WO2012127267A1

WO2012127267A1 - A pedicular anchoring system

Info

Publication number: WO2012127267A1
Application number: PCT/IB2011/001124
Authority: WO
Inventors: Emmanuel Zylber; Rodolphe Lourdel; Pierre Capron; Jérôme DEFRANCE
Original assignee: Scient'x; Surgiview
Priority date: 2011-03-18
Filing date: 2011-03-18
Publication date: 2012-09-27

Abstract

The present invention relates to an anchoring system comprising: - a vertebral anchoring device for fixation on at least one vertebra, and - a socket (4) for receiving and fastening a corrective device (7), said socket (4) comprising a longitudinal bore extending about a longitudinal axis and a receiving channel (44) for a said corrective device, and - a screwable stopper (5) to be screwed in the longitudinal bore of the socket (4) by means of a fitting tool (6) to bias said corrective device (7) into said receiving channel (44) of the socket and lock said corrective device in position within the receiving channel. According to the invention, the screwable stopper (5) comprises at least one resilient member (56) preventing disassembling of said stopper (5) from the longitudinal bore of the socket (4) once the stopper has been inserted therein.

Description

A PEDICULAR ANCHORING SYSTEM

Technical Domain

The present invention relates to the field of medical devices and more particularly to a vertebral anchoring system for the surgical treatment of spinal pathologies.

Description of the prior art

In the field of spine defaults correction vertebral anchorage devices like pedicular bone screws or hooks are often used to fixedly secure correction devices such as distraction rods into vertebrae along the spinal column.

Pedicular screws typically have a threaded shank configured for implantation into a pedicle or vertebral body of a vertebra. They further comprise a socket designed to extend beyond the vertebra, said socket generally defining a channel or a U-shaped recess in the head's body to receive a rod or other implant. The socket may further be open or closed at its top depending on the design chosen for accommodating a rod or other implant. If the socket is open, a closure member such as a locking screw must be used to close between opposite sides of the socket once a rod or other implant is placed therein. If the socket is closed, a rod or the like implant is threaded or embushed through the socket of the bone screw.

It is consequently difficult, where possible, to proceed to adjustment of the rod or implant in the body, notably when it is necessary to bend the rod and fix it by a second vertebral anchoring device to another vertebra of the spine with the aim of correcting a bending of the spine for example.

Hopefully, the bone screws with an open socket allow pre-locking of rods by use of the locking screws, which can be tightened onto a rod positioned in the U- shaped recesses of the socket to prevent it from slipping out of the recesses while the surgeon is bending it.

However, the surgeon sometimes needs to adjust the position of the rod relative to the pedicular bone screw by sliding it into the socket of the bone screw while maintaining or adjusting the bending of the rod. Such adjustments becomes extremely difficult when the locking screw of the socket of the bone screw has been tightened too much, which is often the case to prevent the locking screw from loosening and disassemble from the socket of the bone screw to fall into the patient's body. Description of the invention

The present invention aims at providing a reliable solution for pre-locking locking screws in the socket of vertebral anchoring devices such as pedicular bone screws or pedicular hooks for example.

The present invention further aims at allowing automatic setting of a locking screw in the socket of a pedicular bone screw to secure the socket onto a rod and preventing the locking screw from disassembling from the bone screw head.

The solution provided by the invention consists in an anchoring system comprising:

- a vertebral anchoring device for fixation on a vertebra, and

- a socket for receiving and fastening a corrective device, said socket comprising a longitudinal bore extending about a longitudinal axis and a receiving channel for a said corrective device, and

- a screwable stopper to be screwed in the longitudinal bore of the socket by means of a fitting tool to bias said corrective device into said receiving channel of the socket and lock said corrective device in position within the receiving channel.

According to the invention, the screwable stopper advantageously comprises at least one resilient member preventing disassembling of said stopper from the longitudinal bore of the socket once the stopper has been inserted therein.

