Three-Dimensional Force Profile During Cochlear Implantation Depends on Individual Geometry and Insertion Trauma

Area of Science:

• Otolaryngology
• Biomechanical Engineering
• Medical Imaging

Background:

• Cochlear implantation aims to preserve acoustic hearing, necessitating atraumatic electrode insertion.
• Understanding cochlear geometry's impact on insertion forces is crucial for improving surgical techniques and reducing intracochlear trauma.

Purpose of the Study:

• To investigate the relationship between cochlear geometry, electrode insertion forces, and intracochlear trauma.
• To correlate three-dimensional (3D) force profiles with micro-CT imaging of insertion trauma.

Main Methods:

• Utilized 10 fresh-frozen human temporal bones, dissecting the inner ear.
• Employed a 3D force measurement system to record insertion forces (2 μN sensitivity) of a lateral wall electrode array.
• Analyzed intracochlear trauma using micro-computed tomography (micro-CT) and correlated findings with insertion videos.

Main Results:

• Found a correlation between 3D intracochlear force profiles and micro-CT detected trauma.
• Insertion angle and cochlear geometry significantly influenced electrode insertion forces and trauma.
• Trauma frequently occurred within the first 180°, marked by electrode buckling and spiral ligament rupturing.

Conclusions:

• A combined 3D force measurement and micro-CT system effectively characterizes CI electrode mechanical behavior and insertion trauma.
• Intracochlear trauma is associated with abrupt force direction changes rather than solely high force amplitudes.