Adjustable osteosynthetic system of the rachis and positioning tool

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DESCRIPTION

Spinal osteosynthesis system with position regulation and positioning tools.

The invention relates to osteosynthesis systems for the spine and to positioning tools for such systems.

According to document FR-2 659 546, an osteosynthesis system for the spine is known which comprises several pedicle screws intended to be anchored in vertebrae of the spinal column and a connecting rod adapted to rigidly join the pedicle screws between them. Said system is used in particular in the case of a single or multiple fracture of one or more vertebrae of the spine. The fracture may have different configurations and require corrective movements to rediscover the original morphology of the spine, in particular as regards the curvatures of lordosis or kyphosis. To this end, each pedicle screw comprises a spherical ring slid on the stem and housed in a recess in the head of the pedicle screw, being free to move in this recess. After anchoring the screws in the vertebrae, each pedicle screw can therefore be placed in any position on the stem and according to any orientation with respect to the stem. The head of the screw comprises a pin that allows the screw, ring and stem to be rigidly immobilized together to rigidly fix the screw to the stem in the desired position. This system therefore allows the pedicle screws to slide relative to each other (distraction movement) and to orient them relatively (angular correction), in order to put the vertebrae back in the desired position for osteosynthesis before rigid fixation of the the screws to the stem. However, this system, which facilitates the distraction movements of the pedicle screws, does not allow an easy regulation of the spacing and angular orientation of the pedicle screws relative to each other.

DE-91 12466 presents a positioning tool for an osteosynthesis device. This tool comprises two arms adapted to be applied on two pedicle screws so that they constitute extensions of these. It also includes an arm connecting member that extends from one arm to the other. This member has two threaded rods that cooperate by screw-nut connections with the arms. A maneuver of the connecting member makes it possible to vary the distance between the arms and, in cooperation with the screw connecting member, to vary the relative inclination of the screws. However, this device has the drawback that the maneuvering of the threaded member is relatively long to carry out, in particular when it is desired to produce a large variation in the distance between the arms. Furthermore, this long maneuver requires from the operator numerous manipulations on the journey, in particular repeated rotations of the connecting member of the arms. All these manipulations can generate stresses transmitted to the vertebrae.

An object of the invention is to provide a tool that allows the relative position of the arms to be varied more quickly while avoiding transmitting undesirable stresses to the vertebrae.

In view of achieving this objective, a positioning tool is provided according to the invention for an osteosynthesis system for a spinal column comprising two anchoring members each adapted to be anchored in a vertebra of the spine, and a connecting element of elongated anchoring adapted to join the anchoring members together, the system being adapted to have a non-interlocked configuration in which each anchoring member is movable in rotation with respect to the anchoring connection element about a first axis perpendicular to a longitudinal direction of the anchoring member and perpendicular to a longitudinal direction of the anchor joint element, and an interlocked configuration in which each anchor member is rigidly fixed to the anchor joint element, the tooling comprising two arms adapted to be removably fixed to the two respective anchoring members and an elongated arm joining element adapted to join together a part of each arm, the arm joining element being adapted to join the parts of arms defining an end of mutual separation of the arm parts, the arm connecting element comprising at least one rack having teeth adapted to mesh with one of the arm parts, the or each rack being fixed in rotation to the other arm part.

Thus, the rack makes it possible to vary the distance between the two arm parts connected by the rack very quickly. To do this, it is sufficient to maneuver the rack to interrupt its engagement with one of the arms, and then modify the relative position of the arms and put the rack back into engagement with this arm. Prolonged maneuvering of the tool is avoided. In this way, numerous and repeated manipulations are avoided and the risk that regulation efforts are transmitted to the vertebrae is reduced. The rack can be very easily put into or out of engagement with the arm.

The invention provides a tool that allows a precise regulation of the spacing and the angular orientation of the pedicle screws relative to each other to be easily carried out. Furthermore, the anchoring connection element makes it possible in particular to carry out the distraction movements of the anchoring members and to fix the gap between first parts of the members attached to this connection member. The arm connecting element makes it possible to limit the separation between the arm parts. Since the relative angular orientation of the anchoring members results from the choice of the spacing between the first parts of the anchoring members and the choice of the spacing between the arm parts, the relative angular orientation can be easily and precisely chosen of the anchoring members. Also, the mutual spacing between the anchoring members can easily be precisely adjusted.

