LETTERS TO THE EDITOR

ARTHROGENIC PAIN

To the Editor:It was interesting to read the technical communica-

tion titled “Intra-articular Application of PulsedRadiofrequency for Arthrogenic Pain—Report of SixCases.”1 The authors start with the introduction thatinvasive treatment of chronic pain emanating fromjoints is often difficult because of the complexanatomy of the nerve supply. However, they lump inspinal facet joints, which includes cervical facet jointsand atlanto-axial joints in the shoulder. They failed toexplain the mechanism of action of intra-articularapplication of pulsed radiofrequency, either in cervicalfacet joints, the atlanto-axial joint, knee joints, thesacroiliac joint, or the shoulder. If we understandcorrectly, the needle is positioned in at one place inthe joint and then a pulsed radiofrequency of 45 V isapplied for 10 minutes. This fails to explain themechanism of action. It needs to be clarified if themechanism of pulsed radiofrequency is denervation ofthe nerve supply or the heating of the joint. If the den-ervation of the nerve supply is the mechanism, thereaders are very much interested in knowing how den-ervation can be achieved by placing the needle in oneplace. Further, the authors have used pulsed radiofre-quency for 10 minutes in the cervical facet joint, kneejoint, sacroiliac joint, radiocarpal joint; whereas, forshoulder and atlanto-axial joint, 8 minutes of pulsedradiofrequency was utilized. Even though there wasvariation in the voltage, this does not explain therationale of 40 V applied for 8 minutes in the shoulderand 45 V applied for 10 minutes in cervical facet joint.

Overall, even though this is a technical report, it hassubstantial consequences on interventional pain man-agement with potential abuse of the technology. At thepresent time, pulsed radiofrequency is considered asexperimental even for medial branch nerves and otherperipheral nerves.

Laxmaiah Manchikanti, MDPain Management Center of Paducah, Paducah KY

E-mail: drlm@thepainmd.com

Vijay Singh, MDPain Diagnostic Associates, Niagara WI 54151, U.S.A.

E-mail: vj@wmpnet.net

REFERENCE

1. Sluijter ME, Teixeira A, Serra V, Valgo S, SchianchiP. Intra-articular application of pulsed radiofrequency forarthrogenic pain—Report of six cases. Pain Pract. 2008;8:57–61.

Editorial note:While the experimental nature of the technical report

was already stated in the cited article, we are grateful toDrs Manchikanti and Singh for providing the opportu-nity to emphasize this point. CTH

Reply to Drs. Manchikanti and Singh:We thank Dr. Manchikanti for his interest in our

article.1 As for the mode of action of pulsed radiofre-quency (PRF) in this procedure, we have tried to explainour views in the discussion part of the article. At nopoint have we suggested that any form of denervationcould be involved, and this is of course quite obvious.The mean tip temperature stays well within limits, espe-cially when a pulse width of 10 milliseconds is used.Thermal fields during heat spikes and electric fields onlyreach potentially destructive levels in very close prox-imity (<0.1 mm) to the electrode. Denervation––or,more explicitly, damage––can therefore be excluded asan explanation.

We find this a positive development, because it bringsclarity. When PRF was introduced it was suggested thatthis was a nondestructive method. We now know thatthis is not true. There is a mild degree of destruction,2

probably because of either heat spikes or strong electricfields during the pulse.3 It has been suggested that this“mini-destruction” might play a role in the mode ofaction of PRF. This view cannot be held if intra-articularPRF is effective.

We therefore have to turn elsewhere to find the modeof action. The two systems that govern pain processesare the nervous system and the immune system. Thesesystems are intimately related, up to the point that anaction on one system implies a sequence in the

© 2008 World Institute of Pain, 1530-7085/08/$15.00Pain Practice, Volume 8, Issue 3, 2008 217–219

other. The choice is therefore which system PRF prima-rily affects somehow. If intra-articular PRF is effective,this strongly points to the immune system, because it ishard to see how the nerve endings in a larger joint couldrespond in any way to such weak electric fields. This allsuggests that PRF is an entity of its own, working in away that is entirely different from continuous RF.

