Ultrafluoro guided caudal epidural injection: An innovative blend of two traditional techniques.

Sir,

Epidural steroid injection (ESI) is the commonest interventional pain procedure performed worldwide. Caudal, transforaminal and interlaminal are the approaches available to access the epidural space. The caudal approach has the advantages of medication delivery atleast in part to anterior epidural space (unlike interlaminar, [Figure 1]) and reduced complication rates.[1] Lumbar radiculopathy and lumbar canal stenosis are the most common indications for performing caudal ESI.[2] Blind unguided caudal ESI is associated with significant failure rates (20-38%) and fraught with complications.[34] Therefore, image guidance has become a norm rather than exception. Fluoroscopic guidance with contrast injection has decades of experience, literature support and is considered as the gold standard.[1234] The postulated advantages include ease of identification of sacral hiatus, accurate needle placement under vision, presence of a radiological end point for final tip position (S3) and tracking the contrast spread. However significant radiation hazard and associated biological side-effects to patient, physician as well as bystanders prevails during its usage. Radiation exposure to gonads of reproductively active age group is a particular concern. Ultrasonography (USG) is a relatively new imaging modality increasingly exploited for various image guided interventions. The advantages include portability, radiation free, ability to conduct procedure in unusual patient positions and unlike fluoroscopy, providing a clear view of sacrococcygeal membrane and real time passage of needle through it.[5] However disadvantages include difficult anatomic landmark identification in obese, inability to identify insertion depth, intravascular (5-9%)/intrathecal injection and learning curve in novices.[34] The authors have devised an imaging guidance protocol that embrace the advantages of both imaging modalities, counterbalances each other's disadvantages and have termed it as “ultrafluoro guided caudal injection.” The imaging protocol involves using USG as the primary imaging modality with fluoroscopic confirmation of correct needle tip position and dye spread.

Figure 1

Caudal epidural with anterior epidural dye spread in lateral view

Placing the patient in prone position with a pillow underneath.

Sterile cleaning and draping including placing 5-12 MHz linear transducer probe in sterile sheath with application of sterile jelly.

Scanning sacrococcygeal region in longitudinal and horizontal axis for identification of sacrococcygeal membrane and sacral cornu.

Employing longitudinal section with in-plane technique for needle insertion and passage through sacrococcygeal membrane into epidural space.

Taking an anterio-posterior fluoroscopic view and confirming final tip position below S3.

Omnipaque dye injection under fluoroscopic control and noting epidural spread, its pattern and extent.

Injection of 0.5% lignocaine with 40-80 mg methylprednisolone after obtaining epidurogram.

We conclude by saying that the USG and fluoroscopy should be considered complementary rather than an alternative to one another as their combined usage is associated with USG reduced radiation exposure, USG ability to conduct procedure in unusual patient positions, Fluoro identifying correct needle insertion depth; contrast spread as well as ruling out intravascular [Figure 2] or intrathecal contrast spread. In an era of increasing consumerism, peer and medico-legal scrutiny, multimodal imaging protocol may prove to be a safer alternative compared to the traditional practice of unimodal guided pain interventions.

Figure 2

Caudal epidural with intravascular dye spread