Evaluation of the bony repair in rat cranial defect using near infrared reflectance spectroscopy and discriminant analysis.

We set out to determine whether near infrared reflectance spectroscopy (NIRS) combined with principal component analysis-linear discriminant analysis (LDA) or, variable selection techniques employing successive projection algorithm or genetic algorithm (GA) could evaluate the bone repair in cranial critical-size (5 mm) defect after stimulation with collagen sponge scaffold and/or infrared low-level laser therapy directly on the local. Forty-five Winstar rats were divided into nine groups of five each, namely: group H - healthy, n = 5 (without treatment and without cranial critical-size defect), (GI positive control - n = 5, 21 days or n = 5, 30 days) without treatment and with cranial critical-size defect; (GII-n = 5, 21 days or n = 5, 30 days) cranial critical-size defect filled with collagen sponge scaffold; (GIII-n = 5, 21 days or n = 5, 30 days) cranial critical-size defect submitted to low-level laser therapy; (GIV-n = 5, 21 days or n = 5, 30 days) cranial critical-size defect submitted to combined collagen sponge scaffold + low-level laser therapy treatment. In relation to the histological analysis, the collagen sponge scaffold + low-level laser therapy treatment group (GIV) 30 days showed the best result with the presence of secondary bone, immature bone (osteoid) and newly formed connective tissue (periosteum). GA-LDA model also successfully classified control class of the others classes. Thus, the results provided by the good-quality classification model revealed the feasibility of NIRS for application to evaluation of the wound healing in rat cranial defect, thanks to the short analysis time of a few seconds and nondestructive advantages of NIRS as an alternative approach for bone repair purposes. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1160-1168, 2017.