Romualdo Rossa

Comparison of synthetic hydroxyapatite and porous polyethylene implants in eviscerated rabbit eyes.

Purpose Synthetic hydroxyapatite and porous polyethylene (Polipore) spheres were placed in rabbits’ eviscerated cavities to evaluate tissue reaction and volume maintenance. Methods Fifty-six Norfolk albino rabbits underwent unilateral evisceration and implantation of synthetic hydroxyapatite (H group, 28 animals) or porous polyethylene spheres (P group, 28 animals). Postoperative reactions, animal behavior, and socket conditions were monitored. Light microscopy and morphometric evaluation with statistical analysis of the exenterated orbits were performed at 7, 15, 30, 60, 90, 120, and 180 days. Scanning electron microscopy was appraised 7, 60, and 180 days after surgery. Results Two animals from the H group and 1 from the P group had extrusion 7 days after surgery. Throughout the experimental period, the synthetic hydroxyapatite caused more inflammation than the porous polyethylene material. Ingrowth in the sphere occurred 7 to 15 days after the surgery in both groups, and the tissue reaction became denser at ≈60 to 90 days, when bony metaplasia began in the H group. Volume maintenance was better in the P group and with a smaller pseudocapsule surrounding the implanted sphere than in the H group. Conclusions Clinical findings demonstrated mild inflammation inside the sphere and in the pseudocapsule surrounding it and better cavity volume maintenance in the P group animals. The authors consider porous polyethylene a more suitable material than synthetic hydroxyapatite for use in anophthalmic cavity reconstruction.

Gelatinous polyethylene in the treatment of the anophthalmic cavity

PURPOSE Gelatinous polyethylene (GP) has been used as an orbital implant to evaluate volume maintenance and tissue reaction in the anophthalmic socket in a rabbit model. METHODS Twenty-eight Norfolk white rabbits underwent unilateral evisceration with placement of 2ml GP (GP group – 16 animals) or 2 ml 0.9% sodium chloride solution (Control group – 12 animals). Animal behavior, postoperative tissue response and socket conditions were evaluated. The animals were sacrificed at 7, 15, 30 and 60 days after the surgery and the bulbs were enucleated; volume maintenance and histopathological evaluation were done in the enucleated bulbs. The results were submitted to statistical analysis. RESULTS All animals showed normal behavior. The orbital volume maintenance was better in the GP group. Histopathology in the GP animals showed mild tissue inflammation throughout the evaluation period and a thin pseudocapsule formation surrounding the orbital implant material. CONCLUSION The clinical findings, good orbital volume maintenance and mild inflammatory tissue response make GP a good choice to replace the lack of volume in anophthalmic socket reconstruction.

A Comparison of Human and Porcine Acellular Dermal Tissues in the Subcutaneous Space of a Rat Model

The study compared the host response to a human and a porcine acellular dermal tissue implanted in the subcutaneous space of a rat model. The human and porcine acellular grafts were surgically implanted in the subcutaneous tissue of rats (5 rats/group) and the materials were evaluated at 7, 15, 30, 60 and 180 postoperative days (PO). The histological immune response was quantified using a digital image analysis system, which evaluated the number of vessels present in the implants and in the surrounding soft tissue, the area of inflammatory cell infiltration in the grafts, the width of the capsular formation present around the tissues and the area of implants absorbed. The data were submitted to statistical analysis. Light microscopy showed mononuclear cellular infiltration, the presence of a capsular formation surrounding the grafts and the presence of vacuolar structures (optically “empty spaces”) inside the implants. The image analysis comparing both materials showed significant inflammatory cells in the human graft at 15 and 30 PO, thicker capsular formation in the porcine tissue at 60 PO, increased number of vessels inside the implants and in the surrounding tissues in the porcine graft and a similar absorption pattern in both materials at 180 PO. The histological findings showed that both tissues were well-tolerated when implanted in the subcutaneous tissue of rats, allowing us to consider the porcine acellular dermal graft as a provisional alternative material for reconstructive plastic surgery.

Tratamento de feridas cutâneas extensas usando tecido dérmico acelular porcino com e sem cobertura impermeável

BACKGROUND - The porcine acellular dermal graft is an alternative for the treatment of skin wounds. OBJECTIVE - To evaluate the clinical and inflammatory response elicited by a porcine derived acellu- lar dermal graft with or without an impermeable dressing. METHODS - A matched-pair longitudinal study was conducted by creating two skin wounds along the dorsal midline of 16 rats (4 rats/group) with implantation of a porcine acellular dermal graft with or without an impermeable dressing . At the 7th, 15th, 30th and 60th postoperative days the animals were evaluated and sacrificed. The acellular tissue and surrounding tissues were removed for his- tological and morphometric analysis. RESULTS - The impermeable dressing persisted on the wounds for up to approximately 15 days. The group without impermeable dressing presented more desiccation, fibrin crust, edema, and inflam- matory reaction in the dermis. At the 60th postoperative day, the group without the impermeable dressing still showed ulcerations, epithelium thinning and lack of keratin, whereas in the group with impermeable dressing the skin was already normal. CONCLUSION - The porcine acellular dermal tissue associated with the impermeable dressing pre- sented better clinical and histological results compared to the porcine acellular dermal tissue with- out the impermeable dressing in extensive wound healing. Keywords: Wound healing; Biocompatible materials; Tissue transplantation Resumo: FUNDAMENTOS - O tecido dermico acelular porcino e alternativa para o tratamento de feri- das cutâneas. OBJETIVO - Avaliar a resposta clinica e inflamatoria do implante de tecido dermico acelular porci- no, com e sem cobertura impermeavel. METODOS - Estudo pareado, longitudinal, criando-se duas feridas cutâneas no dorso de 16 ratos (quatro animais/grupo), em que foi implantado tecido dermico acelular coberto ou nao por impermeavel. Os animais foram avaliados e sacrificados sete, 15, 30 e 60 dias apos a cirurgia, sendo removidos os tecidos acelulares e adjacentes para avaliacao histologica e morfometrica. RESULTADOS - A cobertura impermeavel permaneceu sobre o tecido acelular porcino ate cerca de 15 dias. O grupo sem impermeavel apresentou maior desidratacao, com crosta fibrinoleucocitaria, edema e reacao inflamatoria na derme. Sessenta dias apos a cirurgia, animais do grupo sem impermeavel ainda apresentavam ulceracoes, afinamento do epitelio e ausencia de queratina, enquanto nos do grupo com impermeavel a pele ja se encontrava normal. CONCLUSAO - O tecido dermico acelular porcino com cobertura impermeavel apresentou resultados clinicos e histologicos melhores do que os do tecido dermico acelular porcino sem impermeavel para tratamento de feridas cutâneas extensas. Palavras-chave: Cicatrizacao de feridas; Materias biocompativeis; Transplante de tecidos