In Vitro Biomechanical Study of Pedicle Screw Pull-out Strength Based on Different Screw Path Preparation Techniques

Overview

Journal Indian J Orthop

Publisher Springer Nature

Specialty Orthopedics

Date 2016 Apr 8

PMID 27053808

Citations 1

Authors

Mark Moldavsky

Kanaan Salloum

Brandon Bucklen

Saif Khalil

Jwalant S Mehta

Affiliations

Soon will be listed here.

Abstract

Background: Poor screw-to-bone fixation is a clinical problem that can lead to screw loosening. Under-tapping (UT) the pedicle screw has been evaluated biomechanically in the past. The objective of the study was to determine if pedicle preparation with a sequential tapping technique will alter the screw-to-bone fixation strength using a stress relaxation testing loading protocol.

Materials And Methods: Three thoracolumbar calf spines were instrumented with pedicle screws that were either probed, UT, standard-tapped (ST), or sequential tapped to prepare the pedicle screw track and a stress relaxation protocol was used to determine pull-out strength. The maximum torque required for pedicle screw insertion and pull-out strength was reported. A one-way ANOVA and Tukeys post-hoc test were used to determine statistical significance.

Results: The pedicle screw insertion torques for the probed, UT, ST and sequentially tapped (SQT) techniques were 5.09 (±1.08) Nm, 5.39 (±1.61) Nm, 2.93 (±0.43) Nm, and 3.54 (±0.67) Nm, respectively. There is a significant difference between probed compared to ST (P ≤ 0.05), as well as UT compared to both ST and SQT (P ≤ 0.05). The pull-out strength for pedicle screws for the probed, UT, ST and SQT techniques was 2443 (±782) N, 2353(±918) N, 2474 (±521) N, and 2146 (±582) N, respectively, with no significant difference (P ≥ 0.05) between techniques.

Conclusions: The ST technique resulted in the highest pull-out strength while the SQT technique resulted in the lowest. However, there was no significant difference in the pull-out strength for the various preparation techniques and there was no correlation between insertion torque and pull-out strength. This suggests that other factors such as bone density may have a greater influence on pull-out strength.

Citing Articles

Risk Factors for Clinically Relevant Loosening of Percutaneous Pedicle Screws.

Ohba T, Ebata S, Oba H, Koyama K, Haro H Spine Surg Relat Res. 2019; 3(1):79-85.

PMID: 31435556 PMC: 6690121. DOI: 10.22603/ssrr.2018-0018.

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