Modular osteosynthesis device for vertebrae
An osteosynthesis device for the treatment of the spine is disclosed having a fork head which is U-shaped in a side view, and which fork head, in the proximal direction, has two fork legs with an internal thread and in which a connecting rod can be received, and a grub screw is passed through the internal thread, and the fork head is detachably connected to a bone anchor. The bone anchor is pivotably mounted in the ball seat of the fork head, wherein the fork head in the ball seat area has slots open towards the distal side and thereby at least one deflectable leg is formed.
1. An osteosynthesis device for the treatment of the spine, comprising:
a fork head which is U-shaped in a side view, and which fork head, in a proximal direction, has two fork legs with an internal thread and in which a connecting rod can be received,
a grub screw is passed through the internal thread, and the fork head is detachably connected to a bone anchor, and the bone anchor is pivotably mounted in a ball seat of the fork head,
wherein the fork head in the ball seat area has slots open towards a distal side and thereby at least one deflectable leg is formed, characterized in that the fork head with at least one deflectable leg, which can be applied to the outer surface of a bone anchor head,
wherein the at least one leg has an outer wall and an inner wall, which are interconnected at at least one point in such a way that upon tightening the grub screw, a pressing against one another of the outer wall and the inner wall from the proximal to the distal direction is generated, so that a compressive stress arises in the outer wall and a tensile stress arises in the inner wall, and
wherein between the inner wall and the outer wall, there is a gap which is formed circumferentially,
whereby the at least one deflectable leg is forced against an outer circumference of a spherical head and as a result, the spherical head of the bone anchor clamps in the fork head at a stable angle due to a resulting compressive force.
2. The osteosynthesis device according to claim 1 , wherein the slots extend from radially inside to radially outside, so that the inner wall, outer wall and the connection point have slots.
3. The osteosynthesis device according to claim 1 , wherein the wall thickness of the outer wall is thicker than that of the inner wall.
4. The osteosynthesis device according to claim 1 , wherein the inner wall has at least a smallest wall thickness of 0.3 mm and a maximum wall thickness of 1.5 mm.
5. The osteosynthesis device according to claim 1 , wherein the outer wall and the inner wall of the deflectable leg are integrally connected to one another at least in the area of the distal free end of the deflectable leg.
6. The osteosynthesis device according to claim 1 , wherein the outer wall and inner wall of the deflectable leg are connected to one another by further struts or supports.
7. The osteosynthesis device according to claim 1 , wherein the outer wall of the deflectable leg tapers at least in sections from the proximal to the distal side.
8. The osteosynthesis device according to claim 1 , wherein the inner wall of the deflectable leg tapers at least in sections from the proximal to the distal side.
9. The osteosynthesis device according to claim 1 , wherein the inner wall of the deflectable leg has a radius at the connection point.
10. The osteosynthesis device according to claim 1 , wherein inner walls of deflectable legs coming from the distal side merge above the ball seat and form the proximal area and the fork legs.
11. The osteosynthesis device according to claim 1 , wherein a proximal area of the outer wall fully encloses the fork head and ends below the proximal end of the fork head.
12. The osteosynthesis device according to claim 1 , wherein the at least one deflectable leg is separated by slots, and the slots separate outer wall and inner wall in sections.
13. The osteosynthesis device according to claim 1 , wherein the slots of the outer wall have a different height than the slots of the inner wall.
14. The osteosynthesis device according to claim 1 , wherein the fork legs are connected to one another in a proximal area and contain the internal thread when connected.
15. The osteosynthesis device according to claim 1 , wherein the fork head as a whole is formed integrally.
16. The osteosynthesis device according to claim 1 , wherein the fork head is produced by an additive manufacturing process and consists of a metallic alloy consisting of titanium, cobalt-chromium, or stainless steel alloy.
17. The osteosynthesis device according to claim 1 , wherein the fork head has at least one distally directed edge or projections in an area of the fully enclosing outer wall, and at least one proximally directed edge or projection can be used as a counter bearing to initiate an opposing force acting thereon that generates a pulling against one another of the outer wall and the inner wall, whereby a compressive stress in the inner wall and a tensile stress in the outer wall lead to the at least one leg moving away from the outer surface of the bone anchor head.
18. The osteosynthesis device according to claim 1 , wherein at least one contact point or projection is provided on the outer wall, and at least one retaining feature for the attachment of an instrument is provided on a proximal fork head, and when initiating a pressure force to the contact point an angle-stable clamping of the bone anchor in the fork head is generated without a connecting rod and/or grub screw being present.
19. An osteosynthesis device for the treatment of the spine, comprising
a fork head which is U-shaped in a side view, and which fork head, in a proximal direction, has two fork legs with an internal thread and in which a connecting rod can be received,
a grub screw is passed through the internal thread, and the fork head is detachably connected to a bone ancho, and the bone anchor is pivotably mounted in a ball seat of the fork head,
wherein the fork head in the ball seat area has slots open towards a distal side and thereby at least on deflectable leg is formed, characterized in that the fork head with at least one deflectable leg, which can be applied to the outer surface of a bone anchor head,
wherein the at least on leg has an outer wall and an inner wall, which are interconnected at at least one point in such a way that upon tightening the grub screw, a pressing against one another of the outer wall and the inner wall from the proximal to the distal direction is generated, so that a compressive stress arises in the outer wall and a tensile stress arises in the inner wall,
wherein the at least on deflectable leg is forced against an outer circumference of a spherical head of the bone anchor and as a result, the spherical head clamps in the fork head at a stable angle due to a resulting compressive force,
wherein in an unloaded state the connecting rod rests on at least one outer rod support, the connecting rod being spaced apart from at least one inner rod support, and in a loaded condition with tightened grub screw said spacing is reduced.