Abstract
Four cases of constrictive neuropathy of the posterior interosseous nerve (PIN) in the absence of external compression are reported. All patients presented with a history of severe elbow pain with no apparent cause, followed by paralysis of the PIN. There were one or two well-localized constrictions on the PIN proximal to the arcade of Frohse where no obvious external compressive structure was observed. After epineurotomy with or without neurorrhaphy, three patients had a complete return of motor function within 1 year. The remaining patient required tendon transfer after resection of the abnormal segment of nerve.