Posterior interoseous nerve (PIN) syndrome is an entrapment of the deep branch of the radial nerve just distal to the elbow joint. It may result in the paresis or paralysis of the fingers and thumb extensor muscles.

We present a review of 26 cases of PIN entrapment syndrome, diagnosed an treated over a ten years period form 1996 to 2005. Their ages ranged form 12 to 57 years, they were 18 men and 8 women. The interval between, the onset or paralysis and operation ranged from 4 months to 1 year. All the patients were diagnosed preoperatively as having PIN palsy from physical examination and electromyographic (EMG) studies of the posterior interoseous innervated muscles and all were treated by operation.

The cause of compression was, ganglia in four cases, fascia thickening at the arcad of frohse in six cases, the radial recurrent vessels in three cases, lipoma in four cases, dislocated head of the radius in two cases, infamed synovium in four cases, tumour in two cases, and Intraneural Perineurioma in one case. The periods of postoperative observation were from 1 to 10 years. The paralysis recovered completely by the six postoperative months in all cases except one girl with intraneural peri-neurioma.

Three patients developed mild reflex sympathetic dystrophy which resolved with physiotherapy and auxilary blocks. Two patients developed hyperaesthesia in the distribution of the superficial radial nerve which recovered in a few weeks.

Having arrived at a diagnosis of PIN syndrome, it is important to select the correct level for the release of the radial nerve. Fair or poor results can be due to incorrect diagnosis, incomplete release or irreversible nerve injury.