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Spinal Injections

If you have been referred for an injection to ease back pain, neck pain, a trapped nerve or sciatica, this article will provide some information on the various types you may be offered.

Spinal injections come in three main forms; epidural, nerve root and facet joint.

Facet Joint Injection

Facet joint injections target small joints at the back of your spine that can become painful if irritated, out of position, or arthritic.

Most commonly facet joints give localised pain in a band across the lower back or shoulders, however they can give pain in any part of the back and even may refer pain down the legs, arms, and into the head. A physical and neurological exam is needed to differentiate facet joint referred pain from nerve pain.

Nerve root injections target the spinal end of a specific nerve, and are useful in cases of sciatica or pain travelling down the arms. When a nerve is irritated in the spine it gives a distinctive pattern of pain. Blocking signal from this nerve usually relieves this.

Epidural injections go into the space around the spinal cord. When nerve irritation is not confined to one specific nerve root, for example in multiple disc herniations, pain signals are blocked from travelling up the spinal cord using an epidural. This is useful in cases of back pain, referred pain, or a combination.

In almost all cases the substance injected is a mix of a corticosteroid and local anaesthetic. Local anaesthetic blocks pain signals, while the corticosteroid is a powerful local anti-inflammatory which, in some cases, will help ease the irritation causing the pain.

Success rates of spinal injections vary. Facet joint injections have a 6 month success rate of between 20 and 40 percent. That is to say, between 20% and 40% of patients report remaining pain free 6 months after injection.

Nerve root block injections have been reported to have provided a 75% success rate, although this includes patients who only reported a 50% improvement or higher.

Epidural injections have a success rate of between 25 and 50 percent, although for lasting relief multiple injections are required.

Risk factors for all injections are broadly the same, although higher with nerve root and epidural injection. Despite being carried out under x-ray the greatest risk is that of nerve injury, with paralysis and permanent loss of sensation, weakness or pain resulting. Other side-effects include aggravation of pain, avascular necrosis (a bone disease caused by corticosteroids), infection, spinal fluid leakage and spinal cord bleeds.

Approximately 1 in every 100 injections will have a serious side-effect, with aggravation of pain being approximately 1 in 8.

Although this may sound like a relatively high risk, current guidelines suggest attempting a series of spinal injections before surgery is considered.