A Randomized, Placebo-Controlled Studyto Assess the Efficacy of Lateral BranchNeurotomy for Chronic Sacroiliac Joint Painpme_1328 383..398

Nilesh Patel, MD,* Andrew Gross, MD,†Lora Brown, MD,‡ and Gennady Gekht, MD‡

*Advanced Pain Management, Green Bay, Wisconsin;

†Orthopedic Center of Florida, Ft. Myers, Florida;

‡Coastal Orthopedics, Pain and Rehabilitation,Bradenton, Florida, USA

Reprint requests to: Nilesh Patel, MD, AdvancedPain Management, 2595 Development Drive, GreenBay, WI 54311, USA. Tel: 941-744-6960; Fax:920-338-2131; E-mail: npatel@apmhealth.com.

Disclosure/Conflict of Interest Information: Financialsupport for the study was provided by Baylis Medicalto cover coordinator time, administrative costs, andstudy treatments. Study equipment was provided atno cost. Treatments were provided to patients at nocost.

No direct compensation was given to the physiciansor staff who performed these procedures. No conflictsof interest are noted by participating study physiciansor staff.

Abstract

Objective. The objective of this study was tocompare the efficacy of lateral branch neurotomyusing cooled radiofrequency to a sham interventionfor sacroiliac joint pain.

Design. Fifty-one subjects were randomized on a2:1 basis to lateral branch neurotomy and shamgroups, respectively. Follow-ups were conducted at1, 3, 6, and 9 months. Subjects and coordinatorswere blinded to randomization until 3 months. Shamsubjects were allowed to crossover to lateral branchneurotomy after 3 months.

Subjects. Subjects 18–88 years of age had chronic(>6 months) axial back pain and positive responseto dual lateral branch blocks.

Interventions. Lateral branch neurotomy involvedthe use of cooled radiofrequency electrodes to

ablate the S1–S3 lateral branches and the L5 dorsalramus. The sham procedure was identical to theactive treatment, except that radiofrequency energywas not delivered.

Outcome Measures. The principal outcome mea-sures were pain (numerical rating scale, SF-36BP),physical function (SF-36PF), disability (Oswestrydisability index), quality of life (assessment ofquality of life), and treatment success.

Results. Statistically significant changes in pain,physical function, disability, and quality of life werefound at 3-month follow-up, with all changes favor-ing the lateral branch neurotomy group. At 3-monthfollow-up, 47% of treated patients and 12% of shamsubjects achieved treatment success. At 6 and 9months, respectively, 38% and 59% of treated sub-jects achieved treatment success.

Conclusions. The treatment group showed signifi-cant improvements in pain, disability, physical func-tion, and quality of life as compared with the shamgroup. The duration and magnitude of relief wasconsistent with previous studies, with current resultsshowing benefits extending beyond 9 months.

Key Words. Sacroiliac; Pain; Radiofrequency;Ablation; Neurotomy; Lateral

Introduction

The sacroiliac joint (SIJ) has the requisite innervation tobe a potential source of low back pain [1–4]. Studies havesuggested that approximately 15% of undiagnosedchronic axial low back pain may originate from the SIJcomplex [5–7]. The prevalence is higher in patients withlow back pain after lumbar fusion procedures, with ratesas high as 32% and 43% [8–10]. The condition alsoappears to be more common in older patients [7]. Treat-ment options include conservative management andinjections with local anesthetic and corticosteroids. Con-servative management, including physiotherapy and chi-ropractic, has yet to be evaluated in a controlled study onsubjects with injection-confirmed SIJ pain [11]. Controlledstudies on intra-articular injections have demonstratedmoderate- to long-term pain relief in some subjects, butno studies have provided a high level of evidence [12–14].Periarticular injections have been shown to provide go

Pain Medicine 2012; 13: 383–398Wiley Periodicals, Inc.

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od short-term relief in controlled studies, highlighting therole of extra-articular sources of pain [14–16]. SIJ fusionhas been suggested as a treatment alternative in patientswith pelvic rim disruption, but high level of evidence for thisprocedure has yet to emerge.

In recent years, there has been a growing interest in theuse of radiofrequency (RF) to treat low back pain stem-ming from the SIJ. A number of retrospective and pro-spective case series have reported largely positive results[17–24]. Treatment techniques and study outcomes,however, have varied across these studies with a lackof consensus on best practices. Earlier studies usedmonopolar, thermal RF, but more recent studies have usedwhat is referred to as cooled RF, in which electrodes areinternally cooled to produce larger thermal lesions[22,24,25]. These studies hypothesized that larger lesionscompensate for the variability in location of the targetlateral branches. A controlled study that used cooled RFto target the L5 dorsal ramus and the lateral branches ofthe S1–S3 dorsal foramina reported treatment success in64% and 57% of patients at 3 and 6 months, respectively,with some subjects continuing to experience relief beyond1 year [25]. A subsequent study analyzed demographicand clinical variables of a cohort of patients who receivedlateral branch neurotomy and revealed that using cooledRF, but not monopolar RF, was the only positive predictivefactor for treatment success [26].

