efficacy and safety of pulsed radiofrequency as a method ... · it has been suggested that a dorsal...

RESEARCH ARTICLE Open Access

Efficacy and safety of pulsedradiofrequency as a method of dorsal rootganglia stimulation for treatment of non-neuropathic pain: a systematic reviewIvana Vuka1, Svjetlana Došenović2, Tihana Marciuš1, Lejla Ferhatović Hamzić3, Katarina Vučić4,Damir Sapunar1,5† and Livia Puljak5*†

Abstract

Background: We systematically reviewed the evidence on the efficacy and safety of dorsal root ganglion (DRG)targeted pulsed radiofrequency (PRF) versus any comparator for treatment of non-neuropathic pain.

Methods: We searched MEDLINE, CINAHL, Embase, PsycINFO, clinicaltrials.gov and WHO clinical trial register untilJanuary 8, 2019. All study designs were eligible. Two authors independently conducted literature screening. Primaryoutcomes were pain intensity and serious adverse events (SAEs). Secondary outcomes were any other pain-relatedoutcome and any other safety outcome that was reported. We assessed the risk of bias using the Cochrane tooland Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I). We conducted narrative evidence synthesisand assessed the conclusiveness of included studies regarding efficacy and safety.

Results: We included 17 studies with 599 participants, which analyzed various pain syndromes. Two studies wererandomized controlled trials; both included participants with low back pain (LBP). Non-randomized studies includedpatients with the following indications: LBP, postsurgical pain, pain associated with herpes zoster, cervicogenicheadache, complex regional pain syndrome type 1, intractable vertebral metastatic pain, chronic scrotal andinguinal pain, occipital radiating pain in rheumatoid arthritis and chronic migraine. In these studies, the PRF wasusually initiated after other treatments have failed. Eleven studies had positive conclusive statements (11/17) aboutefficacy; the remaining had positive inconclusive statements. Only three studies provided conclusiveness ofevidence statements regarding safety – two indicated that the evidence was positive conclusive, and one positiveinconclusive. The risk of bias was predominantly unclear in randomized and serious in non-randomized studies.

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* Correspondence: [email protected]; [email protected]†Damir Sapunar and Livia Puljak contributed equally to this work.5Center for Evidence-Based Medicine and Health Care, Catholic University ofCroatia, Ilica 242, 10000 Zagreb, CroatiaFull list of author information is available at the end of the article

Vuka et al. BMC Anesthesiology (2020) 20:105 https://doi.org/10.1186/s12871-020-01023-9

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Conclusion: Poor quality and few participants characterize evidence about benefits and harms of DRG PRF inpatients with non-neuropathic pain. Results from available studies should only be considered preliminary. Not allstudies have reported data regarding the safety of the intervention, but those that did, indicate that theintervention is relatively safe. As the procedure is non-destructive and early results are promising, furthercomparative studies about PRF in non-neuropathic pain syndromes would be welcomed.

Keywords: Chronic pain, Non-neuropathic pain, Pulsed radiofrequency, Dorsal root ganglion

BackgroundChronic pain is one of the major public health issuesworldwide and is one of the leading causes of years livedwith disability [1]. Estimates on the prevalence ofchronic pain in the general population vary, rangingfrom 11% [2] up to 64% [3]. These different estimatesare mostly due to differences in the definition of chronicpain regarding the duration of symptoms (3 vs. 6months) and the wording of questions used for assessingchronic pain [4]. Besides its major clinical impact andcosts for the healthcare system, chronic pain impairs pa-tients’ quality of life, as well as their ability to work andfunction, causing massive indirect socioeconomic costsworldwide [5]. Chronic pain asserts this major impacton individuals, health systems and society because of in-adequate treatment modalities.Pulsed radiofrequency (PRF) emerged as a therapeutic

treatment for various painful conditions, including bothneuropathic and non-neuropathic pain [6–8]. PRF hasbeen described as “a non-neurodestructive therapy inpain management ”[9]. PRF is a minimally invasive inter-vention, which involves the application of pulses of elec-tric current, created at the tip of an electrode, without aharmful increase in the temperature [9].It has been suggested that a dorsal root ganglion

(DRG) is a desirable target for the treatment of pain[10]. PRF application close to dorsal root could alleviateneuropathic pain [11]. However, we have observed an in-creasing number of studies on chronic pain, reportinguse of DRG targeted PRF treatment of non-neuropathicpain in humans. Therefore, we aimed to conduct a sys-tematic review about the evidence on the efficacy andsafety of DRG targeted PRF treatment of non-neuropathic pain.

MethodsStudy designWe published a systematic review protocol a priori inthe PROSPERO database (registration number:CRD42017076502). Since the original protocol coveredextremely wide scope and heterogeneous interventions,subsequently we divided the original protocol into a separ-ate assessment of DRG targeted electrical field stimulation(EFS) [12] and PRF. The systematic review was performed

following the PRISMA statement and Center for Reviewsand Dissemination (CRD) manuals.

Eligibility criteriaParticipants, intervention and study designsWe included primary studies with participants sufferingfrom various painful conditions which are not currentlyclassified as purely of neuropathic origin (i.e. non-neuropathic pain). In case that condition was defined ofboth origins, neuropathic and non-neuropathic, such aspost-surgical pain or low back pain we included suchcondition. We excluded studies where PRF treatmentwas used for neuropathic pain as it is defined in theguidelines of the International Association for the Studyof Pain (IASP). We used the IASP classification ofchronic pain for ICD-11. We chose to include both ran-domized controlled trials (RCTs) as well as non-randomized study designs (NRSDs) because we expecteda few RCTs in this research area, and we wanted to pro-vide a comprehensive picture of evidence in this field ofresearch. We used Cochrane Handbook for Reviews ofInterventions to define the design of included studies.Manuscripts that included more than 10 participantswere classified as case series, while those that includedless than 10 participants were defined as case reports[13]. We only included studies where PRF treatment wasdirected to the DRG, including a combination of PRFwith other therapies. If the study only reported resultsabout efficacy, and safety was not reported, we still in-cluded such a study to get comprehensive evidence syn-thesis regarding efficacy.

Outcome measuresPrimary outcomes were: pain intensity and serious ad-verse events (SAEs). For primary outcome, we reportedany outcome measures, as reported in included manu-scripts. Secondary outcomes for efficacy were any otherpain-related outcomes, and for safety any other safetydata, including non-serious adverse events and othercomplications regarding tested intervention.

Search strategy and information sourceWe searched four databases: MEDLINE via Ovid,Embase via Ovid, CINAHL and PsycINFO via

Vuka et al. BMC Anesthesiology (2020) 20:105 of 21

EBSCOhost (Supplementary Table 1). Databases weresearched from the date of inception until January 8,2019 with no restriction regarding the language. Re-cords were then exported to the EndNote X5 citationsoftware (Clarivate Analytics, Boston, MA, USA) andduplicates removed. Furthermore, reference lists of allincluded studies and their citations were downloadedfrom Web of Science and screened to find additionaleligible studies. ClinicalTrials.gov and World HealthOrganization’s International Clinical Trial Registry Plat-form (WHO ICTRP) were searched to identify ongoingstudies.

Study selectionReviewers independently screened each title/abstract ofretrieved records as well as full-texts of retrieved studiesfor possible inclusion (authors LFH, IV, TM and SD par-ticipated in screening). Discrepancies were resolved byanother author (DS).

Data extractionIndependent data extraction was performed by two au-thors for each data point (authors: IV, and TM or KV).We extracted the following data: the surname of the firstauthor, year of publication, study design, details aboutintervention (treatment protocol and device used), com-parator, inclusion and exclusion criteria, number of par-ticipants, baseline characteristics of participants, follow-up period, DRG level treated and outcomes about effi-cacy and safety.

Risk of bias assessmentWe used the Cochrane Risk of Bias (RoB) tool (versionfrom 2011) to assess RoB in RCTs and the Risk of BiasIn Non-randomized Studies of Interventions (ROBINS-I)tool for cohort type studies. RoB was analyzed independ-ently by two authors (IV, and SD or KV). Discrepancieswere resolved by another author (LP).

Synthesis of resultsDue to the heterogeneity of included studies, it was notpossible to conduct a meta-analysis, even though wehave planned to do it in our study protocol. For this rea-son, we conducted a narrative and tabular synthesis ofresults. We also conducted an analysis of conclusivenessabout efficacy and safety of the treatment in the ab-stracts of included studies. We divided conclusivenessstatements into five categories: positive conclusive (fa-vorable conclusion in favor of PRF), positive inconclu-sive (favorable conclusion, but with a note aboutinsufficient or low quality evidence), negative conclusive(PRF not beneficial), negative inconclusive (PRF notbeneficial, but with a note about insufficient or low qual-ity evidence) and not reported.

