gms | German Medical Science

65th Annual Meeting of the German Society of Neurosurgery (DGNC)

German Society of Neurosurgery (DGNC)

11 - 14 May 2014, Dresden

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New pedicle screw design with expandable shell for low bone quality

Meeting Abstract

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  • Onur Yaman - Tepecik Education and Research Hospital, Department of Neurosurgery, Izmir, Turkey
  • Teyfik Demir - TOBB University of Economics and Technology, Department of Mechanical Engineering, Ankara, Turkey
  • Mehmet Fatih Örmeci - TOBB University of Economics and Technology, Department of Mechanical Engineering, Ankara, Turkey
  • Can Yaldiz - Sakarya Education and Research Hospital, Department of Neurosurgery, Sakarya, Turkey
  • Adem Bursali - Balikesir State Hospital, Neurosurgery, Sakarya, Turkey
  • Mustafa Özkaya - TOBB University of Economics and Technology, Department of Mechanical Engineering, Ankara, Turkey

Deutsche Gesellschaft für Neurochirurgie. 65. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC). Dresden, 11.-14.05.2014. Düsseldorf: German Medical Science GMS Publishing House; 2014. DocDI.13.08

doi: 10.3205/14dgnc193, urn:nbn:de:0183-14dgnc1939

Published: May 13, 2014

© 2014 Yaman et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

Outline

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Objective: Pullout strength of the pedicle screws depend on several factors such as core geometry, size, bone mineral density (BMD). Expandable pedicle screws (EPS) provide superior pullout strength. EPS’s are formed like an inverse conical geometry inside bones. In this study, a novel pedicle screw fixation system was designed and manufactured.

Method: The novel fixation system is designed as a fixing plug and screw assembly. It contains a PEEK outer shell and a Ti6Al4V core component. The outer shell’s expansion mechanism is designed as two-pin plug. Shell’s both inner and outer surfaces are designed as conical structure. The core is also designed in conical structure and core head is assembled with a standard poly-axial screw head. The novel system was tested according to ASTM F543. Polyurethane Grade 20 foams were used.

Results: Three revisions completed on first design. Also randomly selected conical core classical pedicle screw (CPS) is selected from our laboratory database. Over than 40 different screw designs tested according to ASTM F543, F1798 and F1717. Novel design exhibited significantly higher pullout performance than the classical pedicle screw. (P<0,05) On the other hand pullout test results between revision are not drastically higher or lower than each other. P values are 0,05 and 0,048 between Rev3-Rev1 and Rev3-Rev-2, respectively.

Conclusions: The novel modular fixation system was biomechanically evaluated. Tested specimen’s pullout strength was 1196,3 N by performing static pullout test according to ASTM F543. This result is drastically higher than the classical pedicle fixation screws. In addition to this, PEEK shell’s fusion tendency will provide an extra durability to the system. Using a polymer-based shell will provide to absorb micro vibrations which cause micro fractures and accelerate the pullout of screw.