OUTLINE: Facet Denervation

INTRODUCTION Facet Denervation

It is accepted that the lumbar zygapophyseal joints (facet joints) are a potential source of low back and referred leg pain. However, as a clinical entity, facet syndrome remains ill-defined and hence the extent and significance of its contribution in disabling low back pain is a subject of ongoing debate. Nevertheless it is possible to identify, through diagnostic testing, a very select group of patients that can be successfully treated by percutaneous radiofrequency facet joint denervation.

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Whilst Goldthwait (1), in 1911, is credited as the first to recognise the lumbar facet joint as a potential source of back and leg pain, it was Ghormley (2), in 1933, who first coined the term "facet syndrome". However, their theories focussed more on the facet joint exerting mechanical pressure on nerves as the origin of symptoms.

Later, in 1971, Rees (3,4) published his work on "Multiple Bilateral Subcutaneous Rhizolysis…" where he reported a technique of denervation of the posterior spinal structures, including the facet joints, merely by the sweep of a Beaver blade and claimed apparently successful treatment in 998 out of 1000 consecutively treated patients. (We can only dream of such success!).

Following up on Rees’ work Shealy (5) initially experimented with Rees’ technique but encountered problems with haematomata in several patients which led him to the use of a radiofrequency lesioning device under fluoroscopy guidance. Mooney (7) was impressed by his observations of Shealy’s technique and was stimulated, along with Robertson (6), to undertake their important work in an attempt to provide more scientific evidence of the facet joint as a source of back pain. In their study, injection of the zygapophyseal joints in normal volunteers induced both back and referred leg pain and, moreover, they found that the pain could be obliterated by injection of local anaesthetic into the same joints.

Accordingly, the concept of the facet joint block as a diagnostic test was born. Since then there have been numerous studies exploring the utility of facet joint injections as both a diagnostic and therapeutic tool in the treatment of low back pain and it is fair to say that there have been widely varying results (8,9,10,11,12,13,14,15,16). Nevertheless injection of local anaesthetic into lumbar facet joints or at their nerve supply is accepted as a diagnostic test of facet joint pain and it was a natural progression to explore facet joint denervation procedures in the hope of providing longer lasting and perhaps permanent relief of facet joint pain (7,17,18,19,20,21,22,23,24,25,26). In order to refine techniques of facet joint denervation there was a renewed interest in anatomic studies to improve the understanding of innervation of lumbar spine structures and, in particular, to precisely map the afferent nerve supply of the facet joint (18,26,27,28,29,30).

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ANATOMY Facet Denervation

The major afferent nerve supply to the facet joint is provided by the medial branch of the posterior primary ramus. The medial branch descends from the posterior primary ramus over the base of the transverse process in a groove at the root of the superior articular process which is bridged by the mamillo-accessory ligament (Figure 1). The mamillo-accessory ligament is formed by a condensation of the intertransverse ligament fibres passing from the mamillary body to the transverse process and occasionally it is ossified. After passing under the bridge of the mamillo-accessory ligament the medial branch courses across the lamina deep to multifidus and finally enters the muscle. Deep to the muscle it sends fibres innervating the caudal portion of the facet joint immediately above before sending fibres to the facet joint below.

Paris (29) proposed a greater multiplicity in afferent supply to the facet joint. In particular, he described an ascending facet branch that passed to the posterior aspect of the facet joint one level above and throughout its course was entirely intramuscular and did not lie on any bony structures. He also suggested a more proximal origin of branches to multifidus and theorised that they would contain accessory afferent supply to the facet joints. However, this description of the anatomy, and in particular the ascending facet branch, could not be verified by Bogduk in his anatomical dissections (18,26,27,28,30). The existence of an intramuscular ascending facet joint branch would infer a "triple innervation" of the facet joints where a single medial branch supplies the adjacent facet joint and the joints above and below. However, there is more broad acceptance of the "dual innervation" as proposed by Bogduk where the medial branch supplies its adjacent facet joint and the joint immediately below. There is agreement throughout the literature that the medial branch of the posterior primary ramus is constant and is fixed adjacent to the bone in the region of the mamillo-accessory ligament. There is no evidence of nerve fibres crossing the midline so that facet joints on each side have a unilateral innervation.