ResultsThe flow chart in Fig. 1 shows the number of recordsanalyzed in each screening phase. We screened 63 man-uscripts in full text, and we finally included 17 manu-scripts in this systematic review. Excluded studies, andreasons for their exclusion, are listed in SupplementaryTable 2. The characteristics of the included studies aredetailed in Table 1.Among 17 included studies there were two randomized

controlled trials [14, 15] and 15 non-randomized studies(Table 1). The total number of participants in these stud-ies was 599; the median number of participants was 28(range: 1 to 127) (Table 1). Both RCTs included partici-pants with low back pain (LBP) [14, 15]. Non-randomizedstudies included patients with the following indications:LBP [16–18], postsurgical pain [19–21], pain associatedwith herpes zoster [6], cervicogenic headache [22, 23],complex regional pain syndrome type 1 [24, 25], intract-able vertebral metastatic pain [26], chronic scrotal and in-guinal pain [27], occipital radiating pain in rheumatoidarthritis [28] and chronic migraine [29] (Table 1). Thesestudies had highly heterogeneous parameters of stimula-tion (Table 2). Detailed information about inclusion andexclusion criteria, as well as baseline characteristics of in-cluded participants, are listed in Table 3.

Low back painIn this group, there were 5 studies with a total of 328participants, including two RCTs with 28 participants inone [14] and 60 participants in another one [15], oneretrospective cohort study including 29 participants [16],and two before and after comparisons with 84 partici-pants in one [17] and 127 participants in another [18].Trial by Holanda et al. [14] included 28 participants

which were randomized in three groups: PRF treatmentgroup with the probe directed through the needle in thesecond lumbar intervertebral foramen (N = 11), lidocaineinjection group (N = 7) and laser irradiation treatmentgroup (N = 10). All participants from the lidocaine injec-tion group and laser irradiation group reported a 100%reduction in visual analogue scale (VAS) scores immedi-ately after the treatment, while participants from thePRF group reported a 62.5% reduction in pain. At 1-month follow-up laser irradiation group had a 55.5%reduction in pain; lidocaine injection group 62.5% reduc-tion and PRF group only 20% [14].An RCT by Lee et al. [15] analyzed predictive value

and cost-effectiveness of the use of diagnostic blocks be-fore PRF treatment. They included 60 participants suf-fering from LBP with or without lower-limb pain,randomized into two groups. In one group (N = 30) par-ticipants received DRG blocks with 1 ml of 2% bupiva-caine and 1ml of 2% triamcinolone, and those who hadat least 50% improvement were scheduled for PRF


treatment. The other group (N = 30) received only PRFtreatment without DRG blocks. Limited low back painwas treated with DRG block or PRF applied to the L2DRG; lower -limb pain was treated with PRF applied tothe L3–S1 DRG. The authors concluded that DRGblocks had no statistically significant impact on the re-sults of PRF treatment, while their application resultedin overall higher medical costs [15].Yang et al. [16] reported results of a retrospective co-

hort study that aimed to develop a patient-mounted nav-igated intervention (PaMNI) system for spinal diseasesto evaluate the success of the PRF treatment. The studyalso included a pilot clinical trial were the new PaMNIsystem (N = 16) was compared to conventional fluoros-copy (N = 13). In all patients, PRF treatment was deliv-ered on the L4 DRG. Both groups showed a reduction inVAS scores 1 month after the treatment with no statisti-cally significant difference between groups (P = 0.238).However, the study showed the feasibility and efficacy ofthe PaMNI system [16].

Before and after comparison by Hsu et al. [17]followed 84 participants up to 3 years to investigate thecorrelation between different types of lumbar lordosiswith the outcomes of PRF treatment applied to L2 DRGin chronic low back pain. The analysis showed that after3-year follow-up participants had a statistically signifi-cant reduction in low back pain, regardless of the type oflumbar lordosis [17]. The study by Tsou et al. [18], alsofollowed participants for up to 3 years. They includedparticipants who had low back pain with lower -limbpain (N = 78) or without it (N = 49). LBP was treatedwith PRF applied to the L2 DRG and lower-limb painwas treated with PRF applied to the L3–S1 DRG. Per-centage of participants achieving at least 50% improve-ment in VAS scores was similar in both groups at 1-yearfollow-up, with 20 out of 45 participants (44.44%) in thegroup without lower -limb pain and 34 out of 74 partici-pants (45.95%) in the group with lower -limb pain [18].None of the studies reported serious adverse events. Two

studies reported minor complications: mild discomfort

Fig. 1 Flow chart of study inclusion


Table

1Characteristicsabou

tefficacyandsafety

ofinclud

edstud

ies

Autho

randyear/Study

design

(Cochrane

hand

book

andstud

yauthors)

Interven

tions

priorto

PRF

treatm

ent

Num

berof

participants(fo

reach

pain

cond

ition

treated)

Follow-up

Outcomemeasures

Results:efficacy

forpain

intensity

Con

clusion

statem

ent

abou

tefficacy

Results:serious

adverseeven

tsResults:any

othe

rsafety

data

Con

clusion

statem

ent

abou

tsafety

Low

backpain(LBP)

Holanda

2016

[14]

RCT/pilotstud

yNoothe

rinterven

tion

PRFtreatm

ent

grou

pn=11;

lidocaine

injection

grou

pn=7;

laserirradiatio

ntreatm

entgrou

pn=10

5min

and1

mon

th1.Lumbarpain

intensity

byVA

Spresen

tedas

percen

tage

ofrelativedifference

2.Chron

icLBP

reliefby

PRS

PRFgroup

:VA

Srelativedifference

at5min:62.5%

VASrelativedifference

at1mon

th:20%

Lidoc

aine

injection

group

:VASrelative

differenceat

5min:

100%


at1mon

th:62.5%

Lasertrea

tmen

tgroup

:VA

Srelativedifference

at5min:100%


at1mon

th:55%

Positive

conclusive

NoSA

Esoccurred

Somepatients

expe

rienced

onlymild

discom

fort

durin

gproced

ure

Not

repo

rted

Lee2018

[15]

RCT/rand

omized

,prospe

ctive,and

comparativestud

y

Diagn

ostic

block

+PRFgrou

preceived

diagno

sticblock

with

1mlo

f2%

bupivacaineand

1mlo

f2%

triamcino

lone

.

Diagn

ostic

block+

PRFgrou

p(n=30);

PRFgrou

p(n=30)

2weeks,1,3

and6mon

ths

1.Pain

intensity

byNRS

2.Functio

nal

disabilitiesby

ODI

Diagno

stic

block

+PR

Fgroup

:BaselineNRS:8

(rang

e5–9);

NRS

at2weeks:2

(rang

e1–7);

NRS

at1mon

th:2

(rang

e1–8);

NRS

at3mon

ths:3

(rang

e1–8);

NRS

at6mon

ths:4

(rang

e1–8).

PRFalon

egroup

:BaselineNRS:7.5rang

e(3–10);

NRS

at2weeks:2

(rang

e1–9);

NRS

at1mon

th:2

(rang

e1–9);

NRS

at3mon

ths:3

(rang

e1–9);

NRS

at6mon

ths:4

(rang

e1–9).

Pvalues

comparison

betw

eengrou

ps:

NRS

at2weeks:P

=0.302

NRS

at1mon

th:P

=0.690

NRS

at3moths:P

=0.957

Positive

inconclusive

Not

repo

rted

Not

repo

rted

Not

repo

rted


Table


tefficacyandsafety

ofinclud

edstud

ies(Con

tinued)

Autho

randyear/Study

design

(Cochrane

hand

book

andstud

yauthors)

Interven

tions

priorto

PRF

treatm

ent

Num

berof

participants(fo

reach

pain

cond

ition

treated)

Follow-up

Outcomemeasures

Results:efficacy

forpain

intensity

Con

clusion

statem

ent

abou

tefficacy

Results:serious

adverseeven

tsResults:any

othe

rsafety

data

Con

clusion

statem

ent

abou

tsafety

NRS

at6mon

ths:P=

0.673

Yang

2010

[16]

RCS/in

vivo

clinical

trial

Noothe

rinterven

tion

PaMNIsystem

n=

16;

conven

tional

fluoroscopy

n=13

1mon

th1.Pain

intensity

byVA

SPa

MNIg

roup

:BaselineVA

S:5.8(±2.3);

VASat

1mon

th:4.1(±

2.1).

P=0.005.

Fluo

roscop

ygroup

:BaselineVA

S:6.5(±2.2);

VASat

1mon

th:5.3(±

2.8).

P=0.067.

Nostatisticaldifference

betw

eengrou

psat

1mon

th(P=0.238).

Positive

conclusive

Not

repo

rted

Not

repo

rted

Not

repo

rted

Hsu

2017

[17]

BA/retrospe

ctive

stud

y

Noothe

rinterven

tion

841weekafterthe

treatm

entand

at3,6,9,12

mon

thsand

yearly

postop

eratively

(for3yearsin

total)

1.Pain

intensity

byVA

S2.Functio

nal

disabilitiesby

ODI

Analysisof

VASscores

forpain

indicated

sign

ificant

redu

ctions

oflow

back

pain

durin

gthe3-year

follow-upfor

patientswith

all4

type

sof

lumbarlordosis.

