JP2002528218A - Fixing device with deformable set screw - Google Patents

Abstract

The anchor assembly (12) to be implanted has a hook (18) for securing the anchor (13) to the spine or other osseous body and a cylinder for receiving an elongated cylindrical stabilizer rod (11). An anchor (13) with a recess (19) having a profile. The anchor assembly (12) further includes a set screw (14) with an external thread corresponding to the internal thread (22) of the anchor (13). The set screw (14) is advanced toward the rod (11) by turning the set screw (14) in the anchor (13) while the rod (11) is resting in the recess. The leading edge region of the set screw extends generally laterally across the set screw (14) and forms a thin wall forming a concave / convex dome (27) that is convex in a direction toward the stabilizer rod (11). (27). After the dome (27) comes into contact with the rod (11), the dome (27) is deformed by turning the set screw (14) further, so that the outer surface of the dome (27) tries to match the rod (11). The rod (11) is more securely held in the recess (19) of the anchor.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates to orthopedic implant components, and more particularly to anchors for securing a stabilizing rod to bone material.

[0002] Increasingly accepted surgical techniques for treating vertebral joint fusion and spinal disorders such as, for example, scoliosis, involve hard interlocking or stabilizing bony elements relative to a single anchor. Including the use of clothing. Such internal fixation devices typically include an elongated rod and several anchors. Each anchor includes a hook or other structure to facilitate fixation to the bone material and a coupling structure that forms a releasable engagement with the elongated rod. Thus, the rod can be used in combination with two anchors to secure two vertebrae or other bone elements together with respect to each other.

One example of this solution is described in (Puno et al.-Puno, et al) US Pat.
96, 321 is a spinal implant assembly. The implant assembly includes an elongate rod and a top load anchor with hooks for securing to a spinal member. The anchor has a seat defining a recess for receiving the rod, and opposite walls with grooves extending longitudinally, i.e., parallel to the length of the rod. The closure member also has a recess for receiving the rod and further has a longitudinally extending shoulder on each side. The shoulder is received in the groove and allows the closure member to slide longitudinally into engagement with the seat. An internally threaded opening extends transversely to the rod through the closure member to receive a set screw having an external thread. A countersink in the set screw accepts the drive tool, and a beveled beveled tip improves gripping of the set screw on the rod.

While such devices may work in a variety of situations, they require special equipment with a boss and a fork-like head containing a spring-loaded plunger ball as shown in FIG. 11 of the patent. Apart from requiring this tool for insertion, the closure does not contribute to the gripping force on the rod, but rather is pushed away from the rod as the force is distributed between the seat and the set screw. More universally, the number of required elements adds to the cost and complexity of the device.

Accordingly, it is an object of the present invention to provide an anchoring device that reliably anchors the spine or other bone components to one another.

Another object is to provide an anchor assembly for securing an elongated stabilizer rod to bone material that minimizes the number of moving parts and does not require complex tools in use.

[0007] Yet another object is to easily conform to the shape of a stabilizing rod or other stabilizing member,
It is an object of the present invention to provide an anchor assembly which provides a more secure friction grasp for a stable member.

[0008] Yet another object is to provide an implantable orthopedic fixation device and anchor assembly that is more reliable, less complex, and less costly to manufacture.

SUMMARY OF THE INVENTION To accomplish these and other objects, an apparatus is provided for securing two or more bony bodies to one another. The device includes a stabilizing member and an anchor adapted to be secured to the first bony body. The anchor has a recess for receiving a stabilizer. The device also includes a retainer adapted to couple to the anchor in such a manner that the retainer can be advanced toward the stabilizer when the stabilizer is positioned in the recess. The retainer includes a leading edge region with a leading edge surface. The leading edge engages the stabilizer when the retainer advances to a predetermined position relative to the anchor. The leading edge region is adapted to deform in response to advancement of the retainer beyond the predetermined location.
As a result of this deformation, the leading edge tends to assume the same shape as the stabilizer. Further, the device includes a coupling structure that integrally couples the stabilizing member to the second bony body. Thus, the coupling structure cooperates with the anchor, the retainer, and the stabilizing member to integrally couple the first and second osseous bodies.

