Thoracic Spine Fracture-Dislocation After Minor Trauma in a Neurologically Intact Patient With Congenital Absence of Posterior Spinal Elements: A Case Report.

Thoracic spine fracture-dislocations are typically the product of high-energy injuries, and their neurological sequelae are usually devastating. For a patient to experience such an injury from a minor trauma and preserve all neurological function is rare and is often credited to the paradoxical decompression effect that follows a traumatic fracture of the posterior elements of the spine. This is a case of a 31-year-old female patient who suffered a severe thoracic spine fracture-dislocation from a low-energy fall from a manually operated "merry-go-round" in a kids' park. Despite the apparent instability, she was totally neurologically intact. Furthermore, MRI and CT were performed, which revealed a fracture-dislocation at the T4-T5 level and a previously undiagnosed congenital absence of the spinous processes and the posterior ligamentous complex at the level of T3-T6. The patient was successfully managed with open posterior reduction and instrumented fusion. Her recovery was complete and remains neurologically intact at long-term follow-up. In the context of severe spinal instability, this case highlights a unique pathophysiological mechanism for neurological sparing. The congenital absence of posterior elements of the thoracic spine created a biomechanically vulnerable segment that is susceptible to dislocation from such a minor trauma. Simultaneously, this also created an abnormally capacious spinal canal that protected the spinal cord from getting injured. This report highlights the importance of having a high index of suspicion for underlying congenital abnormalities when a significant spinal injury occurs from a low-energy mechanism.