KR20130127786A - Pedicle screw locking system - Google Patents

Abstract

The low height spinal fixation system includes one or a plurality of multi-axis pedicle screws, and the connection assembly includes one or a plurality of inward offset clamps having a cylindrical band assembled to the connection rod with sliding stable frictional stability. Connection assembly and annular flange. Each inward offset clamp is assembled to a corresponding multi-axis pedicle screw and forms a small angle auto locking hoop that forms stable temporary stability by the application of small compression forces. Each clamp is further fixed on the pedicle screw using a fixing nut coupled on the pedicle screw, and the position of the connecting rod is more firmly fixed on the clamp by elastic deformation of the clamp flange and the cylindrical band. In the fully fixed position the clamp flanges are brought into load-bearing contact, resulting in multiaxial orientation and assembly strength of the final assembly.

Description

Pedicle screw locking system

The present invention relates to a pedicle screw locking system, and more particularly to a pedicle screw locking system used for the correction of spinal disorders.

In a typical multi-axis pedicle screw system, the clamp is assembled to the pedicle screw prior to installing the pedicle screw in the bone. However, the inherent randomness of the pedicle screw installation necessitates an independent clamping system that is assembled on the pedicle screw after the clamp is installed in the bone. An independent clamp system allows for efficient and hassle-free selection and adjustment of the position of the clamps and rods to achieve the desired final position of the spinal column's spine without the need to adjust the position of the pedicle screw. Although many desired objects are achieved by prior art systems, they have the contradictory features and have the disadvantage of not reaching the completion of a well-functioning stable multi-axis system.

US patent application 2007/0233062 discloses an offset stabilization system that presents a multi-angle pedicle fixation and low height. This system limits the choice of surgery for alignment of the spine, since the fixing bracket must be assembled to the pedicle screw prior to implantation.

US patent 7335201 discloses a system with pedicle screws having a spherical connector with conical cavities. U. S. Patent 7335201 uses a number of additional elements such as toggle bolts, split retaining rings, collets, clamps. In addition, special press tools and drivers are required to successfully complete the assembly. Similarly, U.S. Pat.Nos. 5,562,40,6050997 and 6623485 use toggle bolt split rings, secondary screws, and the like to achieve multi-axis positioning. However, the complexity of the system and the stack height of the components render these systems useless.

U.S. Patent No. 5938663 and U.S. Patent Application No. 2007/0161987 show multi-angle stabilizing rod characteristics between the rod and the fixing bracket. U.S. Patent No. 5938663 and U.S. Patent Application No. 2007/0161987 also disclose an offset stabilization system that allows axial positioning of a securing bracket relative to a pedicle screw. However, such systems are inherently unstable because of the possibility of distorting the position of the components at the junction of the rod and the bracket.

U. S. Patent No. 5084048 discloses a single spherical connection integral with a pedicle screw, but additional convex or flat washers are required to achieve stable attachment. As disclosed, the system has a high axial height by stacking each component element in the order of spherical pedicle screw element, fixing bracket flanges, washer element, fixing nut and pedicle screw driver. In addition, the almost vertical contact areas of the assembled parts are locked to the position of the stabilizing rod relative to the fixing bracket before the position of the fixing bracket is fixed on the pedicle screw. As a result, undesirable properties are obtained for the necessary position adjustment of the vertebral addition. Furthermore, almost axial locking requires opposing surfaces to be roughened to increase frictional resistance to achieve proper final stability.

US Pat. No. 6,043,43 discloses a spherical connection between a pedicle screw and an offset connector element having a secondary set screw that secures the connecting rod to the connector. Advantageously the surface relationship of the spherical connections is improved by forming incomplete contact. However, high torques must be applied to induce deformation of the material for deformation of the curvature of the locking dome to achieve a secure fixation.

In summary, prior art systems using offset fixation of connecting rods used for stabilization of the spine are high. In addition, prior art systems use ancillary secondary components to achieve multi-axis positioning and locking. In addition, prior art systems require high torque and uneven surfaces to achieve locking of the components of the system.

The assembled system preferably presents an extremely low height in order to reduce the action of stimulating tissue, such as a high system, as in the prior art.

The multi-axis system also preferably uses a single fastening nut to lock the position of the assembly and the minimum number of parts required to complete the assembly.