Advantageously, the arm connecting element is adapted such that, when it defines the end, it allows a relative displacement of the arm parts in a single direction of displacement.

Advantageously, the arm connecting element is adapted such that, when defining the end, each arm is movable in rotation with respect to the arm connecting element about a second axis parallel to the first axis.

Advantageously the extreme is a maximum.

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Advantageously, the or each rack is arranged so that the teeth extend in the direction of the anchoring members when the arm parts are connected by the rack.

Advantageously, the or each rack is movable in sliding with respect to the arm to which it is attached, along the second associated axis.

Advantageously, the arm portion adapted to engage with the or each rack has, for the or each rack, an area adapted to engage with the rack and which has a width greater than a width of the rack.

Advantageously, the arm that supports the or each rack comprises means for returning the rack or racks to a position corresponding to the engagement of the teeth with the other part of the arm.

Advantageously, the arm connecting element comprises two racks rigidly fixed to each other, coplanar, parallel to each other, having teeth that extend in the same direction and adapted to extend on either side of the arm with the which are coupled.

Advantageously, each arm is adapted to be movable in rotation with respect to the associated anchoring member around a longitudinal axis of the anchoring member.

Advantageously, each anchoring member comprises means for locking the anchoring member in position on the anchoring connection element, the associated arm having an opening for actuation of the locking means when the arm is fixed on the anchoring member.

Advantageously, each arm has a flat external face adapted to extend in front of the other arm when the arms are joined by the arm connecting element, this face being adjacent to a free end of the arm opposite the anchoring member and inclined with respect to a longitudinal axis of the arm, so that the arm has a width that narrows in the direction of this free end.

Advantageously, it comprises a manual tool for mutually moving towards or away from each other respective parts of the anchoring members or of the arms joined by joining elements.

Also provided according to the invention is a set for the osteosynthesis of the spine comprising an osteosynthesis system comprising two elongated anchoring members each adapted to be anchored in a vertebra of the spine, and an adapted elongated anchoring connecting element to connect the anchoring members together, the system being adapted to have a non-interlocked configuration in which each anchoring member is movable in rotation with respect to the anchoring connection element about a first axis perpendicular to a longitudinal direction of the anchoring member and perpendicular to a longitudinal direction of the anchor joint element, and an interlocked configuration in which each anchor member is rigidly fixed to the anchor joint element, the assembly further comprising a tooling according to the invention.

Advantageously, the anchoring connection element is adapted so that in the unlocked configuration each anchoring element is movable in sliding along the anchoring connection element.

Advantageously, the anchoring connection element comprises a rod and each arm has at least one recess for the passage of the rod, the recess having a width greater than a diameter of the rod.

Other characteristics and advantages of the invention will also appear in the description that follows of a preferred embodiment given by way of non-limiting example. In the attached plans:

Figure 1 is a perspective view of the system according to the invention once installed, the vertebrae not being represented;

figure 2 is an analogous view showing the installation of the system of figure 1, with the distractor clip;

figure 3 and figure 4 are views from the rear and from the left of the rack tube of figures 1 and 2;

figure 5 is a partial sectional view on an enlarged scale of the rack tube of figure 4, showing the shaft and associated spring in a section perpendicular to the axis of the shaft;

Figures 6 and 7 are views from above of the rack tube of Figure 4, showing different positions in translation of the arm connecting element with respect to the associated tube along the axis of the shaft; Y

- Figures 8 and 9 are views of the rear and left of the return tube of Figures 1 and 2.

The osteosynthesis equipment of the invention comprises two sets such as that which will be described with reference to the figures, including two systems intended to be fixed, for example, to the same vertebrae of the spine, on either side of the median axis of the spine. .

The system comprises two anchoring organs 6 or pedicle screws having an elongated rectilinear shape with a longitudinal axis 9. Each pedicle screw 6 has a threaded end portion 10 or foot adapted to be anchored in a vertebra of the spine, and an opposite head 12 longitudinally to this threaded portion 10. The screw 6 has a free end 11 longitudinally opposite the head

12.

The system comprises an anchoring connection element 14 constituted here by an elongated, generally rectilinear stem with a circular section.

