Ectopic spinal calcification associated with diffuse idiopathic skeletal hyperostosis (DISH): A quantitative micro‐ct analysis

Abstract

Diffuse idiopathic skeletal hyperostosis (DISH) is a non‐inflammatory spondyloarthropathy identified radiographically by calcification of the ligaments and/or entheses along the anterolateral aspect of the vertebral column. The etiology and pathogenesis of calcifications are unknown, and the diagnosis of DISH is currently based on radiographic criteria associated with advanced disease. To characterize the features of calcifications associated with DISH, we used micro‐computed tomographic imaging to evaluate a cohort of 19 human cadaveric vertebral columns. Fifty‐three percent of the cohort (n = 10; 3 females, 7 males, mean age of death = 81 years, range 67–94) met the radiographic criteria for DISH, with calcification of four or more contiguous vertebral segments. In almost all cases, the lower thoracic regions (T8‐12) were affected by calcifications, consisting primarily of large, horizontal outgrowths of bony material. In contrast, calcifications localized to the upper thoracic regions demonstrated variability in their presentation and were categorized as either “continuous vertical bands” or “discontinuous‐patchy” lesions. In addition to the variable morphology of the calcifications, our analysis demonstrated remarkable heterogeneity in the densities of calcifications, ranging from internal components below the density of cortical bone to regions of hyper‐dense material that exceeded cortical bone. These findings establish that the current radiographic criteria for DISH capture heterogeneous presentations of ectopic spine calcification that can be differentiated based on morphology and density. These findings may indicate a naturally heterogenous disease, potential stage(s) in the natural progression of DISH, or distinct pathologies of ectopic calcifications. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

Dystrophic calcification and heterotopic ossification in fibrocartilaginous tissues of the spine in diffuse idiopathic skeletal hyperostosis (DISH)

“…The classic radiographic feature of DISH is the presence of flowing mineralization along the anterolateral aspect of the vertebral column, 1 but our previous report identified heterogeneity in the morphological appearance of ectopic mineral associated with DISH based on µCT analysis. 27 This heterogeneity was likewise evident in the histological appearance of individual motion segments from spines with DISH based on variability noted in the structure, (Fig. 1a), b-bʹʹ thoracic segment T3-4 from a 72-year-old male with dystrophic calcification (Fig.…”

“…The features of ectopic mineral formation that define DISH have been primarily characterized through clinical imaging, with few Based on these and previous studies from our group, 27 we postulate that the two forms of ectopic mineralization may reflect different disease processes or perhaps distinct stages in the pathogenesis of DISH.…”

“…A previous study by our group characterized the morphometry and radiodensity of ectopic mineral associated with DISH in embalmed cadaveric human spines using microcomputed tomography (µCT) imaging. 27 Mineral formations at individual motion segments in the thoracic spine were differentiated based on morphology, categorized as vertical bands when the resultant bridging angle relative to the vertebrae was greater than 90°, as horizontal outgrowths when the resultant bridging angle was <90°, or as discontinuous-patchy when the mineral formed an incomplete bridge. 27 For the present study, we carried out detailed analyses of 15 individual motion segments from the thoracic spine of six donors with DISH from the previous study (one female and five males; median age 82 years, range 72-87) ( Fig.…”

“…27 These spines were selected based on (i) having met the diagnostic criteria for DISH (with at least four contiguous segments affected, 2 previously assessed by two clinician observers) and (ii) each spine containing at least two of the three morphological presentations of ectopic mineralization described in our previous study (discontinuous-patchy, vertical, or horizontal). 27 Histological features of spinal tissues Twelve regions of the spine containing ectopic mineral structures at individual motion segments were isolated ( Supplementary Fig. S1) to assess the histological appearance of affected tissues.…”

“…Microcomputed tomography (µCT) imaging Intact human vertebral columns were previously scanned by µCT as described 27 using a cone-beam X-ray imaging system (GE Locus eXplore Ultra: London, CAN) at a peak voltage of 80 kVp and tube current of 50 mA. The 1 000 X-ray projections were reconstructed into a single three-dimensional volume with an isotropic voxel spacing of 154 µm.…”