Restoration of hearing by inner ear prosthesis

Weinheim, August 21, 2014. When hearing aids bring no benefits or no longer help, cochlear implants have enabled people with severe or complete hearing loss to access the world of hearing for the past 30 years. The internationally active Freudenberg Group supplies several types of precision tubes and moldings for these implants. The inner ear prosthesis converts sound into electrical signals which stimulate the auditory nerve in the inner ear (cochlea). This allows people to perceive speech and other sounds again. In Germany, about 30,000 people are equipped with a device of this type and the number is growing. Solutions for medical technology, which are produced by the Helix Medical Business Group, have a long tradition at Freudenberg and a high priority within the Group. “The increased longevity of people combined with growth in the world population will have a marked effect on the health market,” says Dr. Mohsen Sohi, Speaker of the Board of Management of the Freudenberg Group. “We can make a valuable contribution here because our materials competence and product solutions are in demand in this market.”

The cochlea is located in the inner ear and functions as an internal microphone. In the case of many hearing impairments, the cochlea does not function at all or its function is highly restricted. In such cases, the amplification provided by hearing aids is insufficient for the people affected to understand the spoken word. Here, a cochlear implant may bring benefits, provided that the auditory nerve is intact.

The cochlear implant is a prosthesis that replaces the inner ear and is inserted into the cochlea. The device consists of a microphone, a transmitter, a speech processor and the implant itself with the electrode array. The microphone, transmitter and speech processor are worn externally on the body. The microphone captures incoming sound waves and transfers them to the speech processor. This processor converts the sound waves into electric pulses and forwards them to the transmitter. The transmitter conveys these signals to the electrodes in the cochlea, which then electrically stimulate the various sections of the auditory nerve. The nerve carries the stimulation patterns to the brain, where the complete hearing experience is created.

High functionality within a very small space

These implants call for biocompatible materials and high-precision manufacturing processes. Freudenberg is the first manufacturer to use an innovative process for precision liquid silicone molding that also meets the requirements for microscopically small implants. “With our HelixMicro technology, we can produce micro-implants with a weight of less than 0.001 grams. And we can extrude tubes with diameters as small as 0.2 millimeters,” Lars Gerding, Technology Director at Helix Medical, reports.

HelixMicro products are used in a wide variety of medical devices including pacemakers, port systems and cochlear implants. They can be combined with a large number of application-specific additional features to form individually tailored solutions. “Freudenberg is working continuously on individual medical technology solutions for the benefit of patients throughout the world,” says Dr. Jörg Schneewind, President and CEO of the Helix Medical Business Group.

In cochlear implants, the Freudenberg components ensure that the individual parts of the device are fixed in place and the prosthesis is effectively sealed. The silicone tubes have a diameter of only 0.2 millimeters. The precision moldings are only a few millimeters in size and their shape is extremely complex. As a result of the extremely long service life of the implants, regular replacement, as in the case of other implants, is not needed.

Bright prospects for extremely high precision

Treatment with cochlear implants is well established in modern industrialized nations. In Germany, where these devices have been used for more than 30 years, about 30,000 people now live with one or even two cochlear implants. Every year, some 3,000 new patients are treated with a cochlear implant and the number is growing. The insertion of these devices calls for very high precision, which is why the operations are carried out with computer and robot support. Nowadays, the operation, which is carried out under general anesthetic, is a routine intervention. According to the German Medical Technology Association, Germany is now one of the world’s leading locations for micro-systems in medicine.