Clinical Neurology and Neurosurgery 126 (2014) 11–17
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Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Evaluation of endoscopic dorsal ramus rhizotomy in managing facetogenic chronic low back pain Zhen-Zhou Li ∗ , Shu-Xun Hou, Wei-Lin Shang, Ke-Ran Song, Wen-Wen Wu Department of Orthopedics Surgery, the First Affiliated Hospital of Chinese PLA General Hospital, Beijing, China
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Article history: Received 30 June 2014 Received in revised form 24 July 2014 Accepted 9 August 2014 Available online 18 August 2014 Keywords: Chronic low back pain Lumbar zygapophysial joint Medial branch neurotomy Endoscope Rhizotomy
a b s t r a c t Objective: To study the effectiveness of surgical dorsal endoscopic rhizotomy for the treatment of facetogenic chronic low back pain. Methods: From April 2011 to November 2011, 58 patients who were diagnosed with lumbar facetogenic chronic low back pain (CLBP) and thereafter experienced >80% reliefs of pain with two comparative lumbar 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 conservative treatment. Patients’ preoperative and postoperative VAS score, percentage of pain relief and the MacNab score were analyzed and compared. Anatomic variations and any possible complications were recorded. Results: In the operation group, VAS scores of pain (low back/referred) at any time point postoperatively were significantly lower than that before MBB (P < 0.05), which, however, showed no significant difference as compared to the scores after MBB (P > 0.05). In the conservative group, VAS scores of pain (low back/referred) at any time point postoperatively with conservative treatment decreased significantly compared 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 operation group were higher than that in the conservative group. In addition, four separate newly identified anatomical variations of medial branch anatomy were observed and reported. Conclusion: Dorsal endoscopic rhizotomy is safe and effective for the facetogenic CLBP, and can achieve better clinical outcome than the conservative treatment. © 2014 Elsevier B.V. All rights reserved.
1. Introduction The lumbar facet or zygapophysial joints are paired diarthrodial articulations between posterior elements of adjacent vertebrae [1]. It consists of a distinct joint space capable of accommodating between 1 and 1.5 ml of fluid, a synovial membrane, hyaline cartilage surfaces, and a fibrous capsule [2]. The facet joint capsule and the surrounding structures are innervated [3]. Chemical or mechanical stimulation of the facet joints and their nerve supply may elicit back and/or leg pain [4]. Facet joints have been implicated as a source of chronic pain with an overall prevalence of 31% (circa.
∗ Corresponding author at: Department of Orthopedics Surgery, the First Affiliated Hospital of Chinese PLA General Hospital, No. 51, Fucheng Road, Haidian District, Beijing 100048, China. Tel.: +86 13601266970; fax: +86 10 85630233. E-mail address: [email protected] (Z.-Z. Li). http://dx.doi.org/10.1016/j.clineuro.2014.08.014 0303-8467/© 2014 Elsevier B.V. All rights reserved.
21–41%) in a heterogeneous patient population with chronic low back pain (CLBP) [5]. Chronic low back pain of facet joint origin may be managed by intra-articular lumbar facet joint injections [6,7], lumbar facet joint nerve blocks [8,9], and radiofrequency neurotomy [10,11]. However, there have been disparities in the previous reports regarding the varying outcome parameters of the different treatment modalities [3,12–15]. A recent narrative review by Bogduk [16] suggested that lumbar medial branch neurotomy remains as the only effective treatment available for CLBP. The theoretical basis of neurotomy lies in the fact that facet joint surgery deadens the medial branches and cuts off their afferent pathways which are the source of the chronic low back pain. A one-year follow-up study showed that the effectiveness of percutaneous neurotomy of medial branches is only 43–80%. Anatomical variations of the dorsal medial branch anatomy, incorrect placement of electrode, incomplete ablation, and nerve regeneration are important factors that should be taken
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into account when deciding or moderating the effectiveness of medial branch neurotomy. The aims of our study were to evaluate the effectiveness of dorsal endoscopic rhizotomy and compare it with the conservative treatment for the treatment of facetogenic chronic low back pain with respect to VAS scores, percentage of pain relief, and MacNab scores. 2. Methods 2.1. Participants This study was approved by the ethics committee of the First Affiliated Hospital of PLA’s General Hospital (China), and written informed consent was obtained from all participants. From April 2011 to November 2011, 58 patients who were diagnosed as lumbar facetogenic chronic low back pain (CLBP) and registered at the Department of Orthopedics Surgery of the First Affiliated Hospital of PLA’s General Hospital were included in a prospective 1-year follow-up. The inclusion criteria were: (1) patients with chronic low back pain of at least 3 months’ duration, (2) patients with mechanical low back pain especially elicited by movement of torsion/rotation and from flexion to extension, (3) patients with spine diseases of degenerative lumbar instability, lumbar degenerative spondylolisthesis, degenerative lumbar scoliosis, and/or lumbar facet joint osteoarthritis, and (4) patients who experienced >80% relief of pain with two comparative lumbar medial branch blocks (lidocaine and bupivacaine). The exclusion criteria were: (1) patients with radicular pain (defined as neurological findings of nerve root dysfunction), or with cauda equina syndrome and (2) patients with a known specific etiology for low back pain such as infection, tumor, or trauma. Considering referred pain, patients can be divided into three groups: (1) patients whose pain was
only in the lower back (group A); (2) patients whose pain was predominantly in the low back, yet also radiated into the buttocks and legs (group B); and (3) patients whose pain was predominantly in the low back, yet has vastly spread into the knee or even lower (group C). The patients were randomly divided into two groups (each with 45 and 13 cases, respectively), i.e., the operation group comprising of 45 cases received dorsal endoscopic rhizotomy, and the conservative group consisting of 13 cases received conservative treatment, 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 platform, and made sure that their lumbar kyphosis and abdomen not be pressed. Local anesthesia (1 ml of 0.5% lidocaine) and mild sedation with fentanyl or midazolam were carried out. Surgical loci were determined according to the scope of the medial branch block which was performed under fluoroscopy. The target point is at the junction of the base of superior articular processes (SAP) and the transverse process (Fig. 1a and b). An 18-G needle was docked onto the target point. The anteroposterior fluoroscopic view and the lateral view were obtained with the maximal exposure of the target regions (Fig. 1c and d). Each target was injected with 2 ml of a mixture of contrast agents consisting of 1.6 ml of omnipaque and 0.4 ml of methylene blue. Then guide wire, soft tissue dilator and beveled working cannula were serially inserted. After checking the proper location of the cannula, forceps was used to remove the fatty tissue between muscles. RF probe was inserted through endoscope. Then, the soft tissue at base of the transverse process including the medial branch was removed in order to completely expose the
Fig. 1. Positioning the surgical points. (A) target point for dorsal endoscopic rhizotomy (TP, transerve process, AP, accessory process, MAL, mammillary-accessary ligament, MB, medial branch); (B) the skin entry point for dorsal endoscopic rhizotomy; (C) frontal view showing the puncture needle was docked into the target positions; (D) lateral view showing the puncture needle was docked into the dorsal region of the transverse process.