Positive

conclusive

NoSA

Esoccurred

Cereb

ralspinal

fluid

leaking

from

the

cann

ulas

oftw

opatientswhile

thene

edlewas

beingdirected

towardthe

DRG

.This

leakageceased

immed

iately

afteradjusting

thelocatio

nof

thene

edletip

.

Specific

adverse

even

tsmen

tion,no

overall

conclusion

abou

tsafety

Tsou

2010

[18]

BA/no

tstated

Noothe

rinterven

tion

Group

A(CLBP

with

outlower-limb

pain)n=49;

Group

B(CLBPwith

lower-limbpain)

n=78

From

1weekup

to3yearspo

st-

operatively

1.Pain

intensity

byVA

S2.Adverse

even

ts

Group

A,L

2trea

tmen

t:≥50%

VAS

improvem

ent:

at1week:25/49

(51.02%);

at3mon

ths:27/49

(55.1%

);at

1year

20/45(44.44%).

Group

B,L

2trea

tmen

t:≥50%

VAS

improvem

ent:

at1week:34/78

(43.59%);

at3mon

ths:37/78

(47.44%);

at1year:34/74

(45.95%).

Positive

conclusive

NoSA

Esoccurred

Noob

viou

scomplications

wereob

served

Positive

conclusive

Postsurgical

pain

Albayrak2017

[19]

InthePRF

PRFgrou

p(TEN

S+

15days

and1-

1.Pain

intensity

byPR

Fgroup

activity:

Positive

NoSA

EsNo

Not

repo

rted


Table


tefficacyandsafety

ofinclud

edstud

ies(Con

tinued)

Autho

randyear/Study

design

(Cochrane

hand

book

andstud

yauthors)

Interven

tions

priorto

PRF

treatm

ent

Num

berof

participants(fo

reach

pain

cond

ition

treated)

Follow-up

Outcomemeasures

Results:efficacy

forpain

intensity

Con

clusion

statem

ent

abou

tefficacy

Results:serious

adverseeven

tsResults:any

othe

rsafety

data

Con

clusion

statem

ent

abou

tsafety

PCS/retrospe

ctive

stud

yof

prospe

ctively

collected

data

grou

pparticipants

received

prog

nostic

diagno

sticblock

priorto

involvem

ent.

exercise

+PRF)

n=

22;

TENSgrou

p(TEN

S+exercise)n=17

mon

thpo

sttreatm

entand

followinglast

controlexamin-

ation.Themean

follow-uptim

ewas

253.8±109

days;for

TENS

grou

p:217±

114days

andfor

PRFgrou

p:282.2±97

days

VAS

2.Deg

reeof

neurop

athicpain

redu

ctionby

DN4

3.Chang

ein

knee

flexion

byRO

M4.Functio

nalstatus

byWOMAC

5.Patient

satisfaction

Successwas

defined

asat

least

50%

redu

ctionto

theVA

S(activity,

rest,night)

baselineVA

S:6.6(±1.5);

VASat

15days:3

(±1.4);

VASat

1mon

th:3.9(±2);

VASat

lastcontrol:3.5

(±2.4).

PRFgroup

rest:

baselineVA

S:4.3(±1.7);

VASat

15days:1.8(±

0.9);

VASat

1mon

th:2.6(±

1.5);

VASat

lastcontrol:2(±

1.6).

PRFgroup

night:

baselineVA

S:3.8(±2.2);

VASat

15days:1.5(±

1.1);

VASat

1mon

th:2.1(±

1.4);

VASat

lastcontrol:1.7

(±1.4).

TENSgroup

activity:

baselineVA

S:5.9(±1.9);

VASat

15days:3.8(±

2.2);

VASat

1mon

th:4.3(±

2.2);

VASat

lastcontrol:4.4

(±2.1).

TENSgroup

rest:

baselineVA

S:5(±2.4);

VASat

15days:2.6(±

2.4);

VASat

1mon

th:3.4(±

2.5);

VASat

lastcontrol:2.8

(±2.1).

TENSgroup

night:

baselineVA

S:4.3(±2.6);

VASat

15days:2.1(±

2.7);

VASat

1mon

th:2.7(±

2.6);

VASat

lastcontrol:2.6

(±1).

Sign

ificant

difference

achieved

inan

improvem

entof

atleast

50%

ontheVA

Sscores

atactivity

followingthe

conclusive

occurred

complications

wereob

served


Table


tefficacyandsafety

ofinclud

edstud

ies(Con

tinued)

Autho

randyear/Study

design

(Cochrane

hand

book

andstud

yauthors)

Interven

tions

priorto

PRF

treatm

ent

Num

berof

participants(fo

reach

pain

cond

ition

treated)

Follow-up

Outcomemeasures

Results:efficacy

forpain

intensity

Con

clusion

statem

ent

abou

tefficacy

Results:serious

adverseeven

tsResults:any

othe

rsafety

data

Con

clusion

statem

ent

abou

tsafety

lastcontrolexamination

betw

eenthetw

ogrou

ps(P=0.006),b

utno

ton

theVA

Sscores

atrestandnigh

t(P>

0.05).

Coh

en2006

[20]

RCS/retrospe

ctive

data

analysis

Noothe

rinterven

tion

PRFDRG

grou

pn=13;

PRFICNgrou

pn=

15;

MM

grou

pn=21

6weeks,3

mon

ths

1.Pain

intensity

byVA

S2.Answersto

2qu

estio

nsevaluatin

gpatient

satisfactionand

functio

nal

improvem

ent

Successful

was

defined

as≥50%

pain

redu

ctionon

VASandaffirmative

answ

erto

2qu

estio

ns

Noseparate

VASscores

show

nin

manuscript,

successwas

achieved

asfollows.:

PRFDRG

group

:6weeks:61.5%

3mon

ths:53.8%

PRFICNgroup

:6weeks:21.4%

3mon

ths:6.7%

MM

group

:6weeks:27.3%

3mon

ths:19.9%

Effect

didno

treach

statisticalsign

ificanceat

6weeks

(P=0.12).

At3mon

ths,success

rate

forPRFDRG

grou

pwas

sign

ificantlygreater

than

forthosepatients

treatedwith

PRFICN

(P=0.01),and

approached

sign

ificance

whe

ncomparedwith

MM

(P=0.06).

Positive

conclusive

Smallinciden

tal

pneumotho

rax

was

foun

ddu

ringaroutine

scan

ofthelung

fieldsafterPRF

DRG

.This

patient

was

not

symptom

atic

andwas

treated

conservatively

with

observation.

Noothe

rcomplications

occurred

Not

repo

rted

Fam

2018

[21]

BA/sing

learm

interven

tionstud

y

Steroid

injections

with

1mlo

fbu

pivacaine

0.25%

and1ml

of dexamethasone

4mgin

atotal

volumeof

2ml

immed

iately

afterPRF

proced

ure.

n=100

1week,1,3and

6mon

ths

1.Pain

intensity

byVA

S2.Qualityof

lifeby

QOLS

3.Chang

ein

useof

pain

med

ication

4.Adverse

effects

5.Patient

satisfaction

BaselineVA

S:7.48

±1.46

(med

ian:

8);

VASat

1week:5.01

±2.61

(med

ian:

5)(P=

0.032344);

VASat

1mon

th:3.26±

2.37

(med

ian:

3)(P<

0.0001);

VASat

3mon

ths:4.44

±2.8(m

edian:

4)(P=

0.00139);

VASat

6mon

ths:4.7±

2.88

(med

ian:

4)(P=

0.0057).

Positive

inconclusive

NoSA

Esoccurred

Pain

atthe

need

lingsite,

feverof

unknow

netiology

atthe

nigh

tof

interven

tion,

mild

tomod

erate

elevationof

glucoselevelin

portionof

diabetic

participants

Positive

inconclusive

Pain

associated

withhe

rpes

zoster

Kim

2017

[6]

RCS/retrospe

ctive

Noothe

rinterven

tion

PRFgrou

pn=20;

continuo

us1,3and6

mon

ths

1.Pain

intensity

byNRS

PRFgroup

:baselineNRS:6.30±0.98

Positive

conclusive

NoSA

Esoccurred

1patient

complaine

dof

Not

repo

rted


Table


tefficacyandsafety

ofinclud

edstud

ies(Con

tinued)

Autho

randyear/Study

design

(Cochrane

hand

book

andstud

yauthors)

Interven

tions

priorto

PRF

treatm

ent

Num

berof

participants(fo

reach

pain

cond

ition

treated)

Follow-up

Outcomemeasures

Results:efficacy

forpain

intensity

Con

clusion

statem

ent

abou

tefficacy

Results:serious

adverseeven

tsResults:any

othe

rsafety

data

Con

clusion

statem

ent

abou

tsafety

coho

rtstud

yep

iduralgrou

p(ro

pivacaine)

n=22

2.Doseof

anticon

vulsants

andanalge

sics

Con

tinu

ousep

idural

group

:baselineNRS:6.73±0.88

NRS

values

were

sign

ificantlylower

inPRFgrou

pfro

m1to

3mon

thsand6mon

ths

aftertheproced

ure(P=

0.029)

than

thosein

continuo

usep

idural

grou

p.

pain

atthe

proced

uresite,

anditim

proved

with

infew

days

Cervico

gen

iche

adache

vanZu

ndert2003

[22]

BA/clinicalaudit

Diagn

ostic

block

priorto

involvem

ent.

