|Year : 2021 | Volume
| Issue : 2 | Page : 146-149
Comparative study of positive predictive value of diagnostic single versus dual median branch block for radiofrequency neurotomy in lumbar facet joint syndrome
Baibhav Bhandari1, Subrata Ray2, Subrata Goswami1
1 Department of Pain Management, ESI Institute of Pain Management, Kolkata, West Bengal, India
2 Department of Anesthesiology, KPC Medical College and Hospital, Kolkata, West Bengal, India
|Date of Submission||19-Dec-2020|
|Date of Decision||14-May-2021|
|Date of Acceptance||17-May-2021|
|Date of Web Publication||31-Aug-2021|
Dr. Subrata Goswami
Department of Pain Management, ESI Institute of Pain Management, Kolkata, West Bengal
Source of Support: None, Conflict of Interest: None
Background: Almost 60%–85% of people suffer from low back pain once in their lifetime. Due to a large number of pain generators, many a times lower back pain pose as enigma. Many clinical trials have shown validity of median branch block (MBB) in the management of chronic low back pain arising from facet joint pathology. Single blocks result in 27%–63% false positives, whereas double controlled blocks significantly decrease the false positives and increases the sensitivity to 54% and specificity to 88%. The aim of our study was to determine positive predictive value of diagnostic single and dual MBB for radiofrequency (RF) neurotomy in patients with facet joint arthropathy in Indian population. Subjects and Methods: Thirty patients allocated into two groups (n = 15), Group S - Single diagnostic MBB and Group D - Dual diagnostic MBB. Numerical Rating Score (NRS) and Roland Morris Disability Questionnaire (RMDQ) were recorded in all patients in both the groups at multiple times. Pre and postprocedure NRS and RMDQ score in both the groups were statistically compared. Results: NRS in Group D was lower as compared to Group S 1 month after neurotomy (P = 0.034). RMDQ in Group D 1 month after RF neurotomy was lower as compared to Group S (P = 0.045). The positive predictive value in Group S with single MBB is 66.6%, whereas the positive predictive value in Group D with dual MBB is 86.6% at the end of 1 month post-RF ablation. Conclusions: Single MBB injection for diagnosis of facet joint syndrome yields many false positives results and the positive predictive value for the same is lower as compared to Dual MBB.
Keywords: Facet joint, low back pain, nerve blocks, positive predictive value
|How to cite this article:|
Bhandari B, Ray S, Goswami S. Comparative study of positive predictive value of diagnostic single versus dual median branch block for radiofrequency neurotomy in lumbar facet joint syndrome. Indian J Pain 2021;35:146-9
|How to cite this URL:|
Bhandari B, Ray S, Goswami S. Comparative study of positive predictive value of diagnostic single versus dual median branch block for radiofrequency neurotomy in lumbar facet joint syndrome. Indian J Pain [serial online] 2021 [cited 2021 Nov 30];35:146-9. Available from: https://www.indianjpain.org/text.asp?2021/35/2/146/325201
| Introduction|| |
The lifetime prevalence of low back pain (LBP) is estimated at 60%–85%, while the annual prevalence in the general population ranges from 15% to 45%. However, it is often difficult to reach a definitive diagnosis and provide appropriate treatment. Different etiologies of LBP were ascertained in the past decades using different diagnostic blocks. The prevalence of facet joint induced pain ranges from15% to 40% in different age groups. In some clinical trials, median branch block (MBB) has shown great validity in the control of chronic or even acute LBP from facet joint dysfunction.
Facet joint pain is diagnosed by blocking median nerve at the level of the joint involved and one level above it. A positive test increases the likelihood of facet joint as pain generator, whereas a negative test excludes the joint as pain generator. Single blocks result in 27%–63% percent false positives, whereas double controlled blocks significantly decrease the false positives and increase the sensitivity to 54% and specificity to 88%. As the role of diagnostic blocks has not been accepted beyond question, the study to validate positive predictive value of these blocks are till relevant. We under took this study to determine the correlation between MBB responses and radiofrequency (RF) neurotomy or ablation outcomes among Indian population.
Aims and objectives
- Primary objective was to assess the outcome of RF ablation after single MBB and dual MBB
- Secondary objective was to determine positive predictive value of diagnostic single MBB and dual MBB for RF ablation in patients with low back pain
| Subjects and Methods|| |
This was a prospective randomized open label comparative study, conducted at a Government State Hospital at Kolkata, from March 2017 to August 2017. After obtaining approval of the hospital ethics committee (Clinical Trial Registry No CTRI/2017/05/008683), thirty patients diagnosed clinically as having unilateral single facet joint arthropathy were enrolled in this study [Table 1]. As there was no such prior study in Indian population, we considered this as pilot study, and sample size and power of study were not calculated.
Inclusion criteria were age between 18 and 60, chronic LBP with or without proximal nonradicular extremity pain of more than 3 months duration, pain unresponsive to conservative treatment including medical management, physical therapy, and previous interventions. Exclusion criteria were more than one facet joint or bilateral facet joint involvement, pain for less than 3 months, neurological deficits, pregnancy and lactating mother, prior low back surgery, concurrent cervical or thoracic pain, or pain in these regions lasting longer than 2 weeks during the previous 6 months, primary or metastatic spine tumor or spinal cord injury, allergy to medications used in procedure, and blood coagulation disorder.
After obtaining written informed consent from the patients, they were randomized into two groups according to computer-generated randomization chart. Group S (n - 15) – single diagnostic MBB with 1% lignocaine and Group D (n - 15) – dual diagnostic MBB with 1% lignocaine and 0.25% bupivacaine.
