IMAGING FINDINGS OF ANKYLOSING SPONDYLITIS COMPLICATED WITH SPINAL FRACTURE

Lili Chen¹, Dengfa Yang¹, Tiejun Yang¹, Linyou Wang1, Leiming Xu^{2, *}, Jiawei Wang², Liang Sheng¹

¹Department of Radiology, The Second Affiliated hospital of Zhejiang University School of Medicine, Hangzhou, PR China- ²Department of Radiology, Taizhou Municipal Hospital, Taizhou, PR China 

Objective: To investigate the imaging features of ankylosing spondylitis (AS) complicated with spinal fracture and to reduce missed diagnosis and misdiagnosis.

Methods: The clinical data and imaging features of 48 patients with AS complicated with spinal fracture were analysed retrospectively.

Results: The X-ray examination showed that there were 15 cases of vertebral fracture, four cases of adnexal fracture, 11 cases of intervertebral displacement, 19 cases of intervertebral space widening or narrowing, 11 cases with Andersson damage. In 24 negative cases, fractures could be observed on computed tomography (CT) or magnetic resonance imaging (MRI). Among the 47 patients with CT examination, three fractures were limited to the anterior column of the vertebral body, and 45 cases showed involvement of three columns, and the fracture lines were transverse to the anterior, middle and posterior three columns. Fifteen patients had transverse fracture of the vertebral body; the fracture line was horizontal or slightly oblique across the vertebral body and adnexa. Seventeen patients had intervertebral fracture; the calcified anterior longitudinal ligament was broken, the corresponding level of the intervertebral space was narrow or widened to varying degrees and the fracture line was extended to the posterior accessory ligament complex through the intervertebral space. Thirteen patients had vertebral and intervertebral fractures. Fourteen cases had Andersson damage in the intervertebral fractures, including two cases with accumulated air in the intervertebral space, 25 cases with intervertebral displacement and 36 cases with spinal stenosis. Among 39 patients examined by MRI, 23 showed vertebral fracture with bone marrow oedema of the vertebral body, and 14 cases showed spinal cord injury with high signal intensity of T2-weighted imaging (T2WI) in the spinal cord. In 17 cases of intervertebral fracture, MRI showed that the fracture line extended completely along the intervertebral disc to the posterior adnexal ligament complex. High signal intensity of T2WI in the intervertebral disc, ligamentum flavum, supraspinous ligament and interspinous ligament could be seen, among which 12 cases were accompanied by Andersson damage.

Conclusion: AS complicated with spinal fractures is mainly characterized by transvertebral or/and intervertebral transversal three-column fractures, instability and tendency towards spinal cord injury, and differs from compression fractures that are common in non-AS spine fractures. The key point of distinguishing Andersson lesion type III caused by fracture from infectious spondylitis is that the former features a fracture line involving the posterior adnexal ligament complex.