Coccyx pain (coccydynia) apparently occurs far less commonly than lumbosacral pain. Coccydynia can be a severe and persistent pain, causing significant suffering, frustration, and functional limitations (199). These patients often have a history of coccyx trauma (e.g., from a fall or childbirth) resulting in contusions, fractures, dislocations, or other injuries. However, other cases are idiopathic. Typical symptoms include focal tailbone pain, particularly worse with sitting and sometimes immediately worse upon going from sit-to-stand (199). Careful screening should seek to exclude malignancies of the spine (e.g., chordoma) and intrapelvic structures (e.g., rectum) (199,200). Useful diagnostic studies may include x-rays, MRI, CT scans, and colonoscopy (199). Dynamic radiographs comparing coccygeal alignment and angulation while sitting (weight bearing on the coccyx) versus standing may reveal dynamic instability (dislocations) not visualized via non—weight-bearing studies (201,202).

Injections for coccyx pain may include focal corticosteroids placed at the posterior coccyx or into a sacrococcygeal or coccygeal joint, ideally performed under fluoroscopic guidance to maximize injection accuracy and minimize the risk for inadvertent puncture of the rectum or other nearby structures. Diagnostic nerve blocks can include local anesthetic blockade of the somatic posterior coccygeal nerve fibers as well as the sympathetic nerve fibers (ganglion Impar) anterior to the coccyx (203–207). For both diagnostic and therapeutic injections, it is frequently helpful to simultaneously block both the anterior (sympathetic) and posterior (somatic) nerves. This combination can more completely shut off all afferent inputs from the coccyx, with resultant relief implying that the coccyx is the source of pain. Also, effective local anesthetic blockade can provide therapeutic benefit, sometimes including complete and permanent relief (208). The mechanism is perhaps via disrupting hyperactive and/or hypersensitive afferent reflex arcs or sympathetically maintained pain. The various technical approaches to the ganglion Impar include injecting a spinal needle from inferior to the coccyx (above the anus), or passing the needle through the sacrococcygeal joint or through the intracoccygeal joints (203–207). Fluoroscopic guidance is crucial for safe and effective performance of sympathetic nerve blocks at the ganglion Impar, especially given the close proximity to the bacteria-laden rectum. Nerve ablation in the coccyx region may be beneficial for selected patients with coccydynia (207). Most patients with tailbone pain will obtain adequate relief via nonsurgical treatments such as injections, thus often avoiding the need for surgery and its potential complications (209).

Refferences

Source:  Physical Medicine and Rehabilitation - Principles and Practice

Although still controversial, discography (diagnostic intervertebral disc injection) is both an imaging study and a provocative physiologic study for determining whether an intervertebral disc is in fact a pain generator in a given patient (Table 68-7). Inserting a spinal needle into the center of the intervertebral disc and injecting contrast dye provides both physiologic information on whether a degenerative disc is painful and on anatomic features of the intervertebral disc. There is currently no other method to establish reliably whether a disc is a patient’s pain generator.

Clinical Presentation of Discogenic Pain

Patients with lumbar discogenic pain typically have low back pain but can also have pain referred to the buttock, hip, groin, thigh, or distal lower limb. (175). Discogenic pain is typically worse with lumbar flexion and unsupported sitting, as intradiscal pressures have been found to be higher in these positions (176). Physical examination should reveal a normal neurologic examination if the discogenic pathology does not affect the nerve roots.

Radiographic Correlation

MRI and CT of the lumbar spine can be useful initial assessment tools because they are noninvasive tests that allow for visualization of multiple discs. Although they have high sensitivity (Figs. 68-18 and 68-19) for detecting anatomic disc abnormalities, surgically proven internal disc disruption has been reported in cases of normal-appearing MRIs (177). MRI carries a high rate of false-positive findings, as shown in studies of asymptomatic patients (178). In addition, they cannot provide the physiologic information about whether an abnormal- appearing disc is actually a pain generator. Although highintensity signal zones (HIZ) in the posterior annulus on MRI have been linked to discogenic pain (Fig. 68-19), the HIZ can also occur in asymptomatic patients (179–182). With no pathognomonic features of discogenic pain and a high falsepositive rate of anatomic findings on noninvasive diagnostic tests, the diagnosis of symptomatic lumbar disc diseases requires a physiologic study for better clinical correlation of a patient’s pain with CT or MRI abnormalities. Provocation discography is a physiologic test for discogenic pain.

Anatomy and Pathophysiology of Discogenic Pain

The intervertebral disc is a well-innervated structure with A-delta and C-pain fibers (183) containing nociceptive substances such as substance P, calcitonin gene-related product, VIPs in the annulus fibrosis (184–186). Nerve growth factor has been found in both the annulus fibrosis and nucleus pulposus, which may increase pain sensitization (187). In healthy intervertebral discs, only the outer one third of the annulus fibrosis is innervated. Study of intraoperative samples from degenerative intervertebral discs of patients with chronic back pain demonstrated evidence of inward growth of nerve fibers along the radial fissures into the inner annulus (185,186). The presence of the neural structures and nociceptive fibers is believed to be the anatomic basis of chronic low back pain due to degenerative disc diseases. Discogenic pain may occur in internal disc disruption, which is a condition characterized by a degraded nucleus pulposus with radial fissures extending into the peripheral annulus fibrosis (Fig. 68-19) (188,189). The outer margin of the annulus is intact. The nucleus pulposus, reaching the innervated outer annulus through the annular fissures, invokes an intensive local inflammatory process. These inflammatory substances irritate and sensitize the nociceptive fibers in the outer annulus. The threshold for nociceptive mechanical stimulation is lowered in these chemically sensitized nociceptors. Chronic discogenic pain may result from mechanical stimulation of sensitized nociceptors with normal lumbar disc loading. In fact, intraoperative mechanical stimulation of the posterior annulus in the presumed painful segment induced low back pain in one study (190). Degenerative disc disease is believed to account for some 40% of patients with chronic low back pain of unclear origin (191).

FIGURE 68-18. Lateral plain film nucleography demonstrating a posterior annular fissure in the L4-5 and L-S1 discs, respectively, through which contrast leaked into the ventral epidural space. Compare this image with that in Figure 68-23. The nucleography of the L3-4 discs was normal. The patient had concordant back pain at the L4-5 and L5-1 discs but no pain at the L3-4 discs.

