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Radio-Frequency Facet Nerve Blocks
Lumbar
  History  
In the latter third of the 20th century the modern specialty of spine care first began to  take shape.  A number of concepts and associated procedures were developed along the way.  Some have not successfully withstood the test of time but others have remained in the treatment armamentarium because of their well-demonstrated continuum of safety and efficacy.  In time all procedures become more refined and sophisticated and that has also been the story here. The chronicle of how facet injections,  medial branch blocks and radio-frequency facet nerve blocks came to be is a particularly intriguing tale known to but to few. 

It is interesting to observe that the number of radio-frequency and coagulative procedures in general (as reflected by minimally invasive spine procedures, treatment of prostate cancer and other tumors, and even therapy for varicose veins utilizing liquid microparticles) have greatly increased in recent years reflecting the increasing importance of minimally invasive procedures and interventional radiology. 
 
  History   
The modern era of interest in the facet (zygoapophyseal) joints came about when clinicians began to recognize that these structures, when associated with disc degeneration, were important sources of pain and resulting disability in patients.  It appears that Joel Goldthwait was the first to recognize this connection in 1911 (The Lumbosacral Articulation: an explanation of many cases of 'lumbago,' 'sciatica,' and 'paraplegia.'" Boston Medical Surgical Journal 1911) followed soon after by Ralph Ghormley  in 1933 (Low Back Pain with Special Reference to the Articular Facets, with Presentation of An Operative Procedure." Journal of American Medical Association 1933). 

The credit for the first anatomic studies performed on the nervous system innervation of these facet joints goes to Professor Guy Lazorthes and associates, beginning in the 1950s (Lazorthes G, Gaubert J: L'innervation des articulations interapophysaires vertebrales, Comp Rend Assoc Anat 43:488-494, 1956).  Because his works were published in French journals a number of decades passed before his contributions were appreciated by the English speaking medical world.  The later work of Drs. Stanley Paris , Nikolai Bogduk, and others in the 1980s served to complement the original work of Lazorthes and to build a scientific basis for our present understanding and associated treatment of  the "facet syndrome" as an important contributor to the etiology of low back pain in the world's population.  
              
Stanley Paris is shown above studying the dorsal root complex of a cadaver.  In the drawing at right the green dot is on the dorsal ramus of the emerging dorsal nerve root ganglion.  The yellow dot shows the point at which this ramus breaks up into numerous small branches.  These branches innervate the facet.  The medial branch of this complex is the typical target for medial branch injections and permanent radio-frequency (RF) blocks.
The making of sense in regard to all of this information from the anatomic and pathologic standpoint fell to Professor William Kilkaldy-Willis of the University of Saskatoon, Saskatchewan, Canada who, on the basis of his personal research (Kirkaldy-Willis W et al. Pathology and Pathogenesis of Lumbar Spondylosis and Stenosis, Spine, Vol 3, No. 4, pp. 318-328, 1978) during the 1970s initiated the concept of  the "degenerative cascade".  Kirkaldy-Willis' anatomic studies were soon confirmed by radiologists and clinicians who could then begin to visualize these same entities on computed tomographic scans (CT) and then on magnetic resonant imaging (MRI) studies.
In the first of the illustrations above the arrows point to areas of the articular facet joint which have eroded, produced diastasis, and have  resulted in joint dysfunction as shown on a CT scan.  In the second image the arrow points to a similar area of erosion in a pathologic specimen provided by Professor Kirkaldy-Willis.  The third image also shows facet joints with more advanced degenerative change which has created a degenerative spondylolisthesis due to acquired incompetence of these joints.  More advanced facet degeneration was then appreciated and associated with lateral spinal stenosis, the most common reason for creation of the "failed back surgery syndrome".

In the late 1960s an Australian surgeon, W. E. Skyrmer Rees, first introduced the concept of treating low back pain emanating from the facet joints by surgically incising the intertransverse ligament with a scalpel in order to section the dorsal ramus as a means of producing sensory blockade and thus relieving back pain secondary to what has become called the "facet syndrome".  The illustration shown below was drawn by Rees, in 1971, to illustrate how a "Beaver Eye Knife" was utilized to surgically section this intertransverse ligament and the dorsal ramus of the postganglionic segment of the spinal nerve.
Rees referred to his procedure as "dorsal root rhizolysis" and usually performed it on both sides.  Following publication of his work in the 1975 Medical Journal of Australia American neurosurgeon C. Norman Shealy visited Rees in Australia.
Shealy observed Rees' procedures, and returned to the United States where he performed rhizolysis on a number of his own patients.  He concluded that while the procedure seemed to have merit it was not minimally invasive and often produced significant subcutaneous hematomas.  Shealy's previous experience with radio-frequency coagulating electrodes used to treat trigeminal neuralgia and intractable pain with cordotomy led him to replace the Beaver scalpel with a radiofrequency probe.  
It remained for some of Shealy's neurosurgical colleagues to further refine this clinically valuable technique . A significant improvement was achieved when Charles Ray (seen below), designed a combination trocar/ probe electrode.  At about this time, based on  the anatomic studies of Paris and Bogduk, it became evident that a that a much more selective procedure could be performed by producing a blockade of the medial branch of the dorsal nerve ramus at the base of the transverse process (providing a definitive and safe bony end-point).
In addition to this by replacing the previous need for of general anesthesia with "monitored anesthetic control" using local anesthesia and narcotic supplementation (i.e. Fentanyl and  Versed) percutaneous radio-frequency facet blocks then became a safer and more patient-friendly procedure.  
Shown above is a radiofrequency procedure in progress.  The Ray electrode (or other RF electrodes) are inserted percutaneously under fluoroscopic control and directed to the base of each transverse process, where a monitored RF lesion is produced.
The illustration to the left demonstrates the target areas for placement of the radiofrequency probe. Thermocoagulation occurs in a cylindrical area around the probe tip. 
The reason for lesion production at multiple sites is that the sensory input system is similar to a spider's web and the goal is not to destroy the system but to block some of the "strands" to simply cut down on the sensitivity of the system's response.  

