Epidural steroid injections (ESI) are used to treat a variety of conditions that cause unrelenting back pain. In some cases, ESI can delay the need for surgery. Some estimates suggest that, between, 10%-20% of the population suffers from some sort of chronic back pain. There are many reasons someone might experience continued back pain – issues with facet joints, torn or inflamed ligaments, strained muscles, and irritated nerve roots. ESI treats all of these issues. For most people, ESI should result in a reduction of chronic back pain, disability and can even diminish the depression that tends to go along with this time of constant pain.
The spine consists a track of bones called vertebrae. They are stacked on top one another, leading from the pelvis to the base of the skull. They form a channel that protects the spinal cord. The vertebrae are composed of many structures. At the beginning is a solid, circular body connected to two transverse processes on either side by thin bony structures termed pedicles. The transverse processes are bony projections, on either side, where the muscles attach. These transverse processes are then connected to the back-facing protrusion that can be felt through the skin. Added to these, are two additional thin, bony structures called the lamina. This design leaves a hollow central clearing between the processes, the lamina, the pedicles and the vertebral body.
Each vertebra is separated by inter-vertebral discs composed of a tough, fibrous outer layer and filled with a soft, gelatinous inner layer of cartilage. These discs support the vertebrae and allow them to shift across one another. They facilitate the movement of the spine. Two vertebrae are connected to one another by two facet joints, or zygapophysials, located on either side of the bone. Facet joints connect the upward and create an opening at the side, between two connected vertebrae. These vertebrae are called the neural foramen. Through the neural formen, nerve roots exit the spine to peripheral tissues.
There are three ways to administer ESI. The interlaminar approach offers an injection into the back and directly between the thin laminar portions of two adjacent vertebrae. This is done to access the epidural space in the spinal cord. The transforaminal approach involves injection through the neural foramen at the side of two adjacent vertebrae, and this is done to directly target the epidural space near a nerve root. Finally, the caudal approach involves an injection through a structure known as the sacral hiatus. The sacral hiatus is located just above the tailbone. This approach is done to access the epidural space. Whatever the approach, during an ESI procedure, a radiologic technique known as fluoroscopy, a type of real-time x-ray, is used to assist the physician in guiding the needle to the proper site. Fluoroscopy makes ESI highly accurate.
ESI’s are guided toward the spot where the pain is believed to generate. Once appropriately positioned, a solution can be injected through the needle directly to the site to relieve pain and inflammation. This solution generally consists of an anesthetic, mixed with a long-acting steroid, and this has an anti-inflammatory effect on the irritated area. ESI’s are very effective in treating all manner of pain within the spine.
A herniated (slipped disc, as it is sometimes known), refers to the displacement of inter-vertebral disc material outside the borders of its joint. For reasons that are not completely understood, disc herniation may cause intense pain or very little pain. The pain results from the shifted disc material, or subsequent inflammation. This puts pressure on a nearby nerve or nerve root. This type of pain is termed radiculopathy. Depending on which level of the spinal cord is affected, pain can be felt in several areas: the back, neck, arms or legs, and compression can cause numbness and/or weakness in some circumstances.
ESI’s are most often performed when sciatica, or shooting leg pain, results from a herniated disk. A herniated disc compresses nearby nerve roots, causing systematic shooting pain along the path of the nerve. In the case of sciatica, the leg is specifically effected. Studies have shown that ESI’s provides effective short-term pain relief for up to 80% of patients and long-term pain relief for up to 75% of sufferers.
Even if a disc is not herniated or compressing a nearby nerve root, it can still cause pain. Sometimes, because the discs are innervated, irritation to the disc can cause what is known as “disogenic pain”. ESIs may provide significant relief for this kind of pain.
Spinal stenosis is a narrowing of the central vertebral channel through which the spinal cord passes. This causes compression of the spinal cord and limited movement of the spine. Stenosis can, also, cause a narrowing of the neural formen, which can lead to compression of specific nerve roots. Spinal stenosis is common with advancing age, and the compression of nerve tissue is a common cause of pain. Spinal stenosis if often associated with arthritis, disc herniation, spinal tumors and forms of spinal injury. ESIs are helpful in relieving pain from these conditions.