Device for fixing a bony structure to a support member

A device for fixing a bony structure to a support member. The device includes a main body with first and second members, the second member being movable in rotation with respect to the first member, around a first axis. A flexible member passes between the members and forms a loop around a bony structure. A clamping mechanism moves the first and second members into a clamping position. A support member and the flexible member are secured between the members in the clamping position. The first axis is movable in translation along a first direction and the second member is movable in translation along the first direction. The clamping mechanism cooperates with the first and second members to move the second member in translation in the first direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to EP12305614.5, filed on Jun. 1, 2012, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure generally relates to a device for fixing a bony structure to a support member, to a system comprising such a device and to a method using it. Such a device may be helpful for holding a bone (e.g. a vertebra) and a support member (e.g. a rod) in a desired configuration. In particular, the present disclosure relates to a system and method for stabilizing at least two vertebrae.

BACKGROUND OF THE INVENTION

One field of application for the invention is holding together a bone and a support member in a desired relative position, while allowing in some cases a limited amount of relative movement, for example to aid in healing of breaks or to correct bony structure deficiencies and abnormalities. In particular, sufferers of abnormal spine curvature or other spine deficiencies may benefit from the invention.

The spine is formed of superposed vertebrae, normally aligned along a vertebral axis, from the lumbar vertebrae to the cervical vertebrae, each having an anterior part: the vertebral body, and a posterior part: the vertebral arch (or neural arch), the anterior and posterior part enclosing the vertebral foramen. Each vertebral arch is formed by a pair of pedicles and a pair of laminae, with transverse processes and/or a spinous process (or neural spine) projecting therefrom. The transverse processes and the spinous process project opposite to the vertebral foramen.

When the vertebrae are articulated with each other, the vertebral bodies form a strong pillar for the support of the head and trunk. In between every pair of vertebral bodies, there is an intervertebral disc.

When the spine of a person has abnormal curvature (e.g. scoliosis) or other deficiencies (e.g. a damaged intervertebral disc), the vertebrae are typically too close together, too far apart or otherwise misaligned, and there is a need to stabilize the vertebrae in a correct position relative to one another. Mainly, there is either a need to compress the vertebrae (i.e. to bring and hold them closer together) or a need to distract the vertebrae (i.e. to move and keep them away from each other).

Devices known in the art for holding vertebrae relative to one another typically include one or more rods that are held by devices attached to the vertebrae by means of screws, hooks, or flexible ligatures. One such device is described in patent document EP2052689A1. This known device comprises a holding body having a receiving portion for receiving the rod and an engagement portion, a closure member for engagement with the engagement portion of the holding body to secure the rod within said receiving portion, and an anchor member for anchoring the holding body to the bony structure of a vertebra.

In the device of EP2052689A1, to create a connection, the receiving portion of the holding body has to be sized to the gauge of the rod used. Since, depending on the specific intervention and patient, a variety of different rod gauges may be required, different holding bodies adapted to accommodate each specific rod gauge need to be provided.

While known devices have proven effective, further improvements would be beneficial.

SUMMARY OF THE INVENTION

Described is a fixing device for fixing a bony structure to a support member. This fixing device comprises:a main body comprising first and second members defining between them a first passage configured for receiving the support member, the second member being pivotable with respect to the first member, around a first axis, anda clamping mechanism engaging the main body and being configured to move the first and second members towards each other for clamping the support member therebetween.

In an exemplary fixing device, the first axis is movable in translation along a first direction so that the second member is movable in translation along the first direction, with respect to the first member. Such freedom of movement in translation allows the size of the first passage to be adjusted to the gauge of the support member to be used. Proper clamping of a variety of support members having different gauges can thus be obtained.

In certain embodiments, the clamping mechanism engages with the first and second members and is configured to move the second member in translation along the first direction, so as to narrow the first passage. Accordingly, the size of the first passage can be narrowed to the gauge of the support member to be used, by means of the clamping mechanism.

Configurations of the device that allow for the intraoperative adjustment of the first passage of the device that receives the support member can have the advantage of being adjustable to a variety of support members having different gauges, while being made of a limited number of parts, which makes the device simpler to produce and easier to handle.

In certain embodiments, the fixing device is adapted to receive a flexible member within the first passage, in a direction transverse to a longitudinal axis of the first passage.

