SGEM#483: Electricity – TENS Units for Treating Back Pain

Reference: Otterness et al. The Use of TENS for the Treatment of Back Pain in the Emergency Department: A Randomized Controlled Trial. AEM Aug 2025 Date: August 22, 2025 Guest Skeptic: Dr. Lauren Westafer is an Assistant Professor in the Department of Emergency Medicine at the University of Massachusetts Medical School, Baystate. She is the co-founder of FOAMcast and a researcher in pulmonary embolism and implementation science.  Dr. Westafer serves as the research methodology editor for Annals of Emergency Medicine. Case: A 44-year-old man presents to the emergency department (ED) with low back pain after bending to pick up his child. He has pain in his left lower back that is worse when he moves. He has no fever, chills, weakness, or numbness. He has well-controlled hypertension and no history of recent antibiotic use or drug use. The patient has no midline tenderness, is without neurological deficit, and has no red flag features on history and physical exam. He took 500 mg of acetaminophen a few times without significant relief. Background: Back pain is one of the most common reasons patients seek ED care, with an estimated 2.5 million ED visits for back pain each year. After dangerous diagnoses such as spinal epidural abscess, cord compression, and ruptured abdominal aortic aneurysm have been excluded, the next challenge for emergency clinicians is analgesia to improve the patient’s pain and mobility. Unfortunately, there are numerous causes of musculoskeletal low back pain, rendering a single treatment course inconsistently effective for all-comers. Many pharmacological and non-pharmacological therapies have been tried with limited efficacy.  Acetaminophen (Williams et al Lancet 2014) Muscle relaxants (Friedman et al JAMA 2015) NSAIDs (Machado et al Ann Rheum Dis 2017) Steroids (Balakrishnamoorthy et al Emerg Med J 2014) Benzodiazepines (Friedman et al Ann Emerg Med 2017) Cognitive Behavioral Therapy and mindfulness (Cherkin et al JAMA 2016) Chiropractic (Paige et al JAMA 2017) Physical therapy (Paolucci et al J Pain Research 2018) Acupuncture (Colquhoun and Novella Anesthesia and Analgesia 2013) One treatment that can be very effective but comes with very real potential harms is opioids. The American College of Emergency Physicians (ACEP) has addressed the issue of opioid use in patients being discharged home after an acute episode of pain. They give a Level C Recommendation saying: Do not routinely prescribe, or knowingly cause to be co-prescribed, a simultaneous course of opioids and benzodiazepines (as well as other muscle relaxants/sedative-hypnotics) for treatment of an acute episode of pain in patients discharged from the emergency department (Consensus recommendation).  Transcutaneous electrical nerve stimulation (TENS) is a non-pharmacological modality that administers low-intensity electrical stimulation to inhibit nociceptive pain signals. The efficacy of TENS devices in acute low back pain is uncertain. Clinical Question: Is transcutaneous electrical nerve stimulation (TENS) more effective at relieving back pain than sham TENS? Reference: Otterness et al. The Use of TENS for the Treatment of Back Pain in the Emergency Department: A Randomized Controlled Trial. AEM Aug 2025 Population: Adult ED patients (≥18 yr) with thoracic or lumbar back pain of at least moderate severity when research assistants were present (Mon–Fri, 8a–8p). Exclusions: Patients with suspected spinal cord injury or infectious etiology, fractures, hemodynamic instability, allergy to standard analgesics, pacemakers, and those with skin conditions precluding TENS application were excluded. Intervention: Two cutaneous TENS adhesive pads above and below the point of maximal tenderness with TENS unit set at a point just below the pain threshold and gradually increased for up to 30 minutes. Comparison: Sham TENS pads applied but no electrical current. Patients were told they might or might not feel pulses. Outcome: Primary Outcome: Absolute reduction in pain (0–10 NRS) from baseline to 30  Secondary Outcomes: Administration of rescue medications, change in pain severity, patient satisfaction with assigned treatment, and whether patients would recommend the same treatment Trial: Single-center randomized controlled trial Dr. Kara Otterness This is an SGEMHOP, and we are pleased to have the lead author on the episode, Dr. Kara Otterness. She is originally from Illinois and graduated from Drexel University College of Medicine and completed her Emergency Medicine residency training at NYU/Bellevue. She joined the Stony Brook EM faculty in 2015. She is passionate about teaching, medical education and currently serves as one of the assistant program directors at Stony Brook.  Dr. Otterness has been a guest skeptic on SGEM#96.  