NIR Spectroscopy Enables Accurate Evaluation of Osteoarthritis

An arthroscopic probe, developed at the University of Eastern Finland, could be used to quantitatively assess the health of joint tissues, improving physicians’ ability to detect initial signs of post-traumatic osteoarthritis (PTOA).

The surgical instrument utilizes NIR spectroscopy (NIRS) to determine the rigidity of the cartilage and the mineral content of the cartilage bone, enabling more accurate detection of cartilage and bone loss. It also assesses the health of the surrounding tissue. The availability of comprehensive information on the condition of joint tissues through quantitative assessment of lesion severity and extent could enhance the treatment outcomes of arthroscopic interventions.

The novel arthroscopic probe in an equine knee joint in vivo, with the probe tip in contact with cartilage surface (inset). Courtesy of Jaakko Sarin.

Researcher Jaakko Sarin investigated the potential of arthroscopic NIRS to simultaneously monitor progressive degeneration of cartilage and subchondral bone in vivo in Shetland ponies undergoing different experimental cartilage repair procedures. Osteochondral tissues adjacent to the repair sites were evaluated using an arthroscopic NIRS probe, and significant degenerative changes were observed in the tissue properties when compared with tissues from healthy joints.

According to Sarin, clinical application of NIRS, a technique that is typically used to evaluate food quality, is possible now thanks to the availability of advanced computational power and mathematical modeling methods such as artificial neural networks (ANNs). Sarin used multivariate analysis techniques and ANNs to model the relationships between NIR spectral data and reference parameters such as cartilage biomechanical properties. This enabled him to reliably determine articular cartilage stiffness and subchondral bone mineral density from in vitro spectral data. Changes in these tissue properties are prognostic indicators of OA.

Sarin also investigated the effectiveness of optical coherence tomography (OCT) and ultrasound imaging for evaluating joint health. Both techniques are well-suited for imaging narrow joint cavities. The study compared the reliability of these methods for evaluation of chondral injuries with that of conventional arthroscopic evaluation. Conventionally, joint health is diagnosed based on the patient’s symptoms and joint mobility, and with x-ray and MRI.

Optical coherence tomography was found to be the most reliable method. “In contrast to conventional arthroscopic evaluation, optical coherence tomography and ultrasound imaging provide information on inner structures of cartilage and enable, for example, detection of cartilage detachment from subchondral bone,” Sarin said.

The research was published in Scientific Reports (https://doi.org/10.1038/s41598-018-31670-5).