In addition, the positioning of the parts is preferably locked sequentially. That is, it is preferable that the relative multiaxial orientation of the first assembly elements is locked, and the linear distance of the second weight is locked. This locks the clamp on the first pedicle screw, thereby fixing the orientation while allowing the rod to slide linearly within the clamp by appropriate friction restraints, and the necessary compression / tension between the second weights. It is achieved by fixing the rod position on the clamp after it is formed.

The multi-axis system also takes advantage of the mechanical advantages of morphological relationships between components such as the small angular contact of automatic locking and lever arm compression to reduce the need for high torque for reliable assembly.

It is an object of the present invention to substantially or significantly improve an existing multi-axis pedicle screw system by providing a component assembly of extremely low height.

It is a further object of the present invention to provide a system for installing pedicle screws regardless of the assembly parts and subsequent connecting clamps and rod dimensions and shapes.

It is a further object of the present invention to provide a system which minimizes the number of parts required for assembly during the surgical procedure.

It is a further object of the present invention to lock the axial position of the clamp on the pedicle screw with approximately 30% final assembly torque (automatic locking), while allowing the slide of the rod within the clamp to adjust the proper fluctuation of the vertebrae. And lock the assembly sequentially by locking the assembly to the desired 100% final assembly torque by fastening the locking element to a fully clamped position using 75% of the final assembly torque. Nuts).

It is a further object of the present invention to provide automatic locking of the clamp to the pedicle screw, resulting in lower torque applied to the pedicle screw, and consequently the secondary fastening features required to stabilize the pedicle screw during the locking procedure. To remove it.

In order to achieve the above object, a pedicle screw locking system according to a preferred embodiment of the present invention comprises an intermediate structure formed between the body of the pedicle screw and the stud of the pedicle screw, and having a truncated spherical surface; A clamp having a truncated spherical surface having an annular flange in contact with the inner side and a cylindrical band for receiving the connecting rod, the clamp connecting the pedicle screw and the connecting rod to each other and clamping the connecting rod; And a locking member fastened to the stud penetrating the flange and applying locking pressure to the assembly in which the pedicle screw, the clamp, and the connecting rod are assembled.

Preferably, the intermediate structure has a center of sphere coaxial with the axis of the pedicle screw, and the truncated spherical surface comprises a recessed surface disposed about the axis of the pedicle screw.

The flange includes an upper flange of a spherical dome shape having an opening and a lower flange forming a hoop, and the upper flange and the lower flange are in contact with each other.

The connecting rod is slid into the band to form the assembly, and the clamp is pressed so that the upper flange and the lower flange are brought into close contact with each other by the locking member to secure the connecting rod by forming a contact in the mutually locked state.

The upper flange includes a spherical dome surface configured to have a center coaxial with the center of the pedicle screw, and the lower flange includes a spherical sheet having a center coaxial with the center of the pedicle screw.

The upper flange includes an annular opening that is larger than the working diameter of the stud and smaller than the working diameter of the rim sheet of the locking member.

The lower flange has a tapered through bore that forms a sheet surface configured for automatic locking rim contact with the truncated spherical surface of the pedicle screw.

The locking member has a bottom with depressions, and the depressions make contact with the upper flange to support the rim load.

The band is elastic.

The present invention as described above has the advantage of using only three components, pedicle screws, clamps and a single nut fastener, to achieve a firm multi-axis connection from the vertebra to the connecting rod. Furthermore, the offset of the final assembly, ie the inward spacing from the pedicle screw to the connecting structure, can be changed by varying the dimensions of the intermediate connecting structure without changing the scope and function of the present invention. These offsets can be oriented vertically, angularly, or inwardly, and also allow for isolation of assembly components from existing vertebral bone structures, such as facets, as well as additional misalignment to allow for straight misalignment. Surgical options may be provided. This is a great advantage since the surgeon does not have to modify the shape of the connecting rod.

