Unrecognized c1 lateral mass fracture without instability; the origin of posterior neck pain.

Posterior neck pain is a common complaint of patients in the pain clinic. The atlas (C1) burst fracture is known to be a cause of posterior neck pain and instability. Although the atlas burst fracture and instability can be discovered by plain X-rays which show lateral mass displacement or widening of the atlantodental interval, assessment of an atlas burst fracture can be difficult if there is no instability in the imaging study. Here we report a case of a 46-year-old female patient who had complained of sustained posterior neck pain for 6 months. Plain X-rays showed only disc space narrowing at C4/5 and C5/6, without any cervical instability. However, an unrecognized C1 lateral mass fracture was detected by CT and MRI. The patient's pain was then successfully treated after atlantoaxial joint injection with a C2 DRG block.