Introduction

Spinal pain is extremely common. The incidences of pain in the neck, thoracic, and low back are estimated at 44%, 15%, and 56%, respectively, in the general population.¹ Facet arthropathy is an important source of spinal pain, and facet interventions are the second most common procedure performed in the United States by pain physicians, behind epidural steroid injections. This chapter focuses on the intraarticular injections of facet joints between vertebrae C2 through S1 for diagnostic and therapeutic purposes. The injection of the atlanto-axial joint (AAJ) between vertebrae C1-C2 is discussed elsewhere.

Prevalence of Facet Joint Pain

Estimates of lumbar facetogenic pain vary, from 15% of all back pain complaints² to 59.6% males and 66.7% females in the community based on a population study.³ The prevalence of lumbar facetogenic pain, determined by placebo-controlled diagnostic blocks using a criterion of 90% pain reduction, ranges from 27% to 40% in patients with axial low back pain.^4,5 Sedation may increase false-positive rates of diagnostic blocks by 10%, but psychological comorbidity has not been shown to affect the diagnostic accuracy. Aging is positively related to the prevalence of lumbar facet arthropathy, with an occurrence of 89% in individuals 60 to 69 years old. The most common level is at L4-L5.²

The prevalence of thoracic facet pain ranges between 33% and 48% with a 95% confidence interval based on responses to comparative controlled diagnostic blocks.⁶ The prevalence of cervical facet pain is 30% to 70% of cases^7–9 and is not significantly affected by prior surgery, psychopathology, or age. The most commonly affected facet is C4-C5 (14.62%) followed by C3-C4, C2-C3, C5-C6, and C6-C7, respectively.¹⁰ There is no proven correlation between clinical manifestation of facetogenic pain and facet arthrosis shown by imaging studies or cadaveric observations. Diagnostic block remains the best available tool to identify facetogenic pain despite its high false-positive rates (39% to 53%).

Thus, facet arthropathy accounts for approximately 40% of axial cervical and thoracic pain and approximately 30% of axial lumbar pain. The most commonly affected levels are C4-C5 at the cervical region and L4-L5 at the lumbar region. Whereas lumbar facet pain is more age dependent, predominantly occurring in elderly adults, cervical and thoracic facet pain is not significantly affected by age.

Establishing Diagnosis

Numerous studies have attempted to determine the historical, or physical, and radiographic findings that correlate with pain associated with facet arthropathy. None has been proven specific, sensitive, and reliable.² Consequently, diagnosis is primarily based on pain reduction and mobility improvement in response to controlled diagnostic facet blocks.^4,6,11 The diagnosis of facetogenic pain is suggested by controlled comparative (lidocaine/bupivacaine) medial branch blocks. A criterion of 80% pain reduction and the ability to perform maneuvers that were painful before the diagnostic intervention are commonly used. However, a recent study suggests that using 50% pain reduction as a criterion for positive diagnostic block is just as effective as using 80% pain reduction in predicting the outcomes of medial branch radiofrequency ablation.¹²

Even though facetogenic pain is primarily determined by diagnostic blocks, clinical findings from history and physical examinations usually help physicians decide if diagnostic facet blocks are warranted. For example, pain from the AAJ is typically provoked by head rotation with the neck slightly flexed forward. This information may lead to an AAJ block rather than a cervical facet block. Therefore, taking the patient history and performing a physical examination is still an indispensable step in establishing a diagnosis of facet pain. Pain referral patterns for cervical and thoracic facet pain have been generated,^2,13–15 as shown in Fig. 12-1.

Fig. 12-1 Maps of referred pain from the cervical (A) and thoracic (B) facets.

(Part A adapted from Bogduk N, Marland A: The cervical zygapophysial joints as a source of neck pain, Spine 13:610-617, 1988; part B adapted from Dreyfuss P, Tibiletti C, Dreyer SJ: Thoracic zygapophyseal joint pain patterns: a study in normal volunteers, Spine 19:807-811, 1994.)

Anatomy of the Facet Joints

The vertebral column most commonly consists of seven cervical, 12 thoracic, and five lumbar vertebrae. Two adjacent vertebrae make joint connections through the intervertebral disc in the front and a pair of facet joints in the back, with the exception of C1-C2 vertebrae. The facet is a true synovial joint between the inferior and superior articular processes composed of a synovial membrane, hyaline cartilage, and fibrous capsule. These joints function to support the stability of the spine and prevent injury by limiting excessive motion in all directions.

