Biomechanical Engineering Expert Discusses Catastrophic Failure of Hip Implant


Biomechanical Engineering Expert WitnessThis biomechanics and kinesiology case involves a critical failure of an orthopedic hip implant in Michigan. The plaintiff was an active woman in her early 60’s who had undergone a hip replacement procedure several months before the date of the incident in question. The woman was an enthusiastic gardener, and was planting flowers in her front yard when she suddenly heard a loud pop and experienced immediate and excruciating pain. The woman presented to the emergency room, where x-rays revealed a fracture in the “head” region of her hip implant. The implant, which had been produced by a major medical device manufacturer, was later subject to a voluntary pinnacle hip recall due to manufacturing defects.

Question(s) For Expert Witness

  • 1. Please discuss your background working with artificial hip implants.
  • 2. Have you previously designed such devices?

Expert Witness Response E-007593

My research group works on tribology (friction/wear/corrosion) of orthopedic implants. I work at the cutting edge of designing new devices, and my work in orthopedics is currently funded by the National Science Foundation and the National Institutes of Health. I also have experience working as an expert witness on several cases related to failure of hip implants. I have worked on a case with simple and multi-modular designs and I am intimately familiar with the failure modes of these devices and interfaces. The question specifies “wear”, which is indeed a significant problem in modular devices. In particular “fretting wear”, caused by reciprocating micro-motion is of primary concern. However, the short case description mentions “fracture” of the head, which may or may not be the result of wear. It could result from a myriad of things. Currently, my research is on designing orthopedic implants. My background is mechanical design, and I am the Chair of the Design and Manufacturing division within the Department of Mechanical Engineering at a major university. I am one of the few people who do rigorous academic research on the design of orthopedic hip implants.

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