How are lumbar facet blocks administered for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

Intra-articular lumbar zygapophyseal joint blocks, as described by Bogduk et al, are performed with the patient lying prone. Upper lumbar facet joints originate in the sagittal plane; therefore, the joint space is usually evident on posteroanterior fluoroscopy with the patient prone. The lower lumbosacral zygapophyseal joints are oriented obliquely at an angle of approximately 45° to the sagittal plane.

To permit visualization of the joint space, the patient has to be rotated appropriately and supported in an oblique prone position or a C-arm fluoroscopy unit capable of tilting the x-ray beam. A 22-gauge or 25-gauge, 9-cm spinal needle is the most practical for accessing the target joint cavity. Finer needles enter the joint space more easily but are apt to stray during penetration of the back muscles. If this difficulty is encountered, then a double needle technique can be used, in which a large gauge needle is introduced to the target joint and a finer needle is passed through the larger needle to penetrate the joint capsule.

The operator relies on feel to determine when the needle enters the joint and limits penetration of the joint no farther than its center. Correct placement of the needle inside the midpoint of the joint is confirmed by injection of a small quantity of contrast medium (less than 0.3 mL) using a small syringe (2-5 mL) to minimize injection pressure. If the needle is inside the joint, the arthrogram smoothly outlines the smooth perimeter of the joint space. At this point in the procedure, the patient should be questioned in detail whether the character of pain that is perceived as a result of the dye injection is concordant to the pain for which treatment is being sought. Once intra-articular placement has been verified, LA can be used to ablate the pain and provide additional diagnostic verification. Addition of corticosteroids has been reported to provide therapeutic benefit; however, no more than a total of 1 mL of any solution combination should be injected.


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