It should be noted that the corrective device used in connection with the anchoring system of the invention can be a distraction rod or a corrective implant or another surgical device that needs to be secured to the spine for treatment or corrective purpose. The vertebral anchoring device can also be any kind of pedicular anchorage, a vertebral screw or a hook for instance.

According to a preferable embodiment of the invention, the screwable stopper comprises advantageously a cylindrical body comprising a buttress external thread being complementary with a corresponding buttress internal thread on the internal surface of a wall of the socket.

Preferably, the screwable stopper comprises an annular collar accommodating said resilient member.

Still preferably, said collar extends beyond said external thread at a bottom of the bodv of the screwable stopper.

In an illustrated embodiment of the apparatus of the invention said collar comprises a lip forming a shoulder extending radially to its annular surface and about which said resilient member is clipped.

In a preferred embodiment of the invention, the diameter of said collar is lower than the diameter of external thread of said screwable stopper.

As n advantage, said resilient member can be chosen as a bushing ring. It is also preferable that the resilient member is made of polymer.

In the illustrated embodiments, the apparatus of the present invention further comprises a fitting tool to fit the screwable stopper into said socket by means of screwing wherein said fitting tool comprises an engaging part configured to engage said screwable stopper such that the fitting tool is automatically released from the screwable stopper once it has been screwed in a said socket for a determined lengthin a pre-locking position.

According to another characteristic of the invention, the screwable stopper comprises a longitudinal through hole having an internal shape adapted to mate the shape of the engaging part of a fitting tool.

Advantageously, the engaging part of the fitting tool comprises a tapered coupling section and a cylindrical tip protruding from the through hole of the screwable stopper to abut against a corrective device lodged into the receiving channel of the socket before the screwable stopper when said stopper is screwed with the fitting tool in the socket and manage a clearance between said stopper and said corrective device and forcing disengagement of the fitting tool from the screwable stopper. Preferably, the tapered shape of the engaging part of the fitting tool is such that the contact between said engaging part and said through hole of the screwable stopper is linear. Description of drawings

The anchoring system of the present invention will be presented hereinafter in the detailed description, with references to the enclosed drawings into which:

- Figure 1 is a front view of the an anchoring system according to the invention comprising a pedicular screw, a screwable stopper fitted in a socket of said screw and a fitting tool for adjusting and screwing the stopper inside said socket;

- Figures 2A and 2B are perspective views of the pedicular screw of the anchoring system shown in fig.l except for the fitting tool that has been removed;

- Figure 3 is a perspective view of a fitting tool for pre-locking the screwable stopper of the anchoring system of the invention;

- Figure 4 is an exploded perspective view of a screwable stopper for the anchoring system of the invention;

- Figures 5 and 6 are front section views of the socket of the pedicular screw of the anchoring system of the invention showing the adjustment process of the screwable stopper with the fitting tool in the socket where a distraction rod has been inserted;

- Figures 7 and 8 represent section views of the anchoring system of the invention showing respectively the linear contact between the fitting tool and the screwable stopper during screwing of said stopper and disengagement of said linear contact when the screwable stopper has been set in a pre-locking position

- Figures 9 and 10 represent variant embodiments of the anchoring device of the invention in the form of a vertebral hook and a fixed pedicular screw respectively.

Best mode for carrying out the invention

As it is commonly known in the field of spine surgery and represented one of the main problems encountered by the surgeons when implanting patients with rods or the like for corrective purpose of spine pathologies is that classical pedicular bone screws with screwable stoppers are incompatible with in-situ rod bending technique for example because it is necessary to lock the rods in translation into the socket of pedicular bone screws by tightening the screwable stoppers against the rods to prevent said stoppers from disassembling from the socket of the pedicular screws and falling into the patient's body.

To get rid of this incompatibility the present invention proposes an anchoring system 1 illustrated in Figs.l to 10, which cancels the need of effective locking of the stopper to proceed to in-situ bending of rods once the pedicular bone screws have been implanted into the spine at their required position.

