A comparative study of continuous versus pulsed radiofrequency discectomy for management of low backache: Prospective randomized, double-blind study.

BACKGROUND: Radiofrequency (RF) is a minimally invasive target-selective technique that has been used with success for many years in the treatment of different pathologies, such as low back pain, trigeminal neuralgia, and others. AIM: The aim of this study is to compare different mode of RF - continuous RF (CRF) versus pulsed RF (PRF) along with steroid in the management of low back pain of discogenic origin. SETTING AND
DESIGN: Prospective, randomized, double-blind trial.
MATERIALS AND METHODS: Forty patients with chronic discogenic low back pain were randomized to receive CRF plus intradiscal triamcinolone 40 mg (Group 1) or to receive PRF plus intradiscal triamcinolone 40 mg (Group 2). Outcome measured includes immediate as well as long-term pain relief using visual analog scale, the Oswestry Disability Index and straight leg raising test. STATISTICAL ANALYSIS: The continuous variables were compared by one-way analysis of variance test. Discrete variables were compared by Fisher's exact test/Chi-square test/Student's t-test, whichever appropriate. The value of P < 0.05 was considered statistically significant.
RESULTS: There was a significant decrease in pain score after CRF without any added side effect. Pain relief after PRF was insignificant.
CONCLUSION: CRF with steroid seems to be better for treatment of chronic discogenic low back pain than PRF with steroid.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Chronic low back pain is a common problem and more than 80% of the global population will experience low back pain at least once in their life time. Low back pain can originate from the lumbar facet joints, the sacroiliac joint, the intervertebral discs (discogenic low back pain), and the coccyx. Chronic low back pain is typically defined as pain in the low back that persists for ≥3 months. Of the population with acute low back pain, approximately 2–34% will eventually experience chronic low back pain.[12] Conservative treatment options for chronic low back pain may include pharmacotherapy, massage, physiotherapy, spinal cord stimulation, and educational or psychological therapies (e.g., cognitive behavioral therapy, support groups, educational sessions).[345] If conservative treatments are ineffective, more invasive methods, such as steroid injections, nerve blocks, cryoablation, radiofrequency ablation (RFA), or surgery can be attempted.[678]

RFA may be continuous RF (CRF) or pulsed RF (PRF). CRF uses high-frequency alternating current to induce coagulative necrosis in the target tissue. Tissue destruction occurs with probe temperatures between 60°C and 80°C. Because tissue heating decreases rapidly with distance from the electrode tip, CRF lesions are well-circumscribed, thus offering an advantage over chemical neurolysis. With CRF, the magnitude of tissue destruction is related to the temperature of the tissue, as well as the size of the electrode and duration of the procedure. In contrast, PRF uses RF current in short (20 ms), high-voltage bursts; the “silent” phase (480 ms) of PRF allows time for heat elimination, generally keeping the target tissue below 42°C. The mechanism by which PRF controls pain is unclear, but it may involve a temperature-independent pathway mediated by a rapidly changing electrical field.

Review of previous literature showed that different modes of RF were compared but none of the studies compared along with steroid. We hypothesized that combining intradiscal steroid along with RF may improve pain relief.

Hence, we plan this study to compare different mode of RF (CRF vs. PRF) along with intradiscal steroid in the management of low back pain of discogenic in origin.

MATERIALS AND METHODS

After Institutional Ethical approval and written informed consent, forty patients aged 18–60 years, of either sex, of American Society of Anesthesiologists (ASA) Grade I or II, presenting with low back pain secondary to discogenic in origin as evidenced by clinical and radiological examination (X-ray spine and magnetic resonance imaging [MRI]), were included in this prospective, randomized controlled, double-blind study from May 2011 to April 2013. Patient included in this study were having acute radicular pain (visual analog scale [VAS] >4) resistant to conservative management for at least 3 months, with MRI contained disc herniation correlating with patient symptoms. Patient with history of local site infection, tumor, fracture, spondylolisthesis more than 2 levels, severe motor deficit, sphincter disturbances, spinal stenosis on MRI, history of open disc surgery at suspected level and history of any uncontrolled medical disease were excluded from the study.