The fixing device may be adapted to clamp the flexible member between at least one of the first and second members and the support member, when a support member is disposed within the first passage. In this case, the flexible member and the support member can be simultaneously clamped, i.e. the flexible member and the support member can be simultaneously held in position with respect to the fixing device.

At least one of the first and second members may be provided with at least one through opening, said through opening being in communication with the first passage and being configured to guide the flexible member therethrough.

In certain embodiments, the clamping mechanism comprises a clamping member which is configured to cooperate with the first and second members so as to exert a force on the second member, the force having a component along the first direction.

In certain embodiments, the resultant force exerted by the clamping member on the second member is oriented substantially along the first direction, which improves the clamping efficiency.

A variety of clamping mechanisms that cause the flexible member and support member to remain in a fixed position can be utilized. For example, a single clamping mechanism can be used to hold the flexible member and support member in a fixed position, or two or more separate clamping mechanisms can be used to hold the flexible member and support member in a fixed position individually.

In certain embodiments, the clamping member is a screw with a screw head and a shank, the shank being threadably engaged with the first member and the screw head being configured to exert said force on the second member when the screw is tightened (e.g. when it is screwed into the first member). Using a screw as the clamping member is one embodiment which allows the physician to (finely) adjust the clamping force to the needs. In particular, the physician (or other operative) may lock, unlock, move and/or remove the fixing device, merely by screwing or unscrewing the screw.

The fixing device can be preloaded onto a support member with the clamping mechanism partially tightened with final tightening occurring after the physician has the flexible member and support member in its desired position.

In certain embodiments, the screw head defines a first sloped or curved surface and the second member defines, on its outside face, a second sloped or curved surface. The force exerted by the screw onto the second member is exerted through those first and second surfaces when the screw head is tightened. The first sloped or curved surface may be symmetrical around the rotational axis of the screw. It may be, for instance, a circular part of a spherical (or substantially spherical), convex or conical surface of the screw head.

In certain embodiments, the second member is provided with an oblong opening through which the screw shank passes. The longitudinal direction of that oblong opening may be substantially perpendicular to the screw axis and/or to the first axis A.

In certain embodiments, the second member has an inside face defining an abutment for engagement against the support member. This abutment pushes the support member towards the first member when the second member is moved in translation in the first direction. The shape of the abutment is configured to transmit force to support members of different gauges in the best possible way. For example, the outline of the abutment, in a section plane perpendicular to the first axis, may be concave towards the support member. For instance, the abutment may be a groove, the support member being engaged in that groove.

In certain embodiments, a pivoting mechanism is provided between the first and second members, the pivoting mechanism comprising a pivot shaft being received in an oblong opening provided in at least one of the first and second members.

In certain embodiments, one of the first and second members is provided with a pivot shaft extending along the first axis, and the other one of the first and second members is provided with at least one oblong opening (i.e. an opening having an oblong cross-section) through which the pivot shaft passes, the oblong opening having a longitudinal direction substantially parallel to the first direction. The cooperation between the pivot shaft and the oblong opening is a simple and safe solution for the first and second members to move both in translation and rotation with respect to each other. In cross-section, the oblong opening may have an open outline, i.e. an outline with a gap, or a close outline. When the oblong opening has an open outline, the pivot shaft may be inserted into or taken out of the oblong opening sideways, through the gap of the open outline of the opening. The oblong opening may be open in its longitudinal direction, i.e. the gap of the open outline of the opening may be provided along the longitudinal direction of the groove.

In certain embodiments, the pivot shaft is a one-piece shaft extending through the first and second members. This one-piece shaft may be fixedly linked to the first or second member by friction, welding, swaging, crimping, pressing, clamping or any other appropriate solution.

The pivot shaft may also be defined by two pins protruding from one member, on opposite sides thereof, and extending through the oblong openings of the other member.

Also described is a system comprising at least one support member and at least one fixing device, as described above, for fixing a bony structure to the support member.

The support member may be rigid or not. Typically, the support member is a rod or equivalent. The cross-section of the support member may have different shapes. For instance, it may be round, flat or polygonal. The support member may be provided in a variety of gauges (e.g. different widths or diameters) that can be available to a physician for surgery, thus providing the physician with the ability to select an appropriate support member for the patient from a set of available sizes. In particular, the system may comprise a set of support members of different sizes and at least one fixing device.

The system may further comprise a flexible member passing through the first passage, between the support member and said first and/or second member, the flexible member extending outside or beyond the main body for attachment to the bony structure. In particular, the flexible member may form a loop around the bony structure.