Although the previous controlled study of lateral branchRF neurotomy reported successful outcomes, its samplesize was small, and its results have not been replicated[25]. The present study was, therefore, undertaken tocompare the outcomes of cooled RF and placebo in alarger group of patients.

Methods

This study was conducted in a private practice pain man-agement department of an ambulatory center. Approvalfor this study was obtained from the Patient AdvocacyCouncil Institutional Review Board (Mobile, AL, USA).

Study Design

To detect a significant difference in pain reductionbetween the groups, power calculations determined theneed for 51 subjects in this study, with 34 subjects in thetreatment group and 17 in the sham group, according toa 2:1 randomization scheme (a = 0.05; b = 0.1). Thissample size was derived using an expected reduction of3.5 on the numerical rating scale (NRS) for pain in thetreatment group and a reduction of 1.0 in the controlgroup. These estimates of treatment and sham effectswere based, respectively, on controlled studies by Cohenet al. and Pauza et al. [25,27].

Recruitment and Screening

Patients in this study were recruited between July 2008and July 2010. They were recruited from the practice of

the senior author, from colleagues, and via advertisementsin local print media. An initial phone interview was con-ducted for individuals responding to advertisements todetermine appropriateness for study. Individuals deemedappropriate via telephone interview and those referred byother physicians then underwent in-person screening withstudy coordinators and physicians. No financial induce-ments were provided for participation in the study.

The inclusion criteria were as follows: predominantlyaxial pain below the L5 vertebrae; axial pain lasting longerthan 6 months; 3-day average NRS between 4 and 8;age greater than 18 years; failure to achieve adequateimprovement with comprehensive non-operative treat-ments, including but not limited to activity alteration, non-steroidal anti-inflammatory, physical and/or manualtherapy, and fluoroscopically guided injections of steroidsinto the SIJ or sacroiliac ligaments; other possible sourcesof low back pain reasonably excluded (by means ofphysical exam, medical history, and magnetic resonanceimaging/computed tomography/X-ray as required),including but not limited to bone fractures, the hip joint,symptomatic spondylolisthesis, tumor, and other regionalsoft tissue structures. Patients with history of potentiallyconfounding intervertebral disc disease or zygapophysealjoint pain were excluded, but discography and/or medialbranch blocks were not uniformly used to screen for theseconditions. The exclusion criteria were as follows: aBeck’s Depression Inventory score of greater than 20;irreversible psychological barriers to recovery; spinalpathology that may impede recovery such as spondylolis-thesis at L5/S1, or scoliosis; symptomatic moderateor severe foraminal or central canal stenosis; systemicinfection or localized infection at anticipated introducerentry site; concomitant cervical or thoracic pain greaterthan 2/10 on a NRS scale; uncontrolled or acute ill-ness; chronic severe conditions such as rheumatoid/inflammatory arthritis; pregnancy; active radicular pain;immunosuppression (e.g., AIDS, cancer, diabetes, surgery<3 months ago); worker’s compensation, injury litigation,or disability remuneration; allergy to injectates or medica-tions used in the procedure; high narcotics use (>30 mgmorphine daily or equivalent); active smokers (terminationfor at least 6 months with no smoking during follow-upperiod were acceptable with caution); subject unwilling-ness to consent to the study.

Subjects meeting all the aforementioned criteria werethen screened with two sets of anesthetic blocks. Theblocks were performed on the symptomatic side. Patientswith bilateral symptoms were blocked bilaterally. First,the lateral branches of S1–S3 were blocked using thefollowing method. Using C-arm fluoroscopy, an anterior-posterior image through the L5-S1 disc space wasobtained. The C-arm was tilted sufficiently to visualize theposterior sacral foramina at S1, S2, and S3. Once visual-ized, 25G spinal needles were advanced to the surfaceof the sacrum 3–10 mm lateral to each posterior sacralforamen. Needle positions at the S1–S3 levels corre-sponded to the 3:00 position on a clock face on the rightside and the 9:00 position on the left side. A lateral image

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was checked to confirm appropriate depth of placementon the sacral surface. After confirming needle placement,0.5 cc of 0.5% bupivacaine was injected at each level.The dorsal ramus of L5 was then blocked as described inthe ISIS practice guidelines [28]. After confirming needleplacement in the notch between the sacral ala and the S1superior articular process, 0.5 cc of 0.5% bupivacainewas injected. Volumes did not exceed 2 cc total for uni-lateral injections and 4 cc total for bilateral injections. Cor-ticosteroids were not administered as part of thediagnostic blocks. Subjects were not given any sedation(including oral sedation) and encouraged not to take anypain medication around the time of the diagnostic block inan attempt to allow for more accurate assessment ofrelief. To be considered as having a positive response tothe block, subjects were required to have greater or equalto 75% relief of their index pain for between 4 hours and7 days following the injections. This blocking protocol wasrepeated on a separate day, after a return to baseline pain.Subjects achieving 75% relief of their index pain after bothblocks were required to return to baseline pain beforeentry into the study.