The main objectives are achieved by minimizing the effect of lamination of parts and typical features of prior art assemblies. The overall height of the assembly is calculated as the distance from the vertebrae to the top of the assembly. Similar to the prior art, the inwardly directed clamp typically reduces the assembly height occupied by the rod. An improvement of the present invention over this prior art is to further reduce the height of the assembly by truncating the spherical locking surface into an equatorial band and integrating the pedicle screw fastening feature within the vertical height of the spherical surface. It is to let. Further objects are achieved by increasing the contact pressure by a factor of ten by configuring the dimensions and position of the annular seat of the lower flange to an angle of incidence that is typically five degrees of contact angle with the spherical locking surface. This advantageous feature allows the surgeon to temporarily lock the multiaxial orientation by applying a thumb pressure on the assembly to the clamp and connecting rod. An additional automatic locking feature also uses a lower tightening torque to further improve assembly strength, which not only further improves ease of installation but also eliminates the additional tool and implant features required in prior art assemblies where automatic locking is not possible. . A further improvement facilitated by the automatic locking of the clamp is that the multiaxial position of the clamp with respect to the pedicle screw is maintained and that the linear adjustment of the vertical gap between the vertebrae can be made before the final locking takes place. This is achieved by the initial engagement between the clamp and the connecting rod by sliding friction. The clamp has a cylindrical band of small dimension, the flanges elastically open when the rod is assembled to the clamp, and the rod forms a stable but frictionally stable assembly. This not only facilitates the manipulation of the multiple clamps during assembly to the pedicle screw, but also increases the pressure of the nut during surgery to allow adjustments to press or release the position of the vertebrae, while the locking nut is used to Guaranteed locking after pressurizing to the closed position.

1 is a partially exploded perspective view of a pedicle screw assembly;
2 is a partial cross-sectional detail view of a preferred embodiment showing contact of spherical clamp / pedicle screws;
3 is a partial cross-sectional view of another embodiment showing contact of a tapered rim clamp / pedicle screw;
4 is a perspective view of a pedicle screw of the preferred and alternative surfaces used to insert the pedicle screw onto the spinal pedicle;
5 is a perspective view of the clamp shown from above and below;
6 is a partial cross-sectional view of a preferred embodiment showing a clamp and rod preassembled to a pedicle screw;
7 is a plan view of the clamp of the preferred and alternative embodiments showing the offset of the connecting rod.

The present invention discloses an improved low height pedicle screw locking system that uses an inwardly offset stable rod. This system is mainly for use in the correction of spinal disorders. The vertebra here is fixed with rods installed substantially parallel to the axis of the vertebra and fixed to the vertebra with pedicle screw fixation. The rods are generally attached to the pedicle screw by the use of a number of clamping methods, and by the desired positioning of the support and these rods the vertebrae can be in proper alignment and fixed.

The parts of the present invention provide a complete assembly by using at least two bone fixation structures, such as pedicle screws, one or a plurality of link structures, such as connecting rods, and fixing nuts simultaneously with connecting the pedicle screws to the connecting rods. It includes an intermediate connection structure such as a clamp for fixing the.

Each of the pedicle screw units has an intermediate structure having a truncated spherical band with surfaces having recesses configured to engage distal bone fixation screws and proximal mechanical fixation screws and pedicle screw fastening mechanisms. Include.

Each intermediate structure includes a cylindrical band configured to receive a linkage structure and two annular flanges, the inner one of the two annular flanges being configured to receive a spherical band of pedicle screws in a nearly radial contact state with the press assembly. An upper spherical shape having an annular seat forming an hoop stress automatic locking engagement on the upper flange, the upper flange configured to be concentric to the spherical band of the pedicle screw, on the final press assembly to the pedicle screw Has a surface.

Each of the bone anchoring structure and the intermediate connecting structure on the assembly is locked in the desired position by a mechanical locking structure such as a nut. The nut has an inner recess and a larger diameter rim than the annular opening of the upper flange to form angular rim contact with the spherical surface above the intermediate connecting structure described above.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would unnecessarily obscure the gist of the present invention.

For clarity of the invention, the same or similar elements as those of the alternative embodiments among the elements of the embodiments have been indicated using the same reference numerals. In order to clarify the morphological and positional criteria, parts assembled in the locked state have been disclosed.

