Microcalcification of lumbar spine intervertebral discs and facet joints is associated with cartilage degeneration, but differs in prevalence and its relation to age

Cartilage calcification (CC) is associated with degeneration in non-vertebral joints, but little is known about CC and lumbar vertebral joints. The goal of this study was to analyze the prevalence of CC in lumbar facet joints (FJ) and intervertebral discs (IVD) and its relation to cartilage degeneration and age in a non-selected cohort of the general population. The segment L4/5 of 85 consecutive donors (mean age 61.9 years) was analyzed by high-resolution imaging digital-contact radiography (DCR). Quantification was achieved by measuring CC in % of total cartilage area. Histological degeneration of FJs and IVDs was determined by OARSI and Boos scores. Prevalence of CC was 36.5% for FJ (95%CI (0.26, 0.48)) and 100% for IVD (95%CI (0.96, 1.00)). The amount of IVD CC (3.36% SD +/- 7.14) was 16.3 times higher (p<0.001) than that of the FJ (0.23% SD +/- 0.53) and independent of each other (p=0.07). The amount of FJ CC correlated significantly with FJ and IVD degeneration (FJ r=0.44, p=0.01, IVD r=0.49, p=0.006) while the amount of IVD CC correlated only with IVD degeneration (r=0.54, p<0.001). Age correlated with IVD CC (r(s)=0.35, p<0.001), but not FJ CC (r(s)=0.04, p=0.85). We conclude that IVD fibrocartilage is particularly prone to calcification. A causal relationship between lumbar CC and degeneration is possible, but the clear differences in IVD fibrocartilage CC and FJ synovial joint CC in regard to prevalence and in relation to age point to a differential role of CC in single compartments of the respective motion segment in lumbar spine degeneration. (c) 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2692-2699, 2017.