This study included 228 patients suffering from LDP with radiculopathy, recruited from the outpatient clinic of the Rheumatology and Rehabilitation Department at University Hospital; they were assessed for eligibility to participate in this study.
Those who met the inclusion criteria were selected. Conversely, those who did not meet inclusion criteria or met the exclusion criteria were excluded. Accordingly, 136 patients who met the inclusion criteria were divided into two groups:
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Group 1: Included 68 patients allocated for US-guided CESI, 3 patients went to spinal surgery, did not receive an intervention, 6 patients lost during follow-up, and finally data was analyzed for 59 patients.
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Group 2: Included 68 patients allocated FL-guided CESI, 2 patients went to spinal surgery, did not receive an intervention, 4 patients lost during follow-up, and finally data was analyzed for 62 patients.
Inclusion criteria
Patients with LDP with unilateral radiculopathy diagnosed by routine clinical examination and MRI, in whom conservative treatment (medical treatment and physiotherapy) failed for more than 6 weeks and refuse surgery or were unfit for surgery, are included.
Exclusion criteria
Vertebral fractures, direct trauma, spinal inflammatory disease, spinal infection, bleeding tendency, LBP with tumors, bilateral radiculopathy, cauda equina syndrome, spinal canal stenosis, post-laminectomy surgery, diabetic, and hypertensive patients are excluded.
Data collection
Baseline clinical data collected by interviewing the participants included demographic characteristics, disease duration, and history of associated medical conditions such as diabetes mellitus, hypertension, spinal trauma (direct or indirect, previous spinal operation), and history of other illnesses such as cancer, abdominal, or pelvic diseases.
Clinical examination
All patients were subjected to general systemic examination, the local musculoskeletal examination of all the joints with stress on lumbar spine examination, special tests as straight leg raising test, modified Schober test, and neurological examination to lower extremity to reveal the occurrence of the lumbar radiculopathy.
Laboratory assessment
Blood samples were taken and analyzed for measuring complete blood count, erythrocyte sedimentation rate, random blood glucose, and C-reactive protein.
Imaging
MRI is the imaging modality of choice, as it has the advantage of not using ionizing radiation and has good visualizing capacities especially of the soft tissue [12].
Study design
The study is a randomized controlled clinical trial.
Type of randomization
After baseline evaluation, the eligible patients (n = 136) were randomly allocated into treatment groups by means of block randomization (size of block = 4, with last block size = 2). The patients in each block were randomized by the use of a sealed envelope. Patients and doctors assessing outcomes were blind to the method of injection. After the inclusion of a patient, a physiatrist drew an envelope and opened it (Fig. 1).
Sample size
This is a controlled randomized clinical trial that proposes to assess the effectiveness of ultrasound-guided vs. fluoroscopy-guided caudal epidural steroid injection for the treatment of unilateral lower lumbar radicular pain. A previous study showed that a difference in the Oswestry Disability Index of 2.42 between the two procedures was clinically significant with a standard deviation of 4.74. To calculate the sample size with the level of significance = 5%, power = 80%, and type of test = two-sided, the following formula is used:
$$ n=\left[2{\mathrm{SD}}^2{\left({\mathrm{Z}}_{\alpha /2}+{\mathrm{Z}}_{\beta}\right)}^2\right]/{\mathrm{d}}^2 $$
where n = sample size required in each group, Zα/2 = 1.96 at type 1 error of 5%
Zβ = 0.842 at 80% power, and d = effect size, the difference between mean values. Based on the above formula, the sample size required per group is 60.2. Hence, the total sample size required is 120.
Therefore, a sample size of 120 patients, 60 in each arm, is sufficient to detect a clinically important difference between ultrasound-guided vs. fluoroscopy-guided caudal epidural steroid injection for the treatment of unilateral lower lumbar radicular pain using a two-tailed t test of the difference between means with 80% power and a 5% level of significance.
All the eligible patients were treated with either US-guided or FL-guided CESI and were administered a mixture of 20 cc (0.5% lidocaine 18.0 ml and 2 ml of triamcinolone acetonide 40 mg/1 ml) [13].
