History and Physical Examination

History and physical examination are important for exclusion of other causes of spinal pain. On reviewing the medical history, several conditions can affect the facet joints. These include osteoarthritis, inflammatory arthritides (rheumatoid arthritis, ankylosing spondylitis, and reactive arthritis), synovial impingement, meniscoid entrapment, chondromalacia facetae, pseudogout, synovial inflammation, and villonodular synovitis,^1–4 Signs on clinical examination that may point to facet pain include tenderness over the facet joints on palpation; pain that is characterized as deep, dull, and aching; pain that is difficult to localize; and stiffness, especially in the morning. Sudden onset of pain noted with twisting, bending, or rotary movements and pain aggravated on extension and lateral bending more than flexion are also consistent with facet joint–mediated pain, although the latter finding is unreliable. Additional physical examination findings may include muscle spasm and either hypalgesia or hyperalgesia over the area of pain. Flexion, extension, and rotation may or may not be decreased. The straight-leg raise results are usually negative. Given all of the above, the clinical criteria for facet joint–mediated pain are generally nonspecific and unreliable.^5–7 Most maneuvers used in physical examinations are likely to stress several structures simultaneously, especially the discs, muscles, and facet joints, thus failing to provide any reasonable diagnostic criteria based on physical examination.

As stated previously, history and physical examination, along with radiologic imaging, cannot reliably be used to diagnose painful zygapophyseal joints. Therefore, medical branch blocks are needed to diagnose facetogenic pain.⁸ Numerous studies have tried to predict who will respond to facet joint injections. Revel et al⁹ identified seven variables associated with a positive response to facet joint injections: age older than 65 years, pain that was not exacerbated by coughing, pain not worsened by hyperextension, pain not worsened by forward flexion, pain not worsened when rising from flexion, pain not worsened by extension-rotation, and pain well relieved by recumbency. A later study by Revel et al¹⁰ found the presence of five among seven variables distinguished 92% of the patients responding to lidocaine injection and 80% of those not responding to lidocaine. However, further investigations of Revel et al’s variables by other investigators have been proven wrong.⁵

Injections in Facilitating the Diagnosis

Facet joint–mediated pain can be diagnosed with placebo-controlled or controlled local anesthetic diagnostic blocks using either facet joint blocks or medial branch blocks. The choice of technique used should be based on evidence of effectiveness of diagnosis and ease of technique. Evidence for diagnostic medial branch blocks using 80% pain relief with controlled diagnosed blocks are noted to be Level I or II-1 based on U.S. Preventive Services Task Force criteria.^11,12 Medial branch blocks are relatively easier to perform and safer than intraarticular blocks because medial branch blocks can be performed even with osteophyte formation, which prevents entry into the facet joint. Additionally, the target area of the medial branch prevents overpenetration of the needle into the spinal canal during placement, therefore decreasing the possibility that the needle will pass through the target and into the spinal canal and cord, which can occur during intraarticular injections. Medial branch blocks also have therapeutic validity, but the therapeutic validity of intraarticular injection is lacking.¹¹

False-positive rates of single local anesthetic blocks are high, ranging from 27% to 63% for cervical, 42% to 58% for thoracic, and 21% to 33% for lumbar medial branch blocks.^12–14

Because of high false-positive rate of single local anesthetic blocks, numerous experts advocate performing diagnostic double blocks with either saline control or two different local anesthetics. Control blocks using normal saline under double-blind conditions is the most rigorous form of control blocks, requiring three blocks of the same joint. The first block would have to be with the local anesthetic to establish prima facie that the joint is symptomatic. To maintain the controlling effect of change and blinding, the second block would have to be either normal saline or inactive agent, and the third block would need to be the reciprocal agent.⁸ Despite this evidence, in a systematic study of the cost-effectiveness of using controlled facet blocks, Bogduk and Holmes¹⁵ determined that the use of placebo-controlled injections cannot be justified in the United States based on financial considerations.

