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  1. Science and Research (Medical Devices)

Solid Mechanics Laboratory

Solid Mechanics Laboratory

Contact

Terry Woods, Ph.D.

Summary

The mechanical durability of materials and medical devices is critical in the development and successful performance of medical devices. We use experimental and computational solid mechanics to investigate engineering issues relevant to existing and new devices and materials. Our ongoing participation with voluntary consensus standards organizations (e.g. American Society for Testing and Materials (ASTM) International and International Organization for Standardization (ISO)) leverages FDA resources to create lasting consensus solutions for regulatory issues. Our research examines traditional engineering materials (e.g., metals and polymers) and biological materials as well as tissue engineered medical products (TEMPs) to study effects of the service environment and manufacturing processes on both initial and long term mechanical performance to advance the safety and effectiveness of medical devices. The results of our work in this area directly support the CDRH mission to protect and promote the public health and assure that patients and providers have timely and continued access to safe, effective, and high-quality medical devices by helping to measure, define, and quantify the effects of manufacturing and processing procedures and the use environment on medical devices. Our research is focused on the following areas:

Experimental and Computational Analysis

Mechanical testing of spinal fusion implants.


Experimental and Computational Analysis

Computational stress analysis simulating ASTM standard for spinal implant testing.


Image of Fatigue testing of cardiac leads

Fatigue testing of cardiac leads.


Corrosion in Medical AlloysCorrosion in Medical Alloys

Pitting and plume seen after corrosion testing in stainless steel wires.

(1) Mechanical Durability of Materials and Medical Devices

  • evaluating the Fatigue-to-Fracture methodology for assessing the fatigue life of cardiovascular medical devices,
  • characterizing the effects of test environment on fatigue, wear, and ion release of commonly implanted metals, and
  • developing a bench test method for evaluating intra-operative spinal cage failures due to impaction.

(2) Medical Device Performance Testing

  • investigating abrasion and wear of metal-on-metal hip implants,
  • characterizing the reverse total shoulder arthroplasty (rTSA) in-vivo motion path and abrasion and wear of rTSA devices.
  • evaluating the penetration resistance of personal protective equipment like gowns, drapes, and gloves to clinically relevant test soils, and
  • developing a test method for evaluating perforation potential of pacemaker and ICD cardiac leads.

(3) Manufacturing and Processing of Materials and Medical Devices

  • investigating the effects of surface area on corrosion susceptibility of nitinol with different surface processing, and
  • studying the effects of parameters including energy source, print orientation and lattice structure on the mechanical behavior of 3D printed metals and absorbable polymers

(4) Computational Solid Mechanical Modeling of Medical Devices

  • predicting mechanical performance of spinal fixation devices,
  • comparing modeled fretting and observed wear in hip implants, and
  • predicting high stressed regions resulting from non-circular deployment configurations in heart valves.

Current funding sources

FDA Critical Path Initiative
FDA Medical Countermeasures Initiative
FDA Office of Women’s Health  

Personnel

FDA Staff:
Terry Woods, Ph.D., Laboratory Leader
Andrew Baumann, Ph.D.
Matthew Di Prima, Ph.D.
Nandini Duraiswamy, Ph.D.
Vivek Palepu, Ph.D.
Daniel Porter, Ph.D.
Matthew Schwerin, B.A.
Shiril Sivan, Ph.D.
Stacey Sullivan, Ph.D.
Oleg Vesnovsky, Ph.D.
Jason Weaver, Ph.D.

External collaborators

Anderson Orthopaedic Research Institutedisclaimer icon
Ansys Incdisclaimer icon
Association for the Advancement of Medical Instrumentation (AAMI)disclaimer icon
Biocoat Inc.disclaimer icon
Boston Scientificdisclaimer icon
Case Western Reserve Universitydisclaimer icon
DePuy Synthes Spinedisclaimer icon
DePuy Synthes Traumadisclaimer icon
Drexel Universitydisclaimer icon
G. Raudisclaimer icon
Growing Spine Foundationdisclaimer icon
Johns Hopkins Applied Physics Laboratorydisclaimer icon
Johns Hopkins Universitydisclaimer icon
MedStar Union Memorial Hospitaldisclaimer icon
Medical Device Testing Services
Medtronicdisclaimer icon
National Institute for Occupational Safety and Health (NIOSH)
University of Georgiadisclaimer icon
University of Maryland at College Parkdisclaimer icon
University of Maryland Baltimore Countydisclaimer icon
University of Ottawadisclaimer icon
University of Texas at Dallasdisclaimer icon
University of Toledodisclaimer icon
Walter Reed National Military Medical Center
Zimmer Biometdisclaimer icon

