Self-stopping tissue anchors

A system for use with tissue of a subject, the system comprising:

• a driver;
• and
• a tissue anchor, the tissue anchor comprising:
• an anchoring portion configured to be screwed distally into the tissue by being rotated about a longitudinal axis of the anchor;
• and
• a crown, coupled to a proximal portion of the anchoring portion, defining a tissue-facing surface, and comprising:
• an anchor head fixedly coupled to the anchoring portion, such that screwing the anchoring portion into the tissue moves the anchor head distally along the longitudinal axis toward the tissue,
• a driver interface, configured to be engaged by the driver, and
• a socket, fixedly coupled to the driver interface, and shaped to receive the anchor head within the socket, the tissue-facing surface facing distally away from the socket,
• wherein the tissue anchor has:
• a first state in which the anchor head is seated snugly within the socket, such that torque applied by the driver to the driver interface rotates the socket, the anchor head, and the anchoring portion, thereby facilitating screwing of the anchoring portion into the tissue, and
• a second state in which the anchor head is disposed distally from the socket, such that torque applied by the driver to the driver interface rotates the socket relative to the anchor head and the anchoring portion, and
• wherein the tissue anchor is configured to transition from the first state to the second state, responsively to the anchoring portion having been screwed into the tissue sufficiently deep such that the tissue resists further distal movement of the tissue-facing surface while the screwing of the anchoring portion into the tissue pulls the anchor head distally out of the socket.