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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 50  |  Issue : 4  |  Page : 125-130

Correlation between lumbar lordosis and the treatment of chronic low back pain with pulsed radiofrequency applied to the L2 dorsal root ganglion


1 Division of Neurosurgery, Taipei Tzuchi Hospital, The Buddhist Tzuchi Medical Foundation, Taipei, Taiwan
2 Department of Surgery, Taipei Tzuchi Hospital, The Buddhist Tzuchi Medical Foundation, Taipei, Taiwan
3 Division of Neurosurgery, Taipei Tzuchi Hospital, The Buddhist Tzuchi Medical Foundation, Taipei; School of Medicine, Buddhist Tzu Chi University, Hualien, Taiwan
4 School of Medicine, Buddhist Tzu Chi University, Hualien; Department of Anesthesiology, Taipei Tzuchi Hospital, The Buddhist Tzuchi Medical Foundation, Taipei, Taiwan

Date of Submission10-Oct-2016
Date of Decision19-Nov-2016
Date of Acceptance22-Dec-2016
Date of Web Publication19-Jul-2017

Correspondence Address:
Chun-Jen Huang
Department of Anesthesiology, Taipei Tzu Chi Hospital, 289, Jianguo Road, Sindian District, New Taipei City 231
Taiwan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/fjs.fjs_43_17

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  Abstract 

Background: Percutaneous pulsed radiofrequency (PRF) applied to the L2 dorsal root ganglion (DRG) is an alternative procedure for treating patients with chronic discogenic pain. It is assumed that afferent nerve fibers innervating the degenerated disc and facet joint might travel in the same pathway and finally enter into the L2 DRG. Blocking the L2 DRG with PRF might alleviate discogenic pain and facet joint pain concurrently.
Purpose: The purpose of this study was to investigate the correlation between different types of lumbar lordosis (LL) and the treatment of chronic low back pain with PRF applied to the L2 DRG.
Materials and Methods: Between 2008 and 2013, 84 patients (29 men and 55 women) were enrolled. Their mean age was 56.03 ± 9.04 years. All patients suffered from low back pain for more than 6 months that worsened on prolonged sitting or standing and did not improve with at least 3 months of conservative treatment. LL was classified into four types based on Roussouly's classification. The L2 DRG was blocked with 2-Hz PRF waves lasting for 120 s at 45 V with the temperature of the electrode tip not above 42°C. The functional outcomes were assessed pre- and post-operatively using a visual analog scale (VAS) and the Oswestry Disability Index (ODI).
Results: Twenty-four patients were Type 1 LL, 26 were Type 2 LL, 21 were Type 3 LL, and 13 were Type 4 LL. The mean age of patients with each type of LL was type 1 (56.63 ± 12.09 years), Type 2 (55.39 ± 11.05 years), Type 3 (55.86 ± 11.40 years), and Type 4 (56.54 ± 12.73 years). There were similar improvements in the VAS and ODI scores for all LL types. Two patients experienced cerebrospinal fluid leakage when the needle was moved toward the L2 DRG, but neither patient experienced a neurological deficit.
Conclusion: PRF applied to the L2 DRG is an alternative procedure for treating patients with chronic low back pain, regardless of which type of LL the patients have. Chronic low back pain, including discogenic pain and facet joint pain, may be treated by PRF applied to the L2 DRG.

Keywords: Chronic low back pain, discogenic pain, facet joint pain, L2 dorsal root ganglion, lumbar lordosis, pulsed radiofrequency, Roussouly's classification


How to cite this article:
Hsu HT, Chang SJ, Huang KF, Tai PA, Li TC, Huang CJ. Correlation between lumbar lordosis and the treatment of chronic low back pain with pulsed radiofrequency applied to the L2 dorsal root ganglion. Formos J Surg 2017;50:125-30

How to cite this URL:
Hsu HT, Chang SJ, Huang KF, Tai PA, Li TC, Huang CJ. Correlation between lumbar lordosis and the treatment of chronic low back pain with pulsed radiofrequency applied to the L2 dorsal root ganglion. Formos J Surg [serial online] 2017 [cited 2017 Sep 19];50:125-30. Available from: http://www.e-fjs.org/text.asp?2017/50/4/125/211082




