Root cause analysis of paraplegia following transforaminal epidural steroid injections: the 'unsafe' triangle

The utilization rate of transforaminal epidural steroid injections (TFESIs), an elective diagnostic and therapeutic spinal procedure, has risen dramatically over the past decade. In 2006 alone, greater than 300,000 thoracolumbar TFESIs were performed on Medicare beneficiaries. Despite the purported superiority of the transforaminal route, compared to other modes of epidural injection, TFESIs are associated with potential hazards. The artery of Adamkiewicz (ARM) might enter any mid thoracic, lower thoracic, or lumbar foramen; the exact level, in a specific patient, will be unknown to the proceduralist. The authors propose that the "safe triangle" approach to transforaminal epidural injections is not safe (TFESIs). Injury to the ARM can lead to paraplegia, independent of operator skill or adjuvant safety initiatives (digital subtraction angiography, local anesthetic test dose). Injury to the ARM is a "black swan" event. The authors believe that catastrophic injury may be averted when performing TFESIs by avoiding the "un-safe," superoanterior triangle in the foramen and that transforaminal injections should be performed at the inferior aspect of the foramen, known as Kambin's triangle.