Anchoring element
An anchoring element with a screw (12) comprising a threaded section (13) and a head (15) designed as a spherical segment-shaped section, and with a receiving portion (1) for connecting the screw (12) to a rod (19), is provided. The receiving portion (1) comprises a first end (2) and a second end (3) opposite the latter and a longitudinal axis (4) passing through the two ends (2, 3). The receiving portion further comprises a bore (5) coaxial with the longitudinal axis (4), a first region adjoining the first end (2) with an essentially U-shaped cross-section (18) with two free arms (8, 9) comprising a thread for receiving the rod (19) to be inserted, a region adjoining the other end (3) for receiving the head (15), and an element which exerts pressure on the rod (19) or on the head (15). In order that the screws can be used in situ for very different lengths, the threaded section (13) and the head (15) are designed as separate parts.
The invention concerns an anchoring element with a screw comprising a threaded section and a head designed as a spherical segment-shaped section, and with a receiving portion for connecting the screw to a rod, according to the introductory part of patent claim 1. An anchoring element of this kind is used in particular in vertebral column surgery, but also in accident surgery on other bones.
Such an anchoring element is known from DE 43 07 576 C1, for example. With known anchoring elements and screws of this kind, the threaded section of the screw and its head are constructed in one piece. As the surgeon needs very different lengths of screws, he must always have different sets of such screws available. This makes a considerable stockpile necessary, resulting in considerable costs.
It is the object of the invention to eliminate this drawback.
This object is achieved by the anchoring element characterised in patent claim 1. As a result it is possible for the surgeon during application to shorten the threaded section to a desired length before or after implanting, and then connect it to the head and the receiving portion. In this way the maintenance of stocks is substantially reduced, and at the same time the possibilities for the surgeon to make finer adjustments are increased, as the screws can be shortened to any length.
Developments of the invention are characterised in the subsidiary claims.
Further characteristics and suitabilities of the invention are apparent from the description of practical examples with the aid or the figures.
The figures show:
In the first embodiment shown in
The receiving portion 1 comprises, starting from the first end 2, a U-shaped recess 7 extending perpendicularly to the longitudinal axis 3, with two free arms 8, 9 ending towards the first end 2. Adjoining the first end 2, the arms comprise an internal thread 10. The bottom of the U-shaped recess extends as far as a predetermined distance from the second end 3. Adjoining the first end 2, the arms 8, 9 comprise on the outside a section 11 whose outside diameter is smaller than the outside diameter of the adjoining section of the receiving portion.
The screw 12 cooperating with the receiving portion 1 comprises a threaded section 13 designed as a bone screw and a spherical segment-shaped head 15 which is connected thereto in the assembled view shown in
There is further provided a pressure element 17 which is of cylindrical construction and has an outside diameter which is so large that the pressure element can be introduced into the first bore 5 and moved to and fro in the axial direction in the latter. On its lower side facing towards the second end 3 the pressure element 17 comprises a hollow spherical segment-shaped section which is constructed symmetrically to the longitudinal axis 4 and whose radius corresponds to the radius of the head 5. The pressure element comprises a U-shaped recess 18 which extends transversely to the longitudinal axis 4 and whose free arms extend towards the first end 2. The lateral diameter of this U-shaped recess is selected so that a rod 19 to be received can be inserted in the recess and guided laterally in the latter. The depth of the hollow spherical segment-shaped recess is selected so that it ends at a distance from the second end 3 which is greater than the distance from the centre 16 corresponding to the radius of the head 15, looking towards the first end 2. At the bottom of the U-shaped recess 18 is an adjoining coaxial bore 20 whose diameter is smaller than the diameter of the rod 19 to be received.
