Caudal epidural steroids are most commonly considered for patients with chronic low back pain with radicular pain secondary to disc herniation or radiculitis who have not responded to conservative modalities of treatment. The caudal approach is especially appealing in postlaminectomy patients with post-lumbar laminectomy syndrome or sacral involvement or those who have bilateral and multilevel pathology. These injections are also performed for patients with chronic axial or discogenic pain and spinal stenosis [13, 23].

Contraindications for caudal epidural injections can be divided into absolute and relative. Accordingly, the known risks of epidural steroids must be weighed against any potential benefit. Ideally, patients should be actively involved in the decision-making process.

A written medical note with detailed neurologic history, physical examination, and radiographic reports including a working diagnosis should be in the chart and reviewed immediately prior to the procedure.

Written informed consent should be completed documenting a discussion of the options, potential benefits, and potential risks.

Intravenous access should be established and appropriate monitoring should be applied and maintained throughout. Accordingly the presence of all necessary equipment including resuscitation equipment should be confirmed.

The patient is then placed in a prone position, with one pillow under their head and one under their lower abdomen to reduce spinal lordosis. They are instructed to abduct their heels while keeping their toes together; this internal rotation ensures relaxation of the gluteal musculature. In obese patients, the gluteal cleft may be separated by attaching a broad band of sticky plaster between the skin of the buttocks and the operating table. Strict sterile technique must be employed and a large area should be prepped with an antiseptic solution that is approved for neuraxial procedures. It is also important to keep accurate records of the procedure and any unexpected events or complications.

For the procedure, some clinicians recommend a 22-g spinal needle to minimize procedural pain, whereas the authors suggest a Tuohy needle and catheter in order to deliver the injectate more cephalad in the sacral canal. Care should be taken not to introduce free skin particles with epidermal cells into the spinal canal, due to the potential risk of epidermoid tumors [6]. There are wide variations in the volume of the sacral canal; we recommend a preparation of corticosteroids with local anesthetic agents and/or normal saline in volumes ranging from 10 to 15 mL.

Caudal epidural injections can be performed using fluoroscopy, ultrasonography, or a landmark-based technique. These techniques are discussed below. It should be noted that in adults, the rate of inaccurate placement with landmark-based technique can be as high as 35 % in experienced hands [14, 30]. In addition, intravascular placement rates of 14 % and extra-epidural placement rates of 9 % have been reported. There are controlled studies that suggest “blind” caudal injections are not more effective than epidural injections of normal saline either for short-term outcomes or in the long term [5].

Fluoroscopically guided caudal epidural anesthesia is considered the gold standard by most clinicians. Despite the lack of strong evidence that fluoroscopically guided injections are more effective, they are undoubtedly safer than a blind injection, and as such the use of C-Arm fluoroscopy makes rational sense [5].

It is recommended to start with the C-arm in an AP (anterior–posterior) orientation to ensure that the patient’s pelvis is not laterally tilted. This is especially true in obese patients. Subsequently, in the lateral view, the sacral hiatus will usually be visible as a translucent opening toward the base of the caudal canal. Identification of the coccyx immediately caudad can also help with localization of the hiatus. Similarly, the clinician may palpate the coccyx and sacral cornua to help identify the point of needle insertion.

After adequate local anesthesia infiltration, an 18-gauge needle may be used to perforate the skin. At this point, the desired needle (spinal or Tuohy) is pushed through this perforation and advanced toward the hiatus. AP and lateral fluoroscopic images are taken to confirm the depth and direction of needle advancement. Once the needle is visualized just inside the canal, the Tuohy needle can be rotated 180° as necessary to enable smooth advancement. It should not be advanced beyond the S3 foramen to avoid damaging the sacral nerve roots and to minimize the risk of subarachnoid or subdural placement.

After negative aspiration for blood and CSF, appropriate myelographic quality radiocontrast material should be injected under live fluoroscopy. If venous runoff is noted, the needle tip can be withdrawn and moved until the venous runoff is no longer seen. If CSF is aspirated or a subdural or subarachnoid pattern is seen, the procedure should be terminated and repeated at a later date. Under normal circumstances, when contrast media is injected into the epidural space, a classic “Christmas-tree” pattern will be visualized within the bony canal. It should be noted that adhesions will limit dye spread. Subarachnoid dye spread will be noted centrally and extend significantly cephalad with only a small volume. Subdural injections will tend to be more patchy, and the contrast spread will not be as wide or predictable as subarachnoid pattern [5, 25]. Images of stages of a fluoroscopically guided caudal injection are seen below in Fig. 44.4. Examples of a wide variety of contrast spread patterns have been published elsewhere [28].

After final placement of the needle or catheter and repeat negative aspiration, local anesthetic should be injected as a test dose prior to injection of the full dose of medication in aliquots. The patient may report pressure upon injection which should be halted until this pain has dissipated. Upon completion of the procedure, the stylet should be reinserted prior to needle removal. A sterile adhesive bandage should also be applied over the puncture site.

Ultrasonography in the field of pain medicine continues to grow as the technology advances. It is noninvasive, safe, simple to use, does not involve exposure to radiation, and has the potential to provide real-time images.

The potential benefit of ultrasound imaging for caudal epidural steroids was first described in 2003 [17]. The investigators found it to be especially helpful in moderately obese patients who were unable to assume the prone position. It is also useful when faced with decreased bone density, gas or feces in the rectum, or where fluoroscopy is not available or contraindicated [15, 20, 22].