Direct vertebral rotation significantly decreases the pullout strength of the pedicle screw: a biomechanical study in adult cadavers

Kerim Sariyilmaz*, Okan Ozkunt, Halil Can Gemalmaz, Tunca Cingoz, Tuna Pehlivanoglu, Tamer Aksoy, Ozcan Kaya, Murat Baydogan, Fatih Dikici

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

The pullout strength of the pedicle screws after direct vertebral rotation (DVR) maneuver is not known. This biomechanical study was performed to quantitatively analyze the pullout strength of a pedicle screw after DVR maneuver using human cadaveric vertebrae. Thoracic vertebral bodies from three cadavers were harvested and stripped of soft tissues. Thirty pedicles of 15 vertebrae were separated into two groups after bone mineral density measurements. Polyaxial 5.5 mm pedicle screws with appropriate length were inserted with a freehand technique for each pedicle. One Kirschner wire was inserted to the anterior part of each vertebral corpus the half depth of each corpus was embedded into PVC pipes using polyester paste. In the DVR group, each screw was pulled horizontally with 2 kg (~20 N) load over a screwdriver rigidly attached to the screw, and a DVR maneuver was simulated. The control group did not load with a DVR maneuver. Samples were placed on a universal testing machine and pullout loads were measured. The Mann–Whitney U test was utilized, and the P value <0.05 was considered as statistically significant. In the DVR group, the mean pullout strength was 183.35 N (SD ± 100.12), and in the control group, the mean pullout strength was 279.95 N (SD ± 76.26). Intergroup comparisons revealed that DVR maneuver significantly decreases the pullout strength (P= 0.012). The results of this study confirm that the pullout strength of pedicle screw significantly decreases by approximately 35% when DVR maneuver is applied.

Original languageEnglish
Pages (from-to)230-234
Number of pages5
JournalJournal of Pediatric Orthopaedics Part B
Volume30
Issue number3
DOIs
Publication statusPublished - 1 May 2021

Bibliographical note

Publisher Copyright:
Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.

Funding

We thank Acibadem Mehmet Ali Aydinlar University for donation of the cadavers. Implants for this study were donated by Tasarim Medical Turkey.

FundersFunder number
Acibadem Mehmet Ali Aydinlar University

    Keywords

    • biomechanical
    • cadaveric vertebra
    • direct vertebral rotation
    • pedicle screw
    • pullout strength

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