Adolescent idiopathic scoliosis (AIS) is a condition that causes spinal curvature in children. Affecting between two and three percent of children aged between ten and 16, AIS is a  disease with conspicuous physical symptoms like the visible deformity of the spine. Current treatments include bracing and surgery, both of which may result in detrimental side effects for patients: Although bracing has been a mainstay of non-operative AIS treatments for almost fifty years, studies suggest that the technique is able only to stop the progression of the spinal curvature, but cannot reduce the deformity. In turn, surgery corrects the curve deformity, but fuses the spine, eliminating its function.

Based on research that suggests AIS is a musculoskeletal expression of a central nervous system disorder, the Fraunhofer Institute for Photonic Microsystems IPMS as part of an European consortium worked more than two years on a complaisant, alternative therapy within the project »StimulAIS«.

The EU funded project contained an alternative AIS treatment, which relies on the muscular electrostimulation of deep paraspinal rotator muscles – a technique known as functional electrical stimulation (FES). The project purpose was to develop and realize a novel device for the treatment of AIS which will be capable not only of stopping progression of the curvature, but also correcting it through micro-electro-stimulation with a programmable stimulating protocol and a real-time stimulus adaptation. Thus, the device has to be small, implantable and also programmable to provide customized treatments for each patient.

Within the consortium Fraunhofer IPMS was responsible for both the development of the electronic components of the implantable device including the reader for data communication as well as the wireless charger and for the development of the operating software. The implantable device’s electronics should provide a defined stimulation pattern to the paraspinal muscles with a given training plan. Therefore, several stimulation schemes can be configured by an embedded software. In order to adapt the stimulation patterns to the state of the paraspinal muscles, the ongoing electromyographic activity must be acquired and subsequently analyzed. The measurement system also contains a motion sensor system which contributes data to the analyzing algorithm, too. The analyzing algorithm is part of the embedded firmware. The device can be controlled from outside wirelessly based on a 13.56MHz near field transponder system which also transmits the recorded data. The battery included in the device can operate up to several weeks. After that, a recharging of the device is necessary, realized by a wireless inductive coupled charging system.

Successful End of StimulAIS project

By the end of the StimulAIS project in January 2015, the entire project consortium has successfully achieved three main results that have been integrated in a working implantable medical device in accordance with EU directives for performing customized treatment of AIS: 1. An implantable device with associated stimulation control software and charger could be realized. 2. Specific surgical instruments were developed in order to implant the electro-stimulation device and for the connection of electrodes to the key muscles. 3. An external operating unit to program the subcutaneous device and to collect bioelectric data of the patient was generated.

The StimulAIS project has received funding from the European Union’s Seventh Framework Programme (FP7) for research, technological development and demonstration under Grant Agreement No 315327. In addition to the Fraunhofer IPMS, five other industrial and research partners participated: Tequir S.L. (Spain), Bentronic (Germany), Synergie Ingeniere Medicale SARL (SYNIMED, France), the Instituto de Biomecánica de Valencia (IBV, Spain) and the Universidad Católica de Valencia (UCV, Spain).