Characterizing human subchondral bone properties using near-infrared (NIR) spectroscopy

Abstract

Degenerative joint conditions are often characterized by changes in articular cartilage and subchondral bone properties. These changes are often associated with subchondral plate thickness and trabecular bone morphology. Thus, evaluating subchondral bone integrity could provide essential insights for diagnosis of joint pathologies. This study investigates the potential of optical spectroscopy for characterizing human subchondral bone properties. Osteochondral samples (n = 50) were extracted from human cadaver knees (n = 13) at four anatomical locations and subjected to NIR spectroscopy. The samples were then imaged using micro-computed tomography to determine subchondral bone morphometric properties, including: plate thickness (Sb.Th), trabecular thickness (Tb.Th), volume fraction (BV/TV), and structure model index (SMI). The relationship between the subchondral bone properties and spectral data in the 1st (650–950 nm), 2nd (1100–1350 nm) and 3rd (1600–1870 nm) optical windows were investigated using partial least squares (PLS) regression multivariate technique. Significant correlations (p < 0.0001) and relatively low prediction errors were obtained between spectral data in the 1st optical window and Sb.Th (R2 = 92.3%, error = 7.1%), Tb.Th (R2 = 88.4%, error = 6.7%), BV/TV (R2 = 83%, error = 9.8%) and SMI (R2 = 79.7%, error = 10.8%). Thus, NIR spectroscopy in the 1st tissue optical window is capable of characterizing and estimating subchondral bone properties, and can potentially be adapted during arthroscopy.

Clinical application of near infrared fiber optic spectroscopy for noninvasive bone assessment

“…Correlations between NIR absorption measurements and bone properties are supported by both the cadaver and MC modeling studies, which indicate that a reflectance NIR probe is capable of sampling M2 bone transcutaneously, with 45% to 50% of the measured spectra's contribution arising directly from the bone. The relationship between direct (ie, not transcutaneous) NIR absorption measures of bone and bone quality has been shown in prior studies, where NIR spectra correlated to subchondral bone morphometric properties as determined by micro‐computed tomography in samples extracted from rats and humans . However, the exponential attenuation of light through absorbing tissues suggests that absorption from the overlying skin, fascia and fat could dominate that from the underlying bone, thus eliminating any correlations between transcutaneous NIR absorption measurements and bone quality.…”

Arthroscopic Determination of Cartilage Proteoglycan Content and Collagen Network Structure with Near-Infrared Spectroscopy

“…The superior penetration depth of NIRS, compared to MIRS, promotes its application for evaluation of whole cartilage tissue in clinical arthroscopies. In contrast to MIRS, NIRS is also capable of providing information on the underlying bone through articular cartilage in both equine and humans 1,27. These studies showed that the visible and short NIR spectral regions are optimal for estimating bone properties, such as subchondral plate thickness and volume fraction, due to their better penetration depth compared to longer wavelengths 20…”

Near-infrared spectroscopy enables quantitative evaluation of human cartilage biomechanical properties during arthroscopy

“…Most probably the spectral response from the superficial cartilage layer, which substantially contributes to cartilage biomechanical capacity, is sufficient for accurate prediction of biomechanical properties. Although spectral region could be restricted to 1,400e2,500 nm, as per Padalkar et al 39 , to limit the effects of subchondral bone 43 , the benefits of utilizing wider spectral region in terms of improved correlation with biomechanical properties and compositional properties outweigh its cons 23,44 .…”