  Introduction Top


It is estimated that about 60%–80% of people in the general population experience at least one episode of low back pain in their life, and 10%–20% of these cases become chronic.[1] The current view is that occupation,[2] physical activity,[3] force injuries,[4] smoking,[5] repetitive physical loading,[6] sex,[7] and body weight [8] can affect the risk for low back pain. In addition, genetic factors [9] may affect the risk for disc degeneration. Studies of the etiologies of chronic low back pain indicate that lumbar disc degeneration and facet joint disease are the most common causes.[10],[11]

Roussouly et al. prospectively studied 160 healthy adults and categorized lumbar lordosis (LL) into four types. They found that patients with symptomatic disc herniations were mostly Type 1 LL or 2 LL and patients with spinal canal stenosis were mostly Type 4 LL. Type 3 LL patients rarely reported significant problems.[12] Goel observed that facet instability, rather than disc herniation, could be the main factor that initiates a torrent of events leading to spinal canal stenosis.[13] Based on these observations, it appears that discogenic pain, which accounts for about 39% of chronic low back pain,[10] is more prevalent in patients with Type 1 LL and Type 2 LL, whereas facet joint pain, which accounts for about 21%–41% of chronic low back pain,[11] is more common in Type 4 LL patients.

The dorsal root ganglion (DRG) is within an intervertebral foramen (IVF) of the lumbar spine. Marginal branches of the DRG radiate to different nerves, including the spinal nerve (connecting to peripheral tissues), sinuvertebral nerve (connecting to the spinal canal), and ramus communicans (connecting to the paravertebral sympathetic trunk). The intervertebral disc receives nerve branches from the sinuvertebral nerve and ramus communicans, whereas the facet joint receives medial branches from the dorsal rami of the spinal nerve [Figure 1].[14],[15],[16]
Figure 1: Schematic drawing of the spinal cord and segmental spinal innervation. The red arrow indicates the medial branch from the primary dorsal ramus. The purple arrow shows the sinuvertebral nerve. The black arrow denotes the dorsal root ganglion. The blue arrow designates the sympathetic chain

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Previous research has verified that most afferent fibers from the lower lumbar discs originate in the sinuvertebral nerve, proceed through the ramus communicans and lumbar sympathetic chain, and then enter the spinal cord through the L2 ramus communicans and L2 spinal nerve roots.[17],[18] In view of these anatomical relationships, Tsou et al. applied pulsed radiofrequency (PRF) to the L2 DRG of patients with chronic lumbar discogenic pain. They reported relief from back pain during the 3-year follow-up period.[19] Blocking the L2 DRG may also enervate the medial branch originating from the dorsal rami and relieve facet joint pain although this hypothesis has not yet been examined. The aim of this study was to investigate the correlation between different types of LL and the treatment of chronic low back pain with PRF applied to the L2 DRG.


  Materials And Methods Top


This retrospective study was approved by the local Institutional Review Board and informed consent was obtained from all the individuals. Diagnoses of chronic low back pain and selection of patients were made by a senior neurosurgeon (HTH). All included patients were more than 20-year-old, had low back pain for more than 6 months that worsened upon prolonged sitting or standing, and failed to improve after at least 3 months of conservative treatment. Patients were excluded if they had sagittal imbalance, spinal listhesis, infection, tumor, stenosis, or disc herniation causing nerve root compression.

Between 2008 and 2013, 84 patients (29 men and 55 women, mean age: 56.03 ± 9.04 years) were enrolled. All patients were examined with lumbar X-ray and magnetic resonance imaging (MRI). The MRIs of all enrolled patients revealed no evidence of nerve root compression related to stenosis, disc herniation, or spondylolisthesis, except dehydration of at least one intervertebral disc or narrowing of the facet joint space, with mild to marked osteophyte formation from L2 to S1.

According to the classification defined by Roussouly et al.,[12] LL of all patients can be divided into four types based on sacral slope (SS) and the number of vertebral levels contained in the lordotic segment. A Type 1 LL has an SS <S35° and generally has a short LL, with lordotic levels consisting of three vertebrae or less; the vertex of the LL is seated in the midpoint of the L5 vertebral body. A Type 2 LL has an SS <S35° and a longer LL, with lordotic levels comprising more than three vertebrae; the vertex of the LL is located at the bottom of the L4 vertebral body. A Type 3 LL has an SS more than 35° but <45°; the vertex of the LL is in the midpoint of the L4 vertebral body. A Type 4 LL has an SS >45° and a high pelvic incidence (PI); the vertex of the LL is at the bottom of the L3 vertebral body.

