Significant progress in bionic reconstruction of limb functions

( Image: Depositphotos)
( Image: Depositphotos)

Bionic reconstruction, in which functionless limbs are replaced by mechatronic limbs, can restore mobility and quality of life to accident patients. However, the high-resolution transmission of information from the brain to the machine remains a demanding challenge. An interdisciplinary research team led by Vlad Tereshenko and Oskar Aszmann from MedUni Vienna’s Department of Plastic, Reconstructive and Aesthetic Surgery has now made further significant progress as part of a study. In their study, recently published in the journal "Science Advances", the scientists showed that skeletal muscles can play an important role as a high-resolution interface for neuronal information from the spinal cord. These new findings can significantly improve the control of bionic prostheses.

"The most remarkable discovery of our study is that a skeletal muscle can be reinnervated by a number of axons, i.e. nerve processes, that is more than 15 times higher than its original physiological innervation after a high-capacity nerve rerouting," study leader Oskar Aszmann goes into detail. Physiological innervation refers to the supply of skeletal muscles with nerve fibres to control muscle movements. This indicates the extensive interface capabilities of skeletal muscles to unfold neuronal information from the spinal cord and make it available for the control of a prosthesis.

In addition, surgical rerouting of different nerves has redefined the molecular profile of muscle fibre types, indicating changes in muscle physiology. This implies that surgically rerouting different nerves can load the target muscle with a plethora of biological signals and orchestrate its contractile properties.

Novel human-machine interface explored

"These results establish a link between the neuronal capacity of the donor nerve and the number of reinnervated motor axons, which is crucial for the development of novel human-machine interfaces," says first author Vlad Tereshenko, summarising the enormous relevance of the study for those patients for whom biological hand replantations or transplants are not possible after severe nerve injuries.

In their study, the researchers demonstrated the remarkable ability of skeletal muscles to act as biological amplifiers for neuronal information from the spinal cord and to control bionic prostheses. "The neural signals can now be decoded and mapped to motor commands in a high-resolution manner thanks to advances in bioengineering and machine learning to provide a reliable biological interface for high-precision control of a bionic prosthesis," the study authors said.

World leader in bionic reconstruction

MedUni Vienna, with the team led by Oskar Aszmann from the Department of Plastic and Reconstructive Surgery, has been the world’s leading innovator in bionic reconstruction since 2009. In the first sensational case in 2011, electrician Patrick Mayrhofer received a "bionic hand" after he was caught in an electrical circuit while working and his hand became non-functional. The Clinical Laboratory for Bionic Limb Reconstruction was opened at MedUni Vienna in 2019 to drive forward research into and improvement of bionic reconstructions.

Publication: Science Advances

Peripheral Neural Interfaces: Skeletal Muscles are Hyper-Reinnervated According to the Axonal Capacity of the Surgically Rewired Nerves. High-Information Transfer Peripheral Interfaces;
Vlad Tereshenko, Dominik C. Dotzauer, Martin Schmoll, Leopold Harnoncourt, Genova Carrero Rojas, Lisa Gfrerer, Kyle R. Eberlin, William G. Austen Jr, Roland Blumer, Dario Farina, Oskar C. Aszmann;
https://dx.doi.org/10.1126/scia­dv.adj3872