Facet Joint Injection

Anatomy and Physiology

The facet joint (zygapophyseal joints) are located throughout the spine and vary in size and shape depending on the vertebral level.[5] They are synovial joints formed by the articular processes between two adjacent vertebrae. The superior vertebrae provide the inferior articular process, and the inferior vertebrae provide the superior articular process.[2] Additional features include the articular cartilage overlying the facet of each articular process, followed by a layer of the synovial membrane and a tough outer fibrous layer overlying the membrane.[5] It is estimated that the joint space has a capacity of 1 to 2 mL.[6] 

The facet joint has many functions, including limiting excessive motion, distributing the axial load, and preventing displacement from forward and rotational movements of the intervertebral joint. Facet joint innervation comes from the medial branch of the posterior ramus of the spinal nerve. With each facet joint, sensory information is provided through dual innervation from the spinal nerve at the same level and one level above.[2]

It is estimated that facet joint pain is the source of pain in up to 67% of patients with neck pain, 48% of patients with thoracic pain, and up to 45% of patients with low back pain.[2] Due to the rich innervation of the synovium, it is thought that pain arising from the facet joint stems from injury or inflammation from degenerative arthritis, capsular distension or defects, instability, and impinged nerves secondary to osteophytes.[4][7] 

Nociceptive nerve fibers, autonomic nerve fibers, substance p nerve fibers, and inflammatory mediators such as prostaglandins and cytokines have all been implicated in playing a role in facet joint pain. Amongst the different types of facet joint pain etiologies, degenerative osteoarthritis is the most common cause. Other causes of facet joint pain include degenerative spondylolisthesis, rheumatoid arthritis, ankylosing spondylitis, and septic arthritis.[6]

Indications

Indications for diagnostic facet joint injections include strong suspicion for the pain of facet joint etiology (focal tenderness over the facet joint, pain in response to hyperextension, rotational movement, or bending laterally, leg pain not extending below the knee), chronic low back pain, neck pain not relieved with conservative management, low back pain with normal imaging, neck pain in the setting of a whiplash injury, post-laminectomy syndrome without evidence of arachnoiditis or recurrent disc disease, facet joint synovial cyst rupture, conservative management for vertebral compression fracture, and symptomatic spondylolysis.[2][1] 

Prior to facet joint injections, it is recommended that conservative treatments are trialed for at least 3 months, including multimodal medication management, physical therapy, and behavioral modifications. It is also important to note the presence of moderate to severe pain burden with pain scores > 4/10 on the numeric pain scale, as well as an associated compromise in functionality or quality of life.

Indications for therapeutic facet joint injection include patients with confirmed facet joint pain who responded to diagnostic facet joint injection, adjunct to conservative pain management, in patients who are unable to manage pain with oral or systemic drug therapy, pain due to adjacent segment deterioration after spinal fusion, pain due to spondylolytic defects.[2]

Contraindications

There are no absolute contraindications besides patient refusal. Relative contraindications include patients with systemic or local infection over the injection site, coagulopathy or bleeding diathesis (particularly with the cervical region), allergy to contrast agent or medications, a neurologic disorder that may be masked by procedure, and pregnancy.[2][3]

Equipment

• Imaging suite with access to C-arm fluoroscopy or computed tomography (CT) 
• 18 gauge needle for aspirating drugs
• 25 gauge hypodermic needle for skin infiltration with a local anesthetic
• 1% lidocaine for skin infiltration
• A 22 to 25 gauge spinal needle for entering the facet joint
• Contrast agent (240 mg % iohexol)
• Local anesthetic (0.5% bupivacaine is long-acting, alternative agents may be used)
• Steroid (40 mg % triamcinolone is long-acting, alternative agents may be used)[2]

Personnel

Facet joint injections are typically performed by clinicians trained in pain, interventional radiology, physical medicine and rehabilitation, and spine intervention.

Preparation

Written consent should be obtained after the patient is informed about the risks, benefits, and alternatives to facet joint injection. The patient should be advised that pain relief with a facet joint injection is variable and that repeated injections may be needed due to the transient nature of pain improvement.[2][3] The procedure is typically performed at an outpatient facility. Sedation is ideally avoided as it may confound the patient’s response to pain, but mild sedation may be considered if the patient is anxious. Vitals signs will be monitored during the procedure.[2]

Patient positioning is prone, and a pillow can be placed under the abdomen to allow ease of access to the joint and reduce lumbar curving. The patient’s head and face should be supported for comfort and breathing. For cervical injections, patient positioning may involve a lateral or an oblique frontal approach. If lateral positioning is assumed, a headrest should be used to avoid lateral flexion of the neck, and shoulders should be positioned down.[5]