As can be seen from
On the side facing towards the first end 2, the pressure element 17 is adjoined by a nut 22 which comprises an external thread 23 mating with the internal thread 10 and in addition an internal thread 24. The inside dimensions of the nut 22 are selected so that the inside width is smaller than the diameter of the section 21 and larger than the diameter of the rod 19 and hence of the U-shaped recess 10. Further, an internal nut 25 with an external thread mating with the internal thread 24 is provided. Finally, there is provided a bush 26 which encompasses the free end adjoining the first end 2 and which in the assembled state sits on the annular section 11, as shown in
As can best be seen from
As can best be seen from
In operation, first the screw 12 is screwed into the bone or vertebra. For this purpose the shank 14 has known engagement possibilities such as a hexagon socket. Then the surgeon shortens the shank 14 to the desired length and first places the receiving portion with the second bore on the shank 14 and then guides the head from the first end 2 onto the shank 14, so that the shank 14 is introduced into the bore 27 from the spring-yielding edge 30 and the head surrounds the shank in the manner shown in
Due to the pressure on the head 15 exerted as seen from the first end 2, the slotted head 15 is on the one hand connected or clamped to the shank 14, preventing movement, and at the same time the head is locked in its rotational position.
The second embodiment shown in
The shank 14 of the screw preferably has the cylindrical shape shown in
The further embodiment shown in
Operation takes place in the same manner as in the practical example described first, wherein after shortening of the shank 35 the head 15 is introduced into the bore 5 from the first end 2 of the receiving portion 1 and screwed onto the shank 35 introduced from the second end 3.
The further embodiment shown in
Operation takes place in a similar manner to the practical example according to
In the practical examples described above, the head 15 is in each case held by an edge designed in one piece with the receiving portion 1. Such an abutment can also be formed in another way: for example, it is possible to drill the first bore 5 completely through the receiving portion 1 and then, adjoining the second end, to mount in it a holding element which receives the head 15.
In the practical examples described above, the receiving portion always comprises the nut 22 and an internal nut 25 as well as a bush 26. This fixing can also be designed differently in a known manner. In particular, if occasion arises only an internal nut can be provided.
In the practical example described above with reference to
In a further embodiment, notches 28 can be provided additionally in the manner shown in
Claims
1. Anchoring element with a screw (12) comprising a threaded section (13) and a head (15) designed as a spherical segment-shaped section, and with a receiving portion (1) for connecting the screw (12) to a rod (19), wherein the receiving portion (1) comprises a first end (2) and a second end (3) opposite the latter, a longitudinal axis (4) passing through the two ends (2, 3), a bore (5) coaxial with the longitudinal axis (4), a first region adjoining the first end (2) with an essentially U-shaped cross-section (7) with two free arms (8, 9) comprising a thread for receiving the rod (19) to be inserted, a region adjoining the other end (3) for receiving the head (15), and an element (22, 17) which exerts pressure on the rod (19) or on the head (15), characterised in that the threaded section (13) and the head (15) are designed as separate parts.
2. Anchoring element according to claim 1, characterised in that the threaded section (13) comprises a shank (14) at the head end.
3. Anchoring element according to claim 1 or 2, characterised in that the head (15) comprises a spring-yielding edge on its side facing towards the threaded section (13).
4. Anchoring element according to any of claims 1 to 3, characterised in that the edge (34) facing towards the threaded action comprises one or more apertures or recesses (28, 29, 33) which are directed parallel to the axis of symmetry (4) and distributed circumferentially.
5. Anchoring element according to claim 4, characterised in that an aperture (33) extends over the whole wall length, seen in a direction parallel to the axis of symmetry (4).
6. Anchoring element according to any of claims 1 to 5, characterised in that the head (15) comprises a bore (27) coaxial with the axis of symmetry.
7. Anchoring element according to claim 6, characterised in that the bore (27) is cylindrical.
8. Anchoring element according to any of claims 2 to 7, characterised in that the shank (14) comprises a rough surface.
9. Anchoring element according to any of claims 2 to 8, characterised in that the shank (14) is polygonal.
10. Anchoring element according to any of claims 1 to 6, characterised in that the head (15) comprises an internal thread in the bore and the shank (35) comprises an external thread mating therewith.
11. Anchoring element according to any of claims 1 to 6, characterised in that the head (15) is corrugated in the circumferential direction in the bore and the shank (37) comprises a corresponding corrugation on its outer side.
Type: Application
Filed: Dec 27, 2004
Publication Date: Aug 4, 2005
Inventors: Lutz Biedermann (Vs-Villingen), Jurgen Harms (Karlsruhe)
Application Number: 11/023,114