The spinal sagittal balance of each patient was evaluated using 36-inch spinal films (anteroposterior and lateral views). The patient was positioned so that the upper arms were close to the anterior chest, the hands were on the ipsilateral clavicles, and the legs were straight in a standing position. A normal sagittal balance is defined as a C7 plumb line within 6 cm from the posterior-superior corner of the S1 vertebrae; a positive sagittal balance is defined by a length >6 cm.

Each patient was placed in a prone position before PRF treatment. The skin over the operative area was disinfected and anesthetized locally with 2% lidocaine. Under the guidance of a C-arm fluoroscope, a 10-cm, 22-gauge, sliced-tip cannula and a 1-cm active tip electrode was moved toward the L2 DRG, near the IVF. A PRF generator from Baylis Medical Devices Co., was used. The ganglion was localized when sensory stimulation (50 Hz) replicated the patient's pain at 0.5 V or less. The needle was pushed deeper into the IVF until the patient reported a tingling sensation. Then, 2-Hz PRFs were generated for 120 s at 45 V, while ensuring that the temperature of the electrode tip was not above 42°C. The same procedure was repeated at the L2 DRG on the contralateral side.

The functional outcomes were measured by comparison of pre- and postoperative scores on a visual analog scale (VAS, range: 0–10) for pain and the Oswestry Disability Index (ODI, range: 0–100). The influences of age, sex, smoking, and body mass index (BMI) on these indices were also assessed. Examinations were conducted at an outpatient clinic before treatment and 1 week after treatment by the same neurosurgeon who performed the procedure. A trained nurse examined the patients at 3, 6, 9, 12 months and yearly postoperatively under the supervision of the same neurosurgeon.

Statistical analysis

A paired t-test was used to evaluate the therapeutic efficacy of PRF treatment. A mixed model was applied to assess the effect of sex, age, smoking, BMI, and type of LL on treatment efficacy. A positive significant difference was assumed at a P < 0.05. All statistical analyses were performed using MedCalc Statistical Software version 14.12.0.

Ethical approval

The study was conducted in accordance with the Declaration of Helsinki and was approved by the local ethics committee of the institute. Informed written consent was obtained from all patients prior to their enrollment in this study.


  Results Top


Based on Roussouly's classification, the LL of 24 patients was classified as Type 1, 26 patients as Type 2, 21 patients as Type 3, and 13 patients as Type 4. The patients in these different groups had similar ages (Type 1: 56.63 ± 12.09 years, Type 2: 55.39 ± 11.05 years, Type 3: 55.86 ± 11.40 years, Type 4: 56.54 ± 12.73 years). Postoperative 36-inch spinal films showed the C7 plumb line was an average of 2.5 cm in length (range: 0.2–4.5 cm) away from posterior-superior corner of the S1 vertebrae, indicating a normal sagittal balance.

Analysis of VAS scores for pain indicated significant reductions of low back pain during the 3-year follow-up for patients with all 4 types of LL [Figure 2]. Examination of ODI scores for disability showed obvious improvements of functional outcome in the first 6-month follow-up for patients with all 4 types of LL [Figure 3]. We also analyzed the effect of different patient characteristics on the reduction in VAS score for pain [Table 1] and ODI score [Table 2]. The type of LL, age, smoking, and BMI had no significant effect on VAS or ODI scores. Nonetheless, males had a significant decline of VAS scores (but not ODI scores) than females (P = 0.02).
Figure 2: Line graph depicts the difference of visual analog scale score for four types of lumbar lordosis before and after pulsed radiofrequency treatment over time

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Figure 3: Line graph depicts the difference of Oswestry Disability Index score for four types of lumbar lordosis before and after pulsed radiofrequency treatment over time

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Table 1: Effect of sex, type of lumbar lordosis, smoking, body mass index, and age on improvement of the visual analog scale score for pain after pulsed radiofrequency treatment

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Table 2: Effect of sex, type of lumbar lordosis, smoking, body mass index, and age on improvement of the Oswestry Disability Index score after pulsed radiofrequency treatment

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Cerebral spinal fluid (CSF) was observed leaking from the cannulas of two patients while the needle was being directed toward the DRG. This leakage ceased immediately after adjusting the location of the needle tip. After the procedure, one of these two patients suffered from dizziness because of CSF leakage and the other patient was asymptomatic. The patient with dizziness recovered well without neurological deficit after resting in a supine position for about 1 h.


