Bone anchor
AssigneeBiedermann Technologies GmbH & Co. KG
InventorsTimo Biedermann, Berthold Dannecker
Life of this patent
Estimating the term…
Abstract
A bone anchor includes a shank for anchoring to a bone and a receiving part for coupling a rod to the shank. The receiving part includes a base and two legs each including a first portion extending away from the base, and a second portion extending from the first portion further away from the base, and an elongate extension member extending from the second portion still further away from the base. An internal engagement structure is provided on the first and second portions for engaging a fixation device. A breakaway portion facilitates breaking away of the second portion. The extension members are at least as long as the second portions. The second portions are stiffer than a region of the extension members adjacent the second portions.
Claims24
A bone anchor comprising:
- a shank for anchoring to a bone or a vertebra;
- and
- a receiving part for receiving a rod for coupling the rod to the shank, the receiving part having a central axis and comprising a base and two free legs extending upwardly from the base to define a recess for inserting the rod;
- wherein each of the legs comprises a first portion extending away from the base, and a second portion connected to an end of the first portion opposite the base and extending from the first portion farther away from the base, wherein a first downwardly facing engagement surface is provided on at least part of the first portion and a second downwardly facing engagement surface is provided on at least part of the second portion, wherein the first and second downwardly facing engagement surfaces are positioned at a same radial distance away from the central axis such that both are configured to engage and restrict movement of a fixation device away from the base of the receiving part to secure the rod in the recess, wherein a breakaway portion having a reduced wall thickness or width is provided between the first portion and the second portion to facilitate breaking away of the second portion from the first portion;
- and
- wherein each of the legs further comprises an elongate extension member connected to an end of the second portion opposite the first portion and extending from the second portion farther away from the base, wherein the extension members are at least as long axially as the second portions, and wherein when the extension members are unflexed, a greatest width between outer surfaces of the extension members is smaller than a greatest width between outer surfaces of the second portions of the legs while a distance from the central axis to an inner surface of the extension members is greater than a distance from the central axis to an inner surface of the second portions of the legs excluding the second downwardly facing engagement surface, such that a wall thickness of each of the second portions of the legs is greater than a wall thickness of each of the extension members to make the second portions of the legs stiffer than the extension members.
A method of connecting a rod to a bone or a vertebra via a bone anchor comprising a shank, a receiving part, and a fixation device, the receiving part having a central axis and comprising a base and two free legs extending from the base to define a recess for inserting the rod, wherein each of the legs comprises a first portion extending upwardly away from the base, and a second portion connected to an end of the first portion opposite the base and extending from the first portion farther away from the base, wherein a first downwardly facing engagement surface is provided on at least part of the first portion and a second downwardly facing engagement surface is provided on at least part of the second portion, wherein the first and second downwardly facing engagement surfaces are positioned at a same radial distance away from the central axis such that both are configured to engage and restrict movement of the fixation device away from the base of the receiving part to secure the rod in the recess, wherein a breakaway portion having a reduced wall thickness or width is provided between the first portion and the second portion to facilitate breaking away of the second portion from the first portion, wherein each of the legs further comprises an elongate extension member connected to an end of the second portion opposite the first portion and extending from the second portion farther away from the base, wherein the extension members are at least as long axially as the second portions, and wherein when the extension members are unflexed, a greatest width between outer surfaces of the extension members is smaller than a greatest width between outer surfaces of the second portions of the legs while a distance from the central axis to an inner surface of the extension members is greater than a distance from the central axis to an inner surface of the second portions of the legs excluding the second downwardly facing engagement surface, such that a wall thickness of each of the second portions of the legs is greater than a wall thickness of each of the extension members to make the second portions of the legs stiffer than the extension members, the method comprising:
- anchoring the shank to the bone or the vertebra;
- inserting the rod into the recess;
- engaging the fixation device with the first downwardly facing engagement surface on the legs to secure the rod in the recess;
- and
- breaking the breakaway portions to separate the second portions of the legs and the extension members from the first portions of the legs.
Dependencies are inferred from the claim text.