Resource facilities

Hardware

  • Mechanical load frames suitable for the axial and torsional durability testing of medical devices and materials
  • 3D printers for an array of materials to investigate the rapidly developing area of additive manufacturing
  • MTS Bionix servo-hydraulic axial-torsional load frames (with spine motion capabilities)
  • ElectroForce 3300 axial torsional load frame (TA Instruments)
  • Instron uniaxial load frames
  • HIROX HK-7700 Digital Optical Microscope
  • Princeton Applied Research Model 263A Potentiostat
  • Gamry Interface 1000 Potentiostats
  • Buehler Rockwell hardness tester
  • Buehler micro hardness tester
  • Bruker 3D Profilometer
  • Wire fatigue testers
  • Metallurgical preparation lab (Grinding/polish equipment and Abrasive and diamond saws)
  • Real-time X-ray machine
  • MicroCT 100 imaging and reconstruction system
  • HOTPACK environmental chambers 

Software

  • Computational modeling software (ANSYS and Abaqus)
  • Materialise software (Mimics/3-matics) for CT image reconstruction and design
  • Computational design software (ProE, Solidworks)
     

Relevant standards & guidances

Selected peer-review publications

  1. Marrey, R., Baillargeon, B., Dreher, ML., Weaver, JD., Nagaraja, S., Rebelo, N., and Gong, XY. Validating Fatigue Safety Factor Calculation Methods for Cardiovascular Stentsdisclaimer icon. Journal of Biomechanical Engineering, 2018.
  2. Nagaraja, S., Sullivan, SJL., Stafford, PR., Lucas, AD., and Malkin, E. Impact of Nitinol Stent Surface Processing on In-vivo Nickel Release and Biological Response. Acta Biomater, 2018.
  3. Palepu, V., Helgeson, MD., Molyneaux-Frances, M., and Nagaraja, S. Impact of bone quality on the performance of integrated fixation cage screws. The Spine Journal, 2018.
  4. Sritharan, D., Fathi, P., Weaver, JD., Retta, SM., Wu, C., and Duraiswamy N.Impact of Clinically Relevant Elliptical Deformations on the Damage Patterns of Sagging and Stretched Leaflets in a Bioprosthetic Heart Valve. BMES’s Cardiovascular Engineering and Technology, 2018.
  5. Sullivan, SJ., Stafford, P., Malkin, E., Dreher, ML., and Nagaraja, S. Effects of tissue digestion solutions on surface properties of nitinol stents. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2018.
  6. Weaver, JD., Ramirez, L., Sivan, S., and Di Prima, M. Characterizing fretting damage in different test media for cardiovascular device durability testingdisclaimer icon. Journal of the Mechanical Behavior of Biomedical Materials, 2018.
  7. Palepu, V., Peck, JH., Simon, DD., Helgeson, MD., and Nagaraja, S.Biomechanical Evaluation of an Integrated Fixation Cage during Fatigue Loading: A Human Cadaver Study. The Journal of Neurosurgery - Spine, 2017.
  8. Sullivan, SJ., Madamba, D., Sivan, S., Miyashiro, K., Dreher, ML., Trépanier, C., and Nagaraja, S. The effects of surface processing on in-vivo corrosion of Nitinol stents in a porcine model. Acta Biomaterialia, 2017.
  9. Delfino, J. and Woods, TO. New Developments in Standards for MRI Safety Testing of Medical Devicesdisclaimer icon. Current Radiology Reports, 2016.
  10. Di Prima et al, FDA’s Perspective on Additive Manufacturing of Medical Productsdisclaimer icon. 3D Printing in Medicine, 2016.