Z.-Z. Li et al. / Clinical Neurology and Neurosurgery 126 (2014) 11–17
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Fig. 2. Operation process of dorsal endoscopic rhizotomy (A) and normal anatomical morphology of medial branch of the dorsal ramus of the spinal nerve (B).
dorsal of the base of the transverse process and bony structures of the SAP (Fig. 2). Skin incision was sutured by absorbable suture material after endoscope and working cannula were removed. 2.3. Follow-up and medical evaluation All patients were discharged 2 days after the operation. Being blinded to the treatment assignments, the surgeon assessed each patient. The post-rhizotomic patients were followed up 1 day, 3 months, 6 months and 12 months postoperatively, respectively. During that follow up period, the patients completed the visual analog scale (VAS) questionnaire. Low back pain or referred pain was measured on a visual analog scale (VAS) (with values ranging from 0 to 10) before MBB, after MBB, immediately after the surgery (baseline) and at the end of the 3rd, 6th, and 12th month postoperatively. A higher score on the VAS equates to a higher level of pain. Percentage of pain relief (%) was calculated as: (VAS score after treatment − VAS score before MBB) × 100/VAS score before MBB. The MacNab score was recorded at 12 months postoperatively. The MacNab criteria were applied to each patient by characterizing pain relief of 75–100% as excellent, 50–74% as good, 25–49% as fair, and 0–24% as poor [17]. Success is based on an excellent, good, or fair outcome. Besides, any potential complications were also evaluated at each visit.
were males (56%) and 20 were females (44%), while in the conservative group, 6 were males (46.2%) and 7 were females (53.8%). Pains with or without the referred pain were classified according to the low back pain location. Most of the pains were 27B (46.5%) followed by 22C (37.9%). The average pre-operative VAS score of back pain for the operation group was (7.69 ± 1.06) as compared to (6.69 ± 0.75) for the conservative group, while the mean pre-operative VAS score of referred pain was (7.69 ± 1.06) for the operation group and (6.69 ± 0.75) for the conservative group, marked as the level of severe and constant pain in our questionnaire. The VAS score was found to be significantly higher in the operation group as compared to the conservative group (all P < 0.05). Twenty two percent (22%) of patients reported a duration of pain for 1 year or less, whereas 28% reported a longer duration of 1 to 4 years, and 50% suffered pain for longer than 4 years. The average duration of pain including low back pain and referred pain was significantly greater in the operation group than that in the conservative group (P < 0.05). No statistically significant difference in age, sex, type and duration of referred pain, history of lumbar spine surgery, mode of surgery was observed between the two groups (P > 0.05) (see Table 1). Fig. 3 shows no significant difference in the distribution for each joint involved between the two groups (P > 0.05). In the 45 patients underwent dorsal endoscopic rhizotomy, the surgical target were predominantly performed at the zygapophyseal joint (L3-S1) (18 cases). Fig. 4 summarizes the distribution for the levels of treatment.
2.4. Statistical analysis All analyses were performed using SPSS 11.5 software (SPSS, Chicago, IL, USA). Qualitative data were expressed as frequency and percentage. Chi-square test was used to examine the relation between qualitative variables. Normally distributed continuous data are presented as means ± standard deviation (SD) and were compared using t tests. Non-normally distributed continuous data are presented as the median and range, and were compared using the Wilcoxon rank sum test. Differences within groups between patients’ preoperative and postoperative VAS scores were analyzed for significance using one-way analysis of variance. Difference among 2 or more than 2 groups were assessed by using t tests. Differences were considered statistically significant when P < 0.05. 3. Results 3.1. Patient’s characteristics The mean age of patients receiving dorsal endoscopic rhizotomy was (61.84 ± 11.77) years, and it was (62.62 ± 19.83) years for those who underwent conservative treatment. In the operation group, 25
Table 1 Demographic characteristics. Index
Operation group
Sex (male/female)-no. Age (years) VAS score of back pain Duration of back pain (months) VAS score of referred pain Duration of referred pain (months) Type of referred pain A B C History of lumbar surgery No Yes Mode of surgery Lumbar canal decompression Lumbar fusion
25/20 6/7 61.84 ± 11.77 62.62 ± 19.83 7.69 ± 1.06* 6.69 ± 0.75 137.13 ± 135.77* 48.23 ± 71.40 5.41 ± 1.88* 4.17 ± 0.83 19.92 ± 23.27 (37) 14.25 ± 23.37 (12)
Conservative group
8 21 16
1 6 6
33 12
8 5
4 8
1 4
* P < 0.05, versus conservative group; A, patients whose pain was only in the lower back; B, patients whose pain was predominantly in the low back, but also have radiated into the buttocks and legs; C, patients whose pain was predominantly in the low back, but also have spread into the knee or even lower.
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Z.-Z. Li et al. / Clinical Neurology and Neurosurgery 126 (2014) 11–17 Table 4 MacNab score of the 1 year postoperative evaluation in two groups. MacNab score
Operation group
Excellent Good Fair Poor
27 (60%) 17 (37.8%) 1 (2.2%) 0
Conservative operation 0 (0%) 0 (0%) 6 (46.2) 7 (53.8)
3.2. Postoperative outcomes In the operation group, all the 45 patients completed the endoscopic dorsal endoscopic rhizotomy. During the follow-up period, no complications were observed. During operation, we observed anatomical variants of the dorsal ramus of the spinal nerve, including the number, the thickness and the positioning of the dorsal ramus (Fig. 5). Table 2 summarized the VAS score of the low back pain and referred pain before MBB, after MBB, immediately after surgery and at 3, 6, and 12 months postoperatively in the two groups. In the operation group, the low back pain and referred pain showed a lower score at any time point postoperatively (P < 0.01), as compared to the VAS pain score obtained before MBB, while showed no statistical difference (P > 0.05) as compared to the VAS pain score obtained after MBB. In the conservative group, the low back pain and referred pain showed a lower score at any time point postoperatively (P < 0.01), as compared to the VAS pain score obtained before MBB, while showed a higher score (P > 0.05) as compared to the VAS pain score obtained after MBB. The VAS back or referred pain score in the two groups was not statistically different at any time point postoperatively (P > 0.05). Table 3 illustrated therapeutic procedural characteristics with average degree of pain relief after MBB and at 3, 6, and 12 months postoperatively in the two groups. There was not statistically different with respect to the degree of pain relief (back/referred) after MBB in the two groups. The relief of pain (back/referred) at any time point postoperatively in the operation group was higher in comparison to that in the conservative group (t test, all P < 0.01). As shown in Table 4, excellent/good McNab outcomes of the 1 year postoperative evaluation in the operation group were
Fig. 3. Range and segment distribution of the medial branch blocks (MBB) in two groups. Group A, operation group; Group B, conservative group.
