US20040068258A1 - Device for fixing bones in relation to one another - Google Patents

Abstract

A device for fixation of vertebral bodies including a longitudinal support with a central axis and n anchoring elements (2≦i≦n). Each anchoring element having a longitudinal axes, a front end, and a back end. The longitudinal axis of each anchoring elements may be arranged at an angle of between 65° and 115° relative to the central axis of the longitudinal support, while the anchoring elements are designed to abut the back end. The anchoring elements may be shaped in the form of a blade toward the front end.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of the U.S. national stage designation of copending International Patent Application PCT/CH00/00654, filed Dec. 8, 2000, the entire content of which is expressly incorporated herein by reference thereto.[0001]
FIELD OF THE INVENTION
• The present invention relates generally to orthopaedic fasteners, and in particular to a device for fixation of vertebral bodies.[0002]
BACKGROUND OF THE INVENTION
• Instabilities in spinal-column motion segments that may be caused by vertebral fractures, degenerative changes, etc. often require that the segments in question be fused. In order to ensure the immobilization of the segments to be fused as required for bone fusion, the corresponding segments are often stabilized with a fixation system. Fixation systems may either be inserted and anchored from the posterior, whereby the anchoring is done by means of bone screws in the pedicles, or from the anterior or antero-lateral, in which case the anchoring is done by means of bone screws in the vertebral bodies.[0003]
• The quality with which fixation systems are anchored is heavily dependent on the quality of the bone structures. This is especially true of antero-laterally anchored fixation systems. The greater the degree of osteoporosis, the greater the danger that the bone screws will cut through the bone when subjected to even small loads. The use of thick screws reduces the risk of cutting through the bone. However, overly thick screws should be avoided lest there be excessive destruction of the bone structure in the vertebral body.[0004]
• Known approaches in the related art for reducing the risk of the anchoring elements cutting through the bone are presented in DE 296 00 879 and in WO 00/10473. These publications deal basically with a hollow screw that is screwed into the vertebral body. The hollow screw does not need to displace a great deal of bone, because a peg of bone maybe left in place in the center of screw. However, when the hollow screw is being screwed in, the vascular supply to the peg of bone left in the center may be impaired, which may lead to complications, especially in osteoporotic bones. Also, in bones with still-functioning repair mechanisms, the hollow screw may be so heavily in-grown that it may be difficult to remove it if the area is to be inspected or, if removed, it will do serious damage to the bone (in some cases, for example, it has proved to be impossible to remove hollow screws inserted into the cervical vertebral column).[0005]
• In connection with the surgical treatment of fractures in long bones, intramedullary stabilization techniques have been developed that, with modification, may also be successfully employed in the spinal column to solve the problem of anchoring anterior and antero-lateral spinal-column fixation systems. Intramedullary pins, for instance, may be used to splint fractured tubular bones by providing an intramedullary connection between the proximal portion of the broken tubular bone and its distal portion. Because of its geometry, however, the intramedullary pin can withstand only minor rotational and axial loads. This may not be potentially problematic as long as the fractured bone is able under axial load to maintain its height and the fracture is more or less diaphyseal. As soon as multi-fragment fractures arise, however, the intramedullary pin typically has to be anchored proximally and distally. In this way, the intramedullary pin can provide not only splinting but, as in the case of the spinal column, may act as a proximately and distally anchored longitudinal support that can transfer forces and moments at all levels from proximal to distal. In the case of the intramedullary pin, the anchoring implants may be screws that are run transversely through the bone and the intramedullary pin on the proximal and distal sides. In patients with osteoporosis and in cases where the fractures lie close to the joint, anchoring the intramedullary pin with screws is often not a satisfactory approach. Also, spiral-twisted blade-shaped implants known in the related art and as used in clinical practice are not particularly suitable for use on spinal column.[0006]
SUMMARY OF THE INVENTION
• The present invention relates to the fixation of bones, and in particular to the fixation of vertebral bodies. In one embodiment, the present invention is comprises a longitudinal support with a central axis and n anchoring elements (2≦i≦n). Each anchoring element having a longitudinal axes, a front end, and a back end. The longitudinal axis of each anchoring elements may be arranged at an angle of between 65° and 115° relative to the central axis of the longitudinal support, while the anchoring elements are designed to abut the back end. The anchoring elements may be shaped in the form of a blade toward the front end. The angle-variable connection of the anchoring elements may be achieved by virtue of the fact that at the back end each anchoring element comprises means for receiving the longitudinal support with attachment means that can be controlled from the back end for reversibly locking the connection between the longitudinal support and the anchoring element. The locked connection may prevent relative movement between the longitudinal support and the anchoring element and takes up forces and moments in all three axial directions of a three-dimensional coordinate system.[0007]
