Implantable sphincter assistance device with redirected or focused magnetic fields for interaction between adjacent beads

An apparatus includes at least one link and a plurality of beads. The plurality of beads is joined using the at least one link and is configured to be arranged in an annular arrangement. The annular arrangement is sized and configured to form a loop around an anatomical structure in a patient. The annular arrangement is configured to move between a contracted configuration and an expanded configuration. The loop in the contracted configuration is configured to prevent fluid flow through the anatomical structure. Each bead includes a housing, a magnet contained within the housing, and a secondary element that is different from the magnet. The magnet is configured to emit a magnetic field. The magnets of the plurality of beads are configured to magnetically bias the loop toward the contracted configuration. The secondary element is contained within the housing and is configured to increase the magnetic field of the magnet.