In clinical practice, controlled diagnostic blocks with two local anesthetics with different durations are used. A true-positive response is one in which the patient reports complete relief of pain for a shorter duration when short-acting local anesthetic is used and a longer duration when a long-acting agent is used.¹⁶ Lidocaine 1% to 2% commonly used for the first block with a positive response is followed by a later block with bupivacaine 0.25% to 0.5% 2 to 4 weeks later.^11,17 Response patterns of medial branch blocks using bupivacaine and lidocaine were defined by Barnsley et al.¹⁶

A concordant response confirms that the joint is the source of pain with confidence of 85%.¹⁸

The Facet Joint

The basic anatomical unit of the spine is referred to as a three-joint complex that consists of paired zygapophyseal joints and an intervertebral disc (Fig. 13-1).¹⁹ This articular triad functions to stabilize and support the spine along with limiting motion of the spine.

Fig. 13-1 Illustration of the posterior view of the lumbar spine and the posterior neural structures. Laminae of L2 through S1 are labeled. DPRL5, dorsal primary ramus of L5; DPRS1, dorsal primary ramus of S1; DPR3, dorsal primary ramus of L3; FJ, facet (zygapophyseal) joint L3-L4; I, inferior articular process of L4; LB1, lateral branch of dorsal primary ramus of L1; IAB, inferior articular branches from L3 medial branch (supplies L4-L5 facet joint); IBP, intermediate branch plexus; MB3, medial branch of dorsal primary ramus of L3; NR3, third lumbar nerve root; S, superior articular process of L5; SAB, superior articular branches from L4 (supplies L4-5 facet joint also); TP3, transverse process of L3.

The term zygapophyseal joint (or facet joint) originated from the Greek root zygos, meaning yoke or bridge, and physis, meaning outgrowth. Therefore, the facet joints bridge the vertebrae behind the vertebral foramina.²⁰ Facet joints are paired diarthrodial synovial joints formed by inferior articular process of one vertebra and superior articular process of the subjacent vertebra. Facet joints share the same general characteristics of synovial joints. As true synovial joints, each facet joint contains distinct joint space capable of accommodating 1 to 1.5 mL of fluid, a synovial membrane, hyaline cartilage surfaces, and fibrous capsule. The fibrous capsule of the facet joint is composed mostly of collagenous tissue arranged more or less in transverse fashion to provide maximum resistance to flexion. The thick fibrous joint capsule is covered by synovial membrane superiorly, posteriorly, and inferiorly. Anteriorly, the synovial membrane lacks a true fibrous capsule and instead is in direct contact with the ligamentum flavum.¹⁹

Facet joints are richly innervated with three types of nerve endings: encapsulated (Ruffini-type endings, pacinian corpuscles), unencapsulated, and free nerve endings.¹⁹ The presence of low-threshold, rapidly adapting mechanosensitive neurons lining the facet capsule suggests that in addition to transmitting nociceptive information, the facet capsule also serves proprioceptive function.^21,22

Facet capsule nerve endings contain substance P, calcitonin gene-related peptide, and neuropeptide Y.^23,24 Inflammatory mediators such as prostaglandins, inflammatory cytokinase, interleukin 1B, interleukin 7, and tumor necrosis factor have also been found in facet joint cartilage and synovial tissue.^25,26

The orientation of the facet joints varies at the cervical, thoracic, and lumbar regions. Facet joints oriented parallel to the sagittal plane provide substantial resistance to axial rotation but minimal resistance to shearing forces (backward and forward sliding), and facet joints oriented more in a coronal plane tend to protect against flexion and shearing forces but provide minimal protection against rotation. The cervical facets are orientated in a coronal plane, which allows for flexion, extension, and lateral bending. The C2-C3 to C5-C6 facets are angled 35 degrees from the coronal plane, and C7-T1 are angled 22 degrees from the coronal plane. Orientation of the C5-C6 facet joint is between 22 and 35 degrees. All cervical facet joints from C2-C3 to C7-T1 are angled 110 degrees from the midline posterior sagittal plane. In the cervical spine, it is important to remember that the vertebral artery passes through the foramen of the transverse process of C1-C6.²⁷

Facet joints in the thoracic spine differ from that of the cervical and lumbar spines in that their orientation is in a more coronal direction, which allows thoracic facet joints to play an important role in stabilization of thoracic spine during flexion loading. The T1-T2 facet joint is angled 66 degrees from a transverse plane, with the cephalad end more anterior than the caudad end. The T3-4 to T11-T12 facet joints are angled 75 degrees from the transverse plane. The T1-T2 to the T11-T12 facet joints are uniformly angled 110 degrees from the midline posterior sagittal plane. The T12-L1 facet joint is 25 degrees oblique to the sagittal plane from the midline posteriorly, which is similar to the lumbar orientation.^28,29

The upper lumbar facet joints (T12-L2) are oriented closer to the midsagittal plane of the vertebral body, which allows limited rotational movements and favors flexion and extension. The lower facet joints tend to be oriented in a more coronal angle, which allows for greater rotational movements. The lumbar facet joints’ cephalad ends are farther anterior than the caudad ends because the facet joints are tipped approximately 10 degrees. In the upper lumbar spine, approximately 80% of the facet joints are curved, and 20% are flat; in the lower lumbar spine, these numbers are reversed.^30,31 The lumbar facet joints transition from a coronal orientation to a sagittal positioning with age. Some studies have shown a positive association between degenerative spondylolisthesis and more sagitally oriented lower lumbar facet joints.³²

Cervical

The facet joints are innervated by the dual nerve supply from the medial branch of the dorsal ramus. Cervical facet joints from C3-C4 to C7-T1 are supplied by medial branches from the same level and the level above. Medial branch nerves arise from the posterior primary rami located in the cervical intertransverse space and then passes dorsally and medially to wrap around the waist of the articular pillar. The location of this nerve on the articular pillar is essentially the same as those of nerves C4-C8. The medial branches are bound to the periosteum by an investing fascia and are held against the articular pillars by tendons of the semispinalis capitis. The C7 medial branch crosses the root of the C7 transverse process and therefore lies higher on the lateral projection of the C7 articular pillar.³³

The C2-C3 facet joint differs in innervation in that their innervation comes from the third occipital nerve along with C2 and C3 medial branches. Two medial branches usually arise separately from the C3 dorsal ramus. The superior and larger branch is the third occipital nerve (also known as the superficial medial branch), and the inferior branch is the deep medial branch. The third occipital nerve innervates C2-C3 joint. It curves dorsally and medially around the superior articular process of the C3 vertebra and crosses the C2-C3 facet joint either just below or across the joint margin. It also provides cutaneous neural supply for the suboccipital region. The C3 dorsal ramus is the only cervical dorsal ramus below C2 that has a cutaneous distribution.^34,35

The C8 medial branch runs a course similar to the upper thoracic nerves. It arises from the dorsal ramus within lateral margin of the intervertebral foramen of C7-T1. Because of the C8 medial branch and seven cervical vertebrae, numbering of medial branches is different in the cervical region compared with in the thoracic and lumbar spine. The facet joint is innervated by a cervical medial branch at the same level and level above for C4-C7. For example, the C5-C6 facet joint is innervated by the medial branches of C5 and C6. This numbering applies to the C4 through C7 levels.^34,36

Medial branches of the cervical posterior rami are different than lumbar medial branches in that they supply mainly the facet joints and have limited innervations of the posterior neck muscles (the multifidus, interspinalis, semispinalis cervicis, and semispinalis capitis).

Thoracic Innervation

Medial branch nerves from two segmental levels innervate each thoracic facet. The medial branch has ascending branches that form when the medial branch passes caudal to the zygapophyseal joint and descending branches form where the medial branch crosses the transverse process to pass to the next joint below. The configuration of the upper thoracic (T1-T3) and lower thoracic (T9-T10) spine are reasonably consistent. Medial branches arise from the dorsal ramus within 5 mm of the lateral margin of the intervertebral foramen, where it passes dorsally, inferiorly, but mostly lateral within the intertransverse space. Opposite the tip of the transverse process, the medial branch curves dorsally through the intertransverse space, aiming for the superolateral corner of the transverse process. It crosses this corner and then travels caudad across the transverse process surface in the cleavage plane between the origins of the multifidus medially and the semispinalis laterally. The nerve than runs inferiorly and medially over the dorsal aspect of the multifidus. Exceptions to this configuration occur at the midthoracic level (T4-T8), where the medial branch does not reliably make bony contact with the transverse process. The nerve at times is suspended in the intertransverse space. The course is separated from the transverse process by the multifidus. There is no relation with contact to bone in these levels.

The course of the medial branches of T11 and T12 also vary because of different osseous anatomy at these levels. The T12 transverse process is shorter compared with other levels. Therefore, the T11 branch runs across the lateral surface of the root of the relatively short T12 transverse process. At the T12 level, the medial branch assumes a course analogous to those of the lumbar medial branches.^28,37,38

Lumbar Innervation

A given lumbar facet joint is innervated by nerve fibers from medial branch nerves at two levels. The medial branch nerve at a given level innervates the inferior portion of the facet above and the superior portion of the facet below except for L5, which sends an ascending articular branch only to the L5-S1 joint.

The primary dorsal rami divide into three nerves as they approach their respective transverse processes: the medial branch, intermediate branch, and lateral branch. The medial branch is the largest of the dorsal branch nerves. The medial branch has three branches as well. The proximal branch hooks around the articular process to supply the facet above. The medial descending branch passes medially and downward to innervate the superior and medial portions of the facet capsule below, the multifidus and interspinales muscles and ligament, and the periosteum of the neural arch. The ascending branch supplies the facet above. The other two main branches of the dorsal ramus are the intermediate branch and the lateral branch. The intermediate branch sends fibers into the longissimus muscles. The lateral branch innervates the iliocostalis muscle, the thoracolumbar fascia, the skin of the lower back and buttock, and the sacroiliac joint, but does not innervate the facets.^22,39

The medial branches of L1-L4 rami have a predictable course. These medial branches come off the dorsal ramus and exit from the intervertebral foramen, piercing the intertransverse ligament and crossing the superior border of the transverse process. The branches then travel along the junction of the transverse process and superior articular process. This junction is often referred to as a “groove.” The medial branch nerve runs in the groove along the lateral aspect of the neck of the superior articular process, traveling caudally and posteriorly where it is in direct contact with the base of the superior surface of the transverse process, passing under the mamilloaccessory ligament. At L3, L4, and L5 levels, this ligament can become calcified. The medial branch nerve then proceeds inferiorly and posteriorly, where it sends fibers cephalad to innervate the caudad capsular margin of the adjacent superior joint capsule. Then it sends fibers to the next lower level at its cephalad capsular margin.^20,40

The course of the L5 medial branch is somewhat modified because the transverse process is replaced by the ala of the sacrum. The L5 medial branch is not the medial branch of L5 but rather the dorsal primary ramus of L5, which is longer. The dorsal ramus pierces the intertransverse ligament and runs caudally and posteriorly along the groove formed by the junction of the superior articular process and sacral ala. The L5 dorsal ramus divides into two branches, a medial and lateral branch. The L5 medial branch curves medially around the base of the L5-S1 joint, sending an articular branch to this joint and then supplying the multifidus muscles. There is no mamilloaccessory ligament at this level. However, fibrous tissue fixes the position of the nerve at the base of the superior articular process. The lateral branch of the L5 dorsal ramus runs caudad to communicate with the S1 dorsal ramus lateral branch.^41,42

The name of the joint blocked is numerically the same as the names of the transverse processes targeted for injection, but the names of the nerves are one segment higher. For example, the L2 medial branch (which courses over the base of the L3 transverse process) innervates both the inferior portion of the L2-L3 facet joint and the superior portion of the L3-L4 facet joint. The superior portion of L2-L3 facet joint is innervated by the L1 medial branch.

Pain Referral Patterns

The distribution of referred pain appears to be related to the innervation of the medial and lateral branches of the dorsal rami. Studies of mapping out referral patterns have used asymptomatic volunteers and pain patients. Referral patterns from cervical zygapophyseal joints were studied by Dwyer et al.⁴³ In their first study, the facet injections were done in normal volunteers, which showed certain referral patterns. The accuracy of referral patterns were later studied on symptomatic patients. Referral patterns obtained were C2-C3 as pain located in the upper cervical region and extending at least onto the occiput. The C3-C4 pattern is located over the posterolateral cervical region without substantial extension into the occiput and extending caudally over the posterolateral aspect of the neck without entering the region of the shoulder girdle. The C3-C4 pattern basically covers the area that is coextensive with the underlying levator scapulae muscle. Whereas the C4-C5 pattern is concentrated over the angle formed by the top of the shoulder and side of the neck, the C5-C6 pattern spreads laterally toward the shoulder with the main area draping over the top, front, and back of the shoulder girdle, with a base coinciding with the spine of the scapula. The C6-C7 pattern extends below the spine of the scapula. The typical C7-T1 pain pattern extends into the paravertebral area with coverage over the scapulae.⁴⁴

The thoracic facets may produce middle back pain that is paraspinous with neuralgic characteristics. Thoracic referral patterns were noted by joint distention in normal volunteers. Some overlap was noted in the thoracic area. The pain was usually one to two segments inferior and lateral to the involved joint and unilateral. The T1-T2 joint pain was noted to be below the inferior angle of the scapulae. Despite this, there is a wide overlap in thoracic referral patterns that makes them unreliable.^44–46

Referred pain from the lumbar zygapophyseal joints and medial branches has been examined in numerous studies showing overlap of referred pain between each level.^47,48 Pain from L1-L3 has been shown to extend into the flank, hip, and upper lateral thighs. Pain from L3-S1 has been shown to extend deeper into the thigh, usually laterally and posteriorly and also into the groin area. Referred pain from the L4-5 and L5-S1 facet joints can also cause pain extending into the lower lateral leg, below the knee, and even to the foot at times.^20,47,49 Referred pain may also assume a pseudoradicular pattern, making the underlying diagnosis difficult to confirm based on pain patterns.⁵⁰

Indications

The purpose of medial branch blocks is to test if the patient’s pain is relieved by anesthetizing the target nerves. Patients who should be included for diagnostic medial branch blocks may have pain that is somatic or nonradicular pain in the neck, upper back, mid back, lower back, upper or lower extremity, or chest wall, or headaches. Pain should be intermittent or continuous with a visual analog score an average of 6 or more on a scale of 0 to 10 that causes functional disability. Pain should last for at least 3 months or longer. Patients should have spinal pain of unknown origin and lack neurological deficits. Patients should have tried and failed conservative management, which includes oral medications such as nonsteroidal antiinflammatory drugs (NSAIDs), physical therapy, exercise, and bed rest.^11,13

Contraindications

Contraindications are those for any regional block.

Absolute contraindications are those conditions in which the conduct of a needle procedure under radiographic control could cause potential risk to the patient’s health and include:

Relative contraindications are conditions that require special consideration because of the risk they pose. They do not preclude the performance of medial branch blocks; however, because of these conditions, the investigator may elect not to perform the procedure. If they do proceed, special precautions are necessary.

Relative contraindications include:

Target Identification

Cervical

Positioning

Cervical medial branch blocks can be performed with the patient in the prone, supine, or lateral position. If using the lateral approach, the patient is placed in the lateral decubitus position with the painful side up. A cushion can be placed underneath the patient’s head to keep the neck parallel to the table. The patient can use a pillow or device to hug or accommodate the arms if needed. The prone position is also a commonly used approach to the cervical medial branches.

Needle Placement

The target points for cervical medial branch blocks from the third to the sixth medial branches is the “centroid” of the articular pillars with the same segmental number as the target nerve (Fig. 13-2). The centroid is found at the intersection of the two diagonals of the diamond-shaped pillar. This target point can be seen with true lateral fluoroscopic imaging in which the silhouettes of the articular pillars on each side at a given segment are superimposed. To confirm superimposition, the x-ray beam should be tilted around the long axis of the patient for splitting of the superimposed articular pillar silhouettes to occur. Therefore, the ipsilateral articular processes are noted. It is important to confirm a true lateral view because it is essential to eliminate any risk of aiming the needle toward the contralateral side of the neck. It is important to have the target point in the center of the x-ray beam so it appears on the center screen when using fluoroscopy. Keeping the target point in the center avoids parallax errors.