BRIEF DESCRIPTION OF THE DRAWINGS
• Preferred features of the present invention are disclosed in the accompanying drawings, wherein similar reference characters denote similar elements throughout the several views, and wherein:[0008]
• FIG. 1 is a top view of an embodiment of the device according to the invention;[0009]
• FIG. 2 is a side view of the embodiment of the device according to the invention shown in FIG. 1;[0010]
• FIG. 3 is a side view of another embodiment of the device according to the invention;[0011]
• FIG. 4 is a perspective view of an embodiment of the anchoring element;[0012]
• FIGS. 5[0013]ato5gare top views of various embodiments of the anchoring element;
• FIGS. 6[0014]aand6bare side views of various embodiments of the anchoring element;
• FIGS. 7[0015]ato7eare cross-sections of anchoring elements of various embodiments of the anchoring element;
• FIGS. 8[0016]aand8bare perspective views of twisted anchoring segments in various embodiments of the anchoring element;
• FIGS. 9[0017]aand9bare perspective views of anchoring segments consisting of multiple blades in various embodiments of the anchoring element;
• FIG. 10 is a perspective view of an embodiment of a spiral-shaped anchoring element that is equipped with a transport screw;[0018]
• FIG. 11 is a perspective view of another embodiment of a 3-blade anchoring element that is equipped with a transport screw;[0019]
• FIG. 12 is a perspective view of another embodiment of an anchoring element that is equipped with a transport device;[0020]
• FIG. 13 is a perspective view of an implantable anchoring element with a transport device;[0021]
• FIG. 14[0022]ais a perspective view of an embodiment of the anchoring element with a surface structure;
• FIG. 14[0023]bis a perspective view of another embodiment of the anchoring element with a surface structure;
• FIG. 14[0024]cis a perspective view of an embodiment of the anchoring element with transverse-running holes;
• FIG. 15 is a perspective view of an embodiment of an anchoring element that is equipped with a threaded bush;[0025]
• FIGS. 16[0026]aand16bare perspective views of devices for anchoring a transport device for inserting the anchoring element;
• FIGS. 17[0027]aand17bare perspective views of another device for anchoring a transport device for inserting the anchoring element;
• FIG. 18 is a cross-section through a vertebral body with an implanted anchoring element; and[0028]
• FIG. 19 is a view of a cut-out of a spinal column with an implanted device as described by the invention.[0029]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• FIGS. 1 and 2 show an embodiment of the device according to the invention that comprises an[0030]anchoring element3 with receiving means7 for alongitudinal support1 at theback end6 of theanchoring element3. The receiving means7 consists of a receivinghead10 that is essentially circular-cylindrical and is coaxial with alongitudinal axis4 of theanchoring element3, with achannel11 that is open toward theback end6 to receive thelongitudinal support1. In this case, thelongitudinal support1 is received in such a way that itscentral axis2 runs vertical to thelongitudinal axis4. In an area between thefront end5 and the receivinghead10, the anchoringelement3 contains an anchoringsegment27, which is designed as an essentiallyparallelepiped blade9. Viewed vertically with respect to thelongitudinal axis4, theblade9 has a rectangular cross-section with a width B and a thickness D. At thefront end5 of theanchoring element3, the width B of theblade9 converges to apoint14. Moreover, external threading12 that is concentric to thelongitudinal axis4 on the receivinghead10 and anut13 that can be screwed onto this external threading12 are arranged at theback end6 of theanchoring element3 as immobilizing means8 so that when thenut13 is tightened, thelongitudinal support1 is axially clamped in thechannel11, thereby locking theanchoring element3 to thelongitudinal support1.
• The embodiment shown in FIG. 3 of the device according to the invention encompasses an[0031]anchoring element3, which has as an anchoring segment27 a spiral-shapedblade9 that is coaxial to thelongitudinal axis4. At theback end8 of theanchoring element3, coaxial to thelongitudinal axis4, are located acone segment23 that abuts the anchoringsegment27 and, also attached coaxially thereto, a threadedpin25. The receiving means7 consists essentially of a connectingelement36 with a hole in it, wherein thelongitudinal support1 is mounted so as to be able to move coaxially with respect to the central axis2 (FIG. 2) and can be secured in place with astop screw35. Running next to thelongitudinal support1 in connectingelement36 is acavity38 in the shape of a hollow sphere that runs through the connectingelement36, in which a slottedtensioning element37 in the shape of a two-base spherical segment is mounted. Thetensioning element37 is equipped with aninner cone39, in which thecone segment23 can be received in theanchoring element3. Because theanchoring element3 and the connectingelement36 are connected by means of thetensioning element37 that can be rotated in the cavity around three axes that are vertical to one another, the angle between thecentral axis2 of thelongitudinal support1 and thelongitudinal axis4 of theanchoring element3 can be varied. With anut13 that can be screwed onto the threadedpin25 at the end, thecone segment23 is pulled into theinner cone39 of thetensioning element37, thus expanding said segment radially. In thecavity38, clamping is done in such a way that the anchoringelement3 is locked in the connectingelement36. Such a connection between thelongitudinal support1 and a pedicle screw as ananchoring element3 is described in EP 0 599 847. Instead of thecone segment23 and the threadedpin25, at theback end6 of theanchoring element3 there can be a ball head that can be connected to thelongitudinal support1 by means of a device to connect alongitudinal support1 to ananchoring element3 that is designed as a pedicle screw, as disclosed in WO 98/52482.
