Calculation methods have not yet gained as much acceptance in medical technology as they have in automotive engineering. The development of medical products such as wound dressings and prostheses, medical devices such as operating tables, surgical instruments, scissors, endoscopes, etc. is strongly driven by trials. A great deal of testing is carried out, animal experiments are performed, and complex, lengthy and expensive clinical trial series are conducted on humans until products are allowed to be used.

If you look at prostheses, for example, they are handmade by prosthetists. Critical ones are reinforced based on experience and cases of damage. The shape of the residual limb is scanned, but elastic areas, reinforcements and ribs of the socket are more randomly placed.
If the prostheses are printed via 3D printers, there is little empirical data on tolerable stresses. The load distribution, which essentially determines the wearing comfort of a prosthesis, is largely unknown.

Figure 1 3D printed foot prosthesis

How security is purchased

These development processes for medical technology products are very complex, expensive and also unsafe. Safety is often bought by the fact that components are oversized or have to be replaced after too short a time. Interactions with humans are evaluated by means of tests. This costs time and money.

Figure 2 Finite element stress distribution of the prosthesis

What can simulation look like?

Simulations both in flow calculations CFD and in the strength area FEM can greatly accelerate the development processes.

Simulation can be divided into purely technical simulations such as an operating table, an operating light, forceps, a pump or a syringe, and simulations involving interactions with human bodies.
Examples here include wound dressings, decubitus mattresses, exoskeletons, prostheses, stents, and implants.

In the meantime, there are body models or partial body models for finite element studies that can accurately represent bones, muscles, tendons and skin. Here, too, the automotive industry is far ahead, using detailed body dummies for its virtual crash tests.

However, it is also possible to use X-rays, CT scans and MRI scans to specifically create the conditions of an individual patient as an FE model and perform various calculations.

Figure 3 Flow simulation CFD in a nose from a CT scan

As described in more detail in a blog article, a CT scan of the nasal cavity can be used to make statements about how successful a nose operation in which parts of the nasal septum are removed is in terms of freer breathing.

These development processes for medical technology products are very complex, expensive and also unsafe. Safety is often bought by the fact that components are oversized or have to be replaced after too short a time. Interactions with humans are evaluated by means of tests. This costs time and money.

Figure 4 Stress distribution of a wound dressing on the human body

What are the advantages of simulation

The advantage of simulation is, on the one hand, that the invisible becomes visible, e.g. the pressure distribution of a residual limb in a prosthesis socket or the flow conditions in an endoscope, or that the load on the body or technical component can be determined and compared with permissible values.

This information can be used specifically to optimize components, make them lighter, safer and more comfortable, and increase their service life.

Fig. 5 Strength analysis on an operating table

In some cases, the development time for a product is drastically reduced, which is reflected in the development costs.

On the other hand, clinical trials can be shortened. If, for example, tumors are treated by heat, the temperatures can also be determined in the simulation model at arbitrary points without invasive intervention. Heating by appropriate devices can be optimized in a targeted manner.

Scenarios can also be run through in the simulation that are prohibited by law in living humans. One only has to think of cold chamber tests at -70°C to test protective clothing.

Fig. 6 Flow analysis CFD of a laboratory centrifuge

Notes

Merkle & Partner is a network partner of Space2Health, a network that combines solution approaches from medicine, medical technology and aerospace.

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Stefan Merkle
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