  Discussion Top


Our study showed that PRF applied to the L2 DRG may be an alternative method for treating patients with chronic low back pain, regardless of which type of LL the patients have. In fact, based on VAS scores for pain and ODI scores, there were no significant differences in the alleviation of back pain among patients with the 4 different types of LL. Age, BMI, and smoking were unrelated to the PRF treatment in our patient population. However, males had significant improvements for pain than females in terms of VAS scores. The results indicated that patients with chronic low back pain, either discogenic pain or facet joint pain, may be treated by PRF applied to the L2 DRG. The complication rate was low. Only two cases had procedure-related CSF leakage which ceased immediately after the position of the needle tip was relocated. Neither patient suffered from neurological deficits although one complained of short-term dizziness.

A variety of interventions to treat chronic low back pain have been employed and various outcomes were reported. The treatments used for discogenic pain include intradiscal electrothermal therapy,[20] spinal fusion,[21] and artificial disc replacement.[22] Tsou et al. proposed the treatment of discogenic pain by applying PRF to the L2 DRG.[19] Most physicians have relied on provocative discography to determine whether a patient's back pain is discogenic in origin [23],[24] although the reliability of provocative discography remains uncertain. Ohtori et al.[25] recommended injecting a small amount of bupivacaine into the painful disc to confirm discogenic pain.[17] Tsou et al.[19] used MRI to determine that discogenic pain depended on dehydration of the intervertebral disc and observed that a patient could not tolerate prolonged sitting or standing if the pain was provoked by lumbar hyperflexion. However, in the light of the authors' inclusion criteria, which were not very stringent, it is reasonable to speculate that some of the included patients did not suffer from discogenic pain; in particular, some of them may have had facet joint pain.

Previous research showed that lumbar facet joints are the source of low back pain in 21%–41% of patients with chronic low back pain.[11] Each facet joint has dual innervation by medial branches from the posterior primary rami at the same level and one level above the zygapophysial joint.[26] The diagnosis and treatment for lumbar facet joint pain remains controversial. The literature shows no correlation between findings of facet joint degeneration from computed tomography or MRI and the occurrence of facet joint pain.[27] Radiofrequency denervation of the medial branch from the dorsal rami is an effective method for the treatment of facet joint pain, and most authors report sustained relief in 50%–80% among patients without previous back surgery.[28],[29]

We retrospectively reviewed the records of patients to assess pain relief following application of PRF treatment to the L2 DRG but did not perform provocative discography or the diagnostic facet block test to confirm whether the source was a degenerated disc or a facet. Based on Roussouly classification, the PI of the Type I and Type II LL are smaller than that of Type IV, indicating the spinal alignment of Type I and Type II LL are straighter. Theoretically, a straighter spinal alignment tends to produce axial and flexion compression on the discs and results in degenerative disc disease. As for the Type IV LL, the compression force is likely to be shifted from the discs to the facet joints due to a larger PI, leading to instability of the facet joints and facet joint pain. We assumed that afferent nerve fibers innervating the facet joints pass through the medial branch of the dorsal rami and travel the same pathway as nerve fibers innervating the discs. The results showed that blocking the L2 DRG with PRF provides an alternative way to treat discogenic pain and facet joint pain concurrently. Nonetheless, further investigations, such as a prospective controlled study, are needed to confirm the observations.

A limitation of this study is that it included a relatively small number of patients with chronic low back pain, so the proportions of patients with different types of LL may not be representative of all patients with chronic low back pain from the general population. This may have led to a bias and might explain our higher rate of chronic low back pain in Type 3 LL patients although Roussouly et al. reported fewer complaints of low back pain in those with Type 3 LL.[12]


  Conclusion Top


PRF applied to the L2 DRG is an alternative procedure for treating patients with chronic low back pain, regardless of which type of LL the patients have. Chronic low back pain, including discogenic pain and facet joint pain, may be treated by PRF applied to the L2 DRG.

Financial support and sponsorship

The study was supported by grants from the Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation (TCRD-TPE-104-52 and TCRD-TPE-103-RT-7).

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

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