Randomization and Primary Treatment

At enrollment, a baseline evaluation of all subjects wascompleted, and subjects were randomized on a 2:1 basisto either the treatment group or the sham group usingpre-sealed envelopes given by a nurse not involved in thestudy. Procedures were completed within 60 days ofenrollment. Both treatment and sham procedures wereperformed in a fluoroscopy suite equipped with a C-arm.Preceding both treatment and sham procedures, patientsreceived local anesthetic and moderate sedation. Underthe supervision of a board certified anesthesiologist andCRNA, patients were placed on a low-dose continuouspropofol infusion with or without opioid and benzodiaz-epine supplementation at the discretion of the anesthesiateam. Patients remained communicative throughout theprocedure. At this time, the randomization code wasrevealed to the machine operator and physician. The gen-erator operator controlled whether RF energy was appliedto the patient. The equipment arrangement in the fluoros-copy suite allowed physicians to view the generatorscreen during the procedure and thereby gain knowledgeof group assignment. Thus, physician blinding was notpossible. The patient remained visually isolated from theequipment and was exposed to typical equipment noisesregardless of treatment group. To further ensure blinding,the patient was kept out of contact with other studysubjects postoperatively. Those subjects who received RFwere thereby classified as “treatment” subjects, and thosewho did not receive RF were classified as “sham”subjects.

The following technical description is applicable to bothtreatment and sham procedures, except that RF energywas not delivered to sham subjects. Probe placements,procedure duration, equipment sounds, and visual indica-tions to the patients in both groups were identical.

First, the L5 dorsal ramus was lesioned with a cooled RFSInergy probe (Kimberly Clark Health Care, Roswell, GA,USA) in the following manner. The patient was placed inthe prone position and the target anatomy for electrodeplacement was identified using C-arm fluoroscopy. First,an anterior-posterior view was obtained by imagingthrough the L5-S1 disc space. The C-arm was thenrotated obliquely 20°–30° such that the junction betweenthe S1 superior articular process and the sacral ala wasvisualized. The specific bony target for needle placementwas the notch between these two bones, just inferior tothe cranial-caudal midline of the notch. The introducerwas advanced “down the beam” until bone contact at thetarget. A lateral view confirmed that the tip of the styletwas no deeper than the mid aspect of the superior articu-lar process (SAP). The stylet was removed from the intro-ducer and was replaced with the SInergy Probe (KimberlyClark Health Care). A lateral view confirmed the tip of theprobe to be 2 mm proximal to the tip position previouslyobserved with the stylet, which allowed for distal projec-tion of the lesion. Once accurate electrode placement wasconfirmed, 0.5 cc of 2% lidocaine and 0.5 cc of 0.75%bupivacaine was injected through the introducer to reducediscomfort and ensure blinding. RF energy was thenapplied for 150 seconds, at a set temperature of 60°Cusing a Pain Management Radiofrequency Generator(Kimberly Clark Health Care). During RF delivery, subjectswere monitored for any new symptoms and pain in thegroin, thigh, lower leg, or foot.

After coagulation of the L5 dorsal ramus, the sacral lateralbranches of S1, S2, and S3 were targeted. C-arm fluo-roscopy was used to visualize through the L5/S1 discspace. The C-arm was then tilted until the S1, S2, and S3posterior sacral foramina were successively visualized.Using this imaging strategy, 27-gauge 3.5-in. Quinckeneedles were placed at the lateral margins of the S1, S2,and S3 posterior sacral foramina in order to obtain amore definitive localization of these structures via tactilefeedback.

The first bony target for electrode placement was a point7 mm lateral to the 27-gauge needle at the lateral marginof the S1 posterior sacral foramen. Prior to skin puncture,the area over the target entry point was infiltrated with 1%lidocaine. An introducer with stylet was then advancedthrough the skin and overlying tissue until contact wasmade with the target point on the sacrum. A stainless steelruler (Epsilon Ruler, Kimberly Clark Health Care) was usedto measure the distance between the posterior sacralforamen and the introducer. The stylet was then replacedwith the 17-gauge, 75-mm cooled electrode with 4-mmactive tip (Kimberly Clark Health Care), which, being 2 mmshorter than the stylet, came to a final position of 2 mmfrom the surface of the sacrum. A lateral fluoroscopicimage confirmed that the RF probe was not within thesacral canal. Impedance was then confirmed to bebetween 100 and 500 W; if outside this range, the elec-trode was repositioned slightly by reintroducing the styletand slightly altering the location of the introducer. RFenergy was then delivered for 150 seconds, at a set

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temperature of 60°C. In order to form an arc-shaped wallof heated tissue lateral to the S1 posterior sacral foramen,two additional lesions were created at that level. Afterremoving the electrode and reinserting the stylet, the intro-ducer was angled cranially and medially to a bony target7 mm from the first lesion target. The epsilon ruler wasused to judge distance between targets, and the lateraledge of the posterior sacral foramen. After applying RF tocreate the second lesion, the introducer was angled cau-dally to a position 7 mm inferior from the first target. RFwas applied to create the third lesion and complete thethermo-coagulation blockade of the lateral branches atS1. The same method was used to lesion lateral to the S2and S3 posterior sacral foramina; however, only twolesions were created lateral to S3. For reference, right-sided S1 and S2 lesions corresponded to 2:30, 4:00, and5:30 positions on the face of a clock; left-sided S1 and S2lesions corresponded to 6:30, 8:00, and 9:30 on the faceof a clock. For S3, right-sided lesions corresponded to1:30 and 3:00 on a clock face, and left-sided lesionscorresponded to 9:00 and 10:30. Subjects requiring bilat-eral treatment received contralateral RF treatment duringthe same procedural session. Post-lesioning, 1 cc of a 1:1mixture of 2% lidocaine and 0.75% bupivacaine was givenat each level to control pain in the immediate postopera-tive period.

