May 1, 2018 Dr Chee L Khoo
Chronic, persistent low back, lower extremity pain, and radicular pain may be secondary to disc herniation, disc disruption, disc degeneration, facet joint disease, spinal stenosis, or post lumbar surgery syndrome resulting in disc-related pain with or without radiculitis. The specificity and sensitivity of the symptoms and signs are low and therefore, not as reliable as we think in getting to the precise diagnosis. The patho-physiology and mechanism of the symptoms is highly complex and remain controversial.
Radiation of pain needs to be carefully interpreted. Somatic referred pain in the buttock or lower limb can be expected. Somatic referred pain is mostly in the buttock or lower extremity with any type of pain generators in the lumbar spine and it should not be confused with radicular pain.
The assessment of differential diagnosis is based on history and physical examination which includes neurological examination, motor examination, sensory examination, reflex examination and application of provocative manoeuvres including straight leg raising test, crossed straight leg raising test, bowstring sign and slump test. Sciatica was highly sensitive for a clinically important herniated disc, as was old age for spinal stenosis and compression fractures. Subjective symptoms of numbness is considered reasonably sensitive but not specific as a sign of radiculopathy.
Positive findings on CT or MRI can sometimes be misleading as patients can have multiple pathologies and may not be related to their symptoms at all. Further, multiple levels of disc and nerve root pathologies is often present. Deciding which level is the cause of the symptoms is not always easy. We certainly don’t want to operate on the wrong level.
Opioids for chronic pain is often frown upon even though sometimes, opioids are needed but increasingly, epidural injections are used as alternative to high dose opioids. Interventional procedures have evolved and improved over time since epidural injection was first introduced for low back pain and sciatica in 1901. One of the major contributors in the improvement of these interventions is the advancement of imaging guidance technologies. The utilisation of image guidance has dramatically improved the accuracy and safety of these interventions.
There are three different techniques for epidural injection: caudal, interlaminar and trans-foraminal. Epidural injection can either be diagnostic (assess the source of pain) or therapeutic (aiming to fix the symptoms) or or both.
Diagnostic spinal injection
The theoretical basis of controlled diagnostic blocks is that if a patient genuinely has pain from a particular target structure, complete or near complete relief of that pain should be obtained consistently whenever that structure is anesthetised and repeating the diagnostic block can increase the diagnostic accuracy by testing for consistency of response and for the effect of different aesthetic agents.
In the latest evidence based clinical practice guidelines from the American Society of Interventional Pain Physicians, for the lumbar spine:
Diagnostic selective nerve root block
- Diagnostic selective nerve root blocks are recommended in the lumbar spine in select patients with an equivocal diagnosis and involvement of multiple levels.
Diagnostic Lumbar Facet Joint Nerve Blocks
- The evidence for diagnostic lumbar facet joint nerve blocks is good with 75% to 100% pain relief
as the criterion standard with controlled local anaesthetic or placebo blocks. Thus, diagnostic lumbar
facet joint nerve blocks are recommended in patients with suspected facet joint pain.
Diagnostic Sacroiliac Joint Blocks
- The evidence for diagnostic intraarticular sacroiliac joint injections is good with 75% to 100% pain relief as the criterion standard with controlled local anaesthetic or placebo blocks. Thus, controlled sacroiliac joint blocks with placebo or controlled comparative local anaesthetic blocks are recommended when indications are satisfied with suspicion of sacroiliac joint pain
Therapeutic Epidural Injections
- The evidence for caudal epidural, interlaminar epidural, and transforaminal epidural injections is good in managing disc herniation or radiculitis but only fair for axial or discogenic pain without disc herniation, radiculitis or facet joint pain with caudal and lumbar interlaminar epidural injections, and
- limited with transforaminal epidural injections;
- For spinal stenosis with caudal, interlaminar,and transforaminal epidural injections, the evidence is fair;
- For post surgery syndrome with caudal epidural, the evidence is also fair but as good with transforaminal epidural injections.
The recommendation for epidural injections for disc herniation is that one of the 3 approaches may be used; for spinal stenosis any of the 3 approaches are recommended; whereas for axial or discogenic pain, either lumb
ar interlaminar or caudal epidural injections are recommended. However for transforaminal the evidence is limited for axial or discogenic pain and post surgery syndrome.
Therapeutic Lumbar Facet Joint Interventions
- The evidence for lumbar conventional radiofrequency neurotomy is good, limited for pulsed radiofrequency neurotomy, fair to good for lumbar facet joint nerve blocks, and limited for intraarticular injections.
- Among the therapeutic facet joint interventions either conventional radiofrequency neurotomy or therapeutic facet joint nerve blocks are recommended after the appropriate diagnosis with controlled diagnostic lumbar facet joint blocks.
Therapeutic Sacroiliac Joint Interventions
- The evidence for sacroiliac cooled radiofrequency neurotomy is fair; limited for intraarticular steroid injections; limited for periarticular injections with steroids or botulinum toxin; and limited for both pulsed radiofrequency and conventional radiofrequency neurotomy.
- Due to emerging evidence for intraarticular injections, they are recommended in select cases with or without periarticular injections. Cooled radiofrequency neurotomy is recommended after appropriate diagnosis confirmed by diagnostic sacroiliac joint injections.
Thus, the right spinal injection for the right patient for the right condition can be of benefit. Often, it can be confusing to which injection should be given at which site. A quick word with our friends at Spectrum Medical Imaging can solve the confusion. This week’s chart is quite helpful to.
An Update of Comprehensive Evidence-Based Guidelines for Interventional Techniques in Chronic Spinal Pain. Part II: Guidance and Recommendations. Pain Physician 2013; 16:S49-S283