FIGURE 68-19. T2-weighted sagittal images of lumbar spine. MRI demonstrating degenerative disc disease, especially at L5-S1.

Indications

Indications for discography appear in the “Position Statement on Discography” from 1988 and 1996 by the Executive

Committee of the North American Spine Society (192):

  • Patients with unremitting spinal pain of greater than 4 months and unresponsive to all appropriate methods of conservative therapy
  • Patients in whom other investigations have failed to explain the source of pain
  • Chronic back pain patients who are contemplating intradiscal or surgical procedures such as spinal fusion

Technique

Discography is generally performed in a radiologic suite or an operating room. The patient is placed in either a prone or oblique side-lying position. A pillow is placed under the patient’s abdomen to reverse lumbar lordosis. The lumbosacral area is prepared and draped in a sterile fashion. The patient’s vital signs should be monitored and oxygen saturation recorded with a pulse oximeter. A peripheral intravenous line should be established for light conscious sedation.

An AP fluoroscopic view is then used to identify the appropriate disc level. The fluoroscope is tilted in either a cephalad or caudad direction to best visualize the target disc space on radiograph. The C-arm is then rotated ipsilaterally to place the superior articular process of the subjacent vertebral body in a position that bisects the vertebral body above. An appropriate size spinal needle, typically a 25-gauge, 3.5-in. spinal needle is used to infiltrate the skin and subcutaneous tissue down to the superior articular process with 1% lidocaine. Caution should be exercised not to inject local anesthetic overzealously in the superior articular process area in order to avoid potential spread to the epidural or nerve root areas, thus compromising the patient’s ability to perceive pain during the subsequent provocative discography. To reduce the chance of discitis, a two-needle technique with 18- or 20-gauge, 3.5-in. introducers and 22- or 25-gauge, 6-in. inner needles, is recommended.

The introducer needle is inserted and directed to the outer edge of the superior articular process in the AP view and just to the anterior border of the superior articular process in the lateral view. The inner needle is then inserted through the introducer and slowly advanced to the center of the nucleus pulposus using alternating AP and lateral views. If the patient complains of radicular pain or paresthesias in a nerve root distribution during needle advancement, the needle should be withdrawn and redirected. If a pressure-controlled system is used for the injection, the needle is connected to an injection system with a manometer that is filled with nonionic and water-soluble contrast. The injectionist then injects contrast slowly, monitoring the pressure reading and the patient’s reports of pain simultaneously. The opening pressure is the pressure reading at the first appearance of dye in the disc on fluoroscopy. The endpoint of the injection occurs when the patient reports concordant pain (defined as reproduction of pain in the same location and intensity), or when 2 mL of total volume is injected into the disc or the pressure reading reaches 90 lb per square inch (psi). To help minimize the chance of discitis, 5 to 10 mg of cefazolin can be injected into each disc before needle removal. One level above and below the disc with concordant pain should be also studied so as to serve as a control (Figs. 68-20 to 68-22).

Information obtained from discography includes the volume of contrast injected, the patient’s pain response (no pain, dissimilar or discordant pain, similar pain, and exact pain provocation or concordant pain), degree of resistance to injection, morphology of the nucleogram, and postdiscogram CT morphology of the disc (193).

FIGURE 68-20. Sagittal T2-weighted lumbar spine MRI demonstrating degenerative disc disease at L5-S1 and possible degenerative disc disease at L4-5 and L3-4.

FIGURE 68-21. Lateral view of lumbar discograms reveals a posterior annular fissure at L4-5 and L5-S1 discs. The discography reproduced the patient’s clinical symptoms (concordant) at L4-5 and L5-S1 discs but no pain at L3-4 discs.

FIGURE 68-22. AP view of lumbar discograms demonstrated left side posterior annular fissures.

Postinjection CT scanning provides an axial view of the injected discs (Fig. 68-23). Patterns of radial and concentric annular fissures are more clearly defined in this plane. Postdiscography CT scanning should be performed within 2 hours of the discogram to prevent diffusion of dye out of the nucleus. The Dallas Discogram Description, in addition to recording the pain and contrast volume injected, describes morphologic degrees of annular degeneration and disruption (194). Annular degeneration and disruption are graded by the percentage of the contrast injected that fills the annulus and annular fissures toward the outer annulus as revealed by the contrast (Table 68-8) (195). A study by Derby et al. found that there was a significant correlation between the extent of annular disruption on CT and the rate of symptomatic disc on discography, with significant differences between grade 3 and 5 versus grade 0 and 2 (196).

FIGURE 68-23. Lumbar postdiscography CT image demonstrating the track of contrast that leaked through a radial fissure into a circumferential outer annular fissure.

A positive discogram requires a concordant pain response, an abnormal nucleogram, and a normal control level. In contrast, multilevel painful discs without a normal control disc on injection are unexplainable and cannot be regarded as positive.

Validity of Discography

In a prospective and controlled study in 1990, by applying modern manometry and postdiscography CT technology, refined needle placement techniques, less irritating contrast dye, stressing concordant pain, or discordant pain in addition to disc morphology (195), Walsh concluded that using stringent criteria, the false-positive rate of lumbar discography in asymptomatic individuals is 0% and the true-positive rate in symptomatic patients is 89% (189). However, Walsh’s study is limited by its small sample size (i.e., only ten controls and seven patients).