Participantswith

>50%

pain

reliefreceived

PRF.

n=14

2mon

thsand6

mon

thsafter

thelastpatient

wereinclud

ed.

Meanfollow-up

was

19.4

mon

ths(±8.9

mon

ths),m

ax-

imum

2.5years.

1.Satisfactorypain

relief(GPE:d

efined

asascoreof

6or

7po

intson

theLikert

scale;at

least50%

pain

relief

2.Durationof

the

effect

3.Other

treatm

ents

4.Chang

ein

useof

pain

med

ication

Dataabou

tpain

relief

(GPE):

9/14

patients(64%

)repo

rted

successful

pain

redu

ction(6

or7po

ints

ontheGPE

Likertscale).

Positive

conclusive

NoSA

Esoccurred

Noothe

rcomplications

observed

Positive

conclusive

Zhang2011

[23]

CR/CR

Diagn

ostic

blocks

with

1.5%

lidocaine

.Po

sitive

respon

sewas

considered

as90%

pain

relief

lastingfor30

min.

n=2

6mon

ths

1.Pain

intensity

byNRS

Patien

t1:

BaselineNRS:5;

NRS

at6mon

ths:0.

Patien

t2:

BaselineNRS:4;

NRS

at6mon

ths:0.

Positive

inconclusive

Nosign

ificant

complications

occurred

Nosign

ificant

complications

occurred

Not

repo

rted

Com

plexregiona

lpainsynd

rome

Albayrak2016

[24]

CR/CS

Noothe

rinterven

tion

n=2

1and3days

afterPRF,2and

5or

10mon

ths

(differen

tlast

follow-uptim

epo

intfor2

patients)

1.Pain

intensity

byVA

S2.RO

Mde

gree

Patien

t1:

BaselineVA

Sdu

ring

movem

ent:80;

VASat

3days:30;

VASat

2and10

mon

ths:

20.

Patien

t2:

BaselineVA

Sdu

ring

movem

ent:100;

VASat

3days:30;

VASat

2mon

ths:20;

VASat

5mon

ths:10.

Positive

inconclusive

NoSA

Esoccurred

No

complications

wereob

served

Not

repo

rted

Apiliogu

llari2015

[25]

CR/CR

Noothe

rinterven

tion

n=1

1dayafter

treatm

ent(2

1.Pain

intensity

byVA

SBaselineVA

S:100;

VASat

1day(PRF

onPo

sitive

inconclusive

NoSA

Esoccurred

Nosign

ificant

complications

Not

repo

rted


Table


tefficacyandsafety

ofinclud

edstud

ies(Con

tinued)

Autho

randyear/Study

design

(Cochrane

hand

book

andstud

yauthors)

Interven

tions

priorto

PRF

treatm

ent

Num

berof

participants(fo

reach

pain

cond

ition

treated)

Follow-up

Outcomemeasures

Results:efficacy

forpain

intensity

Con

clusion

statem

ent

abou

tefficacy

Results:serious

adverseeven

tsResults:any

othe

rsafety

data

Con

clusion

statem

ent

abou

tsafety

weeks

afterfirst

PRFthe

treatm

entwas

repe

ated

),6

mon

ths

L5):50;

VASat

2weeks

(after

repe

ated

PRFon

L4):10.

Thepatient

had

symptom

sreliefforover

6mon

ths.

occurred

Intractable

verteb

ralm

etastaticpain

Arai2015[26]

CS/CR

Noothe

rinterven

tion

n=15

0,1,7,21,28,35

and42

days

1.Pain

intensity

byNRS

atrestand

whilemoving

NRS

atrest:

baselineNRS:from

1to

4(m

edian3);

NRS

atday1:med

ian2;

NRS

atday7:med

ian1;

NRS

atday21:m

edian

1. Sign

ificant

decrease

in3

weeks

(P<0.0001).

NRS

while

mov

ing:

baselineNRS

from

5to

10(m

edian8);

NRS

atday1:med

ian4;

NRS

atday7:med

ian4;

NRS

atday21:m

edian

3. Sign

ificant

decrease

in3

weeks

(P<0.0001).

Positive

conclusive

NoSA

Esoccurred

Noothe

rcomplications

occurred

Not

repo

rted

Chron

icscrotala

ndinguina

lpain

Hofmeester

2013

[27]

CR/CR

Diagn

ostic

block

with

1mlo

flevobu

pivacaine

0.25%

n=1

12mon

ths

1.Pain

intensity

byVA

SBaselineVA

Sscores:7–8;

VASinitiallyafter

interven

tion:

4;VA

Sat

12mon

ths:0–1.

Positive

conclusive

Not

repo

rted

Not

repo

rted

Not

repo

rted

Occipital

radiating

painin

rheu

matoidarthritis

Lee2015

[28]

CR/CR

Diagn

ostic

block

with

0.3mlo

f0.75%

levobu

pivacaine

and1mg

triamcino

lone

n=1

6mon

ths

1.Pain

intensity

byVA

SBaselineVA

S:10;

VASat

6mon

ths:0.

Positive

conclusive

Not

repo

rted

Not

repo

rted

Not

repo

rted

Chron

icmigraine

Li2018

[29]

CR/CR

Diagn

ostic

block

with

1mlo

f2%

lidocaine

n=1

1year

1.Pain

intensity

byVA

SBaselineVA

S:8;

VASat

1year:com

plete

pain

relief.

Positive

inconclusive

Not

repo

rted

Not

repo

rted

Not

repo

rted

Abb

reviations:B

Abe

fore

andafter,CR

case

repo

rt,C

Scase

serie

s,CLBP

chroniclow

back

pain,D

RGdo

rsal

root

gang

lion,

GPE

glob

alpe

rceivedeffect,ICN

intercostaln

erves,MM

med

ical

man

agem

ent,NRS

numerical

ratin

gscale,ODIO

swestrydisabilityinde

x,Pa

MNIsystem

patie

nt-m

ount

naviga

tedinterven

tion,

PRFpu

lsed

radiofrequ

ency,P

RSpa

inreliefscaleQOLS

quality

oflifescale,

RCSretrospe

ctive

coho

rtstud

y,RO

Mrang

eof

motion,

TENStran

scutan

eous

electrical

nervestim

ulation,

SAEs

serio

usad

verseeven

ts,V

ASvisual

analog

uescale,WOMACfunctio

nalstatusby

Western

Ontario

andMcM

aster

universitie

sosteoa

rthritisinde

x


Table

2Parametersof

pulsed

radiofrequ

ency

treatm

entof

dorsalroot

gang

lion

Autho

randyear

Com

parator

Protocol

used

fortreatm

ent

Deviceused

Positio

nof

theelectrod

e

Low

backpain

Holanda

2016

[14]

PRFtreatm

entand

lidocaine

injectionvs.

laserirradiatio

n

Pulsewidth:20mswith

wash-

outpe

riodof

480ms;

Freq

uency:50

Hz;

Amplitu

de:45V;

Duration:

5min

(with

washou

tpe

riods

of300ms);

Tempe

rature:42°C

150mm

RFprob

ewith

5mm

activetip

(com

pany

isno

tspecified

);COSM

ANG4pu

lsege

nerator

(Cosman

Med

ical,Burlington

,MA,U

SA).

L2

Lee2018

[15]

Diagn

ostic

block+PRF

Amplitu

de:100

V;Duration:

240s;

Tempe

rature:40–42

°C

20-gauge

cann

ulaandCosman

Four-Electrode

Radiofrequ

ency

Gen

erator

(G4)

(Cosman

Med

ical,Burlington

,MA,U

SA).

L2-L5

andS1

Yang

2010

[16]

2im

plantatio

ntechniqu

esNostim

ulationparametersgiven

22-gauge

,SMK-C10

(Radionics

Inc.,Burlington

,MA,

USA

).RF

gene

ratorno

tspecified

.L4

Hsu

2017

[17]

Nocomparator

Freq

uency:2Hz;

Amplitu

de:45V;

Duration:

120s;

Tempe

rature:42°C

10-cm

22-gauge

sliced

-tip

cann

ulawith

1cm

ac-

tivetip

(com

pany

isno

tspecified

);RF

gene

rator

(Baylis

Med

icalCom

pany,M

ontreal,Canada).

L2

Tsou

2010

[18]

Nocomparator

Freq

uency:2Hz;

Amplitu

de:45V;

Duration:

120s;

Tempe

rature:42°C

10-cm,22-gaug

e,curved

-tip

cann

ulawith

a1cm

activetip

electrod

e(com

pany

notspecified

);RF

gene

rator(Baylis

Med

icalCo.,M

ontreal,Canada).