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In the majority of cases the cause of lumbar facet joint pain is not known. Whilst facet joint osteoarthritis is a relatively common occurrence it is rare to find other definite recognisable pathology affecting the zygapophyseal joint such as systemic inflammatory arthropathy, facet joint fracture or infection (6,7,15,31,32,33,34). Exclusion of such disorders is important, leaving osteoarthritis which has been proposed as a cause of facet joint pain. Interestingly it has been demonstrated that facet joint degeneration almost invariably follows disc degeneration at the same level and, accordingly, degenerative changes within the facet joint rarely, if ever, exist in isolation (32,33,34). In spite of this, a study by Schwarzer (12), evaluating patients by provocative discography and facet joint blocks, concluded that it was rare to suffer symptomatic disc degeneration in combination with symptomatic facet joints.

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Whilst most clinicians recognise a clinical presentation which is presumed attributable to facet joint pain, there is no literature to support any pathognomonic historical, physical examination or imaging findings associated with lumbar facet joint syndrome (7,9,11,14,15,16,19,31). Typically, it is thought that facet joint pain is aggravated by rest in any posture and is relieved by movement. The pain may be unilateral or bilateral in the lower back with, or without, radiation to the lower limbs. Radiculopathy is absent and the pain should not radiate below the knee. Morning stiffness may be associated with a stooped posture on rising and lumbar extension is the movement most likely to aggravate symptoms. Despite the consistency of this description throughout the literature, clinical features have not proven to be predictive of the response to diagnostic facet joint blockade (13,14,15,16).

Facet joint injections form part of the investigative armamentarium when evaluating patients with non-radicular low back pain who have failed to respond to appropriate non-operative management, including an exercise programme, and in whom there are no sinister features of alternative underlying pathology. Lumbar facet joint injections, combined with the use of intra-articular corticosteroids, have been used as both a diagnostic and therapeutic modality. However, their use remains controversial (6,8,10,11,15). As a therapeutic option, some authors have found facet joint injections to be of no use whilst, at best, the injections may provide temporary relief of sufficient duration to allow resolution of symptoms by natural processes or through an appropriate rehabilitation programme.

A series of studies undertaken by Bogduk and associates have shown that targeted medial branch blockade is a valid diagnostic test in the evaluation of facet joint pain (12,13,16). Indeed, from a technical viewpoint , medial branch block is more easily performed than facet joint injections and there is less prospect of diffusion of the local anaesthetic to involve surrounding structures which may confound the response.

In addition, differential blocks undertaken on separate occasions using local anaesthetic agents with different pharmacological properties and durations of action have been able to exclude false positive results (13). Based on these studies, and others where the placebo response is controlled, facet joint pain is thought to have a prevalence of up to 40% in chronic non-radicular low back pain (14,15).

If facet joint pain is accepted as a significant contributor in disabling low back pain then it follows that facet joint denervation may provide long-term or even permanent relief of symptoms attributable to the facet joints. Facet joint denervation is appealing given the accessibility of the facet joint and, more particularly, the medial branch of the posterior primary ramus which has a constant course adjacent to an easily identifiable bony land-mark.

Bearing this in mind, when investigating a patient for consideration of radiofrequency denervation, it is logical that a medial branch block is a more appropriate diagnostic tool than facet joint block since it directly evaluates the structure that is scheduled for ablation.

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The original technique described by Shealy (5) targeted the electrode lateral to the mid-point of the facet joint and then swept the electrode in a cephalad and caudad direction so that there were three electrode positions for each joint covering the lateral aspect of the facet joint. In view of improved anatomic knowledge the following modified technique is recommended:-

Under sterile conditions with the patient laying prone over a pillow to reduce the lumbar lordosis, on a radiolucent operating table, the levels to be denervated are located by antero-posterior (AP) fluoroscopy. The target point (i.e. the base of the transverse process where it meets the root of the superior articular process) is marked on the skin (Figure 2). A puncture site is marked a centimetre or two lateral and caudal to the target point for the L1 to L4 levels. (The L5 level is treated differently owing to the different anatomy and is described below.) The lateral and caudal entry point is chosen to prevent deflection of the probe from the target at the base of the transverse process by the overhanging superior articular process and the bulging mamillary process. Since it has been shown that the uninsulated portion of the probe will produce a radial spread of the lesion that does not extend beyond the tip of the electrode, a more caudal approach is chosen to allow the introduced probe to lie nearly parallel to the target nerve so that the nerve is more likely to be encompassed by the radial spread of the lesion (35). The L5 dorsal ramus courses in the groove between the ala and the superior articular facet of S1 and can be approached in a more sagittal direction with the probe laying parallel to the dorsal primary ramus proper as it hooks over the sacrum. The intended puncture sites are anaesthetised using Lignocaine 1% down to the level of the deep fascia being careful not to anaesthetise deep around the facet joint which may interfere with nerve conduction and patient response.

