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Este trabalho teve como objetivo avaliar o comportamento in vivo de uma membrana inovadora para fusão posterolateral da coluna vertebral, com base em análises de tomografia computorizada (TAC) de vértebras de ovelhas removidas após eutanásia. A membrana utilizada (HPMC-Mix) é um material compósito inovador com uma matriz polimérica de hidroxipropilmetilcelulose (HPMC), um polissacarídeo biodegradável derivado da celulose e um material de reforço à base de fosfato tricálcico e hidroxiapatite. Pretende-se que esta membrana
promova a regeneração óssea e funcione como uma ponte óssea na união dos processos transversos de vértebras adjacentes, pelo que deverá apresentar propriedades osteocondutoras, osteointegrativas e osteoindutoras, destacando-se assim dos demais produtos disponíveis no mercado, os quais apresentam uma eficiência regenerativa muito aquém da exigida para a aplicação pretendida. É prioridade a futura comercialização da membrana em estudo, que em virtude das suas características inovadoras poderá produzir um impacto significativo no aumento da taxa de sucesso da cirurgia de fusão espinhal posterolateral, a qual é atualmente bastante reduzida (10-40 %). Recorrendo à técnica de tomografia computorizada obtiveram-se os datasets das implantações de dois materiais (membrana HPMC-Mix e um material disponível no mercado, utilizado em aplicações cirúrgicas e com propriedades conhecidas (ChronOS)), em animais ex vivo, obtidas
em marcos temporais de 15 dias, 3 meses e 6 meses após a cirurgia. Seguidamente reconstruiram-se os datasets e separaram-se os volumes da amostra onde se encontra cada um dos dois materiais, com recurso ao DataViewer para posterior quantificação, já que ambos os materiais estavam implantados para unir os processos transversos adjacentes das vértebras L4-L5, porém em lados opostos. Seguiu-se a segmentação da região de interesse das amostras e o cálculo do seu volume e densidade mineral óssea, com recurso ao software CTAn. Um modelo ANOVA sem repetições foi aplicado aos resultados da quantificação dos volumes de cada lado, assim como da densidade mineral óssea nas amostras de 15 dias, 3 e 6 meses após cirurgia. Os resultados obtidos do valor p foram superiores a 0,05, indicando que não há diferenças estatisticamente significativas entre o comportamento dos dois implantes nem entre os valores obtidos nos diferentes timepoints, exceto na comparação entre o BMD e no Object Volume/Total Volume, pelo que se seguiu a aplicação do teste post hoc Tukey's HSD, com o objetivo de determinar quais os grupos temporais que são significativamente diferentes entre si. Após avaliação do último modelo estatístico concluiu-se que não existem diferenças estatisticamente significativas em nenhuma das combinações entre os resultados dos timepoints, pelo que se conclui que o material em estudo é um potencial substituto ósseo, com a vantagem de ser mais
maleável em aplicação cirúrgica, adaptando-se melhor ao defeito, comparativamente com o material comercial ChronOS.
This study aimed to evaluate the in vivo behavior of an innovative membrane for posterolateral spinal fusion, based on computed tomography (CT) analyses of sheep vertebrae removed after euthanasia. The membrane used (HPMC-Mix) is an innovative composite material with a polymeric matrix of hydroxypropylmethyl cellulose (HPMC), a biodegradable polysaccharide derived from cellulose and a reinforcement material based on tricalcium phosphate and hydroxyapatite. This membrane is intended to promote bone regeneration and function as a bone bridge in the union of the transverse processes of adjacent vertebrae, and should therefore present osteoconductive, osteointegrative and osteoinductive properties, thus standing out from other products available on the market, which present a regenerative efficiency far below that required for the intended application. The future commercialization of the membrane under study is a priority, as its innovative characteristics could have a significant impact on increasing the success rate of posterolateral spinal fusion surgery, which is currently quite low (10-40%). Using computed tomography, datasets were obtained from the implantations of two materials (HPMC-Mix membrane and a commercially available material used in surgical applications and with known properties (ChronOS)) in ex vivo animals, obtained at timepoints of 15 days, 3 months, and 6 months after surgery. The datasets were then reconstructed and the sample volumes containing each of the two materials were separated using DataViewer for later quantification, since both materials were implanted to join the adjacent transverse processes of the L4-L5 vertebrae, but on opposite sides. The region of interest of the samples was segmented and their volume and bone mineral density were calculated using the CTAn software. An ANOVA model without repetitions was applied to the results of the quantification of the volumes of each side, as well as the bone mineral density in the samples obtained 15 days, 3 and 6 months after surgery. The results obtained for the p-value were greater than 0.05, indicating that there are no statistical significant differences between the behavior of the two implants or between the values obtained at the different timepoints, except in the comparison between the BMD and the Object Volume/Total Volume, so the post hoc Tukey's HSD test was applied, with the aim of determining which time groups are significantly different from each other. After evaluating the last statistical model, it was concluded that there are no significant statistical differences in any of the combinations between the timepoint results, therefore it is concluded that the material under study is a potential bone substitute, with the advantage of being more malleable in surgical application, adapting better to the defect, compared to the commercial material ChronOS.
This study aimed to evaluate the in vivo behavior of an innovative membrane for posterolateral spinal fusion, based on computed tomography (CT) analyses of sheep vertebrae removed after euthanasia. The membrane used (HPMC-Mix) is an innovative composite material with a polymeric matrix of hydroxypropylmethyl cellulose (HPMC), a biodegradable polysaccharide derived from cellulose and a reinforcement material based on tricalcium phosphate and hydroxyapatite. This membrane is intended to promote bone regeneration and function as a bone bridge in the union of the transverse processes of adjacent vertebrae, and should therefore present osteoconductive, osteointegrative and osteoinductive properties, thus standing out from other products available on the market, which present a regenerative efficiency far below that required for the intended application. The future commercialization of the membrane under study is a priority, as its innovative characteristics could have a significant impact on increasing the success rate of posterolateral spinal fusion surgery, which is currently quite low (10-40%). Using computed tomography, datasets were obtained from the implantations of two materials (HPMC-Mix membrane and a commercially available material used in surgical applications and with known properties (ChronOS)) in ex vivo animals, obtained at timepoints of 15 days, 3 months, and 6 months after surgery. The datasets were then reconstructed and the sample volumes containing each of the two materials were separated using DataViewer for later quantification, since both materials were implanted to join the adjacent transverse processes of the L4-L5 vertebrae, but on opposite sides. The region of interest of the samples was segmented and their volume and bone mineral density were calculated using the CTAn software. An ANOVA model without repetitions was applied to the results of the quantification of the volumes of each side, as well as the bone mineral density in the samples obtained 15 days, 3 and 6 months after surgery. The results obtained for the p-value were greater than 0.05, indicating that there are no statistical significant differences between the behavior of the two implants or between the values obtained at the different timepoints, except in the comparison between the BMD and the Object Volume/Total Volume, so the post hoc Tukey's HSD test was applied, with the aim of determining which time groups are significantly different from each other. After evaluating the last statistical model, it was concluded that there are no significant statistical differences in any of the combinations between the timepoint results, therefore it is concluded that the material under study is a potential bone substitute, with the advantage of being more malleable in surgical application, adapting better to the defect, compared to the commercial material ChronOS.
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Keywords
Posterolateral fusion Vertebrae HPCM-Mix membrane Micro-CT Bone mineral density Bone volume New bone formation Ovis aries animal model Fusão Posterolateral Vértebras Membrana HPCM-Mix, Micro-CT Densidade mineral óssea Volume ósseo Formação de novo osso Modelo animal Ovis aries Modelo animal Ovis aries