Authors’ Conclusions: “TENS was more effective than sham TENS at reducing pain severity in adult ED patients with back pain.” Quality Checklist for Randomized Clinical Trials: The study population included or focused on those in the emergency department. Yes The patients were adequately randomized. Yes The randomization process was concealed. Yes The patients were analyzed in the groups to which they were randomized. Yes The study patients were recruited consecutively (i.e. no selection bias). No  The patients in both groups were similar with respect to prognostic factors. Yes  All participants (patients, clinicians, outcome assessors) were unaware of group allocation. No All groups were treated equally except for the intervention. Yes Follow-up was complete (i.e. at least 80% for both groups). Yes All patient-important outcomes were considered. Yes The treatment effect was large enough and precise enough to be clinically significant. Unsure Financial conflicts of interest. None Results: The total cohort consisted of 80 patients. The mean age was 46 years. It was evenly split between female and male patients. The vast majority had lumbar pain (86%), 40% traumatic and 33% recurrent pain. Roughly half of patients had tried self-care with over-the-counter medications, and 31% had used heat.   Key Results: TENS produced a greater reduction in 30-minute pain than sham and reduced the need for rescue meds, with higher satisfaction and similar functional measures. Primary Outcome: The mean difference in change in pain scores was 1.2 (95% CI 0.5-1.9) p=0.002 Secondary Outcomes: Overall, secondary outcomes favoured the intervention. Rescue medications were administered to a higher proportion of patients in the sham TENS group (73% vs 45%), and more patients rated the degree of pain relief as better or much better in the TENS group (55% vs 26%). More patients in the intervention group were satisfied with their treatment (78% vs 50%). Listen to the SGEM podcast to hear Kara respond to our five nerdy points.  Convenience Sample: This trial used a convenience sample of patients enrolled only when research assistants were available (weekday business hours). Restricting recruitment in this way creates a risk of selection bias and limits generalizability because the study population may differ systematically from all ED back-pain patients. For example, patients who present to the ED at night and on weekends may have different injury mechanisms, comorbidities, pain severity or expectations. Compromised Masking: Although the trial was designed to be patient and assessor-mask, most patients correctly guessed their group allocation (95% TENS and 83% sham). When masking is not maintained, especially for subjective outcomes like pain scores, patients’ expectations can influence reported outcomes (placebo/nocebo effects). This can inflate the apparent benefit in the intervention arm, a form of differential measurement bias. True allocation concealment and maintaining blinding integrity are central to avoiding biased estimates of effect in RCTs. However, it is difficult to think about how such an intervention could be delivered without patients guessing correctly. Clinical vs Statistical Significance: The trial’s primary outcome did reach statistical significance (mean pain reduction difference 1.2 points, 95% CI 0.5–1.9) p =0.002. However, the effect size was close to or below many published minimum clinically important difference (MCID) thresholds for acute pain of around 1.5 on a 0–10 scale. Overemphasis on statistical significance without weighing clinical relevance can lead to the adoption of interventions that improve scores in a way that is detectable to researchers but not perceptible or valuable to patients. Small Sample Size: Patient recruitment in the ED is notoriously difficult due to difficulties staffing research staff at all hours of the day and during acute conditions. The authors recruited an adequate number of patients (n=80) for their power analysis; however, this resulted in large confidence intervals and ranges. Small studies are more vulnerable to random error and chance imbalances in prognostic factors, even with randomization. This increases the likelihood that the observed effect could be an overestimate (small-study effect) and reduces confidence in the precision of the result. Single-Centred: Because the trial was conducted in a single ED, the findings may not translate directly to other practice environments. Results from a tertiary academic centre (often with more resources, specialist staff, and research infrastructure) may not reflect community EDs, rural settings, or different health systems. Patient demographics, case mix, staff expertise, and even equipment quality can influence both the feasibility of the intervention and its observed effect. Without replication in multiple, diverse sites,