| 释义 |
Trolley Track Sign A term for the combination of the dagger sign—a single central vertical radiodense line caused by ossification of the interspinous and supraspinous ligaments—and the railroad sign—a pair of lateral vertical linear lines—caused by ossification of the apophyseal joints. The three vertical ossified lines together make up the trolley-track sign and are seen on AP view in patients with ankylosing spondylitis |