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Dr. Frey
Dr Schmidt
Dr. Schmidt
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Telephone: (303) 762-0808
Fax: (303) 762-9292
colorado spine logo
Telephone: (303) 762-0808
Fax: (303) 762-9292
Contact Us for Appointment


Making an Appointment
Phone, Forms, Directions

Denver Spine Surgery Office


2535 S Downing Street
Denver CO 80210

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Understanding Medical Tests: Diagnostic Spinal Injections

X-rays, CT Scans, and MRIs provide excellent imaging of different spinal disorders. However, these tests do not show or reproduce pain. Spinal injections, typically used to control pain, can be used diagnostically to locate the pain source. Diagnostic spinal injections include discography (discogram), selective nerve root blocks (SNRB), sacroiliac joint injections, facet joint injections, and medial blocks.

Typically, these injections only offer 6 to 12 hours of relief from specified symptoms, which then is a diagnostic result. Please keep in mind, that if you experience dramatic relief, but relief lasts for only 6 hours, it is still a positive correlative result.

The type of diagnostic spinal injection your doctor chooses is based on your medical history, physical and neurologic examination, and other test findings.The type of diagnostic spinal injection your doctor chooses is based on your medical history, physical and neurologic examination, and other test findings.


Discography is a specific test to tell if a damaged or abnormal disc is causing pain. This is not a routine test. It may be performed prior to spinal disc surgery to determine which disc levels will be treated.

Discography, an invasive procedure, is performed using fluoroscopy (similar to x-ray, except in real time). To help you relax during the procedure, mild sedation may be administered. However, we cannot completely sedate, or put you to sleep, as you need to be alert enough to report what you feel to our team during the injection. An antibiotic may also be given intravenously before and after. You may be positioned, with pillows for support and comfort, on your side, or in another position. The injection sites are cleansed using an antiseptic and an anesthetic numbs the skin.

Using fluoroscopic guidance, a contrast agent (dye) is injected into the center of select discs. Contrast enhances the disc’s anatomical characteristics and may spread outside the disc if abnormal. The dye may irritate a damaged, symptomatic disc. Pressure measurements from inside the disc are collected too. As each disc is injected with contrast, you are asked to describe your symptoms, such as the intensity and type of pain experienced.

Please understand that the purpose of this test is not just to make you hurt! Rather, the purpose is to recreate symptoms familiar to your unique pain pattern.

When discography replicates your symptoms, it is called a positive discogram. If symptoms are not replicated, it is a negative discogram. Discography can be uncomfortable and symptoms are temporary.

The procedure may take 45-minutes, depending on the number of discs examined.

Lumbar DiscographyDiscogram: Fluoroscopy view shows the intact disc above and the degenerated disc below.

Selective Nerve Root Block (SNRB)

A selective nerve root block is performed to determine if a specific spinal nerve is the source of pain. A SNRB is performed to diagnose cervical (neck) or lumbar (low back) radiculopathy (irritation and inflammation of a nerve root).

Using fluoroscopic guidance, steroid medication (a strong anti-inflammatory) is injected at a specific nerve root If the injection reduces symptoms, the pain source is identified. The test takes 15- to 30-minutes per spinal level.

Sacroiliac Joint Injection

The sacroiliac joint, located in the lower spine above the tailbone, is the largest joint in the spine. Inflammation of the sacroiliac joint can cause low back and buttock pain.

Using fluoroscopy, local anesthetic and steroid medication is injected into the sacroiliac joint. If pain is relieved, it could mean the joint is the pain generator.

Sacroiliac Joint
  1. Sacroiliac Joint
  2. Coccyx (tailbone)
  3. Sacrum

Facet and Medial Blocks

Joint inflammation between spinal bones can cause back pain. Facet and medial blocks involve injecting steroid medication into one or more joint structures to determine if a specific joint generates pain.

Facet Joint

  • A facet joint block is an injection of local anesthetic and steroid medication into the joint.
  • A medial block uses similar medication injected outside the joint space near the nerve that feeds a specific joint.
  • Both injection procedures are performed using fluoroscopy.

If pain is relieved, it could mean that the joint or medial nerve generates pain.

Patient Preparation: At Home

Below is a short list of common instructions. After you are seen at Colorado Comprehensive Spine Institute (CCSI), our doctor will provide a more specific list for you.

  • Stop blood-thinning medication 5-days prior to the test
  • Do not take any aspirin product 14-days prior to the test
  • Stop anti-inflammatory medication 5-days prior to the test
  • Stop pain medication 4-hours prior to the test
  • Do not eat or drink 4-hours prior to the test
  • Arrange for someone to drive you home

Patient Preparation: At the Medical Facility

  • The medical staff will review your history, condition, medications, allergies, and other pertinent information.
  • You change into a gown and lie down in a hospital bed.
  • A nurse monitors your heart function (EKG), blood pressure, blood-oxygen levels (finger oximeter), and other vital signs before, during, and after the procedure.
  • Medication is administered to relax you. Light intravenous sedation may be given. Diagnostic spinal injections require you to be awake to respond to questions during the procedure.

What to Expect During the Procedure

  • The procedure is performed in a sterile setting similar to an operating room.
  • The injection site is cleaned and draped. Skin numbing medication is injected into and around the procedure site.
  • Before proceeding, the fluoroscopic C-arm is positioned over you. Fluoroscopic guidance is used during the procedure to guide the needle into the proper position.
  • Diagnostic injections may include an anesthetic, steroid, and/or antibiotic.
  • The goal of a diagnostic injection is to replicate your typical discomfort (symptoms). Your feedback helps to identify the cause of pain.

After the Procedure

  • You are moved to the recovery area where the medical staff continues to monitor your vital signs.
  • You may be discharged home in 30 to 60-minutes with written instructions.
  • The area around the injection site will feel numb. Relief from typical symptoms may last for 6-hours following the injection.
  • Steroids may cause side effects that include blurred vision, frequent urination, increased thirst and change in blood sugar levels, especially in diabetic patients. If these side effects become bothersome or worsen, please call our office.
  • If fever, chills, increased pain, weakness or loss of bowel/bladder function occurs, seek immediate medical attention.
  • Please follow-up with your doctor for test results.

Possible Complications

A facet and medial block, like other medical procedures, may present risks. Complications include risk of infection, low blood pressure, headache, and injury to nerve tissue.

Patient Restrictions

Some patients should not undergo a facet and medial block. Restrictions include:

  • Allergy to the contrast medium and/or drugs to be injected
  • Anemia
  • Significant asthma
  • Bleeding problems
  • Infection
  • Kidney disease
  • Pregnant or breast-feeding
  • Severe spinal abnormality


Diagnostic injections are important to help identify the source of pain. Although these procedures are often uncomfortable, our staff is dedicated to making your procedure as comfortable as possible.


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© 2004-2022 Colorado Comprehensive Spine Institute

LastUpdate: 2016-12-20 22:14:26

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