Diagnostic Injections

Diagnostic methods such as CT scans, MRI scans, and simple X-rays provide excellent imaging of spinal pathology, but they cannot measure pain. The injection of a local anesthetic can reduce pain and help diagnose or confirm the cause of the pain. Spinal diagnostic injections include discography, nerve blocks, sacroiliac joint injections, and small joint injections.

The type of diagnostic injection depends on the patient’s medical history, physical and neurological examination, as well as findings from CT and MRI scans. In the spine, the typical causes of pain are nerves and intervertebral discs. For example, a herniated disc may press on a nerve, causing pain in the buttock and leg, or if in the neck, pain in the shoulder and arm. In such cases, a diagnostic injection aims to numb the affected nerve, confirming its involvement and providing pain relief.

Discography

Discography helps determine if a specific disc is the cause of pain. It is not a routine test, as it is invasive and is only scheduled when surgery is being considered for lower back pain.

During discography, a contrast agent is injected into the disc under fluoroscopic guidance (continuous X-ray imaging of the spine). The contrast agent reveals the anatomical characteristics of the disc, including tears in the annulus fibrosus. Additionally, discography can induce pain—if the test is positive, it should reproduce the patient’s symptoms. If it does not fully replicate the symptoms, it is considered negative, although this does not necessarily mean the disc is not the source of pain. The procedure takes approximately 30 minutes to 1 hour, depending on the number of discs examined. Infection is a rare but possible complication, so all patients receive antibiotics before the procedure.

Selective Nerve Block

A nerve block is performed to determine whether a specific spinal nerve root is causing pain. It can help diagnose both cervical and lumbar radiculopathy (irritation of a spinal nerve). Under fluoroscopic guidance, a local anesthetic and corticosteroid are injected near the nerve root. If this injection reduces or completely alleviates the patient’s pain, the source of the pain has been identified and confirmed. The test takes approximately 15-20 minutes per nerve.

Small Joint Block

Injecting a local anesthetic and corticosteroid into the small joints of the spine helps diagnose whether the joints themselves are the source of pain. The anesthetic provides immediate relief and diagnosis, while the corticosteroid offers long-term pain reduction.

A similar procedure, called a “medial branch block,” targets the posterior branch of the spinal nerve root. The injection, guided by fluoroscopy, is administered next to the small joint with a local anesthetic. If the pain subsides, this confirms that the small joint or the posterior nerve branch is responsible for the pain.

Sacroiliac Joint Injection

The sacroiliac joint is the largest joint in the spine, connecting the sacrum with the two ilium bones of the pelvis. It is responsible for 10-15% of lower back pain cases and can cause pain in the lower back or buttock. Under fluoroscopic guidance, a local anesthetic and corticosteroid are injected into the sacroiliac joint. Pain relief confirms that the sacroiliac joint is the source of the pain.