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From Patent to Patient: the Carbon Fibre Needle

14 January 2007

Carbon fibre needles are being used during minimally invasive spine surgery, where magnetic resonance imaging is used to monitor the operation.

One method of treating a slipped disk is to puncture the spinal disks, which involves injecting medicine into the injured area of the body with a thin needle. To be able to monitor the operation at all times and position the instruments accurately, the surgeon requires an image of the affected area, obtained using magnetic resonance imaging (MRI).

“The problem so far, however, was that conventional metal instruments interfere with the magnetic field of the MRI and distort the picture,” explains Sebastian Schmitz of the Fraunhofer Institute for Production Technology IPT. “Our task was to develop instruments made out of fibre reinforced composite materials for use in the tomograph, as these materials afford a clear view.”

To produce a carbon-fibre-reinforced plastic puncture needle that is just as firm and rigid as those made from stainless steel, the researchers have now developed a new manufacturing process. Up to eight thousand individual carbon fibres are treated in a miniaturized pultrusion process – impregnating them with resin under heat and pressure. To incorporate a working channel into the needles, the engineers use hollow glass fibres that are processed together with the carbon fibres. The patented needles have now entered series production on the basis of this method.1

A finished needle with one working channel has a diameter of 0.8 millimetres. Needles with three channels are a little thicker, measuring 1.2 millimetres. One channel, for instance, contains an endoscope that illuminates the tissue to be treated. Via the same route, the reflected light reaches a camera, and the operator sees a moving image on the monitor. The fibre in the second channel conducts laser light, which the surgeon can use to cut or weld tissue. The third channel serves to induct rinsing liquids or medication. In this way, several stages of treatment can be carried out and monitored simultaneously. The needle is suitable for spinal pain therapy, to inject contrast medium into joints for arthrography, and for puncturing cysts.