Optimal Retention Force of Audio Processor Magnets

Background:

The actual retention force in auditory implants can be modified and influences the comfort of the user. Small forces will loosen the connection. Large forces induce pressure to the skin and the risk of skin irritation and pain. So far, there are no guidelines specifying the optimal retention force.

Methods:

In an experimental setup the retention forces of all available magnet combinations were measured as function of the distance between the magnet pairs. All combinations of Advanced Bionic, Cochlear, and Med-El cochlear implant and implantable hearing system magnets were used. Retention force was measured with a force meter and the labview software after changing the distance between the magnet pairs by an increment motor. The distance-force functions were approximated by a polynomial fit. Clinical retention forces were measured in 100 patients with Cochlear Implants or implantable hearing devices with a thin force sensor foil. Skin status was determined by visual inspection and a patient’s pain, comfort and discomfort was evaluated by a questionnaire.

Results:

We report the distributions of skin status as function of the actual retention force applied to the patients’ skin. We give an advice for the optimal retention force.

Conclusion:

Optimal retention force is a compromise between the risks of skin irritation and audio processor loss. By means of the fitting function the optimal magnet type can easily be calculated for every patient after measuring the actual retention force.