A 66-year-old man was brought to the emergency department after being in a motor vehicle crash in which he was rear-ended with very low impact. He complained of point tenderness in the lower thoracic spine, and a trauma workup was performed according to routine protocol.
Thoracic radiographs showed evidence of bulky bridging osteophytes consistent with DISH (diffuse idiopathic skeletal hyperostosis) but no evidence of a fracture at the site of pain. Further evaluation with CT showed a displaced fracture of the T8 vertebral body, which extended through the disc space. The patient was placed in a brace and managed for non-life-threatening injuries, and was then discharged home.
DISH most commonly occurs in the thoracic spine, typically involving T7-T11 levels. Most patients with DISH are discovered incidentally on imaging because they are often asymptomatic. Occasionally, patients can present with pain, postural instability, neurological symptoms, or dysphagia.
A DISH diagnosis is typically made on radiography, followed by cross-sectional imaging, namely CT or MRI. It is characterized by the presence of ‘‘flowing’’ bulky ossifications along the anterolateral margin of at least four contiguous vertebral bodies, preservation of the intervertebral disk height without any degenerative-related findings and absence of apophyseal joint ankyloses, or fusion at the costovertebral or sacroiliac joints. Imaging features are characteristic, but the differential diagnosis for DISH include seronegative spondyloarthropathies such as ankylosing spondylitis, reactive arthritis and psoriatic arthritis.
Unlike ankylosing spondylitis, fusion of the sacroiliac, facet, and uncovertebral joints do not occur in DISH. Similarly, reactive arthritis has asymmetric sacroiliac joint involvement and psoriatic arthritis has a predilection for the cervical and lower lumbar spine, while DISH occurs most commonly in the thoracic spine.
The fused spine in DISH or any preexisting fusion-type condition is more prone to fracture than a normal spine, and these fractures can involve multiple vertebral columns and can occur after even minor trauma. Patients with moderate to severe disease are more prone to fractures. The thoracic and cervical spine are most commonly involved. Hyperextension is the most common mechanism of injury resulting in DISH-related spinal fractures. Acute spinal fractures are not common, but can lead to neurological injury, nonunion, deformity, or death.
DISH produces broad bridging osteophytes that encompass the anterior longitudinal ligament, annulus fibrosis, and paraspinal connective tissues. The bridging osteophytes are most robust at the intervertebral disk space, extending to the adjacent vertebral body. The proximal and distal thirds of a vertebral body, therefore, are typically covered by ossifications, leaving the mid-vertebral body above and below the site of attachment of the ossifications most vulnerable to fractures. Alternatively, fractures may occur at the end of a fused segment, involving the vertebral body at the junction of fused and unfused spine.
Radiographs of the spine may be initially obtained if fractures are suspected following minor trauma. Fractures may not be easily detected with radiographs in the patients with DISH or any other spinal fusion because of overlapping bone and soft tissues and the presence of productive bone formation. It is therefore reasonable to conclude from this case that a low threshold must be used to order a CT scan of the spine if patients with spinal fusion sustain minor trauma. This will not only assist in making an early and accurate diagnosis but ensure appropriate and timely treatment for patients.
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