Fig. 4. Distribution of surgical target in patients receiving dorsal endoscopic rhizotomy. Wilcoxon test showed no significant difference between the two sides (P > 0.05). L, left side; R, right side.
Table 2 VAS score change of the back pain and referred pain (means ± standard deviation). Time point
Operation group
Conservative group
Back pain Before MBB After MBB Postoperative 1 day Postoperative 3 months Postoperative 6 months Postoperative 12 months 1
7.66 0.47 0.42 0.51 0.58 0.69
± ± ± ± ± ±
Referred pain
1.06 0.55 0.58* 0.99* 1.03* 1.00*
5.41 1.00 0.49 0.46 0.51 0.41
± ± ± ± ± ±
Back pain
1.88 1.27 0.80* 0.73* 0.69* 0.50*
6.70 0.62 1.85 5.15 5.85 5.38
± ± ± ± ± ±
0.75 0.51 0.90* , # 1.21* , # 1.57* , # 1.26* , #
Referred pain 4.17 0.75 0.83 2.92 3.50 3.00
± ± ± ± ± ±
0.83 0.62 0.72* , # 1.08* , # 1.09* , # 1.04* , #
MBB, medial branch block. * P < 0.01, versus before MBB. # P < 0.01, versus after MBB. Table 3 Comparison of relief of pain (back/referred) at different time point in the two groups (means ± standard deviation). Time point
Back pain Operation group
After MBB Post 1 day Post 3 months Post 6 months Post 12 months
93.70 94.26 93.27 92.36 90.82
± ± ± ± ±
7.54 7.98* 12.57* 13.19* 13.05*
MBB, medial branch block; Post, postoperative. * As compared to conservative group, P < 0.01.
Referred pain Conservative group 90.93 23.26 23.26 13.55 22.25
± ± ± ± ±
7.58 15.21 15.21 17.40 11.96
Operation group 81.18 90.02 89.67 87.92 90.29
± ± ± ± ±
21.88 18.95* 19.17* 19.19* 12.76*
Conservative group 82.36 31.11 31.11 15.97 27.92
± ± ± ± ±
13.53 15.03 15.03 19.29 20.59
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Fig. 5. Endoscopic anatomy and its variants of dorsal ramus of the spinal nerve (red arrows). (A) Bifurcated branch variants of dorsal ramus of the spinal nerve; (B) multibranch variants of dorsal ramus of the spinal nerve; (C) thinned anatomical variants of dorsal ramus of the spinal nerve; (D) anatomical variant of dorsal ramus of the spinal nerve covered by periosteum. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
recorded as 97.8%, which was significantly higher than that in the conservative group (P < 0.01). 4. Discussion Chronic low back pain is hard to diagnose, because history and physical examination associated with radiological studies (X-ray, CT, and MRI) are unspecific for the disease [18]. Lumbar facet joints are synovial joints consisting of diarthrodial articulations between posterior elements of adjacent vertebrae and are innervated by medial branches of the dorsal rami from spinal nerves. It is generally assumed that facetogenic CLBP is not as acute as nerve root pain and is usually characterized as a deep and dull pain, thus its accurate loci are fairly difficult to target. This syndrome is characterized clinically by chronic back pain, which deteriorates during rotation or torsion movements, with selective pressure soreness at the level of facet involved. It can radiate into the buttocks and ipsilateral legs, or even worse, spread into the knee or even the foot. The patients included in this study had mechanical low back pain, whose lumbar pain increased during rotation or extension movements. These characteristics have an indicative value for the diagnosis of facetogenic low back pain. Facetogenic lumbar pain is usually accompanied by referred pain, i.e., lumbar facet joints are implicated as the source of chronic low back pain. Further, facet joints of the lumbar spine have been shown to be capable of causing pain in the low back with referred pain to the lower extremities in normal volunteers [19]. The location of referred pain is correlated with the segmental distribution
in lumbar zygapophysial facet joint. Referred pain of upper lumbar facet joint was located at lumbar region or adjacent to the posterior iliac crest, whereas the pain of the lower lumbar facet joint usually spread into the buttocks. However, lesion segment cannot be speculated from the location of referred pain due to the overlap of the range of the referred pain among different segments. Despite the lack of quantitative research, a pervious study showed that the (involved) distance of the referred pain was positively correlated with the stimulus intensity, which means the stronger the harmful stimulus, the further the referred pain will spread [20]. Previous study reported that experimentally induced referred pain could cause the increase of electromyographic activity; pain of the medial branch of the dorsal rami of lumbar nerve is often accompanied by involuntary activity of the muscles of the lower 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 of pain after MBB. It was consistent with the findings as described previously [20]. Diagnostic blocks are the only means by which the source of a patient’s pain can be traced to their zygapophysial joints [21,22]. Single, diagnostic blocks are not valid [23] and carry a false-positive rate of between 25% and 41% [21,24,25]. To reduce the likelihood of false-positive responses, repeated blocks are required. Comparative local anesthetic blocks using Lidocaine or Bupivacaine are a suitable candidate of control [26,27]. Previous study suggested that comparative blocks were found to have a sensitivity of 100%, yet only with a specificity of 65% [27]. Our study demonstrated that
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the excellent/good McNab outcomes of the 1 year postoperative evaluation in the operation group were recorded as 97.8%, which was higher than the findings reported previously, indicating that dorsal endoscopic rhizotomy improves the surgical outcomes significantly. Currently, there has been no consensus on the number and levels of segments. Segment selection is usually speculated according to the location of the referred pain and local tenderness. Using a comparative double block control, Manchukonda et al. [28] reported that blocking the L2-5 (namely L3-S1 facet joint) medial branch of the dorsal ramus of the spine nerve was the most effective modality in the diagnosis of the lumbar facet joint pain. In our study, the low back pain mostly arises from the facet joints (L3-S1), which was consistent with the previous study. No form of conservative treatment including drugs, physical therapy, or cognitive-behavioral therapy has ever been tested for efficacy for proven lumbar facet joint pain. In our study, the relief of pain was lower than 30% at any time point postoperatively after 1-year follow-up, which was consistent with the findings of previous report. Percutaneous lumbar medial branch neurotomy has been indicated as the effective methods for the treatment of facetogenic chronic back pain [29]. The theoretical basis of this neurotomy is to denature the nerves innervating the painful joint and block the afferent pathway of the