Epidural steroid injections are an important therapeutic modality employed by spinal surgeons in the treatment of patients with chronic low back pain with or without lumbar radiculopathy. The caudal epidural is a commonly used and well-established technique; however, little is known about the segmental level of pathology that may be addressed by this intervention. This prospective study of over 50 patients aimed to examine the spreading pattern of this technique using epidurography. The effect of variation in Trendelenburg tilt and the eradication of lumbar lordosis on the cephalic distribution of the injectate were investigated. 52 patients with low back pain and radiculopathy underwent caudal epidural. All had 20 ml volume injected, comprised of 5 ml contrast (Ultravist™ Schering) 2 ml Triamcinolone (Adcortyl™ Squibb) and 13 ml local anaesthetic (1% lignocaine). Patients were randomised to either 0° or 30° of Trendelenburg tilt, as referenced from the lumbar spine. Patients were further randomised to presence or absence of lumbar lordosis, which was eradicated using a flexion device placed beneath the prone patient. A lateral image of each sacrum was obtained, to identify variations in sacral geometry particularly resistant to cephalic spread of injectate. The highest segment reached on fluoroscopy was recorded post injection. Fifty-two patients with a mean age of 50 years underwent caudal epidural. Thirty-one were in 0° head tilt, with 21 in 30° of head tilt. In each of these groups, 50% had their lumbar lordosis flattened prior to caudal injection. The median segmental level reached was L3, with a range from T9 to L5. Eradication of lumbar lordosis did not significantly alter cephalic spread of injectate. There was a trend for 30° tilt to extend the upper level reached by caudal injection (p = 0.08). There were no adverse events in this series. Caudal epidural is a reliable and relatively safe procedure for the treatment of low back pain. Pathology at L3/4 and L4/5 and L5/S1 can be approached by this technique. Although in selected cases thoracic and high lumbar levels can be reached, this is variable. If pathology at levels above L3 needs to be addressed, we propose a 30° head tilt may improve cephalic drug delivery. The caudal route is best reserved for pathology below L3.
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