Disclosures: Abraham Alfaro, PhD, DO: Owns AbbVie Stock (Products/Services: No) (Stockholder/Ownership Interest (excluding diversified mutual funds))

Background and/or Objectives: To assess the effects of anterior interosseous nerve (AIN) injections with phenol or lidocaine on finger flexor spasticity.

Design: Retrospective study with data analyzed by t-tests with repeated measures.

Setting: Outpatient rehabilitation medicine clinic.

Participants: Patients who have finger flexor spasticity due to an upper motor neuron lesion; 18 patients had a stroke, 4 had a traumatic brain injury, and one had a glioblastoma multiforme. There were 18 men and 9 women who received a total of 27 injections. On separate occasions, two patients were injected twice, and one patient was injected 3 times.

Interventions: AIN and flexor digitorum profundus (FDP) motor point injections with Phenol 5% in sterile water.

Main Outcome Measures: Modified Ashworth Scale (MAS) that ranges from 0 (no spasticity) to 4 (contractures).

Results: Twenty three patients received a total of 27 injections; 26 were with phenol and one was with lidocaine. The mean ± standard deviations was: 55.9±12.8 years for age; 0.63±0.58 mA to stimulate the AIN when injected; 2.4±1.4 sites injected; 0.83±0.31 mL of phenol or lidocaine injected per patient; 0.41±0.18 mL of the substance injected at each site; and 3.12±0.38 for the MAS pre-injection and 1.41±0.51 post-injection. The MAS decreased significantly (p < 0.01) from pre- to post-injections.

Conclusions: AIN injections with phenol or lidocaine can significantly decrease finger flexor spasticity by decreasing innervation for FDP and flexor pollicis longus muscles. Since the FDP muscle flexes the distal interphalangeal joints (DIP) and then the proximal interphalangeal joints (PIP), an AIN block may decrease flexion for both DIP and PIP joints if the flexor digitorum sublimis is not spastic.

Level of Evidence: Level III

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/anterior-interosseous-nerve-injections-decrease-finger-flexor-spasticity/