• FIG. 4 shows an embodiment of the anchoring[0032]segment27 that abuts theback end6 of the anchoring element3.jover a length L. The anchoringsegment27 consists essentially of aflat blade9 that has a length L, a width B, and a thickness D. Length L and thickness D enclose the lateral surfaces32 of the blade. When viewed vertically with respect to thelongitudinal axis4, the cross-section of theblade9 encompasses a firsttransverse axis29, which runs in the plane of the lateral surfaces32 and is vertical with respect to thelongitudinal axis4, and a secondtransverse axis30, which is vertical with respect to the lateral surfaces32 and with respect to thelongitudinal axis4. The ratio of width B to thickness D is basically between 1 and 14 and preferably between 3 and 6. Owing to this ratio of width B to thickness D, the implant can be inserted into a vertebral body without major destruction of the bone. Theblade9 is then aligned in the bone with allowance for the action of load. If theblade9 is implanted in a vertebral body in such a way that the firsttransverse axis29 runs parallel to the longitudinal axis of the spinal column, theblade9 has great resistance to bending stress but is in an unfavorable position with respect to cutting through the bone. If, however, theblade9 is implanted in the vertebral body in such a way that the secondtransverse axis30 runs parallel to the longitudinal axis of the spinal column, theblade9 is placed in a more favorable position as regards cutting through the bone, although this is achieved at the expense of reduced resistance to bending.
• For example, the[0033]blade9 can be designed as follows:
• a) in the shape of a parallelepiped with a length L, a thickness D, and a width B (FIG. 5[0034]a);
• b) in the shape of a wedge with a width B that converges toward the front end[0035]5 (FIG. 5b);
• c) in the shape of a wedge with a width B that diverges toward the front end[0036]5 (FIG. 5c);
• d) viewed from the top, the[0037]blade9 is designed to be convex at the front end5 (FIG. 5d);
• e) viewed from the top, the[0038]blade9 tapers to apoint14 with even or uneven sides (FIG. 5e);
• f) viewed from the top, the[0039]blade9 is beveled on one side at the front end5 (FIG. 5f);
• g) viewed from the top, the[0040]blade9 is rounded on one side at the front end5 (FIG. 5g);
• h) in a longitudinal section running parallel to the lateral surfaces[0041]32, theblade9 tapers to a point at thefront end5 with even or uneven sides (FIG. 6a);
• i) in a longitudinal section running parallel to the lateral surfaces[0042]32, theblade9 is beveled on one side at the front end5 (FIG. 6b);
• j) in a cross-section that is a vertical with respect to the[0043]longitudinal axis4, both of the lateral edges of theblade9 that lie in the lateral surfaces32 taper into a point (FIG. 7a);
• k) in a cross-section that is a vertical with respect to the[0044]longitudinal axis4, a lateral edge of theblade9 that lies in alateral surface32 tapers into a point (FIG. 7b);
• l) in a cross-section that is a vertical with respect to the[0045]longitudinal axis4, a lateral edge of theblade9 that lies in alateral surface32 is beveled (FIG. 7c);
• m) in a cross-section that is a vertical with respect to the[0046]longitudinal axis4, both lateral edges of theblade9 that lie in the lateral surfaces32 are equally beveled (FIG. 7d); and
• n) in a cross-section that is a vertical with respect to the[0047]longitudinal axis4, the two lateral edges of theblade9 that lie in thevertical surfaces32 are beveled in diametrically opposed ways (FIG. 7e).
• FIGS. 8[0048]aand8bshow two embodiments of atwisted blade9. FIG. 8ashows ablade9 that is twisted by an angle of twist a over length L around an edge of theblade9 that encloses length L and abuts one of the lateral surfaces32. FIG. 8bshow theblade9 that is twisted by a angle of twist α over length L around thelongitudinal axis4 as well. The twisting can be left-handed or right-handed. For twisting length Lv and angle of twist α, the lead of the twist can be defined as follows:
• Lead S=Lv°360°/α[′].
• In cases where the[0049]blade9 is designed in shape of this kind of spiral, a lead of between 60 mm and 300 mm and preferably between 100 mm and 240 mm is advantageous.
• FIG. 9[0050]ashows another embodiment of theanchoring element3 with a combination ofblades9. The anchoringelement3 comprises an anchoringsegment27 with twoblades9 that are connected by a hollow28 that is arranged coaxially with regard to thelongitudinal axis4 over the entire length of theanchoring element3. In this case the twoblades9 are arranged in such a way that their firsttransverse axes29 lie in one plane. Ahole20 runs through the hollow28 concentrically with respect to thelongitudinal axis4.
• The embodiment of the[0051]anchoring element3 that is shown in FIG. 9bis another combination ofmultiple blades9 that comprises threeblades9 arranged in the shape of a star. The one lateral surfaces32 (FIG. 4) of the threeblades9 are connected to a coaxialhollow cylinder28 parallel to thelongitudinal axis4, whereby the firsttransverse axes29 of theblades9 enclose the central angles β, γ, δ. In the embodiment depicted here, the central angles is β, γ, δ are equal, i.e., β=γ=δ, while in other embodiments theblades9 can be arranged with different central angles as required by the given situation. Ananchoring element3 that comprises three ormore blades9 can also be designed in the shape of a spiral.
• In the case of intramedullary-pin systems, the blade-shaped anchoring implant is hammered in. Hammering in or near the spinal column is not recommended since there is the danger that vital neurologic and vascular structures may be damaged.[0052]
