Copyright @ 200 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited. 7 Biocompatibility of Polylactides in the Middle Ear: An Experimental Animal Study *Lauri I. Peltonen, *Jussi Jero, †Antti Sukura, *Laura Pietola, ‡§kYrjo¨ T. Konttinen, and *Antti A. Aarnisalo *Department of Otorhinolaryngology, Helsinki University Central Hospital; ÞDepartment of Basic Veterinary Sciences, Faculty of Veterinary Medicine; þDepartment of Internal Medicine, Helsinki University Central Hospital, University of Helsinki; §ORTON Orthopedic Hospital of the Invalid Foundation, Helsinki; and k COXA Hospital for Joint Replacement, Tampere, Finland Objective: To study the suitability of resorbable polylactides for reconstruction in middle ear surgery. Experimental Animals: Twenty-four chinchillas. Interventions: Twenty chinchillas were operated on using 2 types of polylactides inserted into the middle ear and outer ear canal, 10 animals in each group. At 6 months, the animals were killed, and their temporal bones were removed for sectioning. Degree of inflammation, fibrosis, degradation of polylactide material, and new bone formation were assessed histologically. Main Outcome Measures: Polylactide implants caused only a mild local inflammation, with no difference between the 2 materials tested. Conclusion: Polylactide acidYbased middle ear implants were successfully used in the reconstructive middle ear surgery. Resorption occurred without complications. Key Words: BiocompatibilityVBioresorbable implantsVChinchillaV Middle earVPolylactide. Otol Neurotol 28:850Y853, 2007. Polylactides are widely used as implant materials in orthopedic, craniomaxillofacial, and urologic operations (1Y3). Thus far, no reports exist on the use of polylac- tides in human middle ear surgery. However, polylactide in a tympanostomy tube application in an animal model has been found to be biocompatible (4). We have pre- viously shown that bacterial adherence in vitro to poly- lactide materials is no greater than 2 other commonly used implant materials, silicone and titanium (5). In this study, we have tested the surgical usefulness and bio- compatibility of polylactides in experimental middle ear surgery. Two polylactide-based implants with different biomechanical and structural properties were evaluated in this novel application. MATERIALS AND METHODS Polylactides Polylactide A plates (L82/G18 polylactic-glycolic acid; Lactosorb, W. Lorenz Surgical, Inc., Jacksonville, FL, USA) were bent into an L-shaped form or straight cut. Polylactide B plates (L80/G20 polylactic-glycolic acid; Bionx, Ltd., Tampere, Finland) were structurally more fragile, and because of this, they were only straight cut. Experimental Animals and Surgical Procedure Twenty-four male chinchillas were purchased from an animal farm (Helsinki, Finland). The animals were housed in the experimental animal unit of the Faculty of Veterinary Medicine (University of Helsinki, Finland). The study was approved by the Provincial State Office of Southern Finland. Animal experi- ments were conducted in accordance with European Convention (1986) guidelines. Animals were divided into 4 groups (10 animals for both polylactide groupsV2 animals were sham-operated, whereas 2 were not operated). They were anesthetized with ketamine (40 mg/kg, i.p.) and xylazine (4 mg/kg, i.p.). Both ears of all animals were photographed through an otoendoscope before and after surgery. The right ear of each animal (except in the 2 control cases) was operated on, where- as the left ear served as a control. A transcanal approach was used, and a tympanomeatal flap was elevated under micro- scopic control. A polylactide plate (A or B) was inserted under the annulus such that the plate was partly under the tympano- meatal flap and partly in the tympanum under the mucosa by eight animals in both groups. Two animals in both groups were implanted such that the whole straight-cut polylactide plate was placed into the tympanum under the mucosa. In the Address correspondence and reprint requests to Antti A. Aarnisalo, M.D., Dept. of Otorhinolaryngology, Helsinki University Central Hospital, P.O. Box 220, 00029 HUS, Helsinki, Finland; E-mail: antti.aarnisalo@hus.fi This study was supported by the Instrumentarium Foundation and by a special governmental subsidy for health sciences research. Otology & Neurotology 28:850Y853 * 2007, Otology & Neurotology, Inc. 850