The facet joints have rich innervation, including encapsulated, unencapsulated, and free nerve endings.² These innervations provide nociception through C and A-δ afferents as well as proprioception through low-threshold, rapidly adapting mechanoreceptors.¹⁹ Immunocytochemistry of facet joints demonstrated the presence of substance P, calcitonin-gene-related peptide, and neuropeptide Y, suggesting pain transmission and sympathetic fibers.^20–22 Facet joint distraction in rats produces spinal astrocyte activation and persistent mechanical allodynia.²³ The expression of a binding protein BiP, also known as growth-related protein 78, is upregulated 2.1-fold in the dorsal root ganglion after painful distraction injury to the rat C6-C7 facet, indicating neuronal stress activation.²⁴ Cytokines and neurotrophic factors are upregulated in dorsal root ganglion neurons in models of facet joint inflammation.^25–28

The architecture and orientation of the facet joint vary with function and position along the vertebral column.^29–31 The lumbar facet joint can accommodate an average of 1 to 1.5 mL fluid. The joint is C shaped and is encased posteriorly in a fibrous capsule of approximately 1 mm thick composed of collagenous tissue. The lumbar facet joint is supported posteriorly by multifidus muscle, superiorly and inferiorly by fibroadipose menisci forming subcapsular recesses, and anteriorly by the ligamentum flavum.³¹ The inferior portion of the joint is larger than the superior portion. Any given facet joint has dual innervation from two segmental medial branch nerves: one arising at the given level and one from one segment above as shown in Fig. 12-2. Consequently, a given medial branch nerve innervates two facet joints, the ascending branch to the caudal portion of the facet above and the descending branch to superior portion of the facet below. For example, the L3 medial branch nerve courses along the junction of the superior articular process and the transverse process of L4 under the mamilloaccessory ligament, supplying the caudal portion of the ipsilateral L3-L4 facet joint, and then courses caudally to supply the ipsilateral superior portion of the L4-L5 facet joint. Conversely, the L3-L4 facet has dual innervation from the L2 and L3 medial branches.

Fig. 12-2 Schematic illustration of lumbar facet innervations.

(Adapted from Cohen SP, Raja SN: Pathogenesis, diagnosis, and treatment of lumbar zygapophysial (facet) joint pain, Anesthesiology 106:591-614, 2007.)

The thoracic facet joint can accommodate no more than 0.75 mL of fluid and is more vertically oriented than the lumbar or cervical facet joints. On average, they are approximately 75 degrees from the sagittal and transverse planes. Similar to the lumbar facets, the thoracic facet joints also have dual innervation. The dorsal ramus arises from the lateral margin of the intervertebral foramen and then courses dorsally, inferiorly, and laterally within the intertransverse space, where it continues over the superolateral portion of the transverse process and runs between the semispinalis thoracis and thoracic multifidus. The dorsal surface of the transverse process is the bony landmark for thoracic medial branch nerve at T1-T4 and T9-T10 levels. The T11-T12 medial branch courses have similar anatomical relationships to the lumbar medial branch nerves as described. It is important to note that the course of the thoracic medial branch differs from lumbar and in some cases does not contact the transverse process. The lack of association with a bony landmark, particularly at T5-T8, makes the thoracic facet medial branch a challenging target for percutaneous interventional procedures.

The cervical facet joints are between the articular pillars of the vertebrae and are oriented approximately 45 degrees from the transverse plain and 80 degrees from the sagittal. The cervical facet joint can accommodate approximately 0.5 to 1.0 mL of fluid. The lateral recess is the target for percutaneous intervention, formed by a thick lateral fibrous capsule and synovial-lined recesses. There is some anatomical variability with the innervation of the cervical facet joints. The medial branch nerve arises from the posterior ramus and passes around the ipsilateral articular pillar, and similar to the thoracic and lumbar facet joints, innervate two joints. Therefore, a given medial branch nerve innervates the inferior portion of the superior facet joint and the superior portion of the inferior facet joint. For example, the C4 medial branch nerve innervates the inferior portion of the C3-C4 facet and the superior portion of the C4-C5 facet. Conversely, each facet joint receives medial branches from above and below. The posterior rami in the cervical region provide little innervation to the paraspinal muscles. Fascia and tendons of the semispinalis capitis muscle ensure the medial branches are adjacent to the periosteum.

