Znak Politechniki Warszawskiej

New chamber stapes prosthesis

The scientific project by the employees of WUT’s faculty of Mechatronics received a distinction in the TANGO funding initiative, operated jointly by the National Science Centre (NCN) and the National Centre for Research and Development (NCBR).

The stapes is the smallest and lightest bone in the human body, and is so-called because of its resemblance to a stirrup (Latin: Stapes).It vibrates constantly, transmitting sounds from outer ear to cochlea. In the cochlea, mechanical vibrations are converted into electrical impulses, which are transmitted to the brain via the auditory nerve so that we can hear. Sometimes the stapes stops vibrating. This could, for example, be caused by a disease called otosclerosis. Limitation of vibrations or no vibrations at all leads to significant hearing loss which is a nuisance and causes much discomfort in everyday life. Patients are offered a surgical procedure called stapedotomy, which is performed by creating a small hole (about 0.4-0.6 mm diameter) in the fixed stapes footplate and inserting a tiny piston-like prosthesis (Pic.1).

 

All the currently used prostheses are piston prostheses. The stimulation of the cochlea with piston prosthesis is not ideal. The main problem is that the compressional wave in the perilymphatic liquid is too low/weak. This is due to the fact that the area of the vibrating piston (about 0,2 sq.mm) is 16 times smaller than area of the stapes footplate (about 3,2 sq.mm). Moreover, putting the vibrating piston in the vestibule may cause balance disorder. There is also the possibility that the piston may fall out of the hole, which can lead to perylimphatic liquid loss and cause an inner ear infection. Sometimes it is observed that the piston has stopped moving, resulting in hearing loss..

The above-mentioned problems with piston prosthesis led to questions about improvements in this matter.

In order to answer these questions, an interdisciplinary team of scientists from WUT and the Institute of Physiology and Pathology of Hearing began working together in 2009. Up till 2012, the research was financed by the National Science Centre (NCN). The research results were published in many scientific journals and presented at international conferences. At the same time, the new chamber stapes prosthesis was invented and patented.

Design of the new prosthesis mimics the anatomy of physiological area of the oval window. It has a stiff plate (like the stapes footplate) suspended on a thin, flexible membrane ( like the stapes annular ligament) attached to a chamber filled with fluid ( like the vestibule). The implantation procedure of the new prosthesis is exactly the same as the procedure for the piston prosthesis..

After the basic research, it was time to build a prototype (Pic.2) and check if the new prosthesis functioned properly, as expected. Potomac Photonic company from the US made the first two prototypes. Another few were donated by CAD-MECH Ltd. From Wrocław.

Ms. Magdalena Sołyga from WUT’s Faculty of Electronics and Information Technology made a significant contribution to the creation of the prototype. She is the one responsible for creating the membrane that joins the two stiff parts of the prosthesis. The membrane is a crucial element of the invention as it enables the vibration transmission from the plate to the perylimph fluid.

 

Whilst waiting for the results of the TANGO competition, initial trials of the prototype were conducted in Kajetany Medical centre in January 2015 . Due to inadequate funds for such research at the time, it had to be done through the generosity of many people. One of them was Professor Henryk Skarżyński – the Director of the Institute of Physiology and Pathology of Hearing, who let the researchers use labs in the World Hearing Center. The project was also supported by Prof. Tadeusz Uhla from the AGH University of Science and Technology and Mr. Jakub Żak from EC Test System company in Krakow. They provided a scanning vibrometer PSV400 by Polytec which was operated by two engineers – Mr. Piotr Gawęcki and Mr. Wojciech Paluch. Due to Dr Maciej Mrówka’s engagement and otosurgical skills, the prototype of our scientists was implanted in the temporal bone.

The experimental research confirmed that the new locular stapes prosthesis transmits the vibrations much better than the traditional piston prosthesis available on the market. About one month after the pilot study of the new invention, the National Centre for Research and Development announced the results of TANGO competition.

Dr Monika Kwacz from WUT’s faculty of Mechatronics, the manager of the research commented on the fact that the project achieved a distinction: “We were very pleased to find out that our work was placed high in the ranking of applications and gained a very good final grade. We now have an incentive to continue our research in order to witness the new prosthesis being used in clinical practice".

TANGO is a joint undertaking of the National Science Centre and the National Centre for Science and Development, set up in order to accommodate the needs of research centres and universities seeking implementation of technologies, products and services, and to reinforce cooperation between researchers and entrepreneurs. Actions eligible for funding under the programme include developing concepts for using the results of basic research in the economy, searching for partners interested in bringing these to production, as well as protecting intellectual property rights. Market analyses, industrial research, as well as research and development work will also be subsidized. Another distinguished project from WUT’s Faculty of Material Science and Engineering is entitled: “Applying non-Newtonian fluids in energy absorbing systems”.