Replacing bone saws with smart lasers

Using lasers rather than scalpels and saws has many advantages in surgery. However, they are only used in isolated cases. But that could be about to change: laser systems are becoming increasingly intelligent and improved, as a research team from the University of Basel demonstrates.

Even in 1957, when Gordon Gould coined the term “laser” (short for “Light Amplification by Stimulated Emission of Radiation”), he was already imagining the possibilities of its use in medicine. Surgeons would be able to make precise incisions without even touching the patient.

But before that could happen, there were – and still are – many obstacles to overcome. Manually operated light sources have been replaced by mechanical and computer-controlled systems to reduce injuries caused by clumsy handling. The switch from continuous beams to pulsed lasers, which turn on and off quickly, has reduced the heat they produce. Technical advances allowed lasers to enter the world of ophthalmology in the early 1990s. Since then, the technology has also evolved in other areas of medicine, but it has only replaced the scalpel and bone saw only in relatively few applications.

Safety concerns pose the biggest obstacle: how can we avoid injury to surrounding tissue? How well can the depth of cut be controlled so that deeper layers of tissue are not accidentally damaged?

Researchers from the University of Basel have made an important contribution to the safe and precise use of lasers with their recent publication in the journal Lasers in surgery and medicine. The research team, led by Dr Ferda Canbaz of the Department of Biomedical Engineering in Basel and Professor Azhar Zam, formerly of the University of Basel but now based at New York University, developed a system that combines three functions: it cuts bones, controls cutting depth and differentiates different tissues.

Three lasers aimed at one location

These three functions are provided by three lasers aligned to focus on the same location. The first laser serves as a tissue sensor as it scans the surrounding area of ​​the site where the bone is to be cut.

Pulses are sent with this laser to the surface at regular intervals, so to speak, vaporizing a tiny bit of tissue each time. The composition of this vaporized tissue is measured with a spectrometer. Each type of fabric has its own spectrum, its own signature. An algorithm processes this data and creates a sort of map that shows where the bones are and where the soft tissue is.

Only when all this is complete does the second laser, which cuts the bones, activate, and only in places where bones rather than soft tissue are represented on the map just generated. At the same time, the third laser, an optical system, measures the depth of the cut and verifies that the cutting laser does not penetrate deeper than expected. During the cutting phase, the fabric sensor also continuously monitors whether the correct fabric is cut.

Autonomous control

“The particularity of our system is that it controls itself, without human interference,” explains Ferda Canbaz, laser physicist.

The researchers have so far tested their system on femur bones and tissues from pigs acquired from a local butcher. They were able to prove that their system works with an accuracy of a few fractions of a millimeter. The speed of the combined laser also approaches that of a conventional surgical procedure.

The research team is currently working on making the system smaller. They have already reduced it to the size of a matchbox by combining the optical system and the cutting laser alone, as shown in Optical Continuum. Once they add the tissue sensor and manage to further miniaturize the entire system, they should be able to insert it into the tip of an endoscope to perform minimally invasive operations.

Less invasive surgery

“More use of lasers in surgery is a laudable ambition for several reasons,” says Dr. Arsham Hamidi, lead author of the study. Contactless cutting reduces the risk of infection somewhat, he points out. “Smaller, more precise incisions also mean tissue heals faster and scarring is reduced.”

Cutting in a controlled manner using lasers also allows new cutting shapes to be applied, so that, for example, a bone implant can be physically locked with the existing bone. “One day we may be able to do without bone cement altogether,” adds Ferda Canbaz.

There are also other areas of surgery where this type of combined setup would be useful: it could allow tumors to be more accurately distinguished from surrounding healthy tissue and then cut out without removing an unnecessary amount of neighboring tissue. One thing is certain: Gordon Gould’s vision of the laser as a versatile medical tool is getting closer and closer.