[0010] In a preferred internal fixation device, the stabilizer is an elongated cylindrical rod used in combination with several two-element anchor assemblies. Each anchor assembly includes an integral anchor member that provides a recess for receiving a rod. Each retainer engages the rod and presses the rod firmly against the recess, establishing a frictional engagement that integrally joins the rod with the implant anchor assembly. In order to ensure a more secure connection, the front end area of the retainer is deformable. The leading edge region is the portion of the retainer that first encounters the rod and establishes a surface engagement as the retainer moves toward the rod during the coupling operation. The leading edge region is preferably plastically deformable so that the leading edge of the retainer tends to conform to the contour of the rod, increasing the area of the continuous surface of the retainer and the rod. This means that the longitudinal, along the rod / anchor interface,
Improves the anchor assembly's ability to maintain an integral connection despite rotational and torsional forces.

A preferred retainer member is a set screw with an external saw tooth thread adapted to engage an internally threaded shape formed along the side wall of the anchor. The set screw has a hexagonal or other non-circular recess for receiving a drive tool. Because the end region is deformable, the set screw can be turned inward beyond where it engages the rod.

In a preferred form, the deformable portion of the set screw includes a thin wall extending laterally across the set screw. The exposed outer surface of the wall provides the leading edge surface of the set screw. Before the set screw contacts the rod, the thin wall is forwardly convex to form a dome.
In response to the forward rotation of the set screw after engagement, the rod ultimately exerts a force on the wall that exceeds the elastic limit of the wall. As a result, the wall is permanently deformed, so that the leading edge not only engages the rod, but also substantially conforms to the contour of the surface of the rod.

The thin wall exerts a clamping force on the rod and cooperates with the anchor recess to provide a secure frictional engagement. Further, because of the same shape as the rod, the thin wall resists the tendency of the set screw to loosen. Implantable anchor assemblies are easy to use, each consisting solely of an anchor and a set screw. No other elements are required. The set screw is fixed by a relatively simple tool, typically a screwdriver with a hexagonal blade corresponding to the drive opening of the set screw.

Thus, in accordance with the present invention, a spinal implant assembly employs an anchor assembly with a deformable set screw, eliminating the need for auxiliary elements and special installation tools. The face of each set screw facing the rod assumes a shape that generally matches the contour of the rod as the set screw is turned inward relative to the rod, establishing an effective integral connection between the anchor and the rod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, FIGS. 1 and 2 illustrate an elongated stabilizer rod 11 and an implanted anchor assembly 12 adapted to be releasably secured to the rod. 1 shows a spinal implant device 10 including: Typically, at least two such assemblies are coupled to the rod and further joined to respective vertebrae or other bone elements to secure the vertebrae to one another.

The anchor assembly comprises two integral elements, the implant anchor 13 and the set screw 1
4 is included. The implant anchor includes a base 15, sidewalls 16 and 17 extending upwardly from the base, and hooks 18 extending below the base. Hook 18 is anchor 13
Used to fix bone to bone material. Alternatively, a bracket with an opening for receiving a bone screw may extend from the base 15.

The side walls and the base cooperate to provide a recess 19 having a circular profile that is slightly larger to match the circular profile of the rod 11 so that the rod fits easily into the recess. Each of the side walls has an inner surface 20 and 21 shaped to provide an internal thread 22 in an arcuate shape, as best seen in FIG.

The set screw 14 is an outer screw 23 adapted to threadably engage the inner screw 22 of the anchor.
Is provided. The set screw has a bottom or leading edge 24 that is convex downward as viewed from FIGS. As can be seen from FIG. 1, the set screw is adapted to receive a drive tool with a hexagonal blade with a hexagonal blade and has a centrally located hexagonal drive opening open at the top of the set screw. That is, hollow 25
including. The driving tool may be similar to the driver.

From FIG. 3, it can be seen that the hexagonal recess 25 extends inward (downward as viewed in the figure) to an annular edge 26. Immediately below the edge 26 is a thin, disk-shaped wall 27. The wall 27 is concave / convex, is generally uniform in thickness, and forms an inverted dome that projects below the remainder of the set screw. Thus, the lowest or outermost portion of the set screw is the central region of the wall or dome 27.