Subjects were prescribed analgesics for postoperativepain. Activity was avoided the day of the procedure, andexcessive activity was avoided for 1–3 days following theprocedure. Subjects remained out of contact with anyoneprivy to randomization details.

Outcome Measures and Follow-Up

Patient reported outcomes for pain, physical function, dis-ability, global perceived effect (GPE), and quality of lifewere obtained using a number of instruments. A NRS wasused to assess pain. The Oswestry disability index (ODI)was used to assess disability. The Short Form SF-36(version 1) was used to assess bodily pain and physicalfunction using the respective subscales: SF-36BP andSF-36PF. Quality of life was measured using the Assess-ment of Quality of Life (AQoL) assessment tool. GPE wasmeasured by having subjects rate their index pain on a7-item scale with the following options: pain is completelygone; pain has decreased a lot; pain has decreased; painis the same; pain has increased; pain has increased a lot;and pain is the worst possible. To assess blinding, patientswere asked post-procedure if they believed active treat-ment had been received. All questionnaires were admin-istered by a study coordinator blinded to subjectrandomization. Physicians involved in performing proce-dures were not involved in follow-up patient visits. Sub-jects in the treatment group were scored with theseinstruments at baseline and at 1-, 3-, 6-, and 9-monthpost-procedure. Subjects in the sham group were scoredat baseline and post-procedure at 1 and 3 months.

Both assessors and subjects were blinded to randomiza-tion at the 1-month and 3-month follow-up time-points.

Unblinding occurred after 3-month follow-up data werecollected. After unblinding at 3-months, subjects in thesham group were offered RF lateral branch neurotomyand those who opted to crossover were followed-up at 1,3, and 6 months. Subjects who crossed-over from thesham group to receive lateral branch neurotomy werereferred to as “crossover” subjects.

Statistical Measures and Study Endpoints

Means and standard deviations were calculated for con-tinuous variables and compared with t-tests. For cate-gorical variables, data were summarized in frequency dis-tributions and compared with Fisher’s exact test. Resultsfor proportions are reported hereafter as percentages,followed by confidence intervals calculated at the 95%level. Statistical significance was considered to beP < 0.05.

The primary endpoint in this study was the comparison ofmean change from baseline in NRS between treatmentand sham groups at the 3-month follow-up time-point.Secondary endpoints in this study included comparison ofmean changes from baseline between treatment andsham groups in ODI, SF-36BP, and SF-36PF. The propor-tions of subjects demonstrating a successful response totreatment were compared between groups, with treat-ment success defined as a �50% decrease in NRS painscore corroborated by one of the following: 1) a 10-pointincrease (improvement) in SF-36BP or 2) a 10-pointdecrease (improvement) in ODI. Other secondary end-points were GPE and comparison of mean quality of life(AQoL). For subjects who dropped out of the study afterthe 3-month time-point, the last-observation carried-forward method of data imputation was used to calculatesubsequent results. Subjects who did not complete abaseline outcome questionnaire for an outcome tool wereexcluded from mean change analysis at subsequent time-points for that outcome; this applied to three subjects forSF-36PF, two subjects for SF-36BP, four subjects for ODI,and four subjects for AQoL. The crossover group was notcompared with the treatment or sham groups as the studywas not designed to make such comparisons: crossoversubjects received treatment with lateral branch neurotomyin an unblinded manner, as opposed to the original treat-ment group that received the procedure in a blindedmanner. This also precluded the combination of data fromthe treatment and crossover groups.

Results

Demographics and Complications

There were 304 patients screened by telephone andin-clinic for inclusion in this study (Figure 1). Two hundredfifty-three individuals were excluded from participation fora multitude of reasons: 153 did not meet the clinicalinclusion criteria, 97 declined to be randomized or complywith protocol, 2 did not report for randomization, and 1died before randomization. Fifty-one subjects were

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deemed eligible, consented, and randomized in the study.After randomization, 34 subjects were allocated to thetreatment group and 17 to the sham group. All enrolledsubjects participated in the study until the unblinding at 3months. Seven treatment subjects dropped out of thestudy after the 3-month follow-up, and an additional twodropped out after the 6-month follow-up. One shamsubject chose not to crossover to receive lateral branchneurotomy.

In the treatment and sham groups, respectively, 64% (47–82%) and 56% (32–81%) of subjects were able to accu-rately guess which procedure they received (P = 0.584).Blinding was satisfactory as these rates were not signifi-cantly different from chance.

No serious complications were reported for the 50 lateralbranch neurotomy procedures or for the 17 sham proce-dures completed during this study. A small proportion of

Figure 1 Chart showing progression of a randomized, placebo-controlled trial of lateral branch neurotomyusing cooled radiofrequency for sacroiliac joint mediated low back pain.

