Are suspensory ligaments important for middle ear reconstruction?

Area of Science:

• Biomedical Engineering
• Otolaryngology
• Biomechanics

Background:

• Middle ear prostheses are advancing with 3D printing for personalized reconstructions.
• Understanding the role of middle ear ligaments is crucial for optimizing prostheses design.
• Previous research indicated minimal impact of ligaments on sound transmission, contradicting anatomical assumptions.

Purpose of the Study:

• To investigate the functional role of middle ear ligaments in sound transmission.
• To determine the effect of severing specific ligaments on hearing sensitivity and ossicular chain position.
• To inform the design of three-ossicle prostheses for middle ear reconstruction.

Main Methods:

• Gerbil models were used to study the posterior incudal ligament and anterior mallear process.
• Ligamentous attachments were severed, and subsequent changes in hearing sensitivity were measured.
• Synchrotron microtomography imaging was employed to visualize the ossicular chain's position before and after ligament severance.

Main Results:

• Severing both the posterior incudal ligament and anterior mallear process resulted in a significant hearing sensitivity threshold change of approximately 20 dB across a wide frequency range.
• 3D renderings revealed a noticeable shift in the ossicular chain's position following ligament severance.
• These findings contradict previous studies suggesting a minimal role for these ligaments.

Conclusions:

• Middle ear ligaments, specifically the posterior incudal ligament and anterior mallear process, play a critical role in sound transmission.
• Impairment of sound transmission occurs only when both mallear and incudal ligaments are severed.
• The results have direct implications for middle ear reconstructive surgery and the development of advanced 3D-printed prostheses.