• Possible ways of inserting the[0053]anchoring element3 in a controlled manner using atransport device15 are depicted in FIGS.10-13. Thetransport device15 shown in FIG. 10 includes atransport screw16 with ascrew tip17, ascrew shaft18, a threadedsegment21 adjacent to thescrew tip17, and a drive means19, whereby the drive means19 can be operated from theback end6 of theanchoring element3. Thetransport screw16 is able to turn freely relative to theanchoring element3. If thetransport screw16 is turned by means of thescrewdriver49, it screws through the bone and pulls the anchoringelement3 along with it.
• As shown in FIGS. 10 and 11, the threaded[0054]segment21 can be integrated into the anchoringsegment27, whereby the threads protrude radially over the thickness D of the blade or protrude over the anchoringsegment27 at thefront end5 of theanchoring element3. Moreover, the threadedsegment21 may protrude over only part of length L or over the entire length L. The advantages of thistransport device15 lie in the fact that thetransport screw16 pulls the anchoringsegment27 directly into the bone. There is the disadvantage, however, that in the middle of the spinal column the bone is very porous, so that thetransport screw16 may pull out and the transport device could fail.
• In FIG. 12 the[0055]transport device15 includes atransport screw16, which is located in thehole20 in the hollow28, protrudes over thefront end5 of theanchoring element3, and can be anchored in the counter corticalis. Instead of being anchored in the counter corticalis by means of threading, as in the case oftransport screw16, other elements such as pegs46 (FIGS. 16aand16b) or hooks47 (FIGS. 17aand17b), etc., with extensions can also be used. At theback end6 of theanchoring element3, thetransport device15 has anextension63 that is connected to thetransport screw16, protrudes coaxially over the anchoringelement3 over length segment A, and has anabutment15 at the end, so that an expandingdevice51 can be inserted between theabutment50 and theback end6 of theanchoring element3 and the anchoringsegment27 can be forced into the bone by opening the expandingdevice51. In this embodiment of thetransport device15 thetransport screw16 is anchored in the bone from the outset. The drawback, however, is the expensive instrumentation required by the limited space in which the work may be performed.
• The U-shaped[0056]auxiliary device48 that is symbolically depicted in FIG. 13 is anchored by means of, e.g., bone screws52 in the cortex layer as an abutment in order to force the anchoringsegment27 at theback end6 of theanchoring element3 into the bone by means of an expandingdevice51. Here additional drilling of the vertebral bodies may be required in order to anchor theauxiliary device48.
• Compared to bone screws as well as hollow screws, in the[0057]blade9 the anchor strength may be relatively low in thelongitudinal axis4. Thetransport devices15 shown in FIGS.10-12 may increase the anchoring strength.
• FIGS. 14[0058]a-14cshow ways, without limitation, in which the design of the surface of theblade9 may be altered to increase anchoring strength in the longitudinal axis4:
• a) A saw-toothed design of the surface of[0059]blade9 that is enclosed by length L and width B (FIG. 14a), whereby the steep sides of the teeth of the saw are directed away from thefront end5 of theanchoring element3; or3
• b) A fish-scale-like design of the surface of[0060]blade9 that is enclosed by length L and width B (FIG. 14b), whereby the sides of the scales, which are steep in this case as well, are directed away from thefront end5 of theanchoring element3.
• In this case, the saw-toothed or fish-scale-like design may be applied to only one of the surfaces enclosed by length L and width B, or it can be applied to both of these surfaces; or it can encompass only a portion of length L, or it can extend over the entire length L.[0061]
• c) Instead of a mechanical lock, it is also possible to use a biological lock. As FIG. 14[0062]cshows, in this casemultiple holes62 run through theblade9 vertically with respect to the surfaces enclosed by length L and width B, so that the bone can grow through theholes62.
• In the embodiment shown in FIG. 15, a threaded[0063]bush40 with external threading41 is located at theback end6 of theanchoring element3. The threadedbush40 includes acoaxial hole42, which can slide over acylindrical pin43 that is arranged between the anchoringsegment27 and thecone end segment23. Like the transport screw18 (FIGS.10-12), this threadedbush40 also helps to increase the anchoring strength of theanchoring element3 in the bone. This embodiment can be used in combination with the versions shown in FIGS.10-14.
• FIGS. 16[0064]aand16bshow devices for anchoring the transport device16 (FIG. 12) in the counter corticalis that can be used instead of a transport screw15 (FIG. 12). This is a hollowcylindrical peg46 that is designed to be elastically radial from itsfirst end56 and itssecond end57 bycoaxial slots56 in the radial direction (FIG. 16a). In the embodiment shown in FIG. 16a, the radial expansion of thepeg48 is accomplished by means of two expandingcones53 that are coaxially arranged on an also-coaxial threadedrod54 and that can be pushed against one another by the external threading on the threaded rod and by corresponding internal threading in the expandingcones53. As FIG. 16bshows, instead of the expanding cones53 awedge element58 can also be used to expand thepeg46 radially. Apeg46 is shown here that has coaxially penetratingslots55 only from thesecond end57, so that the expansion of thepeg46 is accomplished by pulling thewedge element58 inward coaxially by means of the threadedrod54. Instead of being made of 4 parts, as shown in FIG. 16b, thewedge element58 can also be composed of 1, 2, or 3 parts.
