Caudal Epidural Steroid Injection: APA Pain Medicine Course

Learn all about caudal epidural steroid injections in this comprehensive pain medicine course by APA. Master the technique and improve patient outcomes.

The caudal epidural block, involving needle insertion through the sacral hiatus for medication delivery into the epidural space, is widely employed for surgical anesthesia and pediatric analgesia. It is also a popular method for managing various chronic pain conditions in adults. Initially introduced as a blind technique, the success rate in children exceeds 96%, but in adults, it was only 68–75%. Advances in imaging technologies like fluoroscopy and ultrasonography have improved the accuracy of caudal epidural blocks in adults.

Anatomy -

In the realm of caudal epidural block, recent reports have spotlighted anatomical features and variations crucial to the procedure's success and risk mitigation. A profound understanding of pertinent anatomy is required.

Sacral Cornua: Vestiges of the inferior articular processes of the fifth sacral vertebra, sacral cornua manifest as bony prominences at the sacrum's caudal end. Palpating these structures is integral to locating the sacral hiatus in the traditional landmark-based technique. However, palpability isn't uniform. Studies indicate that sacral cornua are bilaterally palpable in only 19%, unilaterally palpable in 25%, and bilaterally impalpable in 54% of isolated adult sacral bone. This variability, with palpability defined at a minimum height of 3mm, contributes to the high failure rate of the blind technique.

Sacral Hiatus: Formed by the non-fusion of lamina and spinous processes of lower sacral vertebrae, the sacral hiatus marks the sacral canal's caudal termination. Laterally flanked by two sacral cornua, the sacral hiatus may be palpable as a dimple. During caudal epidural block, accessing the sacral canal necessitates needle insertion into the sacral hiatus. Nevertheless, anatomical variations of the sacral hiatus may pose challenges or complications, such as dual puncture, during the procedure.

The mean anterior-posterior (AP) diameter of the sacral hiatus at its apex ranges from 4.6 ± 2mm to 6.1 ± 2.1mm, with a decrease observed with age. In clinical scenarios, an AP diameter at the apex of less than 3.7mm is linked to difficulties in blindly inserting a needle into the caudal epidural space. When ultrasound guides the procedure, challenges arise with an AP diameter at the apex below 1.6mm. Studies report incidences of short AP diameter, with less than 3mm in 8.77% and less than 2mm in 1%–6.25%. Extreme cases involve a completely closed sacral hiatus, preventing needle insertion, with an incidence of 2-3% in studies on dry human sacral bone.

The apex of the sacral hiatus is most commonly situated at the S4 level (65–68%), followed by the S3 and S5 levels (approximately 15% each), and the S1 to S2 level in 3–5% of cases. Complete agenesis of the posterior wall of the sacral canal is noted in 1% of cases. The higher the apex, the shorter the distance to the dural sac termination, potentially leading to accidental dural puncture. Conversely, a lower apex is associated with a shorter sacrococcygeal ligament (SCL), with lengths below 17.6mm linked to challenging blind caudal epidural blocks.

The dural sac typically ends between the S1 and S2 vertebrae, with the majority terminating at S2. In 1 to 5% of cases, the termination occurs at S3 or below. Among individuals with low back pain or sciatica, 1 to 5% exhibit a sacral Tarlov cyst, a perineural cyst communicating with the dural sac and filled with cerebrospinal fluid. Over 40% of these cysts are positioned at or below the S3 level. A lower termination of the dural sac or the presence of a Tarlov cyst increases the likelihood of dural puncture or intrathecal injection during caudal epidural block.

The distance between the termination of the dural sac and the apex of the sacral hiatus, a critical factor in assessing the risk of dural puncture, exhibits significant variation across ethnic groups. Studies report average distances such as 32 ± 12 mm in an Indian cadaver study, 60.3 ± 13.1 mm in a British study using magnetic resonance imaging (MRI), and 44.6 ± 11.8 mm in a Turkish study. Notably, this distance can be as short as less than 6 mm in some individuals, as indicated by these findings.

Indications for caudal epidural steroid injection -

1. Lumbar Disc Herniation: CESI may be recommended for individuals experiencing pain, numbness, or tingling due to herniated discs in the lumbar region.

2. Lumbar Radiculopathy: Conditions causing irritation or compression of spinal nerve roots, such as sciatica, can benefit from CESI to alleviate associated pain and inflammation.

3. Lumbar Spinal Stenosis: CESI may be considered for individuals with lumbar spinal stenosis, a condition characterized by the narrowing of the spinal canal, causing pain and discomfort.

4. Degenerative Disc Disease: CESI can be used to manage pain and inflammation associated with degenerative changes in the lumbar discs.

5. Post-Surgical Pain: Individuals experiencing persistent pain after lumbar spine surgery may be candidates for CESI as part of their pain management strategy.

6. Chronic Lower Back Pain: When conservative treatments fail to provide sufficient relief for chronic lower back pain, CESI may be considered to reduce inflammation and alleviate pain.

7. Neurogenic Claudication: Individuals with neurogenic claudication, often associated with lumbar spinal stenosis, may find relief from symptoms through CESI.

Contraindications for caudal epidural steroid injection -

1. Systemic Infections: Active systemic infections or local infections at the injection site can increase the risk of spreading the infection. In such cases, the procedure is typically postponed until the infection is resolved.

2. Bleeding Disorders: Individuals with bleeding disorders or those taking anticoagulant medications may be at an increased risk of bleeding at the injection site. The potential for excessive bleeding is a contraindication.

3. Allergy to Injected Medications: If a patient has a known allergy to any of the medications (such as corticosteroids or local anesthetics) used in the injection, it is a contraindication.

4. Uncontrolled Diabetes: Poorly controlled diabetes may increase the risk of infection and slow the healing process. Caudal epidural injections may be contraindicated in such cases.

5. Pregnancy: While there is limited evidence regarding the safety of caudal epidural steroid injections during pregnancy, it is often avoided unless the potential benefits outweigh the risks.

6. Local Anesthetic Allergy or Sensitivity: Allergic reactions or sensitivities to local anesthetics used in the injection are contraindications.

7. Spinal Abnormalities or Anomalies: Certain structural abnormalities or anomalies of the spine may make it technically difficult or risky to perform caudal epidural injections.

8. Unstable Medical Conditions: Individuals with unstable medical conditions, such as uncontrolled hypertension or heart failure, may be at increased risk during the procedure.

9. Recent Infections at Injection Site: Recent infections at or near the injection site, including skin infections, may be a contraindication.

About the Author -

Meet Dr. Debjyoti Dutta, a distinguished pain specialist and accomplished author with affiliations at Samobathi Pain Clinic and Fortis Hospital in Kolkata. Currently a registrar at the Indian Academy of Pain Medicine, Dr. Dutta specializes in musculoskeletal ultrasound and interventional pain management. Renowned for impactful publications such as "Musculoskeletal Ultrasound in Pain Medicine" and "Clinical Methods in Pain Medicine," he provides profound insights into effective pain management strategies. Beyond clinical roles, Dr. Dutta serves as a faculty member at Asian Pain Academy, playing a pivotal role in delivering top-notch pain management fellowship training in Kolkata, India. His dedicated efforts significantly contribute to the education and professional development of individuals in the field.