Transforaminal epidural steroid injection via a preganglionic approach for lumbar spinal stenosis and lumbar discogenic pain with radiculopathy
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.63807
Source of Support: None, Conflict of Interest: None
Background: Epidural steroid injection (ESIs) is one of the treatment modalities for chronic low back pain (CLBP) with various degrees of success. Aim: We analyzed the efficacy of fluoroscopically guided transforaminal epidural steroid injections (TFESIs) via a preganglionic approach in patients with foraminal stenosis due to lumbar spinal stenosis and lumbar discogenic pain with radiculopathy. Materials and Methods: We analyzed the data of 40 patients (February 2008 and April 2009) with the diagnosis of CLBP and treated by fluoroscopically guided TFESIs via a preganglionic approach. Patients were followed-up at one month (short term), six months (midterm) and one year (long term) after injections. Follow-up data collection included the Visual Numeric Pain Scale (VNS) and North American Spine Society (NASS) patient satisfaction scores. Results: The mean age of the patients was 59.87 ± 15.06 years (range 30 - 89 years, 25 women). Average follow-up period was 9.22 ± 3.56 months. Statistically significant differences were observed between the pre-procedure and post-procedure VNSs (P < 0.01, Pearson Correlation Test). Improvements in VNS scores were correlated with improvements in the NASS scores. When the VNS scores were evaluated with respect to the age of patient, level numbers, gender, pre-procedure symptom duration and pre-procedure VNS, no significant differences were found (P < 0.05, linear regression test). At short term evaluation in post treatment (one month), 77.78 % of patients were found to have a successful outcome and 22.22 % were deemed failures. Overall patient satisfaction was 67.23 % in the midterm period. Additionally, 54.83 % of patients (N/n: 15/8) had a successful long-term outcome at a follow-up of one year. Conclusion: Our data suggest that fluoroscopically guided TFESIs via a preganglionic approach, in patients with foraminal stenosis due to lumbar spinal stenosis and lumbar discogenic pain with radiculopathy, has effective outcome and patients responding to injection have significantly lower post-injection pain scores.
Keywords: Chronic low back pain, effective outcome, lumbar spinal stenosis, preganglionic, radiculopathy, transforaminal epidural steroid injection
Common conservative medical treatments for low back pain (LBP) and radiculopathy include oral medications, exercise therapies, back posture training, lifestyle modifications, and epidural steroid injections (ESIs) ,, First advocated in 1952 by Robecchi and Capra, lumbar ESI has become a widely performed conservative therapeutic modality in patients with LBP.  Steroid injections may be delivered to the epidural space via a percutaneous caudal, interlaminar, or transforaminal approach, and the reported success rates ranged from 20 to 100%, with an average of 67%.  Compared with an interlaminar or caudal ESI, a transforaminal epidural steroid injection (TFESI) provides minimal risk of dural puncture, better delivery of medication to the site of radiculopathy, and increased distribution of the drung into the ventral epidural space. ,, TFESI can be given via a ganglionic approach or a preganglionic approach. Nserve root compression can be due to either subarticular or paracentral disk herniation, or central canal and/or lateral recess stenosis supra-adjacent to the intervertebral disk. There is no clear-cut consensus regarding the optimal injection site of performing TFESI.  Further, Lee et al. evaluated the effectiveness of TFESI via a preganglionic approach in patients with lumbo-sacral radiculopathy in whom the nerve-root compression was supra-adjacent to the intervertbral disk, , and reported effective treatment outcomes with rare post-procedure complications. We report the effectiveness of preganglionic TFESI approach in patients with LBP due to either the lumbosacral radiculopathy or stenosis of the lumbosacral vertebrae.
The TFESI procedure was performed by the same surgeon (S.K.) in all the 40 patients seen between February 2008 and April 2009. Patient medical charts were reviewed for the diagnosis, age at onset of symptoms, duration of symptoms prior to injection, findings on magnetic resonance imaging (MRI), injection levels, and subsequent surgical procedures. Informed consent was obtained and strict patient confidentiality was maintained.
