Effectiveness of Cervical Transforaminal Epidural Steroid Injection

Background and Project Justification: Neck pain is now the fourth leading cause of years lost to disability, shortly after back pain, depression, and arthralgia. Cervical radiculopathy, a common cause of neck and radiating arm pain, is estimated to afflict 83:100,000 individuals yearly. Age-related cervical spondylosis and disc herniation are the most common causes, with the C6 and C7 nerve roots most frequently affected. In general, patients who experience new onset radicular pain tend to improve within 4-6 months, with complete recovery in over 80% of patients by 24-36 months. However, a significant proportion of patients experience severe pain and associated functional impairment despite conservative care, which often prompts physician directed interventions.

Cervical transforaminal epidural steroid injection (TFESI) is a target-specific treatment for refractory radicular pain. Analgesic mechanisms for epidural steroid administration include reducing inflammation at the nerve root, reducing nociceptive input from somatic nerves, stabilization of neural membranes, and blockade of C fiber activity in the dorsal root ganglion . Previously, this procedure was associated with rare but catastrophic neurologic injury, though to be related to inadvertent deposit of particulate steroid into the vertebral artery or radiculomedullary arteries, both of which traverse through or close to the cervical neuroforamina . Since the physician community has adopted new guidelines that include the use of only non-particulate steroid during cervical TFESI , neurologic infarction has not been reported in the literature. When the Spine Intervention Society (SIS) clinical practice guidelines are employed, large cohort study demonstrates zero prevalence of serious complications associated with this procedure .

While high-quality outcome literature demonstrates both efficacy and effectiveness for analogous use of this intervention in the lumbar spine, far fewer studies have addressed clinical outcomes associated with cervical TFESI in which appropriate procedure technique , outcome measurement, data analysis, and results interpretation have been reported . Outcome literature reporting on the use of cervical TFESI is limited by small sample size, retrospective design with loss of follow-up, lack of categorical data analysis, and a failure to stratify results by demographic and clinical variables that potentially influence pain and functional outcomes. Further, outcome literature reports on the effect of particulate steroid injectate during cervical TFESI is no longer relevant to appropriate clinical practice in the context of unequivocal guidelines. Pragmatic studies with a cervical TFESI arm in which dexamethasone was use do allow for some insight regarding success rates associated with this procedure; calculates of success rates in these studies arms demonstrate responder rates of 60% achieving >50% pain relief (CI95 35-85%) at 4 weeks, 55% achieving >50% (CI95 43-67%) at 8 weeks, and 65% achieving >50% at 12 weeks (CI95 48-81%). These responder rates are encouraging, but limited by wide 95% confidence intervals due to small sample size. Prior systematic review has concluded that the evidence for treatment benefit of radicular pain by cervical TFESI is of very low quality due to multiple limitations in study design introducing risk of bias, but does overall suggest approximately 50% patients experience 50% relief of radicular pain for at least 4 weeks after cervical TFESI.

Additional clinical outcome literature is needed, particularly given recent policy decisions, such as that of Oregon State in relation to ending coverage of epidural steroid injections at any spinal level. Without expansion of the evidence-basis for this important procedure, there is a risk that this treatment option may be taken away from patients suffering from cervical radicular pain by further policy change. A sham-controlled trial, similar to the Ghahreman study, would be ideal; however, due to cost considerations germane to a study designed and conducted in a manner that would prevent any possible criticism from the larger medical community, we instead propose a high-quality, large prospective cohort study as a significant contribution to the literature. Even the best designed trials, such as Dreyfuss' 2006 study, have been underpowered to definitively demonstrate effectiveness; notably, the lower bound of the 95% confidence interval of the proportion of treatment responders in this study was 35%. The investigators aim to conduct a large enough cohort study narrow the 95% confidence interval of the proportion of responders substantially. Preliminary data from our center demonstrates a responder rate of 55% at 4-week follow-up (n=22), based on a definition of ≥50% improvement in index pain (Appendix A). These data represent analysis of consecutive patients who underwent cervical TFESI for unilateral radicular pain as a part of a different prospective outcome study at our center, nearing completion. This responder rate represents a conservative estimate of what might be expected in the proposed work, as the current study includes less stringent inclusion and exclusion criteria.

Further, the investigators intend to use the results of this study as foundational data from which to propose a randomized controlled study through a large federal funding mechanism. It is imperative that such a trial be conducted by investigators who are experienced with this procedure and understand the appropriate standards for the design and interpretation of the results of a study of a treatment intervention for pain. Our spine research group is well-positioned for this, and we absolutely welcome the input and mentorship of the Spine Intervention Society Research Division, Board of Directors, and other leadership towards this mutual goal.