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.
Neuropathic-like LBRLP (sciatica).
S-LANSS score ≥ 12 points.
LBRLP lasting more than 6 months.
Age between 18 and 70 years.
Acute injury or recent major trauma history.
Relevant painful conditions of the hip joint or pelvic/sacroiliac region.
Symptoms compatible with cauda equina syndrome (loss of bladder/bowel control, sexual dysfunction, paralysis of lower limbs, etc.).
Previous surgery on the spine, pelvis or hip.
Parallel
Percutaneous Electrical Nerve Stimulation
Procedure/SurgeryParticipants 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.
Placebo Transcutaneous Electrical Nerve Stimulation
Procedure/SurgeryAdhesive 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.
Transcutaneous Electrical Nerve Stimulation
Procedure/SurgeryParticipants 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.
Placebo Percutaneous Electrical Nerve Stimulation
Procedure/SurgeryA 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.
Real Dry Needling (without Percutaneous Electrical Nerve Stimulation)
Procedure/SurgeryParticipants 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.
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.
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.
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.
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).
Sociodemographic variables
Sociodemographic data will be collected using a standardized form in which participants will be required to provide their age, gender, occupation, height, weight, ethnicity, education level, comorbidities, history of sports activity, symptoms in other joints, duration of symptoms and medication use.
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Universidad Complutense de Madrid
Lead sponsor
Colegio de Fisioterapeutas de la Comunidad de Madrid
Collaborator
