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9 Articles in Volume 15, Issue #3
Abuse-Deterrent Formulations
Ask The Expert: False-Positive Screen for Benzodiazepines
Clinical Diagnosis of Centralized Pain in the Age of ICD 10
Editor's Memo: The WHO Pain Treatment 3-Step Ladder
Letters to the Editor: Hormone Dosing, Adhesive Arachnoiditis
Pain in Women
PROMIS Pain-Related Measures: An Overview
Selective Interventional Spinal Techniques: Injections and Ablations
Transcranial Direct Current Stimulation (tDCS): What Pain Practitioners Need to Know

Selective Interventional Spinal Techniques: Injections and Ablations

The use of appropriate, selective injection techniques and radiofrequency ablations, combined with a comprehensive, personal rehabilitation plan, is more beneficial than isolated treatment strategies.

Selective spinal and joint injections are being performed with increasing frequency in the management of acute and chronic disorders of the musculoskeletal system. Effective treatment of chronic spine and joint pain requires accurate identification of the correct pain source. Interventional pain specialists play a critical role in the selective provision of spinal injection techniques to diagnose and treat musculoskeletal pain disorders.

One of the most common pain disorders seen by interventional pain specialists is spine and sacroiliac joint (SIJ) pain. The facet (zygapophyseal) joints can be significant source of spinal and extremity pain.1-4 These joints, and the nerves innervating them, can produce cervical, thoracic, lumbar, and referred pain (head, shoulder, scapula, buttock, thigh, and leg). The SIJ, which also is innervated, has been shown to be a significant source of referred pain in the buttocks, hip, and posterior thigh.

This article will review the benefits of spinal injections in the diagnosis and management of spinal joint pain and discuss specific treatment techniques for SIJ pain.

Diagnostic Benefit

Injection techniques have obvious diagnostic and therapeutic value—they are extremely useful tools for precisely diagnosing and localizing the spinal pain generator(s). Therefore, the goal of diagnostic selective nerve or joint injections is to differentiate the qualitative and quantitative contributions of discogenic, radicular, and posterior element axial pain sources. This is especially true in the setting of multilevel spine and joint disease and in situations where imaging or electromyographic tests show no obvious abnormalities.

The injections can be directed at specific target sites in and around the spine. Because of the precise needle localization needed and the technical difficulty of performing these procedures, the use of fluoroscopy and contrast dye are essential. Epidural injections frequently are performed without radiographic guidance, but incorrect needle placement into subcutaneous, intraligamentous, and intravenous locations occurs in up to 25% of cases. Therefore, fluoroscopic visualization with an epidurogram, perisheathogram, or arthrogram is highly recommended, especially in postoperative cases in which anatomical boundaries are disrupted and imaging studies are difficult to interpret accurately.

Sometimes diagnostically reproducing the pain trigger during these procedures facilitates accurate identification of the painful structure. Typically, non-affected nerve roots will not trigger a severe pain response when they are mechanically irritated by a spinal needle or contrast dye. In addition, when combined with a local anesthetic or corticosteroid solution, spinal injections can provide temporary pain relief—which would indicate a therapeutic benefit and a positive response to the procedure.

Comparison of pain levels before and after the injections—by patient verbalization, pain procedure diaries, and visual analog scales (VAS)—helps the practitioner gauge the response to the anesthetic procedures. Afterwards, provocative maneuvers, such as assessment of spinal range of motion, straight leg raises, and ambulatory capabilities before and after the injections also may help the practitioner determine the contribution of that particular site as the actual painful source. Exaggerated or extreme pain behaviors during these assessments provides information about nonphysiologic causes of pain—usually provided from before and after procedures such as that noted on pain procedures diaries or VAS pain scores comparisons. 5-9

Indication for Procedures

These selective spinal and joint injections are indicated specifically for medically stable patients and are considered outpatient, minimally invasive, minor surgical procedures. For patients with failed back surgical syndrome and for those considering operative interventions (eg, spinal fusion, microdiscectomy, or laminectomy and decompression), combining injection procedures with an accurate history and physical exam and appropriate imaging and/or electrophysiologic studies can help the interventional pain specialist and/or the spinal surgeon develop a more directed and efficient treatment program. Spinal injections also can be used as an adjunct to rehabilitation and physical therapy, proving pain relief, increasing range of motion before and/or during the rehabilitative process, and allowing the patient to participate more fully in the therapy program.