1 is a partially exploded perspective view of a pedicle screw assembly, showing a pedicle screw 1, a medial clamp 2, a retaining nut 3, and a connecting rod 4 assembled to the clamp 2. Illustrated. The axis 5 of the pedicle screw 1 and the axis 6 of the connecting rod 4 do not cross each other. The assembly can be locked in a multiaxial orientation of these axes. The pedicle screw 1 has an intermediate structure 9 having a proximal threaded stud 7, a distal threaded body 8 configured for bone fixation, and a truncated spherical surface 10. . In a preferred embodiment the spherical surface 10 has a recess 11 as a flat subsurface having dimensions configured to engage a driver (not shown) for inserting and securing the pedicle screw 1 into the spinal pedicle bone structure. Shows. The clamp 2 shows annular flanges (proximal flange 12 and distal flange 13) and a cylindrical band 14 configured to receive a rod 4 before being assembled to the pedicle screw 1. The flanges 12 and 13 have generally parallel adjacent surfaces that are capable of pressure contact along the interface 15. The threaded stud 7 typically has a thread for receiving the nut 3. The nut 3 locks the assembly to the final installation position by applying a pressure contact pressure on the spherical dome surface 16 of the upper flange 12.

FIG. 2 shows a typical partial cross-sectional view of an assembly of a preferred embodiment of the invention, which assembly comprises a multiaxial pedicle screw 1, a clamp 2 in a finally assembled and locked position, and vertebral pedicles (shown in FIG. A connecting rod 4 adapted to connect at least two clamps to at least two screws provided on the assembly), and a nut 3 for applying a locking pressure on the assembly. FIG. 2A is an enlarged detail view of the portion indicated by the circle of FIG. 2. FIG. In figure 2 the axis 5 of the pedicle screw 1 and the axis 6 of the connecting rod 4 are shown to be perpendicular to each other. The pedicle screw 1 has an intermediate structure 9 having a proximal threaded stud 7, a distal threaded body 8 configured for bone fixation, and a truncated spherical surface 10. . The diameter 17 of the intermediate structure 9 is formed on the outer periphery of the center 18 and is generally disposed in a plane 19 perpendicular to the axis 5 of the pedicle screw 1. The spherical surface 10 also shows the depression 11 as a flat lower surface having dimensions configured to engage a driver (not shown) for inserting and securing the pedicle screw 1 in the spinal pedicle bone structure. The threaded stud 7 is typically formed with a thread adapted to receive the retaining nut 3. The nut 3 exerts a press contact pressure on the spherical dome surface 16 of the clamp 2. The clamp 2 shows annular flanges (proximal flange 12 and distal flange 13) and a cylindrical band 14 configured to receive the rod 4 before assembly of the pedicle screw 1. The proximal flange 12 shows a spherical dome surface 16 configured to have a center coaxial with the center 18 of the pedicle screw 1. The distal flange 13 shows a spherical sheet 19 having a center coaxial with the center 18 of the pedicle screw 1. The fastening nut 3 shows the bottom surface with the depression 20. This depression 20 forms a contact supporting the rim load with the dome surface 16 and presses the proximal flange 12 towards the distal flange 13 along a common interface 15. In final contact and exerts an external force on the line of action penetrating the center 18 to the assembly in all multiaxial orientations of the assembly. The sheet 21 increases the contact force by forming a rim contact fixed at an angular position 24, and the contact force penetrating the center 18 because the spherical dome surface 16 and the spherical surface 10 are concentric. Strengthen multiaxial locking at the line of action. 2 and 2a also show the rim contact area of the spherical multiaxial sheet and the retaining nut. Referring to the distal flange 13, the spherical concave sheet 19 is formed to have the same diameter as the diameter 17 of the sphere, and exhibits a hoop spherical contact at a small angle 23 that is also coaxial with the center 18. . To illustrate a small angle 23 contact that would result in primary multi-axis automatic locking of the clamp 2 to the screw 1, a typical small angle 23 on the order of 5 degrees would give a normal contact force of 10 times the normal contact force for locking. Increase. This automatic locking feature allows the surgeon to pre-assemble the clamp and rod assembly by inserting the clamp and rod assembly onto the installed pedicle screw and by capturing the sheet 19 on the spherical surface 10. The advantage of being able to fix the multiaxial orientation of the clamp and the pedicle screw by applying a thumb pressure on the clamp prior to the assembly and further engagement of the fastening nut 3. The spherical surface 19 advantageously extends in a cylindrical shape towards the distal direction forming the surface 22. This extension increases the thickness of the distal flange 13 so that the distal flange 13 is increased in strength without affecting the overall height of the assembly. The distal extension 22 may form a cylindrical surface or alternatively a taper surface or a tapered surface. Referring to the proximal flange 12, the annular opening 25 is larger in diameter than the working diameter of the stud 7 and smaller in diameter than the working diameter of the rim seat 21 of the nut 3. ) Allows for compressive rim contact with the nut 3 in a multiaxial orientation.

