connectivity by design.
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Guidewires have been used for ages to perform image-guided procedures in the circulatory system, such as angioplasty, catheter insertion, stent placement and brain surgery. They require precise intravascular steerability for accessing difficult-to-reach anatomical locations and limiting damage inside the body. We developed an intrinsically safe design that offers physicians active endovascular access through enhanced maneuverability. This was achieved with the ingenious, ergonomic design of a guidewire and a one-hand controller that is able to steer only the guidewire’s tip.
Guidewires are usually made from nitinol, the metal alloy of nickel and titanium that is famous for its superelasticity. Fully exploiting this unique property, we developed a new concept for a steerable guidewire. It consists of three parts: two thin nitinol tubes provided with a helical cut that slide over each other, and a pull wire through the interior.
Our design, the Redwire, includes a one-hand controller that enables the physician to manipulate the interplay of the three parts such that independent bending and rotation of the guidewire’s tip inside the patient’s body can be achieved. This makes it easier to take turns when reaching complex junctions, thus speeding up the procedure and potentially improving its outcome. Intrinsic patient safety is ensured by the biocompatibility of the product design and the presence of the pull wire, which in the unlikely case of breakage keeps all parts together.
The controller can be used intuitively due to its ergonomically sound design, derived from extensive usability studies and based on multi-physics simulations. During operation, it can be disconnected from the guidewire to add a new catheter, for example. The controller is manufactured with high cost-effectiveness and reproducibility by injection molding.
We also performed in-depth multi-physics simulations of the guidewire design, concerning bending shape, rotation behavior, tip load, support stiffness, force actuation and maximum stresses. This helped us to properly understand and ultimately predict the metal deformation and resulting guidewire behavior, giving us maximum control over the design. Experimental validation showed that we can use the simulations accurately for virtual prototyping of guidewires.
In this way, we have built a platform that contains all the required design rules for making a custom steerable guidewire. Diameter and tip stiffness as well bending radius and location are adjustable. This opens up possibilities for the realization of guidewires of 1.5 to 3 meter length for various applications, in the clinic and beyond.
It has been very special to develop a major innovation like the Redwire for a medical instrument that is of great use in potentially life-saving procedures. We talked to physicians about their needs and the new applications and added value they expected from a guidewire. Our new design, which was developed in a collaboration with Peter Besselink from Memory Metal Holland B.V., extends their range in operation. They can, for example, take an extra corner to reach the intended target in the circulatory system exactly or to guide the catheter of choice that cannot be handled by a conventional wire.