Low back pain is a major problem. Most of the cases of low back pain can be treated by rest, medication and exercises. Injections are part of non-surgical method of treatment of low back pain. They could be considered after a course of medication and physical therapy but before surgery.
Injections could be used for diagnosis of the origin of the pain as well.
For diagnosis, it involves passing the needle and instilling the medication like lidocaine [a local anesthetic] into the desired structure. If the pain is relieved, the particular structure is the cause of pain.
This could be very helpful in guiding treatment.
Injections provide pain relief, sometimes more effectively [in selected cases] because they deliver medication directly to the anatomic location that is generating the pain.
The relief may be long-lasting or short-term, depending on the injection.
Common types of injections for back pain relief include:
- Epidural steroid injection
- Selective nerve root block
- Facet joint block/Facet rhizotomy
- Sacroiliac joint block
To understand the application of these injections, you should have an idea of spine anatomy.
Following articles would give you an idea about spine anatomy
Epidural Steroid Injection
epidural steroid injection is most common type of injection given for back pain. In this, a steroid solution is injected directly around the dura.
The success rate is generally 50%. That means 50% of the patients would have significant pain relief. The effect of injection lasts from one week to one year.
General consensus [though there is lack of significance evidence] is 3 injections per year.
Risks of epidural steroids include
- Puncture of dural resulting in CSF leakage.
- Infection of epidural spac.
- Damage to a nerve root [very rare]
Epidural steroid injections should not be performed on patients whose pain is from a tumor or infection.
Selective Nerve Root Block
Selective nerve root block is primarily used to diagnose the specific source of nerve root pain. It is also used for relief of back pain and leg pain.
Imaging studies may always be not able to pin point the inflamed root.
In a selective nerve root block, the nerve is approached at the level where it exits the foramen. A mixture of a steroid and lidocaine [anesthetic agent].
Selective nerve root block is performed under fluoroscopy.
If patient gets relieved after injection, the site of pain generation gets confirmed.
The anesthetic agent acts for short time only. However, the steroid helps reduce inflammation around the nerve root.
Selective nerve root may temporarily worsen the pain as injection is applied near the nerve root which might get irritated by the drugs.
Like epidural steroids, selective nerve root block can be applied three times a year.
Facet Joint Block and Facet Rhizotomy
This is effective when the facet joint itself is the pain generator. It is also a diagnostic method just like selective nerve root block to confirm if the facet joint is pain generator.
Facet joints often can be cause of back pain.
This procedure is also done under fluoroscopy.
The needle is inserted into the facet joint capsule to inject lidocaine + steroid. If the pain is relieved, the specific facet joint is the pain generator.
Just like other two described procedure, facet joint block can be done up to three times per year. There are very few risks associated with this technique.
If facet block injections provide good but temporary relief, , a facet rhizotomy may be considered for lasting pain relief.
In this procedure a needle with a probe is inserted just outside the joint. The probe is then heated with radio waves and applied to the sensory nerve, disabling it.
Disabling the nerve prevents the pain signals from getting to the brain.
A facet rhizotomy injection is successful in providing lasting pain relief for approximately 50% of patients.
Sacroiliac Joint Block
Sacroiliac joint block is used for diagnosing and treating the low back pain associated with sacroiliac joint dysfunction.
This procedure is also done under fluoroscopy where a needle is inserted into the sacroiliac joint. A mix of lidocaine and a steroid are injected and relief is gauzed.
An SI joint block injection may be repeated up to three times per year.
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