source of the chronic low back pain. A previous study reported that the effectiveness of percutaneous lumbar medial branch neurotomy (LMBN) is only 43–80% [30,31]. Anatomical variations of the medial branch of dorsal ramus anatomy, incorrect placement of electrode, incomplete ablation, and nerve regeneration may be the important factors affecting the effectiveness of this neurotomy. In this study, we found multiple anatomic variants of the medial branch anatomy. In clinical practice, percutaneous puncture technique may not achieve satisfactory therapeutic benefit if it fails to reach the location of the anatomic variants of the nerve. Endoscope-assisted technology can contribute to the denaturing of the normal and varied medial branches of the nerve. Relief after LMBN typically lasts between 6 and 12 months [32]. Pain recurs when the nerves regenerate, but relief can be reinstated by repeated neurotomy [32]. Successful treatment which repeated two and three times has been reported [32], however, no limit has yet been established as to the number of times that the procedure can be successfully repeated to maintain relief of pain. Endoscopic-assisted dorsal ramus rhizotomy can directly denature the medial branch and block the nerve regeneration of the medial branch, which significantly reduces the possibility of the nerve regeneration and results in a low recurrence of pain. In our study, we found that the excellent/good McNab outcomes of the 1 year postoperative evaluation in the operation group were recorded as 97.8%, with a recurrence rate of only 2.2%, suggesting that our treatment technology achieved good therapeutic results. Previous study reported that the satisfaction rate was 41% in patients with a history of laminectomy, whereas it was only 27% in patients with a history of lumbar spine fusion after percutaneous LMBN [33]. In our study, 17 patients had a history of lumbar spine surgery, of which 12 cases received DER treatment. The excellent/good McNab outcomes after a 1-year follow-up in the operation group were recorded as 91.7% (11/12). In contrast the other 5 patients in the conservative group did not achieve such therapeutic benefit. These findings suggested that the DER can still achieve a desirable therapeutic effect despite the fact of a failed back surgery syndrome. Percutaneous lumbar medial branch neurotomy may lead to a few minor complications, such as painful dysesthesias, painful anesthesia, hyperesthesia and nerve root injury. In our study, however, no complication was observed, indicating that endoscopic-assisted technique has increased the accuracy and
thoroughness of neurotomy and ameliorated the potential occurrence of surgery-related complications. 5. Conclusion Dorsal endoscopic rhizotomy is proposed as a safe and effective treatment for facetogenic CLBP, allowing the achievement a better clinical outcome than the conventional conservative treatment. Further studies with a larger sample size of patients and a longer period of follow-up are anticipated to further validate and support the efficacy of this technique. Conflict of interest The authors have no conflicts of interest to declare. Acknowledgements None. References [1] Bogduk N, Twomey L. The zygapophysial joints. Clinical anatomy of the lumbar spine and sacrum; 1997. p. 33–41. [2] Glover J. Arthrography of the joints of the lumbar vertebral arches. Orthop Clin North Am 1977;8:37–42. [3] Van Zundert J, Vanelderen P, Kessels A, van Kleef M. Radiofrequency treatment of facet-related pain: evidence and controversies. Curr Pain Headache Rep 2012;16:19–25. [4] Cohen SP, Raja SN. Pathogenesis, diagnosis, and treatment of lumbar zygapophysial (facet) joint pain. Anesthesiology 2007;106:591–614. [5] Manchikanti L, Singh V, Falco FJ, Cash KA, Pampati V. Evaluation of lumbar facet joint nerve blocks in managing chronic low back pain: a randomized, doubleblind, controlled trial with a 2-year follow-up. Int J Med Sci 2010;7:124–35. [6] Carette S, Marcoux S, Truchon R, Grondin C, Gagnon J, Allard Y, et al. A controlled trial of corticosteroid injections into facet joints for chronic low back pain. N Engl J Med 1991;325:1002–7. [7] Schulte T, Pietilä T, Heidenreich J, Brock M, Stendel R. Injection therapy of lumbar facet syndrome: a prospective study. Acta Neurochir (Wien) 2006;148:1165–72. [8] Manchikanti L, Manchikanti K, Manchukonda R, Cash K, Damron K, Pampati V, et al. Evaluation of lumbar facet joint nerve blocks in the management of chronic low back pain: a preliminary report of a randomized, double-blind controlled trial: Clinical Trial NCT00355914. Pain Physician 2007;10:425. [9] Manchikanti L, Manchikanti KN, Damron K, Pampati V. Effectiveness of cervical medial branch blocks in chronic neck pain: a prospective outcome study. Pain Physician 2004;7:195–202. [10] Tomé-Bermejo F, Barriga-Martín A, Martín JLR. Identifying patients with chronic low back pain likely to benefit from lumbar facet radiofrequency denervation: a prospective study. J Spinal Disord Tech 2011;24:69–75. [11] Streitberger K, Müller T, Eichenberger U, Trelle S, Curatolo M. Factors determining the success of radiofrequency denervation in lumbar facet joint pain: a prospective study. Eur Spine J 2011;20:2160–5. [12] Physicians ASoIP. Interventional techniques: evidence-based practice guidelines in the management of chronic spinal pain; 2007. [13] Boswell MV, Shah RV, Everett CR, Sehgal N, Mckenzie-Brown AM, Abdi S, et al. Interventional techniques in the management of chronic spinal pain: evidencebased practice guidelines. Pain Physician 2005;8:1–47. [14] Boswell MV, Colson JD, Sehgal N, Dunbar EE, Epter R. A systematic review of therapeutic facet joint interventions in chronic spinal pain. Pain Physician 2007;10:229–53. [15] Manchikanti L, Singh V, Vilims BD, Hansen HC, Schultz DM, Kloth DS. Systematic review. Pain Physician 2002;5:405–18. [16] Bogduk N. Evidence-informed management of chronic low back pain with facet injections and radiofrequency neurotomy. Spine J 2008;8:56–64. [17] MacNab I. Negative disc exploration: an analysis of the causes of nerve-root involvement in sixty-eight patients. J Bone Joint Surg Am 1971;53:891–903. [18] Masala S, Nano G, Mammucari M, Marcia S, Simonetti G. Medial branch neurotomy in low back pain. Neuroradiology 2012;54:737–44. [19] Manchikanti L, Singh V, Falco F, Cash KA, Pampati V. Lumbar facet joint nerve blocks in managing chronic facet joint pain: one-year follow-up of a randomized, double-blind controlled trial: Clinical Trial NCT00355914. Pain Physician 2008;11:121–32. [20] Mooney V, Robertson J. The facet syndrome. Clin Orthop 1976;115:149–57. [21] Schwarzer A, Aprill C, Derby R, Fortin J, Kine G, Bogduk N. The false-positive rate of uncontrolled diagnostic blocks of the lumbar zygapophysial joints. Pain 1994;58:195–200.
