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Clinical Neurology and Neurosurgery 126 (2014) 11–17

Contents lists available at ScienceDirect

Clinical Neurology and Neurosurgery

jo ur nal home p age: www.elsev ier .com/ locate /c l ineuro

valuation of endoscopic dorsal ramus rhizotomy in managingacetogenic chronic low back pain

hen-Zhou Li ∗, Shu-Xun Hou, Wei-Lin Shang, Ke-Ran Song, Wen-Wen Wuepartment of Orthopedics Surgery, the First Affiliated Hospital of Chinese PLA General Hospital, Beijing, China

r t i c l e i n f o

rticle history:eceived 30 June 2014eceived in revised form 24 July 2014ccepted 9 August 2014vailable online 18 August 2014

eywords:hronic low back painumbar zygapophysial jointedial branch neurotomy

ndoscopehizotomy

a b s t r a c t

Objective: To study the effectiveness of surgical dorsal endoscopic rhizotomy for the treatment of faceto-genic chronic low back pain.Methods: From April 2011 to November 2011, 58 patients who were diagnosed with lumbar facetogenicchronic low back pain (CLBP) and thereafter experienced >80% reliefs of pain with two comparative lum-bar medial branch blocks were recruited in the study. Of those 58 patients, 45 cases (the operation group)received dorsal endoscopic rhizotomy, and the remaining 13 cases (the conservative group) received con-servative treatment. Patients’ preoperative and postoperative VAS score, percentage of pain relief and theMacNab score were analyzed and compared. Anatomic variations and any possible complications wererecorded.Results: In the operation group, VAS scores of pain (low back/referred) at any time point postoperativelywere significantly lower than that before MBB (P < 0.05), which, however, showed no significant differ-ence as compared to the scores after MBB (P > 0.05). In the conservative group, VAS scores of pain (lowback/referred) at any time point postoperatively with conservative treatment decreased significantlycompared with that before MBB (P < 0.05) and were significantly higher than that after MBB (P < 0.05).Percentage of pain relief in the operation group at any time point postoperatively were significantly

higher than that in the conservative group (P < 0.01). The MacNab scores of 1 year follow-up in the oper-ation group were higher than that in the conservative group. In addition, four separate newly identifiedanatomical variations of medial branch anatomy were observed and reported.Conclusion: Dorsal endoscopic rhizotomy is safe and effective for the facetogenic CLBP, and can achievebetter clinical outcome than the conservative treatment.

© 2014 Elsevier B.V. All rights reserved.

. Introduction

The lumbar facet or zygapophysial joints are paired diarthro-ial articulations between posterior elements of adjacent vertebrae1]. It consists of a distinct joint space capable of accommodatingetween 1 and 1.5 ml of fluid, a synovial membrane, hyaline carti-

age surfaces, and a fibrous capsule [2]. The facet joint capsule andhe surrounding structures are innervated [3]. Chemical or mechan-cal stimulation of the facet joints and their nerve supply may elicit

ack and/or leg pain [4]. Facet joints have been implicated as aource of chronic pain with an overall prevalence of 31% (circa.

∗ Corresponding author at: Department of Orthopedics Surgery, the First Affiliatedospital of Chinese PLA General Hospital, No. 51, Fucheng Road, Haidian District,eijing 100048, China. Tel.: +86 13601266970; fax: +86 10 85630233.

E-mail address: lizhenzhou88@126.com (Z.-Z. Li).

ttp://dx.doi.org/10.1016/j.clineuro.2014.08.014303-8467/© 2014 Elsevier B.V. All rights reserved.

21–41%) in a heterogeneous patient population with chronic lowback pain (CLBP) [5].

Chronic low back pain of facet joint origin may be managed byintra-articular lumbar facet joint injections [6,7], lumbar facet jointnerve blocks [8,9], and radiofrequency neurotomy [10,11]. How-ever, there have been disparities in the previous reports regardingthe varying outcome parameters of the different treatment modal-ities [3,12–15].

