Caudal Epidural Injection

Acute or chronic low back pain or sciatica

Causes and findings:
• Disc lesion, acute nerve entrapment
• Central or bilateral pain in low back with or without sciatica or root signs
• Usually painful flexion and side flexion away from painful side and nerve root tension signs

Equipment:
Syringe - 1ml
Needle - 21G 1.5 inches (40mm) green
Kenalog 40 - 40 mg
Lidocaine - Nil
Total volume - 1 ml

Anatomy:
The spinal cord ends at the level of L1 and the thecal sac ends at S2 in most individuals. The aim of this injection is to pass a disinflaming solution through the sacral hiatus and up the canal so that it bathes the posterior aspect of the intervertebral disc, anterior aspect of the dura mater and any affected nerve roots centrally. The sacral cornua are two prominences that can be palpated at the apex of an equilateral triangle drawn from the posterior superior spines on the ileum to the coccyx. There is a thick ligament at the entrance to the canal. The angle of the curve of the canal varies widely and the placement of the needle reflects this.

Technique:
• Patient lies prone over small pillow
• Identify sacral cornua at base of imaginary triangle with thumb
• Insert needle between cornua and pass horizontally through ligament
• Pass needle slightly up canal adjusting angle to curve of sacrum
• Aspirate to ensure needle has not penetrated thecal sac or blood vessel
• Slowly inject solution into epidural space
• Keep hand on sacrum to palpate for swelling caused by suprasacral injection

Aftercare:
The patient lies prone for 10 min and then supine for a further 10 min. He or she can continue to do whatever is comfortable and is reassessed about 10 days later. If the injection has helped it can be repeated at 1- or 2-week intervals as long as improvement continues. The causes of the back pain should then be addressed - weight, posture, work positions, lifting techniques, exercise, abdominal control, etc.

Comments:
Occasionally the canal is difficult to enter. This might be because of a bifid or very small canal or because the angle of the sacrum is very concave. Reangulation
of the needle might be necessary. If clear fluid or blood is aspirated at any point the procedure is abandoned and attempted a few days later. If the patient feels faint or dizzy during the injection, stop injecting and wait for the symptoms to go. If they do not, abandon the procedure. Caudal epidural is safe provided1 3 7:
• there is no allergy to local anaesthetic (not used in this method)
• there is no local sepsis
• the patient is not on anticoagulant therapy

Alternative approach:
If the affected level is higher than the common L5/S1 level, more volume may be required to reach these levels. In this case we recommend addition of up to 10 ml of normal saline, depending on the level of the lesion and the size of the patient.