Open AccessBiomechanical Study of the Pullout Resistance in Screws of a Vertebral Fixation System
Author(s) -
Sarah Fakher Fakhouri,
Ariane Zamarioli,
Célia Regina Galloro Wichr,
Cleudmar Araújo,
Helton Luíz Aparecido Defino,
Antônio Carlos Shimano
Publication year - 2011
Publication title -
advances in mechanical engineering/advances in mechanical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.318
H-Index - 40
eISSN - 1687-8140
pISSN - 1687-8132
DOI - 10.1155/2011/701263
Subject(s) - photoelasticity , stiffness , fixation (population genetics) , biomechanics , materials science , orthodontics , materials testing , composite material , medicine , anatomy , population , environmental health , solid mechanics
The purpose of this study was to investigate the effect of varying the outer diameter of screws of a vertebral fixation system by submitting them to mechanical tests and photoelasticity. The pullout mechanical test was performed in 20 swine lumbar vertebrae, divided into two groups based on the screw outer diameter: 5.0 and 6.0 mm. The maximal pullout strengths and stiffness were evaluated. For the photoelasticity, eight models were used and divided into the same groups. The maximal pullout strength was 974.12 ± 144.44 N in the 5.0 mm screws and 1537.42 ± 326.95 N in the 6.0 mm screws (P ┼ 0.001). The stiffness was 418.60 ± 62.58 103N/m in the 5.0 mm screws and 502.12 ± 133.45 103N/m in the 6.0 mm screws (P = 0.09). The mean ± SD shear stress of the 5.0 mm screws was 12.90 ± 1.87 KPa and 11.99 ± 2.01 KPa for the 6.0 mm screws. Thus, the 5.0 mm screw had lower pullout and higher shear stress, suggesting that this screw is more susceptible to loosening