Before performing any diagnostic and/or therapeutic procedures for spinal and joint pain, the interventional pain specialist must understand the radiographic anatomy of the facet and larger joints, most importantly the nerves involved (Figures 1 and 2). Each of the facet and larger joints have a dual nerve supply. For example, the facet joints are innervated by the medial branch of the dorsal ramus, one from the level above the target joint and one from the level below the target joint.

Although numerous interventional procedures are used to treat spinal-related pain conditions, a few of the most common types of diagnostic and therapeutic spinal injections are listed in Table 1.10-15

 

Sacroiliac Intra-articular Joint

The sacroiliac joint (SIJ) can be a primary or secondary source of lower back pain or dysfunction that should be thoroughly investigated and considered. Studies using controlled blocks to identify the pain generator have shown that the prevalence of SIJ pain in those with lower back and buttock pain is approximately 15%.16,17 The importance of the SIJ often is overlooked because its anatomical location makes it difficult to examine in isolation, and many SIJ clinical tests place mechanical stresses on contiguous structures. In addition, many other structures may refer pain to the SIJ.

Before 1934, the SIJ was felt to be the primary cause of lower back pain. However, a study by Mixter and Barr focused attention on the disc as the primary cause of lower back pain.18 Recently, attention has been refocused on the SIJ as a primary or secondary cause of lower back pain and disability. SIJ dysfunction is first suspected when a patient presents with a suggestive mechanism of injury (direct fall on the buttocks, rear-end motor vehicle accident with ipsilateral foot on the brake at the moment of impact; fall into a hole with one leg in the hole and the other leg extended outside). Pain diagrams, which document a predominant pain zone extending from the posterosuperior iliac spine to the caudal portion of the joint, can accurately predict which patients with suspected discogenic or posterior element pain have symptomatic SIJs on provocative injection.

Physical examination findings include a positive seated flexion test, standing flexion test, or Gillet test for aberrant sacroiliac motion, a positive Patrick’s manuever for ipsilateral SIJ pain, and tenderness over the ipsilateral SIJ, sacrotuberous ligament, piriformis muscle, and pubic symphysis. Diagnostic confirmation is attained when symptoms are reproduced upon distention of the joint capsule by provocative injection and subsequently abated with an analgesic block. The ligamentous integrity of the joint is established arthrographically.

Fluoroscopically-guided, contrast-enhanced, intra-articular injections are one subset of the treatment techniques available for SIJ pain.14-22 Because diagnostic (with anesthetic only) and therapeutic (with corticosteroid and anesthetic agents) SIJ injections are invasive, the procedure should be reserved for patients who have SIJ pain, have failed to respond to aggressive functional restoration (eg, physical therapy, osteopathic, or chiropractic manipulation and stabilization exercises) or who have reached a plateau in the therapy process. Fluoroscopic evaluation is essential to ensure accurate intra-articular injections, due to the irregular and convoluted joint surface and anatomy.

The procedure has a very low morbidity and complication rate, however preprocedural patient education, precautions, and preparation still are essential. The author recommends postoperative application of ice to the affected area, a short course of muscle relaxants and nonsteroidal anti-inflammatory drugs, and a short, but intense, course of physical therapy, with emphasis on SIJ mobilization and stabilization exercises.

Facet Joint and Medial/Lateral Branch Blocks

Goldwaith first identified the lumbar zygapophyseal joint (z-joint) as a source of pain in 1911.23 In 1933, Ghormley coined the term “facet syndrome,” which referred to the symptom complex associated with pain emanating from this joint.24 Subsequently, various types of localized, pseudoradicular, and sclerotogenous referred pain from this joint have been described, in the lumbar, cervical, and thoracic regions. Injections to diagnose and control pain originating from the z-joint should always be used as an adjunct to aggressive, conservative spine care (ie, physical therapy or manipulation treatments, pain-relieving medications, and other pain-relieving modalities).

