Advanced corrosion bioreactor testing apparatus
Inventors
Ahn, Jeongmin • Welles, Thomas
Assignees
Publication Number
US-12298224-B2
Publication Date
2025-05-13
Expiration Date
2043-03-10
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Abstract
A testing apparatus for evaluating a medical implant for electric potential oscillations that lead to corrosion. The testing apparatus uses a uniaxial load device having a mounting base for accepting a medical implant and orienting the implant along a predetermined axis, a support plate positioned under the uniaxial load device and moveable to apply a force to the implant, a load cell positioned above the mounting plate to measure the force applied to the implant, and a set of differential variable reluctance transducers positioned to measure motion of the implant. A chamber encloses the uniaxial load device so that the implant can be submerged in a fluid replicating human synovial fluid. A faraday cage surrounds the chamber for isolation from environmental electromagnetic radiation. An array of near field antenna are positioned circumferentially around the chamber and driven by a multi-frequency generator.
Core Innovation
The invention is a testing apparatus specifically designed to simulate the in vivo environment experienced by a modular hip implant, particularly at the taper junction where corrosion can occur. The apparatus features a uniaxial load device with a mounting base for securing and orienting the implant along a predetermined axis, a moveable support plate to apply force, a load cell for measuring applied loads, and differential variable reluctance transducers to detect implant motion. These components are enclosed in a chamber that holds a fluid replicating human synovial fluid, and the implant is submerged for testing.
To further recreate physiologic conditions, a Faraday cage encompasses the chamber for electromagnetic isolation. An array of near field antennas, positioned circumferentially around the chamber, is coupled to a multi-frequency generator to introduce controlled electric potential oscillations. This setup allows for the targeted investigation of how electrical fields contribute to the corrosion processes observed in vivo, by exposing the implant to both mechanical forces and varying electromagnetic environments similar to those inside the human body.
The problem addressed by the invention is the inability of current research and testing apparatus to effectively replicate or predict the complex corrosion mechanisms observed in failed orthopedic implants, especially those involving electric potential oscillations in addition to mechanical influences. Existing methods focus predominantly on tribocorrosion and mechanically assisted crevice corrosion but have not successfully reproduced the type and degree of corrosion found in vivo. The present invention provides a comprehensive system to separately and simultaneously investigate these mechanisms, offering a more complete evaluation of implant failure modes.
Claims Coverage
There are two independent claims, each focusing on key inventive features related to the testing apparatus and the method for testing a medical implant.
Testing apparatus for simulating in vivo corrosion of medical implants
The apparatus incorporates: - A uniaxial load device with a mounting base for orienting the implant, a moveable support plate for applying force, a load cell for force measurement, and a set of differential variable reluctance transducers for measuring implant motion. - A chamber enclosing the uniaxial load device that holds a fluid to completely submerge the implant. - An array of near field antennas placed circumferentially around the chamber. - A Faraday cage that surrounds the chamber, electrically isolating the device from environmental electromagnetic radiation. - A multi-frequency generator connected to the antenna array for generating controlled electric fields.
Method for testing a medical implant under simulated physiologic and electromagnetic conditions
The method includes the steps of: 1. Positioning the medical implant in a uniaxial load device that orients it along a predetermined axis. 2. Applying force to the implant with a moveable support plate. 3. Measuring both force (using a load cell) and motion (using differential variable reluctance transducers). 4. Enclosing the implant in a chamber to submerge it in fluid. 5. Energizing an array of near field antennas around the chamber with a multi-frequency generator. 6. Isolating the assembly from environmental electromagnetic radiation via a Faraday cage.
The inventive features focus on a combined mechanical, chemical, and electromagnetic simulation system for accurately replicating in vivo corrosion factors affecting medical implants, as well as a method for implementing this simulation in a controlled laboratory setting.
Stated Advantages
Allows for independent and simultaneous investigation of electrically driven corrosion mechanisms alongside traditional fretting and crevice corrosion.
Enables realistic simulation of physiologic and electromagnetic conditions experienced by implants in the human body.
Supports direct comparison to recovered implants due to utilization of actual modular junctions and accurate orientation to human physiology.
Facilitates identification and classification of corrosion products depending on experimental electromagnetic parameters, supporting detailed post hoc analyses.
Documented Applications
Evaluation of modular hip implants for susceptibility to corrosion and failure under simulated physiological and electromagnetic conditions.
Classification and study of electrochemical reactions and corrosion products generated on biomedical metal alloys in the presence of static and oscillating electric fields.
Testing new medical implant designs for potential failure due to corrosion mechanisms replicating those found in the human body.
Potential adoption across the medical implant industry for the comprehensive evaluation of implants.
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