L2-L5andS1

Postsurgical

pain

Albayrak2017

[19]

TENS+exercise

vs.TEN

S+exercise

+PRF

Pulsewidth:20msactiveand

480mssilent

perio

ds;

Freq

uency:2Hz;

Amplitu

de:45V;

Duration:

120s;

Tempe

rature:42°C

22-gauge

cann

ula(OWLRF

cann

ula100mm)with

5mm

activetip

electrod

e(Diro

sTechno

logy

Inc.,

Canada);N

euroTherm

1100

RFge

nerator

(NeuroTherm,W

ilmington

,MA,U

SA).

L4

Coh

en2006

[20]

Intercostaln

erve

stim

ulationandmed

ical

managem

ent

Pulsewidth:20msin

1scycle;

Freq

uency:2Hz;

Amplitu

de:45V;

Duration:

120s;

Tempe

rature:42°C.

Theproced

urewas

repe

ated

4tim

es,for

atotald

urationof

8min.

10cm

electrod

ewith

a5mm

activetip

(PMC22–

100-5,BaylisMed

ical,M

ontreal,Quebe

c,Canada);

PMG-115-TD,V2.0A

RFge

nerator(Baylis

Med

ical

Com

pany,M

ontreal,Canada).

ExactDRG

sareno

tspecified

Fam

2018

[21]

Nocomparator

Duration:

120s;

Tempe

rature:42°C

2cycles

perfo

rmed

22-gauge

,10cm

,curvedcann

ulawith

10mm

activetip

(Baylis

Med

icalCom

pany,M

ontreal,

Canada).RFge

neratorused

notrepo

rted

.

T2andT3

Pain

associated

withhe

rpes

zoster

Kim

2017

[6]

Con

tinuo

usep

iduralblock

(ropivacaine)

Pulsewidth:20ms;

Freq

uency:2Hz;

Amplitu

de:45V;

Duration:

360s;

Tempe

rature:42°C

22-gauge

10cm

electrod

ewith

10mm

activetip

(Radionics

Inc.,Burlington

,MA,U

SA);RF

gene

rator

notspecified

.

Cervical,thoracic,

lumbo

sacral(exact

DRG

sno

tspecified

)

Cervico

gen

iche

adache


Table

2Parametersof

pulsed

radiofrequ

ency

treatm

entof

dorsalroot

gang

lion(Con

tinued)

Autho

randyear

Com

parator

Protocol

used

fortreatm

ent

Deviceused

Positio

nof

theelectrod

e

vanZu

ndert2003

[22]

Nocomparator

Pulsewidth:20ms;

Amplitu

de:45V;

Duration:

120s(20mscurren

tand480mswith

outcurren

t);

Tempe

rature:42°C

54mm,22-gaug

eSM

KPo

lene

edlewith

4mm

ac-

tivetip

(Cotop

InternationalB

V,Amsterdam,

Nethe

rland

s);RFG

3CPlus

RFge

nerator(Radionics

Inc.Bu

rling

ton,

MA,U

SA).

CervicalD

RG

Zhang2011

[23]

Nocomparator

Duration:

360s;

Tempe

rature:42°C

Inform

ationno

tgiven.

C2

Com

plexregiona

lpainsynd

rome

Albayrak2016

[24]

Nocomparator


480mssilent

perio

ds;

Freq

uency:2Hz;

Amplitu

de:40V;

Duration:

120s;

Tempe

rature:42°C

22-gauge

cann

ula(OWLRF

cann

ula54

mm)with

4mm

activetip

electrod

e(Diro

sTechno

logy

Inc.,

Canada);N

euroTherm

1100

RFge

nerator

(NeuroTherm,W

ilmington

,MA,U

SA).

C5andC6

Apiliogu

llari2015

[25]

Nocomparator


480mssilent

perio

ds;

Freq

uency:2Hz;

Amplitu

de:45V;

Duration:

120s;

Tempe

rature:42°C

22-gauge

cann

ula(OWLRF

cann

ula54

mm)with

4mm

activetip

electrod

e(Diro

sTechno

logy

Inc.,

Canada);N

euroTherm

1100

RFge

nerator

(NeuroTherm,W

ilmington

,MA,U

SA).

L4andL5

Intractable

verteb

ralm

etastaticpain

Arai2015[26]

Nocomparator


480mssilent

perio

ds;

Freq

uency:2Hz;

Amplitu

de:40V;

Duration:

120s;

Tempe

rature:42°C

5mm

activetip

KT,g

uiding

need

le(Hakko

Co.

Ltd.,

Tokyo,

Japan);RFge

neratorJK-3

NeuroTherm

(MorganAutom

ationLtd.,Liss,UK).

Oneach

metastatic

verteb

ralb

ody,L1–5

and

Th7,9–12

Scrotala

ndinguina

lpain

Hofmeester

2013

[27]

Nocomparator

Pulsewidth:8

ms;

Freq

uency:2Hz;

Amplitu

de:45V;

Duration:

480s;

Tempe

rature:42°C

Inform

ationno

tgiven.

T12,L1

andL2

Occipital

radiating

painin

rheu

matoidarthritis

Lee2015

[28]

Nocomparator

Duration:

120s,threecycles

perfo

rmed

;Tempe

rature:42°C

21-gauge

10cm

insulatedne

edle(com

pany

isno

tspecified

);RF

gene

ratorno

tspecified

.C2

Chron

icmigraine

Li2018

[29]

Nocomparator

Pulsewidth:20ms;

Freq

uency:2Hz;

Amplitu

de:45V;

Duration:

900s;

Tempe

rature:42°C

22-gauge

need

le,RFge

neratorG4(Cosman

Med

ical,Burlington

,MA,U

SA).

C2

Abb

reviations:D

RGdo

rsal

root

gang

lion;

PRFpu

lsed

radiofrequ

ency;R

Fradiofrequ

ency


Table

3Inclusionandexclusioncriteria

andbaselinecharacteristicsof

participants

IDInclusioncriteria

/Previous

treatm

ent

Exclusioncriteria

Baselinecharacteristics

Low

backpain

Holanda

2016

[14]

-low

back

pain

for>3mon

ths

-cancer

inlumbarregion

-coagulationdisturbance

-infection

-ne

urolog

icde

ficits

PRFtrea

tmen

tgroup

:-2males,9

females

-agerang

e:42–86years

-pain

duratio

nrang

e:3–144mon

ths

Lidoc

aine

injectiongroup

:-3males,4

females

-agerang

e:33–82years

-pain

duratio

nrang

e:3–48

mon

ths

Lasertrea

tmen

tgroup

:-3males,7

females

-agerang

e:35–84years

-pain

duratio

nrang

e:14–120

mon

ths

Lee2018

[15]

-age20

yearsor

olde

r-pred

ominantly

axiallow

back

pain

for>3

mon

ths

-med

icationtherapyfor>3mon

thswith

out

bene

fit-ph

ysicalrehabilitationfor>3mon

thswith

out

bene

fit

-an

iden

tifiedetiology

oflow

back

pain

(i.e.,

gradeIIor

IIIspon

dylolisthesis)

-po

sitiverespon

seto

previous

spine

interven

tions

such

asep

iduralsteroids

orsacroiliacjointblocks

-previous

facetinterven

tions,lum

barspine

fusion

-un

treatedcoagulop

athy

-concom

itant

med

ical(e.g.,un

stableangina

orde

gene

rativeosteoarthritisof

knee),or

psychiatric

cond

ition

s-concurrent

lumbarpain

gene

rator(i.e.,

muscular/fascialp

ain,

ororgans

with

inthe

abdo

minalcavity)that

couldconfou

ndthe

diagno

sisof

low

back

pain

TFES

IDRG

block

+PR

Ftrea

tmen

tgroup

:-med

ianage:74

years,rang

e53–90

years

-med

iandu

ratio

nof

symptom

s:26

mon

ths,rang

e:3–58

mon

ths

PRFtrea

tmen

talon

egroup

:-med

ianage:75

years,rang

e33–93

years

-med

iandu

ratio

nof

symptom

s:25

mon

ths,rang

e:3–125mon

ths

Yang

2010

[16]

-chronicLBPwith

focaln

eurologicsymptom

sfor>3mon

ths

-spinaldisorders

-coagulop

athy

-concom

itant

med

icalor

psychiatric

illne

ss

PaMNIg

roup

:-5males,11females

-meanage:55.5±13.9years

Fluo

roscop

ygroup

:-2males,11females


Hsu

2017

[17]

-age20

yearsor

olde

r-LBPfor>6mon

thsthat

worsene

dup

onprolon

gedsittingor

standing

-failedto

improveafterat

least3mon

thsof

conservativetreatm

ent

-sagittalim

balance

-spinallisthesis

-infection

-tumor

-sten

osis

-disc

herniatio

ncausingne

rveroot

compression

-29

males,55females

-meanage:56.03±9.04

years

Tsou

2010

[18]

