Facet Joint Procedures

Approximately 20% of low back pain complaints can be attributed to the zygapophyseal joints in the lumbar spine1,19-22 and likely account for even higher rates of pain in the cervical and thoracic spines.19,20,22 Also known as facet or z-joints, these joints become arthritic and potentially painful as with any joint in the body, and consequently, older individuals may be expected to be more likely to respond to facet blocks than younger patients.20,21,23 In fact, in a study of older Australians with non-injury-related chronic low back pain, 30% of individuals reported at least 90% relief following placebo-controlled facet blocks.21

Over the past 40 years, our understanding of the innervation of facet joints and their potential as pain generators has greatly expanded.2 We now know that even referred leg pain and hamstring tightness can be associated with facet joint pain and thus mimic features of sciatica. Cervical facet joints may refer pain to the head, neck, and shoulder areas and have well-described referral pattern "maps," whereas thoracic facet joints may produce mid back pain with accompanying neuropathic symptoms as well.22 Along with the evolution of this knowledge, so too have interventional approaches in dealing with facet-mediated pain.

The specific diagnosis of facet-mediated pain is difficult and controversial, however, because there are no reliable factors of patients' history, physical exam, or imaging studies to otherwise effectively determine pain of facet origin. Several studies have evaluated the use of single photon emission CT (SPECT) to determine if abnormalities can predict facet joint disease and therefore predict favorable response to joint injections. One study example by Pneumaticos et al24 determined that patients who had "hot" facet joints treated with steroid injection responded more favorably than patients who also had non-hot joints injected ( joints were selected clinically by the attending physician as is done in typical practice). Despite this and other positive results, SPECT is not routinely used, perhaps because of limited availability and expense.

For diagnostic injections, there is a high false-positive rate for single sets of lumbar injections.19 Therefore two positive diagnostic injections are felt to be required before considering pain to be truly of facet origin, at least for the purposes of clinical research. These injections should be low volume and demonstrate a specific response based upon the expected duration of the anesthetic used.23,25 In clinical practice, this "double block" approach may not required, or practical, given the relatively similar morbidity of rhizotomy (the procedure that should be considered if diagnostic blocks are positive) compared to injections. Others also argue that the improved specificity of double blocks reduces the sensitivity and therefore denies a potentially therapeutic procedure (rhizotomy) to some patients who would otherwise benefit. Again, this approach assumes that the risks and comorbidity of performing rhizotomy in patients with false-positive results is not significantly greater than performing the second diagnostic block.

Potential complications of facet joint procedures include those described in the section on ESI that may be related to needle placement; side effects of sedation, injected medication, or both; and radiation associated with image guidance.22 Septic joints have been reported after intraarticular injections,26 whereas radiofrequency (RF) neurotomy procedures have been associated with painful dysesthesia, anesthesia dolorosa, hyper-esthesia, and nerve root injury22; however, the overall rate of even minor complications is very low.27

Over the years, conflicting results have emerged regarding efficacy of facet joint procedures.22 One of the most recent systematic reviews by Bogduk et al 2 only considered prospective, double blind, randomized, placebo-controlled trials in their evaluation, and determined that controlled, diagnostic medial branch blocks are the only validated method of diagnosing facet mediated pain and that properly performed neurotomy is the only validated treatment for facet joint pain. A more encompassing review was done by Boswell et al.,22 and their results are included in Table 19-2. Their process was similar to the Salahadin et al. review discussed in the section on ESI,4 and short-term and long-term relief were defined as 6 weeks or less versus longer than 6 weeks duration for injections, respectively, and less than or more than 3 months duration, respectively, for neurotomy procedures. Of note, achievement of long-term relief with injection therapy often requires multiple injections. For instance, in their study of cervical facet pain, Manchikanti et al.28 noted an average of 3.5 injections over the course of a year with an average duration of effect of approximately 3.5 months per injection. Interestingly, this benefit of medial branch blocks was noted with or without steroid. Findings, including number of injections and duration of effect, were similar in their studies of lumbar and thoracic medial branch blocks as well.29

Medial branch blocks (MBB) in the lumbar spine have been repeatedly validated for diagnostic utility.2 ISIS guidelines23 suggest that patients should be evaluated for at least 2 hours postinjection, or until relief ceases (whichever occurs first). To be truly diagnostic, relief should also be noted while the patient is attempting activities that are typically aggravating. There is debate regarding the amount of relief required to consider blocks successful,2,20 but 80% pain relief has typically been accepted as the standard for a "positive" response. A recent retrospective study by Cohen et al.20 however, indicates that the patients who reported 50% to 79% improvement following a single diagnostic block did as well with subsequent rhizotomy as those who reported 80% or more relief following diagnostic block. It is also unclear how much secondary factors, including the use of sedation, anesthesia, or both, during diagnostic blocks, affect the results.20