[0020] The anchor and set screw may be comprised of titanium or other suitable body compatible metal. Preferably, the leading edge of the set screw is plastically deformable as described above. However, a set screw resiliently deformable at least along the leading edge may be used as an alternative.

The interaction of the set screw 14 and the rod 11 when the set screw is turned into the anchor 13 to connect the rod and the anchor assembly is schematically illustrated in FIGS. FIG. 4 is a partial top view showing the dome 27 located above the rod 11. Turning the set screw clockwise, as indicated by the arrow, turns the set screw forward in FIG. 1 and FIG. 2, that is, downwardly toward the rod. FIG. 5 shows a line 5-in FIG.
FIG. 5 is a sectional view taken along line 5. As can be seen in FIG. 5, the outer or bottom surface of the dome 27 provides the leading edge 24. As the set screw is turned downward, the axially centered forwardmost region 29 of the leading edge meets the rod 11. This may conveniently be considered the initial contact point or the predetermined position of the set screw relative to the anchor and rod.

FIG. 6 is a cross-sectional view similar to FIG. 5, showing the deformation of the dome 27 resulting from the downward movement of the set screw beyond the initial contact point shown in FIG. In a section taken along the axis, the deformation of the dome appears generally symmetric. The deformation of the dome 27 shown in FIG. 6 is, at least in part, a plastic deformation, which is the result of a force exerted by the rod 11 that exceeds the elastic limit of the material forming the dome 27.

FIG. 7 shows a cross-sectional view along a line spaced from the axis of the set screw. The movement of the dome 27 relative to the rod 11 over at least a short distance can be considered to be straight in the direction of the arrow in FIG. Thus, the figure shows an area 30 of the dome that has encountered the rod 11 and has been plastically deformed, and an area 31 of the dome that has not yet encountered the rod. When deformed, the dome 27 undergoes a permanent set, but retains its elasticity. Thus, once the setscrew 14 is turned sufficiently to move the region 30 beyond the rod 11, a slight elastic recovery of the dome that moves the leading edge 24 to a point below the top of the rod 11 as shown. is there. However, region 30 remains above region 31 and reflects the permanent set in the portion of the dome that has moved past the rod.

[0024] Permanent set offers several advantages in combination with at least a slight elastic recovery. First, since the elasticity is maintained, the dome 27 applies a radially inward force to the rod 11 and cooperates with the radially inward force of the anchor 13 along the recess 19 to ensure a secure frictional connection. I will provide a. Second, due to the partial elastic recovery, the dome 27 exerts a radially inward force on either side of the vertical line 32 bisecting the rod 11. As a result, the horizontal components of these radial forces act on both the left and right sides as viewed from FIG. The balanced horizontal force component of the rod with respect to the dome acts similarly in both directions, balancing the tendency of the dome 27 to move with respect to the rod 11. In particular, the component of the horizontal force exerted by the rod 11 on the dome area 30 effectively balances the tendency of the set screw 14 to loosen, which can be seen in FIG. The movement of the dome 27 is required.

FIG. 8 shows the completion of the connection between the implant anchor assembly 12 and the rod 11. The rod is captured between the recess 19 of the anchor and the leading edge 24 of the set screw, i.e., between two surfaces that generally correspond to the cylindrical surface of the rod and cooperate to provide a secure frictional connection. You.

In FIG. 9, the set screw 14 is shown in a cross-sectional side view after being removed from the anchor 13 and the rod. A recess 33 is formed in the dome 27, and shows permanent set due to plastic deformation of the material of the set screw.

FIG. 10 also shows the leading edge 24 of the set screw when removed after coupling to the rod 11. Smear patterns exhibit the property of plastic deformation.

The use of the elongated rod 11 and two or more anchor assemblies in an internal fixation procedure requires first defining a fixation location, for example, a spine where the two or more anchor assemblies are fixed to bone material. Typically, the elongate rod is straight, and whenever more than two anchor assemblies are used, the anchor assemblies need to be aligned. Each anchor 13 is aligned and secured together in the longitudinal rod extension, or is mounted in such a way that the anchor is oriented and the cavity is properly aligned. After installing the anchor, the surgeon positions the elongate rod 11 into the recess of the anchor and then, if necessary, slides the rod longitudinally relative to the anchor to the desired axial position. With the rod 11 positioned in this manner, the set screw of each anchor assembly is turned into the associated anchor member to frictionally and integrally secure the rod 11 within the anchor assembly in the manner described above.

