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Journal cover: International Journal of Structural Integrity

International Journal of Structural Integrity

ISSN: 1757-9864

Online from: 2010

Subject Area: Mechanical & Materials Engineering

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Application of laser shock peening for spinal implant rods


Document Information:
Title:Application of laser shock peening for spinal implant rods
Author(s):S.R. Mannava, (College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio, USA), Sagar Bhamare, (College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio, USA), Vibhor Chaswal, (College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio, USA), Leonora Felon, (X-spine Systems Inc., Dayton, Ohio, USA), David Kirschman, (X-spine Systems Inc., Dayton, Ohio, USA), David Lahrman, (LSP Technologies Inc., Dublin, Ohio, USA), Richard Tenaglia, (LSP Technologies Inc., Dublin, Ohio, USA), Dong Qian, (College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio, USA), Vijay Vasudevan, (College of Engineering and Applied Science, University of Cincinnati, Cincinnati, Ohio, USA)
Citation:S.R. Mannava, Sagar Bhamare, Vibhor Chaswal, Leonora Felon, David Kirschman, David Lahrman, Richard Tenaglia, Dong Qian, Vijay Vasudevan, (2011) "Application of laser shock peening for spinal implant rods", International Journal of Structural Integrity, Vol. 2 Iss: 1, pp.101 - 113
Keywords:Fatigue, Finite element analysis, Medical appliances, Spinal cord
Article type:Technical paper
DOI:10.1108/17579861111108653 (Permanent URL)
Publisher:Emerald Group Publishing Limited
Acknowledgements:University of Cincinnati acknowledges the contribution of the State of Ohio, Department of Development and Third Frontier Commission, which provided funding in support of “Ohio Center for Laser Shock Processing for Advanced Material and Devices”. This publication was prepared with financial support from the State of Ohio. The content reflects the views of the authors and does not purport to reflect the views of the State of Ohio.
Abstract:

Purpose – The current industry standard rigid spinal implants suffer fatigue failures due to bending and torsion loads. The purpose of this program was to design novel prototype flexible titanium alloy spinal implant rod with machined features, and then apply the laser shock peening (LSP) process to restore the fatigue strength debit due to these features.

Design/methodology/approach – A flexible prototype rod was designed with flat section at the center of the rod. The flat section was laser shock peened. Static compression tests were conducted as per American Society of Testing Materials standards for three- and four-point bending tests and “vertebrectomy” constructs. Finite element models were developed to aid in the design of LSP and also to guide the experiments.

Findings – The test results indicated a ~3X improvement in flexibility and a reduction in fatigue load ratio, defined as applied load divided by the yield load; from 72 to 68 percent. This rod was LSP's on the flat sections, and tested again. The results indicated an increase in the fatigue load ratio from 68 to 75 percent without any further change in flexibility.

Originality/value – It has been demonstrated successfully that the current industry rigid spinal implant rod can be modified for flexibility and laser shock peened to increase fatigue strength. This enhancement will enable the use of the implant for longer periods and higher loads; and for surgical processes with and without fusion. This technology can be readily applied to all metals that are certified for human implant applications; thus can be implemented with minimal clinical trials.



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