The flexible member may be made of any suitable material that is flexible such as a band, wire, ligament, or cord. For instance, the flexible member may be made of a metal, a polymeric material or a combination thereof.

such a system may be a system for stabilizing at least two vertebrae, which comprises: a first fixing device configured to be fastened to a first vertebra, a second fixing device configured to be fastened to a second vertebra, and a support member for connecting the first and second devices together, thereby providing stabilization between the first and second vertebrae; and wherein at least the first fixing device is a device as described above.

The second fixing device may be similar to or different from the first fixing device.

The stabilization system described herein may be used for providing “static stabilization” or “dynamic stabilization” between the vertebrae. Static stabilization typically refers to holding together the vertebrae in a particular relative position, while minimizing movement between the vertebrae, whereas dynamic stabilization typically refers to holding together the vertebrae in a particular relative position, while allowing a limited amount of relative movement between the vertebrae. For dynamic stabilization, the support member and/or the flexible member may have elastic properties.

As explained above, a variety of support members with different gauges (e.g., with different diameters in case of round section rods) may be used with the same fixing device. Different gauges may be needed to treat different pathologies or portions of the bony structure of the spine (e.g., cervical, thoracic, lumbar, sacral regions). Accordingly, the system may include several support members, of different gauges (or different shapes), and at least one fixing device. The gauge of the support member to be used is then chosen by the physician (or other operative), depending on the specific intervention and patient.

Also described is a method for connecting a bony structure to a support member, comprising the steps of: providing a support member and a fixing device as defined above; passing said loop around the bony structure and applying a force to (e.g., tensioning) said loop to change the position of the bony structure, and impeding movement of the bony structure relative to the support member by fixing the position of the flexible member and support member relative to the fixing device, e.g. by clamping the flexible member and the support member between the first and second members.

Such a method may be used for stabilizing at least two vertebrae. In this case, it comprises the steps of: providing a system as described above; fixing the first fixing device to a first vertebra, by passing said loop around a bony part of the vertebra and tensioning said loop; fixing the second fixing device to a second vertebra; and impeding relative movement between the first and second fixing devices by connecting each of them to the support member, relative movement between the first vertebra and the support member being impeded by fixing the position of the flexible member and support member relative to the first fixing device.

These methods have the advantages derived from using a fixing device or a stabilization system according to the present disclosure.

In particular, the physician (or other operative) may be provided with a system comprising one or several fixing devices as described above, and several support members (e.g., several rods) of different gauges. Since the physician is able to accommodate any of the different support members from the set in the fixing device(s), the physician can freely select one appropriate support member (with a particular gauge) without worrying about the compatibility between the selected support member and the fixing device(s). In other terms, regardless of the support member being selected, the physician can use the same type of fixing device. Accordingly, the physician does not waste time in choosing the fixing device. In addition, the physician needs to acquaint himself with the handling and use of one type of fixing device only.

Selection of the appropriate support member may be done depending, e.g., on the pathology or the type of bony structure to be treated.

Such methods may be used for correcting abnormal spine curvature (e.g., scoliosis) or other spine deficiencies (e.g., a damaged intervertebral disc) by compressing or distracting vertebrae.

Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, some principles of the invention.

DETAILED DESCRIPTION

In the following detailed description, it is referred to the accompanying drawings showing examples of fixing devices and stabilization systems. It is intended that these examples be considered as illustrative only, the scope of the invention not being limited to these examples.

A first example of fixing device1is shown inFIGS. 1 to 4. This device1is for fixing a support member, such as a rod4(seeFIGS. 2-4), to a bony structure. The bony structure may be, for instance, a vertebra V1or V2, as shown inFIG. 7.

The rod4is an example of support member according to the present disclosure. Here, the rod4is rigid and has a circular cross-section. It may be made of biocompatible metallic material.

The fixing device1may be made of biocompatible metallic material. It comprises a main body2forming a clamp. The main body2comprises a first member13and a second member23linked to the first member13over a hinge of axis A. In the figures, the first and second members13,23are, respectively, the lower and upper portions of the main body2. The rod4extends substantially parallel to axis A.

