September/October 2008
Volume 4, Issue 5

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Facet Joint Nerve Block Injection

An Original Contribution by Shamolie Wyckoff, M.D.

Over the past 70 years, various studies have investigated the role of facet joints in back pain. From these studies, facet joints have been recognized as a potential primary source of low back pain separate from spinal nerve compression. There is also evidence that Facet Joint Nerve Block therapy and radiofrequency neurotomy of the lumbar medial branch is effective in managing symptoms of low back pain.

Each vertebra is connected by two facet joints –one on each side. Also called zygoapophyseal joints, the facets are synovial joints lined with hyaline cartilage. These joints allow the spine to flex, extend, and rotate. The joint capsule can undergo extensive stretch which allows them to withstand significant loading and serves to limit rotation and bear some of the axial compressive forces of the spine. Degenerative processes such as osteoarthritis can cause inflammation and irritation of surrounding tissues and sensory nerve endings of the joint. Once this occurs, it may present as back pain. The facet joint can undergo erosions, bony spurs, bony sclerosis, and loss of cartilage as well as sustain injuries to the capsule including tears and hemorrhages which contributes to the condition known as facet syndrome. It was originally defined as lumbrosacral pain with or without sciatic pain but is now known to be described as pain originating in the facet joint radiating to low back, buttock, and thighs.

Patients usually complain of axial back pain with radiation into the buttock, down the thigh and can extend to the foot. Some have noted referred pain has been even to the groin and the greater trochanter. Certain positions such as extension, rotation and lying prone worsen pain from facet syndrome.

Current diagnostics and treatment of chronic low back pain that may be secondary to facet syndrome include Facet Joint Nerve Block or also called medial branch blockade. This is performed in order to diagnose pain originating from the facet and to identify those patients that would benefit from a medial branch radiofrequency ablation. Facet joints are innervated by the medial branch of the dorsal ramus. Studies have shown that the facet joint capsule itself is richly innervated with nerve endings. The facet nerve block involves blocking the innervation of the posterior capsule of the joint. The joint may be considered to be the source of pain if the pain is relieved by medial branch blockade. To eliminate false positives and consider radiofrequency neurotomy, one diagnostic block and one confirmatory block using local anesthetics on two separate occasions is performed and must have 50% pain relief.

Each facet joint is innervated by the medial branch at that level and below that level. To successfully block the innervation of a lumbar facet joint, it is necessary to block the 2 medial branches that supply the joint. Each facet joint is innervated by the medial branch at that level and below that level therefore the injections are performed above and below the level of a given facet joint. Exceptions to this are in the thoracic and lumbar spine where the joints are supplied by the medial branch from above and at the level. For example, the L4-5 facet joint is innervated by the L3 medial branch and L4 medial branch.

The posterior primary ramus branch of the exiting segmental nerve divides into lateral, intermediate, and medial branches as soon as it exits the foramen. The medial branch passes caudally and slightly dorsally, adhered to the periosteum by the mammiloaccesory ligament, hooking medially around the caudal aspect of the superior articular process of the facet joint. The medial branch nerve is located at or slightly superior to the level of the transverse process and just lateral to the medial border of the superior articular process.

Facet Joint Nerve Block is performed at the junction of the superior articular and transverse processes. The patient is laid prone with pillow under stomach and sterile preparation is used. An AP view is obtained to center the junction of transverse process and superior articular process. It is then obliqued 25-30 degrees to the side of back being treated in order to obtain the “Scotty dog” view. A skin wheal is made with 1% lidocaine and using a 22 gauge 3.5inch needle, it is advanced medially, anteriorly and caudally to hit periosteum(bony endpoint) at the junction of the superior articular process , base of the transverse process and the pedicle. Use of contrast dye will ensure, correct placement and confirm the needle is not intravascularly placed. Prior to injection, the bevel opening should be medial and slightly inferior to reduce lateral and superior flow to the intervertebral foramen. 0.3-0.5cc of anesthetic solution is then injected.

When performing Cervical Facet Joint Nerve Injection, the medial branch is blocked where it crosses the midportion of the articular pillar as viewed fluoroscopically in lateral projection.

Precautions to this procedure include patients on warfarin or other anticoagulants. Aspirin and NSAIDs are considered safe if stopped 5-7 days prior to procedure. These procedures are not indicated in those that have a coagulopathy, pregnancy, systemic infection, or severe allergy to any of the medications. Complications that may occur include infection, bleeding, increased pain, trauma, and inadvertent injection.

Currently, evidence for facet joint nerve blocks in managing chronic low back pain has shown to be moderate for short term and long term relief. It continues to play an important role in the diagnosis and treatment of chronic low back pain in patients.§