Initial dire predictions that RF lesioning would produce "Charcot" joints (total denervation of a joint sometimes seen with syphilis or diabetes).  This phenomenon was initially described by Jean-Martin Charcot, 1825-1893, Professor of Neurology at the University of Paris) and fortunately there has been no evidence, over time, that this occurs.  Other dire predictions regarding significant denervation of the multifidus muscles have also not been borne out.  What has become evident that partial dennervation of the facets decreases the sensitivity of the A-Delta and C fiber facet "alarm system" thus decreasing patient pain and associated spasm relating to facet dysfunction causing low back pain and frequently providing the patient with meaningful relief of low back pain while also providing them with a "window of opportunity" to start daily, self-administered, health maintenance programs.
  The Burton Experience  
The Burton Experience with percutaneous radio-frequency facet blocks began in the early 1972 when the Editor invited Norman Shealy to give a presentation on "Articular Nerve of Luschka, Rhizotomy for Back and Leg Pain" at Temple University Health Sciences Center in Philadelphia.  The term "Luschka" referred to German Anatomist Herbert von Luschka (1820-1875) who studied and described the uncovertebral joint. This usage became synonymous with the the term "zygoapophyseal joint." 

Following this symposium a Joint Study Group consisting of Drs. Shealy, Prieto, Burton, and Long  initiated an interinstutional trial of this procedure.  These clinical results were presented at the annual meeting of the American Association of Neurological Surgeons in Los Angeles in 1973.  In the Burton series the overall long-term procedure efficacy(3 year follow-up) was 67% (Burton CV: Percutaneous Radiofrequency Facet Denervation, Applied Neurophysiology, 39:80-86, 1977) and it is interesting to note that even today this same efficacy determination has continued, unchanged,  in the Editor's clinical practice.  

Radiofrequency facet blocks are now, after over 30 years of clinical application, considered to be "well established" by the world spine specialist community.  They have, on the basis of a large population of clinical use, proven to be a valid and important, minimally invasive, low risk procedure for the well-selected patient with a "facet syndrome" when applied by experienced physicians using x-ray control. 

In a prime example of one of the great examples of perversity in our health care system many procedures such as lumbar radiofrequency facet blocks have been denied for third party payor coverage as being "experimental or investigational" based on the fact that double blinded and controlled studies weren't done over the two scores of time ending the 20th century:
This would mean that this insurance company would not cover appendectomy for appendicitis for the same reason.  Remarkably,  Nath et al actually performed  a randomized controlled study to confirm efficacy which was published in the Journal Spine in 2008 (Nath et al, Percutaneous Lumbar Zygoapophyseal (Facet) Joint Neurotomy Using Radiofrequency Current, in the Management of Chronic Low Back Pain, Spine, Vol. 33, No. 12, pp. 1291-1297, 2008).

It is not unusual for patients to experience continued pain relief for many years following percutaneous RF Facet blocks.  Good results for as long as 20 years are known by the Editor.  Key to maintaining this is not to be a smoker and be in a daily self-administered health care program.  Repeat blocks are rarely needed.  The representation that this is something which needs to be repeated, on a regular basis, throughout a patient's life, is the stuff of fantasy and suggests a professional motivation not in concert with the patient's best interests. 
 
For the right patient, and if performed by the right specialist for the right reasons, radiofrequency facet blocks, in the lumbar area, have been a successful endeavor and have been an important contribution to the spine care armamentarium, particularly when used in conjunction with other conservative therapies.  Because of this long-term positive experience spine specialists now routinely perform diagnostic and therapeutic facet blocks in the thoracic and cervical areas.

Dorsal Root Rhizolysis and Dorsal Root Rhizotomy-  When Australian surgeon, W. E. Skyrmer Rees, first introduced the concept of treating low back pain emanating from the facet joints he actually intended to completely sever the dorsal nerve root with a scalpel.  He was the one, in the 1960s to coin the term "dorsal root rhizolysis", which a correct description of what he was attempting to do.  The Latin "Rhiz" is translated "root", referring to nerve root (i.e. dorsal nerve root) and "lysis" means "to cut".  The term "otomy" is a bit more complex because it is used, in present medical lingo, to mean "to open".  However,  "otomy" derives from the Greek work "tome"  meaning "to cut" and we are therefor back to meaning surgical division of of some or all the fibers of a nerve; not a minimally invasive percutaneous coagulation of small nerve fibers. 

Articular Nerve of Luschka Rhizolysis- Term used by Shealy to describe his modification of the Rees procedure.  Rhizolysis is a misnomer and von Luschka never described a nerve associated with the uncovertebral joint.

Percutaneous Radiofrequency Facet Denervation-  Term used originally by Burton in the 1970s to describe partial denervation of the facet joints.

Percutaneous Radio-Frequency Facet Nerve Blocks (PRFFNB)- Term used by Burton and associates in Minneapolis from 1981 to the present.  Although unwieldy, this verbage is correct.  Percutaneous Radiofrequency medial branch nerve block is more specific and also correct.