Each set screw is provided by a relatively simple drive tool similar to a conventional driver with a hexagonal head or, alternatively, a separate head with a non-circular profile that matches the non-circular recess of the set screw. Routed into the associated anchor member. With the anchor member already secured, the set screw is the only part that needs to be moved while closing the anchor device.
There is no intermediate part to align during closure.

As mentioned above, the leading edge region of the set screw plastically deforms during closure, and thus has approximately the same profile as that of the rod. This increases the set screw / rod surface contact area for a more stable connection. Another advantage of the deformable set screw is that the desired surface conformance and continuous engagement are achieved without the need for any auxiliary members or elements. The inner anchor assembly consists solely of the anchor member 13 and the set screw 1
And 4. Since there are no additional elements or concerns about their proper positioning and placement, the surgeon only needs to pay close attention to the procedure at hand.

FIG. 11 is a top view of an alternative embodiment of a set screw 34 having a non-circular shaped recess or drive opening 35 as an alternative to the hexagonal shape of the recess 25. Set screw 34 is often referred to as a "torx" set screw. FIG.
Reference numeral 2 denotes a driving tool blade 36 suitable for turning the set screw 34. FIG. 13 shows the hexagonal blade 37 of the drive tool used in connection with the set screw 14. Various other non-circular shapes are also suitable.

FIG. 14 shows three anchor assemblies 39, 4 in combination with a single stabilizer rod 42.
FIG. 14 shows an alternative embodiment of the fixation device 38 employing 0 and 41. FIG. Each anchor assembly includes an anchor 43 and a set screw 44 that is in threaded engagement with the anchor, has a leading edge continuous with the rod 42, and is plastically deformed as described above. The anchor 43 includes a bracket 45 and a bone screw 46. Each bone screw passes through an opening in the associated bracket.
The screws and apertures are described, for example, in "Anterior Cervical Plate and Fixation Device", filed May 19, 1999 and assigned to the assignee of the present patent application.
and the anchor assemblies 39-41 coupled to the vertebrae 47, 48 and 49, respectively, may be rod-shaped, as described in US patent application Ser. In conjunction with 42, the vertebrae are integrally joined to each other.

FIG. 15 is a side cross-sectional view illustrating an alternative embodiment of the set screw 50 engaged with the stabilizer rod 51. The rod 51 is housed in a recess of the anchor, not shown.
The leading edge 52 of the set screw is elastically deformed along the portion of contact with the rod, forming a depression at 53. For example, a set screw 50 formed of a body-compatible, elastically compressible polymer includes an external thread 54 that interacts with a corresponding internal thread (shown) of the anchor. The set screw incorporates a hexagonal recess, ie, a drive opening 55.

Although the invention has been described in relation to fixing the vertebrae to one another, other bone materials or bodies may be fixed to one another using the fixation devices and elements described above. You should understand that. Some applications may require a non-linear stabilizing member instead of a linear stabilizing rod, or a stabilizing rod having a non-circular profile. Further, the fixing device may employ the above-described anchor assembly in combination with other anchor elements that do not involve deformation of the set screw.

Thus, the present invention provides an internal fixation device that is easier to use. Each anchor assembly simply requires two compatible parts, and the assembly is not complicated and does not require special tools. A deformable set screw whose leading edge generally matches the shape of the rod cooperates more reliably with the anchor member to capture the rod in full integral frictional engagement. A simpler and more stable anchor assembly reduces both the cost and complexity of the internal fixation device.

[Brief description of the drawings]

FIG. 1 is a perspective view of an implanted anchor assembly and an elongated stabilizer rod constructed according to the present invention before the anchor assembly is coupled to the rod.

FIG. 2 is an end view of the rod and anchor assembly before coupling.

FIG. 3 is a cutaway perspective view of a set screw of the anchor assembly.

