Artificial muscle for reanimation of the paralyzed face: Durability and biocompatibility in a gerbil model

Background: Current management of permanent facial paralysis centersonnervegraftingandmuscletransfer;however, limitations of those procedures call for other options. Objectives: To determine the durability and biocompatibility of implanted artificial muscle in a gerbil model and the degree of inflammation and fibrosis at the host tissue-artificial muscle interface. Methods: Electroactive polymer artificial muscle(EPAM) devicesengineeredinmedical-gradesiliconewereimplanted subcutaneously in 13 gerbils. The implanted units were stimulated with 1 kVat 1 Hz, 24 h/d via a function generator. Electrical signal input/output was recorded up to 40 days after implantation. The animals were euthanized between23and65days after implantation,andthehosttissue- implant interface was evaluated histologically. Results: The animals tolerated implantation of the EPAM devices well, with no perioperative deaths. The muscle devices created motion for a mean of 30.3 days (range, 19-40 days), with a mean of 2.6×10⁶ cycles (range, 1.6×10⁶ to 3.5×10⁶ cycles). Histologic examination of the explanted devices revealed the development of a minimal fibrous capsule surrounding the implants, with no evidence of bacterial infection or inflammatory infiltrate. No evidence of device compromise, corrosion, or silicone breakdown was noted. Conclusions: Artificial muscle implanted in this shortterm animal model was safe and functional in this preliminary study. We believe that EPAM devices will be a safe and viable option for restoration of facial motions in patients with irreversible facial paralysis.