Thoracic Facet Injections
The thoracic spine may be an under-served pain generator equally in men and women. Review of thoracic pain literature, however, finds repeated references to the thoracic spine as a “far less common” problem area than the neck or low back. Per Dreyfuss, the relative incidence of cervical, thoracic, and lumbar pain in a Netherlands pain clinic was 5:2:20, respectively.1 In 2000, Mcinerney et al noted nucleus pulposus herniations were “far less common” in the thoracic spine than in the cervical and lumbar regions.2 He rated the incidence of thoracic disc herniation to be from 0.25% to 1% of all disc herniations. In 2004, Manchikanti et al noted the prevalence of facet joint pain in patients with chronic cervical spine pain was 55%, with thoracic spine pain at 42%.3 Thoracic facet joint pain however has been recognized as equally disabling as neck and low back facet conditions. Manchikanti et al concluded from 1997 to 2006 there was exponential growth in the performance of facet joint interventions.4 Presumably most of these procedures were directed to the neck and low back.
But what pain specialist does not hear, on a daily basis, about pain under the shoulder blade or pain at the bra line. Perhaps it is our prioritizing of the neck and low back that puts the thoracic spine on the back burner. Perhaps it is our perception that thoracic pain is less important, less common, or less debilitating that it is overlooked. Perhaps it is the daunting differential diagnosis of thoracic pain that distracts us from the simplicity of treating thoracic facet pain.
Evidence for Thoracic Facet Joint Interventions
As is the case with neck and low back pain, anecdotal results in the thoracic spine for fluoroscopically-guided pain management procedures in the hands of properly trained physicians who customize their patients’ care can be excellent (see Figures 1 and 2 for illustration of thoracic medial branches). Pain management techniques have been evaluated for utility and are showing promise in the thoracic spine—not only for diagnostic but also therapeutic capability. Atluri in 2008 established that evidence for a diagnosis of thoracic facet joint pain is with controlled comparative local anesthetic blocks at level I or II-1.6 The evidence for therapeutic thoracic facet joint interventions is level I or II-1 for medial branch blocks. The recommendation is 1A or 1B/Strong for diagnostic and therapeutic thoracic medial branch blocks. The incidence of chronic mid and upper back pain caused by thoracic facet joints was noted to be 34% to 48% of patients based on responses to controlled diagnostic blocks. Conservative modalities and conventional treatments such as heat, cold, anti-inflammatories, bracing, physical therapy, acupuncture, Pilates, yoga, and chiropractic can be applied adjunctively.
The differential diagnosis of thoracic pain is extensive and may ultimately and justifiably distract the physician from facet-mediated pain. This differential includes:
Further confounding the search for thoracic facet-mediated pain is the overlapping, redundant patterns of competing structures in and around the thoracic spine (see Figures 3 through 8). Dreyfuss et al provoked normal thoracic facets and produced a partial pain pattern map.4 Fukui et al also mapped out some thoracic facet patterns.8 Young et al produced a composite diagram of costotransverse joint pain patterns.10 Displayed are cervical disc and cervical facet joint patterns in addition to a typical myofascial trigger point map. One notes how these potential pain generator patterns overlap. To complicate the diagnostic challenge, the more precise anatomic location of the thoracic medial branches has been dissected and displayed. These locations overlap with the pain patterns we’ve already seen. The shared location of trigger points with medial branch nerves suggests many of the so-called trigger point injections that I served up in the past were probably medial branch blocks.
Anterior and Lateral Disc Protrusions in the Thoracic Spine
Returning to Mcinerney et al and his study in 2000 of thoracic disc herniations, a cursory review of my office charts produced at least twenty examples where thoracic MRIs were interpreted as unremarkable by the radiologist yet I was able to discern obvious anterior and lateral protrusions.2 It is typically easy to predict where a patient’s thoracic pain will be by examining the MRI (see Figure 9). This is not to presume these patients necessarily had discogenic pain, internal disc disruption with or without radicular features but, in fact, all twenty reported 90% to 100% immediate relief with intraarticular thoracic facet injections under fluoroscopy. These responses were obtained by the nursing staff independently post- procedure with open-ended questions.
The apparent reason for the frequency of anterolateral disc protrusions in the thoracic spine is the reversed or kyphotic curve compared to the lordotic neck and low back where the pressure on the thoracic disc is now anterior rather than posterior. The thoracic anterior longitudinal ligament prevents the disc from protruding straight forward so it protrudes laterally. The interest of the radiologist is directed posteriorly to where the nerves are. It is in the interest of the pain management specialist to note the disc protrusion—whether posterior or anterior—as it implies disc space narrowing, facet compression and inflammation posteriorly.
If the patient gets excellent immediate temporary relief from intraarticular facet injection then confirmatory medial branch block is indicated. If the patient gets excellent immediate temporary relief from confirmatory medial branch block then medial branch neurotomy is indicated. Some physicians prefer to go first directly to medial branch block. Since Manchikanti et al in 2004 noted the false positive rate for single blocks with lidocaine was 63% in the cervical spine, 55% in the thoracic spine, and 27% in the lumbar spine for facet joint injections, a dual block is recommended.3
Thoracic Intraarticular Injection
Dreyfuss and others have described the technique for thoracic intraarticular injection.1 In 2000, Manchikanti et al concluded the clinical picture alone was unable to characterize pain from lumbar facets.14 This implies the gold standard for diagnosing facet mediated pain is intraarticular injection (preferably fluoroscopically-guided.) It has been suggested that thoracic facet injections are not painful and sedation is unnecessary. I would recommend having sedation available. Thoracic joints, if inflamed, can be painful during injection. Smith et al in 2009 concluded that systemic review provided no significant evidence of the influence of sedation—either with midazolam or fentanyl—in the evaluation of cervical and lumbar facet joint pain with controlled nerve blocks with an indicated evidence of Level II-1. His review applied stringent criteria of at least 80% pain relief and the ability to perform previously painful movements after the diagnostic blocks.15