An animal model of lower eyelid spacer grafting with acellular dermis.

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Lower eyelid retraction is common in patients with dysthyroid orbitopathy and is seen less commonly in other conditions. Treatment typically requires vertical augmentation of the posterior eyelid lamella with an interpositional graft. Several autologous, homologous, and alloplastic materials have been used. We investigated the gross and microscopic in vivo histology of acellular homologous dermis used as a structural interpositional graft in the lower eyelids of Yucatan minipigs. This prospective, experimental study was designed as follows: Surgery was performed on the left lower eyelid of 4 Yucatan minipigs in accordance with the Massachusetts General Hospital Subcommittee on Research Animal Care guidelines. A 4 x 20-mm strip of acellular porcine dermis was prepared and sutured into place between the tarsus and conjunctiva/lower lid retractors. Tissues were harvested at 6 and 12 weeks and were evaluated histologically. Gross examination revealed vertical elongation of the palpebral conjunctival surface. Histologic evaluation was performed with hematoxylin and eosin and Verhoeff elastin stains. Serial sections demonstrated incorporation of grafted dermal matrix into native tissues without evidence of inflammation. Definitive differentiation between grafted dermis and native dermis was not possible with light microscopy. Portions of the graft appeared to be epithelialized, whereas other histologic regions showed poorly adhesive epithelium. Inflammatory infiltrates including lymphocytes and polymorphonuclear leukocytes were not seen. No epithelioid or giant cells were identified in the sections examined. Acellular homologous dermis produced no measurable untoward effects when implanted as an interpositional graft in the lower eyelid of Yucatan minipigs. On the basis of its material characteristics, it appears to be suitable for this purpose: It is readily available, easily stored, easy to manipulate, and produces minimal inflammation. Long-term persistence, early postoperative histology, and clinical eyelid elevation in humans remain to be evaluated.