• Another device for anchoring the transport device[0065]16 (FIG. 12) in the counter corticalis is shown in FIG. 17aand17b. This is ahook47 that expands radially relative to thelongitudinal axis4 of the anchoring element3 (FIG. 1), tapers toward itstip61, and is forced together radially both before and during installation by a coaxially arrangedbush59. Thehook47 is inserted by means of acoaxial rod60. After thehook47 is inserted,bush59 is pulled off of thehook47 over its end opposite thetip61, whereupon thehook47 elastically expands radially and is thus anchored in the counter corticalis.
• FIG. 18 shows a cross-section through a[0066]vertebral body63 with an insertedanchoring element3 that passes through thevertebral body63 with alongitudinal axis4 that runs transverse to the longitudinal axis of the spinal column.
• FIG. 19 shows a side view of several[0067]vertebral bodies63 with an implanted device according to the invention which, in this embodiment, comprises a telescopinglongitudinal support1 with acentral axis2 that runs parallel to the longitudinal axis of the spinal column and two anchoringelements3.
• In use the present invention may provide a spinal-column fixation device that can be attached to the vertebral bodies by means of spiral-twisted, blade-like anchoring elements and that takes into account the following additional considerations:[0068]
• a) the anchoring implants may be inserted before the longitudinal support is inserted, thus obviating the need for complicated targeting devices and for aligning the anchoring elements specifically with the longitudinal support;[0069]
• b) the longitudinal support may be placed at the end of the anchoring implant;[0070]
• c) connections between the longitudinal support and anchoring implant may be polyaxial, play-free, and angularly stable, and may be locked and unlocked; and[0071]
• d) it should be possible to insert the anchoring elements with a transport device, thereby avoiding the uncontrolled hammering.[0072]
• Depending on the design of the receiving means, the angle between the longitudinal supports of the anchoring elements and the central axis of the longitudinal support may be fixed, may be varied around an axis, or may be adjusted polyaxially. The surface of the blade may also be designed in different ways on a side that is enclosed by length L and width B or on the two sides that are enclosed by length L and width B. For example, without limitation, the surface(s) of the blade may comprise:[0073]
• a) a smooth surface;[0074]
• b) saw-toothed;[0075]
• c) fish-scale-like;[0076]
• d) arrow-like teeth;[0077]
• e) rough surface (for example, etched, plasma-coated, radiated); or[0078]
• f) holes (biological locking by virtue of the bone growing through the holes).[0079]
• In this regard the surface structures may be applied on one side, on both sides, or only partially on the surface of the blade. The different blade designs can be combined with the different surfaces.[0080]
• The anchoring element may be hammered in, or inserted into a vertebral body with the aid of a transport device. Uncontrolled hammering on the spinal column is generally not recommended (there is the risk of damaging neurologic and vascular structures). Suitable transport systems include, without limitation, the following:[0081]
• a) a transport screw is integrated into the blade (at the tip);[0082]
• b) an element (screw, pin, hook, etc. with extension) anchored in the counter-corticalis serves as an abutment so that the blade can be pulled into the bone; or[0083]
• c) a device is anchored in the corticalis in order to force the anchoring element into the bone.[0084]
• Compared to the devices that are anchored to the vertebrae by means of screws, the invention may provide the following properties:[0085]
• 1) Resistance to cutting through the bone may be increased, while at the same time the amount of bone displaced may be reduced:[0086]
• Same load-bearing surface area per unit of length:[0087]
• Implant with 2 bone screws per vertebra with a minor diameter of d=5 mm; Load-bearing surface area per unit of surface area: 2×d×length/length=10 mm2/mm Displacement per unit of length: 2×d2×Pi/4×length/length=39 mm2/mm[0088]
• Implant with blade-shaped anchoring element per vertebra with width B=10 mm, core in the middle with a diameter of d=5 mm, and a blade thickness of D=1.2 mm: Load-bearing surface area per unit of surface area: 2×d×length/length=10 mm2/mm Displacement per unit of length: ((B−d)×H+d2×Pi/4×length/length=25.6 mm2/mm[0089]
• This shows that there is thus a reduction in displacement (excluding the threading) of 34% with the same load-bearing surface area.[0090]
• Same displacement per unit of length (excluding threading):[0091]
• Implant with 2 bone screws per vertebra with a minor diameter of d=5 mm; Displacement per unit of length: 2×d2×Pi/4×length/length=39 mm2/mm Load-bearing surface area per unit of length: 2×d×length/length=10 mm2/mm[0092]
• Implant with blade-shaped anchoring element per vertebra with width B=7 mm, core in the middle with a diameter of d=5 mm, and a blade thickness of D=1.2 mm: Displacement per unit of length: ((B−d)×H+d2×Pi/4×length/length=39 mm2/mm Load-bearing surface area per unit of length: ((39 mm2−d2×Pi/4/H+d)×length/length=21 mm2/mm.[0093]
• This shows that the load-bearing surface area is increased by 110% while displacement remains the same.[0094]
• 2. Devices that are anchored in the vertebral bodies with screws require at least 2 bone screws per vertebra or one bone screw combined with a clasp-like base in order to provide the rotational stability required for fusion. A blade-shaped anchoring element may be anchored in the bone in a rotationally stable manner, therefore providing the rotational stability required for successful fusion of the vertebral bodies being bridged, and thus offers the following advantages:[0095]
