Implantable sphincter assistance device with dual zone controlled rate of constriction force

An apparatus comprising:

• (a) a plurality of beads, wherein each bead of the plurality of beads comprises:
• (i) at least one housing,
• (ii) at least one magnet positioned within the at least one housing, and
• (iii) at least one resilient member positioned within the at least one housing;
• and
• (b) a plurality of interconnection elements, wherein each interconnection element of the plurality of interconnection elements movably joins together a corresponding pair of beads of the plurality of beads, wherein the plurality of beads and the plurality of interconnection elements are sized and configured to form an expandable loop around an anatomical structure in a patient,
• wherein the plurality of beads is configured to apply at least one constrictive force, wherein the at least one constrictive force includes at least one of:
• (i) a first constrictive force generated via the at least one magnet of each bead of the plurality of beads;
• or
• (ii) a second constrictive force generated via the at least one resilient member of each bead of the plurality of beads;
• wherein the at least one resilient member is configured to engage a respective interconnection element to thereby apply the second constrictive force of the at least one constrictive force;
• wherein the expandable loop is configured to apply the at least one constrictive force to the anatomical structure, wherein the at least one constrictive force has a first rate of change when a dilation ratio of the expandable loop is within a first range, a second rate of change when the dilation ratio of the expandable loop is within a second range, and a third rate of change when the dilation ratio of the expandable loop is within a third range, and wherein the dilation ratio is a ratio of a current size of the expandable loop relative to a maximum size of the expandable loop;
• wherein the first range of the dilation ratio is between approximately 0% and approximately 25%, the second range of the dilation ratio is between approximately 25% and approximately 75%, and the third range of the dilation ratio is between approximately 75% and approximately 100%;
• and
• wherein the first constrictive force is greater when the dilation ratio is within the first and second ranges than within the third range.