In a retrospective study, Derby et al. reported that a patient with a chemically sensitive disc, defined as one having a concordant pain response provoked with intradisc pressure of less than 15 psi as measured by a manometer, has a better outcome with interbody fusion versus intertransverse fusion surgery (197). This better surgical outcome presumably resulted from the removal of the mechanical load or stimulation to the chemically sensitive disc through removal of the painful intervertebral discs and stabilization with interbody fusion (197). Nevertheless, these investigators pointed out that discography should never stand alone as a diagnostic tool and sole factor for a clinical decision. The presence of a chemically sensitive disc does not rule out other coexisting sources of pain, nor does it exclude patients with excessive pain magnification. Discography should be used in conjunction with other diagnostic tests, such as MRI and CT scans, as well as the patient’s history, physical examination findings, response to a comprehensive therapeutic program, and psychometric profile information. Therefore, careful candidate selection is the key to maximizing clinically valuable data from discography. A recent study by Carragee et al. in 2000, although controversial, revealed a high false-positive rate with lumbar discography in a mixed population of 26 asymptomatic patients (182). A significant positive pain response and pain-related behavior with discography were found in 10% of the pain-free group and in 83% of the somatization disorder group. Discs with annular disruption were more likely to be painful on injection. The study concluded that if strict criteria are applied, the rate of false-positive discography may be low in subjects with normal psychometric profiles. Schwarzer et al. in 1995 (183) reported that a discogram is likely to provide highly specific information on the painful lumbar disc when the following characteristics are present: (a) unremitting low back pain persisting after 6 months of conservative care; (b) no prominent psychological dysfunction; (c) injection of all degenerated discs and one normal disc by MRI; or (d) combination of the results of appropriately and carefully performed provocative and imaging tests.

Complications of Discography

Potential complications of discography include discitis (0.05% to 4%), nerve root injury, subarachnoid puncture, chemical meningitis, bleeding, and allergic reaction (192). Use of sterile technique, a two-needle technique, as well as intradiscal antibiotics, can reduce the risk for infection (198).

Summary

In addition to providing imaging of disc morphology, discography is the only provocative physiologic test that can provide information on whether a degenerative disc is the source of pain. In appropriately selected patients, discography is a safe, reproducible, objective diagnostic tool when testing includes volume, pressure, fluoroscopic abnormalities, and pain provocation. Discography results help guide surgical management of chronic back pain. A negative discogram or a multilevel positive discogram without a painless control level can help to exclude a patient as a surgical candidate. Conversely, a singleor double-level positive discogram, along with other clinical data, can help to guide operative planning with respect to fusion or other surgical procedures. This potentially optimizes surgical outcomes. Whether diagnostic discography will actually change surgical outcome depends on many factors, such as a patient’s psychosocial factors, job situation, and the surgical technique employed. The true value of diagnostic discography will likely remain controversial until a prospective, randomized, double-blind, and controlled clinical trial on the outcomes of surgery based on discography is carried out.

Refferences

Source:  Physical Medicine and Rehabilitation - Principles and Practice

Radiofrequency neurotomy interrupts the nociceptive afferent from the Z-joint by thermally coagulating the two medial branches that innervate a given Z-joint. The exposed terminal portion of radiofrequency probe delivers heat at 80°C. For each Z-joint (except the C2-3 joint, which is innervated by the third occipital nerve), two medial branches need to be ablated.

Indications

Radiofrequency neurotomy can provide relative long-term benefit symptoms from persistent or recurrent Z-joint pain despite conservative care (that have had transient benefit from Z-joint injections), and for patients with substantial (e.g., at least 80%) pain relief after dual blocks of the medial branch with two local anesthetics of different duration on two occasions.

Technique

Lumbar Medial Branch Neurotomy

Since the “groove” at the junction of the superior articular process and the transverse process can be clearly viewed in a certain fluoroscopic position, this “groove view” has been proposed for the starting position of a lumbar medial branch neurotomy. Specifically, the C-arm intensifier is obliqued ipsilaterally approximately 10 to 15 degrees and tilted cephalad 20 degrees. A 22-gauge 100 mm radiofrequency probe with a 5-mm active tip is then introduced using the “tunnel view” until it contacts the bone and advanced along the “groove” where the medial branch resides. The radiofrequency probe creates an effective circumferential lesion around the probe but does so poorly distal to the tip. To avoid incomplete heating, the radiofrequency probe needs to be placed on and parallel to the path of the medial branches crossing the transverse processes. In AP imaging, the needle should be medial to the lateral silhouette of the superior articular process. A lateral view should be obtained to ensure that the needle is not positioned anterior to the posterior aspect of the neuroforamen. Motor stimulation using 2.0 Hz and less than 2.0 V should not induce any muscle twitching or movement in the lower extremity. A single lesion at 80 degrees celsius for 60 seconds is performed. A second and third lesion is performed after repositioning the needle 1.0 mL cephalad and caudad to ensure proper coagulation of the length of the medial branch.

Cervical Medial Branch Neurotomy

For cervical medial branch ablation, the patient is placed in a prone position and the C-arm is tilted in a cephalad direction to obtain a pillar view. The first radiofrequency lesioning probe is inserted parallel to the articular pillar, directed down the fluoroscopic beam and slightly medial until it touches the dorsal aspect of the pillar. The needle is then walked lateral until it slips off the bone. A second radiofrequency probe is inserted with approximately 30 degrees of ipsilateral obliquity and slightly caudad so that this needle can be positioned more anteriorly. The rest of the needle advancement is the same as for the first needle. This dual needle placement positions the two probes to allow subsequent adequate denervation along the entire length of the medial branch. Prior to lesioning, a lateral view is taken to ensure that the tips of the radiofrequency probes are not anterior to the anterior margin of the articular pillars. Motor stimulation is conducted at a frequency of 2.0 Hz and at less than 2.0 V intensity. If muscle twitching or upper extremity movement occurs, this indicates that the radiofrequency probe is too close to the anterior rami and needs to be repositioned. Next, 0.5 mL of 1% lidocaine is injected through the radiofrequency cannula. A lesion is then performed at this position at 80°C for 60 seconds. The probe is then repositioned 1 mm caudad and cephalad, respectively, and two additional lesions are made for a total of six lesions using the two radiofrequency probes. A similar technique is employed for the third occipital nerve.

