An overview of different systems: the bone-anchored hearing aid.

In the past 30 years, a large amount of clinical and audiological research on bone conduction hearing devices has been performed. In this review, we give a brief history of the developments in indications, surgical techniques and sound processors with respect to implantable bone conduction devices like the bone-anchored hearing aid or Baha. Starting with the use of Baha in patients with bilateral conductive or mixed hearing loss (HL), the indications for such devices have been extended to patients with unilateral HL, children and moderate mentally retarded patients. Bilateral fitting has been shown to be beneficial in restoring binaural hearing in patients with bilateral acquired or congenital conductive HL. In addition, the surgical techniques used to implant the titanium fixture for Baha application have been modified and further developed to reach two main goals: (a) optimal osseointegration, and (b) preparation of the implant site to minimize the occurrence of soft tissue reactions. Currently, the most used techniques are the pedicled skin flap, dermatome and linear incision techniques. Several generations of the Baha(®) sound processor have been developed by Cochlear(TM) to provide sufficient amplification in different hearing situations. Improvements in sound quality, aesthetics and handling have been major points of interest. The Baha sound processors most often used today are the Baha(®) Divino, the Baha(®) Intenso and the Baha(®) Cordelle. Recently, the more flexible Baha(®) BP100 sound processor was launched.