An 11 Blade is used to puncture the skin prior to insertion of 3½ inch, 14 gauge Shiley needles with trocars under AP fluoroscopy. The Shiley needle is advanced until it is blocked by the base of the transverse process which obviates the need for lateral fluoroscopy to check the depth of placement. The trocar is removed and the blunt tipped electrode is introduced via the Shiley needle which can be used to steer the electrode. The transverse process is easily palpated and the electrode is then directed in a cephalad and medial direction so that it slips off the transverse process into the intertransverse space. The probe is then gradually withdrawn so that the uninsulated portion lies at the root of the superior articular process, more or less parallel to the course of the medial branch. At L5, as previously mentioned, the probe comes to lie in a more sagittal direction in the groove on the superior aspect of the ala, adjacent to the superior articular facet and is parallel to the posterior primary ramus proper. AP fluoroscopy is used to confirm the position of the tip of the electrode.

A stimulation mode can be used to confirm the electrode tip is properly positioned adjacent to the medial branch of the posterior primary ramus and away from the anterior primary ramus. At 2 hertz, motor stimulation may occur and if twitching of the lower limb muscles is observed then the probe should be withdrawn to a more posterior position. At 100 hertz, a sensory response is elicited in the posterior primary ramus which may produce pain or tingling similar to the presenting symptoms. However, the sensory response is not diagnostic and this step should not be necessary since the symptomatic levels would have been identified by prior medial branch blockade.

After satisfactory placement of the electrodes, lesions are made with a radiofrequency generator and typically the electrode tip temperature is raised to 80° Celsius for ninety seconds. During the production of the lesion the patient should be awake and co-operative in order to alert the surgeon as to the development of any radicular symptoms that would necessitate repositioning of the lesioning electrode. Usually the patient will experience an exacerbation of back pain that will reach a crescendo and then settle as the lesion is completed. Immediately post-operatively the neurological status is checked. The procedure is undertaken on an outpatient basis with minimal or no sedation and the patient is allowed to return to normal activity as symptoms permit.

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RESULTS Facet Denervation

Since the introduction of radiofrequency denervation of the facet joint by Shealy (5) the technique has been modified and used with varying results (7,17,18,19,20,21,22,23,24,25,26).

To date there have been only three randomised controlled trials (20,22,24) that have been published evaluating the effect of radiofrequency lumbar facet joint denervation in chronic low back pain. However, the studies are not directly comparable since they each used either different diagnostic criteria or different surgical technique.

Gallagher (20), in 1994, included 60 patients who were judged, on clinical grounds, to have symptoms of low back pain suggestive of facet joint origin. Forty-one patients reported improvement or were equivocal in their response following injection of local anaesthetic into and around the facet joints that were thought to be appropriate. Those patients were randomised to undergo either radiofrequency facet joint denervation or a sham procedure using the invalidated technique of Shealy. Nevertheless, improvement in symptoms was noted in patients who had a clear improvement following facet joint injections compared to patients who were equivocal in their response to the injections. The results were evaluated at one month and six months and were statistically significant.

van Kleef (22), in 1999, reported results in 31 patients with chronic low back pain selected on the basis of pain relief following diagnostic blockade of the medial branch of the posterior primary rami. The technique of lesion production was similar to the modified technique as described in the text above although the approach was more from a posterolateral oblique direction than the more caudal oblique approach as promoted by Bogduk (35). At least fifty percent pain relief following medial branch blockade was required to be eligible to enter the study and then patients were randomised to undergo either radiofrequency lesioning or a sham procedure. Interestingly, in the final analysis, the results were superior in patients that had reported complete relief of pain with diagnostic nerve blocks compared to those with only partial relief of pain. Statistical analysis at three, six and twelve months following treatment showed significant improvement in pain and functional disability in the treatment group.

Leclaire (24), in 2001, published results examining a larger sample size of 70 patients but a shorter follow-up of only three months and reported no significant improvement in the treatment group compared to the sham group. However, it is noteworthy that patients were included in the study based on their response to intra-articular facet joint injections rather than diagnostic medial branch blockade.

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Apart from transient radiculopathy and the report of a skin burn through poor earthing, there have been no serious complications associated with the procedure (5,19,20,21,22,23,24,25).

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CONCLUSION Facet Denervation

It is apparent that there exists a very select group of patients with disabling low back pain that can be attributed to the facet joints and may be successfully treated by facet joint denervation.