Efficacy

Proper patient selection is the key for optimal outcome from radiofrequency neurotomy. One recent prospective study has demonstrated good efficacy from the procedures when patients with presumed Z-joint pain are selected using the double block paradigm with comparative local anesthetic (130). The patients were diagnosed with a lumbar Z-joint pain if they obtained at least 80% pain reduction after medial branch blocks with 0.5 mL of 2% lidocaine on one occasion and 0.5% bupivicaine on another. At 12 months following the radiofrequency medial branch neurotomy, 60% of patients achieved at least 90% pain reduction and 87% of patients had 60% pain relief. The success of denervation was seen in virtually all patients as demonstrated by post-radiofrequency needle EMG of the corresponding segmental multifidi (130). The initial population of 41 patients accepted into the study and clinically felt to have facet-mediated pain was reduced to only 15 candidates for actual RFA, which further emphasizes the importance of double-block screening for Z-joint pain diagnosis. A recent randomized study using single Z-joint blocks for selecting patients with subsequent radiofrequency neurotomy demonstrated modest success with an average VAS pain reduction of 2.0 points in 66.7% of the lesion group versus 35.7% of sham group patients at 8 weeks to 12 months follow-up (131). An obvious concern with this study is that the criteria for a positive block mandated a relatively low threshold of only 50% pain relief, and 40 of 92 patients subjected to the diagnostic block had a positive response in this regard. This would imply a prevalence of facet joint pain higher than what has been reported in most populations. Another study showed no treatment effect at 12 weeks, as assessed by the Roland-Morris scale (2.6% change) and Oswestry scale (1.9% change) and VAS (–7.6% change) (132). Again, the known 38% false-positive rate for a single-block makes the study results and conclusions less convincing (126,133).

Efficacy of radiofrequency neurotomy for cervical Z-joint pain (other than from the C2-3 joint that was excluded from this study), has also been demonstrated in a randomized, double-blinded, and placebo-controlled trial (134,135). The patients were selected by placebo-controlled medial branch blocks. The total duration of pain relief was defined as the period until the patient judged that pain had returned to 50% of the pre-procedural level. Twenty-four patients were randomized into radiofrequency neurotomy and sham radiofrequency neurotomy (radiofrequency probes placed but radiofrequency was not turned on) groups. Fifty percent pain relief lasted 263 days in the radiofrequency group and 8 days in a controlled group. A second study of 28 patients with long-term follow-up and repeat radiofrequency neurotomy demonstrated a median duration of pain relief of 422 days. In the 11 patients who underwent repeat radiofrequency neurotomy, the median duration of pain relief was 219 days. The authors concluded that radiofrequency neurotomy provides clinically significant pain relief, and can be repeated if pain recurs (136).

Recent review articles on randomized controlled trials of radiofrequency neurotomy for spinal pain concluded that RF neurotomy was efficacious for both chronic low back pain and neck pain after flexion-extension injuries (124), and that there is evidence of moderate strength for use of RFA in the cervical and lumbar spine (129).

Complications

Potential complications of fluoroscopic-guided, contrastenhanced lumbar Z-joint injections or medial branch blocks are rare. The most common post-procedural problem is transient pain at the injection site. However, there have been rare case reports of meningitis, inadvertent spinal anesthesia, and infection after Z-joint injections (137,138). Recurrent back and neck pain after radiofrequency neurotomy may be due to incomplete ablation or medial branch regeneration (139). Since the dorsal root ganglia are left intact, the ablated medial branches may regenerate. Because radio frequency neurotomy does not permanently denervate the Z-joints or cause inherent instability in the spine, the concern of Charcot facet joint development has little ground and no such cases have been published (140). Also, because the DRG remains intact, deafferentation pain should not occur. Side effects from radiofrequency neurotomy are rare when the procedure is performed correctly but include local pain and infection.

Refferences

Source:  Physical Medicine and Rehabilitation - Principles and Practice

The sacroiliac (SI) joint can be a significant source of low back pain (141–143). Etiologies of SI pain include spondylo arthropathy, crystal arthropathy, septic arthritis, trauma, and pregnancy diasthesis (144). In addition, SI joint dysfunction (pain from a biomechanical disorder without a demonstrable lesion) has been proposed as a possible etiology of SI pain (145). Among patients with chronic low back pain, a study using a single block technique of the SI joint with a local anesthetic, estimated the prevalence of SI joint pain as between 13% and 30% (141). A study on 54 patients with unilateral low back pain suspected from the SI joint, using a dual local anesthetic block technique, demonstrated an 18.5% prevalence of SI joint-based pain (142).

Anatomy and Pathophysiology

The SI joint is a true diarthrodial joint and is innervated by nerves from the L4 through S2 levels (146). Studies on human and animal SI joint capsules demonstrated the presence of mechanoreceptors and nociceptors (147,148). The SI joint has a close anatomic relationship to the lumbosacral plexus and the L5 and S2 nerve roots. Therefore, SI joint pathology such as inflammation or chronic synovial irritation from joint dysfunction can not only serve as a pain generator, but also can potentially involve the nearby neural tissues and induce pain. Injection of the joint with contrast material in healthy volunteers produced pain that extended approximately 10 cm caudally and 3 cm laterally from the posterior superior iliac spine in a linear strip (146). Patients with pain diagrams similar to the SI joint pain mapping were confirmed as having SI pain with SI joint provocation injection (149).

Diagnosis of the SI Joint Pain

The value of clinical data from history and physical examination in the diagnosis of SI joint pain remains controversial (141–143,150,151). Although SI joint pain frequently manifests as pain in the sacral sulcus areas, SI joint pain can refer to the buttock, lower lumbar region, groin, and lower limb (152). However, none of these symptoms, signs or various provocative tests are pathognomonic for SI joint pain. Other sources of low back pain, such as lower lumbar Z-joint arthropathy or degenerative disc disease, can present similarly. By using fluoroscopically guided SI joint blocks to confirm cases of SI joint pain (Fig. 68-17), several authors have shown that clinical medical history and pain provocation tests are not reliable in the diagnosis of SI joint pain (141–143,150,151).

FIGURE 68-17. AP view of right SI joint arthrogram demonstrating contrast in the posterior (medial) and anterior (lateral) joint space. This 23-year-old man complained of persistent right-sided low back pain after a front-impact motor vehicle collision. He was forcefully pressing his right foot on the brake during the collision, with resultant right SI pain. Injecting the right SI joint with 1 mL of 2% lidocaine relieved 90% of his low back pain, lasting several hours. SI joint injections can have both diagnostic and therapeutic benefits.