With reference to Figs. 1-8, the reference number 1 generally represents an anchoring system according to the present invention in a preferred embodiment. Figures 9 and 10 represent variant forms of an anchoring device according to the present invention presenting common technical features with the following description.

The anchoring system 1 comprises a vertebral anchoring device in the form of a pedicular bone screw 2, a gripping assembly 3 comprising a socket 4 and a screwable stopper 5 to be fit in the socket 4 for adjusting the pedicular bone screw 2 onto a corrective device or surgical implant such as a distraction rod 7 and a fitting tool 6 adapted for fitting said screwable stopper 5 into said socket 4 of the gripping assembly 3.

The pedicular bone screw 2 comprises a shank 21 integral with an upwardly extending upper end 22 generally having a substantially spherical form.

The shank 21 is elongate about a longitudinal axis X-X', with a helically wound bone engaging thread 23 extending substantially from the upper end 22 to near a lower spike tip 24 and projecting radially outward therefrom. The helically wound thread 23 thereby allow for gripping and advancement of the pedicular bone screw 2 in the bone of a vertebra to allow a surgeon secure an implant or rod 7 to the spine of a patient for correcting a deformation or pathology in the spine such as scoliosis. The gripping assembly 3 extends at the upper end 22 of the shank 21 about said axis X-X'. It comprises a socket 4 and a screwable stopper 5. The gripping assembly 3 is integral with the shank 21 to provide a monoaxial extending device for fixing an implant or rod 6 to correct a default in the spine.

The socket 4 of the gripping assembly 3 has a substantially cylindrical shape with a peripheral cylindrical wall 41 extending about the axis X-X' and delimiting a central longitudinal bore 42 into which said screwable stopper 5 can be accommodated.

The inner surface of the peripheral wall 41 includes a helically wound track or thread 8 extending from the top rim 43 of the longitudinal bore 42 downwardly therefrom.

The track or thread 8 is configured to mate with a corresponding external thread 9 located on the external surface of the screwable stopper 5 when said stopper 5 is introduced and rotated by means of the fitting tool 6 into the longitudinal bore 42 at the top rim 43.

It should be noted that the corresponding shapes of the track or thread 8 in the socket 4 and the external thread 9 of the screwable stopper 5 can be configured with any type of structure conventionally known such as V-shaped thread, a buttress thread, a reverse angle thread or other thread-like or non-thread-like helically wound mating shapes for operably guiding under rotation and advancing the screwable stopper 5 in the socket 4 of the gripping assembly 3 when the stopper 5 is torqued in the longitudinal bore 42 of the socket 4 with the fitting tool 6.

The closure screwable stopper 5 is aimed for biasing a correction member such as a rod 7 for correction of spinal deformities against the bottom of a U-shaped channel 44 defined by two U-shaped recesses 45 casted or machined in opposite symmetrical positions in the wall 41 of the socket 4 of the gripping structure 3.

The two U-shaped recesses 45 extend symmetrically about the longitudinal axis X-X' of the socket and bone screw 2 from the top rim 43 of the socket 4 to beneath the middle of the socket 4, and preferably approximately at a third of the socket's length taken from the top end 22 of the shank 21 of the bone screw 2. The two U-shaped recesses 45 define the U-shaped channel 44 throughout the socket 4, which is designed to receive a correction rod 7 seated at the bottom of the U-shaped recesses 45 so that said rod 7 can only be translated transversely to the axis X-X' of the shank 21 and socket 4 of the bone screw 2 in the channel 44 defined by the recesses 45.

The rod 7 that is utilized with the anchoring system 1 can be any of a variety of implants utilized in reconstructive spinal surgery, but is normally a cylindrical elongate structure having a cylindrical surface of uniform diameter and preferably having a generally smooth surface. The rod 7 is also preferably sized and shaped to snugly seat near or at the bottom of the U-shaped channel 44 of the socket 4.

