FR2865377A1 - Vertebral osteosynthesis equipment for use in correcting position of vertebrae has polyaxial anchor with nut that is elastically deformable and is interposed between the connecting portion and a bearing surface of the base - Google Patents

Abstract

A polyaxial anchor has a stud (5) articulated with respect to a base enables bone anchoring. A clamp (4) enables assembly of the connecting portion (3) on the anchor. A nut (31) of the polyaxial anchor is elastically deformable and is interposed between the connecting portion and a bearing surface (17,18) of the base (6) to which stud is integrated.

Description

The present invention relates to a vertebral osteosynthesis material.

  A vertebral osteosynthesis material generally comprises bone anchoring members, such as pedicle screws or lamella hooks, one or two connecting rods, intended to be connected to these anchoring members, and connecting pieces of this type. or these connecting rods to these anchoring members. The equipment may also include lengthwise adjustable cross members, which transversely connect two parallel connecting rods to maintain these rods relative to each other.

  In an existing type of material, each anchoring member comprises a threaded proximal pin on which a nut can be screwed, and each connecting piece can be in the form of a stirrup comprising a rounded part intended to surround a connecting rod and two parallel wings pierced with holes. These wings are intended to be engaged on said threaded proximal pin and to be clamped, by means of this nut, against a bearing surface provided on the anchoring member, this tightening causing the tightening of said rounded portion around the connecting rod and thus ensuring the longitudinal immobilization of this rod relative to the anchoring member. The anchoring members and connecting pieces may be of the "monoaxial" type, that is to say not allowing, before clamping, an articulation of the connecting piece with respect to the part intended to be inserted into the os, or may be of "polyaxial" type, that is to say, allowing such a joint before tightening.

  The existing vertebral osteosynthesis devices are intended to immobilize two vertebrae relative to each other, to eliminate any relative movement of these vertebrae, which may be painful, or to restore the proper position of a vertebra relative to to the other. To obtain this immobilization, these materials are designed to ensure a perfectly rigid connection of the connecting rods with the anchoring members.

  This rigid assembly may, however, not be desirable in all cases. It leads in particular to the exercise of significant stresses at the anchoring bone areas of said anchoring members, as well as increased stresses at the vertebral joints located on either side of the treated vertebral segment, which can lead to degeneration of these joints. In addition, it is not suitable for treatment of non-degenerative conditions, including the treatment of scoliosis in young patients.

  The present invention aims to remedy these essential disadvantages.

  The material concerned comprises, in a manner known per se, bone anchoring members, such as pedicle screws or lamella hooks, one or two connecting rods, intended to be connected to these anchoring members, and pieces of connection of this or these rods to these anchoring members, at least one of these anchoring members and these connecting pieces being of the "polyaxial" type, that is to say allowing an articulation of the connection piece relative to the anchoring member, clamping means being provided for immobilizing a connecting rod in the connection piece that receives the anchoring member.

  According to the invention, at least one of said anchoring member and said "polyaxial" type connecting piece comprises at least one part or part part with an elastically deformable structure, interposed, after assembly, between said connecting piece and said anchoring member, this part or part of an elastically deformable structure part allowing a mobility of the connecting piece, and therefore of the connecting rod, relative to the anchoring member, with damping.

  Thus, in the material according to the invention, said connecting piece is not immobilized relative to the anchor member but can play vis-à-vis it, to allow limited movements of the vertebrae . The stresses exerted on the anchor bone areas of the anchoring member are thus significantly reduced, as well as the risk of over-stresses at the vertebral joints located on either side of the treated vertebral segment.

  Said clamping means may be designed to clamp the connecting piece against said workpiece or a workpiece with an elastically deformable structure and to clamp this workpiece or a workpiece against the anchor.

  The play of the connecting piece is then made possible only by the deformation of said part or part of elastically deformable structure part.

  The anchoring member may comprise, if not a surface forming an axial abutment, against which the connection piece comes to rest, said clamping means clamping this connecting piece against this surface.

  The immobilization of the connecting rod relative to the connecting piece is thus performed independently of any clamping of said part or part of elastically deformable part.