As written in the discussion of our article, it is ourworking hypothesis that PRF has an anti-inflammatoryeffect on the immune system. There are relatively simplemethods available to verify this. We are presentlyengaged in these investigations. The first data are con-cordant with the hypothesis but we need time for aformal study. If the hypothesis is confirmed, a number ofobservations fall into place. It could then be understoodhow PRF could be effective in neuropathic pain, becauseneuropathic pain is in fact an inflammatory process.4 Itcould also be understood how PRF could work forradicular pain because of a herniated disk5 and for dis-cogenic pain.6

We find all this a challenge rather than a problem.This contrasts sharply with the tone of Dr Manchikan-ti’s letter. Let us make it perfectly clear that this is not apersonal reproach, but we wish to discuss this matterbecause we are under the impression that his lettervoices the attitude of a larger group of colleagues.Maybe the roots of this contrast must be seen in ahistorical perspective. The older generations ofdoctors––who are now the teachers––have been raisedin a period when the nervous system was implicitlysovereign in matters of symptomatic treatment of pain.Until the late seventies the role of the immune systemwas nonexistent, as creation was perfect and whateverthe immune system did was good for us.

We now know that this was a costly error. When wecut a nerve, the immune system responds with inflam-mation. This is why ablative methods have––with fewexceptions, such as the medial branch––regularly endedup in disaster. We also know that a malfunctioningimmune system––which has a considerable prevalence––may prevent a favorable outcome of surgery.7 We knowthese things, but appropriate action is surprisingly slow.It seems that we sometimes have an overly activehomeostasis.

As for PRF, for old time’s sake it hurts to associateradiofrequency with anything else than railroad tracksand ablation. Or, to stay in the terminology, it gives tosome of us the uncomfortable feeling of allostasis: thebelly feeling that something is not right. We proposethat the time has come to form a united front in the

interest of the patient, recognizing that there are twoseparate methods of applying radiofrequency with adifferent mode of action, each with its own potentialand drawbacks.

We do not share Dr. Manchikanti’s worries about thepotential abuse of technology. It would be different ifthe method could predictably have adverse effects, bytemperature effects or by compromising innervation.This, however, is not the case. It could be argued forexample that a generally accepted method such as anintra-articular steroid injection is more consequential.We have a high opinion of the intelligence of the reader,and we are confident that any colleague who wants tocopy this technique will be as careful and as reticent aswe have been in the initial phase.

Menno E. Sluijter, MD, PhD, FIPPInstitute for Anesthesiology and Pain Clinic, Swiss

Paraplegic Center, Nottwil, SwitzerlandE-mail: sluijterm@aol.com

Alexandre Teixeira, MD, FIPPClinica de Dor, Porto, Portugal

E-mail: alteix@iol.ptVicente Serra, MD

Umivale (MATEPPS nr 15), Valencia, SpainE-mail: vserra@arrakis.es

Susan Balogh, MDInstitute for Anesthesiology and Pain Clinic, Swiss

Paraplegic Center, Nottwil, SwitzerlandE-mail: Susan.Balogh@paranet.ch

Pietro Schianchi, MD, FIPPSt. Anna Hospital, Lugano, Switzerland

E-mail: p.schianchi@bluewin.ch

REFERENCES

1. Sluijter ME, Teixeira A, Serra V, Balogh S, SchianchiP. Intra-articular application of pulsed radiofrequency forarthrogenic pain—Report of six cases. Pain Pract. 2008;8:57–61.

2. Erdine S, Yucel A, Cunen A, Aydin S, Say A, Bilir A.Effects of pulsed versus conventional radiofrequency currenton rabbit dorsal root ganglion morphology. Eur J Pain.2005;9:251–256.

3. Cosman ER Jr, Cosman ER Sr. Electric and thermalfield effects in tissue around radiofrequency electrodes. PainMed. 2005;6:405–424.

4. Watkins LR, Maier SF. Immune regulation of centralnervous system functions: from sickness responses to patho-logical pain. J Int Med. 2005;257:139–155.

218 • letters to the editor

5. Teixeira A, Grandinson M, Sluijter ME. Pulsedradiofrequency for radicular pain due to a herniated interver-tebral disc––an initial report. Pain Pract. 2005;5:111–115.

6. Teixeira A, Sluijter ME. Intradiscal high-voltage,long-duration pulsed radiofrequency for discogenic pain: apreliminary report. Pain Med. 2006;7:424–428.

7. Geiss A, Rohleder N, Kirschbaum C, Steinbach K,Bauer HW, Anton F. Predicting the failure of disc surgery bya hypofunctional HPA axis: evidence from a prospectivestudy on patients undergoing disc surgery. Pain. 2005;114:104–117.

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