The Effect of Transcutaneous Electrical Nerve Stimulation (TENS) on Postoperative Pain and Sleep After Inguinal Hernia Surgery: A Randomized Controlled Trial

This randomized controlled clinical trial investigates the effects of Transcutaneous Electrical Nerve Stimulation (TENS) on postoperative pain and sleep quality in patients undergoing inguinal hernia repair. Inguinal hernia is one of the most common surgical conditions worldwide, with increasing prevalence in recent years. Although tension-free herniorrhaphy has become the gold standard technique due to its low recurrence rate, rapid recovery, and cost-effectiveness, chronic postoperative inguinal pain (CPIP) remains a significant complication that negatively affects quality of life. CPIP is typically defined as new or altered groin pain persisting for more than three months after surgery, and its pathophysiology is not fully understood. Nerve injury or entrapment of the ilioinguinal, iliohypogastric, or genitofemoral nerves is considered a major contributor.

Postoperative pain management often relies on opioid analgesics, which carry risks of dependence, respiratory depression, and prolonged hospitalization. Therefore, non-pharmacological alternatives are of growing interest. TENS is a minimally invasive neuromodulation technique that modulates pain signals, most commonly explained by the Gate Control Theory, in which stimulation of large myelinated fibers inhibits transmission of pain through smaller nociceptive fibers. Previous studies have suggested potential benefits of TENS in CPIP, but evidence remains limited and inconsistent. Moreover, chronic pain is frequently associated with sleep disturbances, further impairing physical and psychological well-being. TENS may therefore improve both pain and sleep quality in this patient population.

The study will be conducted between October 2025 and October 2026 at the General Surgery Department of SBÜ Adana City Training and Research Hospital. Eligible participants will be adults (≥18 years) undergoing inguinal hernia surgery who are conscious, cooperative, and without contraindications to TENS. Exclusion criteria include cardiac pacemakers or implanted electronic devices, uncontrolled epilepsy or neurological disorders, chronic opioid use prior to surgery, severe psychiatric or cognitive impairment, dermatological conditions at electrode sites, requirement for additional analgesic/regional block during follow-up, or concurrent participation in another clinical trial.

Sample size was determined by power analysis, requiring 40 patients in the intervention group and 40 in the control group (total n=80) to detect a significant difference with α=0.05 and power=0.80. Data collection will include a Personal Information Form, the Visual Analog Scale (VAS) for pain intensity, and the Richards-Campbell Sleep Questionnaire (RCSQ) for sleep quality. VAS is a validated, simple, and widely used tool for assessing subjective pain intensity, while the RCSQ evaluates multiple dimensions of sleep quality using visual analog scales.

The primary hypothesis is that TENS will reduce postoperative pain and improve sleep quality compared with standard care. The null hypothesis states that TENS has no effect on these outcomes. Ethical approval has been obtained, and all procedures will be performed under physician supervision to ensure patient safety.