As illustrated in Figs. 1 and 2, the screwable stopper 5 has a generally cylindrical body 51, with a helically wound external thread 9 configured to mate the internal track or thread 8 on the inner surface the socket's wall 41 for rotating advancement of the stopper 5 into the socket 4 when said stopper 5 is rotated clockwise in the longitudinal bore 42 of the socket 4 from the top rim 43 and, in particular, to cover the top or upwardly open portion of the U-shaped channel 44 to capture the rod 7 within the socket 4 of the pedicular bone screw 2.

The screwable stopper 5 further includes at a base or bottom 52 an annular collar 53 of smaller diameter than the body 51. The annular collar 53 is provided with a lip 54 at its bottom. The lip 54 aims at frictionally engaging the rod 7 when the screwable stopper 5 is screwed with the fitting tool 6 in the longitudinal bore 42 of the socket.

The screwable stopper can be any of a variety of different types of closure structures for use in conjunction with the present invention with suitable mating structure with the inner surface of the wall 41 of the socket 4.

As shown in Fig. 4, the body 51 of the stopper 5 comprises a longitudinal through hole 55 extending along a longitudinal axis Z-Z' of the stopper 5. The through hole 55 aims at receiving the fitting tool 6 for screwing the stopper 5 within the longitudinal bore 42 of the socket. The geometry of a transverse section of the through hole 55 can be of any type usually encountered in the field of pedicular bone screws such as a triangular, square, pentagonal, hexagonal or octagonal section. According to the invention, screwable stopper 5 further comprises a resilient annular member 56 clipped onto said annular collar 53 over the lip 54. That annular resilient member 56 can be of rubber or in any biocompatible resilient material such as PEEK (Polyether ether ketone), PCU (Polycarbonate Urethane), UHMPWE (Ultra- high-molecular-weight polyethylene) or the like.

The resilient member 56 advantageously prevents the screwable stopper 5 once inserted and screwed in the longitudinal bore 42 of the socket 4 to disassemble from said bore and stopper 5 under vibrating or mechanical stress to the wall 41 of the socket 4. This contributes to an advantageous effect of the anchoring system 1 of the invention, which is to allow a setting of the stopper 5 in the socket 4 in a pre- locking position wherein there is a thin gap or clearance S of a few tenths of millimeters between the lip 54 of the stopper and the rod 7 in the U-shaped channel for the surgeon to be able to bend in-situ the rod before locking the screwable stopper 5 onto said rod during a surgical procedure.

The anchoring system 1 of the present invention further comprises a fitting tool 6 for screwing and setting in position the screwable stopper 5 within the longitudinal bore 42 of the socket 4 of the bone screw 2.

Advantageously according to the invention the fitting tool 6 is very like a screwdriver and basically comprises an elongate cylindrical shank 61 at a first end 62 of which a handle part 63 is formed and at a second end 64 of which an engaging part 65 is formed opposite to the handle part 63.

The handle part 63, the elongate shank 61 and the engaging part 65 of the fitting tool 6 all extend coaxially along a longitudinal axis Y-Y'.

Preferably, the handle part 63 is substantially cylindrical and has larger diameter than the elongate shank 61, which in turn also has a larger diameter than the engaging part 65. The handle part 63 further preferably comprises a corrugated or rough external surface 66 to provide an easy and firm grip by hand and a good transmission of torqueing efforts from a hand to the fitting tool 6.

Moreover the engaging part 65 of the fitting tool 6 comprises a coupling section 651 extending from the elongate shank 61 and terminated by a cylindrical tip 652 joined to the coupling section 651 by a fillet 653. Preferably, the coupling section 651 of the engaging part 65 has a non- revolutional tapered shape, and more preferably a shape corresponding to the shape of a transverse section of the through hole 55 of the screwable stopper, a pentagonal or hexagonal tapered shape for instance. Such a shape is preferably chosen to help efficient torque transmission from the fitting tool 6 to the closure screwable stopper 5 as shown in fig. 1 and fig. 5.

