Spinal injections are used in two ways. First, they can be performed to diagnose the source of back, leg, neck, or arm pain (diagnostic). Second, spinal injections are used as a treatment to relieve pain (therapeutic).
Most spinal injections are performed as one part of a more comprehensive treatment program. Simultaneous treatment nearly always includes an exercise program to improve or maintain spinal mobility (stretching exercises) and stability (strengthening exercises) (AAOS, 2015).
Back pain is the number-one reason people visit their doctors, and epidural steroid injections have been a mainstay of treatment for short-term pain relief for decades. The injections seem to be most effective for people who have “radicular” pain, or pain that radiates from the spine to a leg or an arm, caused by a herniated disc.
For many people, back pain goes away on its own or with nonsurgical treatments. Epidural steroid injections shouldn’t typically be used as a first-line therapy for back pain relief, but that doesn’t mean they can’t play a role in treating pain. But injections won’t cure the underlying cause of back pain, and they provide only temporary relief. Unfortunately, in many cases, chronic back pain can’t be cured, but must instead be managed, like other chronic conditions—and patients must have realistic expectations of what epidurals can do.
Types of Spinal Injections
Epidural injections are used to treat pain that starts in the spine and radiates to an arm or leg. Arm or leg pain often occurs when a nerve is inflamed or compressed (“pinched nerve”).
Epidural injections involve injecting an anesthetic and an anti-inflammatory medication, such as a steroid (cortisone), near the affected nerve. This reduces the inflammation and lessens or resolves the pain. This type of epidural injection is a therapeutic one.
Sacroiliac Joint Injections
SI joint injections are similar to facet joint injections in many ways. The SI joints are located between the sacrum and ilium (pelvic) bones.
Problems in the SI joints have been shown to cause pain in the low back, buttock, and leg. Typically, one joint is painful and causes pain on one side of the lower body. It is less common for both SI joints to be painful at the same time.
This joint can also be injected for both diagnostic and therapeutic purposes. Anesthetizing the SI joint by injection under X-ray guidance is considered the gold standard for diagnosing SI joint pain. A diagnostic injection of the sacroiliac joint with anesthetic should markedly diminish the amount of pain in a specific location of the low back, buttock, or upper leg.
A therapeutic injection will typically include a steroid medication, with the goal of providing longer pain relief.
Facet Joint Injections
Facet joint injections can also be done for both diagnostic and therapeutic reasons. These types of injections are often used when pain is caused by degenerative/arthritic conditions or injury. They are used to treat neck, middle back, or low back pain. The pain does not have to be exclusively limited to the midline spine, as these problems can cause pain to radiate into the shoulders, buttocks, or upper legs.
For diagnostic purposes, facet joints can be injected in two ways: injecting anesthetic directly into the joint or anesthetizing the nerves carrying the pain signals away from the joint. If the majority of pain is relieved with anesthetic into the joint, then a therapeutic injection of a steroid may provide lasting neck or low back pain relief.
If anesthetic injections indicate that the nerve is the source of pain, the next step is to block the pain signals more permanently. This is done with radiofrequency ablation, or damaging the nerves that supply the joint with a “burning” technique.
Provocation discography is a type of spine injection done only for diagnosis of pain. It does not have any pain relieving effect. In fact, it is designed to try to reproduce a person’s exact or typical pain. This is to find the source of longstanding back pain that does not improve with comprehensive, conservative treatment. Discography is performed much less commonly than the other types of spinal injections reviewed above. It is often used only if surgical treatment of low back pain is being considered. The information gained from discography can assist in planning the surgery.
Discography involves stimulating and “pressurizing” an intervertebral disc by injecting a liquid into the jelly-like center (nucleus pulposus) of the disc. More than one disc is injected in order to distinguish a problem disc from one without symptoms. Criteria are used to identify a painful disc by provocation discography, including the type and location of pain and the appearance of the disc on an X-ray after the procedure.
Patients may be asked to change into a hospital gown, which allows for access to clean the injection area and to allow the physician to easily visualize the injection site. An epidural steroid injection usually takes between 15 and 30 minutes and follows a relatively standard protocol:
- The patient lies flat on an X-ray table or with a small pillow under their stomach to slightly curve the back. If this position causes pain, the patient can be allowed to sit up or lie on their side in a slightly curled position.
- The skin in the low back area is cleaned and then numbed with a local anesthetic similar to what a dentist uses.
- Using fluoroscopy (live X-ray) for guidance, a needle is inserted into the skin and directed toward the epidural space. Fluoroscopy is considered important in guiding the needle into the epidural space, as controlled studies have found that medication is misplaced in many (> 30%) of epidural steroid injections that are done without fluoroscopy1.
- Once the needle is in the proper position, contrast is injected to confirm the needle location. The epidural steroid solution is then injected. Although the steroid solution is injected slowly, most patients sense some pressure due to the amount of the solution used (which in lumber injections can range from 3mL to 10mL, depending on the approach and steroid used). The pressure of the injection is not generally painful
- Following the injection, the patient is monitored for 15 to 20 minutes before being discharged home.