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Advanced FEA Stress Analysis of Medical Instruments and Devices using Femap, NX Nastran and LS-DYNA

Medical device (aspiration tip) for bone marrow extraction for endoscopic surgery




Predictive Engineering has been involved with the analysis of medical devices since 1995 with its first work on an endoscopic surgical stapler to pedicle screws to all-plastic medical device to our current work with micro-cables and filar wrapped tubes for robotic surgery applications.  In all cases, these projects were benchmarked against experimental results and shown to be in tight correlation. 

Complex analysis demands were only part of the challenge for these projects since the medical industry also requires extensive documentation and quality assurance that the models are built per specification.  Additionally, in several cases the clients required that an accuracy assessment be performed prior to the correlation with experimental results.  It was an interesting and enlightening twist that a prediction was required of the model’s precision prior to the divulgement of the experimental data.

The projects presented within this Case Study represents a small portion of the total work done over the years but illustrates some of the most complex modeling challenges facing the medical industry with multi-component systems loaded to their failure point and that of elegant numerical simulations where stress waves are propagated through visco-elastic medium (acoustic radiation force imaging).

FEA Simulation of Medical Devices using Advanced Nonlinear Analysis

  • Elastic-plastic nonlinear analysis of aspiration tip of bone marrow extraction tool
  • Filar wrapped Nitinol tube for aspiration of bone marrow during surgery
  • All plastic medical snap-fit device
  • Locking orthopedic pedicle screw of spinal surgery
  • Endoscopic surgical stapling anvil
Figure 1: Flexible-shaft medical tool for bone marrow extraction with filar (wire) strands wrapped around a flexible Nitinol tube to provide torsion stiffness while provided an extraction path for the extraction product.
Figure 2: FEA simulation model of titanium locking pedicle screw for spinal surgery as analyzed for its locking capability as a function of interference fit and friction coefficient
Figure 3: Acoustic radiation force impulse (ARFI) imaging is a recently developed technology for making strain images of human tissue and organs.  A FEA simulation was developed to model the ultrasonic radiation in pseudo human tissue.
Figure 4: All plastic medical snap-fit design using several different grades of plastics
Figure 5: FEA Simulation of endoscopic surgical stapling anvil for ultimate load determination