The use of steroids and Sarapin have also been studied for medial branch blockade both in the neck and low back. These substances have not

Debate exists as to whether it is acceptable to perform the procedure under general anesthesia. This may increase the risk of nerve root injury with improper probe placement, because the patient cannot sense and thus warn of impending injury.2 Testing the probe with varied frequency stimulation is important to perform regardless of use of general anesthesia. This allows the interventionalist to assess for motor activation of the nerve root, an important warning sign of probe misplacement.

Other studies have evaluated alternative means for neurotomy, including cryoneurolysis36 and percutaneous laser denervation.37 All three studies have shown promising initial results for short- and long-term relief when performed in the lumbar spine and may become more widespread options in the future.

Cervical MBB Moderate Moderate

TABLE 19-2 Summary of Literature Support for Various Facet Joint Procedures for the Treatment of Chronic Facetogenic Pain as Outlined by Boswell et al22

Procedure Short-term Relief Long-term Relief

Cervical intra-articular Limited Limited

Thoracic intra-articular Indeterminate Indeterminate

Lumbar intra-articular Moderate Moderate

Thoracic MBB

Moderate

Moderate

Lumbar MBB

Moderate

Moderate

Cervical MBN

Strong

Moderate (Strong*)

Thoracic MBN

Indeterminate

Indeterminate

Lumbar MBN

Strong

Moderate

*Long-term relief for cervical facet pain has strong evidence when a multiple lesion per level strategy is used, as reported by Lord et al and advocated by others.23,35 This procedure is not commonly done in the United States and significantly increases operative time.

*Long-term relief for cervical facet pain has strong evidence when a multiple lesion per level strategy is used, as reported by Lord et al and advocated by others.23,35 This procedure is not commonly done in the United States and significantly increases operative time.

demonstrated improved or longer lasting efficacy as compared to bupiva-caine alone in subjects identified as having facet-mediated pain with double blocks.28,29

Intraarticular steroid injections have been shown to be no more effective than saline injections into the facet joints.26,30 Unfortunately the only prospective, double-blind, randomized, placebo-controlled trial for intraarticular cervical facet injections was limited to MVC-related whiplash sufferers.30 The authors screened patients for facet-mediated pain with double blocks and found no benefit from intraarticular steroid versus anesthetic. Results of this study, however, should not be applied to degenerative cervical facetogenic pain, which should be studied separately. A study by Kim et al.31 evaluated intraarticular cervical facet injections in a variety of diagnoses and found that those with "disc herniation" responded better than those with myofascial or whiplash pain syndromes. Intraarticular hyaluronic acid injections were compared to lumbar facet joint steroid injections by Fuchs et al,32 and no difference in efficacy was noted.

Radiofrequency neurotomy of the medial branch nerves (MBN) (and dorsal ramus of L5) has been used extensively to denervate suspected painful facet joints and remains the only available intervention that has demonstrated substantial, long-term relief.2 Early techniques, where an RF probe is placed perpendicular to the path of the target nerve, have been criticized and often demonstrate limited efficacy.2 The more modern approach of placing the probe along the length of the suspected nerve path is recommended by the International Spine Intervention Society23 and has been shown to coagulate a greater length of the target nerves. Because repairing a greater length of nerve will take longer than a shorter lesion, it can be expected that the'parallel probe" technique can result in long-lasting improvement, as has been suggested in reviews of these techniques and studies.2 With parallel probe placement, significant benefit (60%-80% improvement) may last 6 to 12 months or even longer.33 Benefit has also been demonstrated with up to three repeated treatments, and no limit has yet been established as to how many treatments may result in diminished returns.33 Usual RF ablation involves lesioning at 80° C for 90 seconds at each site, but benefit has also been demonstrated with "pulsed" RF current at 2 Hz for 4 minutes at 42° C.34

In the cervical spine, one prospective, double-blind, randomized, placebo-controlled trial has been conducted for assessing medial branch neu-rotomy.35 The authors determined that this treatment is effective in patients who have MVC-related whiplash with demonstrated facet pain (at C3-C4 and C6-C7) using a triple block technique. This technique is similar to the aforementioned double block, with the addition of a single placebo block as well.

When done according to recommended ISIS guidelines,23 no significant complications of lumbar medial branch neurotomy have been described.2

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