Skin flap thickness in cochlear implant patients - a prospective study

The thickness and quality of the skin overlying a cochlear implant is important for its integrity. It should be thick enough to protect the implant and prevent flap breakdown yet should not be so thick that it impedes the electronic signal or causes difficulty wearing the coil because of loss of the magnetic coupling. The principle of this study was to devise a method to assess the thickness of skin over a cochlear implant receiver stimulator package and prospectively measure this thickness during the first year following surgery. All patients studied were implanted with MED-EL COMBI 40+ implants. The first cohort consisted of 35 adults; the second 23 children. Various methods of measurement were assessed. In this study the principle of the Hall Effect electrode was used to measure the magnetic flux density of the magnet within the receiver stimulator package. Following standardization, results showed that skin thickness significantly thinned in the adult group before stabilizing. This was less obvious in children, probably due to the effect of the skin thickening as the child grows. Knowledge of skin thickness has implications relating to the functioning of an implant and avoiding potential flap related complications.