it is able to extend, from the implantation site, up to a location located outside this implantation site.

According to the invention, the material comprises stop means able to be engaged on the flexible cord and to bear against one of said other members when these other members are engaged on the flexible cord, these stop means being able to be moved along the flexible cord in the direction of the bone anchoring member and being equipped with anti-reversing means forming an obstacle to their movement along the flexible cord in the direction moving away from this bone anchoring member.

The material thus formed makes it possible to cause said other members to advance along the flexible cord only in the direction coming closer to the bone anchoring member; it thus makes it possible to perform a vertebral osteosynthesis with progressive placement of one or two connecting rods on a series of bone anchoring members connected to a series of vertebrae. Indeed, all of the length of a flexible cord can be put to use to cause said other members to advance progressively toward a bone anchoring member. The placement of such a vertebral osteosynthesis material is thus greatly facilitated.

According to another embodiment of the invention, the stop means comprise at least one piece defining a passage for its engagement on the flexible cord and teeth, claws, sharp protrusions or similar not presenting an obstacle to the movement of the piece along the flexible cord in the direction coming closer to the bone anchoring member, and penetrating into the material of the flexible cord when the stop means tend to be moved along the flexible cord in the direction of separation of the bone anchoring member.

According to another embodiment of the invention, the stop means comprise a piece comprising a passage for its engagement on the flexible cord and at least one mobile jaw, movable between a withdrawn position, in which this mobile jaw does not present an obstacle to the progress of the stop means along the flexible cord, and an active position, in which this mobile jaw grips the flexible cord between it and a wall located across from it, and thus prevents the sliding of the stop means in the direction of separation from the bone anchoring member.

Preferably, in this case, the stop means comprise two mobile jaws arranged on both sides of the passage receiving the flexible cord.

Each mobile jaw can in particular comprise teeth, claws, sharp protrusions or similar, intended to penetrate into the material of the flexible cord when the stop means tend to be moved in the direction of separation from the bone anchoring member, and, in so doing, bringing each mobile jaw into the active position.

The connection of said bone anchoring member and the flexible cord can be done using any suitable means. It may involve a non-reversible connection other than by cutting the flexible cord, in particular a connection by crimping of a wall which may be comprised by the bone anchoring member, or by engagement of the flexible cord through the bone anchoring member and arrangement of a stop means at the end of the flexible cord having gone through this bone anchoring member. This stop means can be a stop piece connected to this end or a knot realized at this end.

Preferably, however, the connection of said bone anchoring member and the flexible cord is removable other than by cutting of the flexible cord. In particular, this connection can be realized by screwing of a threaded tip comprised by the flexible cord in a threaded zone corresponding to the bone anchoring member.

The end of the flexible cord opposite that connected to said bone anchoring element can comprise a rigid member, such as a needle, facilitating the engagement of said other members on the flexible cord.

Preferably, the material is part of an assembly comprising advancement means, making it possible to advance said stop means along the flexible cord.

These advancement means thereby make it possible to advance said other members in the direction coming closer to the bone anchoring member. According to one possibility, in this case, the advancement means can be in the form of an instrument comprising a first part able to be selectively engaged at said bone anchoring member and a second part able to be selectively engaged with said stop means, said first part and said second part being movable in relation to each other.

The first part and the second part are brought into a separated position, then are engaged respectively with the bone anchoring member and with the flexible cord; they are then brought closer to each other, thereby performing a movement of said other members along the flexible cord. According to another possibility, the advancement means and said stop means are in the form of an instrument comprising a first stop means able to be selectively engaged at said other members and a second stop means able to be selectively engaged with the flexible cord, these first and second stop means being movable in relation to each other. The first and second stop means are brought into a close together position, then are brought respectively into engagement with said other members and with the flexible cord; the first and second stop means are then distanced from each other, realizing the movement of said other members along the flexible cord.

Said instrument can be in the form of a clamp with two pivoting branches, each equipped with a stop means as previously cited; the pivoting of the branches in the direction bringing the two stop means closer to each other leads a first of these two stop means to be immobilized relative to the flexible cord and the second stop means to advance along the flexible cord, and the consecutive pivoting of these branches in the direction of the separation of the two stop means leads to immobilizing said second stop means in relation to the flexible cord and allowing said first stop means to advance along the flexible cord.