The careful use of diagnostic medial branch blockade is the critical factor in patient selection for facet joint denervation. Meticulous attention to detail through the use of differential medial branch blockade is required to accurately identify a highly selected group of patients that may respond to radiofrequency denervation. Following recommended protocols is a tedious process which may test the patience of the clinician (not to mention the patient) and may explain the paucity of high quality studies and the widely varying results published in the literature. Despite a plethora of literature dealing with anatomy and experimental studies, evaluating the facet joints as a potential source of pain, there is an extremely narrow evidence base of high quality clinical studies examining the utility of radiofrequency denervation of the facet joints. In particular, there is a single study (22) that employed the theoretical best practice methods of patient selection, accurate lesioning technique and rigorous scientific methodology which showed significant alleviation of pain and functional disability in a select group of patients both on a short and long-term basis following radiofrequency denervation.

There are many factors that may lead to failure of the technique including the technical adequacy of diagnosis by medial branch block and the adequacy of subsequent radiofrequency medial branch neurotomy. Additionally, there is always the question of alternate symptomatic pathology and, in particular, symptomatic disc degeneration since disc degeneration has been shown to always co-exist with facet joint degeneration. It has been postulated that late resurgence of symptoms may be associated with nerve regeneration in which case repeat procedures may be indicated after re-evaluation. Nevertheless, the minimally invasive technique of radiofrequency facet joint denervation is appealing given the accessibility of the medial branch of the posterior primary ramus and the reassurance that the reporting of complications from the procedure is virtually non-existent.

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REFERENCES: Facet Denervation

1. Goldthwait JE. The Lumbosacral Articulation. An explanation of many cases of "lumbago, sciatica and paraplegia". Boston Med Surg J, 1911;164:365-372.

2. Ghormley K. Low Back Pain with Special Reference to the Articular Facets, with presentation of an Operative Procedure. JAMA, 1933;101:1773-1777.

3. Rees WES. Multiple Bilateral Subcutaneous Rhizolysis of Segmental Nerves in the Treatment of the Intervertebral Disc Syndrome. Ann Gen Pract, 1971;16:126-127.

4. Rees WS. Multiple Bilateral Subcutaneous Rhizolysis. Med J Aus, 1975;1:536-537.

5. Shealy CN. Facet Denervation in the Management of Back and Sciatic Pain. Clin Orthop, 1976;115:157-164.

6. Mooney V, Robertson J. The Facet Syndrome. Clin Orthop, 1976;115:149-156.

7. Mooney V. Facet Syndrome. In: Weinstein J.N., Wiesel SW, ed. The Lumbar Spine: The International Society for the Study of the Lumbar Spine. Philadelphia: W.B. Saunders, 1990; 422-441.

8. Fairbank JCT, Park WM, McCall IW, et al. Apophyseal Injection of Local Anaesthetic as a Diagnostic Aid in Primary Low-Back Pain Syndromes. Spine, 1981;6:598-605.

9. Lewinnek GE, Warfield CA. Facet Joint Degeneration as a cause of Low Back Pain. Clin Orthop, 1986; 213: 216-222.

10. Lilius G, Laasonen, EM, Myllynen P, et al. Lumbar Facet Joint Syndrome. J Bone Joint Surg (Br), 1998;71-B:681-684.

11. Jackson RP. The Facet Syndrome: Myth or Reality? Clin Orthop, 1992;279:110-121.

12. Schwarzer A, Aprill CN, Derby R, et al. The Relative Contributions of the Disc and the Zygapophyseal Joint in Chronic Low Back Pain. Spine, 1994;19:801-806.

13. Schwarzer AC, Aprill CN, Derby R, et al. The false-positive rate of uncontrolled diagnostic blocks of the lumbar zygapophyseal joints. Pain, 1994;58:195-200.

14. Schwarzer A, Wang S, Bogduk N, et al. Prevalence and clinical features of lumbar zygapophyseal joint pain: a study in an Australian population with chronic low back pain. Ann Rheum Dis, 1995;54:100-106.

15. Dreyfuss PH, Dreyer SJ, Herring SA. Contemporary Concepts in Spine Care: Lumbar Zygapophysial (Facet) Joint Injections. Spine, 1995;20:2040-2047.

16. Kaplan M, Dreyfuss P, Halbrook B, et al. The Ability of Lumbar Medial Branch Blocks to Anesthetize the Zygapophysial Joint: A Physiologic Challenge. Spine, 1998;23:1847-1852.

17. McCulloch JA, Organ LW. Percutaneous radiofrequency lumbar rhizolysis (rhizotomy). Can Med Assoc J, 1977;116:30-32.

18. Bogduk N, Long DM. The Anatomy of the so-called "articular nerves" and their relationship to facet denervation in the treatment of low back pain. J Neurosurg, 1979;51:172-177.