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subjects reported soreness or numbness at the introducersites in the 2 weeks following treatment. One subjectdeveloped shingles at the introducer site, but this wasdeemed unrelated to the treatment.

Analysis of demographic characteristics and clinical fea-tures recorded at baseline revealed no statistically signifi-cant differences between the two groups (Table 1). Also,

no statistically significant differences were found betweenbaseline values of outcome measures (Table 2).

Pain, Physical Function, and Disability

The mean change from baseline in pain, physical func-tion, and disability outcomes are reported in Table 3 fortreatment and sham groups at each time-point. Mean

Table 1 Demographic characteristics and clinical features recorded at baseline of patients randomizedto lateral branch neurotomy or sham study groups

Feature

Lateral Branch Neurotomy(N = 34) Sham (N = 17)

P Value*N % N %

Male 11 32 3 18 0.334Female 23 68 14 82Age (mean � SD), years 56 � 15

(range: 18–88)64 � 14

(range: 43–84)0.087

Work status:Unemployed because of back pain 1 3 1 6 0.259Unemployed not because of back pain 11 32 9 53Working 22 65 7 41

Duration of pain6–12 months 6 18 1 6 0.58412–24 months 5 15 3 18>24 months 22 65 13 77Missing 1 3 0 0

Previous treatmentPhysiotherapy 7 21 2 12 0.699Bed rest 5 15 3 18 1.000Anti-inflammatory drugs 23 68 11 65 1.000Opioids 12 35 11 65 0.073Injections 14 41 7 41 1.000Chiropractics 8 24 3 18 0.731

Referred painIn buttock 23 68 13 77 0.746In thigh 11 32 9 53 0.225In leg 9 27 6 35 0.532

*0.05; SD = standard deviation.

Table 2 Baseline outcome measures of patients randomized to lateral branch neurotomy or sham studygroups

Outcome Measure

Lateral Branch Neurotomy Sham

P ValueMean SD Mean SD

NRS for pain (0–10) 6.1 (N = 34) 1.3 5.8 (N = 17) 1.3 0.370SF-36 (0–100)

SF-36 bodily pain 40 (N = 33) 15 43 (N = 16) 10 0.525SF-36 physical functioning 50 (N = 32) 20 47 (N = 16) 24 0.707

Oswestry disability scale (0–100) 37 (N = 32) 14 35 (N = 15) 10 0.639AQoL 0.60 (N = 33) 0.19 0.54 (N = 14) 0.16 0.346

AQoL = Assessment of Quality of Life; NRS = numerical rating scale; SD = standard deviation.

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improvement in NRS pain score at the 3-month time-pointfor the treatment group was significantly greater than thatfor the sham group. The treatment group achieved asignificantly greater improvement in SF-36BP at the 1-and 3-month time-points. The treatment group achieved asignificantly greater improvement in SF-36PF at the3-month time-point. The treatment group achieved a sig-nificantly greater improvement in ODI at the 1- and3-month time-points. Individual NRS, SF-36BP, ODI, andSF-36PF outcomes at 3-month follow-up are shown inFigure 2. The distribution of outcome states for all treat-ment subjects is shown in Figure 3.

To evaluate the proportion of patients who achieved aclinically meaningful outcome, treatment success wasdefined as a �50% NRS decrease corroborated by one ofthe following: 1) a 10-point increase in SF-36BP or 2) a10-point decrease in ODI. Sixteen out of 34 treatmentsubjects (47%; 30–65%) and 2 out of 17 sham subjects(12%; 1–36%) met the definition of treatment success at 3months (P = 0.015; Figure 4). The NRS, ODI, SF36-BP,and SF36-PF outcomes for each patient are presented inFigure 2. At 6 and 9 months, respectively, 13 out of 34(38%; 22–56%) and 20 out of 34 (59%; 41–75%) treat-ment subjects had successful outcomes. Treatmentsuccess in subjects who crossed over from sham to lateralbranch neurotomy was observed in 7 out of 16 subjects(44%; 20–70%) at both 3 and 6 months.

Global Perceived Effect

In the current study, a GPE score was considered positiveif the subject rated GPE as “pain has decreased a lot,” or“pain is completely gone.” At the 3-month time-point,47% (29–65%) of treatment subjects had a positive GPEresponse, with 25% of subjects specifying “pain hasdecreased a lot” and 22% of subjects specifying “pain iscompletely gone” (Table 4). At the 6-month time-point,45% (28–64%) of treatment subjects had a positive GPEresponse, with 27% of subjects specifying “pain hasdecreased a lot” and 18% of subjects specifying “pain iscompletely gone.” At the 9-month time-point, 67% (48–82%) of treatment subjects had a positive GPE response,with 52% of subjects specifying “pain has decreased a lot”and 15% of subjects specifying “pain is completely gone.”In the sham group, at the 3-month follow-up time-point,8% (0–36%) of subjects had a positive GPE response,with 8% of subjects specifying “pain has decreased a lot”and no subjects specifying “pain is completely gone.” Asignificantly greater proportion of subjects in the treatmentgroup reported a positive GPE response at 3 months, ascompared with the sham group (P = 0.017). After cross-over to lateral branch neurotomy, at the 3-month time-point, 50% (23–77%) of subjects had a positive GPEresponse, with 36% of subjects specifying “pain hasdecreased a lot” and 14% of subjects specifying “pain iscompletely gone” (Table 4). At the 6-month time-point,