The invention also relates to a vertebral osteosynthesis method using said vertebral osteosynthesis material or said assembly.

This method is essentially characterized by the following steps: - implant, into a vertebra, at least one bone anchoring member which comprises the vertebral osteosynthesis material;

- engage said other members on said flexible cord;

- then engage said stop means on said flexible cord; - move these stop means along the flexible cord in the direction bringing them closer to the bone anchoring member, so as to progressively bring said other members closer to said bone anchoring member, until an assembly position of said other members on the bone anchoring member; - withdraw said flexible cord and said stop means.

Preferably, the method comprises the following steps:

- implant, into a plurality of vertebrae, a plurality of bone anchoring members comprised by the vertebral osteosynthesis material;

- engage a group of said other members, then a group of said stop means on the flexible cord of each bone anchoring member;

- move the group of stop means along the flexible cord of a first bone anchoring member so as to move the group of said other members toward this first bone anchoring member;

- move the group of stop means along the flexible cord of at least one second bone anchoring member so as to move the group of said other members toward this second bone anchoring member;

- again move the group of stop means of the first bone anchoring member so as to move the group of said other members toward the first bone anchoring member;

- again move the group of stop means of the second bone anchoring member so as to move the group of said other members toward this second bone anchoring member;

- repeat the two operations above as many times as necessary to bring the respective groups of said other members into said assembly position.

Preferably, the method comprises a step consisting of using advancement means to advance said respective stop means or groups of stop means along the respective flexible cord(s).

Preferably, the method comprises the steps of:

- using an instrument forming said advancement means, comprising a first part able to engage at a bone anchoring member and a second part able to engage at said stop means, these first and second parts being movable in relation to each other;

- engaging said first part with said bone anchoring member and engaging said second part with said stop means; and - realizing, using said instrument, the movement of the stop means and of said other members along the flexible cord up to said assembly position.

Preferably, the method comprises the steps of:

- using an instrument forming said stop means and said advancement means, comprising a first stop means able to engage with one of said other members and a second stop means able to engage with the flexible cord, these first and second stop means being movable relative to each other;

- engaging said first stop means with one of said other members and said second stop means with the flexible cord; - realizing, using said instrument, the movement of said other members along the flexible cord to said assembly position.

The invention will be well understood, and other characteristics and advantages thereof will appear, in reference to the appended diagrammatic drawing, illustrating, as non-limiting examples, several possible embodiments of the material it concerns. Figure 1 is a cross-sectional view of various members comprised by this material according to one embodiment; figure 2 is a partial view, from the side, of a screw which is part of these members; figure 3 illustrates a vertebra on which are implanted, in the left part of the figure, a material according to the prior art, and in the right part of the figure, members of the material according to the invention; figure 4 is a side view of a bone anchoring member comprised by the material, according to another embodiment; figure 5 is a cross-sectional view of the screw comprising the bone anchoring member shown in figure 4; figure 6 is a view similar to figure 5 of a screw according to still another embodiment; figure 7 is a view of a stop means comprised by this material, according to another embodiment, and figures 8 and 9 are partial views of an instrument which may be comprised by the material.

For simplification, the parts or elements of one embodiment which are found identically or similarly in another embodiment will be identified by the same numerical references and will not be described again. Figure 1 illustrates a set 1 of different members comprised by a vertebral osteosynthesis material, namely a pedicular screw 2, a connecting bar 3, a yoke 4 for connection of this bar 3 and this screw 2, a nut 5 for assembling the yoke 4 on the screw 2 and a stop piece 6.

The screw 2 is of the so-called "polyaxial" type, i.e. comprises a threaded proximal slug 10 articulated in relation to a screw body 11. In the illustrated example, this articulation is realized using a sphere 12 integral with the slug 10, which is received in a corresponding spherical housing defined by a wall 13 integral with the screw body 11. The retention of the sphere 12 in said housing is done by crimping of this wall 13 on the sphere 12.

As appears, the proximal end of the slug 10 (i.e. that opposite the sphere 12), is connected to a flexible cord 15, coaxially thereto, this connection being realized by crimping of this flexible cord 15 of a circular wall 16 comprised by this proximal end. The flexible cord 15 is deformable in the transverse direction, i.e. perpendicular to its length, non-elastically. In the illustrated example, this flexible cord 15 is in the form of a cord in a textile material, in particular in braided polyester. This flexible cord 15 has a length such that it is able to extend, from the implantation site, up to a location located outside this implantation site. At its end opposite the slug 10, the cord 15 comprises a needle 17, coaxially connected to it. The connection of the cord 15 to the needle 17 is done by crimping on this cord of a circular wall 18 comprised by the end of this needle.

The connecting bar 3 is intended to connect several vertebrae to each other.

The yoke 4 comprises a rounded part for receiving the bar 3 and two branches pierced with holes for its sliding engagement on the cord 15. It is intended to rest against the wall 11 , being gripped against said wall by the nut 5, intended to be screwed on the slug 10.

This bar 3, this yoke 4 and this nut 5 are well known elements and are not part of the invention in themselves. Reference may be made to document WO 98/55038, which describes similar members, for more ample details concerning them.

The stop piece 6 is, in the embodiment shown in figure 1 , made up by a single piece in the form of a sphere, pieced all the way through by a hole allowing the straight engagement of this piece 6 on the cord 15. The piece 6 comprises, at this hole, teeth, claws, sharp projections 20 or similar, not presenting an obstacle to the movement of the piece 6 along the cord 15 in the direction of the slug 10 and penetrating into the material of the cord 15 when the piece 6 tends to be moved along this cord 15 in the direction opposite the slug 10.

The piece 6 is able to be engaged against the nut 5 when the yoke 4 and said nut 5 are engaged on the cord 15, and to make it possible to progressively bring said yoke 4 and said nut 5 closer to said slug 10, without possibility of withdrawal of the yoke 4 and the nut 5 in relation to the slug 10.

Figure 3 shows a vertebra 100 and the surrounding tissue 101 which have been removed to reveal the pedicles 102 of this vertebra and the adjacent vertebrae. In the left part of the figure, is illustrated a polyaxial screw 2A according to the prior art, comprising a threaded proximal slug 10A having a length clearly greater than that necessary for mounting of the nut. This slug 10A receives an extension rod 5OA which makes it possible to secure the introduction of the yoke and the nut intended to be mounted on the slug 10A. The osteosynthesis being done on several consecutive vertebrae 100, the operating field is in particular cluttered by the extension rods 5OA given the reduced travel of the proximal slugs 10A.

The cords 15 of the screws 2 according to the invention make it possible to secure the introduction of yokes 4 and nuts 5 as well as the extension rods 5OA but, thanks to their substantially non-elastic transverse deformability, can be moved in the operating field, in order to free a particular zone thereof. They can in particular be pressed against the tissue 101 as illustrated.

Moreover, the length of the slugs 10 is just sufficient for the mounting of the yokes 4 and nuts 5, which eliminates the need, with the material according to the prior art, to break the parts of the proximal slugs 10A exceeding the nuts 5 after assembly. Other than the elimination of the additional operations involved by the realization of these breaks, the material according to the invention makes it possible to eliminate the undesired stresses exerted on the anchohngs of the screws 2 during these breaks.

Moreover, the progress nature of the assembly of the yokes 4 and nuts 5 on the slugs 10A of the material according to the prior art is limited to the length of these slugs 10A, which can hinder the placement of the material or make it difficult in certain cases, or lead to the exertion of substantial stresses on the anchohngs of the screws upon connection of the yokes to the slugs 10A. On the contrary, with the material according to the invention, all of the lengths of the cords 15 can be put to use to guide the yokes 4 and the nuts 5 toward the slugs 10, the pieces 6 making it possible to gradually bring these yokes 4 and nuts 5 onto these slugs 10, closer and closer, during the correction of the position of the vertebrae 100. The cords 15 are, after assembly, easily severed at the slugs 10. Figure 4 shows another embodiment of the connection of the proximal end of a slug 10 and a cord 15. In this case, the sphere 12 is in two hemispheres 12a, 12b, one of which is adjacent to the slug 10, and the slug 10 and this hemisphere 12a are pierced by an axial bore for the engagement of the cord 15; the other hemisphere 12b comprises a circular wall able to be crimped on the end of the cord 15 and to be engaged in the distal portion of said bore. The two hemispheres 12a, 12b can thus be brought side by side in the assembled position (cf. figure 5), making it possible to form the sphere 12.