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Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Evaluation of endoscopic dorsal ramus rhizotomy in managing facetogenic chronic low back pain Zhen-Zhou Li ∗ , Shu-Xun Hou, Wei-Lin Shang, Ke-Ran Song, Wen-Wen Wu Department of Orthopedics Surgery, the First Affiliated Hospital of Chinese PLA General Hospital, Beijing, China
a r t i c l e
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Article history: Received 30 June 2014 Received in revised form 24 July 2014 Accepted 9 August 2014 Available online 18 August 2014 Keywords: Chronic low back pain Lumbar zygapophysial joint Medial branch neurotomy Endoscope Rhizotomy
a b s t r a c t Objective: To study the effectiveness of surgical dorsal endoscopic rhizotomy for the treatment of facetogenic chronic low back pain. Methods: From April 2011 to November 2011, 58 patients who were diagnosed with lumbar facetogenic chronic low back pain (CLBP) and thereafter experienced >80% reliefs of pain with two comparative lumbar 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 conservative treatment. Patients’ preoperative and postoperative VAS score, percentage of pain relief and the MacNab score were analyzed and compared. Anatomic variations and any possible complications were recorded. Results: In the operation group, VAS scores of pain (low back/referred) at any time point postoperatively were significantly lower than that before MBB (P < 0.05), which, however, showed no significant difference as compared to the scores after MBB (P > 0.05). In the conservative group, VAS scores of pain (low back/referred) at any time point postoperatively with conservative treatment decreased significantly compared 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 operation group were higher than that in the conservative group. In addition, four separate newly identified anatomical variations of medial branch anatomy were observed and reported. Conclusion: Dorsal endoscopic rhizotomy is safe and effective for the facetogenic CLBP, and can achieve better clinical outcome than the conservative treatment. © 2014 Elsevier B.V. All rights reserved.
1. Introduction The lumbar facet or zygapophysial joints are paired diarthrodial articulations between posterior elements of adjacent vertebrae [1]. It consists of a distinct joint space capable of accommodating between 1 and 1.5 ml of fluid, a synovial membrane, hyaline cartilage surfaces, and a fibrous capsule [2]. The facet joint capsule and the surrounding structures are innervated [3]. Chemical or mechanical stimulation of the facet joints and their nerve supply may elicit back and/or leg pain [4]. Facet joints have been implicated as a source of chronic pain with an overall prevalence of 31% (circa.
∗ Corresponding author at: Department of Orthopedics Surgery, the First Affiliated Hospital of Chinese PLA General Hospital, No. 51, Fucheng Road, Haidian District, Beijing 100048, China. Tel.: +86 13601266970; fax: +86 10 85630233. E-mail address: [email protected] (Z.-Z. Li). http://dx.doi.org/10.1016/j.clineuro.2014.08.014 0303-8467/© 2014 Elsevier B.V. All rights reserved.
21–41%) in a heterogeneous patient population with chronic low back pain (CLBP) [5]. Chronic low back pain of facet joint origin may be managed by intra-articular lumbar facet joint injections [6,7], lumbar facet joint nerve blocks [8,9], and radiofrequency neurotomy [10,11]. However, there have been disparities in the previous reports regarding the varying outcome parameters of the different treatment modalities [3,12–15]. A recent narrative review by Bogduk [16] suggested that lumbar medial branch neurotomy remains as the only effective treatment available for CLBP. The theoretical basis of neurotomy lies in the fact that facet joint surgery deadens the medial branches and cuts off their afferent pathways which are the source of the chronic low back pain. A one-year follow-up study showed that the effectiveness of percutaneous neurotomy of medial branches is only 43–80%. Anatomical variations of the dorsal medial branch anatomy, incorrect placement of electrode, incomplete ablation, and nerve regeneration are important factors that should be taken
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into account when deciding or moderating the effectiveness of medial branch neurotomy. The aims of our study were to evaluate the effectiveness of dorsal endoscopic rhizotomy and compare it with the conservative treatment for the treatment of facetogenic chronic low back pain with respect to VAS scores, percentage of pain relief, and MacNab scores. 2. Methods 2.1. Participants This study was approved by the ethics committee of the First Affiliated Hospital of PLA’s General Hospital (China), and written informed consent was obtained from all participants. From April 2011 to November 2011, 58 patients who were diagnosed as lumbar facetogenic chronic low back pain (CLBP) and registered at the Department of Orthopedics Surgery of the First Affiliated Hospital of PLA’s General Hospital were included in a prospective 1-year follow-up. The inclusion criteria were: (1) patients with chronic low back pain of at least 3 months’ duration, (2) patients with mechanical low back pain especially elicited by movement of torsion/rotation and from flexion to extension, (3) patients with spine diseases of degenerative lumbar instability, lumbar degenerative spondylolisthesis, degenerative lumbar scoliosis, and/or lumbar facet joint osteoarthritis, and (4) patients who experienced >80% relief of pain with two comparative lumbar medial branch blocks (lidocaine and bupivacaine). The exclusion criteria were: (1) patients with radicular pain (defined as neurological findings of nerve root dysfunction), or with cauda equina syndrome and (2) patients with a known specific etiology for low back pain such as infection, tumor, or trauma. Considering referred pain, patients can be divided into three groups: (1) patients whose pain was
only in the lower back (group A); (2) patients whose pain was predominantly in the low back, yet also radiated into the buttocks and legs (group B); and (3) patients whose pain was predominantly in the low back, yet has vastly spread into the knee or even lower (group C). The patients were randomly divided into two groups (each with 45 and 13 cases, respectively), i.e., the operation group comprising of 45 cases received dorsal endoscopic rhizotomy, and the conservative group consisting of 13 cases received conservative treatment, 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 platform, and made sure that their lumbar kyphosis and abdomen not be pressed. Local anesthesia (1 ml of 0.5% lidocaine) and mild sedation with fentanyl or midazolam were carried out. Surgical loci were determined according to the scope of the medial branch block which was performed under fluoroscopy. The target point is at the junction of the base of superior articular processes (SAP) and the transverse process (Fig. 1a and b). An 18-G needle was docked onto the target point. The anteroposterior fluoroscopic view and the lateral view were obtained with the maximal exposure of the target regions (Fig. 1c and d). Each target was injected with 2 ml of a mixture of contrast agents consisting of 1.6 ml of omnipaque and 0.4 ml of methylene blue. Then guide wire, soft tissue dilator and beveled working cannula were serially inserted. After checking the proper location of the cannula, forceps was used to remove the fatty tissue between muscles. RF probe was inserted through endoscope. Then, the soft tissue at base of the transverse process including the medial branch was removed in order to completely expose the
Fig. 1. Positioning the surgical points. (A) target point for dorsal endoscopic rhizotomy (TP, transerve process, AP, accessory process, MAL, mammillary-accessary ligament, MB, medial branch); (B) the skin entry point for dorsal endoscopic rhizotomy; (C) frontal view showing the puncture needle was docked into the target positions; (D) lateral view showing the puncture needle was docked into the dorsal region of the transverse process.
