The management of a medical problem consists of the diagnostic phase and the therapeutic (or treatment) phase. In pain medicine, a more precise tissue specific diagnosis can be made with interventional diagnostic injections in which a specific target source is identified by the use of some imaging technique, such as fluroscopic x-ray, CT scan or ultrasound, and the presenting pain is either temporarily eliminated or activated by the procedure. Precision diagnosis is fortunately not often required. However, where clinically relevant, such an approach may be necessary particularly as it might lead to a specific treatment for the pain. Interventional treatment that might follow includes needle interventions such as radiofrequency neurotomy and epidural injection; additionally, interventional diagnostic procedures can be used to help plan surgery.

Medial Branch Blocks and Facet Joint Injections are used to diagnose and/or treat facet joint pain. The facet joints are the small paired synovial joints that join adjacent vertebrae at their posterior margins: the anterior (front) elements of two adjacent vertebrae are joined by the intervertebral disc. The facet joints can be a prominent sole source of spinal pain.

Are The Facet Joints The Cause Of Pain?

Facet joint pain presents with local neck or back pain with or without referred pain. In the cervical spine, the local pain is in the neck, and the referred pain can be into the head, the shoulder, the shoulder blade and the arm. In the thoracic spine, the local pain is in the middle back, including in between the shoulder blades, and spreads out around the chest sometimes as far as the front of the chest. In the lumbar spine the back pain can be referred into the buttock, hip and leg.

It has been shown in studies that the facet joints can be damaged in accidents such as in motor vehicle accidents, and that the painful changes in the facet joints do not in general show up on x-ray, CT scan or MRI scanning.

The only way to determine whether the facet joints are the cause of pain is to either inject the joint or its nerve supply with local anesthetic in order to ascertain whether or not the pain is eliminated on the day of the injection. This process of stopping pain is known as a block (the aim is to block out the pain). The nerve supply to the facet joint is via the medial branches of the dorsal ramus, which in turn comes from the spinal nerve. Thus, block of the nerve supply to the facet joints are called medial branch blocks.

Studies have shown that one successful block means that the diagnosis of facet joint pain is about 70% likely. That is, false positive blocks do occur (sometimes a positive block on one occasion is followed by a negative block on another occasion). The diagnostic confidence can be increased by repeating the block with other anaesthetic agents. Two positive blocks increase the diagnostic confidence to 90%.

Facet joint injections are used in two circumstances. The first is in the more acute phase of pain. Here an injection is considered if the pain is not settling rapidly enough with the use of modalities such as exercise, medication and physical therapy. The injection in such a circumstance may also include some cortisone. The second is in more chronic presentations where the pain is not always present. If pain cannot be reliably predicted to be present in the six hours afterward a diagnostic nerve block, then the block is not relevant. If a facet joint injection leads to some prolonged improvement, it is possible that the facet joint is the source of pain.

Medial branch blocks are used in recalcitrant chronic pain situations if it is considered that specific treatment to the facet joint is required. This treatment is known as radiofrequency neurotomy (RFN). It is also called radiofrequency denervation. The treatment applies heat lesions to the nerve. It can lead to prolonged pain relief.

Injection protocol:

Preparation:

It is first important to understand what is being attempted. The major point of the injection is to determine whether or not pain is altered in the 6 hours after the injection. Thus, it is important to have a method for recording the pain score. The most commonly used pain scoring system is called the Visual Analogue Scale (VAS). Pain is rated through a range from 0 to 10. Zero 0/10) indicates no pain; 10/10 indicates pain that is almost unattainable. At 10/10 a person cannot think, move or function at all. Indeed, it would almost be impossible to come in for an injection with a score of 10/10. Each person needs to consider what their VAS is, and apply it to each area of pain. For example, it might be that the back pain is 6/10, and the leg pain 4/10. If so, two columns of the pain chart would need to be recorded. As the aim of the block is to see if pain is altered, it is essential that pain is present at the time of the injection. Thus, do not take pain killers on the day of the injection.

Some people are understandably anxious about the injection. These injections are very safe, so fear of untoward effects should not be a concern. They are also generally not too painful, and can be done quickly. Anxiety itself can lead to increased pain during the procedure. This happens because adrenaline release, which accompanies anxiety, alters pain receptor activity, leading to worse pain. It has been shown that if people can control anxiety they can make the procedure comfortable. The techniques that can be used include:

• Be rational; recognize that this is a trivial procedure, and that it will be over quickly.

• Use relaxation techniques. If you are not sure about these, do some research on the Net or in the library. One usual technique is to use distraction: think about something positive or enjoyable during the injection. If you want some help with distraction, start a conversation in the procedure room, and the nurses or proceduralist will engage in that process. If you would like to hear a particular piece of music during the procedure, bring it in and we will play it for you.

