The purpose of this study was to report the clinical results of interfascicular neurolysis for anterior interosseous nerve palsy (AIN) and posterior interosseous nerve palsy (PIN) with hourglass-like constrictions. Interfascicular neurolysis was performed in 3 patients (including 1 patient with bilateral involvement) with PIN palsy and 1 patient with AIN palsy. Mean age at the time of treatment was 41 years (range, 18-52 years). All patients were initially treated conservatively, but showed no signs of recovery. Surgeries were performed at a mean of 3.8 months after onset (range, 2-7 months). Hourglass constrictions were found in both PIN and AIN. All patients achieved relief from pain or tenderness around the elbow. Finally, all patients showed recovery of muscle strength to better than grade 3 on the manual muscle test after surgery. In cases of AIN and PIN palsy with pain or tenderness around the elbow, interfascicular neurolysis of an hourglass-like constriction of the nerve may be a valid option.
