Optical absorption spectra of human articular cartilage correlate with biomechanical properties, histological score and biochemical composition

This study investigates the relationship between the optical response of human articular cartilage in the visible (VIS) and near infrared (NIR) spectral range and its matrix properties. Full-thickness osteochondral cores (dia. = 16 mm, n = 50) were extracted from human cadaver knees (N = 13) at four anatomical locations and divided into quadrants. Absorption spectra were acquired in the spectral range 400-1100 nm from one quadrant. Reference biomechanical, biochemical composition, histological, and cartilage thickness measurements were obtained from two other quadrants. A multivariate statistical technique based on partial least squares (PLS) regression was then employed to investigate the correlation between the absorption spectra and tissue properties. Our results demonstrate that cartilage optical response correlates with its function, composition and morphology, as indicated by the significant relationship between spectral predicted and measured biomechanical (79.0% <= R-2 <= 80.3%, p < 0.0001), biochemical (65.1%. R-2 <= 81.0%, p < 0.0001), and histological scores (R-mankin(2) = 83.3%, p < 0.0001) properties. Significant correlation was also obtained with the non-calcified cartilage thickness (R-thick(2) = 83.2%, p < 0.0001). We conclude that optical absorption of human cartilage in the VIS and NIR spectral range correlates with the overall tissue properties, thus providing knowledge that could facilitate development of systems for rapid assessment of tissue integrity.