In a clinical trial involving 84 patients with possible low back pain from the SI joint, Dreyfuss et al. studied clinical history and the 12 physical examination tests deemed most reliable by a panel of experts for isolating SI joint pain (143). Fluoroscopically guided intra-articular SI joint injections of local anesthetic and corticosteroid were performed to confirm the diagnosis. The criterion for a positive result was the achievement of at least 90% pain relief postinjection. The study demonstrated that neither the history nor the physical examination data was of significant value in diagnosing SI joint pain (141). Maigne et al. investigated 54 patients with clinical features of chronic low back pain compatible with the origin in the SI joint with the following features: unilateral buttock pain, tenderness over the SI joint, normal lumbar CT scan, failure of previous epidural, or facet injections (142). They applied seven “SI pain provocation tests” before and after the dual block of SI joint. To be considered diagnostic, patients had to report 100% pain relief after block with 1% lidocaine and at least 75% pain relief after block with 0.25% marcaine. There was an 18.5% rate of positive responders to this dual block. The result demonstrated that none of the SI joint pain provocation tests were able to isolate SI joint pain (142). Slipman et al. performed a diagnostic fluoroscopically guided SI joint injection in 50 consecutive patients with low back pain presumed to be from SI joint (162). A reduction of the VAS rating by at least 80% was considered a positive response to SI joint block. The authors concluded that the various SI joint provocative maneuvers were not useful in diagnosing SI joint pain (162). A diagnostic imaging study done with bone scan was found to have low sensitivity and high specificity for diagnosing the SI joint syndrome (149). This study excluded patients with SI joint pain from inflammation, such as in a seronegative spondyloarthropathy. However, another study using single photon emission CT (SPECT) was performed in 54 patients with symptoms of low back pain of at least 3 months duration, the presence of higher erythrocyte sedimentation rate, and higher C-reactive protein levels who had not received anti-inflammatory drugs. The results demonstrated high sensitivity (97%) and specificity (90%) in diagnosing inflammatory disease within SI joints (153).

Indications

Although exact guidelines for administering an SI joint injection are unclear, one set of guidelines is as follows: a diagnostic SI joint injection is indicated in patients with pain over the sacral sulcus who have failed to respond to 4 to 6 weeks of directed physical therapy and oral nonsteroidal anti-inflammatory agents (154,155).

Technique

The patient is placed in a prone position. The skin over the sacral area is prepped and draped in a sterile manner. By rotating the C-arm fluoroscope slightly contralaterally, but occasionally ipsilaterally, intermittent fluoroscopy is used to identify the medial joint line when it just separates from the lateral joint line of the SI joint. Some adjustment of the C-arm in the caudal or cephalad plane may then be used to best isolate and visualize the lower portion of the SI joint. The targeted area is the small lucent area just below the joint line. The skin entry site is selected slightly lower than the targeted area, and is infiltrated with a small amount of 1% lidocaine. A 22- or 25-gauge 2.5 to 3.5-in. spinal needle is inserted and directed down to contact the ilium. The needle is then withdrawn 2 to 3 mL and redirected toward the inferior-medial aspect of the joint into the lucent area (156). Typically, the needle tip will bend if it enters the SI joint, and a tactile sense of a sliding into the joint will be appreciated (157). Applying a slight curve at the tip of the needle prior to use may help assist this process (156). A small amount of contrast is then injected to outline the SI joint. If the needle fails to plunge and no contrast flow is seen on fluoroscopy, one technique advocates that the needle be slowly extracted a millimeter at a time, while continuing to maintain pressure on the plunger until there is a loss of resistance (157). Once an SI joint arthrogram without a vascular uptake pattern is demonstrated, anesthetic with or without steroid is injected (depending upon if the injection intent is for therapeutic or diagnostic use, respectively). One milliliter of 2% lidocaine or 0.5% bupivacaine mixed with 40 mg/mL of triamcinolone acetonide, or other equivalent corticosteroid, is injected into the SI joint (158–161). A total of no more than 2.0 mL of volume is generally injected due to the limited volume of the SI joint (160).

Efficacy

Diagnostic Injection of SI Joints

Because the gold standard for proof of SI joint pain is unclear, the sensitivity and specificity of diagnostic SI joint injections has not been clearly established.

Maigne et al. (142) have suggested that the SI joint block has diagnostic value only for pain from intra-articular sources, not for SI joint pain from extra-articular sources such as the periosteum, interosseous ligaments, erector spinae muscles, or fascial elements, all of which contain nociceptors and hence are possible pain generators (147,148). Therefore, an SI joint block procedure that involves injection of an agent into the extra-articular components rather than the joint cavity may show better correspondence to the clinical features. Future studies should address whether the combination of pericapsular and intra-articular SI joint injection with corticosteroid can improve outcomes.

Therapeutic Injection of the SI Joint

The efficacy of SI joint corticosteroid injections has been reported in prospective and retrospective studies of patients with spondyloarthropathy (163,164). In a retrospective study, Slipman et al. reported a significant benefit from SI joint steroid injection in patients with SI joint syndrome (165). Thirty-one patients with chronic SI joint syndrome received an average of 2.1 fluoroscopic-guided SI joint corticosteroid injections. The average follow-up was 94.4 weeks. Of the 29 patients who completed the study, there was a significant improvement in the Oswestry disability score, VAS, and work status (165). Although these retrospective results are encouraging, there are currently no prospective studies on the efficacy of fluoroscopically guided therapeutic SI joint corticosteroid injections.

Radiofrequency Ablation of the SI Joint

Radiofrequency ablation (RF-A) has recently been proposed as a potential long lasting treatment for SI joint pain, and has been gaining more popularity along with other nonsurgical spinal procedures. RF-A involves de-innervation of the SI joint nerves believed to be responsible for generating pain (166,167). It is indicated as a treatment for those patients who have failed more conservative measures, yet only received transient benefit from diagnostic and/or therapeutic injections of the SI joint (168). The true effectiveness of RF-A of the SI joint is unclear, as of yet (169). In contrast to RF-A in treating lumbar spine facet-mediated pain, which directly targets the medial branches of the dorsal rami, which innervate the facet joints (170), the SI joint has complex innervations (171). Therefore, no consistent procedural technique has been described in the literature. Multiple studies have, in fact, been done using various techniques for RF-A of the SI joint, which are summarized in Table 68-6. The table shows that there are variations among the techniques used in regard to structures, nerves, and patterns of ablation to the SI joint.