FIG. 4 is a schematic showing the set screw / rod interaction during coupling.

FIG. 5 is a schematic showing the set screw / rod interaction during coupling.

FIG. 6 is a schematic diagram showing the set screw / rod interaction during coupling.

FIG. 7 is a schematic diagram showing the set screw / rod interaction during coupling.

FIG. 8 is a perspective view of the rod and the assembly after being connected.

FIG. 9 is a cross-sectional view of the set screw after coupling.

FIG. 10 shows a smear trajectory along the interface between the leading edge of the set screw and the rod.

FIG. 11 is a top view of an alternative set screw showing an alternative non-circular drive aperture.

FIG. 12 shows a blade of a driving tool used for the set screw shown in FIG.

FIG. 13 shows a set screw having a hexagonal drive opening and a hexagonal blade of a drive tool to be used.

FIG. 14 shows an alternative fixation device including three anchor assemblies coupled to three vertebrae via respective brackets and bone screws in combination with a single stabilizer rod.

FIG. 15 is a side cross-sectional view of a set screw according to an alternative embodiment.

────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Toxi, Leonard, Jay, Jr. Washington, Seattle, Twenty-Fifth Avenue, E, 11510 F-term (reference) 4C060 LL13 LL15 MM24

Claims (37)

[Claims] 1. An apparatus for securing two or more bony bodies to one another, comprising: a stabilizing member; and a recess adapted to be secured to the first bony body and having a recess for receiving the stabilizing member. A first anchor and a first retainer adapted to couple to the first anchor such that the first retainer can be advanced toward the stabilizer when the stabilizer is disposed in the recess. A retainer, wherein the retainer includes a leading edge region having a leading edge surface that engages the stabilizer when the first retainer advances to a predetermined position relative to a first anchor, wherein the leading edge region is A first retainer adapted to deform in response to the first retainer advancing beyond a predetermined position, wherein the leading edge surface attempts to conform to the stabilizing member due to the deformation; The said stabilizing member to the second osseous body Including a first anchor, a first retainer, and a coupling structure for integrally coupling the first and second osseous bodies in cooperation with a stabilizing member. A device for fixing two or more osseous bodies to each other. 2. The device according to claim 1, wherein said stabilizer comprises an elongated rod. 3. The device according to claim 2, wherein said elongated rod is circular cylindrical. 4. The device of claim 1, wherein the first anchor includes a hook that secures the anchor to a first osseous body. 5. The apparatus according to claim 1, wherein the recess is shaped to match the stabilizer. 6. The apparatus of claim 1, wherein a leading edge region of the retainer is plastically deformable. 7. The apparatus of claim 1, wherein a leading edge region of the retainer is elastically deformable. 8. The apparatus of claim 7, wherein the leading edge region is further plastically deformable in response to an external force that exceeds an elastic limit of the leading edge region. 9. The invention of claim 1 wherein said retainer is generally symmetrical about its axis and said leading edge region comprises a thin wall extending generally laterally across said retainer. apparatus. 10. The thin wall has a generally uniform thickness in the direction of the axis of the retainer and has a concave / convex shape so as to define a convex surface of the leading edge in the direction of travel of the retainer. The apparatus according to claim 9, wherein: 11. The apparatus according to claim 1, wherein said first retainer is removably coupled to a first anchor. 12. The first retainer comprises a set screw having an external thread,
The apparatus of claim 11, wherein the first anchor includes at least one anchor wall having an internal thread adapted to engage an external thread of the set screw. 13. The invention according to claim 12, wherein said first retainer includes a non-circular drive opening adapted to receive a drive tool for rotating said first retainer about its longitudinal axis. An apparatus according to claim 1. 14. The apparatus of claim 13, further comprising a drive tool having a non-circular blade shaped to match said non-circular drive aperture. 15. A second anchor, wherein said coupling structure is similar in structure to said first anchor, and is adapted to be secured to a second bony body.