  Said part or part of elastically deformable structure part may be shaped so as to achieve a damping of the movement of the connecting piece over the entire travel of the connection piece, in particular by being a compressible material. This part or part part can also be shaped to achieve this damping only in the extreme positions of this movement. According to a possible embodiment of the invention in this second case, said part or part of elastically deformable structure part is formed by a circular wall connected to the connecting piece, this wall comprising at least one transverse slot which passes through it, arranged on one side of this wall in a direction substantially perpendicular to that occupied by a connecting rod when the rod is engaged in the connecting piece, this slot allowing a reduction in the thickness of this circular wall when a constraint is exerted on this wall in the axial direction, on the side where the slot is.

  Advantageously, said circular wall comprises two slots arranged on two of its opposite sides, allowing damping on these two sides.

  The anchoring member may comprise an articulated proximal pin; the walls of the proximal pin and the anchoring member which slide against each other during the movement of this pin may then comprise a smooth and resistant coating, able to withstand many sliding movements of these walls against each other, such as a coating of ceramic or titanium nitride.

  When the articulation of this proximal pin is made by sliding of sphere-shaped faces or spherical portions against each other, these faces advantageously have a diameter much greater than that of the proximal pin, in particular at least double the diameter of this pin, to increase the contact area of its faces with each other.

  The friction is thus exerted on increased surfaces, reducing the risk of wear of said faces.

  According to another possible embodiment of the invention, the material comprises, in addition to the clamping means provided for immobilizing a connecting rod in the connection piece that receives the anchoring member, second clamping means for tightening , independently of the clamping performed by said clamping means, said workpiece or part portion of elastically deformable structure between the connecting piece and the anchoring member.

  Said second clamping means can thus be clamped in a controlled manner, for example by means of a torque screwdriver, according to the degree of damping sought according to the characteristics of the patient (condition of the intervertebral discs, degree of vertebral instability, weight) then said clamping means is tightened to immobilize the rod in the connection piece.

  The material may comprise means forming a mark for identifying different degrees of clamping of said part or part of elastically deformable structure part between the connecting piece and the anchoring member, and thus allow the aforementioned controlled clamping.

  The anchoring member may comprise a part with an elastically deformable structure and the connecting piece may comprise another part with an elastically deformable structure, these two parts coming to bear against each other during the clamping.

  Furthermore, at least one connecting rod of the material may comprise: a rod portion comprising a component with an elastically deformable structure and an articulated pin, - another rod part comprising a zone of support against this part with an elastically deformable structure, and clamping means for clamping this bearing zone against this piece with an elastically deformable structure.

  The connecting rod can thus also have a degree of elastic flexibility.

  Said bearing zone may also include a component with an elastically deformable structure.

  The invention will be better understood, and other features and advantages thereof will appear, with reference to the appended schematic drawing, showing, by way of nonlimiting examples, several embodiments of parts that includes the material that it concerned.

  FIG. 1 is a partial view of a polyaxial pedicle screw and of a connecting rod that comprises this material, and, in cross-section, of a connecting piece and a nut making it possible to assemble a connecting rod to this screw, before assembly; Figure 2 is a view of these parts similar to Figure 1, after assembly; Figure 3 is a view of these parts similar to Figure 2, in a direction perpendicular to that according to Figure 2, in a position; Figure 4 is a view of these parts similar to Figure 3 in a second position; Figure 5 is a view of these parts similar to Figure 3, in a third position; Figure 6 is a view of the same parts in perspective, after placing the screw in a vertebra and before final tightening; Figure 7 is a view of these parts similar to Figure 6, after final tightening; Figure 8 is a view similar to Figure 1 of the same parts of the material, according to a second embodiment, before assembly; Figure 9 is a view similar to Figure 2 of these parts, after mounting; Figure 10 is a partial sectional view of a connecting rod, before assembly; Figure 11 is a view similar to Figure 10, after assembly; Figure 12 is a partial view, in section, of a third embodiment of the invention, including a pedicle screw, a connecting rod, a connection piece shaped "tulip" and a nut to assemble the connecting rod to this connecting piece, and FIG. 13 is a partial view, in section, of a fourth embodiment of the invention, including a polyaxial pedicle screw, a connecting rod, a connection piece and a nut for assembling the connecting rod to this screw.

  FIG. 1 shows a polyaxial pedicle screw 1, a connecting rod 2 of several of these screws 1, a connecting piece 3 of this rod 2 to one of these screws 1 and a nut 4 for assembling the connecting rod. 2 to this screw 1.

  The screw 1 comprises a threaded proximal pin 5 and a threaded distal screw body 6. The pin 5 is intended to receive the piece 3 engaged on it and the nut 4 screwed on it while the body 6 is intended to be inserted in the pedicle of a vertebra, as shown in Figures 6 and 7.

  The pin 5 has a threaded cylindrical portion 10, an enlarged distal head 11 and a flange 12 forming a stop surface.

  The portion 10 has a zone 15 of reduced diameter, making it possible to break its proximal portion after placing and tightening the nut 4, as appears by comparison with FIGS. 2 and 3.

  The head 11 has a double diameter of the diameter of the portion 10 and has a spherical cap shape. This head 11 is intended to be engaged in a proximal cavity 16 delimited by the proximal zone of the body 6 and to be retained in this cavity 16 by crimping a proximal wall 17 that this body 6 presents. After crimping, the wall 17 is shaped to have a hemispherical proximal shape. As it appears in FIG. 1, the dimensions of the cavity 16 and of the opening delimited by the wall 17 after crimping for the passage of the pin 5 are such that a multidirectional movement of this pin 5 with respect to the body 6 is possible. .

  The body 6 also comprises a proximal flange 18 intended to abut against the pedicle 100. This flange 18 has a plurality of radial notches 19, in particular four notches 90 of each other, allowing the body 6 to be held in rotation during tightening. of the nut 4.

  The connecting rod 2 is cylindrical and has a rigidity such that it allows the maintenance of several vertebrae relative to each other.

  This rod 2 is, however, deformable so that it can be shaped according to the correction of the spine to achieve.

  The connection piece 3 comprises a rounded portion 20 intended to surround the connecting rod 2 and two parallel lateral wings 21 pierced with holes for the engagement of the piece 3 on the pin 5. These wings 21 are mutually distant so that in a spacing position, the rod 2 can be inserted and slidable in the part 20, and that, in a position of approximation that confers on them the tightening of the nut 4, they tighten the part 20 around the rod 2, immobilizing the latter with respect to the piece 3.

  As shown in FIGS. 1 and 2, the proximal wing 21 has a proximal bowl 25 of a shape adapted to support the nut 4, whereas the distal wing 21 comprises a circular cavity 26 enabling engagement. of this wing on the collar 12.

  This distal wing 21 further comprises a circular wall 27 integral with it. This wall 27 has a height less than that of the wall 17, and delimits an inner concave spherical face 28 of diameter greater than the diameter of this wall 17.

  In addition, two transverse slots 29 are formed in this wall 27, on two opposite sides of the wall 27, and in a direction substantially perpendicular to that occupied by the connecting rod 2 when the rod is engaged in the rounded portion 20. Each slot 29 extends angularly about 120 of the wall 27 and ends with a widened zone 30 in the form of a circle.

  As can be understood with reference to FIG. 5, the distal portions of the wall 27 delimited by the slots 29 have, at these rounded zones 30, a reduced height, such that these portions can flex at these zones 30, thus allowing a reduction in the height of the wall 27.

  In practice, the number of screws 1 necessary for the treatment to be performed is placed in the pedicles 100 of the vertebrae concerned, then the connecting pieces 3, with the rod 2 engaged in the parts 20, are placed on the pins 5, until The nuts 4 are then tightened to immobilize the rod 2 relative to the parts 3 and the proximal portions of the pins 5 are cut.

  The abutment of each piece 3 against the corresponding flange 12 makes it possible to clamp the rod 2 in this piece 3 independently of any clamping of the piece 3 against the wall 17.

  Once the tightening of the nut 4 has been achieved, the pin 5 thus remains mobile with respect to the body 6, this mobility being free as long as the wall 27 has not come into abutment against the body 6 (see FIG. being possible with deformation of the wall 27 beyond, realizing a damping of the movement of the pin 5 in the maximum angles of movement of this pin. The limit of the possible deflection of the latter corresponds to the coming into contact of the edges of the wall 27 delimiting the slots 29.

  Due to the diameter of its face 28, greater than the diameter of the wall 17, the wall 27 does not obstruct the movement of the pin 5.

  This face 28 may however, as shown in Figure 2, be shaped so as to bear against the substantially hemispherical zone of the wall 17. The friction resulting from this support perform a braking movement of the pin 5, if necessary.

  The sliding zones of the head 11 against the wall 17 and the face 28 against the wall 17 may comprise a smooth and resistant coating, able to withstand very many sliding movements of these walls against each other, such as a coating of ceramic or titanium nitride.

  Figures 8 and 9 show parts 2 to 5 similar to those described with reference to Figures 1 and 2, the parts being identical or similar being designated by the same reference numerals.

  In this case, the flange 18 has a peripheral rim 30 and contains a piece 31 in the form of a washer made of material with an elastically deformable structure, in particular made of silicone or PMMA. In the example shown, the part 3 comprises a similar part 31, these two parts 31 bearing against each other during assembly.

  The part 3 can in this case completely receive a nut 40 in the cavity 25 of its proximal branch 21, this cavity 25 being such that this nut 40 can bear against the distal branch 21 of the part 3 without pressing against the branch 21 proximal.

  The nut 40 has peripheral notches 32 for its rotation operation.

  The material further comprises the nut 4, which can be screwed onto the proximal pin 5.

  In practice, the nut 40 can be clamped in a controlled manner, for example by means of a torque screwdriver, to tighten the parts 31 according to the degree of damping sought according to the characteristics of the patient (state of the intervertebral discs, degree of vertebral instability, weight).

  The nut 4 is then tightened to immobilize the rod 2 in the connection piece 3.

  FIGS. 10 and 11 show a connecting rod 2 of the material which comprises: a part of rod 2a comprising a part 41 with an elastically deformable structure and an articulated threaded pin 5, this articulation being produced in identical manner to that described above, - Another rod portion 2b, comprising a bearing zone 42 against this piece 41 and a tapped bore 43 for screwing this portion 2b on the pin 5 to clamp the bearing zone 42 against the piece 41.

  The connecting rod 2 can thus also have a degree of elastic flexibility.

  Figure 12 shows a pedicle screw 1 comprising a hemispherical head 45 which can be engaged in the connecting piece 3, which has the shape of a "tulip".

  The part 3 comprises a lower hemispherical cavity for receiving the head 45, this cavity allowing the articulation of the part 3 with respect to the screw 1.

  The part 3 further comprises notches for receiving the rod 2 and forms bearing surfaces for it, and an upper thread for screwing a threaded plug 46 immobilizing the rod 2 in it.

  Under the head 45, the screw 1 comprises a thread on which can be screwed a support flange 18 of a workpiece 31, this workpiece 31 being compressed by the connection piece 3 when this workpiece 3 is inclined with respect to the screw 1 and thus allowing the damping of the movement of this piece 3.

  FIG. 13 shows a screw 1 as described with reference to FIG. 1, a part 3 similar to that described with reference to this FIG. 1 but without the wall 27, a part 31 in the form of a washer a material having an elastically deformable structure, in particular made of silicone or PMMA, a rigid washer 50, in particular a metal washer, having a threaded bore allowing it to be screwed onto the pin 5 until clamping the piece 31 between it and the part 6 of the screw, and a nut 4 as described with reference to FIG.

  The washer 50 can be screwed on the pin 5 until a clamping of the piece 31 according to the desired damping. Once this tightening obtained, the part 3, with the rod 2 engaged in it, is placed on the pin 5 and the nut 4 is tightened so as to immobilize the rod relative to the part 3.

  As is apparent from the foregoing, the invention provides a vertebral osteosynthesis material allowing limited play of the connecting piece 3, and therefore of the connecting rod 2, with respect to the anchoring member 1 to the vertebra, to allow limited movements of the treated vertebrae.

  The stresses exerted on the anchoring bone areas of the anchoring member are thus significantly reduced, as well as the risk of overstressing of the vertebral joints located on either side of the treated vertebral segment.

  It goes without saying that the invention is not limited to the embodiment described above by way of example but that it extends to all embodiments covered by the appended claims. Thus, it would not depart from the scope of the invention by replacing the wall 27 with a washer of elastic material or elastic structure, for example in the form of a spring.

Claims (9)

  A vertebral osteosynthesis material, comprising bone anchoring members, such as pedicle screws (1) or lamella hooks, one or two connecting rods (2), intended to be connected to these anchoring members and to to be attached to the vertebrae by means of these, and connecting pieces (3) of this or these rods (2) to these anchoring members, at least one of these anchoring members and connecting pieces ( 3) being of the "polyaxial" type, that is to say allowing articulation of the connection piece (3) with respect to the anchoring member, clamping means (4) being provided for immobilizing a rod link (2) in the connecting piece (3) that receives this anchor member; material characterized in that at least one of said anchoring member (1) and said connecting piece (3) of "polyaxial" type comprises at least one part or part part (27) with elastically deformable structure, interposed , after mounting, between said connecting piece (3) and said anchoring member (1), this piece or part part (27, 31) with elastically deformable structure allowing a mobility of the connecting piece (3), and therefore the connecting rod (2), with respect to the anchoring member (1), with damping.   2 Equipment according to claim 1, characterized in that the anchoring member (1) comprises a surface (12, 50) forming an axial abutment, against which the connecting piece (3) rests, said clamping means ( 4) clamping this connection piece (3) against this surface (12).   3 Material according to claim 1 or claim 2, characterized in that said piece (31) or part of elastically deformable structure part is shaped so as to achieve a damping of the movement of the proximal pin over the entire movement of this piece .   4 Equipment according to claim 1 or claim 2, characterized in that said part or part part (27, 31) with elastically deformable structure is shaped so as to damp the movement of the connection piece (3) only in the extreme positions of the travel of this connection piece.     Equipment according to claim 4, characterized in that said workpiece or part portion with an elastically deformable structure is formed by a circular wall (27) connected to the connecting piece (3), this wall (27) comprising at least one transverse slot (29) which passes therethrough, arranged on one side of this wall (27) in a direction substantially perpendicular to that occupied by a connecting rod (2) when this rod is engaged in the connection piece (3), this slot (29) allowing a reduction of the thickness of this circular wall (27) when a stress is exerted on the wall in the axial direction, the side where the slot (29) is.   6. Material according to claim 5, characterized in that said circular wall (27) comprises two slots (29) arranged on two of its opposite sides, allowing damping on both sides.   7 Material according to one of claims 1 to 6, characterized in that the anchoring member (1) comprises an articulated proximal pin (5), and in that the walls (11, 17) of this proximal pin ( 5) and the anchoring member (1) which slide against each other during the movement of this pin (5) comprise a smooth and resistant coating, able to withstand very many sliding movements of these walls against each other, such as a ceramic coating or titanium nitride.   8 Equipment according to claim 7, characterized in that the articulation of said proximal pin (5) is effected by sliding faces (11, 17) in the form of a sphere or portions of sphere against each other, and these faces (11, 17) have a diameter much greater than that of the proximal pin, in particular at least twice the diameter of this pin.   9 material according to one of claims 1 to 8, characterized in that it comprises, besides the clamping means (4) provided for immobilizing a connecting rod (2) in the connecting piece (3) that receives the anchoring member (1), second clamping means (40, 50) for clamping, independently of the clamping action performed by said clamping means (4), said workpiece or part portion with an elastically deformable structure (31) between the connecting piece (3) and the anchoring member (1).     Material according to one of claims 1 to 9, characterized in that it comprises means forming a mark for identifying different degrees of clamping of said part or part of elastically deformable structure structure between the connecting piece and the body of anchor.   11. Material according to one of claims 1 to 10, characterized in that at least one connecting rod comprises: - a rod portion having a resiliently deformable structural piece and an articulated pin, - another rod portion comprising a bearing zone against this piece of elastically deformable structure, and - clamping means for clamping the bearing surface against this piece 10 elastically deformable structure.