Objectives: To determine (1) levels on fibrous tissue and bony growth around the ceramic receiver-stimulator of cochlear implants in situ and (2) if these ceramic receiver-stimulators can withstand a tractive force of 5 N without displacing.
Methods: During revision surgery, we measured the extent of the fibrous tissue and bone growth around the receiver-stimulators in 13 subjects. After completely exposing the receiver-stimulator, we measured the tractive force it could withstand without displacing. The tractive force was gradually increased until either displacement or a force of approximately 5.5 N was reached.
Results: In 6 out of 10 subjects the receiver-stimulator did not displace when up to 5 N of tractive force was applied. Three subjects could not be evaluated. Statistical analysis was not possible due to the small sample size; however, we found no correlation between the degree of bone growth around the receiver-stimulator and (1) the length of time the implants remained in situ before revision or (2) the tractive force a receiver-stimulator could withstand without displacing. Discussion As bone growth around the receiver-stimulator is often limited, even years after implantation, it might therefore only play a minor role in preventing displacement. In contrast, fibrous tissue encapsulation of the implant bed of the receiver-stimulator may be the key stabilizing factor. In any case, when completely exposed, the 6 out of 10 receiver-stimulators could still withstand a tractive force of 5 N (calculated force generated by magnetic resonance imaging (MRI) with 1.5 T) without displacing.
Conclusions: During MRI, it is strongly recommended to secure ceramic receiver-stimulators with an external pressure bandage in order to minimize risk and possible user discomfort.
Keywords: Bone growth; Cochlear implant fixation; Fibrous tissue growth; Magnetic resonance imaging.