The hinge comprises a pin or shaft10passing thought the first and second members13,23. When the first and second members are assembled, the shaft10extends along axis A and goes successively through an opening13A provided in a first lateral leg13of the second member23, through an opening14A provided in a central part14of the first member13, and through an opening15A provided in a second lateral leg15of the second member23. The lateral legs13,15of the second member23are located on each side of the central part14of the first member13. All openings13A,14A,15A are through holes. However, in other embodiments one or more of the openings13A,14A,15A may be blind holes. Openings13A and15A have a circular cross-section of substantially the same size (i.e. substantially the same diameter) as that of the shaft10. When the fixing device1is assembled, the shaft10is held by friction, welding, swaging, crimping, pressing, clamping or any other appropriate fixing solution inside the openings13A,15A, or otherwise attached to the legs13,15of the second member23. Opening14A has an oblong cross-section with a close outline. The longitudinal direction LD of oblong opening14A is perpendicular to axis A. The shaft10can turn inside the opening14A and can move along the longitudinal direction LD of the opening14A (seeFIGS. 3-4: the position of the shaft10inside the opening14A is different). Accordingly, with respect to the first member13, the second member23is movable in rotation around the first axis A, while being movable in translation in a first direction D parallel to the longitudinal direction LD. In other embodiments, the oblong opening14A may be curved or arcuate, thus allowing the shaft10to move in the oblong opening14A in an arcuate path generally perpendicular to the axis A.

The fixing device1further comprises a flexible member20(shown inFIGS. 3-4, not depicted inFIGS. 1-2) passing through the main body2—e.g. through the first member1, through the passage5between the members13,23, and through the second member23—and extending from the main body2to form a loop20P around a bony structure (not shown inFIGS. 1-4). Here, the flexible member20has two end portions20E and an intermediate portion forming said loop20P. The loop20P extends outside the main body2from a passage21provided in the first member13, and the end portions20E extend from the main body2from a passage22provided in the second member23. The loop20P is tightened or tensioned around a bony structure by pulling on the end portions20E, and the flexible member20is locked in position by clamping the portions13,23and thus pressing the flexible member20between the rod4and a surface of the first member13.

In this example, there is only one exit passage22for the end portions20E and one loop passage21for the loop20P. However, in other examples, not shown, the main body2is provided with two exit passages, i.e. one for each end20E of the flexible member20. Similarly, the main body2may be provided with two loop passages, i.e. one for each branch of the loop20P.

The main body2is further provided with a first passage5for receiving a portion4A of the rod4. The first passage5is defined by recesses provided in the inside faces of the first and second members13,23.

The exit passage22and the loop passage21both communicate with the first passage5. In the appended figures, the exit passage22is located above the first passage5whereas the loop passage21is located below the first passage5. When the flexible member20is passed through the main body2and the rod portion4A is placed into the main body2, between the members13,23, portions of the flexible member20(located between the end portions20E and the loop20P) are held between the rod portion4A and the internal walls of the members13,23defining the first passage5.

In the example ofFIGS. 1-4, the exit passage22, the first passage5, and the loop passage21are substantially aligned and the flexible member20passes on the same side of the rod4, near the first axis A. In other examples, not shown, the flexible member20passes on each side of the rod4, i.e., one branch of the flexible member20passes on one side of the rod4, while the other branch of the flexible member20passes on the other side of the rod4.

The fixing device1also comprises a clamping mechanism for bringing and maintaining the first and second members13,23in a clamping position in which the rod4and the flexible member20are held tight.

Here, the clamping mechanism comprises a screw6. The screw6has a shank6B going through the first and second members13,23, and a head6A having a profile (being internal or external) that allows the screw6to be driven in rotation. In more detail, the screw shank6B passes through an orifice9provided in an engagement portion123of the second member23, and can be screwed into a threaded hole13formed in an engagement portion113of the first member13. The screw shank6B is provided with an outside thread for engagement with the inside thread of the hole13.

The orifice9is oblong, the longitudinal direction N (seeFIG. 2) of this orifice9being oriented substantially perpendicular to the screw axis S and to the first axis A. Due to this oblong shape, the second member23is movable in translation in the longitudinal direction N with respect to the screw6(when the screw6is screwed into the first member13).

The screw6and the engagement portions113,123of the first and second members13,23are located on the side of the main body2which is opposite to the hinge (i.e., to axis A), with respect to the rod4.

By tightening the screw6, the first and second members13,23are moved toward each other and the rod portion4A is clamped inside the first passage5, between the first and second members13,23, while the flexible member20is simultaneously clamped between the rod portion4A and the members13,23.

