Comparison of Soft Tissue Response in Rabbits following Laryngeal Implantation with Hydroxylapatite,Silicone Rubber,and Teflon

This study evaluates the soft tissue response in rabbits following laryngeal implantation for medialization using hydroxylapatite prostheses, carved silicone rubber prostheses, and injectable Teflon. Sixteen rabbits underwent left recurrent laryngeal nerve section for denervation and laryngeal implantation with hydroxylapatite. At 1, 3, 6, and 12 months, 4 animals were painlessly sacrificed and processed for histology. Similarly, animals were implanted with carved silicone rubber prostheses or with Teflon injected through a flap in the thyroid lamina for comparison at 1,3, and 6 months. In animals implanted with hydroxylapatite, histologic findings include limited acute inflammatory response, thin fibrous encapsulation, and osteogenesis in the region of the fenestra, with lamellar bone bridging the space between the implant and thyroid lamina. With silicone rubber prostheses, there is a limited inflammatory response and fibrous encapsulation of the implant without evidence of osteogenesis. Animals implanted with Teflon demonstrated a classic foreign body reaction with multinucleated giant cells, granuloma formation, and migration of Teflon into surrounding muscle. With respect to soft tissue response, both hydroxylapatite and silicone rubber are less reactive than Teflon. The osteogenesis observed in the presence of hydroxylapatite increases implant stability and minimizes the risk of migration. Conversely, the presence of bone growth may limit the reversibility of medialization procedures performed with hydroxylapatite.