Open inguinal hernia repair is one of the most commonly performed general surgical procedures worldwide. Effective perioperative analgesia plays a pivotal role in attenuating the surgical stress response, facilitating early ambulation, improving patient satisfaction, and reducing the incidence of chronic post-herniorrhaphy pain. Although general and neuraxial anaesthesia remain widely used, peripheral regional nerve blocks have gained increasing popularity because they provide excellent perioperative analgesia with minimal haemodynamic disturbance, reduced opioid consumption, and enhanced postoperative recovery. ¹⁻⁴ The sensory innervation of the inguinal region is derived primarily from the ilioinguinal (T12–L1) and iliohypogastric (T12–L1) nerves, with additional contributions from the genital branch of the genitofemoral nerve (L1–L2). Landmark-guided ilioinguinal–iliohypogastric (IIH) nerve block provides direct blockade of the nerves supplying the operative field, whereas the transversus abdominis plane (TAP) block achieves analgesia by depositing local anaesthetic within the fascial plane between the internal oblique and transversus abdominis muscles, thereby blocking the anterior rami of the lower thoracolumbar nerves. ⁵⁻¹³ Although ultrasound-guided regional anaesthesia has become increasingly popular because of improved accuracy and safety, landmark-guided techniques continue to be widely practiced in resource-limited healthcare settings owing to their simplicity, low cost, and universal availability. Previous studies comparing IIH and TAP blocks have predominantly evaluated ultrasound-guided techniques, while evidence comparing landmark-guided IIH and TAP blocks remains limited. ¹⁴⁻²³ Therefore, the present study was undertaken to compare the onset of sensory blockade, duration of anaesthesia, postoperative analgesic efficacy, and rescue analgesic requirements between landmark-guided IIH nerve block and landmark-guided TAP block in adult patients undergoing elective open inguinal hernia repair. We hypothesized that landmark-guided IIH nerve block would provide superior block characteristics and postoperative analgesia compared with landmark-guided TAP block. ¹⁸⁻²³

Study Design This prospective randomized comparative study was conducted in the Department of Anaesthesiology at a tertiary care teaching institute after obtaining approval from the Institutional Ethics Committee. Written informed consent was obtained from all participants before enrolment. Study Population A total of 110 adult patients aged 18–75 years with American Society of Anesthesiologists (ASA) physical status I–III undergoing elective unilateral open inguinal hernia repair were enrolled. Patients with refusal to participate, infection at the injection site, known hypersensitivity to local anaesthetics or dexamethasone, body mass index >35 kg/m², coagulopathy, pre-existing peripheral neuropathy, or severe cardiac, renal, or hepatic disease were excluded. Randomization and Group Allocation Patients were randomly allocated into two equal groups (n = 55 each) by block randomization method. Group IIH Patients received a landmark-guided ilioinguinal–iliohypogastric nerve block. The injection point was identified approximately 2 cm medial and 2 cm superior to the anterior superior iliac spine (ASIS). A 23-G, 50-mm spinal needle was advanced until a characteristic "pop" was appreciated while piercing the external oblique aponeurosis. Following negative aspiration, 18 mL of local anaesthetic solution was injected. The remaining 7 mL was infiltrated around the pubic tubercle to block overlapping sensory fibres from the genital branch of the genitofemoral nerve.⁵⁻⁸ ²⁴ Group TAP Patients received a landmark-guided posterior TAP block through the lumbar triangle of Petit. The triangle was identified using the iliac crest inferiorly, the external oblique muscle anteriorly, and the latissimus dorsi muscle posteriorly. After identifying the two characteristic fascial "pops," the local anaesthetic solution was deposited in the fascial plane between the internal oblique and transversus abdominis muscles following negative aspiration.⁹⁻¹⁷ Local Anaesthetic Solution Both groups received a total volume of 25 mL consisting of: • 12 mL of 0.5% bupivacaine • 11 mL of 2% lignocaine with adrenaline (1:200,000) • Dexamethasone 8 mg (2 mL) Outcome Measures The primary outcome measures were: • Onset of sensory blockade • Duration of anaesthesia The secondary outcome measures included: • Postoperative pain intensity assessed using the Visual Analogue Scale (VAS) at 2, 4, 6, 12, and 24 hours • Total postoperative rescue analgesic consumption (paracetamol and tramadol) • Intraoperative supplemental analgesic requirements • Block-related complications including local anaesthetic systemic toxicity (LAST), haematoma, visceral injury, peritoneal puncture, and femoral nerve weakness. ¹⁸⁻²³ Postoperative pain assessment was performed by an observer blinded to group allocation double blinded study. Statistical Analysis Data were analysed using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables are expressed as mean ± standard deviation (SD) and were compared using the independent Student's t-test. Categorical variables are presented as frequencies and percentages and were analysed using the Chi-square test or Fisher's exact test as appropriate. A P value <0.05 was considered statistically significant