These injections have become an important, yet sometimes controversial, part of nonsurgical spine care. Somatic, axial spine pain has various sources—facetogenic, myofascial, discogenic, or combination of all of these sources. The value of these injections has been disputed, but when they are used appropriately, they can provide both diagnostic and therapeutic benefit. Fluoroscopically guided contrast-enhanced z-joint injection procedures help to evaluate the z-joint as an isolated source of spine-related pain. These procedures also may provide short- and long-term pain relief through the therapeutic effects of the anesthetic and corticosteroid used. Pain relief allows patients to advance through their rehabilitation program more efficiently and rapidly, which can result in overall improved patient function.

Diagnostic Gold Standard

Because no reliable, non-invasive clinical findings or techniques exist for the accurate diagnosis of z-joint–mediated pain—and because the clinical features of z-joint pain, discogenic, ligamentous/muscular, and SIJ pain overlap greatly—fluoroscopically guided z-joint injections of local anesthetics commonly are considered the gold standard for isolating or excluding the z-joints as the facetogenic, axial pain source of spine or extremity pain.

Either intra-articular or medial branch blocks can be used in the diagnostic work-up. Physiologic analgesia is the underlying principle—pain relief after blockade of the nociceptive fibers implicates the blocked structure as the source of pain. Therefore, analgesia after local anesthetic blocks of a z-joint or its nerve supply indicates that the blocked site or joints are indeed the primary pain source. The primary indications for z-joint and medial branch injections are listed in Table 2. Potentially important, but not diagnostic, clinical findings include the site of maximal segmental or direct articular tenderness, concordant pain on provocative segmental testing, articular restriction and local soft-tissue changes, such as increased muscle spasticity, and pain in recognized z-joint referral zones. Studies show that certain levels of the spine, including C2-C3, C5-C6, L4-L5, and L5-S1, appear to be involved more commonly.

Contraindications to these injections are the same as for the epidural steroid injections (see Table 3). In addition, the procedure should be avoided if patients show signs of abnormal clotting status or infection (local or systemic), or have allergies to the injection material (contrast dye, corticosteroid, or anesthetic). Complications from z-joint block procedures are rare and include increased z-joint pain, local needle site pain, chemical menigism (chemical irritation usually by steroid sensitivity or side effects commonly noted: “facial flushing, jitteriness, or secondary leg swelling), spinal nerve root or subdural injections are rarer still. The studies that evaluate treatment of spine pain of z-joint origin (documented by analgesia after single diagnostic blocks) assess the efficacy of isolated corticosteroid z-joint injections, posterior lumbar fusion, and radiofrequency nerve ablations (RFNAs). Documented improvements of >70% in pain from lumbar z-joint and diagnostic L-medial branch blocks prognosticate longer-term (months/years) of beneficial axial pain improvements.25-28

Conventional RFNA

Facet or z-joint nerve ablation, also known as facet denervation/neurotomy, facet rhizotomy, or RFNA is used to treat chronic posterior element pain that is unresponsive to more conservative measures. It involves interruption of the facet joint nerve (medial articular branch of the posterior primary ramus).

Neurotomy of the medial/lateral branch nerves was devised on the premise that pain from a z-joint could be relieved by coagulation of its afferent nerve supply (ie, denervation or selective radiofrequency burning of these sensory nerves). By blocking conduction in these sensory nerves, coagulation would simply reproduce the effect of a diagnostic medial/lateral branch block (using anesthetic and/or corticosteroid) for a longer period of time—approximately 6 to 18 months.25-28