Still preferably according to the invention, the tapered shape of the coupling section 651 and the dimensions (width, depth) of the through hole 55 of the stopper 5 are chosen such that the contact between said coupling section and said through hole 55 is linear and not planar, i.e. the peripheral contact on the coupling section 651 is linear when said coupling section is inserted in the through hole 55.

Moreover according to the invention, the cylindrical tip 652 of the engaging part 651 of the fitting tool 6 is thinner than the coupling section 651, i.e. the tip 652 has as smaller diameter than the smallest dimension of the coupling section 651 taken in a plane perpendicular to the longitudinal axis Y-Y' of the fitting tool 6. As shown in the figures, the end of the cylindrical tip 652 can be flat but it can also be round or adopt any other form.

According to the invention and as shown in Figures 5 to 8, the coupling section 651 of the fitting tool is further designed such that the tip 652 goes beyond the lip 54 of the annular collar 53 when the fitting tool 6 is inserted in the through hole 55 of the screwable stopper 5. Thanks to this particular design and as illustrated in Fig. 5 the tip 652 protrudes in front of the lip 54 of the screwable stopper 5 and therefore comes in abutment against a rod 7 seated in the U-shaped channel 44 of the socket before the lip itself touches said rod.

That protruding tip 652 combined with the conic shape of the coupling section

651 chosen to have only a linear contact between the fitting tool and the screwable stopper 5 during screwing of the stopper 5 inside the through hole 55 provides the capacity to the fitting tool 6 to ensure screwing of the screwable stopper in the socket 4 for a determined length up to a position within the longitudinal bore 42 where the lip 54 of the stopper is just about to touch the rod 7 in the U-shaped channel 44 but does not touch it, leaving a small gap S of a few tenths of millimeters between said lip 54 and said rod 7.

According to the invention, the engaging part 65 of the fitting tool 6 is configured to engage the through hole 55 in the screwable stopper 5 such that the fitting tool 6 is automatically released from the screwable stopper 5 once it has been screwed in the socket 4 for a determined length.

The tip 652 being thinner that the coupling section 651 and therefore thinner than the through hole 55, said stopper 5 loses contact with the pans of the coupling section 651 of the fitting tool 6 when the tip 652 has touched the rod 7 in the U- shaped channel 44, releasing the stopper 5 from torqueing engagement with the fitting tool 6 just a few tenth of millimetres before its lip 54 touches the rod 7 as well.

As a consequence, the tip 652 and conic shape of the coupling section 651 of the fitting tool 6 form a reference for the maximum screwing length of the screwable stopper 5 along axis X-X' in the socket 4 to prevent the stopper from touching the rod 7.

This is a particularly advantageous feature of the anchoring system 1 of the invention as it can help surgeons pre-locking the screwable stopper 5 in position into the socket 4, leaving a gap S between said stopper 5 and a rod 7 thereby allowing translation of the rod 7 into the U-shaped channel 44 and bending in-situ of the rod to implement a required correcting configuration of the rod 7 before locking it in place in patient's body.

Advantageously, the gap S is determined such that:

S≤ D - [H + d)

Where D is the depth of the U-shaped channel 44, H is the height of the screwable stopper 5 and d is the diameter of the rod 7.

So the conic shape of the coupling section 651 and length of the tip 652 of the fitting tool 6 of the invention are configured and chosen such that a linear contact between the coupling section and the screwable stopper 5 is achieved when inserting the fitting tool 6 in the screwable stopper 5, said linear contact intervening on the at a distance T₀=H+S from the end of the tip 652. The gap S allows a manual displacement and bending of the rod 7 in the head of the pedicular bone screw 2 by the surgeon before locking it firmly in place with the screwable stopper 5.