All patients were randomly (computer generated randomization and concealment via sealed opaque envelope technique) assigned to two equal groups: Group 1 to receive CRF plus intradiscal triamcinolone 40 mg and Group 2 to receive PRF plus intradiscal triamcinolone 40 mg.

The patient was admitted on morning day of procedure with 4 h fasting. On arrival to the operating theater, standard monitors were placed and baseline parameters recorded. The procedure was performed under strict asepsis, mild sedation with midazolam 1–2 mg or fentanyl 25–50 mcg as and when required with local anesthesia. All procedures were done by two specialist pain physicians with a backup anesthesiologist for any type of emergency.

Group 1 in prone position, 20-gauge, 15 cm RF cannula (BMC, Montreal, QC, Canada) with 10 mm active tip for CRF ablation is placed inside disc under image in posterior-lateral-oblique view. The needle placement in the center of disc was confirmed using anteroposterior and lateral fluoroscopic views. Confirmation of correct position of RF needle was accomplished by stimulation at 2 and 50 Hz for motor and sensory respectively, which is not expected to give a response at <2 V. Thereafter, discography was performed with 0.5 ml nonionic contrast to evaluate annular integrity and to know about provocative discogenic test. A positive provocative discogenic test is diagnostic of definitive disc pathology. Patients having an annular tear with contrast spreading into epidural space were terminated from the study. After discography, 2 ml of 2% lignocaine was injected, and RF probe was introduced and CRF ablation was done at 80 degree for 3.5 min. After the RFA 40 mg triamcinolone was given into the disc [Figure 1].

Figure 1

Radiofrequency generator

In Group 2 procedure was done like Group 1 except after discography and injection of 2 ml of 2% lignocaine, RF generator was operated in PRF mode for 15 min followed by 40 mg triamcinolone was given into the disc.

Outcome measured includes immediate as well as long-term pain relief using VAS 0–10 cm 0 = no pain and 10 worst imaginable pain, the Oswestry Disability Index (ODI) before and after treatment and improvements in neurological status - straight leg raising test (SLR), spinal tenderness, improvements in sensory symptoms, and motor power. Complication like pain at injection site, infection at injection site, and discitis were also observed.

Statistical analysis

The statistical analysis was performed with IBM SPSS Statistics for Windows, Version 16.0 (IBM Corp., Armonk, NY, USA). The continuous variables were compared by one-way analysis of variance test. Discrete variables were compared by Fisher's exact test/Chi-square test/Student's t-test, whichever appropriate. P < 0.05 was considered statistically significant.

RESULTS

Out of 48 patients, forty patients completed the study successfully and the study groups were comparable in terms of demographic profile, baseline VAS, ASA status, duration of illness, nature of pain, and subjective pain score [Table 1]. Eight patients who do not meet the inclusion criteria were excluded from the study [Figure 2].

Table 1

Demographic and baseline parameter

Figure 2

Flow chart of patient studied

On comparing VAS from baseline, it was seen that in Group 1, there was a significant decrease in VAS in postprocedure day 1 followed by gradual decrease in VAS over next 6 months [Figure 3]. In Group 2, there was an insignificant decrease in VAS in postoperative day 1 followed by gradual deterioration of score over 6 months. In comparison between Groups 1 and 2, there was a significant difference in VAS from day 1 onward [Table 2].

Figure 3

Visual analog scale at different time interval between two groups

Table 2

Visual analog scale at different time interval between two groups (n=20)

Baseline ODI comparison between groups is insignificant. The decrease in ODI in Group 1 is significant on day 1 and there is significant fall in ODI from day 1 to 6-months period. In Group 2 decrease in ODI at day 1 is not that significant as Group 1 and the progress in ODI of Group 2 not significant till 6 months. The comparison of Groups 1 and 2 is insignificant in baseline, but it is significant from day 1 onward [Table 3].

