Erector Spinae Block: How It Works, Benefits, and Techniques

Regional anesthesia techniques are increasingly valuable for managing pain while minimizing opioid use. Among these, the erector spinae block (ESB) has gained attention for its versatility and safety. It provides effective analgesia in various surgical and non-surgical settings with a relatively low risk of complications.

Its popularity is due to its ability to cover multiple dermatomes with a single injection. Understanding its mechanism, benefits, and placement techniques helps optimize its clinical use.

Relevant Anatomy

The ESB targets the erector spinae muscle group, which runs along the vertebral column and consists of the iliocostalis, longissimus, and spinalis muscles. These muscles originate from the sacrum, iliac crest, and lumbar spinous processes, extending superiorly to insert on the ribs and transverse processes of the cervical and thoracic vertebrae. Their primary function is to maintain posture and facilitate spinal extension and lateral flexion.

Beneath these muscles lies a network of nerves contributing to the block’s analgesic effects. The dorsal rami of the spinal nerves provide sensory innervation to the posterior thorax, back, and lumbar regions. Additionally, the ventral rami, which form the intercostal nerves in the thoracic region, are indirectly affected as the anesthetic diffuses anteriorly. This broad nerve involvement explains why a single injection can provide multi-dermatomal coverage, making the ESB useful for thoracic and abdominal procedures.

The fascial plane where the anesthetic is deposited determines its spread. The erector spinae plane, a loose connective tissue space, allows diffusion both cranially and caudally, often spanning from the cervical to lumbar regions depending on the anesthetic volume and concentration. Imaging studies have shown that the injectate can extend several vertebral levels, sometimes reaching the paravertebral space, enhancing its efficacy for visceral pain management.

Mechanistic Considerations

The ESB modulates pain transmission through direct and indirect mechanisms. By depositing local anesthetic between the erector spinae muscles and transverse processes, it blocks the dorsal rami, which supply sensory innervation to the posterior thorax, back, and lumbar regions. The anesthetic often extends to the ventral rami and, in some cases, the paravertebral space, broadening its analgesic effect.

The spread of local anesthetic depends on fascial anatomy and the injectate’s properties. Contrast-enhanced imaging shows that the anesthetic can travel several vertebral levels, sometimes reaching the epidural and paravertebral spaces. Higher volumes, typically 20–30 mL, result in more extensive spread, while lower volumes provide more localized effects. Lipophilic anesthetics like ropivacaine or bupivacaine offer prolonged action.

Beyond direct anesthetic effects, the ESB may reduce neurogenic inflammation and central sensitization, key contributors to persistent pain. By dampening nociceptive input at the spinal level, it may decrease secondary hyperalgesia, leading to lower opioid requirements and improved recovery. Some studies suggest it has mild sympatholytic effects when the anesthetic reaches the paravertebral space, enhancing its role in managing rib fractures and chronic thoracic pain.

Variations In Placement

The ESB can be performed at different vertebral levels to target specific regions. While the fundamental technique remains the same—injecting anesthetic into the fascial plane between the erector spinae muscles and transverse processes—the level of injection determines the extent of analgesia.

Cervical

At the cervical level, the ESB provides analgesia for the neck, upper thorax, and shoulder. It is useful for postoperative pain following cervical spine surgery, clavicle fractures, or shoulder procedures. The injection is typically placed at C6 or C7, where the anesthetic affects the dorsal rami of the cervical spinal nerves. Some studies suggest it may also reach the brachial plexus, enhancing upper limb analgesia.

Ultrasound guidance ensures accurate placement, as the cervical region contains critical vascular and neural structures, including the vertebral artery and cervical sympathetic chain. Due to these structures’ proximity, lower anesthetic volumes (10–15 mL) are used to minimize unintended spread. Potential complications include transient Horner’s syndrome if the sympathetic chain is affected or diaphragmatic dysfunction if the phrenic nerve is involved, particularly in patients with respiratory compromise.

Thoracic

The thoracic ESB is the most widely used variation, particularly for thoracic surgery, rib fractures, and breast procedures. The injection is typically performed at T5, though it can be adjusted based on the analgesic target. The anesthetic spreads cranially and caudally, often covering multiple thoracic dermatomes and sometimes extending into the paravertebral space, enhancing visceral pain relief.

This variation is a common alternative to thoracic epidural anesthesia, offering comparable analgesia with a lower risk of hypotension or motor blockade. Studies show it significantly reduces opioid consumption in patients undergoing thoracotomy or mastectomy. A volume of 20–30 mL is commonly used. While generally safe, potential risks include inadvertent vascular puncture or insufficient analgesia if the injectate does not reach the targeted nerves.

Lumbar

The lumbar ESB is used for lower back, abdominal, and lower extremity pain. It benefits patients undergoing lumbar spine surgery, hip procedures, or those with chronic lower back pain. The injection is typically placed at L3 or L4, allowing the anesthetic to spread along the lumbar dorsal rami and, in some cases, the lumbar plexus.

Compared to the thoracic variation, the lumbar ESB may have a more localized effect due to differences in fascial anatomy. However, it has been shown to provide effective analgesia for lumbar radiculopathy and postoperative pain following abdominal surgeries. A volume of 20–30 mL is often used, though adjustments may be needed based on patient anatomy. Potential complications include inadvertent spread to the psoas compartment, which could cause motor weakness if the femoral nerve is affected.