Caudal anesthesia was described at the turn of last century by two French physicians, Fernand Cathelin and Jean-Anthanase Sicard. The technique pre-dated the lumbar approach to epidural block by several years.1 Caudal anesthesia, however, did not gain in popularity immediately following its inception. One of the major reasons caudal anesthesia was not embraced is the wide anatomical variations of sacral bones and the consequent failure rate associated with attempts to locate the sacral hiatus. The failure rate of 5% to 10% made caudal epidural anesthesia unpopular until a resurgence of interest in the 1940s, led by Hingson and colleagues, who used it in obstetrical anesthesia. Caudal epidural anesthesia has many applications, including surgical anesthesia in children and adults, as well as the management of acute and chronic pain conditions. Success rates of 98%–100% can be achieved in infants and young children before the age of puberty, as well as in lean adults.1 The technique of caudal epidural block in pain management has been greatly enhanced by the use of fluoroscopic guidance and epidurography, in which high success rates can be attained.
Unfortunately, clinical indications, and especially therapeutic interventions for the relief of chronic pain in individuals with failed back surgery syndrome, are often most prevalent in patients with difficult caudal landmarks. It has been suggested that traditional lumbar peridural block should not be attempted employing an approach requiring needle placement through a spinal surgery scar due to the likelihood of tearing the dura and the possibility of inducing hematoma formation over the cauda equina when blood from the procedure becomes trapped between the layers of scar and connective tissues.2 Under these circumstances, it is recommended that fluoroscopically guided caudal epidural block be performed in lieu of the traditional palpation approach. Alternatively, the use of ultrasound may be appropriate to identify the sacral hiatus, and this technique has recently been described. The second resurgence in popularity of caudal anesthesia has paralleled the increasing need to find safe alternatives to conventional lumbar epidural block in selected patient populations, such as individuals with failed back surgery syndrome.
The sacrum is a large triangularly shaped bone formed by the fusion of the five sacral vertebrae. It has a blunted, caudal apex that articulates with the coccyx. Its superior, wide base articulates with the fifth lumbar vertebra at the lumbosacral angle (see Figure 25–1A). Its dorsal surface is convex and has a raised interrupted median crest with four (sometimes three) spinous tubercles representing fused sacral spines. Flanking the median crest, the posterior surface is formed by fused laminae. Lateral to the median crest, four pairs of dorsal foramina lead into the sacral canal through intervertebral foramina, each of which transmits the dorsal ramus of a sacral spinal nerve (see Figure 25–1A). Below the fourth (or third) spinous tubercle, an arched sacral hiatus ...