A recent narrative review by Bogduk [16] suggested that lumbarmedial branch neurotomy remains as the only effective treat-ment available for CLBP. The theoretical basis of neurotomy liesin the fact that facet joint surgery deadens the medial branchesand cuts off their afferent pathways which are the source of thechronic low back pain. A one-year follow-up study showed that

the effectiveness of percutaneous neurotomy of medial branches isonly 43–80%. Anatomical variations of the dorsal medial branchanatomy, incorrect placement of electrode, incomplete ablation,and nerve regeneration are important factors that should be taken

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nto account when deciding or moderating the effectiveness ofedial branch neurotomy. The aims of our study were to evalu-

te the effectiveness of dorsal endoscopic rhizotomy and comparet with the conservative treatment for the treatment of facetogenichronic low back pain with respect to VAS scores, percentage ofain relief, and MacNab scores.

. Methods

.1. Participants

This study was approved by the ethics committee of the Firstffiliated Hospital of PLA’s General Hospital (China), and written

nformed consent was obtained from all participants. From April011 to November 2011, 58 patients who were diagnosed as

umbar facetogenic chronic low back pain (CLBP) and registeredt the Department of Orthopedics Surgery of the First Affiliatedospital of PLA’s General Hospital were included in a prospective-year follow-up. The inclusion criteria were: (1) patients withhronic low back pain of at least 3 months’ duration, (2) patientsith mechanical low back pain especially elicited by movement

f torsion/rotation and from flexion to extension, (3) patients withpine diseases of degenerative lumbar instability, lumbar degen-rative spondylolisthesis, degenerative lumbar scoliosis, and/orumbar facet joint osteoarthritis, and (4) patients who experienced80% relief of pain with two comparative lumbar medial branchlocks (lidocaine and bupivacaine). The exclusion criteria were:1) patients with radicular pain (defined as neurological findings

f nerve root dysfunction), or with cauda equina syndrome and2) patients with a known specific etiology for low back pain suchs infection, tumor, or trauma. Considering referred pain, patientsan be divided into three groups: (1) patients whose pain was

ig. 1. Positioning the surgical points. (A) target point for dorsal endoscopic rhizotomy (TB, medial branch); (B) the skin entry point for dorsal endoscopic rhizotomy; (C) frontal

iew showing the puncture needle was docked into the dorsal region of the transverse pr

eurosurgery 126 (2014) 11–17

only in the lower back (group A); (2) patients whose pain waspredominantly in the low back, yet also radiated into the buttocksand legs (group B); and (3) patients whose pain was predominantlyin the low back, yet has vastly spread into the knee or even lower(group C).

The patients were randomly divided into two groups (each with45 and 13 cases, respectively), i.e., the operation group compris-ing of 45 cases received dorsal endoscopic rhizotomy, and theconservative group consisting of 13 cases received conservativetreatment, which includes non-steroidal anti-inflammatory drugs(NSAIDs), physical therapy and cognitive-behavioral therapy.

2.2. Operative technique

Patients were placed in the prone position on the table plat-form, and made sure that their lumbar kyphosis and abdomen notbe pressed. Local anesthesia (1 ml of 0.5% lidocaine) and mild seda-tion with fentanyl or midazolam were carried out. Surgical lociwere determined according to the scope of the medial branch blockwhich was performed under fluoroscopy. The target point is at thejunction of the base of superior articular processes (SAP) and thetransverse process (Fig. 1a and b). An 18-G needle was docked ontothe target point. The anteroposterior fluoroscopic view and the lat-eral view were obtained with the maximal exposure of the targetregions (Fig. 1c and d). Each target was injected with 2 ml of a mix-ture of contrast agents consisting of 1.6 ml of omnipaque and 0.4 mlof methylene blue. Then guide wire, soft tissue dilator and beveledworking cannula were serially inserted. After checking the proper

location of the cannula, forceps was used to remove the fatty tis-sue between muscles. RF probe was inserted through endoscope.Then, the soft tissue at base of the transverse process includingthe medial branch was removed in order to completely expose the

P, transerve process, AP, accessory process, MAL, mammillary-accessary ligament,view showing the puncture needle was docked into the target positions; (D) lateralocess.

Z.-Z. Li et al. / Clinical Neurology and Neurosurgery 126 (2014) 11–17 13

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predominantly performed at the zygapophyseal joint (L3-S1)(18 cases). Fig. 4 summarizes the distribution for the levels oftreatment.

