An animal model of lower eyelid spacer grafting with acellular dermis

Purpose. Lower eyelid retraction is common in patients with dysthyroid orbi topathy and is seen less commonly in other conditions. Treatment typically requires vertical augmentation of the posterior eyelid lamella with an inte rpositional graft. Several autologous, homologous, and alloplastic material s have been used. We investigated the gross and microscopic in vivo histolo gy of acellular homologous dermis used as a structural interpositional graf t in the lower eyelids of Yucatan minipigs. Methods: This prospective,. experimental study was designed as follows: Sur gery was performed on the left lower eyelid of 4 Yucatan minipigs in accord ance with the Massachusetts General Hospital Subcommittee on Research Anima l Care guidelines. A 4 x 20-mm strip of acellular porcine dermis was prepar ed and sutured into place between the tarsus and conjunctiva/lower lid retr actors. Tissues were harvested at 6 and 12 weeks and were evaluated histolo gically. Results: Gross examination revealed vertical elongation of the palpebral co njunctival surface. Histologic evaluation was performed with hematoxylin an d eosin and Verhoeff elastin stains. Serial sections demonstrated incorpora tion of grafted dermal ma trix into native tissues without evidence of infl ammation. Definitive differentiation between grafted dermis and native derm is was not possible with light microscopy. Portions of the graft appeared t o be epithelialized, whereas other histologic regions showed pearly adhesiv e epithelium. inflammatory infiltrates including lymphocytes and polymorpho nuclear leukocytes were not seen. No epithelioid or giant cells were identi fied in the sections examined. Conclusions: Acellular homologous dermis produced no measurable untoward ef fects when implanted as an interpositional graft in the lower eyelid of Yuc atan 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 in inflammation. Long-term persistence, early postoperative histology, and clinical eyelid elevation in humans rem ain to be evaluated.