The table underscores the fact that there is no standard pattern of ablation and not enough available prospective data to determine which rami or branches should be ablated, or if a pattern technique (i.e., “leap frog” vs. “strip lesion”) is more efficacious. The studies do not show uniformity and additional studies to determine if RF-A is useful for treating chronic SI joint pain are warranted.

Refferences

Source:  Physical Medicine and Rehabilitation - Principles and Practice

Introduction

The prevalence of lumbar zygapophyseal joint (Z-joint) pain has been reported to be approximately 6% in a primary care setting (94). However, in a tertiary spine center, lumbar Z-joint pain has been reported to range from 15% in younger individuals (96) to 40% in older populations (98) with chronic low back pain. In individuals with chronic neck pain after a whiplash injury, Z-joint pain occurred in approximately 50% of patients (99,100). More recent literature examining 500 patients has reported a prevalence of 55% cervical facet joint pain, 42% thoracic facet joint pain, and 31% lumbar Z-joint pain in patients with chronic spine pain identified with a double block model as described later (95). Lumbar facet joint pain has been reported in 16% of patients with chronic postsurgical lumbar spine pain (97). Studies of a larger population using a dual anesthetic block paradigm may be helpful in further identifying the prevalence in the general population for both acute and chronic low back pain.

Anatomy

Z-joints are pairs of small synovial joints in the posterior aspect of the spine, formed when the inferior articular process of one vertebra articulates with the superior articular process of the subjacent vertebra. Each lumbar Z-joint has a 1 to 2 mL capacity (101). Cervical and thoracic Z-joints can hold volumes of less than 1 mL (103) and 0.5 to 0.6 mL (104,105), respectively.

The Z-joint at C2-3 is innervated by the third occipital nerve from the superficial medial branch of the C3 dorsal ramus. Below the C2-3 Z-joint, each cervical Z-joint is innervated by the medial branches from the level above and below. The medial branches wrap around the articular pillar transverse processes. The C7 medial branch is located higher, as it is pushed up by the base of the transverse process. The joints between C0-1 (atlanto-occipital) and C1-2 (atlantoaxial) joints are technically not Z-joints, due to their anterior location. They are innervated by the anterior rami of C1 and C2, respectively. Significant variability in the location of the medial branches has been reported, particularly with regard to the anatomy in the cervical spine (102).

The medial branches innervating the thoracic Z-joints have a different course in relation to the transverse processes (105). The thoracic medial branches instead wrap around the junction between the transverse process and the superior articular process. As in the lumbar spine, they often exit in the middle portion of the intertransverse space, and they typically cross the superolateral corners of the transverse processes and then pass medially and inferiorly across the posterior surfaces of the transverse processes. Furthermore, at mid-thoracic levels (T5-8), the inflection occurs at a point superior to the superolateral corner of the transverse process. Therefore, the superolateral corners of the transverse processes are generally the more accurate target points for diagnostic blockade or radiofrequency denervation of the thoracic medial branches.

In the lumbar spine, each Z-joint is innervated by two medial branches of dorsal rami; one from the same level and the other from the level above (106). For example, the Z-joint at L4-5 is innervated by the medial braches of the L4 and L3 dorsal rami. The medial branches travel along the junction of transverse process and superior articular process. After exiting the mamilloaccessory notch covered by the mamilloaccessory ligament, the medial branches send branches to innervate the same level of the Z-joint and the Z-joint below. However, the L5 dorsal ramus crosses the groove between the sacral ala and the superior articular process of the sacrum. The L5 medial branch to the L5-S1 Z-joint is very short because it does not branch out until it comes just under the L5-S1 Z-joint. It is important to remember that the lumbar medial branch rests on the subjacent level rather than the same level of the transverse process. For example, the L3 medial branch rests on the L4 transverse process rather than on the L3 transverse process (Figs. 68-12 and 68-13). Therefore, to denervate the L4-5 Z-joint, it is necessary to target the L3 and L4 medial branches, which rest on the junction of L4 and L5 transverse processes and superior articular processes, respectively. One exception is the blockade or denervation of the L5 medial branch. Due to the short branch below the Z-joint, denervation of the L5 medial branch can only be performed by destruction of the L5 dorsal ramus proper at the groove between the sacral ala and the superior articular process.

FIGURE 68-12. AP view of left L5-S1 Z-joint (facet) arthrogram. Notice the contrast pooling in the superior and inferior articular recesses. This 33-year-old man injured his low back lifting a 70-lb piece of metal overhead. Unable to sustain the weight, he extended his low back obliquely to the right side to drop the metal. He felt a “pop” in his left low back and sustained persistent significant left low back pain. Several minutes after this left L5-S1 intra-articular Z-joint injection with 0.5 mL of 1% lidocaine, his low back pain was completely abolished.

FIGURE 68-13. AP lumbar MBB at the right L2, L3 and L4 vertebral levels, demonstrating needle tips and contrast injected at the base of SAPs and the transverse processes.

Pathophysiology of Z-joint Pain

The Z-joint is a well-innervated structure. The Z-joint capsule contains both nociceptive and mechanosensitive receptors (101,106–108). Immunocytochemical studies have demonstrated that the Z-joint capsule or synovial folds contain substance P, calcitonin gene-related product, vasoactive intestinal polypeptide (VIP) and neuropeptide, and tyrosine hydroxylase (101,107,108). Ostensibly, the Z-joint capsule is a potential pain generator if it is injured. In addition, like any synovial joints, Z-joints can develop synovitis under certain circumstances.

Typical Z-joint pathology often derives from pathologic mechanical stress or inflammation. In the lumbar spine, the sagittal orientation of upper lumbar Z-joints and the relative lateral oblique orientation of lower lumbar Z-joints make them vulnerable to injury from extension and torsion forces. In the cervical spine, both human and animal studies of whiplash injuries have demonstrated evidence of multiple pathologic findings, including Z-joint capsule tearing, intraarticular hemorrhage, articular cartilage, muscle injury, and subchondral bone fracture (110). These pathologic changes can serve as a basis of pathologic nociception and neck pain. However, none of these pathologies can be detected with conventional imaging studies (110).

