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Reducing damage to the inner ear during cochlear implant surgery

Filip Hrnčiřík is a PhD student in Professor Manohar Bance’s lab at the University of Cambridge. His studentship began in 2019. We’re funding this PhD studentship in partnership with Cochlear Ltd. 


Cochlear implants allow profoundly deaf people to hear by converting sound into electrical signals that the brain can interpret.

Cochlear implants contain a long, thin, plastic (usually silicone) strip with electrodes embedded into it (called an “array”). This array is inserted into the inner ear (cochlea) through manual surgery. The electrode array stimulates the hearing nerve with electrical signals in response to sound. These signals are then transmitted along the hearing nerve to the brain.  

Surgical insertion of cochlear implant arrays into the cochlea can result in trauma to the tissue, often destroying any remaining natural hearing the person has. Minimising trauma during surgery would:

  • preserve more of a person’s residual hearing
  • allow the implant to perform better
  • and ultimately let the person to hear better. 

Arrays from different cochlear implant manufacturers come in a limited number of fixed lengths and properties (such as stiffness and shape), but the size and shape of the cochlea varies a lot from person to person.

Putting the wrong array in the wrong cochlea is more likely to cause damage and destroy remaining hearing than one that fits better. But we know very little about how much the shape and size of the cochlea can vary from person-to-person, and how important these differences are to which array is inserted. This makes it difficult to predict what damage it might cause during surgery. 


This project aims to understand which cochlear implant array features are best suited to which cochlear shapes.  

To do this, Filip will first take very detailed CT scans of human cochleas and document the range of variation in their shape and size. They’ll then use 3D printing techniques to print plastic cochlear models based on these scans, creating plastic models of the more unusual shapes and sizes as well as the more common ones.  

The research team will make their own implant arrays out of silicone, changing the shape, size, and stiffness of the arrays. They’ll then insert these arrays into human cochleas (post-mortem). By measuring the force needed to insert the array, they will calculate how much friction is generated as the array rubs against the inside of the cochlea – more friction is thought to cause more damage.

The researchers will aim to produce plastic cochleas that give similar friction readings to real cochleas. They’ll then test different arrays in the various plastic cochleas to understand which arrays fit best in which types of cochleas. 


This research will provide important information about how the anatomy of the cochlea interacts with the implant array during surgery. This will help surgeons select the best implant for each patient, to reduce trauma and preserve as much of their remaining natural hearing as possible. This will improve hearing outcomes as people can hear better when they use a combination of natural and electrical hearing.  

Currently, only 5% of people eligible for a cochlear implant actually choose to have one. The low uptake is largely due to patients’ concerns that the benefits of an implant don’t outweigh the risk of losing their remaining natural hearing.

The higher standard of implantation that may result from this project could lead to eligibility criteria being relaxed, meaning more people will be able to access and benefit from this life-changing technology.

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