• Devices that are connected to the spinal column cranially and caudally by one blade-shaped anchoring element apiece may be inserted higher up the spinal column than the bulky screw-anchored implants;[0096]
• The fact that the number of anchoring elements required per vertebra may be reduced to one may make it faster and simpler to insert implants based on blade-shaped anchoring elements.[0097]
• In one embodiment, the device for fixation of bones may comprise:[0098]
• 1. A) a longitudinal support ([0099]1) with a central axis (2); and B) n anchoring elements (3.i) (2≦i≦n) with the longitudinal axes (4), one front end each (5) and one back end each (6), whereby C) the longitudinal axes (4) of the anchoring elements (3.i) are arranged at an angle of between 65° and 115° relative to the central axis (2) of the longitudinal support (1); and D) at least one of the anchoring elements (3.j) (1≦j≦n) is designed in the shape of a blade, characterized by the fact that: E) at the back end (6) at least the anchoring element (3.j) comprises receiving means (7) for the longitudinal support (1) with stopping means (8;34) for reversibly securing the connection between the longitudinal support (1) and anchoring element (3.j), and the secured connection does not permit any relative movement between the longitudinal support (1) and anchoring element (3.j), as well as taking up forces and moments in all three axial directions of a three-dimensional coordinate system.
• 2. The device according to 1, wherein at least the one anchoring element ([0100]3.j) (1≦j≦n) is designed in the shape of a blade abutting the back end (6) of the anchoring element (3.j).
• 3. The device according to 1 or 2, wherein the stopping means ([0101]8) can be operated from the back end (6) of at least the one anchoring element (3.j).
• 4. The device according to one of 1-3, wherein the receiving means ([0102]7) is open at the side so that the longitudinal support (1) can be inserted into the receiving means (7) transverse to the longitudinal axis (4).
• 5. The device according to one of 1-3, wherein the receiving means ([0103]7) is open from the back end (6) so that the longitudinal support (1) can be inserted into the receiving means (7) parallel to the longitudinal axis (4).
• 6. The device according to one of 1-5, wherein at least one anchoring element ([0104]3.j) comprises a transport device (15) for inserting the anchoring element (3.j) into a bone parallel to the longitudinal axis (4).
• 7. The device according to 6, wherein the transport device ([0105]15) is designed as a transport screw (16).
• 8. The device according to 7, wherein the transport screw ([0106]16) comprises a screw tip (17), a screw shaft (18), a threaded segment (21) that abuts the screw tip (17), and drive means (19), and the drive means (19) can be operated from the back end (6) of the anchoring element (3.j).
• 9. The device according to 8, wherein at least one anchoring element ([0107]3.j) has a through hole (20) coaxially and the transport screw (16) can be accommodated in this hole (20) in such a way that the screw tip (17) and threaded segment (21) protrude axially over the front end (5) of the anchoring element (3.j).
• 10. The device according to 8, wherein at least one anchoring element ([0108]3.j) has a through hole (20) coaxially and the transport screw (16) can be accommodated in this hole (20), whereby the threaded segment (21) is integrated into the anchoring element (3.j) and over a part of its circumference protrudes radially over the anchoring element (3.j) vertical to the longitudinal axis (4).
• 10. The device according to 8, wherein at least one anchoring element ([0109]3.j) has a through hole (20) coaxially and the transport screw (16) can be accommodated in this hole (20), whereby the threaded segment (21) is integrated into the anchoring element (3.j) and over a part of its circumference protrudes radially over the anchoring element (3.j) vertical to the longitudinal axis (4).
• 11. The device according to one of 1-10, wherein the back end ([0110]6) of at least one of the anchoring elements (3.j) has a coaxial cone segment (23).
• 12. The device according to 11, wherein the cone segment ([0111]23) has a concentric threaded hole (24) that is open at the end axially.
• 13. The device according to 11, wherein a concentric pin ([0112]25) with external threading axially abuts the cone segment (23) at the end.
• 14. The device according to one of 1-10, wherein the receiving means ([0113]7) comprise a coaxial ball head (26) that abuts the back end (6) of the anchoring element (3.j) at the end.
• 15. The device according to one of 1-14, wherein the anchoring element ([0114]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade has an essentially rectangular cross-section with a thickness (D) and a width (B) and the blade (9) has a first transverse axis (22) parallel to the long sides of the cross-section.
• 16. The device according to one of 1-14, wherein the anchoring element ([0115]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, converges toward the front end (5).
• 17. The device according to one of 1-14, wherein the anchoring element ([0116]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, diverges toward the front end (5).
• 18. The device according to one of 1-14, wherein the anchoring element ([0117]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, converges to a point (14) at the front end (5).
• 19. The device according to one of 1-14, wherein the anchoring element ([0118]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, slopes down downward on one side at the front end (5).
• 20. The device according to one of 1-14, wherein the anchoring element ([0119]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, is convex at the front end (5).
