This clinical study focuses on people who experience long-term low-back related leg pain (commonly called sciatica). This type of pain is often associated with nerve irritation or compression in the lower spine and can cause symptoms like shooting or burning pain, tingling, numbness, or weakness in the leg. Many patients continue to suffer from this problem for months or years, and available treatments (including painkillers, anti-inflammatory drugs, or even surgery) do not always provide lasting relief. Because of this, there is a strong need to explore safe, non-drug, non-surgical therapies. The purpose of this study is to test the immediate and short-term efficacy and safety of a single session of a treatment called Percutaneous Electrical Nerve Stimulation (PENS) when applied near the sciatic nerve, the large nerve that runs from the lower back through the buttock and down the leg. PENS uses very thin sterile needles inserted under ultrasound guidance next to the nerve. A gentle electrical current is then applied for about 30 minutes to stimulate the nerve in a controlled way. This may help calm down nerve sensitivity, reduce inflammation, and decrease pain. The investigators will compare PENS with three other options: Transcutaneous Electrical Nerve Stimulation (TENS): A commonly used therapy where mild electrical stimulation is applied through adhesive patches placed on the skin; Dry needling without electrical current: Thin needles are inserted under ultrasound guidance but no current is applied; and placebo treatment: A simulated version of the therapy with no active current, designed to look and feel similar so that participants do not know which treatment they are receiving. The study is designed as a randomized, controlled, double-blind trial, which means that participants are assigned to one of the four groups by chance (like flipping a coin), and neither the patients nor the therapists who collect the measurements will know which treatment has been given. This design ensures fairness and reliability of the results. The investigators will measure: Back and leg pain levels, using a simple 0-10 scale; Disability, meaning how much the pain limits daily activities, measured with a well-known questionnaire; Quality of life, both physical and mental health aspects; Nerve-related pain features, like burning or electric-like sensations; Flexibility and movement, through the Straight Leg Raise test; Sensitivity to pressure and nerve stiffness, using ultrasound elastography, which is a safe imaging technique; and patients' global impression of improvement and any side effects. Assessments will take place before and immediately after the treatment session and after 1 week, allowing the investigators to see both the immediate and short-term effects. Safety considerations: Previous research shows that PENS and similar techniques are generally very safe. The most common side effects are mild and short-lasting, including temporary soreness, heaviness in the leg, or a small bruise. Serious complications are extremely rare. To minimize risks, all procedures will be carried out by experienced physiotherapists, using real-time ultrasound to guide needle placement and ensure accuracy. Only sterile, single-use needles are employed. By comparing PENS, TENS, dry needling, and placebo, this study seeks to determine whether a single session of PENS provides superior benefits in reducing pain, improving function, and enhancing quality of life for patients with sciatica-type low back pain. If successful, this treatment could become a valuable alternative to drugs or surgery, offering patients a safe and effective therapy to better manage their condition and regain daily function.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
TRIPLE
Enrollment
88
Participants will receive real ultrasound-guided dry needle insertion (0.30 mm × 60 mm and 0.30 mm ×50 mm) to the perineural region adjacent to the sciatic nerve at both the subgluteal fold and the posterior thigh (junction between the middle and distal thirds). Electrical stimulation will be applied using the Endomed 484® electrotherapy unit (PRIM Physio, Madrid, Spain) in continuous biphasic mode at low frequency (2 Hz), 250 μs pulse width for 30 minutes. Intensity will be adjusted to elicit a visible, mild muscle contraction.
Adhesive electrodes will be placed near the intervention site (sciatic nerve between the subgluteal fold and the distal third of the thigh) but connected to a disabled channel to simulate placebo TENS.
Participants will receive real superficial electrical stimulation via adhesive electrodes connected to the Endomed 484® unit, configured for TENS (non-invasive). Parameters will include continuous biphasic current, 2 Hz, 250 μs, 30 min, producing a clear sensory perception and mild muscle contraction.
A sham ultrasound-guided dry needling procedure will be performed using Streitberger placebo needles, which contact the skin superficially without penetration. Cables for PENS will be placed on the skin but connected to a disabled channel to simulate placebo PENS.
Participants will receive real ultrasound-guided dry needling but without electrical stimulation. The needles will remain in place for 30 minutes, with the PENS channel disabled to act as placebo.
Pain intensity
Pain intensity will be assessed using the NPRS, a single 11-point numerical rating scale widely validated across different patient populations, where 0 represents no pain and 10 represents the worst possible pain. Data obtained through the NPRS are easy to document, intuitively interpretable and meet regulatory requirements for pain assessment and documentation. The NPRS has been shown to be reliable in assessing LBP intensity, also predicting the degree of disability in these patients. A change of 2 points on the NPRS has been considered to reflect the MCID in patients with LBP, indicating that any change equal to or greater than this value can be considered clinically relevant. However, the MCID has not yet been established in patients with LBRLP and neuropathic characteristics; therefore, a variation of 2 points will be used as a reference value, as in patients with LBP and those with chronic pain in general.
Time frame: Baseline, immediately after the intervention and 1 week post-intervention.
Disability
Disability will be assessed using the Oswestry Disability Index (ODI), an instrument designed to evaluate the degree of disability associated with acute, subacute and chronic LBP. The ODI consists of a total of 10 items, one assessing pain and the remaining nine assessing activities of daily living, each rated on a 6-point ordinal scale ranging from the best to the worst scenario (0-5 points). The scores for each item will be summed to obtain a total between 0 and 50 points, with the following categories: no disability (0-4 points), mild disability (5-14 points), moderate disability (15-24 points), severe disability (25-34 points) and complete disability (35-50 points). The ODI has been shown to be reliable and valid for assessing disability in patients with LBP and has been validated in Spanish. The MCID varies across studies; in this case, the smallest reported value (a change of 5 points) will be used as the reference for significant changes.
