Can keratinocytes cause failure of osseointegration?

Bone-anchored hearing aids are well established, implanted devices. We present two patients who suffered mixed hearing loss and who underwent titanium implant placement in the temporal bone to enable attachment of bone-anchored hearing aids. Osseointegration is necessary for such implants to function. We report these two cases to highlight how such osseointegration may be disrupted. Attached tissue from the explanted or removed titanium implants was examined by transmission electron microscopy and histopathological analysis. Attached tissue from both implants showed the presence of keratinocytes at the titanium implant and living bone interface. This was confirmed by histopathological analysis. In one case, there was frank keratinocyte proliferation, which had led to osseointegration failure; in the other case, such proliferation was present but not so advanced. These findings suggest that, in the cases reported, keratinocytes implanted between the titanium and the living bone, leading to disruption of osseointegration.