Sleeping implant in the temporal bone: report of a case with 20-year follow-up

There is limited knowledge of the long-term fate of "sleeping" or nonloaded implants in the temporal bone.

This article describes the fate of a fixture installed in the temporal bone that remained unloaded for 20 years.

A 25-year-old male with hemifacial microsomia had three osseointegrated implants installed for an auricular episthesis and bone-anchored hearing aid (BAHA) in the left temporal bone in 1988. Two of the implants for the ear episthesis were activated the same year, but the fixture for the hearing aid was not uncovered until 2008. When the patient experienced hearing problems at his office, he wanted to reactivate the sleeping implant. An audiogram showed a maximum conductive hearing loss with good preserved cochlear function. Before reactivation, an Accuitomo three-dimensional, cone beam computed tomography was performed. Resonance frequency analysis (RFA) using the Ostell technique was done when the implant was uncovered.

Preoperative x-ray investigation showed the sleeping implant to be well integrated in the temporal bone, covered with 1 mm bone, and with no signs of resorption. Geometric measurements correlating to the two loaded implants showed the sleeping implant to be positioned too close to these to be able to anchor a BAHA without interference with the episthesis. Surgical exploration was done to analyze the implant. The clinical status correlated well to that diagnosed from the x-ray investigation. RFA revealed the implant to be well integrated. A new fixture and abutment for BAHA was installed in the temporal line and activated 2 months after surgery. The patient is today supplied with a BAHA.

It seems possible to use sleeping implants in the temporal bone even 20 years after installation.