- There is medium quality evidence that cervical medial branch blocks have diagnostic utility in the investigation of pain in adults.
- The procedure appears to be valid, safe, reasonably accurate and clinically useful in the diagnosis of chronic cervical pain.
- Evidence on the accuracy of this procedure was provided by one guideline, one systematic review, six experimental studies and two comparative studies.
- The experimental and comparative studies (covering a total of 555 enrolments) provided more specific information on prevalence of pain, false positives and diagnostic utility.
Double-blind, comparative medial branch blocks, followed by an independent outcome assessment, may be used in the investigation of cervical pain in adults (B).
Certain joints in the neck (known as zygapophyseal, z- or facet joints) have a nerve supply from nerves called medial branches of the cervical dorsal rami. When a particular neck joint is thought to be the source of a person’s pain, the medial branches supplying that joint are injected with local anaesthetic. If the joint is indeed the source, the pain will be completely relieved for a short period of time.
- Chronic spinal pain.
- Persistent neck pain (eg attributed to a motor vehicle or work- related accident).
- Headache of cervical origin (see also third occipital nerve block).
Under x-ray control, a fine needle is inserted into the side of the patient’s neck onto a specific area of bone. A small amount of local anaesthetic is injected on to or around the medial branch nerve. As two medial branches supply most of the joints in question, the procedure may need to be repeated at the next level.
The procedure is carried out in a radiology suite, operating theatre or similar facility with access to a C-arm fluoroscope.
This nerve blocking procedure is performed by a doctor with appropriate training. In the New Zealand setting this is most likely to be a musculoskeletal physician, anaesthetist or radiologist. The assistance of a radiographer is required during the procedure. Afterwards an independent assessor, for example a registered nurse, usually monitors the effect of the blocks for up to two hours.
One guideline, one systematic review, six experimental studies and two comparative studies provided information on the accuracy of cervical medial branch block.
The American Society of Interventional Pain Physicians produced a wide-ranging guideline on techniques for the management of chronic pain (Manchikanti et al, 2003), including a review of controlled clinical studies of the diagnostic utility of medial branch nerve blocks. They concluded that comparative medial branch blocks with local anaesthetic were valid and identify the source of pain in 85% of cases. The authors of the systematic review concluded that diagnostic medial branch blocks (or intra-articular facet joint injections), when performed under fluoroscopic visualisation according to International Association for the Study of Pain (external link) criteria, are safe, accurate and clinically useful in the diagnosis and therapeutic management of chronic spinal pain (Boswell et al, 2003).
The three experimental studies and one comparative study not included in the above guideline investigated the diagnostic utility of cervical medial branch blocks in people with neck pain. Speldewinde et al, 2001 (n=97) calculated that the prevalence of z-joint pain mostly due to motor vehicle or work related accident was 36% rather than the 54% to 60% found in other studies included in the above-mentioned reports. Barnsley, Lord, Wallis & Bogduk, 1993 (n=55) calculated that the false positive rate for a single, uncontrolled diagnostic block for cervical z-joint pain was 27%. One study (Lord et al, 1995, n=50) estimated the false positive rate for the more stringent placebo-controlled, comparative local anaesthetic diagnostic blocks as 12%. Hinderaker et al, 1995 (n=82) used double blind, comparative local-anaesthetic blocks of the cervical medial branches and the third occipital nerve to identify true-positive diagnoses of headache stemming from the second and third cervical vertebral segment (C2/C3). Hinderaker used these blocks to determine if abnormally located “instantaneous axes of rotation” of C2/C3 were a valid diagnostic test for headache stemming from there. There was no association between the two test results (chi-square, p=0.7), however the authors reported that the rotation test could not be carried out on a large number of participants.
Most studies on diagnostic cervical medial branch blocks were of high quality and were carried out by the same group of investigators.
The systematic review noted no reported complications in studies where diagnostic facet z-joint blocks were performed under fluoroscopy and with less than one millilitre local anaesthetic, with or without adjuvants. Participants did not complete trials in three studies due to vasovagal fainting or adverse reactions to lignocaine. In one study, participants reported troublesome, short-lived post-injection pain.