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Fig. 2. Operation process of dorsal endoscopic rhizotomy (A) and normal anatomical morphology of medial branch of the dorsal ramus of the spinal nerve (B).
dorsal of the base of the transverse process and bony structures of the SAP (Fig. 2). Skin incision was sutured by absorbable suture material after endoscope and working cannula were removed. 2.3. Follow-up and medical evaluation All patients were discharged 2 days after the operation. Being blinded to the treatment assignments, the surgeon assessed each patient. The post-rhizotomic patients were followed up 1 day, 3 months, 6 months and 12 months postoperatively, respectively. During that follow up period, the patients completed the visual analog scale (VAS) questionnaire. Low back pain or referred pain was measured on a visual analog scale (VAS) (with values ranging from 0 to 10) before MBB, after MBB, immediately after the surgery (baseline) and at the end of the 3rd, 6th, and 12th month postoperatively. A higher score on the VAS equates to a higher level of pain. Percentage of pain relief (%) was calculated as: (VAS score after treatment − VAS score before MBB) × 100/VAS score before MBB. The MacNab score was recorded at 12 months postoperatively. The MacNab criteria were applied to each patient by characterizing pain relief of 75–100% as excellent, 50–74% as good, 25–49% as fair, and 0–24% as poor [17]. Success is based on an excellent, good, or fair outcome. Besides, any potential complications were also evaluated at each visit.
were males (56%) and 20 were females (44%), while in the conservative group, 6 were males (46.2%) and 7 were females (53.8%). Pains with or without the referred pain were classified according to the low back pain location. Most of the pains were 27B (46.5%) followed by 22C (37.9%). The average pre-operative VAS score of back pain for the operation group was (7.69 ± 1.06) as compared to (6.69 ± 0.75) for the conservative group, while the mean pre-operative VAS score of referred pain was (7.69 ± 1.06) for the operation group and (6.69 ± 0.75) for the conservative group, marked as the level of severe and constant pain in our questionnaire. The VAS score was found to be significantly higher in the operation group as compared to the conservative group (all P < 0.05). Twenty two percent (22%) of patients reported a duration of pain for 1 year or less, whereas 28% reported a longer duration of 1 to 4 years, and 50% suffered pain for longer than 4 years. The average duration of pain including low back pain and referred pain was significantly greater in the operation group than that in the conservative group (P < 0.05). No statistically significant difference in age, sex, type and duration of referred pain, history of lumbar spine surgery, mode of surgery was observed between the two groups (P > 0.05) (see Table 1). Fig. 3 shows no significant difference in the distribution for each joint involved between the two groups (P > 0.05). In the 45 patients underwent dorsal endoscopic rhizotomy, the surgical target were predominantly performed at the zygapophyseal joint (L3-S1) (18 cases). Fig. 4 summarizes the distribution for the levels of treatment.
2.4. Statistical analysis All analyses were performed using SPSS 11.5 software (SPSS, Chicago, IL, USA). Qualitative data were expressed as frequency and percentage. Chi-square test was used to examine the relation between qualitative variables. Normally distributed continuous data are presented as means ± standard deviation (SD) and were compared using t tests. Non-normally distributed continuous data are presented as the median and range, and were compared using the Wilcoxon rank sum test. Differences within groups between patients’ preoperative and postoperative VAS scores were analyzed for significance using one-way analysis of variance. Difference among 2 or more than 2 groups were assessed by using t tests. Differences were considered statistically significant when P < 0.05. 3. Results 3.1. Patient’s characteristics The mean age of patients receiving dorsal endoscopic rhizotomy was (61.84 ± 11.77) years, and it was (62.62 ± 19.83) years for those who underwent conservative treatment. In the operation group, 25
Table 1 Demographic characteristics. Index
Operation group
Sex (male/female)-no. Age (years) VAS score of back pain Duration of back pain (months) VAS score of referred pain Duration of referred pain (months) Type of referred pain A B C History of lumbar surgery No Yes Mode of surgery Lumbar canal decompression Lumbar fusion
25/20 6/7 61.84 ± 11.77 62.62 ± 19.83 7.69 ± 1.06* 6.69 ± 0.75 137.13 ± 135.77* 48.23 ± 71.40 5.41 ± 1.88* 4.17 ± 0.83 19.92 ± 23.27 (37) 14.25 ± 23.37 (12)
Conservative group
8 21 16
1 6 6
33 12
8 5
4 8
1 4
* P < 0.05, versus conservative group; A, patients whose pain was only in the lower back; B, patients whose pain was predominantly in the low back, but also have radiated into the buttocks and legs; C, patients whose pain was predominantly in the low back, but also have spread into the knee or even lower.
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Z.-Z. Li et al. / Clinical Neurology and Neurosurgery 126 (2014) 11–17 Table 4 MacNab score of the 1 year postoperative evaluation in two groups. MacNab score
Operation group
Excellent Good Fair Poor
27 (60%) 17 (37.8%) 1 (2.2%) 0
Conservative operation 0 (0%) 0 (0%) 6 (46.2) 7 (53.8)
3.2. Postoperative outcomes In the operation group, all the 45 patients completed the endoscopic dorsal endoscopic rhizotomy. During the follow-up period, no complications were observed. During operation, we observed anatomical variants of the dorsal ramus of the spinal nerve, including the number, the thickness and the positioning of the dorsal ramus (Fig. 5). Table 2 summarized the VAS score of the low back pain and referred pain before MBB, after MBB, immediately after surgery and at 3, 6, and 12 months postoperatively in the two groups. In the operation group, the low back pain and referred pain showed a lower score at any time point postoperatively (P < 0.01), as compared to the VAS pain score obtained before MBB, while showed no statistical difference (P > 0.05) as compared to the VAS pain score obtained after MBB. In the conservative group, the low back pain and referred pain showed a lower score at any time point postoperatively (P < 0.01), as compared to the VAS pain score obtained before MBB, while showed a higher score (P > 0.05) as compared to the VAS pain score obtained after MBB. The VAS back or referred pain score in the two groups was not statistically different at any time point postoperatively (P > 0.05). Table 3 illustrated therapeutic procedural characteristics with average degree of pain relief after MBB and at 3, 6, and 12 months postoperatively in the two groups. There was not statistically different with respect to the degree of pain relief (back/referred) after MBB in the two groups. The relief of pain (back/referred) at any time point postoperatively in the operation group was higher in comparison to that in the conservative group (t test, all P < 0.01). As shown in Table 4, excellent/good McNab outcomes of the 1 year postoperative evaluation in the operation group were
Fig. 3. Range and segment distribution of the medial branch blocks (MBB) in two groups. Group A, operation group; Group B, conservative group.