• 21. The device according to one of 1-20, wherein the anchoring element ([0120]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed in longitudinal section, converges to a tip at the front end (5).
• 22. The device according to one of 1-20, wherein the anchoring element ([0121]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed in longitudinal section, is attached at the front end (5) on one side.
• 23. The device according to one of 1-22, wherein the anchoring element ([0122]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed in cross-section, narrows to a point on at least one lateral surface (32).
• 24. The device according to one of 1-22, wherein the anchoring element ([0123]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed in cross-section, is attached on one side on at least one lateral surface (32).
• 25. The device according to one of 1-24, wherein the anchoring element ([0124]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade is twisted over length (L) around an edge that abuts one lateral surface (32).
• 26. The device according to one of 1-24, wherein the anchoring element ([0125]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade is twisted over length (L) around the longitudinal axis (4).
• 27. The device according to one of 1-26, wherein the anchoring element ([0126]3.j) has an anchoring segment (27) that has two blades (9) and abuts the back end (6) over a length (L).
• 28. The device according to 27, wherein, when viewed in cross-section, the blades ([0127]9) lie in one plane.
• 29. The device according to 27 or 28, wherein, parallel to the longitudinal axis ([0128]4), the blades (9) are separated by a rod.
• 30. The device according to 29, wherein the rod is a hollow ([0129]28) that is drilled parallel to the longitudinal axis (4).
• 31. The device according to one of 1-26, wherein the anchoring element ([0130]3.j) has an anchoring segment (27) that has three or more blades (9) and abuts the back end (6) over a length (L) and the anchoring segment (27) has a star-shaped cross-section.
• 32. The device according to one of 1-26, wherein the anchoring element ([0131]3.j) has an anchoring segment (27) has three or more blades (9) and abuts the back end (6) over a length (L), whereby the blades (9), viewed in the cross-section of the anchoring segment (27), are arranged with unequal central angles.
• 33. The device according to one of 1-32, wherein the anchoring element ([0132]3.j) has a coaxial hollow (28) with a hole (20) that is also coaxial and penetrates the anchoring element (3.j) from the front end (5) to the back end (6).
• 34. The device according to one of 1-26, wherein the anchoring element ([0133]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L) and at least the one blade (9) has a sawtooth surface structure, whereby the steep sides of the saw-teeth are oriented toward the back end (6) of the anchoring element (3.j).
• 35. The device according to 34, wherein the surface structure is attached on one side.[0134]
• 36. The device according to 34, wherein the surface structure is attached on both sides.[0135]
• 37. The device according to one of 1-33, wherein the anchoring element ([0136]3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L) and at least the one blade (9) has a fish-scale-like surface structure, whereby the steep sides of the scales are oriented toward the back end (6) of the anchoring element (3.j).
• 38. The device according to 37, wherein the surface structure is attached on one side.[0137]
• 39. The device according to 37, wherein the surface structure is attached on both sides.[0138]
• 40. The device according to one of 15-30 or 33-39, wherein the anchoring segment ([0139]27), when viewed in cross-section section, has two blades (9) that lie in one plane and that are separated by a hollow (28) coaxially to the longitudinal axis (4), whereby the blades (9) have a thickness (D) of between 0.8 and 2 mm and a width (B) of between 2.5 mm and 4.5 mm and the hollow cylinder (28) has a diameter (d) of between 3 and 7 mm.
• 41. The device according to one of 15-40, wherein the ratio of the width (B) to the thickness (D) is basically between 1 and 14.[0140]
• 42. The device according to 41, wherein the ratio of the width (B) to the thickness (D) is basically between 3 and 6.[0141]
• 43. The device according to one of 15-42, wherein at least one blade ([0142]9) is designed in the shape of a spiral.
• 44. The device according to 43, wherein at least one blade ([0143]9) has a lead S of between 60 and 300 mm.
• 45. The device according to 44, wherein at least one blade ([0144]9) has a lead S of between 100 and 240 mm.
• 46. The device according to one of 43-45, wherein the twisting angle a over length (L) of the blades ([0145]9) is between 0 and 360°.
• 47. The device according to one of 43-45, wherein the twisting angle a over length (L) of the blades ([0146]9) is between 0 and 180°.
• 48. The device according to one of 43-45, wherein the twisting angle a over length (L) of the blades ([0147]9) is between 0 and 45°.
• 49. The device according to one of 43-45, wherein the twisting angle a over length (L) of the blades ([0148]9) is between 45 and 90°.
• 50. The device according to one of 15-49, wherein at least one blade ([0149]9) is twisted in the shape of a spiral and the twist runs clockwise.
• 51. The device according to one of 15-49, wherein at least one blade ([0150]9) is twisted in the shape of a spiral and the twist runs counter-clockwise.
• While various descriptions of the present invention are described above, it should be understood that the various features can be used singly or in any combination thereof. Therefore, this invention is not to be limited to only the specifically preferred embodiments depicted herein. Further, it should be understood that variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is accordingly defined as set forth in the appended claims.[0151]