Intervention
Ultrasound-guided CESI (Group 1)
All the injection procedures were performed as an outpatient clinic setting. We used Acuson P300 (Siemens, Italy) with a linear transducer at 6 to 12 MHz as the US instrument, and another curved transducer at 2–5 MHz was available for obese patients.
First, the US probe was placed transversely at the midline to obtain the SH transverse image with the patient in the prone position (Supplementary Fig. 1).
Two sacral cornua appeared as hyper-echogenic structures with an inverted U shape, and then, SH was identified easily. At this level, the ultrasound transducer was rotated 90° to obtain the longitudinal view of SH.
Before CESI, the blood vessels were identified by power Doppler imaging. With the help of an assistant, an interventionalist, wearing sterile gloves, set up the equipment needed for the injection on a table covered with a sterile drape. The sacrococcygeal area was prepared using an iodine-based povidone solution and an alcohol solution.
A spinal needle (BD Spinal Needle Quinke Type Point, Becton Dickinson S A, Madrid, Spain) of 22-gauge and 3.5-inch was used. Under longitudinal view, the block needle was inserted using the “in-plane” technique. The block needle was visualized in real-time, piercing the SCL until “pop” or “give” feeling of SCL penetration, entering the SH, but could not be visualized beyond the apex of SH (Supplementary Fig. 2). Therefore, the advancement of needle tip beyond the apex of SH was limited to 5 mm to avoid the dural puncture because the distance between the apex of SH and dural sac termination can be as short as less than 6 mm [14].
After introducing the needle under longitudinal view, the US transducer position could be changed by placing it transversely across the SH and obtaining the image of the two sacral cornua with the needle out of plane. While we injected the material, the injectate will appear to the right, to the left, or to the center, and then, we modify the position of the needle to the affected side (Supplementary Fig. 3).
First, we checked the absence of the blood in the syringe before furthering the needle advancement and then performed an aspiration test to check for the presence of the blood and cerebrospinal fluid. If either method identified the blood, the needle was repositioned. If this technique identified CSF, the procedure was aborted and repeated after 2 weeks. After confirming the absence, first 1 to 2 mL of 1% lidocaine test dose was injected. The flow was observed using the color Doppler mode of US. We defined a positive spectrum as being observed the unidirectional flow of the solution with 1 dominant color through the epidural space beneath the SCL, without other directional flow of multiple colors. If other directional flow was detected, we reset the needle under US guidance and confirmed the needle position.
The following steps were initiated after monitoring of the onset of clinical manifestations such metallic taste, dizziness, tachycardia, lower extremity paresthesia, auditory changes, slurred speech, and motor ataxia for 1 to 2 min. Then, we injected the treatment drug (0.5% lidocaine 18.0 mL & 2 ml of triamcinolone acetonide 40 mg/1 ml) in the absence of such abnormal findings.
Fluoroscopy-guided CESI (Group 2)
All the injection procedures were performed in a specialized room with a FL device in the radiology department. We used a FL device GS 1004 with ALLURA XPER FD 20 system (Philips, Holland) with X-ray tube housing assembly, X-ray tube, beam-limiting device, and image receptor.
The patients were asked to lie on the FL table in a prone position. A pillow was placed under the hips to tilt the pelvis and bring the SH into greater prominence. Consequently, in the lateral view of FL, the SH was normally visualized as a translucent opening toward the base of the sacral canal (SC). Recognition of the coccyx immediately caudal also assisted with localization of the SH.
The sacrococcygeal area was prepared using an iodine-based povidone solution and an alcohol solution. The interventionist then localized the coccyx tip through palpation with a sterilized middle finger. Likewise, palpation of the coccyx and the sacral cornua by the clinician to help distinguish the insertion point of a needle.
A spinal needle (BD Spinal Needle Quinke Type Point, Becton Dickinson S A, Madrid, Spain) of 22-gauge and 3.5-inch was used.
