Spinal mobility and functional limitations in patients with diffuse idiopathic skeletal hyperostosis compared to healthy controls and patients with axial spondyloarthritis

Background Diffuse idiopathic skeletal hyperostosis (DISH) is characterised by ossification of the spine including the anterior longitudinal ligament. While often still considered a pure radiographic finding, recent evidence suggests relevant impairments in physical functioning. Objective To evaluate spinal mobility and functional limitations in DISH compared with radiographic (r-) and non-radiographic (nr-) axial spondyloarthritis (axSpA) and healthy controls (HCs). Methods Consecutive patients and HCs were assessed regarding mobility, including the Bath Ankylosing Spondylitis Metrology Index (BASMI), Short Physical Performance Battery (SPPB), Ankylosing Spondylitis Performance-based Index (ASPI), electronic measures of measuring range of motion (ROM) and range of kinematics (ROK) with the Epionics SPINE. Results We examined 50 patients with DISH, 30 patients with axSpA and 20 HCs. Compared with HC, patients with DISH showed significantly worse BASMI (4.6±1.0 vs 2.8±0.6), SPPB (10.2±2.0 vs 11.9±0.4), ASPI (46.5±26.1 s vs 20.3±5.3) and broad restrictions across ROM and ROK measures (all p<0.001). Compared with axSpA, BASMI (4.6±1 vs 5.1±1.9; p=0.13), SPPB (10.2±2.0 vs 9.5±1.3; p=0.08) and ASPI (46.5±26.1 vs 47.4±23.9; p=0.91) were comparable, but profiles differed: patients with DISH performed better in rotation to both sides and hip-related measures. Age-adjusted analyses confirmed similar group differences independent of age. Conclusion DISH is associated with substantial impairments in spinal mobility and physical performance compared with HC. While limitations were comparable to axSpA, the restriction pattern differed, with DISH showing less deficits in rotational movement. These findings highlight that DISH is not merely a radiographic condition but patients experience significant impairments of mobility, similar to axSpA.