Patients in this group were given diagnostic MBB using 1%, 0.3 ml lidocaine. After the block, the patients were examined after half an hour and asked to perform movements which were earlier perceived to be painful. Those who had 80% reduction of pain were diagnosed as true positive, and pain relief should last for at least 2 h. RF ablation was performed in all the patients having positive response 2–3 weeks after MBB.
Patients in this group were given diagnostic MBB using 1%, 0.3 ml lidocaine. Patients who had at least 80% pain relief for more than 2 h were subjected to second block using 0.25%, 0.3 ml bupivacaine after an interval of 2 weeks from the first block. Half an hour after the block, the patients were examined as before. A true positive response was defined as at least an 80% reduction of pain and pain relief should last for at least 3 h or longer than the duration of relief with lidocaine. RF ablation was performed in all the patients having positive response 2–3 days following MBB.
PROCEDURE: RF ablation was performed at preselected levels with insulated 18G RF probe with 10 mm exposed tip, which was placed on target nerves and two lesions were created at 80°C, each one of 60 s duration, total 120 s.
Percentage pain relief was calculated by the formula ([pretreatment pain intensity-post treatment pain intensity ÷ pretreatment pain intensity] ×100). Patients in both the groups were assessed using Numerical Rating Score (NRS) on a scale of 0–10 and Roland Morris Disability Questionnaire (RMDQ) on a scale of 0–24 on admission, after every MBB, and 1 month after the RF ablation and recorded.Patients, who had ≥3 points decrease in NRS score compared to preprocedure NRS score at 1 month postprocedure evaluation, were considered to be true positive for facet joint syndrome, and <3 point reduction of NRS score was taken as false positive. Preprocedure and post procedure NRS and RMDQ score in both the groups were statistically compared using Wilcoxin Signed Rank test in IBM SPSS software (IBM SPSS South Asia Pvt Ltd, Bangalore, India).
| Results|| |
[Table 2] shows demographic data in both the groups. Both the groups were comparable with respect to demographic characteristics of age, height, and weight [Table 2].
There was a significant difference between NRS preprocedure at the time of enrollment and postprocedure 1 month after RF neurotomy [Table 3] in both the groups, P = 0.001.
|Table 3: Numerical rating score and Roland Morris Disability Questionnaire score of two groups|
Click here to view
There was a significant difference between RMDQ preprocedure at the time of enrollment and postprocedure 1 month after RF neurotomy in both the groups, P = 0.001 [Table 3]. NRS was compared 1 month after neurotomy in both the groups [Chart 1] and it was found that NRS in Group D (3.20 ± 1.20) was lower as compared to Group S (4.26 ± 1.53), which was statistically significant (P = 0.034). When RMDQ was compared 1 month after RF neurotomy in both the groups, it was found [Chart 1] that RMDQ in Group D (10.06 ± 2.65) was lower as compared to Group S (11.06 ± 2.27), which was also statistically significant (P = 0.045).
The positive predictive value, in Group S with single MBB, is 66.6%, whereas the positive predictive value in Group D with dual MBB is 86.6% at the end of 1 month post-RF ablation [Table 4].
| Discussion|| |
Although facet arthropathy is more or less a clinical diagnosis, it is reinforced by diagnostic blocks. Several studies have reported false positive results with single diagnostic nerve blocks such as MBB. Some authors even found outcome of nerve blocks comparable to noninterventional management and do not recommend nerve blocks. On the contrary, many other studies reported better outcome with nerve blocks. In a large study which included 1420 patients from seven different studies, Datta et al. evaluated the prevalence as well as false-positive rate of single diagnostic block and reached to the conclusion that there was an overall prevalence of 31% (95% confidence interval [CI]: 28%–33%) and a false-positive rate of 30% (95% CI: 27%–33%). In another large study, the prevalence was reported to be 27% (95% CI: 22%–33%) and a false-positive rate was 45% (95% CI: 36%–53%). They have also described the significance of using criteria of 80% pain relief to define positive diagnostic test. Another large study showed prevalence of 31% (95% CI: 27%–36%) with a false-positive rate of 27% (95% CI: 22%–32%) with a single block.
Manchikanti et al. studied 110 patients and followed them for 2 years and concluded that double blocks with 80% relief are superior to a single block with 80% relief, single block with 50% relief, or double blocks with ≥50% relief. In our study also, we have set 80% pain relief as cutoff line and ≥3 point reduction of NRS score 1 month after RF ablation as true positive. On the other hand in a multicenter prospective correlational study of 61 consecutive patients, Cohen et al. did not find significant differences in RF neurotomy outcomes based on any MBB pain relief cutoff over 50%.
Derby et al. in their retrospective study concluded that the double MBB protocol better correlated with favorable median branch neurotomy outcomes compared to a single MBB protocol. They also concluded that no patient in the double MBB group, reporting <70% pain relief following diagnostic block, had satisfactory pain relief following neurotomy.
Both studies of Manchikanti L. et al. and Pampati S. et al. analyzed data from long-term follow-up evaluation of repeat MBB to confirm the previous MBB and indirectly supported the ideal cutoff value of pain relief as 80%. They reported that confirmation of prior MBB was best using a double-block protocol with an 80% cutoff value compared to a single block with 80% pain relief.,
No complications were observed in any of the patients in our study. When performed correctly, lumbar medial branch neurotomy is a remarkably safe procedure. Side effects are uncommon, of limited duration, and minor in nature. They include soreness from the electrode track and temporary pain from the sites where lesions are produced. Major complications have been encountered only when operators have failed to follow guidelines for the safe and accurate conduct of the procedure. There are some limitations in our study; power of the study and adequate sample size were not calculated as it was a pilot study in Indian population.
| Conclusions|| |
Single MBB injection for diagnosis of facet joint syndrome yields many false-positive results and the positive predictive value for the same is lower as compared to dual MBB for diagnosis of facet joint syndrome. We propose more studies to be under taken among Indian populations.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]