-chronicLBPwith

orwith

outlower-limbpain

for

>6mon

ths

-conservativetreatm

entfor>3mon

thswith

out

bene

fit-participantswith

symptom

sof

nerveroot

comprom

isedu

eto

mild

ormod

eratebu

lging

disc

also

includ

ed

Not

given

LBPwitho

utlower

limbpaingroup

:-26

males,23females

-men

age:62.94±12.39years

-leveltreated

:L2:49

LBPwithlower

limbpaingroup

:-33

males,45females

-men

age:63.88±14.00years

-levelstreated:

L2:78,L3:14,L4:33,L5:

72,S1:21


Table



participants(Con

tinued)

IDInclusioncriteria

/Previous

treatm

ent

Exclusioncriteria


Postsurgical

pain

Albayrak2017

[19]

-VA

Sscoreof

≥3du

ringactivity

-pain

lastingfor≥2mon

ths

-no

improvem

entwith

physicalmed

icineand

rehabilitation

-refractoryto

pharmacolog

icaltherapies

includ

ingparacetamol

2g/dayandthe

maxim

umtolerabledo

seof

nonsteroidalanti-

inflammatorydrug

sfor1weekandpreg

abalin

300mg/dayfor2weeks

-anypatholog

icalfeatures,suchas

acutestrain

orsprain

-stroke/cen

tralne

rvou

ssystem

disease

-serio

uspsychiatric

disorders

-sciatic

pain

-fib

romyalgia

-men

talimpairm

entaffectingability

toun

derstand

tests/measures

PRF+TE

NS+exercise

group

:-2(9.1%)males,20(90.9%

)females


TENS+exercise

group

:-2males

(11.8%

),15

(88.2%

)females


Coh

en2006

[20]

-age18

yearsor

olde

r-du

ratio

nof

pain

≥3mon

ths

-VA

Sscore≥5

-pain

deem

edto

beof

neurop

athicorigin

based

onhistoryandph

ysicalexam

ination

-presen

ceof

patholog

ythat

couldaccoun

tfora

majority

ofpe

rsistent

symptom

s(e.g.recurrent

cancer)

-un

treatedcoagulop

athy

-un

stablemed

icalor

psychiatric

cond

ition

PRFtrea

tmen

tgroup

:-6males,7

females


Intercostaln

erve

stim

ulation:

-7males,8

females


Med

ical

man

agem

entgroup

:-9males,12females


Fam

2018

[21]

-be

tween18

and65

years

-refractoryto

morph

inesulfate

(MST)and

preg

abalin

-bleeding

tend

ency

-localinfectio

nat

thesite

oftheinterven

tion

-psycho

logicald

isorde

rs-disturbe

danatom

y(con

genital,traumatic,and

postsurgical)

-allergyto

used

med

ication(localane

sthe

tics

andcontrast)

-inability

tolie

comfortablydu

ringthe

interven

tionas

thecardiopu

lmon

arydistress

Not

given

Pain

associated

withhe

rpes

zoster

Kim

2017

[6]

-participantswho

unde

rwen

ttheproced

ure

betw

een30

and180days

afterzoster

onset

-trigem

inal-nerve-in

volved

zoster

-follow-uploss

with

in6mon

thsafterthe

proced

ure

-participantswho

didno

treceiveapprop

riate

antiviraltreatmen

tdu

ringtheacuteph

aseof

herpes

zoster

-caseswhe

rebo

thproced

ures

werepe

rform

edbe

tween30

and180days

ofzoster

onset

PRFtrea

tmen

tgroup

:-11

males,9

females

-meanage:68.10±7.99

years

-days

from

zoster

onset:68.20±40.53

Con

tinu

ousep

idural

block

group

:-6males,16females


-days

from

zoster

onset:74.09±44.50

Cervico

gen

iche

adache

vanZu

ndert2003

[22]

-18

yearsor

olde

r-chronicpain

inthecervicalregion

for>6mon

ths

-ph

armacothe

rapy,p

hysicalo

rmanualthe

rapy,

TENS,and/or

rehabilitationprog

ram

with

out

bene

fit-tempo

rary

pain

reliefof

atleast50%

on7-po

int

Likertscaleafteradiagno

sticsegm

entaln

erve

block

-ability

toun

derstand

theinform

ationprovided

-inform

edconsen

t

-system

icdisease

-tumor

-clinicallyde

mon

strablene

urolog

icde

ficit

-sign

sof

radicularcompression

-5males,13females

-agerang

e:27–77years

-du

ratio

nof

pain

priorto

treatm

ent:<

1–40

years

-DRG

leveltreated

:C2:4,C3:2,C4:2,

C5:4,C6:3,C7:3


Table



participants(Con

tinued)

IDInclusioncriteria

/Previous

treatm

ent

Exclusioncriteria


Zhang2011

[23]

-initialdiagno

sticselectivethegreateroccipital

nerveblocks

with

1.5%

lidocaine

-pain

reliefof

90%

ormorelastingforat

least

30min.

NA

Patien

t1:

-40-years-old

wom

an-pain

lastingfor5years

Patien

t2:

-66-years-old

wom

en-pain

lastingfor1year

Com

plexregiona

lpainsynd

rome

Albayrak2016

[24]

-no

improvem

entwith

thecombine

duseof

med

icaltherapy,ph

ysicaltherapy,andthe

rehabilitationprog

ram

NA

Patien

t1:

-69-years-old

wom

en-9mon

thsof

previous

pain

Patien

t2:

-48-years-old

wom

en

Apiliogu

llari2015

[25]

NA

NA

16-years-old

girl

Intractable

verteb

ralm

etastaticpain

Arai2015[26]

-confirm

edto

have

verteb

ralm

etastasesby

bone

scintig

raph

y,compu

tedtomog

raph

y,and

magne

ticresonanceim

aging

-system

icanalge

sics

didno

tprovideasoun

dpain

relief

-ne

urolog

icalde

ficit

-coagulop

athy

-sign

ificant

cardiovascular

disease

-9males,6

females

-agerang

e:34–82years

Scrotala

ndinguina

lpain

Hofmeester

2013

[27]

-an

orchidop

exype

rform

ed-testblockof

therelevant

DRG

with

1mlo

flevobu

pivacaine0.25%

NA

-13-years-old

boy

Occipital

radiating

painin

rheu

matoidarthritis

Lee2015

[28]

-rig

ht3rdoccipitaland

right

4th,

-5th,

and6thcervicalmed

ialb

ranchblocks

with

levobu

pivacaine(0.3mL;0.75%)and

triamcino

lone

(1mg)

wereinjected

ateach

level

NA

-74-years-old

female

-pain

lastingfor2–3years

Chron

icmigraine

Li2018

[29]

-failure

ofph

armacolog

icaltherapyandstellate

gang

lionblock

-diagno

sticC2blockwith

1mLof

2%lidocaine

with

75–100%

pain

reliefforon

ly4days

NA

-34-years-old

female

-10

yearsof

chronicmigraine

Abb

reviations:D

RGdo

rsal

root

gang

lion,

LBPlow

back

pain,N

Ano

tap

plicab

le,P

aMNIsystem

patie

nt-m

ount

naviga

tedinterven

tion,

PRFpu

lsed

radiofrequ

ency,R

Fradiofrequ

ency,TEN

Stran

scutan

eous

electrical

nervestim

ulation,

TFESItransforaminal

epidural

steroidinjection,

VASvisual

analog

uescale


during the procedure [14] and leakage of the cerebrospinalfluid [17]. One study reported that there were no complica-tions [18]. Two studies from this group did not report anyoutcomes regarding safety [15, 16], but one of them pro-vided a general warning about the radiation dose exposure[16].In this group all studies reported positive statements

regarding the efficacy of the treatment, four studies hadpositive conclusive statements [14, 16–18] while onestudy had positive inconclusive statement [15]. Only onestudy reported a positive conclusive statement aboutsafety [18], one reported only specific adverse events thatoccurred [17], while others did not report any conclu-sion statements (Table 1 and Supplementary Table 3).

Post-surgical painThree studies explored PRF in postsurgical pain, with atotal of 188 participants. In a cohort study of Albayraket al. [19] there were 39 participants with postsurgicalpain after total knee arthroplasty. In another cohortstudy, Cohen et al. [20] included 49 participants suffer-ing from thoracic postsurgical pain. Fam et al. [21] in-cluded 100 women suffering from intercostobrachialneuralgia (ICBN) postmastectomy in a study designed asbefore and after comparison. Despite different etiologyof postsurgical pain the majority of participants experi-enced a reduction in pain after the treatment (details aregiven in Table 1).One participant from the study of Cohen et al. [20]

had a serious adverse event that could not be related toprocedure or treatment. Small pneumothorax was foundduring a routine scan after the PRF procedure. This par-ticipant was treated conventionally and monitored [20].Pain at the site of the procedure was reported as a mildcomplication [21]. The third study reported that compli-cations were not observed [19].Two studies from this group reported positive conclu-

sive statement for efficacy, while the conclusion forsafety was not reported [19, 20]. The study by Fam et al.[21] reported positive inconclusive statements for bothefficacy and safety [21] (Table 1 and SupplementaryTable 3).

