It’s a story full of chance discoveries. The first of these would have been better made in a different way, as like so many technological innovations it originated during the war. Shipwrecked sailors swimming near exploding water explosives died mysteriously, without any external injuries. Post-mortems revealed that their lung tissue had been ruptured. Since then, we have known that strong mechanical forces are released when a sound wave passes from one medium (water) to another (the body).

It wasn’t long before this phenomenon was specifically researched. Doctors and aerospace physicists worked together and developed a device that converted the destructive power of sound waves in the body into something useful: the world’s first kidney stone crusher. In the 1980s, it revolutionised urology. It was now possible to break up even large kidney stones within the patient’s body without the need for a major surgical incision. Even today, when only two small incisions are needed instead of an incision across the abdomen, many patients appreciate the fast, anaesthetic-free treatment. In countries with a less developed healthcare system, removal by “shock wave” is still standard.

It is a destructive procedure that allowed the extracorporeal shock wave to find its way into medicine. However, the next chance discovery was soon to show that it can do more than just shatter. By documenting all the side effects of the new treatment, it became clear that the shock wave stimulates the healing of bone fractures far beyond the extent of normal healing.

The fact that Austria is now a world leader in the treatment of non-healing bone fractures is thanks to the initiative of Wolfgang Schaden. The former senior physician at the Vienna Trauma Centre in Meidling is regarded as a pioneer of shock wave research in traumatology. His pioneering research at the Ludwig Boltzmann Institute of Traumatology and the AUVA led to the founding of the European and later International Society for Extracorporeal Shockwave Therapy (ISMST).

Shockwave treatment is already routine in the AUVA accident hospitals. It is used as a preventative measure for particularly complicated fractures that are expected to fail to heal. Years of experience have shown that the success rate of shockwave treatment is comparable to reconstructive surgery, with fewer complications and only 10% of the costs. For AUVA trauma surgeons, there is therefore no question that shock waves must be the treatment of first choice. It is now also used to treat damage to nerves and tendons.

But how does it actually work? For a long time, it was assumed that the regenerative effects of the shock wave were linked to many microscopic injuries that stimulate healing. However, there was never any proof of these microtraumas. The assumption probably stemmed more from the destructive reputation of the shock wave, an echo of its use as a disintegrator. When Dr Schaden observed that the shock wave also helped with wound healing disorders, the theory of micro-injuries was finally outdated for him.

Studies at the LBI Trauma, the University of Applied Sciences Technikum Wien and the Medical University of Innsbruck describe various cellular effects of the shock wave that could explain its healing properties. In Innsbruck, for example, it was observed on heart muscle cells that the treatment shears off small vesicles on the cell surface, which trigger regenerative effects as a messenger substance – in neighbouring cells and even beyond the original tissue. In this way, stem cells can be recruited from the bone marrow, for example, which then implant themselves where the signal was emitted. The shock wave thus triggers a kind of stem cell therapy in the body.

So we are getting closer to unravelling the last secrets of the shock wave. Despite all the praise, however, it should also be noted that one hurdle has not yet been overcome. In every regenerative field of application, there remains a group of patients who do not respond to the treatment, so-called “non-responders”. This is a phenomenon that is known from many cell biology therapies and reflects the enormous complexity of the body as a system of many living units. It has not yet been possible to explain what makes people non-responders or whether changes in energy, frequency, duration or other parameters would not enable a successful therapy. Science is far from at the end of its tether. And it never tires of testing new applications.

A particularly spectacular study took place in 2023 at the Medical University of Innsbruck under the direction of Priv.Doz. Dr Johannes Holfeld. At the end of bypass operations, while the patients were still attached to the heart-lung machine under deep anaesthesia, their beating heart muscle was treated with a series of shockwave impulses. Subsequently, cardiac output was measured in a blinded fashion. This means that the examining doctors did not know whether the patients had received the treatment or not. The result among those treated was a dramatic improvement in performance following the procedure. The study was eventually terminated prematurely in consultation with the ethics committee. They did not want to deprive the patients who belonged to the untreated comparison group of the real treatment.