Table 3 Pain, physical function, and disability outcomes of subjects who received lateral branchneurotomy or sham procedures

Outcome Measure

Treatment Sham

P ValueMean SD Mean SD

NRS for pain (0–10) (N = 34) (N = 17)1-month change -2.7 2.6 -1.7 2.0 0.1603-month change -2.4 2.7 -0.8 2.4 0.0356-month change -2.5 2.6 — — —9-month change -2.7 2.7 — — —

SF-36 bodily pain (0–100) (N = 33) (N = 16)1-month change 15 17 2 11 0.0063-month change 16 26 -1 13 0.0196-month change 14 22 — — —9-month change 20 23 — — —

SF-36 physical functioning (0–100) (N = 32) (N = 16)1-month change 10 17 5 12 0.2383-month change 14 19 3 12 0.0406-month change 14 23 — — —9-month change 18 21 — — —

Oswestry disability scale (0–100) (N = 32) (N = 15)1-month change -12 14 -4 11 0.0463-month change -11 17 2 6 0.0116-month change -13 16 — — —9-month change -15 16 — — —

NRS = numerical rating scale; SD = standard deviation.Note: Improvements in numerical rating scale and Oswestry disability index scores manifest as decreases, and improvements inSF-36BP and SF-36PF manifest as increases.

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Figure 4 Percent of subjects meeting criteria for successful treatment response, by time-point and studygroup. Whiskers represent the 95% confidence interval. *Statistically significant difference at 0.05 level. Note:Treatment success defined as a �50% decrease in numerical rating scale plus one of 10-point increase inSF-36BP or 10-point decrease in Oswestry disability index.

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47% (21–73%) of crossover subjects had a positive GPEresponse, with 40% of subjects specifying “pain hasdecreased a lot” and 7% of subjects specifying “pain iscompletely gone.”

Quality of Life

The mean AQoL scores for treatment and sham subjectswere not significantly different at baseline: 0.60 � 0.19 fortreatment subjects vs 0.54 � 0.16 for sham subjects(P = 0.346). At 3 months, however, a significant differencein mean AQoL scores was detected between treat-ment (0.69 � 0.21) and sham subjects (0.56 � 0.21;P = 0.048). The mean AQoL scores for each time-pointare shown graphically in Figure 5, with results stratified bystudy group.

Discussion

The results of this study demonstrate that among subjectswith chronic low back pain stemming from the SIJ, lateralbranch neurotomy affects a significantly greater pain

reduction from baseline compared with a sham treatment.Treatment subjects achieved a mean NRS decrease of2.4, while sham subjects experienced a mean reduction of0.8 (P = 0.035). The effectiveness of the treatment proce-dure is supported by statistically significant differences indisability and physical function improvements betweengroups at 3-month follow-up. This result indicates thatlateral branch neurotomy with cooled RF is not a shamprocedure, corroborating the results of Cohen et al. [25].

For a more thorough assessment of clinical utility, it isuseful to consider the proportion of patients that demon-strated a clinically significant outcome. A review ofFigure 2, which illustrates changes in outcomes for eachpatient, suggests that there was a bimodal response tolateral branch neurotomy. This bimodal response ismasked if mean changes in outcomes are considered inisolation. Examination of the study data against a com-posite definition of treatment success allowed forresponders and nonresponders to be delineated, and thusfor the clinical relevance of treatment effects to be moreeffectively examined. To further assess the clinical rel-evance of treatment effects, a graphic representation ofabsolute patient outcome states is provided in Figure 3.Following treatment with lateral branch neurotomy, there isan increase in the proportion of patients occupying more-healthy outcome states. The magnitude of this change isostensibly due to improvements in health experienced bythe responder group identified in Figure 2.

Among treatment subjects, 16 out of 34 were categorizedas responders at the primary endpoint of 3 months, vs twosubjects in the sham group. This difference in responderrates between those receiving active and sham proce-dures is statistically significant and supports the afore-mentioned finding of a legitimate, non-placebo treatmenteffect from lateral branch neurotomy. The responder ratewas consistent between the treatment group (47%) and

Table 4 Percent of subjects reporting a positiveglobal perceived effect, by study group andtime-point

Treatment Sham Crossover

3 months 47% (29–65%)* 8% (0–36%)* 50% (23–77%)6 months 45% (28–64%) N/A 47% (21–73%)9 months 67% (48–82%) N/A N/A

* P < 0.05 comparing treatment and sham groups.Note: A positive global perceived effect was defined as patientsreporting their pain as “decreased a lot” or “completely gone.”

Figure 5 Mean Assessment ofQuality of Life (AQoL) scores bytime-point, with subjects strati-fied by study group. Whiskersrepresent standard deviation.* P < 0.05 comparing meansbetween treatment and shamgroups. (Note: Treatment andsham groups were blinded until 3months, and crossover groupwas non-blinded at all time-points.)