When the appropriate bending of rod 7 has been carried out, the surgeon only has to lock the stopper 5 by screwing it tightly against the rod 7 using a conventional screwdriver, which is not part of the inventive system of the present invention.

Once pre-locked in position in the socket 4, the screwable stopper 5 cannot disassemble from said socket thanks to the resilient annular member embedded around the annular collar 54 of the stopper 5, which holds the stopper 5 in place by friction against the internal thread 8 of the socket 4.

Consequently, the anchoring system 1 of the present invention provides a secure and reliable system for surgeons to implement the in-situ bending technique of correction rods in spine surgery and circumvents the incompatibility between the classical locking systems using pedicular bone screws and the in-situ bending technique.

It should also be considered that the anchoring system of the present invention is not limited to the in-situ bending technique and can also be used in any other correcting technique implementing rods in spine surgery.

It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown.

Claims

1 - An anchoring system (1) comprising:

- a vertebral anchoring device (2) for fixation on at least one vertebra, and

- a socket (4) for receiving and fastening a corrective device (7), said socket (4) comprising a longitudinal bore (42) extending about a longitudinal axis (Χ-Χ') and a receiving channel (44) for a said corrective device, and

- a screwable stopper (5) to be screwed in the longitudinal bore (42) of the socket (4) by means of a fitting tool (6) to bias said corrective device (7) into said receiving channel (44) of the socket and lock said corrective device in position within the receiving channel,

wherein the screwable stopper (5) comprises at least one resilient member (56) preventing disassembling of said stopper (5) from the longitudinal bore (42) of the socket (4) once the stopper has been inserted therein.

2 - An anchoring system according to claim 1, wherein the screwable stopper (5) comprises a cylindrical body (51) comprising a buttress external thread (9) being complementary with a corresponding buttress internal thread (8) on the internal surface of a wall (41) of the socket (4).

3 - An anchoring system according to any of claims 1 or 2, wherein the screwable stopper (5) comprises an annular collar (53) accommodating said resilient member (56).

4 - An anchoring system according to claim 3, wherein said collar (53) extends beyond said external thread (9) at a bottom (52) of the body (51) of said screwable stopper (5).

5 - An anchoring system according to claim 3 or 4, wherein said collar (53) comprises a lip (54) forming a shoulder extending radially and about which said resilient member (56) is clipped.

6 - An anchoring system according to any of claims 3 to 5, wherein the diameter of said collar is lower than the diameter of external thread (9) of said screwable stopper (5).

7 - An anchoring system according to any of claims 1 to 6, wherein said resilient member (56) is a bushing ring. 8 - An anchoring system according to any of claims 1 to 7, wherein the resilient member (56) is made of polymer.

9 - An anchoring system according to any of claims 1 to 8, further comprising a fitting tool (6) to fit the screwable stopper into said socket (4) by means of screwing wherein said fitting tool (6) comprises an engaging part (65) configured to engage said screwable stopper (5) such that the fitting tool is automatically released from the screwable stopper (5) once it has been screwed in a said socket (4) for a determined length.

10 - An anchoring system according to claim 9, wherein the screwable stopper (5) comprises a longitudinal through hole (55) having an internal shape adapted to mate the shape of the engaging part (65) of a fitting tool (6).

11 - An anchoring system according to claims 10, wherein the engaging part (65) of the fitting tool comprises a tapered coupling section (651) and a cylindrical tip (652) protruding from the through hole (55) of the screwable stopper (5) to abut against a corrective device (7) lodged into the receiving channel (44) of the socket (4) before the screwable stopper (5) when said stopper (5) is screwed with the fitting tool (6) in the socket and manage a clearance (S) between said stopper and said corrective device and forcing disengagement of the fitting tool (6) from the screwable stopper (5).

12 - An anchoring system according to claim 12, wherein the tapered shape of the engaging part (65) of the fitting tool (6) is such that the contact between said engaging part (65) and said through hole (55) of the screwable stopper (5) is linear.