Sheep as a large animal model for cochlear implantation.

INTRODUCTION: In surgical training, large animal models are more suitable as their anatomy is more similar to humans. In otology, there have been relatively few studies about large animal models for surgical training. OBJECTIVE: In this study, we aimed to do a neuroradiologic evaluation and surgical insertion of a cochlear implant electrode array on a sheep head model. METHODS: Twenty cadaveric sheep heads were studied. A computed tomography scan and neuroradiologic evaluation was performed on each head, obtaining measurements of the inner ear for each sheep. Sheep measurements were compared to those from temporal bone computed tomography scans from 20 female humans. Surgical procedures were first trained with 13 of the sheep temporal bones, after which cochlear implantation was performed on the remaining 7 temporal bones. The position of the inserted electrode array insertion was confirmed by computed tomography scan after the procedure. RESULTS: Neuroradiologic evaluation showed that, relative to the 20 female humans, the mean ratio for sheep was 0.60 for volume of cochlea, 0.70 for height of cochlea, 0.73 for length of cochlea; ratios for other metrics were >0.80. For the surgical training, the round window was found in all 20 sheep temporal bones. Computed tomography scans confirmed that electrode insertions were fully complete; the mean value of electrode array insertion was 18.3 mm. CONCLUSION: The neuroradiologic and surgical training data suggest that the sheep is a realistic animal model to train cochlear implant surgery and collection of perilymph samples, but less so for surgical training of mastoidectomy due to pneumatization of the mastoid.

Sheep as a large animal model for cochlear implantation / Uso de ovelhas como um modelo animal de grande porte para implante coclear

Abstract Introduction In surgical training, large animal models are more suitable as their anatomy is more similar to humans. In otology, there have been relatively few studies about large animal models for surgical training. Objective In this study, we aimed to do a neuroradiologic evaluation and surgical insertion of a cochlear implant electrode array on a sheep head model. Methods Twenty cadaveric sheep heads were studied. A computed tomography scan and neuroradiologic evaluation was performed on each head, obtaining measurements of the inner ear for each sheep. Sheep measurements were compared to those from temporal bone computed tomography scans from 20 female humans. Surgical procedures were first trained with 13 of the sheep temporal bones, after which cochlear implantation was performed on the remaining 7 temporal bones. The position of the inserted electrode array insertion was confirmed by computed tomography scan after the procedure. Results Neuroradiologic evaluation showed that, relative to the 20 female humans, the mean ratio for sheep was 0.60 for volume of cochlea, 0.70 for height of cochlea, 0.73 for length of cochlea; ratios for other metrics were >0.80. For the surgical training, the round window was found in all 20 sheep temporal bones. Computed tomography scans confirmed that electrode insertions were fully complete; the mean value of electrode array insertion was 18.3 mm. Conclusion The neuroradiologic and surgical training data suggest that the sheep is a realistic animal model to train cochlear implant surgery and collection of perilymph samples, but less so for surgical training of mastoidectomy due to pneumatization of the mastoid.

Resumo Introdução No treinamento cirúrgico, os modelos animais de grande porte são mais adequados, pois sua anatomia é mais semelhante à humana. Em otologia, existem relativamente poucos estudos com modelo animal de grande porte para treinamento cirúrgico. Objetivo Fazer a avaliação neurorradiológica e a inserção cirúrgica de um eletrodo de implante coclear em um modelo de ovelha. Método Vinte cabeças de cadáveres de ovelhas foram estudadas. Foram feitas tomografia computadorizada e avaliação neurorradiológica de cada cabeça, obtiveram‐se medidas da orelha interna de cada ovelha. As medidas das ovelhas foram comparadas às de tomografias computadorizadas do osso temporal de 20 mulheres. Os procedimentos cirúrgicos foram inicialmente treinados com 13 dos ossos temporais de ovelhas, após o qual o implante coclear foi feito nos 7 ossos temporais restantes. A posição de inserção do arranjo de eletrodos foi confirmada por tomografia computadorizada após o procedimento. Resultados A avaliação neurorradiológica mostrou que, em comparação às 20 mulheres, a proporção média para as ovelhas foi de 0,60 para o volume da cóclea, 0,70 para a altura da cóclea, 0,73 para o comprimento da cóclea; as proporções para as outras medidas foram > 0,80. Em relação ao treinamento cirúrgico, a janela redonda foi encontrada em todos os 20 ossos temporais de ovelhas. A tomografia computadorizada confirmou que as inserções dos eletrodos foram totalmente completas; o valor médio da inserção do arranjo de eletrodos foi de 18,3 mm. Conclusão Os dados do treinamento neurorradiológico e cirúrgico sugerem que a ovelha é um modelo animal realista para o treinamento da cirurgia de implante coclear e coleta de amostras da perilinfa, mas não tão realista para o treinamento cirúrgico de mastoidectomia devido à pneumatização da mastoide.