Análise comparativa de diferentes configurações de bloqueio de haste intramedular bloqueada submetidas à compressão axial
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Data
2022-05-05
Autores
de Souza, Gislane Vasconcelos [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Objetiva-se avaliar o bloqueio ortogonal em hastes intramedulares bloqueadas, com e sem estabilidade angular, comparativamente ao sistema de bloqueio paralelo, por meio de testes biomecânicos de compressão axial. Para tal foram utilizados corpos de prova impressos em impressora 3D com falha crítica (20 mm) simulando cominuição diafisária. As hastes foram confeccionadas com 175 mm de comprimento e 8 mm de diâmetro, e divididas em quatro grupos (sete unidades cada). O grupo 1 (G1) foi composto por hastes intramedulares com dois orifícios no segmento proximal e dois no segmento distal, todos roscados, para promover bloqueio dos parafusos com a haste (ângulo estável) e com as corticais dos corpos de prova; neste modelo os orifícios do implante foram dispostos no mesmo plano. No grupo 2 (G2), utilizou-se o mesmo sistema de bloqueio do G1, porém com disposição ortogonal dos orifícios de bloqueio. Já no grupo 3 (G3) o sistema de bloqueio foi formado por bolts específicos confeccionados para acoplamento junto aos orifícios da haste intramedular sem rosqueamento (sem ângulo estável), com corpo maciço e liso, e extremidade proximal com filetes de rosca para interação com a cortical cis do corpo de prova. Neste grupo os orifícios de bloqueio da haste foram dispostos de maneira paralela. No grupo 4 (G4), o mecanismo de bloqueio foi o mesmo do G3, porém com disposição dos orifícios de maneira ortogonal. Foram obtidos resultados de força máxima (N), rigidez (N/mm) e deformação máxima (mm). Força e deformação máxima foram avaliadas pela análise de variância (ANOVA), seguido pelo teste post-hoc de Tukey. Para a variável rigidez foi aplicado teste não paramétrico de Kruskal-Wallis, seguido pelo post-hoc de Dunn. Nível de significância de 5% foi adotada em todas as análises. O grupo 2 obteve o maior valor absoluto de rigidez (4573,14 N/mm), porém sem diferença estatística quanto a média entre os demais grupos para esta variável. O grupo 4, embora tenha sustentado a menor força máxima (16984,07 N) entre os grupos avaliados, foi o grupo que deformou menos (média 8,74 mm). Assim, o bloqueio ortogonal apresenta similaridade mecânica em testes destrutivos de compressão axial e podem representar excelentes alternativas a hastes com bloqueio paralelo, especialmente quando a configuração da fratura limita o seu uso, possibilitando a fixação de dois parafusos mesmo na presença de limitado estoque ósseo. No entanto, estudos clínicos são necessários para avaliar o comportamento de tais implantes frente ao ambiente biológico.
The objective is to evaluate the orthogonal locking in interlocking nails, with and without angular stability, compared to the parallel locking system, through axial compression tests. For this purpose, prototyped specimens with critical failure (20 mm) were used, simulating diaphyseal comminution. The nails were made with 175 mm in length and 8 mm in diameter, and divided into four groups (seven units each). Group 1 (G1) was composed of intramedullary nails with two holes in the proximal segment and two in the distal segment, all threaded, to promote locking of the screws with the nail (stable angle) and with the cortical bones of the specimens; in this model, the implant holes were arranged in the same plane. In group 2 (G2), the same locking system as in G1 was used, but with an orthogonal disposition of the blocking holes. In group 3 (G3), the locking system was formed by specific bolts made for coupling with the nail holes without threading (no stable angle), with a solid and smooth body, and proximal end with threads for interaction with the cis cortical of the specimen. In this group the locking holes of the nail were arranged in a parallel way. In group 4 (G4), the locking mechanism was the same as in G3, but with orthogonally arranged. The means will be compared with Student's t test with a significance level of 5%. Group 2 obtained the highest absolute value of stiffness (4573.14 N/mm), but with no statistical difference regarding the mean between the other groups for this variable. Group 4, despite having sustained the lowest maximum force (16984.07 N) among the groups evaluated, was the group that deformed the least (average 8.74 mm). Thus, orthogonal locking presents mechanical similarity in destructive axial compression tests and may represent excellent alternatives to nails with parallel locking, especially when the fracture configuration limits its use, allowing the fixation of two screws even in the presence of limited bone stock. However, clinical studies are needed to evaluate the behavior of such implants in the biological environment.
The objective is to evaluate the orthogonal locking in interlocking nails, with and without angular stability, compared to the parallel locking system, through axial compression tests. For this purpose, prototyped specimens with critical failure (20 mm) were used, simulating diaphyseal comminution. The nails were made with 175 mm in length and 8 mm in diameter, and divided into four groups (seven units each). Group 1 (G1) was composed of intramedullary nails with two holes in the proximal segment and two in the distal segment, all threaded, to promote locking of the screws with the nail (stable angle) and with the cortical bones of the specimens; in this model, the implant holes were arranged in the same plane. In group 2 (G2), the same locking system as in G1 was used, but with an orthogonal disposition of the blocking holes. In group 3 (G3), the locking system was formed by specific bolts made for coupling with the nail holes without threading (no stable angle), with a solid and smooth body, and proximal end with threads for interaction with the cis cortical of the specimen. In this group the locking holes of the nail were arranged in a parallel way. In group 4 (G4), the locking mechanism was the same as in G3, but with orthogonally arranged. The means will be compared with Student's t test with a significance level of 5%. Group 2 obtained the highest absolute value of stiffness (4573.14 N/mm), but with no statistical difference regarding the mean between the other groups for this variable. Group 4, despite having sustained the lowest maximum force (16984.07 N) among the groups evaluated, was the group that deformed the least (average 8.74 mm). Thus, orthogonal locking presents mechanical similarity in destructive axial compression tests and may represent excellent alternatives to nails with parallel locking, especially when the fracture configuration limits its use, allowing the fixation of two screws even in the presence of limited bone stock. However, clinical studies are needed to evaluate the behavior of such implants in the biological environment.
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Palavras-chave
Ortopedia., Bloqueio., Biomecânica., Fixação interna de fraturas.