Avaliação por meio de elementos finitos da fixação interna com placas tipo grade em dois diferentes tipos de osteotomia sagital do ramo mandibular
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Data
2021-03-09
Autores
Jacob, Eduardo Santana
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Universidade Estadual Paulista (Unesp)
Resumo
A osteotomia sagital dos ramos mandibulares (OSRM) é o procedimento cirúrgico mais utilizado para correção das deformidades na mandíbula. Sua versatilidade e ampla descrição na literatura assegura sua utilização no tratamento das principais desarmonias faciais. Diversas alterações foram propostas ao longo dos anos com o objetivo de proporcionar estabilidade dos segmentos, previsibilidade no tratamento e redução da morbidade cirúrgica. Diferentes métodos de fixação interna estável da OSRM são utilizados, sendo os mais comuns: uma placa com parafusos monocorticais, duas placas com parafusos monocorticais, três parafusos bicorticais em diferentes posições e uma placa com parafusos monocorticais associado a parafusos aposicionais. As placas tipo grade vem sendo utilizadas com sucesso no tratamento das fraturas de ângulos mandibulares, apresentando-se como alternativa ao uso das placas convencionais. Os sistemas tridimensionais permitem uma simples adaptação simultânea da borda superior e inferior da placa ao osso pelo acesso intra-oral, com a facilidade de manutenção do posicionamento ósseo durante a fixação. O uso da análise de elementos finitos permite avaliar, em um modelo matemático, as estruturas de interesse em um ambiente controlado, bem como a aplicação de forças em qualquer ponto e/ou direção, medindo a deformação dos materiais e a tensão aplicada aos mesmos. Devido a escassez de trabalhos avaliando a viabilidade da osteossíntese da OSRM convencional e osteotomias mandibulares curtas com as placas tipo grade, o presente trabalho avaliou a distribuição de tensão sobre as placas, parafusos e estrutura óssea adjacente, pelo método de análise de elementos finitos tridimensional, em dois tipos de avanços lineares. Os dados foram avaliados por meio da distribuição de tensão von Mises nos materiais considerados dúcteis (placas e parafusos) e pelas tensões máximas principais nos materiais não dúcteis (osso cortical e medular). O trabalho concluiu que o aumento do avanço mandibular resultou em uma maior tensão sobre o tecido ósseo, placas e parafusos em ambas as osteotomias e que a osteotomia curta apresentou-se com a menor distribuição de tensão, dentre todos os modelos, no avanço linear de 5,00 milímetros, sugerindo uma maior segurança clínica na sua utilização.
Bilateral Sagittal Split Osteotomy (BSSO) is the most widely used surgical procedure to correct mandibular deformities. Its versatility and wide description in the literature ensures its use in the treatment of the main facial disharmonies. Several changes have been proposed over the years in order to provide stability of the segments, predictability in the treatment and reduction of surgical morbidity. Different methods of stable internal fixation of the BSSO are used, the most common being: a plate with monocortical screws, two plates with monocortical screws, three bicortical screws in different positions and a plate with monocortical screws associated with appositional screws. Grid-type plates have been used successfully in the treatment of mandibular angle fractures, presenting themselves as an alternative to the use of conventional plates. The three-dimensional systems allow a simple simultaneous adaptation of the upper and lower edge of the plate to the bone by intraoral access, with the ease of maintaining bone positioning during fixation. The use of finite element analysis allows to evaluate, in a mathematical model, the structures of interest in a controlled environment, as well as the application of forces at any point and / or direction, measuring the deformation of the materials and the stress applied to them. Due to the scarcity of studies evaluating the viability of osteosynthesis of conventional BSSO and short mandibular osteotomies with grid-type plates, the present work evaluated the stress distribution on the plates, screws and adjacent bone structure, using the three-dimensional finite element analysis method in two types of linear feeds. The data were evaluated by means of von Mises stress distribution in materials considered ductile (plates and screws) and by the main maximum stresses in non-ductile materials (cortical and medullary bone). The work concluded that the increase in the mandibular advancement resulted in a greater tension on the bone tissue, plates and screws in both osteotomies and that the short osteotomy presented with the lowest stress distribution, among all models, in the linear advancement of 5.00 mm, suggesting greater clinical safety in its use.
Bilateral Sagittal Split Osteotomy (BSSO) is the most widely used surgical procedure to correct mandibular deformities. Its versatility and wide description in the literature ensures its use in the treatment of the main facial disharmonies. Several changes have been proposed over the years in order to provide stability of the segments, predictability in the treatment and reduction of surgical morbidity. Different methods of stable internal fixation of the BSSO are used, the most common being: a plate with monocortical screws, two plates with monocortical screws, three bicortical screws in different positions and a plate with monocortical screws associated with appositional screws. Grid-type plates have been used successfully in the treatment of mandibular angle fractures, presenting themselves as an alternative to the use of conventional plates. The three-dimensional systems allow a simple simultaneous adaptation of the upper and lower edge of the plate to the bone by intraoral access, with the ease of maintaining bone positioning during fixation. The use of finite element analysis allows to evaluate, in a mathematical model, the structures of interest in a controlled environment, as well as the application of forces at any point and / or direction, measuring the deformation of the materials and the stress applied to them. Due to the scarcity of studies evaluating the viability of osteosynthesis of conventional BSSO and short mandibular osteotomies with grid-type plates, the present work evaluated the stress distribution on the plates, screws and adjacent bone structure, using the three-dimensional finite element analysis method in two types of linear feeds. The data were evaluated by means of von Mises stress distribution in materials considered ductile (plates and screws) and by the main maximum stresses in non-ductile materials (cortical and medullary bone). The work concluded that the increase in the mandibular advancement resulted in a greater tension on the bone tissue, plates and screws in both osteotomies and that the short osteotomy presented with the lowest stress distribution, among all models, in the linear advancement of 5.00 mm, suggesting greater clinical safety in its use.
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Palavras-chave
Cirurgia ortognática, Osteotomia, Mandíbula, Fixadores internos, Análise de elementos finitos, Orthognathic surgery, Osteotomy, Mandible, Internal fixators, Finite element analysis