Calcification in human intervertebral disc degeneration and scoliosis

Calcification is a pathological process that may lead to impairment of nutrient supply and disc metabolism in degenerative and scoliotic intervertebral discs (IVDs). The purpose of this study was to assess the calcification potential of IVDs in degenerative disc disease (DDD) and adolescent idiopathic scoliosis (AIS). For this purpose, 34 IVDs from 16 adult patients with DDD and 25 IVDs from 9 adolescent patients with AIS were obtained at surgery. The concave and convex parts of the scoliotic discs were analyzed separately. Von Kossa staining was performed to visualize calcium deposits, while type X collagen (COL X) expression associated with endochondral ossification was measured by immunohistochemistry. Alkaline phosphatase activity and calcium and inorganic phosphate concentrations were used as indicators of calcification potential. Results showed the presence of calcium deposits and COL X in degenerative and scoliotic IVDs, but not in control discs, and the level of the indicators of calcification potential was consistently higher in degenerative and scoliotic discs than in control discs. The results suggest that disc degeneration in adults is associated with ongoing mineral deposition and that mineralization in AIS discs might reflect a premature degenerative process. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1888–1895, 2011