The block needle trajectory was visualized and navigated accordingly into the SC. The needle should not be progressed beyond the foramen of S3 to avoid harming the sacral nerve roots and to limit the risk of subarachnoid or subdural placement.
We checked the absence of blood in the syringe before the needle advancement. The inhalation test was performed to check CSF leakage. We injected 1 mL of contrast media (Omnipaque300; GE Healthcare, Carrigtohill, Co., Cork, Ireland) before drug injection. By injecting contrast medium under FL, the placement of the needle tip within the sacral epidural space was verified, and placement either intravascular or intrathecal could be ruled out (Supplementary Fig. 4).
First, we injected 1 to 2 mL of 1%lidocaine as a test dose and monitored for any clinical symptoms such as metallic taste, dizziness, tachycardia, lower extremity paresthesia, auditory changes, slurred speech, and motor ataxia for 1 to 2 min. We injected 20 cc of the treatment drug (0.5% lidocaine 18.0 mL & 2 ml of triamcinolone acetonide 40 mg/1 ml) in the absence of such abnormal findings.
Post injection care for both groups:
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○ Rest for 1 day.
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○ The patient immediately returns to work 2 days after injection.
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○ Pain medication in the form of paracetamol only was allowed for the next 3 months if needed. The patients were instructed to stop analgesics 48 h before the visit to allow proper symptom assessment.
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○ Physical therapy or exercise was not allowed.
Outcome measures
Pain visual analog scale
The VAS-pain score is composed of a continuous horizontal line. This line is 100 mm in length. To measure the intensity of pain, the score is anchored by (0 score = no pain) at one end and (100 score = worst imaginable pain) at the other end. The patient places a mark in the VAS line at the point which represents the intensity of his pain [15].
Straight leg raising
The patient lies on a table in a supine position. With the one handset over the knee of the leg being examined, the examiner applies enough firm pressure to keep the knee in full extension. With the alternate hand cupped under the heel, the examiner raises the straight limb gradually. Sciatic nerve compression is indicated if the pain is agonized or worsened on raising the leg to a level more than 25° but lower than 75° [16].
Modified Schober test
While the patient is standing erect, add marks at 5 cm below and 10 cm above the lumbosacral junction (dimples of venus), and the distance between the two marks is measured. Then, the measurement is repeated with the patient in full forward flexion. In general, the measure should increase by at least 5 cm to 21 cm. An increase of less than 5 cm advocates decreased lumbar spinal mobility [17].
Secondary outcome measures
Oswestry Disability Index [18]
It is a self-administered questionnaire compromised of 10 sections; each section is scored on a 0–5 scale, 5 representing the greatest disability. It is composed of 10 short-term sectors. The index is calculated by dividing the summed score by the total possible score, after that it is multiplied by 100 and expressed as a percentage. Thus, for the not answered questions, the denominator is reduced by 5 for each.
The investigators who assessed the baseline data and outcome measures were blind to treatment procedures, and one investigator was responsible for intervention in the 2 groups.
Statistical analysis
The collected data were computerized and statistically analyzed using the SPSS program (Statistical Package for Social Science) version 18.0.
Qualitative data were represented as frequencies and relative percentages.
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➢ Chi-squared test: it was used to calculate difference between qualitative variables in different groups.
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➢ Quantitative data: it was expressed as mean ± SD (standard deviation).
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➢ Independent T test: it was used to calculate the difference between quantitative variables in 2 groups in normally distributed data.
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➢ Paired sample T test was used to calculate the difference between quantitative variables in the same group at different times.
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➢ Mann-Whitney test: it was used to calculate differences between qualitative variables in 2 groups in not normally distributed data.
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➢ Paired sample Wilcoxon test: it was used to calculate difference between quantitative variables in the same group at different times in not normally distributed data.
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➢ McNemar test: it was used to find the relation between qualitative variables in the same group pre- and post-treatment.
The significance level for all abovementioned statistical tests done and the threshold of significance is fixed at 5% level (p value): *p value of > 0.05 indicates non-significant results, *p value of < 0.05 indicates significant results, and *p value of < 0.01 indicates a highly significant result.