Table 3

Oswestry Disability Index at various intervals between two groups (n=20)

The comparison between SLR of different study groups reveals that there was significant improvement in SLR of Group 1 from day 1 onward. The comparison of Group 2 reveals there was insignificant improvement in SLR. The comparison of SLR of Groups 1 and 2 was insignificant at baseline; it becomes significant from day 1 onward [Table 4].

Table 4

Straight leg raising test at different time interval between two groups (n=20)

The quality of pain relief of Group 1 patients on day 1 is excellent in three patients which progressively increases in number over time and reaches to 16 at 6 months. Remaining four patients had good pain relief. In Group 2, none of the patients had excellent pain relief at any time, only one patient had good pain relief on day 1, satisfactory pain relief was in 3–5 patients and unsatisfactory pain relief was in 14–16 patients at different time intervals [Table 5].

Table 5

Quality of pain relief between two groups at different time intervals (n=20)

DISCUSSION

The management of chronic low back pain of discogenic in origin is challenging. Development of newer minimally invasive techniques including CRF, PRF, intradiscal steroid, ozone discectomy, and automated percutaneous lumber discectomy has modernized the management of discogenic low back pain.[910111213]

It is clearly evident from the study that significant better pain relief was observed in CRF group in term of VAS as compared to PRF at all intervals starting from day 1 to 6 months.

van Kleef et al. and Teixeira and Sluijter reported a similar observation which supports our findings.[910] However, Barendse et al. failed to observe pain relief following RF thermo coagulation of disc in patient suffering from discogenic low back pain.[8] The probable explanation for poor relief of pain following RF discectomy may be as the lesion was performed at lower temperature (70°C) and for lesser duration (90 s) as compared to 80°C and 210 s used in the present study. However, Erçelen et al. demonstrated that the increasing in the duration of RF from 180 to 360 s does not affect pain relief which contradicts observations made in the present study. However, in this study, there is significant (P < 0.05) pain relief using CRF for 210 s at 1 month as well as 6 months interval.[14] It appears that optimal increase in duration of RF lesion in the present study from 180 to 210 s results in better relief of pain. In addition to increase in duration of RF, the use of steroid may be responsible for better relief, however, further exploration into this matter is required.[12] Earlier study by Gautam et al. prospective randomized controlled study with 91 patients suffering from low back pain using PRF with ozone reported significant pain relief for 1 year.[11] The better results seen in this study could be attributed to the combination of ozone with PRF, which may be a synergistic effect.

In PRF group, there was no significant in fall in VAS score from baseline at any time from day 1 to 6 months. The patients receiving PRF reported unsatisfactory pain relief in 70% cases at day 1 and 80% cases at 2 weeks interval similar to observations made by Curatolo and Reiszworkers.[15]

There was significant fall in ODI from baseline value in Group 1 from day 1 to 6 months while in Group 2 improvements in ODI occurs up to 4 weeks after that no improvement occurs.

The comparison of ODI of two groups at various time intervals was significant (<0.05) from day 1 onward till 6 months. Bogduk and Mikeladze et al. observations was similar to our finding, which found CRF to be better than PRF based on decrease in ODI.[1617]

The change in SLR different study groups at different time intervals revealed patients in Group 1 had significant (<0.05) improvement from day 1 onward and an insignificant (>0.05) change in SLR observed in Group 2. From these observations, it is clearly evident that the pain relief and improvement in SLR was definitely better in Group 1 in comparison to Group 2. Teixeira and Sluijter support our observation.[10]

Preoperative spinal tenderness was found in four cases in Group 1 (20%) and two cases in Group 2 (5%). However, no cases were having postoperative spinal tenderness. No major complications such as discitis, bowel and bladder involvement, motor deficit, local site pain, and tenderness were seen.

Limitation of study

Our study has two main limitations. First, these results may vary from investigations performed on other ethnic groups due to variation in pain or drug sensitivity. Younger patients may be more tolerant to pain than older patients. Second, due to small number of patients result may vary.

CONCLUSION

From this study, we concluded that the RF discectomy using continuous temperature (CRF) along with steroid is best in view of immediate and long-term relief of pain and the improvement in ODI without any significant complications.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.