Magnetic Coupling Slippage Detection in Implantable Medical Devices
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Solution Overview
Problem
Implantable medical devices that utilize magnetic coupling for length adjustment often experience 'stalled distraction' due to slippage between the internal and external magnetic fields, leading to inaccurate length measurements.
Innovation Solution
A device with an external magnet and induction coil detects slippage by measuring varying frequency components of the voltage waveform across the induction coil, indicating perturbations that signify magnetic coupling slippage, and includes a detection circuit to alert the user.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If magnetic coupling is used for non-invasive length adjustment, then ease of operation is improved, but reliability deteriorates due to slippage between internal and external magnetic fields
Solution Approach 1:
The patent employs feedback by continuously monitoring the magnetic coupling between internal and external magnets through induction coils. When slippage is detected (through changes in induced voltage frequency components), the system provides feedback to alert the user or adjust the magnetic field strength, ensuring reliable operation while maintaining ease of use.
Solution Approach 2:
The patent introduces an intermediary detection system (induction coils and detection circuits) between the internal and external magnetic fields. This intermediary monitors the coupling status without interfering with the magnetic interaction, allowing reliable detection of slippage while preserving the non-invasive magnetic coupling mechanism.
2Measurement precision
If external magnetic field rotation is used to measure implant length, then measurement precision is improved, but reliability deteriorates when internal magnet fails to rotate in correspondence
Solution Approach 1:
The system uses feedback through induction coils to monitor the actual rotation of the internal magnet. By comparing the expected rotation (based on external magnet rotation) with the actual rotation (detected through induced voltage), the system can identify discrepancies and correct measurement errors, maintaining precision even when slippage occurs.
Solution Approach 2:
The patent replaces direct mechanical coupling measurement with electromagnetic induction for detection. Instead of relying solely on mechanical rotation correspondence, the system uses induction coils to detect the actual magnetic field changes, providing a more reliable measurement method that is not subject to mechanical slippage.
3Strength
If compression force is increased to stabilize the implant, then strength is improved, but magnetic coupling reliability deteriorates due to exceeded distraction force
Solution Approach 1:
The patent applies dynamics by making the magnetic field strength adjustable and responsive to loading conditions. When compression force increases, the system can dynamically adjust the external magnetic field strength or rotation speed to maintain adequate distraction force, ensuring reliable coupling even under varying compression loads.
Solution Approach 2:
The system uses feedback to monitor the magnetic coupling status under compression. When slippage is detected through the induction coils, the system can increase the external magnetic field strength or adjust rotation parameters to compensate for the increased compression force, maintaining reliable coupling while preserving implant stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Accurately detects slippage in magnetic coupling, preventing inaccurate length measurements and ensuring precise tracking of implantable medical device length adjustments.
Implementation Method 1
an induction coil disposed external to the subject and between the at least one external magnet and the implanted medical device, and a detection circuit operatively coupled to the induction coil and configured to detect slippage between the rotational orientation of the magnet of the implanted device and the externally applied magnetic field based at least in part on the measured varying frequency components of the voltage waveform across the induction coil
Data Source
AI summary
A device for the detection of slippage of magnetic coupling between an implanted medical device having a magnet and an externally applied magnetic field includes at least one external magnet configured to apply the externally applied magnetic field, an induction coil disposed external to the subject and between the at least one external magnet and the implanted medical device, and a detection circuit operatively coupled to the induction coil and configured to detect slippage between the rotational orientation of the magnet of the implanted device and the externally applied magnetic field based at least in part on the varying frequency components of the voltage waveform across the induction coil.