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the crossover group (44%) at 3 months, with both thecomposite variable of success and the GPE data indicat-ing that approximately half of the treated subjects in thecurrent study population had a successful response tolateral branch neurotomy. This finding should help preventprevious descriptive studies of lateral branch neurotomyusing cooled probes, which reported largely positiveresults, from being dismissed as merely depicting placeboeffects [22,24,26,29].

The treatment success rates derived from the compositevariable correlated well with patient GPE scores, and inthe author’s opinion accurately represent the proportion ofpatients who achieved meaningful improvements.Figure 2 is designed to allow readers to evaluate treatmentsuccess against alternative composite success criteria.

Based on the treatment responder rates observed at theprimary endpoint (3 months) in the current study, thenumber needed to treat (NNT) to get a successfuloutcome with lateral branch neurotomy is 3 (95% CI, 2–8).A NNT of 2–4 is indicative of an effective treatment [30].While the NNT calculated herein comes from a singlerandomized controlled trial, it does provide a promisingindication of what success rates practitioners may expectwhen using lateral branch neurotomy in carefully selectedpatients with chronic SIJ pain.

Studies of spinal neuroablative procedures have reportedpain relief of approximately 9–12 months in duration, withsome subjects ostensibly achieving permanent relief[31–33]. The outcomes in the current study suggest thatthe durability of lateral branch neurotomy is consistentwith these procedures. At the 9-month time-point, 20 outof 34 subjects (59%; 41–75%) were categorized asresponders. This was higher than the responder rate at 6months at which point 13 out of 34 (38%; 22–56%) treat-ment subjects reported a successful outcome. Thesuccess rate at 6 months may be artificially low due to onesubject who had a pain flare-up, which was resolved by 9months, and another subject who did not meet the sec-ondary outcome requirements for treatment success at 6months but did so at 3 and 9 months. Furthermore, twopatients were identified as having gradual improvementsin outcomes across time, but not meeting the compositecriteria for treatment success until 9 months. An additionalsubject had a discectomy and fusion of the cervical spineat 3 months and revision surgery at 6 months followingcomplications, with treatment effects from lateral branchneurotomy ostensibly masked until 9 months when thetreatment success criteria were met. Overall, these datasuggest that treatment effects seen at 3 months weredurable at 9 months. The data do not indicate how longthese effects will last, but treatment success has beenreported to last beyond 12 months in some subjects [25].The proposed mechanism by which pain returns is thenatural regeneration of ablated nociceptive nervous tissue.It is possible that treatment responders who have a returnof pain would be amenable to repeat RF lesioning, as hasbeen demonstrated in the literature for the treatment oflumbar facet joint pain with RF neurotomy [34].

Three data imputation methods were compared in theanalysis of the current data: complete-case analysis,worst-case analysis, and last-observation carried-forward.The complete-case analysis gave the least conservativeassessment of the data and was disregarded. The worst-case analysis, which assumed that all treatment subjectswere failures, showed that treatment success wasachieved in 35% (19–51%) of treatment subjects at 6months, and 56% (39–73%) of treatment subjects at 9months. These success rates did not differ significantlyfrom those collected under the last-observation carried-forward imputation method: 38% (22–56%) of treatmentsubjects achieved success at 6 months, and 59% (41–75%) of treatment subjects achieved success at 9months. Imputation methods which presume lack-of-effect have been criticized in the literature for penalizingstudies for drop-out subjects [35]. This criticism wasreflected by at least one subject in the current study whowas showing a robust treatment response across all out-comes at 3 months, but had to leave the study shortlythereafter to receive epidural steroid injections for a sepa-rate pain generator. Therefore, the last-observationcarried-forward data imputation technique was used forthe seven subjects who dropped from the current studyafter 3-month follow-up and for the two subjects whodropped after 6 months. This method appears to providea representative means of imputation for this data set;however, the worst-case analysis is also provided forreader consideration.

Subjects and assessors were unblinded after data collec-tion at the 3-month time-point. Results of other prospec-tive studies have shown that the majority of subjectsreceiving sham neurotomy treatments will report theabsence of relief by 3-month follow-up [25,31]. This isconsistent with the current results as 16 out of 17 shamsubjects chose to crossover to receive lateral branch neu-rotomy (one sham subject left the study after completing 3months in the sham group). It was assumed that havingpatients blinded for a longer period of time could increasethe likelihood of noncompliance at follow-up evaluationand encourage the pursuit of other treatments outside ofthe study.