Technique or Treatment

The facet joint can be identified under image guidance with fluoroscopy or CT.[5] Fluoroscopy allows for real-time feedback and the ability to view the joint in multiple planes while minimizing radiation. CT imaging may be beneficial in accessing joints with steep angulation. After the facet joint of interest is identified, the overlying skin is marked, prepped with aseptic technique, and draped in a sterile manner. Local anesthesia is applied to the skin and subcutaneous tissue. Under image guidance, a 3.5-inch (5-inch for patients with obesity) 22 to 25 gauge spinal needle will be advanced to the facet joint, and a contrast medium (0.2 to 0.5 mL) will be injected.[8] Confirmation of intraarticular access is seen on imaging with the formation of a linear streak between articular surfaces and the presence of the medium in either or both of the subcapsular pockets.[5] 

Once intraarticular access is confirmed, a combination of local anesthetic and steroids may be injected.[8] It is recommended that the volume injected be between 1 to 1.5 mL as larger volumes may rupture the joint capsule. However, the injection should be terminated if resistance is encountered.[2] Local anesthetics provide immediate pain relief, while steroids provide longer-lasting pain relief without the need to utilize radiofrequency ablation.[2] Local anesthetics function in inhibiting nerve conduction and excitation with duration depending on the type of anesthetic (lidocaine, bupivacaine, and ropivacaine are commonly used). Corticosteroids function in inhibiting inflammation, promoting immunosuppression, and inhibiting C fiber neural transmission.[6] The most commonly used agents are methylprednisolone, dexamethasone, triamcinolone, and betamethasone.[9] 

It is recommended to only use dexamethasone in the thoracic and cervical region to mitigate the risk of particulate-related embolic events. A previous study evaluating patients with mild, moderate, and severe lumbar facet joint osteoarthritis demonstrated significant improvement in pain scores at 3 months post-treatment with steroids.[10]

It should be noted that intra-articular facet joint injection does not serve as a diagnostic block in preparation for radiofrequency ablation. If radiofrequency ablation of the medial branches innervating the facet joint is desired for longer-lasting relief, the prior test blocks should be done with local anesthesia only (0.25 to 0.5 ml of 2 % lidocaine or 0.5 % bupivacaine) at the level of the medial branches. Each diagnostic test block needs to provide > 80 % analgesia for the duration of the local anesthetic used. 

Complications

Overall, facet joint interventions are considered to be moderate to low risk procedures.[11]

Complications from image-guided facet joint injections are rare. These include septic arthritis, hematoma, excessive bleeding, nerve root irritation, vasovagal reactions, facet capsule rupture, psoas abscess, dural puncture, vertebral artery damage (reported in cervical injections), intrathecal injection, epidural abscess, meningitis, pneumothorax, and phrenic nerve palsy (reported in cervical injections).[5][12][13][14][2] Due to the specific complications associated with cervical facet joint injections, it is less commonly performed at this level. In a study evaluating adverse events related to facet joint injections, major complications were rare and typically related to infections in patients over the age of 60 years old with underlying risk factors.[1]

Issues such as swelling and pain at the needle insertion site typically resolve spontaneously and only last a short period. Local anesthetics rarely cause severe reactions, and steroid injections may cause local reactions that resolve within 48 hours.[2]

Clinical Significance

Although pain stemming from facet joint etiology is common, the diagnosis is challenging due to non-specific findings on physical exam, history, and imaging that may overlap with other pain pathologies. Diagnostic facet joint injections provide a reliable modality to detect pain originating from the facet joint and may offer patient pain relief and guidance in future interventions or treatment.

Enhancing Healthcare Team Outcomes

Facet joint injections are commonly used to diagnose facet joint pain and may provide therapeutic effects. An interprofessional healthcare team approach is critical to ensure patient safety and the proper execution of the procedure. Prior to entering the interventional suite, there should be a review of the patient’s medical history, allergies, labs, and consent. The team will typically involve the physician performing the procedure, nurse, pharmacist, and imaging technician.

Communication is important as each individual plays an essential role in the procedure. The nurse will assist with bringing in equipment, administering medications, and placing monitors on the patient for vital signs. The imaging technician should position the fluoroscopy or CT in an appropriate location before the procedure and be aware of which levels are to be imaged. Communication to a pharmacist should be employed if there are any questions or concerns about the medications. Positioning of the patient is the responsibility of the entire team but is typically performed by the nurse then adjusted as needed to optimize access to the desired facet joint.

The patient is typically awake for the procedure, and thus communicate with the patient about the expectations during the procedure is important. After the procedure, the patient is monitored by the nurse for any immediate adverse effects. Before departure, the patient should be educated on common issues after the procedure, such as injection site tenderness and precautions that would warrant immediate medical attention. The clinician who performed the procedure should be available to answer any questions if the nurse cannot. The interprofessional approach amongst physicians, nurses, pharmacists, and ancillary staff will provide the best outcomes for the patient. [Level 5]