Each screw head 12 has, not shown, two legs extending in front of each other, defining a cavity between them. Head 12 comprises a radially split ring having a spherical outer face and a cylindrical central bore. The ring is adapted to be threaded onto the shank 14 and to be housed in the cavity of the screw head 12. The screw 6 comprises a locking ring, not shown, that cooperates with the legs by being threaded on them to maintain the separation of the legs when their separation occurs caused by the tightening action of an internal locking nut threaded on the head of the screw. screw and resting on the spherical split ring threaded on the stem 14. After locking, the screw head is locked by the combined action of the internal nut and locking ring. Before locking, each pedicle screw 6 is free to move with respect to stem 14, in particular in sliding along the stem and in rotation around the annulus, performing a ball and socket joint. In particular, the screw 6 is free to move with respect to the stem 14 in rotation around a first perpendicular axis 18

ES 2 201 340 T3 to the longitudinal axis 9 of the screw 6 and perpendicular to the longitudinal direction of the stem 14. Thus, the system can have a non-locked configuration in which the anchoring members 6 are movable with respect to the stem 14, and a interlocked configuration in which the anchoring members are rigidly fixed to the stem. The non-locked configuration allows the position of the anchoring members to be chosen as a function of the desired position for the associated vertebrae, and the locked configuration allows the vertebrae to be rigidly immobilized in this position in view of osteosynthesis. Pedicle screws 6 and stem 14 are generally known, for example from the cited document FR-2 659 546, and will not be described in more detail here.

The tooling comprises two arms 8 intended to be associated with the respective screws and each having a general elongated rectilinear axis shape

9. Each arm 8 comprises a tube of generally cylindrical shape, in particular having a cylindrical external face. The arm has a lower axial arm 20 and an upper axial end 22. The lower axial end 20 has internally two concentric bores of axis 9 in view of the fixing of the lower axial end 20 of the arm 8 by fitting onto the associated screw head 12 . The arm 8 is thus adapted to be fixed to the head of the screw 12 extending in extension of the screw. The upper axial end 22 of the arm 8 then extends at a distance d2 from the free end 11 of the screw 6, greater than twice the distance d1 that separates the lower axial end 20 from the free end 11 of the screw.

The lower axial end 20 has two recesses 24 extending in the wall of the tube and diametrically opposite to either side of the axis 9. These recesses are adapted to receive the rod 14 when the arm 8 is mounted on the screw 6. Each recess 24 has a width substantially greater than the diameter of the stem 14 so that, when the stem 14 is housed in the recesses, the arm 8 is movable in rotation about the axis 9 with respect to the screw 6 in a reduced amplitude, for example 10 ° to each side of an average relative position, and therefore 20 ° in total. Each upper axial end 20 has a central opening that allows the passage of a tool in the arm 8 to actuate the locking nut of the pedicle screw 6 on the stem 14, such as the one mentioned when the arm 8 is in position on the head. screw 12.

One of the arms 8, located on the right in Figure 1 and represented in Figures 3 to 7, supports, near its upper axial end 22, a flange 26 traversed by a shaft 28 of axis 30, movable in rotation with respect to the flange around axis 30 and movable in translation with respect to the flange along axis 30. This axis will be called "second axis". The second axis 30 is perpendicular to the longitudinal axis 9 and to the longitudinal direction of the stem 14. The second axis 30 is parallel to the first axis 18. The system comprises two racks 32 each having a series of teeth 34. These racks are rectilinear, parallel to each other and coplanar. The teeth 34 of the two racks 32 have matching identical profiles. The two zippers are fixed with respect to each other, the zippers being defined on two mutually parallel branches of a bar folded in a "U" shape. The base 35 of the "U" extends at a first end of the racks, and a second end of the racks is rigidly fixed to the shaft 28. The racks 32 and the shaft 28 constitute a connecting element of the arm 31 of the system.

This connecting element is movable in rotation with respect to one of the arms 8 around the second axis 30, and permanently fixed to this arm. In the following, the tube that supports the zippers will be called "rack tube".

As Figures 7 and 8 show, the flange 26, the shaft 28 and the racks 32 are configured such that the shaft 28 is movable in translation along the second axis 30 with respect to the arm 8 that supports it. The amplitude of this translation is, for example, 10 mm. Figure 7 shows an extreme position in translation of the shaft, one of the racks resting against the arm 8. Figure 8 shows a middle position, the racks 32 being equidistant from the arm 8.

