Surgical pathology of middle ear implants

Area of Science:

• Otolaryngology
• Biomaterials Science
• Histopathology

Background:

• Middle ear implants are used to address hearing loss.
• Revision surgeries are necessary due to device failure or persistent hearing issues.
• Understanding the long-term biological response to implant materials is crucial.

Purpose of the Study:

• To histologically evaluate explanted middle ear implants after revision surgery.
• To assess the biological integration and degradation of various implant materials.
• To correlate histological findings with clinical outcomes like disease control and hearing preservation.

Main Methods:

• Histological examination of 25 explanted middle ear implants (bone autografts, cartilage grafts, TORP prostheses, polyethylene tubes).
• Macroscopic evaluation of graft rigidity and microscopic assessment of cellular infiltration and material changes.
• Analysis of bone and cartilage viability and host tissue response within implant porous spaces.

Main Results:

• Ossicular and cortical bone autografts demonstrated creeping substitution with vitalized bone (0-83%), independent of implantation duration.
• Cartilage grafts exhibited reduced rigidity, though chondrocyte survival was high in most cases.
• TORP prostheses showed significant foreign body giant cell invasion and fibrous replacement of plastic material in one long-term implant.
• Polyethylene tubes displayed intraluminal foreign body reactions and new bone formation.

Conclusions:

• Bone autografts show good integration via creeping substitution.
• Cartilage grafts may compromise structural integrity over time.
• Porous TORP prostheses and polyethylene implants elicit foreign body responses and bone deposition, potentially impacting long-term function.