Table 1Demographic characteristics.

Index Operation group Conservative group

Sex (male/female)-no. 25/20 6/7Age (years) 61.84 ± 11.77 62.62 ± 19.83VAS score of back pain 7.69 ± 1.06* 6.69 ± 0.75Duration of back pain (months) 137.13 ± 135.77* 48.23 ± 71.40VAS score of referred pain 5.41 ± 1.88* 4.17 ± 0.83Duration of referred pain (months) 19.92 ± 23.27 (37) 14.25 ± 23.37 (12)Type of referred painA 8 1B 21 6C 16 6History of lumbar surgeryNo 33 8Yes 12 5Mode of surgeryLumbar canal decompression 4 1Lumbar fusion 8 4

Fig. 2. Operation process of dorsal endoscopic rhizotomy (A) and normal an

orsal of the base of the transverse process and bony structuresf the SAP (Fig. 2). Skin incision was sutured by absorbable sutureaterial after endoscope and working cannula were removed.

.3. Follow-up and medical evaluation

All patients were discharged 2 days after the operation. Beinglinded to the treatment assignments, the surgeon assessed eachatient. The post-rhizotomic patients were followed up 1 day, 3onths, 6 months and 12 months postoperatively, respectively.During that follow up period, the patients completed the visual

nalog scale (VAS) questionnaire. Low back pain or referred painas measured on a visual analog scale (VAS) (with values ranging

rom 0 to 10) before MBB, after MBB, immediately after the surgerybaseline) and at the end of the 3rd, 6th, and 12th month postop-ratively. A higher score on the VAS equates to a higher level ofain.

Percentage of pain relief (%) was calculated as: (VAS score afterreatment − VAS score before MBB) × 100/VAS score before MBB.

The MacNab score was recorded at 12 months postoperatively.he MacNab criteria were applied to each patient by characteriz-ng pain relief of 75–100% as excellent, 50–74% as good, 25–49%s fair, and 0–24% as poor [17]. Success is based on an excellent,ood, or fair outcome. Besides, any potential complications werelso evaluated at each visit.

.4. Statistical analysis

All analyses were performed using SPSS 11.5 software (SPSS,hicago, IL, USA). Qualitative data were expressed as frequencynd percentage. Chi-square test was used to examine the relationetween qualitative variables. Normally distributed continuousata are presented as means ± standard deviation (SD) and wereompared using t tests. Non-normally distributed continuous datare presented as the median and range, and were compared usinghe Wilcoxon rank sum test. Differences within groups betweenatients’ preoperative and postoperative VAS scores were analyzedor significance using one-way analysis of variance. Differencemong 2 or more than 2 groups were assessed by using t tests.ifferences were considered statistically significant when P < 0.05.

. Results

.1. Patient’s characteristics

The mean age of patients receiving dorsal endoscopic rhizotomyas (61.84 ± 11.77) years, and it was (62.62 ± 19.83) years for thoseho underwent conservative treatment. In the operation group, 25

al morphology of medial branch of the dorsal ramus of the spinal nerve (B).

were males (56%) and 20 were females (44%), while in the conserva-tive group, 6 were males (46.2%) and 7 were females (53.8%). Painswith or without the referred pain were classified according to thelow back pain location. Most of the pains were 27B (46.5%) followedby 22C (37.9%). The average pre-operative VAS score of back pain forthe operation group was (7.69 ± 1.06) as compared to (6.69 ± 0.75)for the conservative group, while the mean pre-operative VASscore of referred pain was (7.69 ± 1.06) for the operation groupand (6.69 ± 0.75) for the conservative group, marked as the level ofsevere and constant pain in our questionnaire. The VAS score wasfound to be significantly higher in the operation group as comparedto the conservative group (all P < 0.05). Twenty two percent (22%)of patients reported a duration of pain for 1 year or less, whereas28% reported a longer duration of 1 to 4 years, and 50% sufferedpain for longer than 4 years. The average duration of pain includ-ing low back pain and referred pain was significantly greater in theoperation group than that in the conservative group (P < 0.05). Nostatistically significant difference in age, sex, type and duration ofreferred pain, history of lumbar spine surgery, mode of surgery wasobserved between the two groups (P > 0.05) (see Table 1).

