Special Section Technical Briefs

Spinal Pedicle Screw Design Retains Grip Strength After Loosening and Relocking1

[+] Author and Article Information
David J. Nuckley, Krishna C. Vedula, Hugh Hestad, John Dawson

Research and Development,
Zimmer Spine,
Minneapolis, MN 55439

Accepted and presented at The Design of Medical Devices Conference (DMD2015), April 13–16, 2015, Minneapolis, MN, USA.

Manuscript received March 3, 2015; final manuscript received March 17, 2015; published online July 16, 2015. Editor: Arthur Erdman.

J. Med. Devices 9(3), 030901 (Sep 01, 2015) (2 pages) Paper No: MED-15-1056; doi: 10.1115/1.4030542 History: Received March 03, 2015; Revised March 17, 2015; Online July 16, 2015

First Page Preview

View Large
First page PDF preview
Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.


Brasiliense, L. B., Lazaro, B. C., Reyes, P. M., Newcomb, A. G., Turner, J. L., Crandall, D. G., and Crawford, N. R., 2013, “Characteristics of Immediate and Fatigue Strength of a Dual-Threaded Pedicle Screw in Cadaveric Spines,” Spine J., 13(8), pp. 947–956. [CrossRef] [PubMed]
Kwok, A. W., Finkelstein, J. A., Woodside, T., Hearn, T. C., and Hu, R. W., 1996, “Insertional Torque and Pull-Out Strengths of Conical and Cylindrical Pedicle Screws in Cadaveric Bone,” Spine, 21(21), pp. 2429–2434. [CrossRef] [PubMed]
Demir, T., and Camuşcuz, N., 2012, “Design and Performance of Spinal Fixation Pedicle Screw System,” Proc. Inst. Mech. Eng., Part H, 226(1), pp. 33–40. [CrossRef]
Fogel, G. R., Reitman, C. A., Liu, W., and Esses, S. I., 2003, “Physical Characteristics of Polyaxial-Headed Pedicle Screws and Biomechanical Comparison of Load With Their Failure,” Spine, 28(5), pp. 470–473. http://journals.lww.com/spinejournal/Fulltext/2003/03010/Physical_Characteristics_of_Polyaxial_Headed.11.aspx [PubMed]


Grahic Jump Location
Fig. 1

Experimental evaluation of pedicle screw–rod interface via ASTM F1798-13 axial (a), torsional (b), and flexion/extension (c) grip strength testing

Grahic Jump Location
Fig. 2

Experimental results of axial grip testing. Notice that design B increases in axial grip, while design A decreases after one cycle of tightening, loosening, and tightening.

Grahic Jump Location
Fig. 3

Experimental results of torsional grip testing. Design A experiences a marked decrease in torsional grip strength, while design B increases in grip strength.



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In