The current study suggests that roughly half of the treatedsubjects (both in the treatment group and those in thesham group who crossed over to receive lateral branchneurotomy) had a successful response to treatment.There are several likely reasons why the remaining sub-jects did not achieve treatment success. First, the diag-nostics blocks did not require a complete resolution ofpain, but only �75% relief. Therefore, it could be expectedthat some patients would achieve only incomplete relieffrom RF lateral branch neurotomy. Second, the blockingparadigm used for patient selection did not include aplacebo control, which raises the possibility that subjectsexhibiting a placebo response to anesthetic injectionsentered the study. Third, several subjects nonresponsiveto treatment had a secondary, previously unidentified paingenerator with a pain map overlapping that of SIJ pain.The reliance on medical history to screen for subjects with

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discogenic pain or facetogenic pain, without the use ofadditional specific tests such as discography or medialbranch blocks, was a shortcoming of this study. Additionalexamples of secondary pain generators observed duringfollow-up in treatment nonresponders in the current studywere as follows: discectomy with fusion at C3 vertebrae,followed by subsequent complications from instrumenta-tion necessitating eventual removal; bilateral osteoarthriticknee pain; development of contralateral SIJ pain afterunilateral treatment; hip pain necessitating steroid injec-tions and eventual hip replacement; and development ofpainful shingles at treatment introducer site. The likelihoodof presenting with a secondary pain generator increases inthe elderly as aging of the body leads to an increasedprevalence of pain-generating conditions. In the currentstudy, 39% of subjects were between 60 and 90 years ofage, and an additional 39% were between 50 and 59. Afourth potential explanation for the lack of treatmentsuccess among nonresponders is the possibility of ventralinnervation of the SIJ, which is not targeted by the lateralbranch neurotomy procedure. Recent evidence has con-firmed the existence of ventral innervation of the SIJ bydistension of the joint to elicit pain following blockade ofthe extra-articular dorsal innervation [36]. This explanation,however, should be abrogated by the current use of adiagnostic blocking technique that selects exclusively fordorsal SIJ pain. Future study results could be improved byusing a diagnostic block that more closely replicates thelesioning targets of the current lateral branch neurotomytechnique [36]. Finally, treatment failure can be due toincomplete denervation of the dorsal innervations due totechnical or procedural variability.

In the current study, sham treatment mimicked the actualtreatment in all respects, except that there was no deliveryof RF energy. Thus, the significantly better outcomesobserved in the treatment group, as compared with thesham group, suggest that the delivery of RF energy toposterior afferent nociceptive pathways has the ability todisrupt pain signaling from the SIJ complex.

The procedural technique targets the S1–S3 lateralbranches and the L5 dorsal ramus, which together com-prise the known dorsal innervations of the SIJ [1–4,19].

While the location of the L5 dorsal ramus maintains aconsistent relationship with the surrounding bony land-marks, a central challenge of this procedural technique isto compensate for the inconsistent location of the sacrallateral branches. There exists patient-to-patient and level-to-level variability in both the number and the location ofthe lateral branches along the posterior sacrum[19,37,38]. Previous studies evaluating lateral branch neu-rotomy using cooled RF have hypothesized that largerlesions could compensate for this variability in lateralbranch location [22,24,25]. Procedurally, this is accom-plished by overlapping the thermal lesions to create con-fluent “strips” of lesioned tissue lateral to the S1, S2, andS3 posterior sacral foramina. The specific lesion targetsaround each of the foramina are a geometric conse-quence of the lesion size and the known variability of thelateral branches.

Internally cooled RF electrodes were introduced in the1990s for tumor ablation and cardiac ablation [39–41].They were developed to increase the maximum volume oftissue ablation attainable by a monopolar RF electrode[39]. The fundamental premise of the cooled RF electrodeis that a circulating coolant will prevent the condition ofhigh impedance at the interface between the tissue andelectrode. This allows a higher RF output power and thusa larger volume lesion (Figure 6). The SInergy probe usedfor this study creates spherical lesions of 8–10 mm indiameter [25,42]. The utility of a larger, spherical lesion forelectrode placement perpendicular to bone is illustrated inFigure 7.

The meticulous positioning of large volume lesions aroundeach posterior sacral foramen in order to sever the afferentinput from the SIJ is a prerequisite to achieving successfuloutcomes for this procedure. A retrospective study byCohen et al. analyzed clinical and demographic variablesas predictors of lateral branch neurotomy success andfound cooled RF, as compared with conventional RF, to bethe only positive predictor of treatment success [26].

Lateral branch neurotomy using cooled RF has been rec-ommended as the treatment option for subjects who havefailed to achieve relief, or achieved only short-term relief,

Figure 6 The temperature pro-file of thermal radiofrequencyablation with and without internalcooling. Internal cooling allowsgreater energy deposition in thetissue, resulting in larger effectivelesion radius. The dashed linerepresents the 50°C isotherm,which is the effective lower limitfor nerve ablation. Adapted fromGoldberg et al. [44].

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from intra-articular SIJ injections [43]. This is the secondrandomized, controlled study evaluating lateral branchneurotomy for the treatment of low back pain stemmingfrom the SIJ to be conducted. The current results in thispatient population showed improvements in measures ofpain, disability, physical function, and quality of life. Thisstudy further supports the recommendation of cooled RFlateral branch neurotomy for persistent SIJ pain [43].

Acknowledgments

Thanks are due to Dr. Laura Ottaviani and Dr. RichardBundschu; Denise Dorman, RN and Head of ClinicalResearch; Deborah Bacon, RN and Research Coordina-tor; Andrea Mehalko, Research Coordinator; DianaBenitez, Certified Medical Assistant; The Coastal Ortho-pedics and Pain Management staff; The staff at the PointeWest and East Ambulatory Surgical Center; RadiologyTechnicians Mike and Venus; and The Anesthesia Teamsat Pointe West and the East Ambulatory Surgical Centers.

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