And a second retainer similar in construction to the first retainer, wherein the second retainer is advanced toward the stabilizer when the stabilizer is disposed in the recess of the second anchor. Is adapted to couple to a second anchor, and is deformable in response to further advancement of the second retainer after a leading edge surface of the second retainer contacts the stabilizer. The apparatus of claim 1, further comprising a second retainer whereby the leading edge surface attempts to conform to the retainer. 16. An anchor assembly for securing a stabilizing rod integrally to a bone material, wherein the anchor assembly is adapted to be secured integrally to the bone material and receives and engages the stabilizing rod within a recess. An anchor element having a recess formed therein, and a retainer adapted to couple to the anchor in a manner to advance the retainer toward the stabilizer rod in the receiving engagement relationship, wherein the retainer is brought into position relative to the anchor. And a retainer including a leading edge region, the leading edge surface of which is positioned to engage the stabilizer rod when advancing, wherein the leading edge region deforms in response to the retainer advancing beyond a predetermined position. The leading edge surface tends to coincide with the stabilizing rod, thereby holding the stabilizing rod in the stowed engagement relationship with the stabilizing rod. An anchor assembly, comprising: 17. The assembly according to claim 16, wherein the first anchor includes a hook that secures the anchor to a first bony body. 18. The assembly according to claim 16, wherein said recess is shaped to match said stabilizing member. 19. The assembly according to claim 16, wherein a front edge region of the retainer is plastically deformable. 20. The assembly according to claim 16, wherein a front edge region of the retainer is elastically deformable. 21. The assembly of claim 20, wherein said leading edge region is further plastically deformable in response to an external force exceeding an elastic limit of said leading edge region. 22. The invention of claim 16 wherein said retainer is generally symmetric about its axis and said leading edge region comprises a thin wall extending generally laterally across said retainer. An assembly as described. 23. The thin wall has a generally uniform thickness in the direction of the axis of the retainer and is concave / convex so as to define the leading edge region in a convex manner in the direction of travel of the retainer. 23. The assembly of claim 22, wherein: 24. The assembly of claim 16, wherein said retainer is removably coupled to an anchor. 25. The retainer comprises a set screw having an external thread and the anchor includes at least one anchor wall having an internal thread adapted to engage an external thread of the set screw. The assembly of claim 24, wherein 26. The assembly according to claim 16, wherein said retainer includes a non-circular opening adapted to receive a drive tool for rotating said retainer about its longitudinal axis. 27. An elongated stabilizer having a longitudinal axis and a generally uniform lateral profile, and an anchor having a recess adapted to be integrally secured to the osseous body and adapted to receive said stabilizer. And a retainer adapted to couple to the anchor element in such a way as to advance the retainer toward the stabilizer member when the stabilizer member is disposed within the recess. Responsive to advancing the retainer beyond the predetermined position, the retainer including a leading edge region having a leading edge surface positioned to engage the stabilizing member when the retainer is advanced to a predetermined position. Wherein the leading edge region is deformed so that the leading edge surface attempts to conform to the profile of the elongated stabilizer. Combination. 28. The retainer includes external threads, and the anchor element includes at least one anchor wall having internal threads adapted to receive the external threads, such that the retainer rotates about its axis. 28. The implantable combination of claim 27, wherein the combination is advanced. 29. The combination of claim 28, wherein the axis of the retainer is substantially perpendicular to the longitudinal axis of the stabilizer during the advance. 30. The combination according to claim 28, wherein said retainer includes a non-circular drive opening adapted to receive a drive tool for rotating said retainer. 31. The combination of claim 30, further comprising a drive tool having a non-circular blade shaped to match said non-circular drive aperture. 32. The combination according to claim 27, wherein said elongated stabilizer comprises a cylindrical rod and said outer shape is circular. 33. The combination according to claim 27, wherein a leading edge region of said retainer is plastically deformable. 34. The combination according to claim 27, wherein a front edge region of the retainer is elastically deformable. 35. The combination of claim 34, wherein said leading edge region is further plastically deformable in response to an external force exceeding an elastic limit of said leading edge region. 36. The combination of claim 27, wherein said retainer is generally symmetric about its axis, and wherein said leading edge region comprises a thin wall extending generally laterally across said retainer. body. 37. The thin wall having a generally uniform thickness in the direction of the axis of the retainer and having a concave / convex shape that defines a leading edge in the direction of travel of the retainer. 37. The combination of claim 36, wherein: