Disclosure
Anesthesiologists have performed facet joint and nerve root blocks for more than 50 years. Initially, these blocks were performed by using palpated anatomic landmarks and a large amount of steroids and/or local anesthetics. As techniques have been refined, fluoroscopic and CT guidance have become popular in performing the injections, because this guidance allows more precise needle placement and thereby lowers the amount of injected pharmaceutical and the complication rate. While anesthesiologists have continued to perform the procedures, the trend toward radiologic guidance has resulted in a greater number of injections performed by radiologists, particularly neuroradiologists and musculoskeletal radiologists. The value of having radiologists perform the procedures is derived not only from their expertise in image-guided needle placement and radiologic anatomy but also from their more objective point of view. The treating physician is not influenced by the patient's physical findings or medical history, and he or she does not determine if the patient needs repeated injections. Separation of the referring physician and the treating physician eliminates any conscious or subconscious bias and can only benefit the patient. In the following article, the indications for facet and nerve root blocks are considered separately, for although the 2 injections are similar in nature and often performed in the same patient during a workup for back pain. The injections are designed to treat different pathologic processes. A short description of each technique follows, as well as a description of injection-related complications and coding issues.
Facet joint injections Typically, facet joint injections are performed as a part of a workup for back or neck pain. Since many patients do not have a readily identifiable cause for pain based on imaging studies and clinical evaluation, a stepwise process of different paraspinal injections is often performed. This process may include facet injections; epidural injections; selective nerve root blocks (SNRBs); and, in certain patients, discography. The injection of local anesthetic and steroids into the facet joint is diagnostic and potentially therapeutic. When optimally performed, the injection is made directly into the joint space, though for generations anesthesiologists have been successful in injecting around the joint. Pain relief following a precise intra-articular injection confirms the facet joint as the source of pain. Although some physicians advocate the use of only local anesthetic, most practitioners inject steroids as well, attempting to provide longer pain relief. Long-term relief (6 mo) can be obtained in 30-50% of patients. Patients referred for facet injections most often have degenerative disease of the facet joints. However, even if the facet joint appears radiologically normal, facet injections still may be of use, as radiologically occult synovitis can cause facet pain, particularly in younger patients. Postlaminectomy syndrome, or nonradicular pain occurring after laminectomy, is also an acceptable reason to perform facet injections. Patients with lumbar facet pain (so-called facet syndrome) typically present with back, buttock, or hip pain. If the patient has only back pain, this pain may radiate into the buttocks or hips, and the pain is typically worse with extension. A useful test is to ask patients to push the pelvis forward while standing with their hands on their hips because this movement typically reproduces facet-mediated pain. Radiculopathy, leg weakness, and leg numbness are not considered part of the facet syndrome and suggest nerve root compression, although this may be secondarily caused by facet hypertrophy. Occasionally, synovial cysts (out-pockets of the facet joint synovium) may be symptomatic. Most often, they cause foraminal or spinal stenosis. Typically, on T2-weighted MRIs, synovial cysts are seen as rounded areas of increased signal intensity with a peripheral rim of decreased signal intensity. These cysts are located adjacent to a facet joint. The injection of steroids into the associated facet joint is effective in resolving synovial cysts in 30-40% of patients, although repeated injections may be necessary. Cervical facet pain is not characterized as easily as lumbar facet pain, and it can occur with a variety of symptoms, depending on the level and the individual patient. Headaches, neck muscle spasms, and general or focal neck pain can originate from the facet joints. This pain is typically worse when patients extend or turn their neck. In particular, the upper cervical facets can often cause occipital headaches. As in the lumbar spine, radiculopathy or arm weakness and/or numbness should suggest an alternate diagnosis. Nerve root blocks Nerve root blocks are a useful tool in the workup for back pain, but they are used in a different patient subset than are facet joint blocks. Nerve root blocks attempt to anesthetize the desired nerve for diagnostic purposes, and steroids are used in an attempt to produce long-term relief, primarily in patients with radiculopathy. Multiple causes of radiculopathy have been discovered. Pressure on the nerve may result in an autoimmune response that can elicit pain. Because the venous drainage lies on the outside of the nerve, pressure on the nerve increases the venous pressure, causing a compartment syndrome within the substance of the nerve. This syndrome causes ischemia and pain within the nerve root, and the pain can be referred along the dermatome for the particular root. Phospholipase A has been implicated in radiculopathy as well. This chemical, the production of which is stimulated by extruded nucleus pulposus material, causes inflammation and pain in the adjacent nerve, even when no compression is present. Because steroids have anti-inflammatory actions, injections around the nerve root may reduce the inflammation, decreasing or eliminating the pain. Although an epidural steroid injection may produce the same effect, a SNRB is a more elegant and focused injection that has more diagnostic value than an epidural injection, particularly in surgical planning. When the 2 techniques are compared, injections of a large amount of steroid throughout the epidural space (epidural injections) are mostly of use when the pathology is located centrally in the spinal canal (eg, central disk extrusion) or when 1 or 2 individual nerves cannot be identified as the most likely source of the symptoms during physical examination or imaging studies. Epidural injection can be compared to a "shotgun blast" of steroids, covering a wide range of levels but placing only a small amount of steroid at each level. SNRB is more of a "sniper rifle" approach, with the injection of a relatively large amount of steroid around a specific nerve root. SNRB is useful when 1 or 2 nerve roots are considered to be the likely cause of the patient's symptoms. Nerve root blocks are useful primarily in the following subsets of patients with radiculopathy:
In addition, irritation of the perineural tissue and the sinuvertebral nerve, which innervates the annulus, may be helped with SNRBs. However, because the generated pain is usually nonfocal, multiple-level diagnostic blocks may be necessary to localize the painful level prior to a therapeutic block.
Materials
Technique After the procedure and its risks and benefits are discussed with the patient, obtain his or her written informed consent (see Complications). Using a model of the spine during the discussion facilitates the patient's understanding and confidence and hastens the consent process. Use of a heparin lock is optional because instances of atopic reactions, including anaphylaxis, and vasovagal responses have been noted during facet injections. Patients may be screened to see if they are at high risk for such reactions, and heparin locks can be placed in those patients. Practitioners can use a high-resolution C-arm or an angiography system that allows angulation of the tube in the lateral direction, or a fixed-tube fluoroscopic system can be used. When a mobile fluoroscopic arm is used, the patient is placed in a prone position, the overlying skin is sterilized, and the site is draped with sterile towels. In cervical injections, a pillow or bolster is placed under the patient's chest, and the neck is flexed. The patient's forehead is supported on a low cushion or folded towel. The facet joint is then localized by using fluoroscopic guidance. By using 1% lidocaine without epinephrine as local anesthesia, a 22- or 25-gauge spinal needle is directed into the desired facet joint. In the lumbar spine, 5-in needles are usually used, and either 3.5- or 5-in needles are usually used in the cervical spine, although 7-in needles are necessary in the lumbar spine in select patients, depending on their body habitus. In the lumbar spine, the facet joint is a curved 3-dimensional structure that can be confusing when the clinician attempts to find the posterior opening. To facilitate access, the joint can be visualized under fluoroscopy while the tube is angled laterally. Because of the shape of the joint, the posterior opening appears first as 2 parallel lines (see Image 1). If the tube is directed even further laterally, the mid portion and then the anterior opening are seen as similar lines that appear to offer access. In reality, the outer facet blocks any attempt to access the joints in this projection (see Image 2). In the lumbar spine, the lower levels typically require a steep obliquity, while less of an obliquity is required further up the spine. Initially, the needle is directed toward the medial part of the joint space opening with the bevel turned to lie medially and anteriorly and then incrementally moved into the facet joint. Placement of the needle near the opening of the facet joint is best accomplished under live fluoroscopy while a needle driver is used to protect the operator's hands from radiation exposure. However, maneuvering the needle into the actual joint space is best performed by using tactile clues to direct the tip into the joint space. In most patients, a pop is felt as the needle traverses the ligament, although this phenomenon is absent in severely degenerated joints. Contrast material may be injected to confirm needle location, especially at first, but with experience, confirmation of appropriate needle placement can be made by feel and by viewing anteroposterior and lateral projections. In most patients, the needle curves medially once inside the joint space (see Image 3). In patients in whom large osteophytes may block access to the joint, the superior and inferior aspects of the joint may be less involved and, therefore, easier to access. In patients in whom extensive hypertrophic changes have occurred, CT can be an invaluable tool in determining the best access route. When using a fixed fluoroscopic device, the patient may be rolled into an oblique position to visualize the joint space or the needle may be directed at the lowest portion of the joint. Sarazin et al introduced this technique to access the facet joint without using any obliquity by accessing the inferior recess. This approach lowers radiation dose to the patient, as the tissue thickness is decreased compared with that of oblique sections. Another advantage is that it does not require a mobile C-arm. In addition, the technique is useful when severe degeneration of the joint is present with large osteophytes. Some authors recommend injecting steroids at the site where the median nerve branches enter the bone, near the notch between the transverse process and the superior articulating process. Directing the needle to this location is easier, since the needle does not have to be actually placed into a bony compartment. However, some groups suggest that this injection is less effective than intra-articular facet blocks. Cervical facets pose a different problem because of the severe coronal angulation. Two methods of approach may be used: the direct posterior approach and the posterior lateral approach. The posterior approach requires a marked caudocranial angulation of the tube, and the needle insertion site is typically in the upper back instead of the neck. Usually, 5-in needles are necessary in this technique, and the posterior approach is technically challenging (see Image 4). An alternative is to direct the tube laterally until the side of the facet is visible, and using a 3-in needle, attempt to place the needle into the joint in this manner. A disadvantage is that the joint space may not be as accessible via this route, although the cervical facet nerve can be injected if joint access is not obtained. Once the needles are in place, a mixture of steroids and 0.25% bupivacaine is injected into each joint. The exact amount may vary, although the total amount of injected fluid is not usually more than 2 mL in the lumbar spine and 1.5 mL in the cervical spine. Because the capacity of a lumbar facet joint is 1.0-1.5 mL and a cervical facet joint is 0.5-1.0 mL, injecting more than the joint can hold may result in a nonselective injection, which decreases the diagnostic accuracy of the procedure. Overfilling the joint usually results in anterior rupture into the epidural space, which may occur even with small amounts of fluid as the anterior ligament is often fenestrated or partially degenerated. A common mixture is Celestone or Kenalog with bupivacaine, although other steroids and local anesthetics may be used. Use caution when injecting facets with associated foraminal or spinal stenosis because transient swelling of the joint may temporarily result in exacerbation of the patient's symptoms. The patient is observed for 15 minutes after the procedure to document pain relief and to monitor the patient for allergic reactions. Because of the small size of the needles, activity restrictions are not necessary. |
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Materials
TechniqueFluoroscopy vs CT and CT fluoroscopy for guidance Nerve root blocks have traditionally been performed by using fluoroscopic guidance, and this is still the most common method of localization. Since the advent of CT, and more recently CT fluoroscopy, these modalities are beginning to be more widely used to direct nerve root blocks. Proponents of fluoroscopy cite decreased procedure time and cost, whereas CT offers the advantages of no contrast material, more precise needle tip placement, and visualization of important vascular structures. Time limitations often prevent the use of traditional CT guidance, especially in busier units, but with CT fluoroscopy, the time differences between the 2 techniques are diminished markedly. The cost differential between the 2 techniques is 0.6 relative value units (RVUs), and this should be taken into account when a technique is chosen. The choice of technique should primarily be based on the physician's comfort, and ultimately, in skilled hands, there is probably no real difference. General procedure Informed consent is obtained from the patient after he or she receives an explanation of the procedure, risks, and benefits. With the fluoroscopically guided technique, the patient is placed in the prone or slightly oblique position. The skin is sterilized and then anesthetized with a local anesthetic, such as pure 1% lidocaine or a 1:1 mixture with 0.25% bupivacaine. The neural foramen is approached from a posterolateral direction with a 20-, 22-, or 25-gauge spinal needle; the size being individual preference. (The author uses 22-gauge needles). A thorough knowledge of vertebral anatomy is essential to optimize needle tip placement. As the nerve root travels within the superior part of the neural foramen, the needle is advanced, under fluoroscopic guidance, toward the 5- to 6-o'clock position of the pedicle (the 12-o'clock position of the foramen). The needle tip is ideally placed in an inferior position. The needle passes directly anterior and lateral to the superior articulating process of the adjacent facet, and various degrees of angulation are necessary in different patients, depending on both the existing anatomy and on the presence or absence of hypertrophic changes. As the postganglionic nerve continues in an inferior and lateral direction from the foramen, as well as anteriorly, the needle should be directed appropriately if placement access into the outer foramen is blocked. The needle tip should be slowly advanced until either the patient experiences radicular pain or until the posterior surface of the vertebral body is encountered (see Image 5). At this point, visualizing the needle tip in the lateral plane allows it to be maneuvered so that it rests in the upper central portion of the neural foramen, directly adjacent to the nerve root and dorsal root ganglion (see Image 6). The location of the needle tip is confirmed by using an injection of 1-4 mL of a nonionic contrast material, which is approved for use in the thecal sac. If the needle has been properly placed, the contrast will flow around the nerve root and may cause radicular pain (see Images 7-8). Correlation of any elicited radicular pain, either from the contrast enhancement or from direct contact of the nerve with the needle tip, with the patient's usual pain pattern is useful in confirming that the correct level has been injected. Once appropriate needle placement has been confirmed, 1% lidocaine with or without bupivacaine (for a diagnostic block) or 1-2 mL of an appropriate steroid mixed with a small amount (0.5 mL) of bupivacaine (for a therapeutic block) is then slowly injected. Examples of appropriate steroid doses include 6 mg Celestone or 80 mg Depo-Medrol. It is important to use as small a total volume as possible if the injection is at least partly for diagnostic reasons, to prevent the spread of anesthetic to adjacent nerve roots or into the epidural space. CT-guided injections are performed by using the same patient positioning as in fluoroscopic-guided injections. A long marker is placed on the skin. (An unfolded paper clip placed lengthwise along a strip of silk tape is an inexpensive and effective marker.) Images are acquired through the desired neural foramen to determine and measure the best path to the nerve (see Image 9). The needle is advanced by using either sequential CT sections or CT fluoroscopy until it lies just adjacent to the nerve root (see Images 10-11). The source of the nerve root irritation (eg, lateral disk, intraforaminal stenosis, posterior disk) determines how central the injection should be. Once the needle has been optimally placed, steroids and bupivacaine are injected. Cervical SNRB with fluoroscopic guidance When a cervical SNRB is performed using fluoroscopic guidance, the patient is placed in the supine position. The skin entry zone should be approximately at the same level as the foramen to slightly anterior. A 25- or 22-gauge spinal needle is directed at the appropriate neural foramen; the superior facet a useful landmark as a target. The needle should be directed into the posterior portion of the foramen to avoid injury to the vertebral artery. The needle should be in the outer portion of the foramen, and, in fact, the needle can be placed outside the foramen with similar efficacy and less risk. The injection of contrast material is critical to outline the nerve root (see Image 12). Contrast should never fill vessels, and does not normally fill the subarachnoid space. The total volume of the local anesthetic and steroid should be smaller than that used in the lumbar spine because of the smaller anatomy. A maximum of 0.5 mL is recommended for a diagnostic block and 1.5 mL for a therapeutic block. Cervical SNRB with CT or CT fluoroscopic guidance When cervical SNRBs are performed with CT or CT fluoroscopic guidance, the patient undergoes scout imaging, and the nerve root is identified as in the lumbar and thoracic spine apart from the supine positioning. The skin entry site is chosen, measured, and marked. A 25- or 22-gauge 3.5-in needle is inserted posterior to the jugular and carotid vessels and maneuvered to just outside the neural foramen. Again, the needle tip should stay in the posterior portion of the foramen (see Image 13). In some cases, the needle may need to be inserted through the neck musculature or through a preplaced 1.5-in 20-gauge needle to prevent the weight of the needle hub from displacing the needle tip anteriorly during scanning. An alternate method is to use a few sterile gauze pads to provide a cushion on which the needle hub can rest while the needle is not actively held. Once the needle has been placed, confirmation of extravascular location of the needle tip should be obtained by injecting a small amount of contrast material (see Image 14). Postprocedural care The patient should be cautioned that transient weakness may occur in the distribution of the injected nerve root if the motor root also becomes anesthetized. Take care to support the patient when he or she stands up and for the first 15 minutes after the injection. Lower bupivacaine doses result in a lower incidence of motor weakness, but with proper needle placement, motor weakness should be a relatively rare occurrence. Observe the patient for at least 15 minutes after the procedure to document pain relief and to monitor the patient for motor weakness and allergic reactions. Because of the small size of the needles, activity restrictions are not necessary.
Complications Complications are rare during either facet joint injections or nerve root blocks, but they may include bleeding, infection, and allergic reactions. Intravascular injection may be harmless, but it results in a suboptimal or false-negative result. Furthermore, intravascular injection can be dangerous if the agent injected into the vertebral artery or radicular branches that enter the neural foramina at various levels. Spinal cord infarcts have occurred from both cervical and lumbar SNRB, and a case of a cord infarct during an S-1 SNRB has even been reported. Whether or not these complications were due to an intravascular injection versus vasospasm or direct arterial injury or some mechanism that is not understood at this time is not clear, but, in this author's opinion, contrast injection is recommended to at least potentially reduce the risk of intravascular injection as well as the necessity, in today's environment, to practice somewhat defensively. Spinal anesthesia may occur if local anesthetic is inadvertently injected into the nerve root sleeve. Prompt recognition of this potentially disastrous complication is vital during cervical procedures, because the patient's breathing may be arrested. The patient's head should be immediately elevated after the injection to ensure that the Marcaine flows inferiorly, and intubation supplies should be readily accessible. Some practitioners elevate the head of the table during cervical injections to help prevent this complication. Some patients experience adverse effects from the steroids. These effects can include insomnia, nightmares, and nervousness, although these are transient. Consider the total steroid dose when performing injections at multiple levels. In addition, there is always the risk of a life-threatening idiopathic reaction to any injected medication. Contraindications Contraindications to paraspinal injections include a history of allergy to local anesthetics or steroids; coagulopathy; or, in the case of facet joint injections, severe foraminal stenosis (which can become worse if an injection is made into the joint itself). Severe foraminal stenosis is a relative contraindication to intra-articular facet joint injections. Injections into the facet joints can cause joint swelling, worsening a pre-existing foraminal stenosis. While small amounts of steroid may be injected gently, at levels with severe stenoses, parafacet (median nerve root block) injections should be considered.
