Interventional Spinal Pain Management: general principles
Definition: The term “interventional” applies to the range of techniques which lie between “conservative” care with self help, pain medications and physical therapies and surgery which implies open dissection of the back or neck to access internal spinal structures for treatment. Most interventions are needle based using injections and electrical treatments or instruments which can be deployed through a needle, a fine catheter or an endoscope (effectively a small diameter hollow tube with a light and a fibre-optic to look through). My phrase “anything with a needle, nothing with a knife” encapsulates the concept.
Most commonly, acute episodes of spinal pain (ie short lived or recent: acute and chronic refer to duration, not severity) are managed by GPs and physical therapists (physiotherapists, chiropracters and osteopaths). An exception may be acute sciatica which can be sufficiently severe to warrant an early injection. if problems don’t settle and become persisting or long lasting (“chronic”) usually physical therapies act to maintain function or to give short lasting relief of pain, but do not take away the pain altogether, nor make a “step-change” in the pain problem (ie a long-lasting and non-reversible improvement in symptoms). In this situation, the object of interventional management is to make this “step-change” in reducing symptoms and to bring the episode to an end, rather than to reapply maintenance treatments over the long term.
The role of Inflammation:
In general, local inflammation caused by tissue damage and the healing response to that is a very potent cause of pain and if that element of the problem can be relieved, the pain will be reduced. This is the object of steroid injection treatments, to reduce local inflammation and thus pain. The trick is to get the steroid or other treatment directly to the site of the problem. The techniques for doing this are described below.
Acute inflammation is mainly mediated by local chemical messengers (such as (prostaglandins, bradykinins ). If inflammation persists, immune cells become involved and attempts at healing by fibrosis or scarring occur but do not always resolve the situation and instead become part of the problem. Therefore, sometimes techniques aimed at reducing or breaking up adhesions (adhesiolysis) may also be required.
Synthetic corticosteroids (usually referred to as cortisone, though this particular chemical is not used since it is too short acting) treat both chemical and cellular mechanisms of inflammation and can be helpful in both situations.
Side Effects of Steroid Spinal (and other) Injections:
There is no such thing as a free lunch. There is no such thing as a treatment or course of action (or sometimes inaction) which is without any possibility of an adverse outcome. Someone, somewhere must have experienced a disaster from anything which is commonly done in the interventional treatment of spinal problems, whether I am aware of it or not!
If you are not willing to encompass the possibility of any level of risk, do not proceed with these treatments. However, that said these treatments are adequately safe for everyday purposes and the probability of a major adverse event is very low. It is difficult to give any estimate of frequency for rare events but it is certainly less than the everyday travel risks we take. For example in 2005 there were 1,106 car drivers and 557 passengers killed on the roads of Great Britain and 1115 killed in air crashes in 2010 (source, Wickipedia). By comparison, the number of major events ever reported for spinal injection procedures are in the tens or perhaps a few hundreds: no treatment which killed a thousand people a year (worldwide) would be tolerated!
Spinal injections of steroid could:
- destabilise diabetes or blood pressure.
- Steroid under the skin could cause thinning (steroid skin atrophy)
- cause a persisting flush reaction in the sunburn area of the neck (usually only in young women prone to blushing) which last a few weeks
- interfere with menstrual peroids for 1 or 2 cycles
Number of Injections
There are no strict limits to the number of spinal steroid injections which can be given and in practice this is governed mainly by common sense. There are very few situations in which regular or frequent steroid injections are a justified or necessary management plan.
Radiofrequency (RF) Treatments
Another important type of treatment is the use of finely tuned electrical energy in the radio wave frequency band to produce highly controlled and targeted local heating or tissue removal. These are referred to broadly as radiofrequency (RF) treatments.
RF nerve lesioning
by placing a radiofrequency electrode with a small heating tip (5 or 10mm) directly upon a small sensory nerve and heating to 80°for 1 minute, the clinician can selectively disrupt the nerve without burning or charing surrounding tissue and thus remove the sensation from a single joint or structure and so relieve pain in the long term (unless the nerve regenerates). This is the basis for treatment of facet joint pain in the back and neck with “RF denervation”. Please note: RF heating is often painful for a week or 2 after treatment.
Pulse RF (PRF)
Another use of RF energy is to pulse current on and off and deliver energy without significant heating. The true mechanism of PRF in relieving pain is not fully understood but it probably mainly inhibits pain transmission. It does not damage or destroy nerves and has no known major side effects. It is a very useful treatment for nerve root pain and in my hands is the main-stay for nerve irritation in the neck (brachalgia).
It is increasingly used in solid tissues and I also use it to ameliorate (reduce, make better, rather than “cure”) intervertebral disc pain occasionally in the peripheral joints (fingers, shoulders, hip and knee) and recently to block the nerves supplying major joints such as the shoulder, knee or hip (see interesting cases).
This is a word made from cold and ablation (or tissue removal). It refers to a specific use of RF energy tuned in such a way as to result in the formation of a high energy field exactly on the tip of the coblation needle which is sufficient to cause disruption of molecular bonds in tissue with which it is directly in contact (the tissue vapourises). This allows very exact removal of damaged or pain generating tissue and is one of the main ways I treat painful, bulging intervertbebral discs which are causing back pain (discogenc pain) or sciatica (coblation nucleoplasty). There are no systemic or long term adverse effects of coblation.