Patients with lumbar Z-joint pain often have more pain in the lateral aspect of the low back unilaterally or bilaterally but not centrally (111). Pain can often be made worse with oblique extension of the lumbar spine (111,112). Pain is often worse after overnight rest or inactivity. Local tenderness and “muscle spasm” over the involved Z-joint are frequently noted. Although Z-joint pain can present with referred pain, groin pain or thigh pain, neural tension signs are negative and there are generally no neurological deficits, though recently a study where a rat model was used to induce Z-joint inflammation has documented associated radiculopathy as a possible sequela (109). Patients with cervical Z-joint pain experience pain located in the axial cervical areas. However, several studies have failed to demonstrate any pathognomonic physical exam findings of Z-joint pain (111,112). Imaging studies are also unable to confirm or refute the diagnosis of Z-joint pain (110,113,114).

Indications

Given the lack of a clinical diagnostic gold standard, clinicians have used regional anesthesia to identify Z-joint pain. Abolishment of low back pain after anesthetic Z-joint injection or medial branch block confirms the Z-joint as the pain generator (Figs. 68-14 and 68-15). Z-joint injection is indicated in patients with acute back and neck pain of suspected Z-joint origin, with no evidence of neurologic deficits, and whose pain pattern resembles that evoked in normal volunteers upon stimulation of their Z-joints. However, since the majority of acute back and neck pain, including Z-joint pain, will resolve in several weeks, the injection is often reserved for individuals with severe pain that has failed to respond to 4 to 6 weeks of conservative therapy including oral analgesics, directed physical therapy, and relative rest. Fortunately, injection can be performed earlier if pain is inhibiting therapy progress.

FIGURE 68-14. Oblique view of left L4-5 Z-joint injection showing the needle tip inside the Z-joint space.

FIGURE 68-15. Oblique view demonstrating blocks of right L1, L2 and L3 medial branches at the right L2, L3 and L4 pedicles, viewed as the “eyes of the Scotties dogs”, at the base of the SAPs and transverse process where the medial branches are located.

Contraindications

As is true of all spinal injection procedures, Z-joint injections are contraindicated in individuals with the following conditions: infection, bleeding diathesis, pregnancy (for use of fluoroscopy), allergy to the medications to be injected (contrast medium, local anesthetics, corticosteroid), and unstable medical conditions such as unstable angina or poorly controlled hypertension or diabetes mellitus. Injections are elective procedures, so an effort should be made to properly select patients so as to ensure safety and optimize outcome.

Techniques

For lumbar Z-joint injection, the patient is placed in a prone position with a pillow under the abdomen to distract the Z-joint. After sterile preparation and skin draping, intermittent fluoroscopic views are used to identify the level of the Z-joint. For the L5-S1 level, the fluoroscope is tilted in a caudad direction to accommodate the lumbar lordosis, and rotated ipsilaterally until the joint space first comes into view, which is the posterior opening of the Z-joint, that is, the needle entry point. Although further rotating the image intensifier will more clearly visualize the Z-joint space, the visualized joint space at this angle is actually the middle or anterior Z-joint opening, not the posterior opening which is the injectionist’s target. For upper lumbar Z-joint injections, it may require less oblique rotation to better visualize the Z-joint space. The needle entry site is marked with a metal instrument. The skin and the underlying tissues are infiltrated with 1% lidocaine. For diagnostic Z-joint injections, the underlying tissues should not be infiltrated with anesthetic in order to maximize injection specificity. A 22- or 25-gauge 3.5 in. spinal needle is then inserted at the anesthetized site and directed toward either the superior or inferior articular processes of the targeted facet joint using a “tunnel view” technique by which the entire needle shaft is paralleled to the fluoroscopy beam in such a way that the needle hub appears as a dot. Once the needle contacts the bone, the tip of the needle is then “walked” off into the Z-joint space. Occasionally, due to the osteoarthritic changes, the needle cannot gain entry. The needle can then be directed into the inferior articular recess just off the lower margin of the articular processes. Once the needle is felt to be in the articular space or to have penetrated the Z-joint capsule, 0.2 to 0.3 mL of the water soluble and nonionic contrast is injected to outline the Z-joint and to confirm that the needle tip is not located inside the vascular or epidural space. For therapeutic benefit, 1.0 mL of a mixed solution containing 20 mg of methylprednisolone acetate and 1% lidocaine is slowly injected into the Z-joint.

Medial Branch Block

For lumbar medial branch blocks, skin preparation and C-arm fluoroscope positioning are essentially the same as for Z-joint injections. The difference is the target, which is the “Scottie dog’s eye” rather than “ear,” because the former represents the anatomical site where the medial branch is situated whereas the latter represents the articular processes forming the Z-joint. After local skin is infiltrated with 1% lidocaine, a 22- or 25-gauge 3.5 in. needle is inserted and directed until the needle touches the middle portion of the “Scottie dog’s eye.” The fluoroscope is then turned to the cross table or lateral view; the needle should be located at the site posterior to the spinal lamina. At the anterioposterior (AP) view, the needle tip should be at or slightly medial to the lateral margin of the superior articular process. At this point, the needle bevel should be turned to face medially, and 0.2 to 0.3 mL of the contrast is injected under real-time fluoroscopy to ensure that a vascular pattern or neuroforamial spread upon the dye injection has occurred. To ensure block specificity, less than 0.5 mL of either 2% lidocaine or 0.5% bupivacaine is used to block each medial branch.

For block of the L5 dorsal ramus, the fluoroscope should be rotated ipsilaterally oblique about 10 to 15 degrees. The needle is then directed in “tunnel view” down to the junction at the superior articular process of the S1 vertebra and the ala of the sacrum. In the AP view, the needle tip should be at the lateral margin of the S1 superior articular process.

Efficacy

Diagnostic Z-joint Injection or Medial Branch Block

The literature has demonstrated that Z-joint injections and medial branch blocks can be used for the diagnosis of Z-joint pain with comparable sensitivity and specificity (Fig. 68-16) (115–118). A medial branch block may be relatively easier to perform with less trauma to the Z-joint. In the cervical spine, medial branch blockade has been shown to be a valid technique for the diagnosis of Z-joint mediated pain (119). Overall, medial branch blockade has a reported 89% specificity and 11% false-negative rate (118).

