Lasers and surgical instrumentation

Wednesday 2nd March 2011
Surgical instruments with electronic serial numbers

Lasers are playing a significant role in current surgical instruments, enabling with laser melting the customisation of complex shaped tools, manufactured in a single step, with new functional integrations such as RFID, or capable of employing a welding process to replace traditional suturing.

This year, Fraunhofer-Gesellschaft researchers exhibit several surgical instruments, one with an integrated electronic chip and one for 'weld' suturing at MEDTEC   Europe in Stuttgart.

From heart transplant to Cesarean, operations require a wide variety of instruments, from simple retractors, clamps, scalpels and scissors to more specialist devices such as cerclage wire passers, which surgeons employ to repair long, oblique fractures in bones.

These are shaped to half encircle the broken bone, and incorporate a hollow channel. In a process like stringing a parcel for post, with thread or wire fed through the channel around the damaged bone, then knotted in place, these support the bone holding the broken parts together.

“Until now, it has always been time-consuming and expensive to manufacture surgical instruments featuring this kind of channel,” says Claus Aumund-Kopp of the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen. Because it is nearly impossible to machine curved channels, shaped tubes have traditionally had to be cast, welded or soldered retrospectively.

At the MEDTEC show in Stuttgart from March 22-24 Bremen-based scientists will be presenting a technique enabling the manufacture of surgical instruments of any shape, even those with complex interiors like channels, or those even with integrated RFID chips.

The technique laser melting was originally developed for prototype production, and this manufacturing method uses an extremely fine laser beam to melt a powder material into almost any desired form, one layer at a time.

“Nowadays, laser melting is a mature technology, which has already proved its worth 
 in the manufacture of medical implants,” states Aumund-Kopp.

Like all generative (bottom-up) manufacturing techniques, it has two major advantages. First, contrasted to turning, drilling or milling, hardly any material is wasted. Second, there are no workpiece production-related restrictions on shape or interior structure.

“The designer can focus exclusively on the surgeon’s stated requirements,” says the engineer. For surgical instruments, either cobalt-chromium steel or titanium powders could be used – both are standard materials in generative manufacturing.

Although no-one has yet begun using the laser melting technique to produce surgical instruments, Aumund-Kopp believes it an ideal manufacturing method: “Even small quantities of customised surgical instruments embedding completely new functions could easily be produced in this way,” he reports.

A 3-dimensional model on a computer is the only template needed; intermediate stages, including production of special tools or casting molds, are eliminated.

Steel components that are produced using laser melting technology also  electrical properties. Normally, metals shield against electromagnetic radiation such as radio waves, so for an RFID chip cast in metal, a small opening must be left above it to be readable.

But with laser-melted instruments this is not necessary. Even completely shrouded in metal, the integrated RFID chips are still able to transmit and receive over short distances. “We assume the layered structure of the material shapes the field in such a way that the chips remain readable despite their metal covering,” explains Aumund-Kopp.

This could prove advantageous in the operating room: After every operation, all surgical instruments have to be cleaned, sterilized and counted. With integrated RFID chips, quantities and individual numerical codes could be checked quickly and easily and electronically linked to the operation report or specific instrument data, such as date of manufacture, protocols for use or current state of cleanliness.

Minimally invasive surgeries: laser suturing
Surgeries with the endoscope are exacting and require special capabilities of the surgeon.

The suturing of tissue and the setting of the knots, in particular, is very complicated due to the lack of space for movement. A new, minimally invasive suturing tool simplifies the procedure so suture material will no longer be knotted, but welded with a laser and will be also be displayed at the Stuttgart Fair.

Increasingly abdominal surgeries are carried out in a minimally invasive manner. A small abdominal wall incision sufficient for the surgeon to insert the instrument and make the organs visible with an endoscope.

This technique is gentler and does not stress the body as much as traditional surgeries do. But minimally invasive surgeries pose a special challenge especially suturing the tissue with needle and suture material which demands skill and dexterity to ensure the suture is not too tight, or too loose.

Setting the correct suture tension depends on a surgeon's experience. In future, a minimally invasive suturing instrument will make this easier. Fraunhofer Institute for Production Technology IPT researcher in Aachen has developed this instrument within the scope of the InnoNet project “The Suture."

In a new, semi-automatic process the suturing instrument enables the surgeon to connect the suture material with a previously set, predefined tension. Not only does it shorten the suturing process with respect to time, it also hastens the healing of the wound and the patient is able to recover more quickly.

“With our new device, the edges of the wound can be joined quickly and safely, since it automatically ensures the optimum tension for the suture. The surgeon no longer has to deal with that. In the future, the difficult task of knotting the ends of the suture material will no longer be necessary, since they simply will be welded with the laser,“ explains Dipl.-Ing. Adrian Schütte, an IPT scientist.

The idea for this process is based on laser welding for plastics where two thermo-plastic pieces to be lasered together are welded by means of laser energy.

Schütte says “In our case, the suture material is one of the two pieces to be lasered together, the other one is the sleeve located in the tip of the new suturing device, which has a diameter of 10mm."

First surgeons access the abdominal cavity through a small tube – a trocar. After they pierce the tissue with a needle, they pull the end of the suture material out with the surgical forceps, through the trocar, and clip it into the sleeve.

A defined tension can be set for the suture by pushing the sleeve through the trocar and simultaneously tensioning the suture. Once desired tension has been achieved, the suture material is welded to the sleeve by laser, located at the end of the suturing instrument. The laser beam is sent via the light conducting fibre through the instrument.

Superfluous suturing material is cut off behind the sleeve. Last step, surgeons pull the suturing instrument out through the trocar. After lasering, the sleeve remains in the abdominal cavity. Schütte notes “Currently, the sleeve consists of polypropylene, in the future we would like to manufacture it from resorbing materials."

Together with the InnoNet Project Partners, the scientist and his team were already able to successfully carry out the suturing process during tests in the laboratory. “We were able to achieve the best results with a suture tension of zero to five Newton and a lasering time of 0.1 seconds.“

Preclinical studies are slated to start in the course of this year at the Aachen university hospital.  Initially the suturing instrument will be used for minimally invasive surgeries in the abdominal area, but the researcher is convinced it can also be adapted to keyhole heart surgeries. A prototype of the minimally invasive suturing instrument from IPT will be on display.

The InnoNet project goal "The Suture - Mechatronic Instruments for Complicated Sutures during Minimally Invasive Surgery" is to develop an automated suture aid for use in minimally invasive surgery. Project partners from the areas of research (Fraunhofer IPT and the Faculty for Applied Medical Technology at the RWTH Aachen) medical technology manufacturers (Medi-Globe, Sopro-Comeg), manufacturers of medical sensor  and measurement technology (LEA), specialists for medical suture material (FEG, Ethicon) and end users (Aachen University Hospital) work together to achieve these goals.

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