Anchors and implant devices

1. Apparatus comprising an implant, the implant comprising:

a rod-shaped housing, having a distal half and a proximal half, and configured to be injected distally into tissue of a subject;

a first electrode, configured to function as a cathode on the distal half of the housing;

an anchor configured to protrude from the proximal half of the housing, no anchor being configured to protrude from the distal half of the housing;

a second electrode, configured to function as an anode, and disposed at a site of the housing that is distal to the anchor and proximal from the cathode; and

circuitry disposed within the housing, configured to configure the first electrode to function as the cathode, to configure the second electrode to function as the anode, and to drive a current between the cathode and the anode,

wherein the anchor comprises a tether that has:

a distal end coupled to the housing, and configured to remain coupled to the housing during and after injection of the housing,

a proximal end, configured to remain outside the subject during and after the injection of the housing, and

a distal portion that comprises the distal end, and is configured to promote tissue growth that adheres the distal portion to the tissue, thereby inhibiting movement of the housing with respect to the tissue.

2. The apparatus according to claim 1 , wherein the anode is disposed on the proximal half of the housing.

3. The apparatus according to claim 1 , wherein the anode has a larger surface area than the cathode.

4. The apparatus according to claim 1 , further comprising an antenna configured to receive wirelessly-transmitted power, wherein the circuitry is configured to use the received power to drive the current between the cathode and the anode.

5. The apparatus according to claim 4 , wherein the antenna is disposed within the housing.

6. The apparatus according to claim 4 , wherein the antenna is disposed between the anode and the cathode.

7. The apparatus according to claim 4 , wherein the antenna is disposed proximal to the anode.

8. The apparatus according to claim 7 , further comprising a delivery tube, wherein:

the implant is configured to be injected distally into the tissue by being disposed, in a delivery state, within the delivery tube with the distal half of the housing disposed closer to a distal opening of the delivery tube than is the proximal half of the housing,

in the delivery state the anchor is in a restrained state thereof, and

the anchor is configured to automatically expand away from the housing upon deployment from the delivery tube.

9. The apparatus according to claim 1 , wherein the tether has a connecting portion that couples the proximal end to the distal portion, and is configured to be disposed within the subject after the injection of the housing, the connecting portion:

having a first state in which the connecting portion is capable of transferring sufficient tension from the proximal end to the distal portion to pull the housing out of the subject, and

being configured to weaken in response to being disposed within the subject, such that, after a duration of being disposed within the subject, tension applied to the proximal end of the tether decouples the proximal end from the distal portion of the tether, the duration being at least 1 day.

10. The apparatus according to claim 9 , wherein the connecting portion is configured to weaken by becoming absorbed by the tissue of the subject.

11. The apparatus according to claim 9 , wherein the distal portion has a coating that is configured to inhibit the promotion of tissue growth for a period of the coating being disposed within the subject, and to decrease inhibiting the promotion of tissue growth after the period, the period being at least 1 day.

12. The apparatus according to claim 11 , wherein the coating and the connecting portion are configured such that the duration is longer than the period.

13. The apparatus according to claim 1 , further comprising a delivery tool that comprises a tube via which the housing is injectable while the distal end of the tether is coupled to the housing.

14. A method, comprising:

injecting, distally into tissue of a subject, a rod-shaped housing of an implant, wherein:

the rod-shaped housing has a distal half and a proximal half,

the implant comprises:

a first electrode, configured to function as a cathode on the distal half of the housing;

an anchor configured to protrude from the proximal half of the housing, no anchor being configured to protrude from the distal half of the housing;

a second electrode, configured to function as an anode, and disposed at a site of the housing that is distal to the anchor and proximal from the cathode; and

circuitry disposed within the housing, configured to configure the first electrode to function as the cathode, to configure the second electrode to function as the anode, and to drive a current between the cathode and the anode,

wherein:

the anchor comprises a tether that has:

a distal end coupled to the housing,

a proximal end, and

a distal portion that comprises the distal end,

injecting the housing comprises:

injecting the housing while (i) the distal end of the tether remains coupled to the housing, and (ii) the proximal end of the tether remains disposed outside of the subject, and

leaving (i) the distal end of the tether coupled to the housing, and (ii) the proximal end of the tether outside of the subject, and

the distal portion of the tether is configured to promote tissue growth that adheres the distal portion to the tissue, thereby inhibiting movement of the housing with respect to the tissue.