Fraunhofer ILT laser-guided spinal surgery minimizes risk to patients

23 Oct 2024

Robotic platform using OCT to monitor progress shows benefits of laser surgery near spine.

A project at Fraunhofer ILT is developing a new robot-assisted and optically monitored laser surgery system for treatment of spinal canal stenosis.

The condition, in which bony constrictions form in the spinal canal, can cause chronic pain and paralysis, but surgical intervention is tricky due to proximity to the spinal cord and risk of injury from the surgery itself.

The use of lasers in treating the condition has been investigated for some time, with Hannover's LZH research center demonstrating that a laser ablation technique could offer surgeons more precise control over bone removal than traditional milling methods.

Fraunhofer ILT set out to integrate a laser ablation technique into a robot-assisted surgical platform, in which the cutting depth could be monitored continuously using OCT.

A patent application has also been filed for the idea of a robotically assisted laser surgery system for the precise and safe cutting of bones, said the Fraunhofer team.

The principle of these laser surgery systems is based on ablating the bone tissue with nanosecond laser pulses. Short pulse duration not only minimizes thermal interaction with the surrounding material, to prevent carbonization of the cut edges and promote the healing process, but also ensures a high degree of microsurgical precision.

The potential for robotic surgery platforms has expanded in parallel with developments in short-pulse medical lasers, along with advances in the utility of the platforms for surgeons. A forum at the 2023 LASER World of Photonics event heard that advances in immersive eyepieces, haptic sensors and stereoscopic optics will be key to helping surgeons experience feedback that is lost in a transition away from conventional hands-on surgery.

A new gold standard for delicate procedures

According to Fraunhofer data, the OCT-monitored spinal canal stenosis system "can determine the thickness of the remaining bone lamella at the bottom of the kerf from a residual thickness of approximately 400 microns. The OCT measurement carried out synchronously with the cutting process is therefore the key to reliable control of the cutting process, based on the residual bone thickness."

Once the individually defined residual thickness has been reached, the cutting process should stop automatically. The surgeon can then lift off the loosened bone with little effort and without risk to the nerve tracts in the spinal canal.

Haptic feedback can be provided to surgeons via the sensors and actuators of the collaborative robot, or "cobot." A cobot's force-torque sensor system determines the force effect on the robot arm, with the actuator system giving the operator haptic feedback when manually guiding a laser applicator.

The long-term research goal at Fraunhofer ILT is to establish this kind of robotically assisted laser procedure for cutting hard tissue as the gold standard for operations close to critical structures, commented the project.

"Thanks to the optical monitoring and precise control of the laser cutting process, our procedure could prevent serious injuries to the spinal cord and nerve roots in future," said Achim Lenenbach, head of the Laser Medical Technology and Biophotonics Department at Fraunhofer ILT.

"The laser surgery system developed at our institute could implement the preoperatively planned incisions with sub-millimeter precision."