Fig. 13-2 Target zones for cervical medial branch block. Lateral illustration of cervical spine showing target zones (black arrows pointing to green circles) located at the midportion of the C2 through C7 articular pillars. The third occipital nerve (TON) is a relatively large nerve branch that may require three separate blocks at the level of the C2 inferior facet or C3 superior facet and where it courses lateral to the C2-C3 facet joint. VA, vertebral artery.

It is important to remember that the vertebral artery from C2 to C7 is located anterior to the facet joint from both a lateral and posterior approach. With a posterolateral approach, the needle should pass through fascia and muscle and remain posterior to the vertebral artery. The puncture point on the skin is selected overlying the target point. The needle tip should be placed at the intended puncture site with the shaft aligned parallel to the x-ray beam, which allows the needle to be directed straight toward the target point. For the patient’s comfort, the needle should be quickly inserted through the skin. When going thorough neck musculature, to minimize discomfort, especially at upper cervical levels, the practitioner should avoid piercing the sternocleidomastoid muscle if possible. If the initial puncture site overlies the sternocleidomastoid, then the patient’s head should be rotated slightly into the pillow. This maneuver attempts to draw the muscle forward and away from the puncture site. The needle can be advanced under lateral fluoroscopic guidance. Corrections toward the target should be made superficially with only fine corrections made when the tip of the needle enters close to the target point. Periodic checking with fluoroscopy should be done to ensure correct position and orientation as the needle is advanced to the target point. Needle placement is then confirmed after negative aspiration with 0.3 mL of contrast. The pillars should be noted on the lateral view. The interventionalist should see spread of contrast across the lateral surface of the articular pillar, filling the concavity that lodges the targeted medial branch. Excess injectate from this site can also spread in a rostrodorsal direction across the plane located between the semispinalis capitis and multifidus. After proper placement is confirmed with contrast, 0.3 mL of local anesthetic is used to anesthetize the target nerve. The needle should be held against the bone during injection.

The transverse process of C7 tends to displace the medial branch relatively higher than the other typical cervical medial branches. Therefore, the target point for the C7 medial branch block lies higher, at the apex of the superior articular process of C7. If the target point is selected too low for C7, the needle may appear to rest on the superior articular process when it is resting on the transverse process. In the lateral view, the target point for the C7 medial branch block will rest higher than the silhouette of the C7 transverse base superimposed on the superior articular process of C7. Final needle placement should be near the apex of the superior articular process of C7. Needle advancement should be checked frequently to not allow the needle tip to stray outside the triangular silhouette of the C7 superior articular process. If the needle tip strays, it could be advanced into the C8 intervertebral foramen or through the C6-C7 zygapophyseal joint. After contact with the superior articular process is made with the needle tip, a posteroanterior (PA) view should be done to confirm that the needle placement is against the lateral margin of the superior articular process. If the needle is noticed to be located at the C7 transverse process, then lateral views should be used for needle adjustments. After the needle is in the final position, 0.3 mL of contrast is injected to confirm spread over the intended target. After confirmation of the needle as not being epidural or intravascular, 0.3 mL of local anesthetic is injected. The needle is then withdrawn approximately 4 mm, and 0.3 mL of local anesthetic injection should be repeated. The depth of needle withdrawal can be gauged with a lateral view. This step of reinjection is done because of the variation of the C7 medial branch, which is displaced by the semispinalis capitis muscle away from bone rather than running across the surface of the articular process. Another anatomical variation to consider is the height of the C7 superior articular process. When a tall C7 superior articular process is present, an additional block at the junction of the transverse process with the superior articular junction may be needed because of variants in the C7 medial branch course where the nerve crosses the root of the transverse process.

