gms | German Medical Science

The “Posterior Interosseus Nerve Syndrome” was first described in 1908 by Fröhse and Frankel from Germany. This diagnosis means a rare entrapment syndrome of the deep radial nerve branch beneath the arcade of Fröhse in the proximal forearm. It relies on partial or complete paralysis of the muscles innervated by this so called posterior interosseus nerve. The patients hand is held with the fingers flexed at the metacarpophalangeal joints of any finger. The wrist can be extended but only to the radial side due to remaining innervation of the extensor carpi radialis longus, since its innervation comes proximal to the arcade of Fröhse. Controversy surrounds the treatment of this syndrome until now, because the results of surgical therapy are often not favorable.

At the Department of Neurosurgery in Mainz surgical decompression of posterior interosseus anterior nerve was performed in 16 cases (9 female, 7 male patients). The patients underwent operative treatment between july 1999 and april 2004. The mean age at the date of surgery was 55 years, ranging from 34 years to 83 years. In all patients the target of the surgical therapy was the total decompression of posterior interosseus nerve beneath the arcade of Fröhse and the supinator muscle. Clinical examination of the patients was performed before and 10 days after surgery. The long time clinical results were ascertained between 6 and 24 months after surgery. Preoperative complaints, surgical technique, postoperative results and complications of the therapy are presented.

The overall success rate in our study was 14/16 (87.5%). 5/16 (31%) patients demonstrated full strength of finger- and wrist-elevation after surgery. An improvement in preoperative paresis could be noted in 9/16 (56%) patients. 2/16 (12%) preoperative pareses remained unchanged. Deterioration was not observed. The complication rate in our series was 1/16 (6%), because 1 patient suffered from a compartment syndrome after surgery which had to be decompressed by a further operation. Other kinds of complication did not occur.

Summing up, it may be said that neurosurgical decompression of deep radial nerve branch in the proximal forearm appears to be an effective and safe method for the treatment of posterior interosseus anterior syndrome.