Ultrasound out of plane approach for pulsed radiofrequency treatment of post herniorrhaphy pain: Synchronizing treatment and imaging modality.

Sir,

Chronic postherniorrhaphy pain is a debilitating complication resulting from surgical trauma or ilioinguinal-iliohypogastric (ILIH) nerve entrapment from sutures, autoclips or mesh.[123] A 55-year-old male presented with severe continuous right sided groin pain radiating to superiomedial thigh that developed immediately following right laparoscopic total extra-peritoneal herniorrhaphy 2 years ago followed by mesh removal for the same with no pain relief. The pain intensity was 8/10 with a past 4 weeks maximum and average of 10/10 and 8/10 respectively on 11 point numerical rating scale (NRS). The pain was electric shock-like, burning and numbness in quality with the pain detect tool score of 20. The aggravating factors were standing, walking, touching, pressing and wearing clothes while there were no relieving factors. It interfered with every inclusive of social, occupational and emotional aspect of patient's life. On examination, allodynia and Tinel's sign was positive. The pain was poorly controlled on tablet pregabalin 450 mg, duloxetine 40 mg, acetaminophen 3 g., tramadol 300 mg daily along with fentanyl 50 μg/h transdermal patch. The patient underwent ultrasound (USG) guided ILIH diagnostic block with 3 ml of 0.5% resulting in 80% pain relief lasting for 120 min. A linear transducer (5-12 MHz) with out of plane approach was employed for accurate neural identification, needle placement and removing the technical bias/error by employing the same imaging approach during both diagnostic and therapeutic blocks. USG guided ILIH pulsed radiofrequency (PRF) was performed the next day by placing a linear transducer probe diagonally along a line joining anterior superior iliac spine (ASIS) and umbilicus with its lateral part resting upon the ASIS. The ILIH nerves were visualized as two hyper echoic shadows in the fascial plane between internal oblique and transversus abdominis from outside-in. A 10 cm radio frequency needle with 5 mm uninsulated tip was advanced in out of plane approach to reach Ilioinguinal and then iliohypogastric nerve medial to it. The patient complained of concordant pain and sensations upon sensory stimulation at 50 Hz and 0.5 V. The PRF was carried at 42°C for 360 min which was associated with a reduction in NRS from 8 to 1 at 1-month follow-up. The patient's medications were gradually tapered, and patient was pain-free off medications at 3 months follow-up postprocedure. The intermittent application of high-frequency electrical current during PRF allows dissipation of heat restricting the maximum temperature to 42°C; hence avoiding neurodestruction and postprocedure neuritis.[4] The electromagnetic field, the neuromodulatory working force of PRF is densest at the electrode tip.[5] Therefore, it is recommended to place the electrode tip perpendicular to the target nerve.[5] An out of plane imaging approach for needle placement falls in sync with this unique mechanism of action of PRF placing its tip in the requisite orientation. Advancements till now have allowed use of USG guidance for peripheral nerve blocks to be practiced as a norm. Adapting and synchronizing the imaging approach with the treatment modality being used is a much-needed next step ahead in the field of USG guided interventional pain medicine. To conclude PRF with USG out of plane approach as the imaging modality is an excellent “treatment-imaging modality” combination for ILIH and other peripheral neuralgias. While the authors experience echoes the same, randomized controlled trials comparing in plane and out of plane approach is a logical way forward.