A C8 medial branch block is needed to block the C7-T1 facet. The C8 medial branch block is approached similar to thoracic or lumbar medial blocks. The C8 medial branch courses over the base of the T1 transverse process. The needle tip is placed at the junction of the superior articulating facet and base of the transverse process of T1. The needle is advanced to this site via a trajectory down the x-ray beam. Contrast (0.3 mL) is injected under continuous “live” anteroposterior (AP) imaging to confirm the position and rule out intravascular uptake. After contrast confirms needle placement, 0.3 mL of local anesthetic is injected.

The third occipital nerve is thicker than the medial branches of the typical cervical dorsal rami; therefore, multiple target points are needed for blocking the nerves involving the C2-C3 facet joint. The target points are located along a vertical line that bisects the articular pillar of C3. There are three target points; the highest target point is immediately above the subchondral plate of the C2 inferior articular process. The lowest point is immediately below the subchondral plate of the C3 superior articular process. The middle point lies midway between these points, usually on the subchondral plate of the superior articular process of C3. Needle advancement is toward the middle of the three target points lateral to the C2-C3 facet joint capsule at the level of the joint. When the needle rests on bone and is in position, the needle is withdrawn slightly (≈3 mm) to ensure the needle has not penetrated the joint capsule. After injection of contrast to rule out venous uptake, injection with 0.3 mL of local anesthetic is done. The needle tip is then readjusted either to the cranial target point (anteroinferior margin of C2 inferior articular facet) or caudad target point (anterosuperior margin of C3 superior articular facet), where 0.3 mL of local anesthetic will also be injected at each spot. If contrast is used, distribution when one has achieved correct needle placement will show spread across the surface of the joint, where the target nerve is held against the joint by the overlying splenius capitis muscle (Figs. 13-3 to 13-7).

Fig. 13-3 Lateral view of C3, C4, and C5.

Fig. 13-4 Left lateral view of C3, C4, and C5. MBB, medial branch block; RFD, radiofrequency denervation.

Fig. 13-5 Lateral view of C2, C3, and C4.

Fig. 13-6 Anteroposterior view of C6. MBB, medial branch block.

Fig. 13-7 Anteroposterior view of C4 and C5.

Thoracic

Positioning

The patient lies in the prone position.

Needle Placement

The target landmarks for thoracic medial branches are the transverse processes. At the upper thoracic levels, the target point is more medial than compared with the lower thoracic levels. For the T1-T4 and T10 medial branch blocks, the target point is the junction of the superolateral corner of the transverse process. The T4-T8 nerves (the target point) do not lie on bone. The target point is the dorsal surface of the ribs that articulates with the transverse process. For the T11 and T12 medial branches, target points are similar to those for the lumbar medial branches. The target point is the junction of the root of the superior articular process and the root of the transverse process. To identify the target point, the ipsilateral oblique view is used to find the “Scotty dog” view. The radiographic target point for thoracic medial branch blocks is found cephalad to the superomedial margin of the transverse process. Cranial or caudal tilt of the C-arm is needed for optimal separation of the transverse process from the costovertebral junction. If the transverse process is obscured, better visualization of the transverse process occurs by rotating the C-arm to the opposite side of interest.

It is important to remember to name the target joints and target transverse processes appropriately. Their segmental nerves are different from those of the target nerves.

To decrease the risk of pneumothorax, the needle position should be dorsal to the target bone. The needle should be advanced down the beam of the x-ray. The needle is placed on the superior lateral corner of the transverse process at T1-T4 and T9 and T10. The needle is placed on junction of superior articular process and transverse process at T11 and T12.

Contrast is injected to confirm adequate spread covering the target area for the nerve and exclude intravascular uptake. At the midthoracic level (T5-T8), there is no validated technique for blocking the medial branches because of the unusual and variable anatomy of the medial branches at this level. The test dose of contrast under live fluoroscopy should show cephalad spread in an elongated ovoid shape covering the area where the target nerve lies (Figs. 13-8 to 13-11).

Fig. 13-8 Lateral view of T8 and T9.

Fig. 13-9 Anteroposterior view of T8 and T9. MBB, medial branch block; RFD, radiofrequency denervation.

Fig. 13-10 Lateral view of T8 and T9. RFD, radiofrequency denervation.

Fig. 13-11 Anteroposterior view of T10, T11, and T12. MBB, medial branch block.