The first known use of radiofrequency (RF) ablation was in 1931, when Krischner treated trigeminal neuralgia with thermocoagulation of the gasserian ganglion.29 In the late 1950s, the first commercial radiofrequency machine became available.30 The use of radiofrequency devices in practical medical applications originally was described by Rees in 1971.31 In a study of 1,000 patients, RFNA was performed by percutaneous insertion of a long knife into the paravertebral muscles to dissect to lumbar segments for access to the medial branch nerves off of the posterior primary rami location. The author claimed a success rate of 99.8%.31 In 1972, Shealy attempted to repeat Rees’ results and achieved only a 50% success rate in 29 patients.32 Subsequently, Shealy described the modern percutaneous technique of RFNA.33

Radiofrequency is a high-frequency current produced by a generator that passes from the electrode to the grounding pad through the body tissues in an electric circuit. The electromagnetic field around the tip of the electrode causes the tissues to heat up and a lesion is formed if the temperature within the neuronal tissues exceeds 40°C.34 The lesion size correlates with the electrode size, temperature generated, duration procedure, and local tissue characteristics. The lesion tends to be an oval shape parallel to the needle, so, ideally, the needle should be parallel to the targeted nerve—at a 15° targeted curve.35 After the RFNA procedure, scar tissue forms, as a result of coagulation, an acute inflammatory reaction, necrosis, and collagen deposition over a period of 3 to 8 weeks.36

Indication

RFNA is indicated in patients with chronic, recalcitrant pain of cervical, thoracic, or lumbar facet joint origin. Clinically, facet joint nerve pain is difficult to evaluate, but it may be suspected when axial pain is greater than extremity pain, extremity pain is in a vague distribution, no neurological changes are noted, and pain is greatest with extension. Because the pain symptoms may mimic other conditions, facet joint nerve pain should be confirmed by diagnostic anesthetic facet joint nerve blocks (FJNBs)/medial branch blocks (MBBs). If MBBs do not substantially (>50%) relieve the pain complex for the life of the local anesthetic, other sources of pain should be explored. Although this procedure remains controversial, numerous studies have reported its efficacy in the treatment of chronic posterior element pain.12-15, 22-41

Cooled RFNA/Neurotomy

Because conventional (monopolar) RFNA has a limited lesion field, cooled RFNA (originally developed for treating ventricular tachycardia and cancer tumors) has been proposed to fulfill the need for increased lesion size during procedures that are complicated by difficult nerve location (eg, thoracic facet pain, SIJ pain). Cooled RF electrodes include a thermocouple at the active electrode tip to provide a temperature-controlled lesion formation. This involves water-cooling of the active electrode tip during the duration of the process without tissue charring at the electrode tip (ie, since the temperature is usually 60° C for cooled RFNA, compared to 80-90° C for conventional/monopolar RFNA). The generator monitors the tissue temperature with the thermocouple and delivers precisely enough power to achieve the exact set temperature. If the targeted tissue is heated slowly, more power is delivered—a higher steady state power output is required to maintain the targeted tissue temperature during lesion formation. A review of the literature revealed significant benefits of larger lesion sizes that can lead to a higher chance of neuroablation of smaller sensory nerves. For this reason, cooled RFNA has been shown to provide improvements over conventional (monopolar) RFNA.42-50

In the laboratory (Kimberly-Clark HealthCare Corp), the lesions produced from cooled RFNA reveals a more spherical lesion, whereas conventional (monopolar) RFNA produced a more ovoid-shaped lesions (Figures 3 and 4).42 The cooling of the active bipolar tip will yield a larger lesion, by removes excessive heat that localizes around the electrode tip. Cooled RFNA has been shown to increase lesion size by affecting lesioning time, temperature, fluid injection, electrode tip site and spacing. The cooled RFNA model allows for intensified power output, which enlarges the electric field generated and increases the specific heat absorption rate. With higher power delivery, the neuroablative RF effect occurs at a further distance from the electrode tip.

 

Theoretically, the larger lesions obtained from cooled RFNA may increase the probability that a targeted sensory nerve will be captured in the “sphere” of tissues neuroablated. Furthermore, cooled RFNA provides larger distal lesion projections, which is advantageous when approaching the targeted nerve in a conventional perpendicular approach. The larger lesions and distal projections obtained by cooled RFNAs may allow improved results, even if health care providers place probes imprecisely.42-50

Both conventional and cooled RFNA probes can also be utilized in a bipolar fashion where heat is generated between 2 points (2 probes). Whereas the monopolar model generates along a longitudinal direction, the bipolar model propagates heat “quasi-spherically” and creates larger lesions than the monopolar model in both cases—with the cooled probes creating the largest lesion field. Currently, the cooled RF bipolar configuration is primarily utilized during the intradiscal biacuplasty procedure to ablate sensitized nerves from internally disrupted discs. 