The screw head6A has a generally spherical, convex or conical shape and the lower part of the screw head (i.e., the part close to the shank6B) defines a first sloped or curved surface31. When the screw6is tightened, the screw head6A comes into abutment with a second sloped or curved surface32defined on the outside face of the engagement portion123, around the orifice9, and the screw head6A pushes on the engagement portion123. Thus, a force F (seeFIG. 4) is exerted by the screw head6A on the second member23, through the first and second surfaces31,32. This force F has a component along the first direction D and, advantageously, the force F is aligned with the first direction D.

The tightening of the screw6makes the pivot shaft10move through the oblong opening14A in the first direction D, as illustrated inFIGS. 3-4(the device being shown in a non-clamping position inFIG. 3, and in a clamping position inFIG. 4). So, when the screw6is tightened, the second member23is moved in translation along the first direction D, with respect to the first member13. The second member23has an internal face with an abutment face33for the rod4, the abutment face33pushing the rod4towards the first member13when the second member23is moved relative to the first member13. In turn, the rod4presses the portions of the flexible member20against the face34of the first member13, thereby locking the flexible member20in position.

Another example of fixing device101is shown inFIGS. 5-6. This device differs from the one ofFIGS. 1-3by the hinge linking the first member1013with the second member1023. The other parts are substantially the same and will not be described again, for the sake of conciseness.

In the example ofFIGS. 5-6, the hinge between the first and second members1013,1023comprises two pins110aligned with each other and both extending along axis A in opposite directions from the first member1013. Those pins110extend from the lateral sides of the central part114of the first member1013and are respectively engaged through openings113A,115A respectively provided in first and second lateral legs113,115of the second member1023. The lateral legs113,115of the second member1023are located on each side of the central part114of the first member1013.

Openings113A,115A are oblong holes having a width corresponding substantially to the diameter of the pins110. The longitudinal direction LD of each opening (seeFIGS. 3-4) is parallel to the first direction D and is substantially perpendicular to the first axis A. Accordingly, the pins110are movable within the openings113A,115A both in rotation around their axis A and in translation in direction D. As a consequence, with respect to the first member1013, the second member1023is movable in rotation around the first axis A, while being movable in translation in direction D, generally perpendicular to the axis A. In other embodiments, the oblong openings113A,115A may be curved or arcuate, thus allowing the pins110to move in the oblong openings113A,115A in an arcuate path generally perpendicular to the axis A.

In cross-section, the outline of each opening113A,115A is open, meaning that this outline has a gap140and that each opening113A,115A opens out at the gap140. The gap140is provided at a longitudinal end of the oblong opening113A,115A. Thus, when assembling the first and second members1013,1023, the pins110are inserted into the openings113A,115A, through the gaps140. Then, the screw106is mounted on the members1013,1023. When the screw106is in position but not tightened, the translational movement of the second member1023with respect to the first member1013is possible while being limited, and the pins110cannot exit the openings113A,115A, through the gap140, because the length of the oblong openings113A,115A (i.e. their length along the longitudinal direction LD) is greater than the maximum length of possible translation of the second member1023along direction D.

When the screw106is not yet mounted on the members1013,1023, in order to impede the pins110from being removed from the openings113A,115A, small stops142protruding inside the opening113A,115A may be provided near the gap140. To assemble the members1013,1023together, the pins110are inserted in force into the openings113A,115A, past the stops142. The pins110cannot go backward, past the stops142, unless a sufficient force exceeding a threshold amount of force is exerted thereon.

Pins110may be made in one piece with the central part114of the first member1013or, alternatively, in separate pieces. In particular, pins110may be formed by the end portions of a shaft passing through the central part114and being fixedly linked thereto or by end portions of shafts extending from the part114in opposite directions.

FIG. 7shows an example of a stabilization system for stabilizing at least two vertebrae V1, V2, the system comprising: a first fixing device configured to be fastened to a first vertebra V1, a second fixing device configured to be fastened to a second vertebra V2, and a support member—e.g. a rod4—for connecting the first and second anchors together, thereby providing stabilization between the first and second vertebrae. The first and second fixing devices may be the same or different and may be devices1,101such as those ofFIGS. 1-6. In this example, the first and second fixing devices1,101are respectively fastened to the laminae of the vertebrae V1, V2.FIG. 7is diagrammatic and, in particular, the flexible members of the fixing devices1,101are not shown.