Fig. 3 shows no significant difference in the distribution for eachjoint involved between the two groups (P > 0.05). In the 45 patientsunderwent dorsal endoscopic rhizotomy, the surgical target were

* P < 0.05, versus conservative group; A, patients whose pain was only in the lowerback; B, patients whose pain was predominantly in the low back, but also haveradiated into the buttocks and legs; C, patients whose pain was predominantly inthe low back, but also have spread into the knee or even lower.

14 Z.-Z. Li et al. / Clinical Neurology and Neurosurgery 126 (2014) 11–17

Fig. 3. Range and segment distribution of the medial branch blocks (MBB) in twogroups. Group A, operation group; Group B, conservative group.

Fig. 4. Distribution of surgical target in patients receiving dorsal endoscopic rhi-zotomy. Wilcoxon test showed no significant difference between the two sides(P > 0.05). L, left side; R, right side.

Table 4MacNab score of the 1 year postoperative evaluation in two groups.

MacNab score Operation group Conservative operation

Excellent 27 (60%) 0 (0%)Good 17 (37.8%) 0 (0%)

Table 2VAS score change of the back pain and referred pain (means ± standard deviation).

Time point Operation group

Back pain Referre

Before MBB 7.66 ± 1.06 5.41 ±After MBB 0.47 ± 0.55 1.00 ±Postoperative 1 day 0.42 ± 0.58* 0.49 ±Postoperative 3 months 0.51 ± 0.99* 0.46 ±Postoperative 6 months 0.58 ± 1.03* 0.51 ±Postoperative 12 months 1 0.69 ± 1.00* 0.41 ±

MBB, medial branch block.* P < 0.01, versus before MBB.# P < 0.01, versus after MBB.

Table 3Comparison of relief of pain (back/referred) at different time point in the two groups (me

Time point Back pain

Operation group Conservative g

After MBB 93.70 ± 7.54 90.93 ± 7.58

Post 1 day 94.26 ± 7.98* 23.26 ± 15.21Post 3 months 93.27 ± 12.57* 23.26 ± 15.21Post 6 months 92.36 ± 13.19* 13.55 ± 17.40Post 12 months 90.82 ± 13.05* 22.25 ± 11.96

MBB, medial branch block; Post, postoperative.* As compared to conservative group, P < 0.01.

Fair 1 (2.2%) 6 (46.2)Poor 0 7 (53.8)

3.2. Postoperative outcomes

In the operation group, all the 45 patients completed the endo-scopic dorsal endoscopic rhizotomy. During the follow-up period,no complications were observed. During operation, we observedanatomical variants of the dorsal ramus of the spinal nerve, includ-ing the number, the thickness and the positioning of the dorsalramus (Fig. 5).

Table 2 summarized the VAS score of the low back pain andreferred pain before MBB, after MBB, immediately after surgeryand at 3, 6, and 12 months postoperatively in the two groups. Inthe operation group, the low back pain and referred pain showeda lower score at any time point postoperatively (P < 0.01), as com-pared to the VAS pain score obtained before MBB, while showed nostatistical difference (P > 0.05) as compared to the VAS pain scoreobtained after MBB. In the conservative group, the low back painand referred pain showed a lower score at any time point post-operatively (P < 0.01), as compared to the VAS pain score obtainedbefore MBB, while showed a higher score (P > 0.05) as compared tothe VAS pain score obtained after MBB. The VAS back or referredpain score in the two groups was not statistically different at anytime point postoperatively (P > 0.05).

Table 3 illustrated therapeutic procedural characteristics withaverage degree of pain relief after MBB and at 3, 6, and 12 monthspostoperatively in the two groups. There was not statistically dif-ferent with respect to the degree of pain relief (back/referred) afterMBB in the two groups. The relief of pain (back/referred) at any

time point postoperatively in the operation group was higher incomparison to that in the conservative group (t test, all P < 0.01).

