Behavior of various orbital implants under axial compression.
PURPOSE: To determine and compare the amount of force required to disrupt the integrity of various orbital implants. METHODS: Compression tests were carried out by using a servo-electrical universal testing system on orbital implants including aluminum oxide (Bioceramic implant, FCI, Issy-Les-Moulineaux, France), coralline hydroxyapatite (HA) (Bio-Eye, Integrated Orbital Implants, Inc., San Diego, CA, U.S.A.), bovine HA (Molteno M-Sphere, IOP Inc., Costa Mesa, CA, U.S.A.), synthetic HA (FCI3, FCI, Issy-Les-Moulineaux, France), Chinese HA (H + Y Comprehensive technologies, Philadelphia, PA, U.S.A.), polylactic acid (Kinsey Nash Corporation, Duluth, MN, U.S.A.), porous polyethylene (Medpor, Porex Surgical Inc., College Park, GA, U.S.A.), and polymethylmethacrylate. RESULTS: Two basic groups of implants were identified: those that eventually reach a critical compression point and collapse (coralline HA, aluminum oxide, synthetic FCI3 HA, bovine HA, Chinese HA, and polymethylmethacrylate), and those that do not collapse but gradually compress with increasing load (porous polyethylene, polylactic acid). For similar-sized implants, the critical collapse point was earliest for the FCI3 HA implant, followed by the coralline HA, aluminum oxide, and polymethylmethacrylate implants. Smaller-sized collapsible implants showed earlier critical collapse points than larger-sized implants of similar material. CONCLUSIONS: A technique was established to assess the force required to disrupt the integrity of various orbital implants that is reliable, unbiased, and repeatable with any orbital implant. Orbital implants of different materials and sizes demonstrate different degrees of integrity. It is important to use similar-sized implants when comparing the integrity of different implant materials because size influences the force required to overcome the structural integrity of the implant.