Figure 6 shows still another embodiment of the connection of the proximal end of a slug 10 with a cord 15. In this case, the slug 10 is adjacent to a proximal hemisphere 12a, and this slug 10 and this hemisphere 12a are pierced with an axial bore for the engagement of the cord 15; a knot 21 is realized at the distal end of the cord 15 to maintain the cord 15 in said bore.

Figure 7 shows another embodiment of the stop piece 6 which may be comprised by the material according to the invention. In this case, the piece 6 comprises two mobile jaws 25 located on both sides of the engagement passage on the cord 15, mounted pivoting around pivots 26. As is understood, these jaws 25 can be moved between withdrawn positions, shown in broken lines, in which they do not present an obstacle to the advancement of the piece 6 along the cord 15, and active positions, shown in solid lines, in which they grip the cord 15 between them and thereby prevent sliding of the piece 6 in the direction opposite the slug 10.

According to another possibility, illustrated in figures 8 and 9, the material according to the invention comprises an instrument making it possible to advance a stop piece 6 as shown in figure 1 along the cord 15. This instrument is in the form of a clamp with two pivoting branches 27, each equipped with a stop assembly 6a, 6b as shown in figure 7; the pivoting of the branches 27 in the direction bringing the two stop assemblies 6a, 6b closer toward each other (cf. figure 8) leads a first stop assembly 6a to be immobilized relative to the cord 15 and the second stop assembly 6b to advance along the cord 15; the consecutive pivoting of these branches 27 in the direction distancing the two stop assemblies 6a, 6b (cf. figure 9) leads to immobilizing said second stop assembly 6b relative to the cord 15 and allows said first stop assembly 6a to advance along the cord 15.

As appears from the preceding, the invention provides a surgical material, in particular a vertebral osteosynthesis material, having determining advantages relative to the similar materials of the prior art.

The invention was described above in reference to different embodiments provided purely as examples. It goes without saying that it is not limited to these embodiments but that it extends to all embodiments covered by the appended claims. In particular, the term "flexible cord" must be understood in the broadest possible sense, covering any suitable threadlike flexible cord, able to have a braided structure as described above but also a single-thread structure, or able to be a cable.

Claims

1 - A vertebral osteosynthesis material, comprising at least one bone anchoring member (2) whereof a proximal part (10) is connected to a flexible cord (15) serving to guide other members (4, 5) comprised by the material in the direction of the bone anchoring member (2), this flexible cord having a length such that it is able to extend, from the implantation site, to a location located outside this implantation site; characterized in that it comprises stop means (6) able to be engaged on the flexible cord and to bear against one of said other members (4, 5) when these other members (4, 5) are engaged on the flexible cord (15), these stop means (6) being able to be moved along the flexible cord (15) in the direction of the bone anchoring member (2) and being equipped with anti-reversing means (20) presenting an obstacle to their movement along the flexible cord (15) in the direction moving away from the bone anchoring member (2).

2 - The material according to claim 1 , characterized in that the stop means (6) comprise at least one piece comprising a passage for its engagement on the flexible cord (15) and teeth, claws, sharp projections (20) or similar not presenting an obstacle to the movement of the piece (6) along the flexible cord (15) in the direction coming closer to the bone anchoring member (2), and penetrating into the material of the flexible cord (15) when the stop means (6) tend to be moved along the flexible cord (15) in the direction moving away from the bone anchoring element (2).

3 - The material according to claim 1 , characterized in that the stop means comprise a piece (6) comprising a passage for its engagement on the flexible cord (15) and at least one mobile jaw (25), movable between a withdrawn position, in which this mobile jaw (25) does not present an obstacle to the advancement of the stop means (6) along the flexible cord (15), and an active position, in which this mobile jaw (25) grips the flexible cord (15) between it and a wall located across from it, and thus prevents the sliding of the stop means (6) in the direction moving away from the bone anchoring member (2).

4 - The material according to claim 3, characterized in that the stop means (6) comprise two mobile jaws (25) arranged on both sides of the passage receiving the flexible cord (15).

5 - The material according to claim 3 or claim 4, characterized in that each mobile jaw (25) comprises teeth, claws, sharp projections (20) or similar, intended to penetrate the material of the flexible cord (15) when the stop means (6) tend to be moved in the direction away from the bone anchoring member (1 ) and, in so doing, bringing each mobile jaw (25) into the active position.