3 is a cross-sectional view of an alternative embodiment of FIG. 2, which is illustrated by reference numerals 19 and 22. FIG. 3A is an enlarged detail view in the circle of FIG. 3. FIG. This alternative embodiment shows an incineration taper sheet 26 for multiaxial contact. Sheet 26 shows an incineration rim contact 32 with a normal contact force line penetrating the center 18 of the spherical surface 10. Since the surface 22 extends in the distal direction to increase the thickness, the strength of the distal flange 13 is advantageously increased without affecting the overall height of the assembly. To illustrate the small angle 23 taper contact, which results in primary multi-axis automatic locking of the clamp 2 to the screw 1, a typical small angle 23 on the order of 5 degrees is 10 times the normal contact force for locking. Increase it. This automatic locking feature allows the surgeon to temporarily fix the multiaxial orientation of the clamp and the connecting rod by applying pressure with the thumb on the clamp, resulting in stabilization of the assembly prior to assembly and engagement of the nut 3. There is this. Further details are substantially similar to those disclosed in FIG. 2.

4 is a perspective view of a pedicle screw having a preferred surface and an alternative concave surface used for screw insertion on a spinal pedicle; 4A shows a preferred embodiment with a spherical surface 10 showing depressions 11, wherein the depressions 11 insert and fasten pedicle screws 1 into the spinal pedicle bone structure. To a hexagonal flat lower surface with dimensions and shapes such that a hexagon socket driver (not shown) is engaged. 4B shows an alternative embodiment with a spherical surface 10 showing depressions 27, wherein the depressions 27 have four grooves symmetrically disposed on the outer periphery of the spherical surface 10. A subsurface in the form of a groove having dimensions and shapes adapted to form. A correspondingly shaped driver (not shown) fitted to the pattern formed by the grooves 27 is used to insert and fasten the pedicle screw 1 into the spinal pedicle bone structure.

5 is a perspective view from above and below of the clamp; 5A is a perspective view from above of a clamp illustrating the spherical surface 16 and the annular opening 25 of the upper flange 12. The upper flange 12 and the lower flange 13 are connected by a cylindrical band 14 having an axis 6 and adapted to engage the connecting rod 4 (not shown). The upper flange 12 and the lower flange 13 have surfaces that are generally parallel and contact along a common interface 15. 5B is a perspective view from below showing a clamp illustrating the tapered surface 26 of the lower flange 13.

6 is a partial cross-sectional view of the assembly of the preferred embodiment illustrating an initial preassembled state before the nut 3 is engaged with the upper flange 12. The cylindrical band 14 has a small dimension so that when the connecting rod 4 is assembled in the cylindrical band 14, the upper flange 12 and the lower flange 13 are spaced apart to form a gap 15A, and the rod is sliding. Is possible, but it is easier to manipulate the plurality of clamps during insertion of the clamps on the pedicle screw by forming a stable assembly with frictional forces. Further tightening of the nut 3 contacts the flange 12 and the clamping force exerted on the rod 6 gradually increases. The final locking position is achieved by the flanges elastically deforming to form the final clamped contact as shown in FIGS. 2 and 3. Gradual increase in the clamping force exerted on the rod 6 when the flange 13 is in the automatic locking hoop contact allows for adjustment of the pressing force or position of the vertebrae during surgery.

