Distribution of spinal damage in patients with axial spondyloarthritis as assessed by MRI: a prospective and blinded study

Abstract

Background Axial spondyloarthritis (SpA) leads to structural bone lesions in every part of the vertebral column. These lesions are only partially visualized on conventional radiographs omitting posterior parts of the vertebral column and the thoracic spine. We therefore evaluated the distribution of structural bone lesions which are partly responsible for immobility and impaired function of the spine in patients with axial SpA based on magnetic resonance imaging (MRI). Methods In this prospective and blinded investigation, we assessed the distribution of structural spinal bone lesions using MRI in patients with axial SpA classified according to the Assessment in Spondyloarthritis International Society (ASAS) criteria of axial SpA. After clinical examination, collection of data of spinal mobility and function two blinded radiologists independently evaluated MRIs of 23 vertebral units of the spine in every patient. Non-parametric statistical methods and Spearman‘s correlation was used to analyze lesion distribution and the relationship with clinical spinal mobility and function parameters. Results In 55 patients with axial SpA (13 females, average disease duration 14.9 years) 657 ventral and 139 dorsal vertebral body structural bone lesions and, notably, 534 facet joint lesions could be visualized. The median number of lesions per patient was higher in the thoracic (8.5, range 1.0–41.0) than in the lumbar (7.5, range 0.0-27.5) and the cervical spine (3.5, range 0.0-24.5); each with p < 0.005. A negative correlation was noted between the number of osteoproliferative structural bone lesions and impairment of spinal mobility and function. Conclusion This MRI-based study revealed a high prevalence of structural bone lesions in dorsal parts of the vertebral column and in the thoracic spine of axial SpA patients that are not adequately visualized on conventional radiographs. These findings may further contribute to a better understanding of reduced mobility of the spine typically associated with axial SpA and may support rheumatologists with the diagnosis.