Concomittant lesions of neural structures represent a rare type of complications in Monteggia's fractures. In acute fractures spontaneous neurological remission usually occurs after reduction of the dislocated radial head. In the presented case a 33-year old man experienced a trady palsy of the posterior interosseus nerve 27 years after a Monteggia's fracture with the radial head left dislocated. Following a minimal trauma in badminton a neurological deficiency probably caused by distraction occurred and resulted in impairment of wrist extension and extension of the fingers. Initiated conservative treatment including intensive physiotherapy and electrotherapy for 4 months was unsuccessful. Consecutively the radial nerve was surgically exposed and released from an entrapping and thickened arcade of Frohse. The radial head was left dislocated. Full neurological recovery was obtained 9 months after surgery.