Special attention is required for the C2-C3 facet joint and the C1-C2 (atlanto-axial) joint. There are four occipital nerves that may contribute to neck pain and headaches. The suboccipital nerve is the dorsal primary rami of C1. The greater occipital nerve is the medial branch of dorsal primary rami of C2. The lesser occipital nerve is the ventral primary rami of C2 and C3. The least occipital nerve, or third occipital nerve, is the medial sensory branch of dorsal ramus of C3. The C2-C3 facet receives the majority of its innervation from the C3 dorsal ramus. The C1, C2, and C3 nerves have been implicated in the trigeminocervical complex as a source of headaches.

Guidelines for Intervention

The latest published practice guidelines for chronic pain management by the American Society of Anesthesiologists Task Force on Chronic Pain Management and the American Society of Regional Anesthesia and Pain Medicine state:

In addition, a recent prospective study tested intraarticular injection of hylan G-F 20 in patients with painful lumbar facet joint arthropathy and reported significant improvement in pain scores, quality of life, and opioid consumption for 6 months.³³ Studies of injecting nonsteroid agents may represent a new direction of intraarticular facet therapy.

The American Society of Interventional Pain Physicians did not recommend intraarticular injections for either diagnostic or therapeutic benefit.³⁴ The International Spine Intervention Society described guidelines for thoracic intraarticular facet joint blocks as an emerging procedure and did not comment on intraarticular lumbar or cervical facet joint blocks.³⁵ Both guidelines suggest better evidence (level I or II) with medial branch blocks for diagnosis and radiofrequency ablation for therapeutic benefit after two positive comparative controlled diagnostic blocks using 80% pain reduction. However, for patients who are not ideal candidates for radiofrequency ablation, such as those with pacemakers, intraarticular facet block with a mixture of local anesthetic and steroid is a viable option.

Indications and Contraindications

Facet interventions are indicated in patients with moderate to severe spinal pain that is somatic and nonradicular (or headache), lasts longer than 3 months in duration, with functional limitation or impairment; failure of more conservative therapies (exercise, physical therapy, simple analgesics); and lack of evidence supporting primarily a discogenic, myofascial, or radicular pain source. Importantly, the patient should have the ability to undergo physical therapy after the intervention.^34,35

Contraindications include anything that would preclude neuraxial procedures, such as lack of informed consent; hemodynamic instability; coagulopathy or thrombocytopenia; pregnancy; infection overlying the puncture site; inability to see target site secondary to hardware; inability of the patient to lie in the procedure position; or allergy to contrast, steroids, local anesthetics, and so on. Readers are referred to American Society of Regional Anesthesia and Pain Medicine guidelines for regional anesthesia and anticoagulation.³⁶

Techniques for Facet Joint Injection

Informed consent is obtained before an intravenous line is placed in a preblock room. The site of the procedure is labeled, and the patient is transported to the procedure room, where the patient is positioned either in the lateral decubitus position with the procedure side up or in a prone position, depending on the level of injections in the spine. Patients are monitored with standard ASA monitors that include three-lead electrocardiography, pulse oximetry, and noninvasive blood pressure measurement at least every 5 minutes. A sign-in process is performed to confirm the patient’s identity, allergies, procedure site, body position, and necessary equipment. Light sedation with anxiolytics such as benzodiazepines and fast-acting opioids are sometimes used, although it is often unnecessary. Heavy sedation, with propofol in particular, is not recommended to ensure effective communication with the patient during the procedure.

Cervical Facet

Lateral Approach

The patient is self-positioned in the lateral decubitus position with the symptomatic side up. The head is placed in the neutral position or slightly extended to the contralateral side (supporting side) to facilitate needle placement. The site is prepped and draped in sterile fashion. The articular pillars and vertebral endplates are aligned under lateral view of fluoroscopy so there is no parallax at the level of the injection site. After the targeted facet has been identified, a radiopaque marker is placed on the skin to localize the entry point, where 1 mL of 1% lidocaine is injected and a 25-gauge 3.5-inch spinal needle is advanced in plane coaxial approach to contact the targeted facet joint under intermittent fluoroscopy guidance. Nonionic contrast of 0.1 to 0.2 mL is injected under a “live” fluoroscopic view to ensure intraarticular filling without vascular spread as shown in Fig. 12-3 (compare A and B, before and after 0.1 mL contrast injection at the C4-C5 facet as indicated by the arrows). The joint accommodates between 0.5 to 1 mL of volume. After proper needle position has been confirmed, 0.5 mL of local anesthetic is injected for diagnostic purposes or a combination of 0.5 mL of local anesthetic and steroid is injected for therapeutic purposes. The needle is then slowly removed, the skin is cleaned, and a bandage is applied, and the patient is transported to the postblock recovery area. It is noteworthy that a true lateral view is critically important to avoid inadvertent entry of the needle into the spinal canal. Also, the needle should first contact the articular pillar of the targeted facet joint and then walk off the pillar to enter the joint to avoid overshoot of the needle into the spinal canal.

