Biocompatibility of clinically applied hydroxylapatite ceramic.

Area of Science:

• Biomaterials Science
• Otolaryngology
• Tissue Engineering

Background:

• Hydroxylapatite (HA) is a synthetic bioceramic used in otologic implants.
• Assessing the long-term biocompatibility and integration of HA prostheses is crucial for clinical success.

Purpose of the Study:

• To evaluate the biocompatibility and integration of porous canal wall and dense incus hydroxylapatite prostheses in human patients.
• To compare the performance of HA prostheses in humans with findings from animal experiments.

Main Methods:

• Analysis of 15 retrieved hydroxylapatite prostheses (11 canal wall, 4 incus) implanted for 4-40 months.
• Utilized light microscopy, scanning electron microscopy, transmission electron microscopy, and x-ray microanalysis.
• Compared retrieved human implants with data from experimental acute infections in rat middle ear models.

Main Results:

• Hydroxylapatite prostheses demonstrated favorable integration, epithelialization, and fibrous tissue coverage, consistent with animal studies.
• Biodegradation patterns in humans generally mirrored those observed in experimental settings.
• Chronic infections in human subjects elicited more severe tissue reactions compared to acute infections in rat models.
• One canal wall prosthesis exhibited trace element accumulation within phagocytic cells.

Conclusions:

• Clinically applied hydroxylapatite prostheses exhibit good biocompatibility and integration in the human ear.
• While generally comparable to animal models, chronic infections present a more significant challenge in human otologic applications.
• Further investigation into trace element accumulation in phagocytes may be warranted.