New Validated Classification for Intervertebral Disk Histology

Abstract

Introduction Intervertebral disk degeneration (IVD) is considered as one of the main causes of chronic low back pain. Consequently, the research on the pathophysiology of IVD degeneration is significantly intensified and new treatment strategies are being developed. In most basic science and pre-clinical studies, histology is an important outcome variable. Nevertheless, an adequately validated histological classification for IVD degeneration is still lacking. Moreover, the existing classifications are elaborate and difficult to use for inexperienced observers. Therefore the aim of this study was to develop and to validate a new histological classification for IVD degeneration. This new classification subsequently was compared to the frequently used nonvalidated classification of Boos et al. Materials and Methods The new classification was applied to sections from 61 human IVDs from all macroscopic degeneration grades. The sections were scored twice by two independent inexperienced observers, twice by an experienced IVD researcher, and once by an experienced pathologist. For comparison, the sections were also scored according to the classification described by Boos et al by two experienced IVD researchers. Macroscopic grading according to Thompson et al and glycosaminoglycan (GAG) content were used for validation of both classifications. Results The new classification had an excellent intra- and a good interobserver reliability, with intraclass correlation coefficients (CC) of 0.84 and 0.73, respectively. Intra and interobserver reliability was comparable for both experienced and inexperienced observers. Statistically significant correlations were found between the new classification, the macroscopic score, GAG content in the nucleus pulposus and age, CC 0.791, −0.620 and 0.687, respectively. The reliability of the Boos classification was comparable to the new classification, however, the CCs for the macroscopic score, GAG content, and age were all low. Conclusion The new histological classification for IVD degeneration is a valuable instrument for evaluating IVD degeneration in human IVD sections and is reliable to use for both inexperienced and experienced researchers. This classification could significantly contribute to the standardization of histological grading of degenerative IVDs. I confirm having declared any potential conflict of interest for all authors listed on this abstract No Disclosure of Interest None declared