Bone-Anchored Hearing Devices

Bone-Anchored Hearing Devices - Sound Vibes

• Definition: Surgically implanted auditory device that transmits sound as vibrations through the skull bone directly to the cochlea, bypassing the outer and middle ear.
• Principle of Osseointegration: A titanium implant integrates with the temporal bone, providing a stable anchor for the external sound processor.
• Direct Bone Conduction (DBC): Sound vibrations are transferred directly to the skull, which then conducts them to the cochlea. This is distinct from air conduction through the ear canal.
• Sound Pathway:
  • External sound processor captures sound.
  • Processor converts sound into vibrations.
  • Vibrations are transmitted through an abutment or magnetic connection to the titanium implant.
  • Implant vibrates the skull and inner ear fluids, stimulating the cochlea.

⭐ BAHDs bypass the outer and middle ear, directly stimulating the cochlea via bone conduction. This is crucial for patients with conductive or mixed hearing loss where conventional aids are unsuitable or ineffective, or for single-sided deafness (SSD).

Bone-Anchored Hearing Devices - Who Gets Wired?

Bone-Anchored Hearing Devices (BAHDs) are indicated for specific types of hearing loss when conventional aids are unsuitable. Candidacy depends on audiological criteria and patient factors.

• Primary Indications:

  • Conductive Hearing Loss (CHL)
  • Mixed Hearing Loss (MHL)
  • Single-Sided Deafness (SSD)

• Audiometric Criteria:

  Indication	Air-Bone Gap (ABG)	Bone Conduction (BC) PTA	Contralateral Ear (SSD)
  CHL	≥30 dB HL	≤45 dB HL	N/A
  MHL	≥30 dB HL	≤55 dB HL	N/A
  SSD (Unilateral Profound SNHL)	N/A	N/A	PTA ≤20 dB HL (Normal)
  (PTA: Pure Tone Average)

• Age Considerations:

  • Surgical implantation: Typically ≥5 years (skull thickness, cooperation).
  • Non-surgical (softband): Infants and younger children.

⭐ Ideal for patients with chronic otitis externa or media, or anatomical malformations (e.g., microtia, atresia, mastoid cavity) where conventional hearing aids are contraindicated or ineffective.

Bone-Anchored Hearing Devices - The Bionic Ear

• Components:
  • Titanium implant: Osseointegrates with skull.
  • Abutment (percutaneous) / Magnetic plate (transcutaneous): Links implant to processor.
  • Sound processor: Captures sound, converts vibrations.

• Types & Comparison:

*   Implant in mastoid.
*   Osseointegration: **3-6 weeks** (children), **3-4 months** (adults) before processor fit.

⭐ Osseointegration, the direct structural and functional connection between living bone and a load-bearing titanium implant surface, is crucial for BAHD success.

Bone-Anchored Hearing Devices - The Full Scoop

Bone-Anchored Hearing Devices (BAHDs), or Bone Conduction Hearing Devices (BCHDs), transmit sound via direct bone conduction to the cochlea. They bypass the outer and middle ear. Primarily indicated for conductive hearing loss, mixed hearing loss, or single-sided deafness (SSD).

• Complications: 📌 SIFT
  • Skin inflammation/infection around abutment
  • Implant extrusion or loss
  • Failure of osseointegration
  • Trauma or Tingling (numbness) at site

⭐ Percutaneous systems generally offer better high-frequency sound transmission but have a higher risk of skin complications compared to transcutaneous systems.

High‑Yield Points - ⚡ Biggest Takeaways

• BAHDs are indicated for conductive hearing loss (CHL), mixed hearing loss (MHL), and single-sided deafness (SSD).
• Sound is transmitted via direct bone conduction, bypassing the external and middle ear.
• Key types include percutaneous (skin-penetrating abutment) and transcutaneous (intact skin).
• Advantages: improved comfort, reduced feedback, and no ear canal occlusion compared to conventional aids.
• Osseointegration of the titanium implant into the mastoid bone is crucial for device stability and function.
• Consider for congenital aural atresia, chronic suppurative otitis media (CSOM), or when conventional aids are contraindicated/ineffective.
• Candidacy requires specific audiometric criteria, including adequate bone conduction thresholds (typically ≤45-65 dB HL).