Fig. 12-3 Cervical facet intraarticular injection: lateral approach. A, Spinal needle is placed in the C4-C5 facet joint (arrow). B, Injection of 0.1 mL of contrast partially filled the facet joint (arrow).

Posterior Approach

The patient is self-positioned prone with the head in neutral position. The skin is prepped and draped in sterile fashion. The C-arm is rotated slightly oblique and then caudad to align the X-ray beam parallel to the surface plane of the facet joint. After the trajectory has been determined, the spinal needle is advanced under intermittent fluoroscopic guidance into the joint, maintaining a coaxial view of the needle. The rest of the injection is the same as for the lateral approach.

Lumbar Facet

The patient is self-positioned prone. The skin is prepped and draped in sterile fashion. The targeted facet is identified with fluoroscopy, and the C-arm is rotated ipsilateral oblique (25 to 35 degrees) to “open” the facet joint (Fig. 12-4). Sometimes a caudocranial angulation of the C-arm (image intensifier toward the head) is required to better visualize the joint space in between the superior and inferior articular processes. The needle is advanced in a coaxial manner with intermittent fluoroscopy to enter in caudal pole of the facet joint. The lumbar facet joint accommodates 1 to 1.5 mL of volume. After the needle has been engaged, 0.1 mL of contrast may be injected, confirming intraarticular spread as shown in Fig. 12-4 (compare A and B, before and after contrast injection at the L5-S1 facet as indicated by the arrows). After proper needle position has been confirmed, for diagnostic purposes, 0.5 mL of local anesthetic is injected; for therapeutic purposes, a combination of 0.5 to 1 mL of local anesthetic and steroid is injected. The needle is then slowly removed, a bandage is applied, and the patient is transported to the postblock recovery area.

Fig. 12-4 Lumbar facet intraarticular injection. A, Spinal needle is placed in the L5-S1 facet joint (arrow). B, Injection of 0.1 mL contrast partially filled the facet joint (arrow).

Imaging

Multidirectional C-arm fluoroscopy is required to perform the blocks using a radiolucent table. Fluoroscopy with film archiving capability is suggested. Ultrasonography is an emerging modality to guide needle placement in the cervical region for intraarticular facet injection and medial branch blocks. Computed tomography has also been used.

Patient Management and Evaluation

The patient should be monitored in the recovery room for at least 15 minutes after the procedure. Relief of concordant pain and increased mobility of provocative movements are assessed before discharge. Written discharge instructions include limiting activities the day of the procedure; resuming all activities the next day; and contacting the physician if there is any weakness, fever, chills, or erythema or induration at the site of the procedure. A pain diary and globally perceived effect are commonly used for evaluation of the outcome.

Outcomes Evidence

There was limited evidence supporting intraarticular anesthetic or steroid injection for diagnostic or therapeutic purposes.^5,6,11 Nevertheless, intraarticular injection can be used in patients who are not ideal candidates for radiofrequency ablation of the facet medial branches, such as those with pacemakers. Furthermore, lumbar facet intraarticular injection of hylan G-F 20 appears effective in pain reduction, improving quality of life, and reducing opioid consumption for 6 months.³³

Risk and Complication Avoidance

Facet joint injection is generally considered to be a very safe procedure. However, significant complications have been reported, including spinal cord injury associated with cervical facet injection and pneumothorax associated with thoracic facet injections.³⁷ Vascular injection of local anesthetics or steroids is a concern associated with spinal procedures. The radicular arteries are the main source of blood to the spinal cord and usually enter the spinal canal in the cervical region through the neuroforamen accompanying the C4-C6 nerve roots.³⁸ Pneumothorax is a concern for any paraspinal thoracic procedure. Other complications reported after facet injections include spondylodiscitis, meningitis and chemical meningism, septic arthritis, and epidural abscess.³⁷ Postdural puncture headache has also been reported.³⁹ The effect on the hypothalamic–pituitary–adrenal axis is likely similar to that of epidural steroid injections.⁴⁰

Many of these complications may be prevented by observing strict aseptic techniques and by performing the procedures with clear understanding of the anatomy and the techniques. Adequate monitoring, early detection, aggressive treatment, and accurate documentation are required when complications do occur to minimize the adverse outcomes.³⁷