The other arm 8, located on the left in Figure 1 and represented in Figures 8 and 9, supports a rod 36 fixed thereto in the vicinity of its upper axial end 22. The rod extends in a direction parallel to the first axis 18. The rod 36 has a tooth-shaped profile over its entire length, the rectilinear head of the tooth being oriented in the opposite direction to the associated pedicle screw 6. This profile is adapted to cooperate by engagement with the teeth 34 of the racks 32 to mesh with the arm connecting element 31. The tube that supports the rod will be called "return tube". Precisely, the rod 36 has two zones 41 that extend on either side of the associated arm 8 and intended to engage with the two respective racks 32. Each zone 41 of the rod has a width 1 greater than the width of the associated rack 32 in order to remain engaged with the rack regardless of the position of the rack in translation along the second axis 30. There are two positions in which the arm connecting element 31 extends in a direction substantially perpendicular to the longitudinal axis 9 of the rack tube.

In one of these positions, the teeth 34 are oriented in the direction of the associated pedicle screw 6 and can therefore engage with the rod 36 of the return tube.

The teeth 34 of the racks have an asymmetric right triangle profile that allows the rod 36 to move along the racks 32 in a first direction when the rod is in engagement with the racks, and preventing its displacement in a second direction. opposite to the first sense. Thus, the arm connecting element 31 makes it possible to define an end of mutual separation between the two upper axial ends 22 of the arms 8. In the example, when the rod is in engagement with the racks, the profile of the teeth allows the mutual approach of the upper axial ends 22 of the arms and prevents their mutual distance, and this in any position of the rod on the racks . The arm connecting element 31 therefore defines here a maximum of mutual separation.

The rack tube comprises a spring 40 constituted by a flat, elongated, generally rectilinear sheet, extending parallel to the longitudinal axis 9, having a fixed lower axial end 42

ES 2 201 340 T3 in a middle portion of the cylindrical external face of the arm 8, and an upper axial end 44 supported against the shaft 28 and arranged between the shaft 28 and the arm. The shaft 28 has two planes 46, 48 which extend substantially perpendicular to one another and parallel to the second axis 30. The rest of the face of the shaft 28 is cylindrical. Plane 46 is arranged so as to make surface-to-surface contact with spring 40 when racks 32 extend perpendicular to supporting arm 8 in view of engaging rod 36. Spring 40 and plane 46 constitute means of return of the arm connecting element 31 towards a position of engagement of the racks with the rod. Likewise, the second plane 48 is arranged so that the arm connecting element 31 is attracted towards a rest position in which it extends substantially parallel to the longitudinal axis 9 resting against the cylindrical face of the arm 8, this rest position being separated from the aforementioned docking position by an angle of approximately 270 °.

The tooling further comprises a hand tool such as a distraction forceps 48 having two drive ends 50 adapted to be simultaneously engaged against the lower axial end 20 of the arms 8 in order to separate them from each other.

The rod 36 and the flange 26 are arranged so that when the two arms 8 are joined by the arm connecting element 31, the rod and the flange extend from a rear side of each arm, opposite the other arm. Each arm 8 has a flat outer face 50 that extends from a middle region of the arm to the upper axial end 22. This face 50 is inclined with respect to the longitudinal axis 9 so that the upper axial end portion 22 of the arm has a width that tapers towards this end 22. These flat faces 50 are arranged so that they extend opposite each other. another when the two arms are joined by the arm connecting element 31. The flat faces 50 are respectively opposite the flange 26 and the rod 36 with respect to the longitudinal axis 9.

The arm connecting element 31 and the two arms 8 constitute a positioning tool for the osteosynthesis system.

The set is used as follows. Each pedicle screw 6 is fixed to vertebrae of the spine, or parts of vertebra. The rings and stem 14 are placed in position, the assembly being in an unlocked configuration. Each arm is mounted

8, namely the rack tube and the return tube, on the associated screw 6. By means of the clamp 48, the lower axial ends 20 of the arms 8 are separated from one another, so that a distraction movement of the vertebrae associated with the anchoring members 2, 4 is carried out. The stem 14 then serves as guide for the relative displacement of the anchoring members. Then, while keeping the lower axial ends 20 in this position, the arm connecting element 31 is passed from the rest position against the arm 8 to the position of engagement with the rod 36.