As shown in Table 4, excellent/good McNab outcomes of the1 year postoperative evaluation in the operation group were

Conservative group

d pain Back pain Referred pain

1.88 6.70 ± 0.75 4.17 ± 0.83 1.27 0.62 ± 0.51 0.75 ± 0.62 0.80* 1.85 ± 0.90*,# 0.83 ± 0.72*,#

0.73* 5.15 ± 1.21*,# 2.92 ± 1.08*,#

0.69* 5.85 ± 1.57*,# 3.50 ± 1.09*,#

0.50* 5.38 ± 1.26*,# 3.00 ± 1.04*,#

ans ± standard deviation).

Referred pain

roup Operation group Conservative group

81.18 ± 21.88 82.36 ± 13.53 90.02 ± 18.95* 31.11 ± 15.03 89.67 ± 19.17* 31.11 ± 15.03

87.92 ± 19.19* 15.97 ± 19.29 90.29 ± 12.76* 27.92 ± 20.59

Z.-Z. Li et al. / Clinical Neurology and Neurosurgery 126 (2014) 11–17 15

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ig. 5. Endoscopic anatomy and its variants of dorsal ramus of the spinal nerve (reranch variants of dorsal ramus of the spinal nerve; (C) thinned anatomical variantserve covered by periosteum. (For interpretation of the references to color in this fi

ecorded as 97.8%, which was significantly higher than that in theonservative group (P < 0.01).

. Discussion

Chronic low back pain is hard to diagnose, because history andhysical examination associated with radiological studies (X-ray,T, and MRI) are unspecific for the disease [18]. Lumbar facet jointsre synovial joints consisting of diarthrodial articulations betweenosterior elements of adjacent vertebrae and are innervated byedial branches of the dorsal rami from spinal nerves. It is gen-

rally assumed that facetogenic CLBP is not as acute as nerve rootain and is usually characterized as a deep and dull pain, thus itsccurate loci are fairly difficult to target. This syndrome is charac-erized clinically by chronic back pain, which deteriorates duringotation or torsion movements, with selective pressure sorenesst the level of facet involved. It can radiate into the buttocks andpsilateral legs, or even worse, spread into the knee or even theoot. The patients included in this study had mechanical low backain, whose lumbar pain increased during rotation or extensionovements. These characteristics have an indicative value for the

iagnosis of facetogenic low back pain.Facetogenic lumbar pain is usually accompanied by referred

ain, i.e., lumbar facet joints are implicated as the source of chronic

ow back pain. Further, facet joints of the lumbar spine have beenhown to be capable of causing pain in the low back with referredain to the lower extremities in normal volunteers [19]. The loca-ion of referred pain is correlated with the segmental distribution

ws). (A) Bifurcated branch variants of dorsal ramus of the spinal nerve; (B) multi-rsal ramus of the spinal nerve; (D) anatomical variant of dorsal ramus of the spinalegend, the reader is referred to the web version of this article.)

in lumbar zygapophysial facet joint. Referred pain of upper lum-bar facet joint was located at lumbar region or adjacent to theposterior iliac crest, whereas the pain of the lower lumbar facetjoint usually spread into the buttocks. However, lesion segmentcannot be speculated from the location of referred pain due tothe overlap of the range of the referred pain among different seg-ments. Despite the lack of quantitative research, a pervious studyshowed that the (involved) distance of the referred pain was pos-itively correlated with the stimulus intensity, which means thestronger the harmful stimulus, the further the referred pain willspread [20]. Previous study reported that experimentally inducedreferred pain could cause the increase of electromyographic activ-ity; pain of the medial branch of the dorsal rami of lumbar nerveis often accompanied by involuntary activity of the muscles of thelower extremity. In this study, of the 58 patients, 27 cases (46.6%)has referred pain involved into the buttocks and legs, and 22 cases(37.9%) with more distant referred pain, both obtaining relief ofpain after MBB. It was consistent with the findings as describedpreviously [20].

Diagnostic blocks are the only means by which the source of apatient’s pain can be traced to their zygapophysial joints [21,22].Single, diagnostic blocks are not valid [23] and carry a false-positiverate of between 25% and 41% [21,24,25]. To reduce the likelihoodof false-positive responses, repeated blocks are required. Compar-

ative local anesthetic blocks using Lidocaine or Bupivacaine are asuitable candidate of control [26,27]. Previous study suggested thatcomparative blocks were found to have a sensitivity of 100%, yetonly with a specificity of 65% [27]. Our study demonstrated that

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he excellent/good McNab outcomes of the 1 year postoperativevaluation in the operation group were recorded as 97.8%, whichas higher than the findings reported previously, indicating thatorsal endoscopic rhizotomy improves the surgical outcomes sig-ificantly.

