Two case reports of 'locked spondyloptosis': the most severe traumatic cervical spondyloptosis with locked spinous process and vertebral arch into the spinal canal.

INTRODUCTION: Traumatic cervical spondyloptosis, including compressive-extension stage 5 of Allen's classification of cervical spine injuries, is commonly observed; however, cases involving locked spinous process and vertebral arch into the spinal canal are extremely rare.

CASE PRESENTATION: We present two individuals with spondyloptosis of C7 with locked spinous process of C6 and the vertebral arch into the spinal canal. Closed reduction was unable to be performed due to rigid locking of the cervical spine in the first case, whereas preoperative closed reduction was achieved with mild traction in a prone position after general anaesthesia in the second case. These two individuals underwent spinal fusion via a posterior approach after open or closed reduction. Six months after surgery, both individuals exhibited significant neurological recovery and acquired a stable gait.

DISCUSSION: To the best of our knowledge, this is the first report of traumatic 'locked spondyloptosis' of the spinous process and vertebral arch into the spinal canal. Although high-grade compressive-extension injuries are usually repaired using a combined anterior-posterior approach, repair is possible with a posterior approach alone with reliable anchors, such as pedicle screws or multiple lateral mass screws. Urgent open reduction may be required for locked spondyloptosis when closed reduction is invalid due to rigid locking of the cervical spine.