Pain associated with herpes zosterA retrospective cohort study by Kim et al. [6] with 42participants addressed PRF of DRG for pain associatedwith herpes zoster but before post-herpetic neuralgia(PHN) was established. The study analyzed two groupsof participants; one received continuous epidural block(N = 22), and the other received PRF treatment (N = 20)after the acute phase of herpes zoster, but before itwas well established, meaning between 30 and 180 daysof the herpes zoster diagnosis. Participants from thecontinuous epidural block group received 0.187%

ropivacaine at the rate of 1 ml per hour, while concen-tration and rate of administration depended on pain re-lief and adverse effects (mean concentration ofropivacaine and infusion rates used were 0.22 ± 0.07%and 1.82 ± 0.65 ml/hr). When satisfactory pain relief wasachieved catheter was removed. Reduction in pain wassignificantly higher in the PRF group compared to a con-tinuous epidural block group (P = 0.029) up to 6 monthsafter the treatment [6]. From the safety aspect, only pro-cedural pain was reported [6]. The study abstract had apositive conclusive statement about efficacy, while safetyconclusion was not reported [6] (Table 1 and Supple-mentary Table 3).

Cervicogenic headacheThe before and after comparison by van Zundert et al.[22] included 18 participants, of which 14 had pain re-lated to non-neuropathic origin (their characteristicswere reported separately in Table 1). Participants werefollowed for a mean time of 19.4 months (maximumfollow-up time 2.5 years) [22]. Before study inclusion,participants received diagnostic nerve blocks with 0.5mL of 2% lidocaine. Treatment outcomes were scoredusing a 7-point Likert scale.Participants who had at least 50% pain relief were in-

cluded in the study and received PRF treatment. Suc-cessful PRF treatment was defined as 6 (≥ 50%improvement) or 7 (≥ 75% improvement) points on 7-point Likert scale (Global Perceived Effect good or verygood). Participants from the group of non-neuropathicpain origin had successful treatment in 9 cases whiletreatment was not successful in 5 cases. The case reportby Zhang et al. [23] described 2 participants who re-ported 100% pain relief lasting for 6 months after thetreatment. Both studies reported that no complicationsoccurred (Table 1).The study by van Zundert et al. [22] reported positive

conclusive statements about both, safety and efficacy,while Zhang et al. [23] reported positive inconclusivestatement about efficacy, while safety was not reported(Table 1 and Supplementary Table 3).

Complex regional pain syndromeThis group included only two case reports [24, 25] withthree participants included. Albayrak et al. [24] reportedcases of two women with post-stroke complex regionalpain syndrome (CRPS). Both patients used multipletreatment modalities before the PRF treatment, includ-ing medical therapy, physical therapy, rehabilitation pro-gram and transcutaneous electrical nerve stimulation(TENS). After PRF treatment, both participants had animmediate resolution of their symptoms that lasted upto 5 and 10months which were final follow-up timepoints [24].


Apiliogullari et al. [25] reported a case of a 16-year-oldgirl suffering from CRPS due to sequelae of poliomyel-itis, who did not respond to non-steroidal anti-inflammatory drugs. However, after two PRF treatments(first applied at L5 and repeated after 2 weeks at L4DRG) she reported immediate pain relief, with VASscores going from 100 points down to 10, this effectremained for over 6 months of follow-up [25]. Bothstudies reported that no complications occurred (Table1).Both studies from this group reported positive incon-

clusive statements about efficacy, while the conclusionabout safety was not reported [24, 25] (Table 1 and Sup-plementary Table 3).

Intractable vertebral metastatic painThe case series of Arai et al. [26] included 15 cases withvertebral metastatic pain, which demonstrated pain re-lief, defined as a 50% pain reduction from baselinevalues. Values on the numerical rating scale (NRS), mea-sured during rest and upon movement, were signifi-cantly lower 3 weeks after the PRF treatment (P <0.0001) [26]. From the safety aspect, there were no SAEsor other complications (Table 1). The study reportedpositive conclusive statements about efficacy, while con-clusion about safety was not reported [26] (Table 1 andSupplementary Table 3).

Chronic scrotal and inguinal painHofmeester et al. [27] reported the first case of usingPRF to treat scrotal and inguinal pain after orchidopexyin a 13-year boy. PRF was performed at three levels (T12-L2) after other treatment modalities have failed. ThePRF of DRG led to an immediate and lasting pain allevi-ation of more than 70% as reported by the patient [27].Information about safety was not reported. The study re-ported positive conclusive statements about efficacy,while the conclusion about safety was not reported [27](Table 1 and Supplementary Table 3).

Occipital radiating pain in rheumatoid arthritisLee et al. [28] reported PRF of the C2 DRG to treat oc-cipital radiating headache in a 74-year old woman withrheumatoid arthritis. The patient has not complained ofany occipital radiculopathy for 6 months, and the poster-ior neck pain has since been reduced to a visualanalogue scale (VAS) score of three, from initial 6/10.Information about safety were not reported [28]. Thisstudy also reported positive conclusive statements aboutefficacy, while the conclusion about safety was not re-ported [28] (Table 1 and Supplementary Table 3).

Chronic migraineLi et al. [29] reported a case of a 34-year old womanwho suffered from chronic migraine with occipital pain.She underwent PRF treatment after the failure of othertreatment modalities. The patient had complete pain re-lief with no symptoms 1 year after the treatment [29].Details are given in Table 1. The study did not reportconclusion about safety, while the conclusion about effi-cacy was positive inconclusive [29] (Table 1 and Supple-mentary Table 3).

Parameters of PRF treatmentLow back pain was a painful condition which had themost different treatment parameters among includedstudies, with a range of different values for amplitude(45 and 100 V), frequency (2 and 50 Hz) and duration oftreatment (120, 240 and 300 s). Pulse width was only re-ported in one study [14] (Table 2). In other studies pa-rameters were similar, the majority had a pulse width of20 ms, the amplitude of 45 V, frequency of 2 Hz and dur-ation of 120 s (Table 2). The temperature at the elec-trode tip was constant parameter, same in all studies,and set to 42 °C in order to avoid tissue damage.

Participants’ inclusion criteriaMore than a half of included studies were before andafter comparisons, case series or case reports where par-ticipants were included and scheduled for PRF treatmentafter failure of other treatment modalities and as a lasttreatment option (Table 3). On the other side, higher-quality studies, such as RCTs and cohort type studieshad clearly defined inclusion and exclusion criteria aswell as described participants’ baseline characteristics(Table 3).

Summary on the conclusiveness of the evidenceAmong 17 included studies, 11 studies had positive con-clusive statements about efficacy; the remaining hadpositive inconclusive statements. The majority of thestudies did not provide conclusive statements regardingsafety in the manuscript abstracts. Only three studiesprovided safety conclusiveness statements – two indi-cated that the evidence was positive conclusive, and onepositive inconclusive (Table 1 and Supplementary Table3).

Risk of biasAnalysis of two included RCTs, with Cochrane Rob tool,indicated that the majority of the domains were judgedwith unclear RoB due to insufficient information aboutthe used methodology (Supplementary Table 4, Fig. 2).Four non-randomized studies were eligible for assess-ment with ROBINS-I. The most common judgment foranalyzed domains (12 domains out of 28 domains judged


for these four studies) was serious RoB. Ten domainswere judged with moderate RoB, and only 6 domainswith low RoB (Supplementary Table 5, Fig. 2).

Studies awaiting classificationOne RCT, which aims to study DRG thermal RF versusPRF for metastatic pain in the thoracic vertebral bodyon 69 participants, is classified as completed on July 30,2018. Results were reported to Clinical Trials.gov butwere returned to the authors after the quality control re-view so results are still not publicly available(NCT03204942). A trial that aimed to study superiorhypogastric plexus block versus PRF for chronic pelviccancer pain on 40 participants is classified as ‘Not yetrecruiting’ since June 26, 2018 (NCT03228316). Studiesawaiting classification are described in SupplementaryTable 6.

DiscussionIn this systematic review, we included 17 studies aboutthe treatment of several non-neuropathic chronic painconditions with PRF directed to DRG. All studies pre-sented positive conclusions (both conclusive and incon-clusive) about the efficacy of the treatment. However, thestudies were mostly non-randomized, with small samplesizes, and issues related to the risk of bias. Therefore, theirresults should only be considered as preliminary.PRF was developed as a less destructive pain relief mo-

dality alternative to conventional radiofrequency (CRF)which can selectively block delta and C fibers [30]. Thefirst report about the clinical effects of PRF on DRG waspublished relatively recently, in 1998. Due to its theoret-ical benefits, it was postulated that PRF could be particu-larly helpful in neuropathic pain [31]. However, we haveobserved in the literature that clinicians and researchersapply PRF to non-neuropathic chronic pain as well.