• If necessary, speak to a psychologist about how to deal with the fear of an injection. Cognitive-behavioural techniques can be very helpful. Occasionally it may be relevant to use an anti-anxiety drug. However, this is not recommended, as it may affect the ability to accurately record the pain score.

The Procedure:

 The injection itself consists of placing a needle through the skin. Precision and safety is ensured as the needle is guided into position with the use of fluoroscopic x-ray control, and the needle is placed directly adjacent to the target structure. A thin needle is used (not much thicker than an acupuncture needle).  Apart from local bruising and pain, the procedure does not have any side effects.  At times pain and bruising can occur for a few days, but the chance of this is around 5%.

It is recommended that you be driven home after the procedure.  Repeat confirmatory injections are usually performed one to two weeks later if the first injections successfully block the pain. If good relief is obtained at the first session, and this is confirmed at the next session, then it is concluded the facet joints are the main cause of pain. The treatment with radiofrequency neurotomy (RFN) is then indicated.

If there is no relief following the first session then it may be necessary to investigate other adjacent facet joints; again two sets of injections may be required.  If there is still no relief then we can conclude that the facet joints are not the cause of your pain.

More on the Pain Chart

As mentioned above, you must rate your pain between 0 and 10, with 0 equaling no pain, and 10 equaling the worst pain imaginable (a pain that is perhaps not attainable). You need to think about how you are going to record the result of the block. In essence, the doctor needs to know whether or not you feel that the block was in the right spot. The doctor wants to know; “did the block get rid of your pain?” You need to work out how to communicate this on the pain chart.

First, consider where you get pain. Consider the main site of pain (typically the neck or the back) and score it. Try to use a reproducible activity or position in which the pain is at its worst to estimate the pain score. Then consider the secondary pain sites, such as the shoulder, the head, the arm, the buttock and the leg. Estimate the pain score for that region also.

For instance, you may have low back pain in addition to leg pain and these two pains should be described separately.  In such an example, it may be that the injection may totally relieve the low back pain, but may not help the leg pain.  This is important information for your doctor to assess when making recommendations regarding further treatment.

Example:

In this example the back pain has been relieved, but the leg pain is the same. This indicates the back pain may be related to the facet joint, but the leg pain is not. Pain charts will need to be interpreted by your doctor and discussed with you.  Please feel free to ask your practitioner or the clinic nurse practitioners questions if any clarification is required.

Discography is a diagnostic procedure that seeks to ascertain whether or not an abnormal intervertebral disc is also the source of a person’s spinal pain problem. It is an invasive procedure that should only be used when all other reasonable treatments have been tried and failed, and when there is a fair chance that the result will lead to some definitive change in the treatment. Discogenic pain (DP), or, pain derived from the disc, cannot be diagnosed using x-rays and other imaging techniques including MRI. These imaging techniques show changes that are most often either genetic or age related; furthermore, these changes are not specific in determining whether or not a disc is the source of pain. Degeneration of discs occurs frequently in people who have never experienced significant spinal pain. 

Although lumbar DP cannot be diagnosed using imaging, there is a significant relationship between disc morphology as determined by discography, and clinical pain as determined by the subjective provocation phase of PD. As a consequence, a particular cohort of spinal pain patients can be diagnosed as having discogenic pain. As alluded to above, it is only important to diagnosis DP if it leads to a successful treatment. Sometimes it is used to make a definitive diagnosis, which leads to a cessation of the need to undertake other treatments. 

The sacroiliac joint (SIJ) is a complex joint that can be a cause of LBP, especially pain around the sacrum. Referred pain from the SIJ can spread from the back down the leg as far as the foot. 

It is uncommon for there to be a need to define the SIJ as the source of pain. However, when a person with chronic disabling LBP has failed conservative treatment including exercises and physical therapy, consideration can be given to ascertaining the source of pain. Other such diagnostic tests for LBP include medial branch blocks, facet joint injection and provocation discography. 

A SIJ block is a diagnostic block that attempts to ascertain if the SIJ complex is likely to be the source of a person's pain. The block is done under the visual control provided by an X-ray machine, and in particular, one that enables the operator to move the direction of the beam at will. CT scan and ultrasound can also be used, but the former is more time consuming with higher radiation, and the latter does not allow the use of contrast to ensure that the injectable material ends up where it should. 

Thus, the diagnostic block entails the injection of the synovial joint, and the injection either of the ligament at the upper and posterior part of the joint and/or the nerve supply to the ligament.