FIGURE 68-16. Lateral view of cervical Z-joint injection, with the arthrogram demonstrating the typical dumbbell shape.

Since the degree of pain relief is a patient’s subjective response, Z-joint injection or medial branch blockade is susceptible to a placebo effect. Other possible causes of falsepositive studies include inadvertent anesthetic spread to pain generators outside of the Z-joint. Research has shown falsepositive rates of 27% to 38% for lumbar blocks, 27% to 63% for cervical blocks, 55% for thoracic blocks, and a 32% placebo effect (95,112,120,121). To minimize false-positive rates, various clinicians have advocated evaluating the response to injecting anesthetics of varying anesthetic durations as well as possibly performing a control injection with saline placebo. A true-positive response is considered to be pain relief lasting for 1 to 2 hours with 2% lidocaine, and 3 to 4 hours with 0.5% bupivacaine, but no effect with saline. However, such a triple block scheme requires three separate procedures and is thus time consuming and costly. Ethical issues arise if a patient accepts the procedural risks and financial costs expecting a therapeutic injection, only to receive a placebo injection. A compromise is to perform a “double block paradigm” using two local anesthetics with different durations of action, one on each of two separate occasions. If each of the two injections relieves pain for the duration expected for the anesthetic used, Z-joint pain can be reliably diagnosed. Published studies have validated this dual blockade paradigm, using comparative local anesthetics for medial branch blocks to anesthetize Z-joints, which constitutes a viable alternative to normal saline controls (100,122).

Potential causes of false-negative responses include venous uptake of the injected anesthetic, aberrant innervation of the target Z-joint, and other technical issues. Since both intravascular injection and epidural spread of injectate can reduce the injection specificity, fluoroscopy plays an important role in maximizing outcomes.

If injection is being performed solely for diagnostic, not therapeutic, purposes, then only local anesthetic should be injected, without corticosteroid. Regarding the placebocontrolled blocks, a positive diagnosis was recorded only if the patient’s pain was completely and reproducibly relieved by each of the local anesthetic but not via the normal saline.

As stated above, double block with local anesthetics of different durations on two separate occasions can reduce (although not eliminate) the false-positive response and placebo effect (122). What constitutes a positive diagnostic response remains the physician’s subjective judgment. For a true concordant response with comparative blocks (100), the patient should obtain complete pain relief with a duration that is consistent with each particular anesthetic solution, though recent published placebo-controlled studies have used a criterion of at least 80% pain relief. This concordant response criterion for identifying Z-joint pain yields a good specificity of 88%, but only marginal sensitivity of 54%, thus suggesting significant false-negatives (100). Expanding the comparative blocks diagnostic criteria to include all patients with reproducible relief, irrespective of duration, increases sensitivity to 100% but lowers specificity to 65% (100). Whether the criterion should be structured to more aggressively prevent false-positive responses versus to prevent false-negative responses may depend on what subsequent treatment will be based on the determination. For additional treatments that can irreversibly alter the patient’s anatomy (e.g., via surgery or radiofrequency ablation [RFA]), preventing false-positive responses becomes increasingly important (100).

Using the dual block technique in patients with chronic low back pain, lumbar Z-joint pain was demonstrated in 15% of younger patients and 40% of older patients (96,98). In chronic neck pain after whiplash injury from motor vehicle injury, Z-joint pain occurred in 54% of patients (99). Another study of patients with chronic neck pain for more than 6 months demonstrated that the prevalence of Z-joint pain was 36% (123). The C2-3 and C5-6 Z-joints were found to be the most common symptomatic joints (99,123). The C2-3 joint was found to be a pain generator in 50% of patients with chronic cervicogenic headache after a whiplash injury (99). It is interesting that using the intra-articular and/or medial branch block, studies have demonstrated that the coexistence of Z-joint pain and discogenic pain in lumbar region is only 4%, while in the cervical spine it is 40% (124,125).

Caution should be exercised using provocation of pain as a sole diagnostic criterion for patient undergoing a diagnostic lumbar Z-joint injection. One study has demonstrated no significant correlation between pain provocation during Z-joint injection and the analgesic response (126).

Therapeutic Effect

The therapeutic benefit of Z-joint injection with corticosteroids remains controversial (127). A past study has suggested positive efficacy of C2-3 Z-joint corticosteroid injections for cervicogenic headache after a whiplash injury (128). Controlled studies have failed to demonstrate such efficacy although the studies had various design flaws (Table 68-5), including the use of saline as a placebo, patient selection bias without using a double block technique, and injection in isolation of other treatments. Selection of patients without using the double block paradigm may potentially include those patients with false-positive results. Finally, injection is not recommended to be used in isolation of other treatments. Rather, when tolerable, patients should be involved in a directed therapy program if they experience significant pain reduction (therapeutic window) after the injection.

A recently published systematic review of the literature from 2004 to 2006 has demonstrated strong evidence for diagnostic injections in the cervical and lumbar spine and moderate evidence for diagnostic injections in the thoracic spine (115). Another published review from 2007 has noted “limited” evidence for intra-articular cervical facet joint injections and “moderate” evidence for intra-articular lumbar Z-joint injections for pain relief (129). It is interesting to note, however, that this study did conclude that there actually was moderate evidence for short-and long-term pain relief from medial branch blocks.

Complications

Potential complications of fluoroscopic-guided, contrastenhanced lumbar Z-joint injections or medial branch blocks are rare. The most common post-procedural problem is transient pain at the injection site. However, there have been rare case reports of meningitis, inadvertent spinal anesthesia, and infection after Z-joint injections (137,138). Recurrent back and neck pain after radiofrequency neurotomy may be due to incomplete ablation or medial branch regeneration (139). Since the dorsal root ganglia are left intact, the ablated medial branches may regenerate. Because radio frequency neurotomy does not permanently denervate the Z-joints or cause inherent instability in the spine, the concern of Charcot facet joint development has little ground and no such cases have been published (140). Also, because the DRG remains intact, deafferentation pain should not occur. Side effects from radiofrequency neurotomy are rare when the procedure is performed correctly but include local pain and infection.

Refferences

Source:  Physical Medicine and Rehabilitation - Principles and Practice

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