Vertebroplasty (cement injection into a vertebra)

Vertebroplasty is a medical spinal procedure in which bone cement is injected through a small hole in the skin into a fractured vertebra with the goal of relieving back pain caused by vertebral compression fractures. Complications from these procedures can however occur and, occasionally, are fatal. Patient specific computer simulation is an ideal tool to assess the risks of an intervention, and to provide a surgeon with recommendations for the amount of cement to be injected, and other parameters.
This type of simulation is however inaccessible to classical mesh-based CFD, as the extremely high porosity poses an unsurmountable to mesh generators. Our meshfree CFD solver has no such issues, and reproduces the full bone filling process with high accuracy.
The right image below shows a computer model, obtained through medical imaging from a damaged human vertebra. On the left image, the vertebra is cut in half to show the results of a computer simulation, showing the progress of a virtual cement injection into the bone.

Image courtesy Annick Baur, EPFL (Lausanne, Switzerland) for all vertebroplasty image data. In collaboration with Dr. VA Stadelmann, AO Research Institute (Davos, Switzerland).

The time evolution of the cement injection is shown on the animation below. The simulation predicts among others on which side of the vertebra the cement exceeds the bone if the injected amount of cement is too large.


Stent design through numerical simulation

Numerical simulation is a crucial tool for understanding the fundamental mechanisms of disease development and for designing new medical devices. Our software provides accurate predictions of medical flow data in human blood vessels. Medical devices like stents are easily integrated in the vessel. The two pictures below for example are obtained from a computer simulation in a human blood vessel with an aneurysm, in which a stent has been introduced. The left image represents the flow pattern in the artery in terms of streamlines. On the righ-hand-side picture, shear stresses on the vessel wall are depicted, which can be related to the risk of rupture of the vessel.


A striking superiority of our software over many other CFD tools stems from its ability to resolve the stent with an extremely fine mesh. Even fine-structured stents with micrometer-scale details are fully resolved (and not just approximated with a continuum porous-media model) to produce accurate predictions on the flow pattern. In the following representation of simulation results for example, the struts of the stent are more than 1'000 times smaller than the diameter of the artery, and yet the stent geometry is fully resolved.

The use of a stent, in the example shown here, is to change the flow pattern in order to stabilize the aneurysm. As the comparison in the animation below (in a steady regime) shows, the stent deviates the flow from the aneurysm into the artery branch ahead, while a minor flow branch is still directed into the aneurysm.

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