Fig. 4. Distribution of surgical target in patients receiving dorsal endoscopic rhizotomy. Wilcoxon test showed no significant difference between the two sides (P > 0.05). L, left side; R, right side.
Table 2 VAS score change of the back pain and referred pain (means ± standard deviation). Time point
Operation group
Conservative group
Back pain Before MBB After MBB Postoperative 1 day Postoperative 3 months Postoperative 6 months Postoperative 12 months 1
7.66 0.47 0.42 0.51 0.58 0.69
± ± ± ± ± ±
Referred pain
1.06 0.55 0.58* 0.99* 1.03* 1.00*
5.41 1.00 0.49 0.46 0.51 0.41
± ± ± ± ± ±
Back pain
1.88 1.27 0.80* 0.73* 0.69* 0.50*
6.70 0.62 1.85 5.15 5.85 5.38
± ± ± ± ± ±
0.75 0.51 0.90* , # 1.21* , # 1.57* , # 1.26* , #
Referred pain 4.17 0.75 0.83 2.92 3.50 3.00
± ± ± ± ± ±
0.83 0.62 0.72* , # 1.08* , # 1.09* , # 1.04* , #
MBB, medial branch block. * P < 0.01, versus before MBB. # P < 0.01, versus after MBB. Table 3 Comparison of relief of pain (back/referred) at different time point in the two groups (means ± standard deviation). Time point
Back pain Operation group
After MBB Post 1 day Post 3 months Post 6 months Post 12 months
93.70 94.26 93.27 92.36 90.82
± ± ± ± ±
7.54 7.98* 12.57* 13.19* 13.05*
MBB, medial branch block; Post, postoperative. * As compared to conservative group, P < 0.01.
Referred pain Conservative group 90.93 23.26 23.26 13.55 22.25
± ± ± ± ±
7.58 15.21 15.21 17.40 11.96
Operation group 81.18 90.02 89.67 87.92 90.29
± ± ± ± ±
21.88 18.95* 19.17* 19.19* 12.76*
Conservative group 82.36 31.11 31.11 15.97 27.92
± ± ± ± ±
13.53 15.03 15.03 19.29 20.59
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Fig. 5. Endoscopic anatomy and its variants of dorsal ramus of the spinal nerve (red arrows). (A) Bifurcated branch variants of dorsal ramus of the spinal nerve; (B) multibranch variants of dorsal ramus of the spinal nerve; (C) thinned anatomical variants of dorsal ramus of the spinal nerve; (D) anatomical variant of dorsal ramus of the spinal nerve covered by periosteum. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
recorded as 97.8%, which was significantly higher than that in the conservative group (P < 0.01). 4. Discussion Chronic low back pain is hard to diagnose, because history and physical examination associated with radiological studies (X-ray, CT, and MRI) are unspecific for the disease [18]. Lumbar facet joints are synovial joints consisting of diarthrodial articulations between posterior elements of adjacent vertebrae and are innervated by medial branches of the dorsal rami from spinal nerves. It is generally assumed that facetogenic CLBP is not as acute as nerve root pain and is usually characterized as a deep and dull pain, thus its accurate loci are fairly difficult to target. This syndrome is characterized clinically by chronic back pain, which deteriorates during rotation or torsion movements, with selective pressure soreness at the level of facet involved. It can radiate into the buttocks and ipsilateral legs, or even worse, spread into the knee or even the foot. The patients included in this study had mechanical low back pain, whose lumbar pain increased during rotation or extension movements. These characteristics have an indicative value for the diagnosis of facetogenic low back pain. Facetogenic lumbar pain is usually accompanied by referred pain, i.e., lumbar facet joints are implicated as the source of chronic low back pain. Further, facet joints of the lumbar spine have been shown to be capable of causing pain in the low back with referred pain to the lower extremities in normal volunteers [19]. The location of referred pain is correlated with the segmental distribution
in lumbar zygapophysial facet joint. Referred pain of upper lumbar facet joint was located at lumbar region or adjacent to the posterior iliac crest, whereas the pain of the lower lumbar facet joint usually spread into the buttocks. However, lesion segment cannot be speculated from the location of referred pain due to the overlap of the range of the referred pain among different segments. Despite the lack of quantitative research, a pervious study showed that the (involved) distance of the referred pain was positively correlated with the stimulus intensity, which means the stronger the harmful stimulus, the further the referred pain will spread [20]. Previous study reported that experimentally induced referred pain could cause the increase of electromyographic activity; pain of the medial branch of the dorsal rami of lumbar nerve is often accompanied by involuntary activity of the muscles of the lower 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 of pain after MBB. It was consistent with the findings as described previously [20]. Diagnostic blocks are the only means by which the source of a patient’s pain can be traced to their zygapophysial joints [21,22]. Single, diagnostic blocks are not valid [23] and carry a false-positive rate of between 25% and 41% [21,24,25]. To reduce the likelihood of false-positive responses, repeated blocks are required. Comparative local anesthetic blocks using Lidocaine or Bupivacaine are a suitable candidate of control [26,27]. Previous study suggested that comparative blocks were found to have a sensitivity of 100%, yet only with a specificity of 65% [27]. Our study demonstrated that
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the excellent/good McNab outcomes of the 1 year postoperative evaluation in the operation group were recorded as 97.8%, which was higher than the findings reported previously, indicating that dorsal endoscopic rhizotomy improves the surgical outcomes significantly. Currently, there has been no consensus on the number and levels of segments. Segment selection is usually speculated according to the location of the referred pain and local tenderness. Using a comparative double block control, Manchukonda et al. [28] reported that blocking the L2-5 (namely L3-S1 facet joint) medial branch of the dorsal ramus of the spine nerve was the most effective modality in the diagnosis of the lumbar facet joint pain. In our study, the low back pain mostly arises from the facet joints (L3-S1), which was consistent with the previous study. No form of conservative treatment including drugs, physical therapy, or cognitive-behavioral therapy has ever been tested for efficacy for proven lumbar facet joint pain. In our study, the relief of pain was lower than 30% at any time point postoperatively after 1-year follow-up, which was consistent with the findings of previous report. Percutaneous lumbar medial branch neurotomy has been indicated as the effective methods for the treatment of facetogenic chronic back pain [29]. The theoretical basis of this neurotomy is to denature the nerves innervating the painful joint and block the afferent pathway of the source of the chronic low