Time frame: Baseline and 1 week post-intervention.
Health-related quality of life
The SF-12 questionnaire, a shortened version of the SF-36, will be used for this assessment. The SF-12 consists of 12 items that evaluate eight different parameters: physical functioning, role limitations due to physical problems, bodily pain, general health, vitality, social functioning, role limitations due to emotional problems and mental health perception. The items are combined and transformed to provide both a physical and a mental health score, each ranging from 0 (worst) to 100 (best). The SF-12 has been shown to be valid and reliable in populations with chronic LBP. The MCID related to quality of life in patients with LBP has been established as improvements greater than 3.77 points in the mental component and 3.29 points in the physical component.
Time frame: Baseline and 1 week post-intervention.
Neuropathic component of pain
This variable will be measured using the S-LANSS pain scale, a self-administered instrument designed to identify patients with pain of neuropathic characteristics. It is a simple scale consisting of seven items with binary responses (yes or no), relating to the presence of symptoms (five items) or clinical signs (two items). The maximum possible score is 24 points, with scores equal to or greater than 12 considered clear indicators of the presence of a neuropathic pain component. The S-LANSS scale has been shown to be reliable for diagnosing pain with neuropathic characteristics and has been validated in Spanish.
Time frame: Baseline and 1 week post-intervention.
Pressure pain threshold
To assess PPT a pressure algometer will be used, determining the minimum amount of pressure required for the patient to feel pain. PPT will be measured at three different points on each side: tibial nerve (posterior aspect of the knee), peroneal nerve (at the level of the fibular head), and the sciatic nerve trunk (gluteal region), repeating each measurement three times and averaging the results. According to the classification by Shrout and Fleiss, algometry measurement of PPT at the tibial nerve has shown good intra-rater reliability (ICC = 0.64) and acceptable inter-rater reliability (ICC = 0.56) in asymptomatic individuals. For the peroneal nerve, intra-rater reliability is excellent (ICC = 0.84) and inter-rater reliability is good (ICC = 0.70). For the sciatic nerve, intra-rater reliability is excellent (ICC = 0.90) and inter-rater reliability is good (ICC = 0.75).
Time frame: Baseline, immediately after the intervention and 1 week post-intervention.
SLR test outcome
The test will be performed with the participant in a supine position, passively raising the lower limb by flexing the hip while keeping the knee extended. A recent meta-analysis has highlighted ongoing concerns regarding its reliability and diagnostic accuracy, suggesting that incorporating structural differentiation movements may improve its performance. Based on previous research of limited quality, the test has been reported to have high sensitivity and low specificity, although results vary between studies. Likelihood ratios also differ widely across investigations, with LR+ ranging from 1.07 to 4.73 and LR- from 0.27 to 0.96. It has been determined that diagnosing radicular pain and radiculopathy in patients with LBRLP, when based solely on history and physical examination, has only slight inter-rater reliability (Kappa 0.35). In terms of interpretation, the SLR test is considered positive when it elicits familiar symptoms that relieve upon returning to the starting position.
Time frame: Baseline, immediately after the intervention and 1 week post-intervention.
Pain Descriptors: Familiar Symptomatology and Paresthesias
Categorical scales will be used to record the extent to which the SLR test reproduces symptomatology recognized by the patient as familiar (not familiar, slightly familiar, considerably familiar or exact reproduction of symptoms) and the severity of any dysesthesias or paresthesias experienced (none, mild-moderate or severe). This questionnaire has demonstrated moderate to excellent inter-rater reliability (ICC = 0.78-0.96).
Time frame: Baseline, immediately after the intervention and 1 week post-intervention.
Range of motion in hip flexion
Data on the hip flexion ROM achieved during the SLR test will be collected. The participant will be in a supine position and the hip flexion movement will be recorded using anatomical reference points and assessed using Kinovea, a motion-analysis software. A previous study using this method reported excellent intra- and inter-rater reliability, with ICCs ranging from 0.985 to 0.999 and a minimal detectable change of 1.3-4° of hip flexion in patients with LBP. In contrast, a previous meta-analysis concluded that inter-rater reliability for ROM measurement during the SLR test is poor, with variations ranging from 13° to 20º.
Time frame: Baseline, immediately after the intervention and 1 week post-intervention.
Sciatic nerve stiffness
An experienced ultrasound researcher will perform shear wave elastography (SWE) to assess sciatic nerve stiffness using a Logiq P9 XDclear™ system with convex (1-6 MHz) and linear (6-15 MHz) probes. Exams will be bilateral in the subgluteal fossa, with participants prone, ankle neutral, and knee extended. The nerve will be identified axially for thickness, width and area, then imaged longitudinally for SWE. Stable transducer positioning will allow simultaneous B-mode and SWE display. Stiffness will be expressed in kPa, taking at least three measurements that will be averaged for analysis. All images will be acquired by the same investigator. This method shows good reliability (ICC = 0.869), and higher stiffness (≈11.3%) has been observed in affected legs of patients with LBRLP compared to their unaffected side and to healthy controls.
Time frame: Baseline, immediately after the intervention and 1 week post-intervention.
Global perceived improvement
Global perceived improvement will be measured using a 7-point Likert scale ranging from "much worse" to "much better." Clinical improvement will be considered in participants who report feeling "moderately better" or "much better".
Time frame: Immediately after the intervention and 1 week post-intervention.
Adverse events
Adverse events will be defined as any problem related to the intervention that causes symptoms lasting at least two days or requiring specific treatment.
Time frame: Through study completion, an average of 2 years.
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