Lumbar

Positioning

Lumbar medial branch blocks can be performed via the posterior approach, but it is not used because of the target obstruction via superior portion of the zygapophyseal joint. Therefore, the oblique approach is usually used. To perform the block with an oblique approach, the patient can lie prone on the fluoroscopy table with a cushion under the hips to decrease lumbar lordosis and have the C-arm of the fluoroscope rotated 10 to 20 degrees from the AP view to the side being blocked. The oblique view can also be obtained with the patient lying semi-prone with a cushion under their abdomen to tilt the target side upward.

Needle Placement

In the lumbar region, the medial branch nerve is located at the level of the transverse process or slightly superior and lateral to the medial border of the superior articulating process. The target for the L1-L4 medial branches is located at the junction of the superior articulating process and transverse process at which the target nerve crosses, midway between the superior border of the transverse process and the location of the mamilloaccessory notch. To find the target, an oblique view is needed with C-arm fluoroscopy. The goal is to obtain an optimal “Scotty Dog” view, which usually occurs at 10 to 20 degrees. The “nose” represents the transverse process, the “eye” represents the pedicle, and the “ear” corresponds to the superior articulating process. The target point is located behind the “eye” of the “Scotty dog,” so the puncture site on the skin is directly in line using a coaxial technique under fluoroscopy. A 1% lidocaine skin wheal is injected subcutaneously. The needle should be advanced directly down the x-ray beam to the target point. The needle tip can be curved to aid in steering the needle to the target point. The needle is advanced until the needle tip contacts bone where the superior articulating process, base of transverse process, and pedicle join each other. When this occurs, the needle tip is “walked” up over the superior aspect of the transverse process just until the tip slides over the top of the transverse process.

In the lateral view, the needle position should be viewed to make sure it is not too far anteriorly and that it is not in the neural foramen. Confirmation of needle position is done with oblique and PA views. In PA view, the tip of the needle should be against the lateral surface of the superior articular process, preferably the most medial end of the transverse process. Contrast 0.1 to 0.3 mL should be injected to confirm the absence of intravascular spread. The needle bevel should be directed caudally to prevent spread of injectate into the neural foramen and allowing the injectate to be deposited on the medial branch.

At the L5 level, is it important to remember the target nerve is not the medial branch of L5. The L5 medial branch is actually the L5 dorsal primary ramus, which is located against the bone along the superomedial aspect of the groove formed by the sacral ala and superior articulating process of S1. The target is along the superior articulating process sacral ala junction just below the upper margin of the sacral ala. The target is found using an oblique view. Less oblique tilt is needed when compared with the L1-L4 levels. Usually 0 to 10 degrees is sufficient for the L5 dorsal primary ramus. Too much oblique causes obstruction of the target point with the “Scotty dog” view because of the iliac crest being in the path of the needle. The skin puncture site should be slightly lateral to the target point but medial to the adjacent iliac crest. Needle advancement should be monitored under fluoroscopic guidance, making sure the needle tip is always below the upper margin of the sacrum with its course being in a ventral and medial direction toward the target point. When the needle contacts the bone forming the superior edge of the sacral ala, the needle is advanced carefully over the bone 2 to 3 mm. PA and oblique views are taken to confirm correct needle position. On the oblique view, the needle tip should be seen resting on the ala of sacrum, at the base of the S1 superior articular process. On the AP view, the needle tip should be against and under the lateral margin of the superior articular process of the sacrum. The needle bevel should be pointed medially to decrease risk of inadvertent spread of injectate into the S1 foramen or to the L5-S1 intervertebral foramen. Contrast should be injected to rule out intravascular spread and to confirm correct placement of the needle (Figs. 13-12 to 13-16).

Fig. 13-12 Lateral view of L4, L5, and S1. RT, right.

Fig. 13-13 Lateral view of L5 and S1.

Fig. 13-14 Anteroposterior view of L4, L5, and S1. MBB, medial branch block.

Fig. 13-15 Anteroposterior view of L5 and S1.

Fig. 13-16 Anteroposterior view of L4, L5, and S1. BLK, block.