back pain. A previous study reported that the effectiveness of percutaneous lumbar medial branch neurotomy (LMBN) is only 43–80% [30,31]. Anatomical variations of the medial branch of dorsal ramus anatomy, incorrect placement of electrode, incomplete ablation, and nerve regeneration may be the important factors affecting the effectiveness of this neurotomy. In this study, we found multiple anatomic variants of the medial branch anatomy. In clinical practice, percutaneous puncture technique may not achieve satisfactory therapeutic benefit if it fails to reach the location of the anatomic variants of the nerve. Endoscope-assisted technology can contribute to the denaturing of the normal and varied medial branches of the nerve. Relief after LMBN typically lasts between 6 and 12 months [32]. Pain recurs when the nerves regenerate, but relief can be reinstated by repeated neurotomy [32]. Successful treatment which repeated two and three times has been reported [32], however, no limit has yet been established as to the number of times that the procedure can be successfully repeated to maintain relief of pain. Endoscopic-assisted dorsal ramus rhizotomy can directly denature the medial branch and block the nerve regeneration of the medial branch, which significantly reduces the possibility of the nerve regeneration and results in a low recurrence of pain. In our study, we found that the excellent/good McNab outcomes of the 1 year postoperative evaluation in the operation group were recorded as 97.8%, with a recurrence rate of only 2.2%, suggesting that our treatment technology achieved good therapeutic results. Previous study reported that the satisfaction rate was 41% in patients with a history of laminectomy, whereas it was only 27% in patients with a history of lumbar spine fusion after percutaneous LMBN [33]. In our study, 17 patients had a history of lumbar spine surgery, of which 12 cases received DER treatment. The excellent/good McNab outcomes after a 1-year follow-up in the operation group were recorded as 91.7% (11/12). In contrast the other 5 patients in the conservative group did not achieve such therapeutic benefit. These findings suggested that the DER can still achieve a desirable therapeutic effect despite the fact of a failed back surgery syndrome. Percutaneous lumbar medial branch neurotomy may lead to a few minor complications, such as painful dysesthesias, painful anesthesia, hyperesthesia and nerve root injury. In our study, however, no complication was observed, indicating that endoscopic-assisted technique has increased the accuracy and
thoroughness of neurotomy and ameliorated the potential occurrence of surgery-related complications. 5. Conclusion Dorsal endoscopic rhizotomy is proposed as a safe and effective treatment for facetogenic CLBP, allowing the achievement a better clinical outcome than the conventional conservative treatment. Further studies with a larger sample size of patients and a longer period of follow-up are anticipated to further validate and support the efficacy of this technique. Conflict of interest The authors have no conflicts of interest to declare. Acknowledgements None. References [1] Bogduk N, Twomey L. The zygapophysial joints. Clinical anatomy of the lumbar spine and sacrum; 1997. p. 33–41. [2] Glover J. Arthrography of the joints of the lumbar vertebral arches. Orthop Clin North Am 1977;8:37–42. [3] Van Zundert J, Vanelderen P, Kessels A, van Kleef M. Radiofrequency treatment of facet-related pain: evidence and controversies. Curr Pain Headache Rep 2012;16:19–25. [4] Cohen SP, Raja SN. Pathogenesis, diagnosis, and treatment of lumbar zygapophysial (facet) joint pain. Anesthesiology 2007;106:591–614. [5] Manchikanti L, Singh V, Falco FJ, Cash KA, Pampati V. Evaluation of lumbar facet joint nerve blocks in managing chronic low back pain: a randomized, doubleblind, controlled trial with a 2-year follow-up. Int J Med Sci 2010;7:124–35. [6] Carette S, Marcoux S, Truchon R, Grondin C, Gagnon J, Allard Y, et al. A controlled trial of corticosteroid injections into facet joints for chronic low back pain. N Engl J Med 1991;325:1002–7. [7] Schulte T, Pietilä T, Heidenreich J, Brock M, Stendel R. Injection therapy of lumbar facet syndrome: a prospective study. Acta Neurochir (Wien) 2006;148:1165–72. [8] Manchikanti L, Manchikanti K, Manchukonda R, Cash K, Damron K, Pampati V, et al. Evaluation of lumbar facet joint nerve blocks in the management of chronic low back pain: a preliminary report of a randomized, double-blind controlled trial: Clinical Trial NCT00355914. Pain Physician 2007;10:425. [9] Manchikanti L, Manchikanti KN, Damron K, Pampati V. Effectiveness of cervical medial branch blocks in chronic neck pain: a prospective outcome study. Pain Physician 2004;7:195–202. [10] Tomé-Bermejo F, Barriga-Martín A, Martín JLR. Identifying patients with chronic low back pain likely to benefit from lumbar facet radiofrequency denervation: a prospective study. J Spinal Disord Tech 2011;24:69–75. [11] Streitberger K, Müller T, Eichenberger U, Trelle S, Curatolo M. Factors determining the success of radiofrequency denervation in lumbar facet joint pain: a prospective study. Eur Spine J 2011;20:2160–5. [12] Physicians ASoIP. Interventional techniques: evidence-based practice guidelines in the management of chronic spinal pain; 2007. [13] Boswell MV, Shah RV, Everett CR, Sehgal N, Mckenzie-Brown AM, Abdi S, et al. Interventional techniques in the management of chronic spinal pain: evidencebased practice guidelines. Pain Physician 2005;8:1–47. [14] Boswell MV, Colson JD, Sehgal N, Dunbar EE, Epter R. A systematic review of therapeutic facet joint interventions in chronic spinal pain. Pain Physician 2007;10:229–53. [15] Manchikanti L, Singh V, Vilims BD, Hansen HC, Schultz DM, Kloth DS. Systematic review. Pain Physician 2002;5:405–18. [16] Bogduk N. Evidence-informed management of chronic low back pain with facet injections and radiofrequency neurotomy. Spine J 2008;8:56–64. [17] MacNab I. Negative disc exploration: an analysis of the causes of nerve-root involvement in sixty-eight patients. J Bone Joint Surg Am 1971;53:891–903. [18] Masala S, Nano G, Mammucari M, Marcia S, Simonetti G. Medial branch neurotomy in low back pain. Neuroradiology 2012;54:737–44. [19] Manchikanti L, Singh V, Falco F, Cash KA, Pampati V. Lumbar facet joint nerve blocks in managing chronic facet joint pain: one-year follow-up of a randomized, double-blind controlled trial: Clinical Trial NCT00355914. Pain Physician 2008;11:121–32. [20] Mooney V, Robertson J. The facet syndrome. Clin Orthop 1976;115:149–57. [21] Schwarzer A, Aprill C, Derby R, Fortin J, Kine G, Bogduk N. The false-positive rate of uncontrolled diagnostic blocks of the lumbar zygapophysial joints. Pain 1994;58:195–200.
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