Procedures · Fluoro and special studies2 min read5-question check
Myelography, lumbar puncture and joint injections
Only nonionic contrast labeled for intrathecal use goes into the spinal canal. Keep the chin extended when the head tilts down.
Lumbar puncture
A lumbar puncture places a needle into the subarachnoid space below the end of the spinal cord, which ends near L1 to L2 in adults. The usual level is L3 to L4, or L2 to L3. The patient may lie in lateral decubitus with the knees drawn up, sit leaning forward, or, under fluoroscopy, lie prone with a pad under the abdomen. Each flexes the spine and opens the spaces between spinous processes. The puncture may collect CSF, measure pressure, or deliver contrast.
Myelography
A myelogram shows the spinal canal, nerve roots and cord after contrast is injected into the subarachnoid space. It is often used when MRI is not possible. Only nonionic iodinated contrast labeled for intrathecal use is allowed, such as iohexol. Ionic contrast in the canal can cause seizures and death. The table tilts to move the contrast, so attach shoulder supports and a footboard. When the head goes down, keep the chin hyperextended to keep contrast out of the skull. Contraindications include blood in the CSF, raised intracranial pressure, and a lumbar puncture within about 2 weeks. Afterward, keep the head elevated 30 to 45 degrees and encourage fluids.
Injections and arthrography
Fluoroscopy also guides epidural steroid, facet and sacroiliac injections. A small amount of contrast confirms needle position before medication goes in. Arthrography puts contrast into a joint. Worked example, a shoulder MR arthrogram: the skin is prepped and draped, lidocaine numbs the skin, and the needle enters the joint under fluoroscopy. Any fluid is drawn off first. A little iodinated contrast confirms placement, then dilute gadolinium is injected, and the patient goes to MRI promptly. A conventional or CT arthrogram uses iodinated contrast.
Your role
The physician obtains consent. You confirm identity, allergies and blood thinners, join the time-out, set up the tray, and run the fluoroscope with pulsed, collimated, low-dose technique. Only the draped table top is sterile. Face the field, never reach over it, open packs away from it, and treat anything doubtful as contaminated.
Clinical Example
A patient with a pacemaker needs a lumbar myelogram. The radiologist punctures at L3 to L4 with the patient prone, injects iohexol labeled for intrathecal use, and tilts the table. You keep the chin extended during the head-down tilt and later send the patient to recovery with the head raised 30 degrees and fluids encouraged.
Common Mistakes
- Thinking any iodinated contrast is safe for intrathecal use.
- Letting the chin flex during a head-down tilt, which lets contrast flow toward the skull.
- Reaching across a sterile tray or touching drapes below table level.
- Forgetting that a recent lumbar puncture is a contraindication to myelography.
Why It Matters
Intrathecal contrast errors can kill, and the 2027 specifications add injection procedures. Expect questions on contrast type, positioning, aftercare and sterile technique.
Key Relationships
- Intrathecal contrast → nonionic, labeled for intrathecal use, never ionic
- Head-down tilt → chin hyperextended → contrast stays out of the skull
- After myelogram → head up 30 to 45 degrees, fluids
- Injection → small amount of contrast confirms needle position