Claims (21)

What is claimed is:

1. A device for fixation of bones, especially vertebral bodies, relative to one another, comprising:

A) a longitudinal support (1) with a central axis (2); and

B) n anchoring elements (3.i) (2≦i≦n) with the longitudinal axes (4), one front end each (5) and one back end each (6), whereby

C) the longitudinal axes (4) of the anchoring elements (3.i) are arranged at an angle of between 65° and 115° relative to the central axis (2) of the longitudinal support (1); and

D) at least one of the anchoring elements (3.j) (1≦j≦n) is designed in the shape of a blade,

characterized by the fact that:

E) at the back end (6) at least the anchoring element (3.j) comprises receiving means (7) for the longitudinal support (1) with stopping means (8;34) for reversibly securing the connection between the longitudinal support (1) and anchoring element (3.j), and the secured connection does not permit any relative movement between the longitudinal support (1) and anchoring element (3.j), as well as taking up forces and moments in all three axial directions of a three-dimensional coordinate system.

2. The device according toclaim 1, wherein at least the one anchoring element (3.j) (1≦j≦n) is designed in the shape of a blade abutting the back end (6) of the anchoring element (3.j).

3. The device according toclaim 2, wherein the stopping means (8) can be operated from the back end (6) of at least the one anchoring element (3.j).

4. The device according toclaim 3, wherein the receiving means (7) is open at the side so that the longitudinal support (1) can be inserted into the receiving means (7) transverse to the longitudinal axis (4).

5. The device according toclaim 3, wherein the receiving means (7) is open from the back end (6) so that the longitudinal support (1) can be inserted into the receiving means (7) parallel to the longitudinal axis (4).

6. The device according toclaim 5, wherein at least one anchoring element (3.j) comprises a transport device (15) for inserting the anchoring element (3.j) into a bone parallel to the longitudinal axis (4).

7. The device according toclaim 6, wherein the transport device (15) is designed as a transport screw (16).

8. The device according toclaim 7, wherein the transport screw (16) comprises a screw tip (17), a screw shaft (18), a threaded segment (21) that abuts the screw tip (17), and drive means (19), and the drive means (19) can be operated from the back end (6) of the anchoring element (3.j).

9. The device according toclaim 8, wherein at least one anchoring element (3.j) has a through hole (20) coaxially and the transport screw (16) can be accommodated in this hole (20) in such a way that the screw tip (17) and threaded segment (21) protrude axially over the front end (5) of the anchoring element (3.j).

10. The device according toclaim 8, wherein at least one anchoring element (3.j) has a through hole (20) coaxially and the transport screw (16) can be accommodated in this hole (20), whereby the threaded segment (21) is integrated into the anchoring element (3.j) and over a part of its circumference protrudes radially over the anchoring element (3.j) vertical to the longitudinal axis (4).

11. The device according toclaim 10, wherein the back end (6) of at least one of the anchoring elements (3.j) has a coaxial cone segment (23).

12. The device according toclaim 11, wherein the cone segment (23) has a concentric threaded hole (24) that is open at the end axially.

13. The device according toclaim 11, wherein a concentric pin (25) with external threading axially abuts the cone segment (23) at the end.

14. The device according toclaim 10, wherein the receiving means (7) comprise a coaxial ball head (26) that abuts the back end (6) of the anchoring element (3.j) at the end.

15. The device according toclaim 14, wherein the anchoring element (3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade has an essentially rectangular cross-section with a thickness (D) and a width (B) and the blade (9) has a first transverse axis (22) parallel to the long sides of the cross-section.

16. The device according toclaim 14, wherein the anchoring element (3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, converges toward the front end (5).

17. The device according toclaim 14, wherein the anchoring element (3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, diverges toward the front end (5).

18. The device according toclaim 14, wherein the anchoring element (3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, converges to a point (14) at the front end (5).

19. The device according toclaim 14, wherein the anchoring element (3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, slopes down downward on one side at the front end (5).

20. The device according toclaim 14, wherein the anchoring element (3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed from above, is convex at the front end (5).

21. The device according toclaim 20, wherein the anchoring element (3.j) has an anchoring segment (27) that has at least one blade (9) and abuts the back end (6) over a length (L), whereby said blade, when viewed in longitudinal section, converges to a tip at the front end (5).

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