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Artigo Original • Rev. bras. ortop. 57 (02) • 2022 • https://doi.org/10.1055/s-0041-1732390   copy

The Influence of Thread Tap Mismatch on Pedicle Screw Pullout Strength* * Work developed at the Laboratório de Bioengenharia da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo, Ribeirão Preto, SP, Brasil.

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Objective

We aimed to study the “in vitro” pullout strength of SpineGuard/Zavation Dynamic Surgical Guidance Z-Direct Screw (DSG Screw, SpineGuard Inc, Boulder, Colorado, USA), a screw designed to be inserted using a direct insertion technique.

Methods

Dynamic Surgical Guidance Screws of 5.5 and 6.5 mm were introduced into polyurethane blocks with a density of 10 PCF (0,16g/cm3). According to the experimental group, screws were inserted without pilot hole, with pilot without tapping, undertapping and line-to-line tapping. Screw pullout tests were performed using a universal test machine after screw insertion into polyurethane blocks.

Results

Screws inserted directly into the polyurethane blocks without pilot hole and tapping showed a statistically higher pullout strength. Insertion of the screw without tapping or with undertapping increases the pullout screw strength compared with lineto-line tapping.

Conclusion

Dynamic Surgical Guidance Screw showed the highest pullout strength after its insertion without pilot hole and tapping.

Keywords:
spinal fusion; pedicle screw; bone screws; biomechanical phenomena/ physiology

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E-mail: rbo@sbot.org.br
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