Receiving part for connecting a shank of a bone anchoring element to a rod and bone anchoring device with such a receiving part

A bone anchoring kit, comprising a bone anchoring element having a shank, a receiving part for connecting the shank of the bone anchoring element to a rod, a securing element having an outer thread, and a tool having a tubular holding portion having a non-circular shape configured to receive the receiving part,

• the receiving part comprising:
• a first end and a second end and a central axis extending from the first end in a direction of the second end,
• a recess having a substantially U-shaped cross section, the recess extending from the first end in a direction of the second end and forming two legs open at the first end and coming together at a bottom of the recess, the recess defining a channel between the legs to receive the rod, the channel having a longitudinal axis,
• the two legs having an inner thread to receive the securing element, the inner thread on each of the two legs extending uninterrupted along substantially the full width of each leg, the outer thread configured to engage and cooperate with the inner thread to permit the securing element to contact and secure the rod,
• wherein the receiving part is polyaxially connectable to the bone anchoring element and the two legs are provided with stiffening structures,
• wherein the stiffening structures comprise a first envelope of the receiving part located above the bottom of the recess along a plane perpendicular to the central axis, the first envelope extending a greater distance from the central axis than every envelope of the receiving part that is parallel to the first envelope and located below the bottom of the recess.

A bone anchoring device comprising a bone anchoring element having a shank, a rod, a receiving part for connecting the shank of the bone anchoring element to the rod, and a securing element having an outer thread,

• the receiving part comprising:
• a first end and a second end and a central axis extending from the first end in a direction of the second end,
• a recess having a substantially U-shaped cross section, the recess extending from the first end in the direction of the second end and forming two legs open at the first end and coming together at a bottom of the recess, the recess defining a channel to receive the rod, the channel having a longitudinal axis,
• the two legs having an inner thread to receive the securing element, the outer thread configured to cooperate with the inner thread to secure the rod,
• wherein the receiving part is polyaxially connectable to the bone anchoring element and the two legs are provided with stiffening structures to reduce splaying caused by a torque acting on the two legs at the time of final tightening of the rod by the securing element,
• wherein along a first plane perpendicular to the central axis and including a longitudinal axis of a rod received in the channel, the receiving part has a first thickness along a first radial direction from the central axis and a second thickness along a second radial direction from the central axis, the first thickness being greater than the second thickness to form the stiffening structures, and
• wherein along a second plane parallel to the first plane and positioned closer to the first end, the receiving part has a third thickness in the first radial direction that is less than the first thickness while maintaining the second thickness in the second radial direction.

A bone anchoring device comprising a bone anchoring element having a shank, a receiving part for connecting the shank of the bone anchoring element to a rod, and a securing element having an outer thread,

• the receiving part comprising:
• a first end and a second end and a central axis extending from the first end in a direction of the second end,
• a recess having a substantially U-shaped cross section, the recess extending from the first end in the direction of the second end and forming two legs open at the first end and coming together at a bottom of the recess, the recess defining a channel to receive the rod, the channel having a longitudinal axis,
• the two legs having an inner thread to receive the securing element, the outer thread configured to cooperate with the inner thread to secure the rod,
• wherein the receiving part is polyaxially connectable to the bone anchoring element and the two legs are provided with stiffening structures to reduce splaying caused by a torque acting on the two legs at the time of final tightening of the rod by the securing element, such that along at least one plane perpendicular to the longitudinal axis of the channel, a cross-section of the receiving part includes a portion above the bottom of the recess having a greatest width in a direction perpendicular to the central axis that is greater than a width of any portion of the cross-section below the bottom of the recess.