Currently, there has been no consensus on the number and levelsf segments. Segment selection is usually speculated according tohe location of the referred pain and local tenderness. Using a com-arative double block control, Manchukonda et al. [28] reportedhat blocking the L2-5 (namely L3-S1 facet joint) medial branch ofhe dorsal ramus of the spine nerve was the most effective modalityn the diagnosis of the lumbar facet joint pain. In our study, the lowack pain mostly arises from the facet joints (L3-S1), which wasonsistent with the previous study.

No form of conservative treatment including drugs, physicalherapy, or cognitive-behavioral therapy has ever been tested forfficacy for proven lumbar facet joint pain. In our study, the relieff pain was lower than 30% at any time point postoperativelyfter 1-year follow-up, which was consistent with the findings ofrevious report. Percutaneous lumbar medial branch neurotomyas been indicated as the effective methods for the treatment of

acetogenic chronic back pain [29]. The theoretical basis of this neu-otomy is to denature the nerves innervating the painful joint andlock the afferent pathway of the source of the chronic low backain. A previous study reported that the effectiveness of percu-aneous lumbar medial branch neurotomy (LMBN) is only 43–80%30,31]. Anatomical variations of the medial branch of dorsal ramusnatomy, incorrect placement of electrode, incomplete ablation,nd nerve regeneration may be the important factors affecting theffectiveness of this neurotomy. In this study, we found multi-le anatomic variants of the medial branch anatomy. In clinicalractice, percutaneous puncture technique may not achieve sat-

sfactory therapeutic benefit if it fails to reach the location of thenatomic variants of the nerve. Endoscope-assisted technologyan contribute to the denaturing of the normal and varied medialranches of the nerve. Relief after LMBN typically lasts between

and 12 months [32]. Pain recurs when the nerves regenerate,ut relief can be reinstated by repeated neurotomy [32]. Successfulreatment which repeated two and three times has been reported32], however, no limit has yet been established as to the num-er of times that the procedure can be successfully repeated toaintain relief of pain. Endoscopic-assisted dorsal ramus rhizo-

omy can directly denature the medial branch and block the nerveegeneration of the medial branch, which significantly reduces theossibility of the nerve regeneration and results in a low recurrencef pain. In our study, we found that the excellent/good McNab out-omes of the 1 year postoperative evaluation in the operation groupere recorded as 97.8%, with a recurrence rate of only 2.2%, sug-

esting that our treatment technology achieved good therapeuticesults.

Previous study reported that the satisfaction rate was 41% inatients with a history of laminectomy, whereas it was only 27%

n patients with a history of lumbar spine fusion after percuta-eous LMBN [33]. In our study, 17 patients had a history of lumbarpine surgery, of which 12 cases received DER treatment. Thexcellent/good McNab outcomes after a 1-year follow-up in theperation group were recorded as 91.7% (11/12). In contrast thether 5 patients in the conservative group did not achieve suchherapeutic benefit. These findings suggested that the DER can stillchieve a desirable therapeutic effect despite the fact of a failedack surgery syndrome.

Percutaneous lumbar medial branch neurotomy may lead

o a few minor complications, such as painful dysesthesias,ainful anesthesia, hyperesthesia and nerve root injury. In ourtudy, however, no complication was observed, indicating thatndoscopic-assisted technique has increased the accuracy and

[[

eurosurgery 126 (2014) 11–17

thoroughness of neurotomy and ameliorated the potential occur-rence of surgery-related complications.

5. Conclusion

Dorsal endoscopic rhizotomy is proposed as a safe and effectivetreatment for facetogenic CLBP, allowing the achievement a bet-ter clinical outcome than the conventional conservative treatment.Further studies with a larger sample size of patients and a longerperiod of follow-up are anticipated to further validate and supportthe efficacy of this technique.

Conflict of interest

The authors have no conflicts of interest to declare.

Acknowledgements

None.

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