The issue of appropriately coding the procedures for billing purposes is important, because miscoding can lead to accusations of fraud, even if it occurred unintentionally. Coding paraspinal injections can be challenging because of the numerous coding changes enacted by Medicare over the last few years. The most recent Current Procedural Terminology (CPT) should be used because the codes appear to be changed in some way almost every year. Facet joint injections Lumbar facets should be coded as 64475 for the first level and 64476 for each additional level, by using the –50 modifier code if both facets at a given level are injected. Cervical and/or thoracic facet injections should be coded as 64470 for the first level and 64472 for each additional level, again with the –50 modifier code as necessary. If fluoroscopic guidance is used, the 76005 code can be used for each injection, whereas 76360 is used for CT guidance. These procedure codes are linked to International Classification of Disease, Ninth Revision (ICD-9) codes, which were modified in early 2000. Currently, Medicare approves facet injections for use in spondylosis without myelopathy but not in spondylosis with myelopathy (for obvious reasons) or in postlaminectomy syndrome. Current accepted ICD-9 codes include 721.0, 721.2, 721.3, 721.90, 722.81, 722.82, and 722.83. Nerve root blocks Lumbar nerve root blocks are coded as 64483 for the first level and 64484 for each additional level. Cervical and/or thoracic nerve root blocks are coded as 64479 for the first level and 64480 for each additional level. Again, 76005 or 76360 codes should be used for needle guidance, depending on whether fluoroscopic or CT guidance was used.
Steroids are widely used in nerve root blocks, epidural injections, and facet joint injections in an attempt to provide temporary relief from pain. When SNRBs are performed for disk herniations, the goal is to provide pain relief for enough time to allow the extruded disks to shrink. In more than 70% of disk herniations, the disk material resolves on its own, given enough time; however, this process can take well over a year. Despite this widespread use, for many years, the lack of randomized controlled trials resulted in questions about the efficacy of steroid injections, and the result of one study suggested that there was no difference between saline and steroids in relieving pain in the facet joint. One prospective, randomized, controlled, double-blind study by Riew et al was performed in patients who were surgical candidates and who initially wished to undergo surgery to relieve radiculopathy from nerve root compression. Approximately 71% of those who underwent SNRB with betamethasone and bupivacaine elected not to have surgery (follow-up, 16 months), whereas only 33% of those injected with bupivacaine alone avoided surgery. Zennaro et al found the greatest efficacy in patients with foraminal stenosis, as compared with those who had foraminal disk herniations. Devulder found that SNRB with steroids was associated with decreased treatment scores in patients with failed back syndrome, as compared with scores in those not treated with steroids. Most studies report an average time of pain relief as 1-3 months in those patients that have initial improvement, although some studies have described longer relief in a high percentage of patients.
In most patients, the first 15 minutes is sufficient to determine whether the injection is successful in alleviating symptoms. However, the author has treated patients in whom no initial relief was experienced with bupivacaine, yet the patient's symptoms resolved over the next few days. Do not conclude that the injection is unsuccessful until 1 week after the injection. Always review the patient's radiologic file prior to each procedure. This review prevents confusion when the order reads, eg, "L5 nerve root block," but the patient has transitional anatomy and 4 lumbar-type vertebrae. In addition, in some patients, MRIs may indicate other reasons for the symptoms, such as disk extrusions or synovial cysts that were missed initially. Good service is important and, if possible, offering same- or next-day service is best, at least initially. Send a letter to the referring clinician describing the procedure and any further recommendations. This information expedites the patient's care, making for a positive experience for both the patient and the referring physician. Most primary care physicians are grateful for any suggestions regarding the further treatment of patients with low back pain, because this disease is often difficult to treat. In recent years, a number of reports have described cases of spinal cord infarcts following selective nerve root blocks, both in the lumbar and cervical spine. At this time, although theories abound, the etiology remains uncertain. While intra-arterial injection is an easy and popular theory, most of the reported cases had contrast injected prior to steroid infiltration, suggesting an alternative cause, such as vasospasm or direct arterial injury from the needle tip. Importantly, include this potential devastating complication in the consent process because absolute safety cannot be completely ensured; thankfully, however, these types of complications have been rare.
Paraspinal Injections: Facet Joint and Nerve Root Blocks excerpt | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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