Rod connection in a surgical device and rod-shaped bone stabilization device comprising the same
A rod connection for fixing a rod part in a surgical device within a bore of a rod receiving member includes the rod receiving member having a bore having an inner diameter, the rod part having an outer diameter, the rod part being introduced into the bore, wherein the inner diameter of the bore and the outer diameter of the rod part are selected, such that the rod part is press-fitted into the bore of the rod receiving member. The bore has an inner wall surface opposing an outer wall surface of the rod part, the inner wall surface or the outer wall surface being provided with at least one recess in order to reduce a contact surface area between the rod part and the rod receiving member.
1. A bone stabilization device comprising:
a rod having an end portion with an outer radius;
a rigid rod receiving member having a bore with an inner radius smaller than the outer radius, such that a press-fit connection is formed when the end portion of the rod is inserted into the bore of the rod receiving member; and
wherein one of an outer surface of the end portion of the rod and an inner surface of the bore of the rod receiving member has at least one recess while an entire length of the other one of the surfaces that is configured to be press-fit has a constant cross-section, wherein when the recess is on the inner surface of the bore, a radius of the bore at the recess is greater than the outer radius of the end portion of the rod, and when the recess is on the outer surface of the end portion of the rod, a radius of the end portion at the recess is smaller than the inner radius of the bore, to reduce a contact area at the press-fit connection when the end portion of the rod is inserted in the bore of the rod receiving member.
2. The bone stabilization device according to claim 1 , wherein the rod and the rod receiving member each comprises a metal.
3. The bone stabilization device according to claim 2 , wherein at least one of the rod and the rod receiving member comprise Titanium or a Titanium alloy.
4. The bone stabilization device according to claim 2 , wherein the rod receiving member comprises Titanium or a Titanium alloy, and the rod comprises Nitinol.
5. The bone stabilization device according to claim 1 , wherein the at least one recess is provided by a thread formed in the inner surface of the bore or the outer wall surface of the end portion of the rod.
6. The bone stabilization device according to claim 1 , wherein the at least one recess is formed to reduce contact surface area between the rod receiving member and the rod by more than 20% and less than 80% as compared with a form fit connection therebetween.
7. The bone stabilization device according to claim 1 , wherein the at least one recess forms a regular or homogeneously distributed pattern within the bore.
8. The bone stabilization device according to claim 1 , wherein an inner diameter of the bore amounts to 4 mm or less.
9. The bone stabilization device according to claim 1 , wherein an inner diameter of the bore amounts to 3 mm or less.
10. The bone stabilization device according to claim 1 , wherein an inner diameter of the bore amounts to 2 mm or less.
11. The bone stabilization device according to claim 1 , wherein the bore has a longitudinal axis, wherein a length of contact surface between the receiving member and the rod extending in the direction of the longitudinal axis amounts to more than 4 mm.
12. The bone stabilization device according to claim 11 , wherein the length of the contact surface between the rod receiving member and the rod extending in the direction of the longitudinal axis amounts to more than 6 mm.
13. The bone stabilization device according to claim 1 , further comprising a bone anchoring device comprising a bone anchoring element and a receiving part connected to the bone anchoring element, wherein the rigid rod receiving member is configured to connect to the receiving part.
14. A rod-shaped bone stabilization device for connecting two or more bone anchoring elements, the rod shaped bone stabilization device comprising:
a first section and a second section each being connectable to one of said hone anchoring elements, the first section having a bore with an inner radius;
a flexible section extending between the first section and the second section and providing elasticity in an axial direction;
a rod having a first end portion with an outer radius greater than the inner radius of the bore and a second end portion, such that a press-fit connection is formed when the first end portion of the rod is inserted into the bore of the first section;
wherein one of an outer surface of the first end portion of the rod and an inner surface of the bore of the first section has at least one recess while an entire length of the other one of the surfaces that is configured to be press-fit has a constant cross-section, wherein when the recess is on the inner surface of the bore, a radius of the bore at the recess is greater than the outer radius of the first end portion of the rod, and when the recess is on the outer surface of the first end portion of the rod, a radius of the first end portion at the recess is smaller than the inner radius of the bore, to reduce a contact area at the press-fit connection when the first end portion of the rod is inserted in the bore of the first section; and
wherein the rod extends through the flexible section towards the second section, in which the second end portion of the rod is slidably supported such as to provide bending elasticity.
15. The rod shaped bone stabilization device according to claim 14 , wherein the second section comprises a sliding support member for slidingly guiding the second end portion of the rod.
16. A method of attaching a bone stabilization device to a bone, the bone stabilization device comprising a rod having an end portion with an outer radius, a rigid rod receiving member having a bore with an inner radius smaller than the outer radius, such that a press-fit connection is formed when the end portion of the rod is inserted into the bore of the rod receiving member, and wherein one of an outer surface of the end portion of the rod and an inner surface of the bore of the rod receiving member has at least one recess while an entire length of the other one of the surfaces that is configured to be press-fit has a constant cross-section, wherein when the recess is on the inner surface of the bore, a radius of the bore at the recess is greater than the outer radius of the end portion of the rod, and when the recess is on the outer surface of the end portion of the rod, a radius of the end portion at the recess is smaller than the inner radius of the bore, to reduce a contact area at the press-fit connection when the end portion of the rod is inserted in the bore of the rod receiving member, the method comprising:
aligning the end portion of the rod with the bore of the rod receiving member; and
inserting the end portion of the rod into the bore of the rod receiving member to form the press fit connection.
17. The method according to claim 16 , further comprising attaching a bone anchoring element to a bone, wherein the rod receiving member is connected to the bone anchoring element.
18. A bone stabilization device comprising:
a rod having an end portion with an outer radius;
a rigid rod receiving member having a bore with an inner radius smaller than the outer radius, such that a press-fit connection is formed when the end portion of the rod is inserted into the bore of the rod receiving member; and
wherein at least one of an outer surface of the end portion of the rod and an inner surface of the bore of the rod receiving member has at least one recess, wherein when the recess is on the inner surface of the bore, a radius of the bore at the recess is greater than the outer radius of the end portion of the rod, and when the recess is on the outer surface of the end portion of the rod, a radius of the end portion at the recess is smaller than the inner radius of the bore, to reduce a contact surface area at the press-fit connection when the end portion of the rod is inserted in the bore of the rod receiving member; and
wherein the at least one recess is formed to reduce the contact surface area between the rod receiving member and the rod by more than 20% and less than 80% as compared with a form fit connection therebetween.
19. A bone stabilization device comprising:
a rod having an end portion with an outer radius;
a rigid rod receiving member having a bore with an inner radius smaller than the outer radius, such that a press-fit connection is formed when the end portion of the rod is inserted into the bore of the rod receiving member; and
wherein at least one of an outer surface of the end portion of the rod and an inner surface of the bore of the rod receiving member has at least one recess, wherein when the recess is on the inner surface of the bore, a radius of the bore at the recess is greater than the outer radius of the end portion of the rod, and when the recess is on the outer surface of the end portion of the rod, a radius of the end portion at the recess is smaller than the inner radius of the bore, to reduce a contact area at the press-fit connection when the end portion of the rod is inserted in the bore of the rod receiving member; and
wherein the bore has a longitudinal axis, wherein a length of a contact surface between the receiving member and the rod extending in the direction of the longitudinal axis amounts to more than 4 mm.
20. The bone stabilization device according to claim 19 , wherein the length of the contact surface between the rod receiving member and the rod extending in the direction of the longitudinal axis amounts to more than 6 mm.