Element with a shank and a holding element connected to it for connecting to a rod

  • US 9,895,173 B2
  • Filed: 04/08/2016
  • Issued: 02/20/2018
  • Est. Priority Date: 11/27/2001
  • Status: Active Grant
First Claim
Patent Images

1. A polyaxial bone anchor comprising:

  • an anchor element having a shank and a head, the head having a spherically shaped segment;

    a receiving part having a recess in a top end having a U-shaped cross-section forming two legs for receiving a rod therebetween, the receiving part comprising an inner thread on each of the two legs;

    a locking element to lock the rod in the recess of the receiving part, wherein the locking element has a central axis, a first end with a flat annular surface that extends radially relative to the central axis in a first plane to engage the rod when the locking element is threaded to the receiving part, and a second end with a flat annular surface that extends radially relative to the central axis in a second plane that is parallel to the first plane; and

    a pressure element that cooperates with the head to fix an angular position of the anchor element relative to the receiving part when the locking element is tightened;

    wherein the receiving part and the head of the anchor element are configured to form a polyaxial connection that permits the spherically shaped segment of the head to swivel in the receiving part when unlocked and wherein tightening of the locking element fixes the angular position of the anchor element relative to the receiving part;

    wherein the locking element comprises an outer thread having two flanks, the outer thread cooperates with, the inner thread of the two legs, an upper flank of the two flanks of the outer thread facing the top end of the receiving part and a lower flank of the two flanks of the outer thread facing away from the top end of the receiving part when the locking element is assembled to the receiving part;

    wherein in a cross-section of the outer thread of the locking element, the upper and lower flanks of the outer thread are symmetrical and each flank encloses an angle of 90 degrees with the central axis of the locking element;

    wherein the inner thread on each of the two legs comprises two flanks, an upper flank facing the top end of the receiving part and a lower flank facing away from the top end of the receiving part; and

    wherein a cross-section of the outer thread of the locking element is substantially rectangular and when assembled the lower flank of the inner thread matches a shape of the upper flank of the outer thread such that locking the rod between the legs with the locking element avoids splaying of the legs.

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