LZH laser device allows precise bone removal

04 Oct 2023

Ablation guided by OCT as alternative to milling should improve surgery for spinal canal stenosis.

A project at Germany's LZH research center is developing a laser platform intended to simplify surgery for spinal canal stenosis, a narrowing of the spinal canal in the lower back.

The condition causes severe pain due to pressure on the nerves in the spinal cord, and traditional surgical solutions have included selectively removing bone from identified areas to relieve the pressure, often through a localized milling operation.

LZH and its partners are now investigating whether a laser-based ablation method for bone removal would offer more precise control of the procedure for surgeons, and be more comfortable for patients.

The InTherSteLa project, named for Innovative Therapy for Spinal Canal Stenosis using Laser Ablation under OCT Control, is scheduled to run until 2025 supported by €250k of federal funding. Participating photonics partners include Laseroptik and Qioptiq Photonics.

"Traditionally, spinal canal stenosis surgeries involve expanding the vertebral canal using a milling tool to thin part of the posterior bony arch of a vertebra as well as parts of the intervertebral joints," commented LZH.

"There is always a risk that the underlying meninges surrounding the nerve canal may be injured and cerebrospinal fluid may leak out. Such complications not only prolong the surgery itself but also the recovery time for patients."

To prevent these kinds of injuries InTherSteLa intends to provide surgeons with better visual control of the process, by developing an instrument in which OCT imaging allows surgeons to see the tissue layers beneath the bone. They can then determine how much bone can be removed with a suitable laser built into the same platform, without hitting the meninges.

VCSEL specialists Octlight indicated that its Caliper-HERO swept source technology was to be used for the OCT imaging aspects of the project.

Hand-held surgical instrument

Use of a laser allows for precise bone removal with an accuracy of 10 to 100 microns, according to LZH, making it a suitable tool for creating a precise passage to the nerve canal. If necessary, a milling operation could then also be combined with this laser-based therapy.

LZH has previously researched how lasers can be applied to other skeletal surgeries, as in the LaZE project launched in 2020 which investigated whether old bone cement could be removed via laser before hip joint replacement procedures, thanks to recent advances in pulse control and output power.

For InTherSteLa, LZH will now study optimizing laser parameters for bone removal and visual representation, as well as considering how the platform can be put to clinical use in the future.

It ultimately envisages a hand-directed instrument similar to an endoscope, enabling surgeons to adapt flexibly to the circumstances during surgery. The requirements for such a handheld device are being developed in collaboration with an experienced surgeon and will undergo preclinical testing at a future date.