The two upper axial ends 22 are then mutually approximated to each other as allowed by the racks 32 coupled with the rod 36, to regulate and choose the maximum spacing between the upper axial ends of the arms. In the course of this approach, the relative angular orientation of the longitudinal axes 9 of the anchoring members varies. Thus, an angular correction movement of the position of the vertebrae is carried out.

When the desired spacing between the upper axial ends 22 has been reached, these ends 22 are loosened. The zippers 32 then prevent any mutual movement of the ends 22 in this position (unless the zippers are disengaged from the rod). It is then possible, if necessary, to modify the mutual spacing between the lower axial ends 20 again, for example by means of the clamp 48, to effect a new distraction and angular correction movement and thus still specify the relative position of the vertebrae. In the course of this movement, the upper axial ends 22 retain the same mutual separation thanks to the self-staticity of the connection between the racks 32 and the rod 36. There is only one rotation of the rack tube with respect to the arm connection element 31 about the second associated axis 30, as well as one rotation of the return tube with respect to the arm connection element 31 about the second associated axis 30 defined by the head of the tooth of the rod 36 engaged with the racks 32. This second axis 30 of the return tube is parallel to the second axis 30 of the rack tube. It is then possible, if necessary, to move the axial upper ends 22 of the arms 8 again relatively, either by bringing them closer to each other with the rod 36 always engaged with the racks 32, or by moving them away from each other, temporarily interrupting the coupling. between the rod and the zippers.

When the racks 32 are in engagement with the rod 36, they extend to either side of the arm 8. Thus, when the rod 36 moves along the racks to bring the ends 22 closer together, the racks they constitute a guide for the movement of the arm 8 that supports the rod. The two inclined faces 50 allow the two upper axial ends 22 to be brought very close to each other, for example by bringing them into contact with each other.

Once the desired position for the vertebrae has been reached, the pedicle screws 6 are rigidly locked in position on the stem 14 thanks to the aforementioned opening made in the arms for this purpose. The arms 8 are then extracted by separating them from the respective pedicle screws 6.

The freedom of rotation of each arm 8 with respect to the associated screw 6, and the freedom of translation of the shaft 28 with respect to the flange 26 allows the system to adapt to the desired positions for the vertebrae.

The equipment may comprise several pairs of anchoring members 6 and arms 8. It may comprise one or more rods 14 to connect these members to each other.

The teeth 34 of each rack could be oriented in the opposite direction in order to define a minimum gap between the upper axial ends 22 of the arms.

The length of the arm 8 is here approximately twice the length of each pedicle screw 6.

The length of the arm will advantageously be greater than the length of the associated screw 6.

The tooling according to the invention can be used with a different osteosynthesis device from that mentioned in patent document FR-2 659 546.

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On the other hand, a positioning tool for an osteosynthesis system for the spinal column can be provided more generally, comprising two anchoring members each adapted to be anchored in a vertebra of the spine, and an anchoring connecting element adapted to join the anchoring members with respect to each other, the system being adapted to obtain a non-locked configuration in which each anchoring member is movable with respect to the anchoring connecting member, and an interlocked configuration in which each anchoring member is rigidly fixed to the anchor connection element, the tooling comprising two arms adapted to be removably fixed to the two respective anchoring members 6 and an adapted arm connection element 31 to join together a part of each arm, in which each arm has an opening for the actuation of locking means in position provided in each anchoring member while the arm is fixed to the anchoring member.

Preferably, this opening will extend along the axis of the arm, in which it will then be hollow, so that the locking means located near the base of the arm will be actuated by introducing a tool into the arm from the upper part of the arm.

On the other hand, it is also possible to provide more generally a positioning tool for a spinal osteosynthesis system comprising two anchoring members each adapted to be anchored in a vertebra of the spine, and an anchoring connection element adapted to join the anchoring members together, the system being adapted to have a non-locked configuration in which each anchor member is movable in sliding along the anchor connection element, and a locked configuration in which each anchor member is rigidly fixed to the anchor connection element. anchorage, the tooling comprising two arms adapted to be removably fixed to the two respective anchoring members and an arm connecting element adapted to join together a part of each arm. The tooling will then advantageously further comprise a hand tool such as tool 48.