A total of 110 Participants were randomized into 2 groups with 55 patients allocated to IIH/IH block group and 55 to TAP block group. All randomized patients completed the study and were included in the final analysis (Figure 1) Figure 1. CONSORT Flow Diagram Patients enrolled (n = 110) ↓ Randomized (n = 110) ↓ Allocated to IIH/IH block (n = 55) Received allocated intervention (n = 55) ↙ ↘ Allocated to TAP block (n = 55) Received allocated intervention (n = 55) ↓ Lost to follow-up (n = 0) Discontinued intervention (n = 0) ↙ ↘ Lost to follow-up (n = 0) Discontinued intervention (n = 0) ↓ Analysed (n = 55) ↙ ↘ Analysed (n = 55) CONSORT flow diagram showing enrolment, randomization, allocation, follow-up, and analysis. x A total of 110 patients completed the study protocol without dropouts. Baseline demographic parameters, ASA physical status distribution, and baseline hemodynamic parameters were comparable between Group IIH and Group TAP (p > 0.05). Table 1. Comparison of Baseline Demographic Characteristics Between Group IIH and Group TAP Variable Group IIH (n=55) Group TAP (n=55) pvalue Significance Age (years) 35.71 ± 8.23 37.51 ± 7.68 0.238 Not Significant Weight (kg) 63.25 ± 8.84 64.82 ± 9.24 0.364 Not Significant Gender M/F 47/8 43/12 0.458 Not Significant Table 2: Comparison of Onset and Duration of Anaesthesia Between the Two Groups Category Group IIH n=55 Mean ± SD Group TAP n=55 Mean ± SD p-value Significance Onset (minutes) 12.50 ± 2.14 15.39 ± 3.17 0.0000013 Significant Duration (minutes) 193.67 ± 24.07 172.22 ± 26.13 0.0000297 Significant Graph 1 - Comparison of Onset and Duration of Anaesthesia Between the Two Groups Primary Anesthetic Parameters: Sensory block onset was significantly faster in Group IIH (12.50 ± 2.14 min) compared to Group TAP (15.39 ± 3.17 min; p < 0.001). The mean duration of anesthesia was significantly extended in Group IIH (193.67 ± 24.07 min) relative to Group TAP (172.22 ± 26.13 min; p < 0.001). Table 3: Comparison of Postoperative VAS Pain Scores Between the Two Groups Time Point Group IIH Mean ± SD Group TAP Mean ± SD p-value Significance 2 hours 2.35 ± 0.75 2.76 ± 0.92 0.010397 Significant 4 hours 2.47 ± 0.81 3.25 ± 1.02 0.000023 Significant 6 hours 2.18 ± 0.75 3.36 ± 0.91 0.000001 Significant 12 hours 1.95 ± 0.78 2.62 ± 1.11 0.000379 Significant 24 hours 1.51 ± 0.63 1.93 ± 0.77 0.002341 Significant Postoperative Pain Trajectory (VAS Scores): Patients in Group IIH maintained significantly lower mean VAS scores at every postoperative time interval up to 24 hours (p < 0.05). Pain severity peaked around 6 hours postoperatively in both groups, but remained lower in Group IIH (2.18 ± 0.75 vs. 3.36 ± 0.91; p < 0.001). Analgesic Consumption and Safety: Postoperative rescue analgesic requirements were significantly lower in Group IIH. Total 24-hour IV paracetamol consumption was 1740 ± 331 mg in Group IIH versus 2180 ± 352 mg in Group TAP (p < 0.001). Total 24-hour IV tramadol consumption was 60 ± 18 mg in Group IIH compared to 89 ± 23 mg in Group TAP (p < 0.001). Supplemental intraoperative sedative and analgesic requirements (paracetamol, tramadol, midazolam, and pentazocine) were similarly lower in Group IIH (p < 0.001). No clinical signs of systemic local anesthetic toxicity, organ perforation, hematoma, or persistent motor block were observed in either group.

This prospective clinical evaluation demonstrates that landmark-guided IIH nerve block combined with pubic tubercle infiltration offers clinical superiority over landmark-guided TAP block for open inguinal herniorrhaphy. Group IIH achieved a significantly faster block onset (12.50 vs. 15.39 min), extended block duration (193.67 vs. 172.22 min), lower postoperative pain scores throughout 24 hours, and marked reduction in intra- and postoperative rescue analgesic consumption. The anatomical basis for these findings lies in the precise target of local anesthetic deposition. The surgical incision, sac traction, and mesh placement in open inguinal hernia repair stimulate neural pathways carried specifically by the ilioinguinal, iliohypogastric, and genitofemoral nerves. In the IIH block technique, local anesthetic is deposited directly adjacent to the nerves as they traverse between the internal oblique and transversus abdominis muscles near the ASIS. Supplementary pubic tubercle infiltration ensures blockade of overlapping sensory branches from the genital branch of the genitofemoral nerve and contralateral nerve crossings. In contrast, a TAP block via the lumbar triangle of Petit acts as a lateral abdominal wall fascia plane deposition. While effective for lower abdominal procedures involving anterior abdominal wall structures, local anesthetic spread within the fascia plane relies on volume distribution and may inconsistently reach the anterior sensory innervation of the groin and scrotum/labia (genitofemoral and ilioinguinal terminal distributions). This anatomical difference explains the slower onset and higher rescue opioid requirement observed in the TAP group. The inclusion of dexamethasone (8 mg) as a local anesthetic adjuvant in both groups contributed to prolonged analgesia. Corticosteroids act locally by suppressing inflammatory mediator release and inhibiting signal conduction in unmyelinated C-fibers. In low- and middle-income clinical settings where high-resolution ultrasound machinery may be unavailable or cost-prohibitive, landmark-guided regional techniques remain indispensable. Our results confirm that landmark-guided IIH block is a safe, highly effective, and reproducible regional technique for open groin surgery when performed with precise anatomical awareness. Limitations: First, ultrasound guidance was not utilized; incorporating real-time needle visualization could enhance block success rates and safety margins. Second, blinding of the administering anesthesiologist was not feasible due to differences in anatomical landmarks and puncture sites, though outcome assessors were fully blinded. Third, chronic post-surgical pain at 3 and 6 months postoperatively was not evaluated.

Landmark-guided ilioinguinal-iliohypogastric nerve block with pubic tubercle infiltration is superior to landmark-guided TAP block for open adult inguinal hernia repair. It provides faster onset of anesthesia, extended anesthetic duration, superior 24-hour pain control, and significant opioid-sparing benefits, making it an ideal primary regional anesthetic technique in resource-limited settings

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