6 - The material according to one of claims 1 to 5, characterized in that the connection of said bone anchoring member (10) and the flexible cord (15) is removable other than by cutting of the flexible cord (15), this connection being in particular realized by screwing of a threaded tip comprised by the flexible cord (15) into a corresponding threaded zone of the bone anchoring member (10).

7 - The material according to one of claims 1 to 6, characterized in that the end of the flexible cord (15) opposite that connected to said bone anchoring member (10) comprises a rigid member (17), such as a needle, facilitating the engagement of said other members (4, 5) on the flexible cord (15).

8 - An assembly comprising a vertebral osteosynthesis material according to one of claims 1 to 7, characterized in that it comprises advancement means, making it possible to advance said stop means along the flexible cord.

9 - The assembly according to claim 7, characterized in that the advancement means are in the form of an instrument comprising a first part able to engage selectively at said bone anchoring member and a second part able to selectively engage at said stop means, said first part and said second part being movable in relation to each other.

10 - The assembly according to claim 8, characterized in that it comprises an instrument including a first stop means able to be selectively engaged at said other members and a second stop means able to be selectively engaged with the flexible cord, these first and second stop means being movable relative to each other. 11 - The assembly according to claim 10, characterized in that said instrument is in the form of a clamp with two pivoting branches (27), each equipped with a stop means (6a, 6b); the pivoting of the branches (27) in the direction bringing the two stop means (6a, 6b) closer toward each other leads a first stop means (6a) to be immobilized relative to the flexible cord (15) and the second stop means (6b) to advance along the flexible cord (15), and the consecutive pivoting of these branches (27) in the direction separating the two stop means (6a, 6b) leads to immobilizing said second stop means (6b) relative to the flexible cord (15) and enabling said first stop means (6a) to advance along the flexible cord (15). 12 - A vertebral osteosynthesis method using said vertebral osteosynthesis material or said assembly according to one of claims 1 to 11 , characterized in that it comprises the following steps:

- implant, in a vertebra, at least one bone anchoring member comprised by the vertebral osteosynthesis material;

- engage said other members on said flexible cord;

- then engage said stop means on said flexible cord;

- move these stop means along the flexible cord in the direction bringing them closer to the bone anchoring member, so as to progressively bring said other members closer to said bone anchoring member, until an assembly position of said other members on the bone anchoring member;

- withdraw said flexible cord and said stop means.

13 - The vertebral osteosynthesis method according to claim 12, characterized in that it comprises the following steps: - implant, in a plurality of vertebrae, a plurality of bone anchoring members comprised by the vertebral osteosynthesis material;

- engage a group of said other members then a group of said stop means on the flexible cord of each bone anchoring member;

- move the group of stop means along the flexible cord of at least one second bone anchoring member so as to move the group of said other members toward this second bone anchoring member; - again move the group of stop means of the first bone anchoring member so as to move the group of said other members toward the first bone anchoring member;

- again move the group of stop means of the second bone anchoring member so as to move the group of said other members toward this second bone anchoring member; - repeat the two operations above as many times as necessary to bring the respective groups of said other members into said assembly position.

14 - The vertebral osteosynthesis method according to claim 12 or claim 13, characterized in that it comprises the step of using the advancement means to advance said respective stop means or groups of stop means along the respective flexible cord(s).

15 - The vertebral osteosynthesis method according to claim 14, characterized in that it comprises the following steps: - use an instrument forming said advancement means, comprising a first part able to engage at a bone anchoring member and a second part able to engage at said stop means, these first and second parts being movable relative to each other;

- bring said first part to engage with said bone anchoring member and said second part to engage with said stop means; and - realize, using said instrument, the movement of the stop means and of said other members along the flexible cord to said assembly position.

16 - The vertebral osteosynthesis method according to claim 14, characterized in that it comprises the following steps:

- use an instrument forming said stop means and said advancement means, comprising a first stop means able to engage with one of said other members and a second stop means able to engage with the flexible cord, these first and second stop means being movable relative to each other;

- bring said first stop means to engage with one of said other members and said second stop means to engage with the flexible cord; - realize, using said instrument, the movement of the other said members along the flexible cord to said assembly position.