Patients were all of Caucasian lineage and the age ranged from 30 to 89 years old (mean: 59.87 ± 14.29 years). Among them, 25 were female (62.5 %). Symptom duration ranged between 12 and 300 months (mean: 76.31 ± 65.74 months) and patient VNS scores ranged between 10 and 8 before preganglionic TFESI (mean: 9.00 ± 0.68). The selection criteria for inclusion were: 1. sustaining radicular pain for more than three months in duration; 2. faukyre ifconservative treatment; 3. definitive evidence of nerve root compression with either subarticular or paracentral disk herniation or central canal and/or lateral recess stenosis at the supraadjacent intervertebral disk based on physical examination and magnetic resonance imaging (MRI). Patients with previous spinal surgery and/or ESIs were excluded. Single level TFESI was given in 28 patients (n=13 at L5-S1, n=13 at L4-L5, n=2 at L3-L4), double-level TFESI in 11 (n=8 at L4-L5 and L5-S1, n=3 at L3-L4 and L4-L5) and triple-level TFESI in only 1 patient (at L3-L4, L4-L5, L5-S1). Descriptive statistics of the patients are shown in [Table 1]. All the patients received at least one fluoroscopically guided TFESI. Average follow-up period was 9.22 ± 3.56 months.
TFESIs were performed in the operation theatre equipped with a planar fluoroscope (Siemens TM , Mόnich, Germany) while the patients were prone. After sterile preparation, draping, and local anesthesia with one per cent lidocaine, a 9-cm long, 21-gauge spinal needle (Stimuquik TM [insulated peripheral nerve block needle]; Arrow International, PA, USA) was advanced towards the involved neural foramen under fluoroscopic guidance. The needle position was tracked via fluoroscopy, and 1 mL of contrast material (Omnipaque 300 TM [iohexol, 300 mg iodine per milliliter]; Amersham Health, Princeton, NJ) was injected to confirm epidural flow and to avoid intravascular, intradural, or soft-tissue infiltration. Upon confirmation of reaching the intended injection site, posteroanterior and oblique spot radiographs were obtained to document distribution of the contrast material. Lee et al.  described that for the preganglionic approach, the landmark for needle insertion was slightly lateral to the pars interarticularis on the oblique view, and at the neural foramen near the nerve root impingement site at the supra adjacent disk level on the posteroanterior view [Figure 1]a - d. Then 40 mg (1 mL) of methylprednisolone acetate suspension [Depomedrol TM Eczacibasi Ilac San., Luleburgaz, Kirklareli] was injected (~1 min), followed by 0.5 mL of bupivacaine HCl (Marcaine Spinal 0.5% Heavy TM ; AstraZeneca, Istanbul).
Follow-up and clinical evaluation
The Visual Numeric Pain Scale (VNS) and North American Spine Society (NASS) patient satisfaction questionnaire were used to evaluate the therapeutic efficacy of TFESIs [Table 2]. , Patients were evaluated before the procedure and at one week after the procedure. Those who responded favorably to TFESIs were then placed in a spine rehabilitation program for four to six weeks to maximize the functional gains. Those who did not respond or responded partially were offered either surgery or physical therapy.
VNS (0-10, 0 indicates no pain, 10 refers to the most severe pain) was recorded at the first clinical examination prior to TFESI. Patients were asked to the worst level of pain prior to, soon after, and one week after the injections. Patient outcomes were assessed one month after the TFESIs (short term) by an anesthesiologist (O.I.K) who was blinded to the pre-injection scores. The evaluator used VNS and NASS patient satisfaction questionnaire to assess the patient's own assessment with regard to the degree of improvement . Patients were then re-evaluated over the phone by a blinded independent observer (E.E) at six months and one year. A reduction in the VNS of more than 50% after the injection and with NASS score of 1 and 2 were classified as successful treatment, and a reduction in the VNS of less than 50% after the injection and with NASS score of 3 and 4 were classified as failed treatment. Patients who had subsequent surgery after injection were also deemed to have failed treatment.
Data were analyzed by SPSS version 13.0 software. The level of correlation between the pre-procedure and follow-up VNS and NASS scores were determined using Pearson Correlation test, with P < 0.05 with 95% confidence intervals considered statistically significant. The effects of the variables (age, gender, symptom duration, level number and pre-op VNS) to the results were analyzed using linear regression test, with P < 0.01 with 99% confidence intervals considered statistically significant.
None of the patients experienced any complications, and all the patients completed the follow-up visits. The mean pre-procedure, post-procedure, one month, six months and one year post-procedure VNSs (mean±SEM) were 9.00 ± 0.68, 1.55 ± 0.78, 2.00 ± 0.98, 2.95 ± 1.13, and 4.07 ± 1.62, respectively. Significant differences were observed between the pre-procedure and post-procedure VNSs (P > 0.01, Pearson Correlation Test). Subsequent analysis [Table 3] revealed that VNSs at one month and one year post-procedure were correlated with each other (P=0.004). Correlation in NASS between post-procedure and one year post-procedure (P=0.008), and correlation in NASS between one month and one year post-procedure (P=0.008) were also determined. Additionally, correlation in NASS between six months and one year post-procedure (P=0.003) were confirmed statistically. These was consistent and sustainable clinical improvement after TFESI over the 12 months period when NASS progressively decreased.
