Histological characteristics of diffuse idiopathic skeletal hyperostosis.

Diffuse idiopathic skeletal hyperostosis (DISH) is a predominantly radiographic diagnosis and histological knowledge of DISH is limited. The aim of this study was to describe the histological characteristics of DISH in the spinal column and to study the relation between DISH and intervertebral disc (IVD) degeneration. Therefore, 10 human cadaveric spines with fluoroscopic evidence of DISH were compared with 10 controls. Plain radiographs and computed tomography (CT) scans were obtained and tissue blocks were resected from three predefined levels of all specimens. The microscopic sections were scored by two blinded observers using a newly developed scoring system specific for characteristics of DISH and a validated scoring system for IVD degeneration. Maximum IVD height was measured on the CT scans. Analyses were performed using Fisher's exact test and Student's t-test. When compared to controls, the right sided sections from DISH specimens showed partial or complete bone bridges, consisting of cortical woven bone, accompanied by morphological changes in the adjoining part of the IVD. Using the histological scoring system for DISH, all parameters were significantly different between the DISH and control group (p < 0.01). The contralateral location did not show differences between the groups. The overall degree of IVD degeneration and height of IVD was comparable for the two groups. The histopathological changes observed in spines with DISH corresponded to the fluoroscopic images and CT scans. The degree of IVD degeneration and IVD height was comparable for both groups, suggesting a limited role for IVD degeneration in the pathogenesis of DISH. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:140-146, 2017.

The influence of diffuse idiopathic skeletal hyperostosis on bone mineral density measurements of the spine.

OBJECTIVES: BMD has been described to be increased in patients with DISH. The contribution of the ossified anterior longitudinal ligament (ALL) on vertebral body BMD is currently unknown. We investigated the influence of DISH on BMD measurements using an experimental DXA scanning protocol. METHODS: Ten DISH specimens and 10 matched human cadaveric spines were used. After assessment of the localization and orientation of the ossified ALL with CT, BMD was measured using an experimental DXA protocol, exploiting the asymmetry of DISH in the thoracic spine. For controls, identical orientations were used and both groups were compared for differences in BMD. RESULTS: Specimens with DISH displayed a significantly higher BMD than their matched controls when the ossified ALL was present in the scanning field. Measurements of the left half of the spine were comparable for DISH specimens and controls (P = 0.446). The right-left difference in anteroposterior view was statistically significant within DISH specimens (P = 0.001), but not in controls (P = 0.825). CONCLUSIONS: The variability in measurements in different scanning orientations suggests a substantial contribution of the ossified ALL to the total BMD in DISH specimens, ranging from 23.6 to 39.0%. Vertebral body BMD does not seem to be increased, as demonstrated by comparable BMDs in the unaffected left half of the spine. It is suggested that routine anteroposterior DXA scanning may overestimate the true vertebral body BMD in DISH patients.

The prevalence of diffuse idiopathic skeletal hyperostosis in an outpatient population in The Netherlands.

OBJECTIVE: In diffuse idiopathic skeletal hyperostosis (DISH), spinal ankylosis may occur due to longitudinal ligament ossification. DISH can lead to back pain, impaired mobility, and displaced fractures after minor trauma. Its etiology is unknown, but is associated with obesity and type 2 diabetes mellitus. We investigated the prevalence of DISH in an outpatient population in the Netherlands. METHODS: Chest radiographs of 501 patients (age > 50 yrs) referred to our institution by general practitioners for non-spine-related conditions were reviewed. DISH was established according to defined criteria; 3-level involvement was defined as pre-stage DISH. Logistic regression analysis was used to investigate the influence of age and sex on the prevalence of DISH. RESULTS: The overall prevalence of DISH was 17.0% (95% CI 13.7-20.3). A significant increase with age was observed (odds ratio 1.03, 95% CI 1.01-1.05; p = 0.006). The odds ratio of male sex was 1.85 (95% CI 1.20-2.86; p = 0.006). The individual predicted probability of developing DISH was 32.1% in 80-year-old men and 16.9% in women of the same age. Pre-stage DISH was found in 4.6% of the individuals and was more frequent in women. CONCLUSION: The prevalence of DISH in this outpatient cohort was 17.0%, which is high compared to recent reports. Age and sex were significantly related to the presence of DISH, suggesting that men and older individuals have a higher probability of developing DISH.