Bone anchor

A bone anchor comprising a shank configured to be anchored in bone, the shank having a first end configured to be inserted first into the bone, an opposite second end, and a longitudinal axis extending through the first end and the second end, the shank comprising:

• a core;
• a thread configured to engage the bone, wherein the thread extends in a helix around the core and comprises a lower flank directed towards the first end, an upper flank directed towards the second end, and a crest between the lower and upper flanks;
• and
• an additional thread structure comprising a cavity formed in the crest that extends together with part of the thread in the helix around the core, wherein the cavity extends radially from the crest to a radial position that corresponds substantially to the core, and wherein part of the crest remains axially between the cavity and the upper flank and/or between the cavity and the lower flank.

A bone anchor comprising a shank configured to be anchored in bone, the shank having a first end configured to be inserted first into the bone, an opposite second end, and a longitudinal axis extending through the first end and the second end, the shank comprising:

• a core;
• a thread configured to engage the bone, wherein the thread extends in a helix around the core and comprises a lower flank directed towards the first end and an upper flank directed towards the second end;
• and
• an additional thread structure comprising a cavity formed into the core that extends together with part of the thread in the helix around other portions of the core, wherein the cavity radially separates at least a portion of the thread from the other portions of the core.