Biomechanical properties of expander compared with conventional screws

Biomechanical properties of expander compared with conventional screws

Author Rassi-Neto, A. Google Scholar
Shimano, A. Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract Object. A pullout strength biomechanical study was performed in 20 fresh swine vertebral bodies in which titanium expander (Group 1) and conventional screws (Group 2) were placed.Methods. the screws were inserted into the anterosuperior portion of the anterior spine, and assessment was performed after application of loads. the expander screw is composed of two parts: 1) a cover with an external portion comprising tight thin threads; and 2) a compact internal screw inserted through the cover that allows expansion. in the comparative study between the screws in Groups 1 and 2 maximum load was assessed, and the intergroup difference was significant (p = 0.00001 [t-test]); regarding load at the elasticity threshold, a significant difference was also observed (p = 0.0063). With regard to rigidity (stiffness), there was a tendency in both groups toward significance (p = 0.069). With regard to absorbed energy in the elastic phase, statistical analysis showed a significant intergroup difference (p = 0.00439). the expander screw showed a greater load-bearing capacity than the conventional screw. Adhesion to bone in relation to the applied load and displacement was greater (significant tendency) in the expander screw group than in the conventional screw group.Conclusions. the expander screws exhibited a greater capacity to absorb energy in the elastic phase. They adhered better to bone, were easy to insert, and, if necessary, were simple to remove.
Keywords cervical spine
screw fixation
expander screw
biomechanical study
Language English
Date 2002-10-01
Published in Journal of Neurosurgery. Charlottesville: Amer Assoc Neurological Surgeons, v. 97, n. 3, p. 346-349, 2002.
ISSN 0022-3085 (Sherpa/Romeo, impact factor)
Publisher Amer Assoc Neurological Surgeons
Extent 346-349
Access rights Closed access
Type Article
Web of Science ID WOS:000178765800012

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