The Infraneural Approach to Lumbar Transforaminal Epidural Steroid Injections: A Practical Review for Trainees and Interventionalists

Lumbar transforaminal epidural steroid injections (TFESIs) are commonly performed for the treatment of lumbosacral radicular pain related to disc herniation, foraminal stenosis, lateral recess stenosis, and degenerative spinal conditions. The conventional supraneural or subpedicular approach targets the superior aspect of the neural foramen, historically described as the “safe triangle.” This is what is commonly taught in pain medicine fellowships. However, this region may contain radicular or radiculomedullary arteries, and inadvertent intra-arterial injections have been implicated in rare but catastrophic complications, including spinal cord infarction and paralysis. The infraneural approach, often described in relation to Kambin’s triangle, targets the lower portion of the neural foramen below the exiting nerve root. This technique is a valuable alternative route that may reduce needle placement in the superior-anterior foraminal region while maintaining targeted delivery to the affected nerve root and ventral epidural space. This concise review examines the anatomic rationale, technical considerations, potential advantages, limitations, and safety implications of the infraneural approach for lumbar TFESIs. Although available evidence suggests that infraneural TFESI can provide similar clinical outcomes to traditional approaches in appropriately selected patients, the literature remains limited by technique, injectate selection, and outcome reporting. Careful preprocedural imaging review, fluoroscopic guidance, contrast injection, and preferential use of non-particulate steroid remain essential regardless of approach.