Improvements in VNSs were correlated with improvements in NASSs (P < 0.05, linear regression test). There was no significant difference in VNS between post-procedure and one month (P=0.067), six months (P=0.978) and one year post-procedure (P=0.711), respectively. There was no significant difference in VNS between one month and six months (P=0.478) or one year post-procedure (P=0.465). These comparisons indicated that the therapeutic benefits of TFESIs occured immediately by the injection, and the beneficial effects of TFESIs are sustainable over twelve months. However, there was a significant difference in VNS between six months post-procedure and one year post-procedure (P=0.001, [Table 4]), suggesting there could be loss of therapeutic benefit over six months after the TFESI procedures. Although the one year post-procedure VNSs still remained statistically similar to immediate post-op VNS.
Further, when the VNS and NASS were evaluated with respect to the age of the patients, level numbers, gender, pre-procedure symptom duration and pre-procedure VNS, no significant differences were found [Table 4]. A reduction by 50% or more in VNS and NASS scores at short-term (one month) follow-up was 77.8% (N/n: 40/31); at mid-term (six months) follow-up it was 67.2% (N/n: 40/27) and at long-term (twelve months) follow-up it was 54.8%.
The efficacy, both short and long-term, of fluoroscopic TFESI in patients with radicular symptoms from lumbar disk herniation and also in patients with radicular pain from lumbar spinal stenosis has been well documented. ., . However, ESI performed without fluoroscopic guidance is likely to miss the perceived target area 30 to 40 % of the time. , Nevertheless, failure to institute a specific treatment modality in a specific population of patients may dilute or inflate the treatment efficacy rates. Lutz et al. reported in an uncontrolled prospective study the efficacy (75.4%) of fluoroscopically guided TFESI in 69 select patients with radiologically confirmed lumbar radiculopathy due to herniated nucleus pulposus.  In some of the studies the efficacy of ESI was short lasting. ,, However, our study suggests that the efficacy of TFESI can be sustained and long lasting, 67% efficacy at 6 months and 55% efficacy at one year. Our results are similar to the observations in the study by Jeong et al.  In their study the efficacy of TFESI was sustained beyond six months in 60% of patients.
TFESIs via a preganglionic approach provides a shorter delivery route and also allows delivery of more medicine at the site of target. ,, Ganglionic approach has its limitations such as a relatively long injection route and limited space to accommodate the injectant. The preganglionic approach may be considered as an alternative to the ganglionic approach if the needle tip cannot be advanced adjacent to the neural foramen; or adequate amount of the drug cannot be injected into the epidural space through the neural foramen due to severe neural foraminal stenosis. Another advantage of the preganglionic approach is that the injectant distributes predominantly in the epidural space at the disk level. Our results were consistent with those of previous studies. , In our study some patients did not respond favorably to TFESIs, there may be several possible reasons. One of the reason could be that the patients might not have adhered strictly to the spine rehabilitation program.
In our study, symptom duration and other variables had no significant effect on the therapeutic outcome in all the follow-up evaluations. Pain perception can be measured by VNS and the quality of life by NASS. In our study there was good correlation between NASS and VNS scores. The validity and reliability of the VNS and NASS scales has been well documented and thus justify the use of these scales in assessing the TFESI efficacy. , Furthermore, these scales have been the standard tools in determining the outcomes in other ESI studies, and are clinically relevant and are sensitive for assessing clinical significance. ,
The limitations of this study are those inherent to any retrospective study and include selection bias and lack of a control group. This study focuses on the therapeutic efficacy of TFESI via a preganglionic approach in a selected group of patients. Additionally, the number of patients included for long-term evaluation was greatly limited by the fact that most patients are yet to complete the program. However, the midterm follow-up was sufficient to evaluate the therapeutic effect of TFESI.
We thank Dou Yu, MD, PhD (the Spinal Cord Injury and Neural Stem Cell Biology Laboratory, Brigham and Women's Hospital/Harvard Medical School, Boston, MA) for his suggestions in the preparation of this manuscript.
[Table 1], [Table 2], [Table 3], [Table 4]