Fig. 2 Risk of bias assessment for randomized controlled studies and cohort type studies


Despite the number of studies found in the literatureabout the treatment of non-neuropathic chronic pain inhumans with PRF, their findings cannot be generalized.In the studies that we have found, the PRF was usuallyinitiated after other treatments have failed. We reporteda similar issue in our recent systematic review in whichwe studied the efficacy and safety of EFS of DRG [12]. Inthat systematic review, we found only one RCT among29 included studies; most of the studies were low-levelof evidence – non-randomized study designs, includingcase series and case reports. The review about EFS ofDRG also included few participants, with a median of 6participants per study [12]. In this systematic reviewthere were 17 included studies, with a median of 28participants.The paucity of large and high-quality studies in the

field of DRG neuromodulation is likely due to the rela-tive novelty of this approach for the treatment of pain.In this systematic review, about PRF of DRG in non-neuropathic pain, only two of 17 included studies wereRCTs, and RoB judgment for the majority of their meth-odological aspects was unclear. Likewise, the most com-mon assessment in non-randomized studies assessedwith the ROBINS-I tool was that there was a serious riskof bias. Besides their suboptimal methodological report-ing, the analyzed studies were relatively small. Even thetwo included randomized controlled trials were small;one included a total of 28 patients in 3 groups, and theother one included 60 patients in two groups.The highest number of studies was found for the low

back pain indication. However, we were not able to per-form a meta-analysis due to clinical heterogeneity of thestudies, as can be seen from characteristics of includedstudies, different comparators used in included trials,and different stimulation parameters. Differences intreatment approaches can result in different clinicaloutcomes.Despite the low level of evidence, all of the analyzed

studies sent positive conclusions to the research com-munity in their abstracts. The majority of these conclu-sions were conclusive, i.e. they did not mention the needto conduct further studies on this subject. Despite theauthors’ positive conclusions regarding the tested inter-ventions, caution is needed when advising DRG targetedPRF to chronic pain patients, because of the paucity ofhigh-quality and high-level evidence. This interventionshould be tested in large-scale, high-quality RCTs totruly test whether the intervention has expected benefitsand harms. Until then, these studies should be treated aspreliminary evidence only.A broad focus of this systematic review could be con-

sidered as a limitation of this review, as we included anypain condition that fits the IASP criteria of non-neuropathic pain. Furthermore, we acknowledge that the

examined studies included patients with various clinicalconditions, and thus there is a possibility that the effect-iveness of the treatment depends on underlying patho-genic mechanisms. However, as can be observed fromour results, there were very few studies in each group ofindications; the highest number of studies (five) wasfound for low back pain. Therefore, focusing on everysingle one of these indications in a separate systematicreview would result in a high number of systematic re-views, with minimal results included. Furthermore, withthis approach, we are giving readers a very wide and in-formative picture of all the non-neuropathic pain condi-tions that were reported in the literature as treated withDRG targeted PRF.We have used IASP classification for definitions of

non-neuropathic pain; these classifications are evolv-ing and changing, so the included conditions may becategorized differently, depending on the time ofcategorization and reference classification used. Previ-ous versions of chronic pain classification were tosome extent insufficient for chronic neuropathic painconditions since some conditions were not definedproperly or were missing so we decided to use theupdated version of classification since it is crucial toget the comprehensive evidence synthesis. Accordingto the newest IASP classification that we used (ICD-11) when deciding about study inclusion we mighthave included some studies that in previous versionsof classification were classified either as neuropathicpain or as the pain of mixed origin. We have in-cluded CRPS 1 [25], which is not considered neuro-pathic pain. In the study of Kim et al. [6] the authorsstudied the effects of DRG PRF beyond the acutephase of zoster, bur before PHN was well established(from 30 days to 180 days after zoster onset). Thestudy of van Zundert [22] has excluded “signs of ra-dicular compression”.It has been questioned before what is the value of sys-

tematic review including poor evidence and small studies[32]. However, such systematic reviews are valuable be-cause they are highlighting the paucity of evidence andthe low quality of available information [33]. Our sys-tematic review is such a case. We even included twocase reports with only one participant which may beconsidered anecdotal rather than firm evidence. It couldbe argued that such studies should not even be includedin systematic reviews; however, we did not set any re-strictions regarding number of participants in our studyeligibility criteria. By showing that many clinicians andresearchers have published small studies, with low-levelevidence, about potential benefits of PRF in chronicnon-neuropathic pain, we hope that trialists will be in-spired to explore this intervention in studies that areconsidered high-level evidence.


ConclusionEven though PRF of DRG was primarily studied forneuropathic pain, we have found as many as 17 pub-lished studies that have reported the use of DRG tar-geted PRF in non-neuropathic pain conditions. Althoughall of these studies reported positive information regard-ing the analyzed interventions, considerable caution isneeded when interpreting these results as anything morethan preliminary. The quality of evidence is low, as therewere only two randomized controlled trials among in-cluded studies, and the risk of bias was predominantlyunclear in RCTs and severe among non-randomizedstudies. The majority of studies included patients thathave failed other therapies so these results cannot begeneralized. PRF treatment needs to be tested in new,high-quality and large-scale trials, to confirm the efficacyof this intervention.

Supplementary informationSupplementary information accompanies this paper at https://doi.org/10.1186/s12871-020-01023-9.

Additional file 1: Supplementary Table 1. Search strategies for fourbibliographic databases searched.

Additional file 2: Supplementary Table 2. Characteristics of excludedstudies.

Additional file 3: Supplementary Table 3. Conclusion statementspresented in the abstracts of included studies.

Additional file 4: Supplementary Table 4. Individual Cochrane risk ofbias judgments for randomized controlled trials.

Additional file 5: Supplementary Table 5. Individual ROBINSjudgments for non-randomized studies.

Additional file 6: Supplementary Table 6. Details about studiesawaiting classification.

AbbreviationsAEs: adverse events; BA: before and after comparison; CLBP: chronic low backpain; CR: case report; CRPS: complex regional pain syndrome; CRD: center forreviews and dissemination; CS: case series; DRG: dorsal root ganglion;EFS: electrical field stimulation; GPE: global perceived effect IASP –International Association for the Study of Pain; ICN: intercostal nerves;LBP: low back pain; MM: medical management; NA: not applicable;NRS: numeric rating scale; NRSD: non-randomized study designs;ODI: Oswestry disability index; PaMNI: patient-mounted navigatedintervention; PHN: post-herpetic neuralgia; PRF: pulsed radiofrequency;QOLS: quality of life scale; RCS: retrospective cohort study; RCT: randomizedcontrolled trial; RoB: risk of bias; ROBINS-I: Risk of Bias In Non-randomizedStudies of Interventions; ROM: range of motion; SAEs: serious adverse events;TENS: transcutaneous electrical nerve stimulation; TFESI: transforaminalepidural steroid injection; VAS: visual analogue scale; WHO ICTRP: WorldHealth Organization’s International Clinical Trial Registry Platform;WOMAC: functional status by Western Ontario and McMaster universitiesosteoarthritis index

AcknowledgementsWe are very grateful to Ms. Ana Utrobicic, expert librarian, for reviewing oursearch strategies and providing valuable advice.

Authors’ contributionsIV, SD, DS, LP: study design. IV, TM, SD, LFH, KV: data collection and analysis.IV, TM, SD, LFH, KV, DS, LP: manuscript writing, approval of final version ofthe manuscript

FundingThe study was funded by the Croatian Science Foundation (HRZZ) grant forYoung Scientist Career Development (HRZZ-DOK-2015-10-2774) and HRZZgrant for Treating Neuropathic Pain with Dorsal Root Ganglion Stimulationawarded to Prof Damir Sapunar (HRZZ-IP-2013-11-4126). The funders had norole in study design, data collection and analysis, decision to publish, orpreparation of the manuscript.

Availability of data and materialsThe datasets used and/or analyzed during the current study are availablefrom the corresponding author on reasonable request.

Ethics approval and consent to participateIn this study we analyzed only data from publicly available published articles;for this reason, ethic approval and consent of participants to participate arenot applicable.

Consent for publicationNot applicable.

Competing interestsNone.

Author details1Laboratory for Pain Research, University of Split School of Medicine,Šoltanska 2, 21000 Split, Croatia. 2Department of Anesthesiology,Reanimatology and Intensive Care, University Hospital Split, Spinčićeva 1,21000 Split, Croatia. 3Center for Translational and Clinical Research,Department of Proteomics, University of Zagreb School of Medicine, Šalata 3,10000 Zagreb, Croatia. 4Department for Safety and Efficacy Assessment ofMedicinal Products, Agency for Medicinal Products and Medical Devices,Ksaverska cesta 4, 10000 Zagreb, Croatia. 5Center for Evidence-BasedMedicine and Health Care, Catholic University of Croatia, Ilica 242, 10000Zagreb, Croatia.

Received: 20 March 2020 Accepted: 26 April 2020

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Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.


https://doi.org/10.1093/pm/pnaa141

https://training.cochrane.org/handbook/archive/v5.1/

https://training.cochrane.org/handbook/archive/v5.1/

https://doi.org/10.1002/14651858.ED000106(11

https://doi.org/10.1002/14651858.ED000106(11

efficacy and safety of pulsed radiofrequency as a method ... · it has been suggested that a dorsal...

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