E1645. Utility of Ultrasound-Guided Perineural Anesthetic Injection of the Posterior Interosseous Nerve (PIN) in Diagnosis of PIN Neuropathy
  1. Sagar Wagle; Mayo Clinic
  2. Katrina Glazebrook; Mayo Clinic
  3. John Skinner; Mayo Clinic
  4. Michael Moynagh; Mayo Clinic
  5. Mark Morrey; Mayo Clinic
To demonstrate that ultrasound (US) guided perineural anesthetic injection around the posterior interosseous nerve (PIN) is a safe and effective confirmatory test in the diagnosis of PIN neuropathy, hence useful in selecting patients for PIN decompression surgery.

Materials and Methods:
Following approval by our institutional review board, we retrospectively searched our institutional database for all cases of ultrasound guided perineural injection of the PIN between January 2015 and April 2020. We found 36 patients with 43 perineural PIN injections. They had lateral forearm pain, positive Tinel test over the radial tunnel and/or arcade of Frohse in the forearm, with or without hand weakness, and were suspected of having PIN neuropathy. All patients had received perineural PIN injection of a local anesthetic with or without corticosteroid as a confirmatory diagnostic test of PIN neuropathy. Patient demographics, immediate pre- and post-injection pain (on a severity scale between 0-10, with 0 being no pain and 10 being the worst pain imaginable), whether they underwent nerve decompression surgery, and surgical outcomes were documented. Paired T test was used to calculate statistical difference in the pain score before and after the perineural injection.

Out of 43 cases (25 females and 11 males with age range 16 - 75 years) of perineural injection around PIN, 21 (49%) reported complete pain relief, 16 (37%) reported partial pain relief, and 6 (14%) reported no pain relief. The median pre- and post-injection pain scores were 5 and 0 out of 10, respectively (p <0.001). 23 out of 37 (62%) responders underwent PIN decompression surgery with average post-op follow-up of 113 days (range 14 - 401 days). Out of 23 patients who underwent decompression surgery, 6 (26%) reported complete pain relief, 15 (65%) reported partial pain relief, and 2 (9%) patients reported no relief on their post-op follow-up. All of the 6 patients without any pain relief from the perineural PIN injection continued with non-surgical management. The PIN was visualized and successfully injected in all of the cases without any complications.

Perineural anesthetic injection around PIN can be performed safely with diagnostic potential in identifying ideal candidates for PIN decompression surgery.