The most common reason for your doctor to recommend this procedure is severe or prolonged back pain that may or may not go down into your leg or buttock on one or both sides. This procedure is most suitable for people whose back pain is a result of disc or facet joint problems related to ageing and arthritis. For this reason, it is usual that you will have a CT or magnetic resonance imaging (MRI) scan of the spine to ensure that there is no cause other than age-related changes in the discs and facet joints to explain your back pain. 

Epidural corticosteroid injection can sometimes be recommended by your surgeon if you have recurrence of your back pain after surgery. This recommendation will usually come after you have had an MRI scan of the spine to ensure that there is nothing that needs further surgical treatment. 

You should wear comfortable clothes that are easy to remove. 

When you make your appointment, you need to let our staff know if you are taking any blood thinning medication. 

Blood thinning medications may need to be stopped for a period of days, or your normal dose reduced, before this procedure is carried out. It is very important that you do not stop taking them without being instructed to do so by your referring practitioner. You will be advised of any such instructions when making your appointment. 

If you have problems lying on your stomach, please make it known when you make your appointment, as this can make carrying out the procedure difficult. 

After the procedure, you will need to lie flat and you may be monitored by our staff for up to 2 hours before being able to go home. You will need to have someone take you home, because you are not allowed to drive immediately after the procedure. 

You will be asked to change into a gown and lie on your stomach on a table. The table will have a thin foam mattress on it and you will have a pillow for your head. 

A metal marker will be taped on the skin of your lower back and images will be used to adjust the position of this marker so that it is at the correct level for the injection. The skin will be marked to indicate where the needle will enter the skin and the metal marker will then be taken away. 

The skin is cleaned with an antiseptic and local anaesthetic is injected to numb the skin and deeper tissues. This is uncomfortable for a few seconds, producing a pin prick and a stinging sensation. You will be awake and only the area where the lumbar epidural injection is being carried out will be numb. 

When the skin and muscles are numb, a thin spinal needle is then guided into the spinal canal and into the epidural space. The placement of the needle in the epidural space is checked by the radiologist by injecting contrast medium. Contrast medium enables the CT to show the area inside the body where the procedure is being carried out more clearly on the images. 

Once it is confirmed that the needle is in the correct position, corticosteroid is then injected. The pressure of the injection may momentarily increase the pain, but this is generally quickly relieved as the local anaesthetic takes effect. 

Depending on the spread of the local anaesthetic, you may feel total numbness of both legs or one leg for up to 2 or more hours. 

The procedure takes approximately 15 to 20 minutes under CT guidance. It may take longer if x-ray is used. The time taken for full recovery, leg function and blood pressure normalisation is approximately 30 minutes to an hour. Some patients require upwards of 2 hours. With preparation time, you should allow 4 hours between entering the radiology clinic and leaving. 

The risks involved in this procedure are rare and minimal, and can include: 

• Increased back or leg pain during the injection, which is temporary and relatively common. It is expected and is not considered a risk of this procedure.
• If contrast is used to check the needle position, there is a small risk of an allergic reaction. The risk of a very serious reaction is less than 1 in every 100,000.
• Allergic reaction to the local anaesthetic used in the skin or mixed with the corticosteroid is very rare, but does occasionally occur.
• If the fluid sac (known as the thecal sac) is punctured by the needle, there may be a quite severe headache for a few days.
• The risk of headache after sac puncture is less than 5%. It is worse with sitting and walking around, and better if you lie down and take lots of fluids and simple pain medication, such as paracetamol.
• Bleeding into the epidural space is also rare and called ‘epidural haematoma’. It is more common if you are on blood thinning medication that is not stopped before having the procedure or you have a blood clotting problem. It causes increasing or persistent back pain after the procedure, and may cause weakness in one or both legs and difficulty emptying your bladder when you go to the toilet.

Image guided injections are accurate and minimise the risks of complications. Very small needles can be used under CT guidance. Relief of back pain and avoidance of, or delay in surgery are the major benefits. The pain relief is often not permanent, but fortunately the injections can be repeated if and when the pain comes back. The generally accepted practice is to limit this to no more than three to four injections per year to minimise the complications of the corticosteroids. 

There is rapid pain relief if local anaesthetic is used and this may last 2–4 hours, but the pain may then return. The steroid takes approximately 48 hours to have effect. In some patients, breaking the pain cycle with the steroid injection results in pain relief, which is maintained for several weeks to months. 

Your doctor will receive a written report on your test as soon as is practicable.

It is very important that you discuss the results with the doctor whom referred you so that they can explain what the results mean for you.