7 is a plan view of the clamp of the preferred and alternative embodiments showing cylindrical band offsets, wherein axis 6 and base axis 29 are common criteria for comparison of alternative embodiments. FIG. 7A shows a clamp 2 of the preferred embodiment as shown in FIG. 1 with a rod axis 6 and a cylindrical band 14 having a base axis 29 of a band perpendicular to the axis 6. ) Is a plan view. 7B shows a clamp of an alternative embodiment having a cylindrical band 32 which is parallel to the axis 6 and has a rod axis 31 offset inward relative to the axis 6 of the clamp 2. 30) is a plan view. 7C shows an alternative embodiment with the band base axis 35 offset angularly relative to the band base axis 29 of the clamp 2 and with the rod axis 6 of the cylindrical band 34. Top view of the clamp 33. 7D shows an alternative embodiment with a band base axis 38 parallel to the axis 29 and offset in the direction of the axis 6 and with a rod axis 6 of the cylindrical band 37. Top view of the clamp 36. Further alternative embodiments may be envisaged in addition to the above alternative embodiments, and such further alternative embodiments may be clamps having both an inward offset of clamp 30 and an angular offset of clamp 33. It may include.

Preferred and alternative embodiments of the invention provide separate methods and implantation steps.

 First, pedicle screws are implanted in a suitable pedicle. Second, the offset of the pedicle screws using a temporary device such as an experimental component arrangement of the dimensions and shape of the clamps available, an alignment caliper measuring the vertical offset between the multi-axis centers of the pedicle screw, and a temporary connecting rod. Determine the relationship and select the clamps and rods necessary to achieve the physician's intended calibration goals.

Third, the appropriate clamp corresponding to the offset relationship desired by the surgeon is assembled to the appropriate connecting rod. This assembly is advantageously stabilized by frictional forces, and the position and orientation of the clamp can be easily adjusted for the alignment of the pedicle screw. Fourth, insert an annular clamp opening on the locking stud proximal of the corresponding pedicle screw, apply the pressure of the thumb to press each clamp onto the middle spherical structure of the pedicle screw, and apply the automatic locking characteristics of the clamp. Effectively installs the assembly of rod and clamp by stabilizing the alignment and orientation of the assembly.

Finally, the clamping nut is engaged by assembling the retaining nut to the locking stud and proceeding further. In this step, the orientation of the clamp relative to the pedicle screw is locked due to the automatic locking characteristics of the present invention. In addition, the connecting rod is still slidable by means of a gap, and the pressing mechanism for final pressing / depressing adjusts the assembly for correction of the positional relationship of the vertebral body. Further advance of the locking nut causes the clamp to deform and ultimately lock the position of the clamp relative to the connecting rod. Further advance of the locking nut to the final locking position coincides with the center of the upper dome sphere and the spherical center of the pedicle screw, resulting in a fully stable and locked assembly. The ability of the present invention to provide gradual, stepwise locking of component elements gives the surgeon significant importance in surgical techniques that provide good control of the implant and control process.

Claims (9)

An intermediate structure formed between the body of the pedicle screw and the stud of the pedicle screw, the intermediate structure having a truncated spherical surface;
A clamp having a truncated spherical surface having an annular flange in contact with an inner surface and a cylindrical band for receiving the connecting rod, the clamp connecting the pedicle screw and the connecting rod to each other and clamping the connecting rod; And
And a locking member fastened to the stud penetrating the flange and applying locking pressure to the assembly in which the pedicle screw, the clamp, and the connecting rod are assembled. The method according to claim 1,
The intermediate structure has a center of sphere coaxial with the axis of the pedicle screw,
And the truncated spherical surface comprises a recessed surface disposed about an axis of the pedicle screw. The method according to claim 1,
And the flange comprises an upper flange of a spherical dome shape having an opening and a lower flange forming a hoop, wherein the upper flange and the lower flange are in contact with each other. The method according to claim 3,
The connecting rod slides on the band to form the assembly,
And the clamp is configured to secure the connecting rod as the upper flange and the lower flange are pressed against each other by the locking member to form a contact in a mutually locked state. The method according to claim 3,
The upper flange comprises a spherical dome surface configured to have a center coaxial with the center of the pedicle screw,
And the lower flange comprises a spherical sheet having a center coaxial with the center of the pedicle screw. The method according to claim 3,
And the upper flange comprises an annular opening larger than the working diameter of the stud and smaller than the working diameter of the rim sheet of the locking member. The method according to claim 3,
And the lower flange has a tapered through bore forming a sheet surface configured for automatic locking rim contact with the truncated spherical surface of the pedicle screw. The method according to claim 3,
And the locking member has a bottom having a depression, the depression forming a contact supporting the upper flange and the rim load. The method according to claim 1,
And said band has elastic force.

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