19. Rashbaum RF. Radiofrequency Facet Denervation: A treatment alternative in Refractory Low Back Pain with or without Leg Pain. Orthop Clin North Am, 1983;14:569-575.

20. Gallagher J, Di Vadi PLP, Wedley JR, et al. Radiofrequency facet joint denervation in the treatment of low back pain: a prospective controlled double-blind study to assess its efficacy. The Pain Clinic, 1994;7:193-198.

21. North RB, Han M, Zahurak M, et al. Radiofrequency lumbar facet denervation: analysis of prognostic factors. Pain, 1994;57:77-83.

22. van Kleef M, Barendse GAM, Kessels A, et al. Randomized Trial of Radiofrequency Lumbar Facet Denervation for Chronic Low Back Pain. Spine, 1999;24:1937-1942.

23. Tzaan WC, Tasker RR. Percutaneous Radiofrequency Facet Rhizotomy – Experience with 118 Procedures and Reappraisal of its Value. Can J Neurol Sci, 2000;27:125-130.

24. Leclaire MD, Fortin L, Lambert R, et al. Radiofrequency Facet Joint Denervation in the Treatment of Low Back Pain. Spine, 2001;26:1411-1417.

25. Geurts JW, van Wijk, RM, Stolker, RJ, et al. Efficacy of Radiofrequency Procedures for the Treatment of Spinal Pain: A Systematic Review of Randomized Clinical Trials. Reg Anesth Pain Med, 2001;26:394-400.

26. Bogduk N, Long DM. Percutaneous Lumbar Medial Branch Neurotomy: A Modification of Facet Denervation. Spine, 1980;5:193-200.

27. Bogduk N, Wilson AS, Tynan W. The human lumbar dorsal rami. J Anat, 1982;134:383-397.

28. Bogduk N. The Innervation of the Lumbar Spine. Spine, 1983;8:286-293.

29. Paris SV. Anatomy as Related to Function and Pain. Orthop Clin North Am, 1983; 14: 475-489.

30. Bogduk N, Twomey LT. Clinical Anatomy of the Lumbar Spine. London: Churchill Livingstone, 1997.

31. Eisenstein SM, Parry CR. The Lumbar Facet Arthrosis Syndrome: Clinical Presentation and Articular Surface Changes. J Bone Joint Surg (Br), 1987;69:3-7.

32. Fujiwara A, Tamai K, Yamato N, et al. The Relationship between Facet Joint Osteoarthritis and Disc Degeneration of the Lumbar Spine: An MRI Study. Eur Spine J, 1999;8:396-401.

33. Butler D, Trafinow JH, Andersson GBJ, et al. Disc degenerate before Facets. Spine, 1990;15:111-113.

34. Vernon-Roberts B, Pirie CJ. Degenerative Changes in the Intervertebral Discs of the Lumbar Spine and their Sequelae. Rheum Rehab, 1977;16:13-21.

35. Bogduk N, Macintosh J, Marsland A. Technical Limitations to the Efficacy of Radiofrequency Neurotomy for Spinal Pain. Neurosurgery, 1987;20:529-535.

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Figure 1 Facet Denervation

Fig 1 – A sketch of a dorsal view of the branches of the left lumbar dorsal rami. Mamillo-accessory ligaments (mal) have been left insitu covering the L1 and L2 medial branches. ZJ zygapophyseal joint, m medial branch, lb lateral branch, ib intermediate branch, ibp intermediate branch plexus, is interspinous branch, a articular branches. (Reprinted from Bogduk N. The Innervation of the Lumbar Spine. Spine, 1983; pg. 289).

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Figure 2 Facet Denervation

Fig 2 - Anteroposterior radiograph of lumbar spine illustrating target points for medial branch neurotomy. The target points lie exactly at the tip of either the arrows at L1, L2 and L5, or the guide needles at L3 and L4. Note, at the L3 and L4 levels, how the silhouette of the superior articular process overlaps the target point, demonstrating why electrodes should be introduced obliquely. The overhanging superior articular process protects the target point in a dorsoventral approach. The guide needles are indicating the target points, however, a more caudal entry point is now recommended in order to allow introduction of the electrode more or less parallel to the respective medial branches at L4 and above. On the right side of the figure the courses of the medial branches of the dorsal rami have been superimposed. (Reprinted from Bogduk N, Long DM. Percutaneous Lumbar Medial Branch Neurotomy: A modification of Facet Denervation. Spine, 1980;5:pg.196).

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Last modified: November 10, 2003