Understanding Vascular Risks in Lumbar Transforaminal Epidural Injections: Insights From Anatomy and Clinical Evidence

Clinical Anatomy Understanding Vascular Risks in Lumbar Transforaminal Epidural Injections: Insights From Anatomy and Clinical Evidence

ABSTRACT

Transforaminal epidural steroid injections are frequently used to treat lumbar and radicular pain. Although ischemic complications are extremely rare, their severity-often resulting in irreversible paraplegia-necessitates a thorough understanding of the anatomical and procedural risk factors. This review carefully examines the vascular anatomy of the lumbar intervertebral foramen, the distribution and risks associated with radiculomedullary arteries, and reported cases of severe complications related to lumbar transforaminal epidural steroid injections. Anatomical and radiological data indicate that radicular arteries are particularly rare below the L two-L three level and are more common on the left side. The upper third of the intervertebral foramen, especially at T twelve-L three, is the most likely site of arterial involvement, raising concerns about the safety of traditional subpedicular approaches. Kambin's triangle appears to be a safer alternative, reducing arterial contact while still enabling effective drug delivery. The use of particulate corticosteroids, especially methylprednisolone and triamcinolone, is strongly associated with ischemic events owing to their larger particle sizes. Non-particulate options such as dexamethasone are preferred, particularly at higher spinal levels. Although rare, venous punctures and hematomas require vigilance and careful steroid selection. Test doses of local anesthetics remain controversial and do not provide clear protective benefits. Current evidence indicates that adjusting techniques-including needle placement, imaging guidance, and corticosteroid choice-can help reduce risks while maintaining the effectiveness of lumbar transforaminal epidural steroid injections.

One Introduction

Nineteen nineties, sparking ongoing debate about the safest and most effective anatomical approach, especially given reports of serious complications involving vascular injury during the procedure,

Transforaminal epidural steroid injections have been used since the nineteen sixties to treat lumbar and radicular pain. Their use became widespread during the

Cohen and Rossc two thousand twenty-four. The introduction of dorsal root ganglion pulsed radiofrequency therapy in the late nineteen nineties further increased the use of transforaminal epidural steroid injection procedures.

The close anatomical relationship between the intervertebral foramen and critical neural and vascular structures-including the nerve root, the dorsal root ganglion, and radiculomedullary arteries-has raised concerns about potential complications including intravascular injection of particulate steroids or anesthetics, direct arterial injury causing vasospasm or endovascular edema, thrombosis leading to spinal cord infarction, or hematoma-induced vascular compression resulting in neurological injury. The most likely cause of vasospasm is arterial impingement, not cannulation of its lumen. Another potential complication of impingement on the artery is loosening of an atheromatous plaque, with a ball valve effect. These risks have prompted numerous anatomical studies on the vascular structure of the intervertebral foramen and its importance for spinal and radicular circulation.

Several anatomical studies have suggested potential "safe zones" for transforaminal needle placement; however, the results are often inconsistent. The proposed safe zones include: one, the subpedicular or "safety" triangle, two, Kambin's triangle or suprapedicular zone, and three, the posterior middle third of the intervertebral foramen.

While the value of anatomical studies is acknowledged, their sample sizes are seldom large and rarely include cases with foraminal pathology. Although radiological studies could be more clinically representative, they frequently fail to distinguish between arterial and venous structures and tend to focus on the more cranial lumbar or caudal thoracic intervertebral foramen regions, while most transforaminal epidural steroid injections are performed between the third lumbar and first sacral vertebra.

The aim of this article is to review the literature on the vascular anatomy of the lumbar intervertebral foramen and the complications associated with transforaminal epidural steroid injection critically, and to develop and propose evidence-based recommendations for safer clinical practice.