Complications

Potential complications of both conventional and cooled RFNA/neurotomy procedures remain relatively low and inconsequential.41,50,51 Both produce actual tissue destruction of sensory nerves primarily, but injury to vital structures, especially spinal nerves, is very uncommon, in large part because of the physiological testing conducted before each neuroablative lesioniong procedure. To ensure a lower risk of complications and that the active tip of the electrode cannula will not be in close enough vicinity to harm any spinal nerves or other unintended targets, sensory and motor testing is carried out before each procedure.

Although the common exacerbation of pain following RFNA is common, the majority of these are cutaneous—related minor pain after the postoperative period (itching, burning, hypersensitivity)— usually lasting a few days to a few weeks after the neuroablative procedures. Infrequently, some patients will experience an uncomfortable dysesthesia (“sun-burn feeling” over the affected skin), allodynia (pain to light touch), but rarely postprocedural neuropathic pain (ranging from 0.5%-9.2% per lesion), transient ataxia, vasovagal reactions, bleeding, infection, thecal sac puncture, headaches, allergic reactions to medications, pneumothorax in thoracic procedures, and/or permanent injury to the spinal nerves. Adverse reactions are more common with cervical/thoracic and SIJ RFNA, but they usually resolve over several weeks. These dysesthesias occur from partial denervation of the lateral branch of the posterior primary ramus, which supplies a variable region of cutaneous innervations overlying the spinous processes.41,49-51

Discussion

Pain is one of the most complex problems medicine faces today. Compartmentalization of pain problems into physiological, physical, and psychosocial categories may be useful diagnostically, but not therapeutically. Pain clinicians must work synergistically to achieve therapeutic success.

In this scenario, the interventional pain specialist is a valuable and often crucial member of the pain management team. Injury and tissue-specific therapeutic exercise programs must form the basis of physical rehabilitation and functional restoration protocols. The program can combine a core of sedentary exercises, coupled with the injury-specific exercises. Importantly, the protocol must expand to encompass psychotherapeutic intervention in chronic pain conditions. Neuromuscular reconditioning must be included to ensure a function-specific, task-oriented program. Essentially, and most importantly, the program must be geared to enhance and foster functional recovery for the affected patient.

Injection techniques play a major role in the management of disorders of the musculoskeletal system. Various procedures and techniques have been used over the years, and are being developed for the interventional management of pain. During the 1990s, more novel injection techniques have been developed, and traditional injection techniques have been refined based on technologic advances in imaging modalities and a clearer understanding of the pathomechanics and the physiochemistry of pain. A few of the most common procedures and a few of the newer techniques were mentioned briefly as options available to the patient in need of pain management.

Summary

The role of the interventional pain specialist in the diagnosis and management of spinal-based pain syndromes, peripheral joint dysfunction, and soft-tissue abnormalities has become more prominent. Many of the painful states seen by an interventional physiatrist and pain specialist can be helped greatly by using a rehabilitation program that may include injection techniques. Some of these interventional procedures are relatively simple and common to perform, whereas others can be technically challenging and should be done only by a specialist with adequate experience and knowledge to perform these procedures accurately and in a timely fashion. It is important to emphasize that the use of fluoroscopy to aid in proper needle placement now is the standard. Fluoroscopic direction of needle placement increases the accuracy and efficacy of several types of selective spinal procedures. Despite the newly found field of interventional pain management, physiatrists remain rooted in the emphasis of functional assessment and physical medical management. Indeed, it is this concept, intrinsic and unique to the interventional pain specialist, that centrally places him/her in an ideal position to be the leader in injectional pain management.

Last updated on: April 15, 2015
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