Anatomy of the posterior interosseous nerve in relation to fixation of the radial head.

The relationship of the posterior interosseous nerve to the radial neck as it relates to internal fixation of radial head fractures was studied in 50 fresh anatomic specimen arms. After a standard posterolateral approach, blind subperiosteal dissection was performed distally until a 4-cm minifragment plate could be placed on the shaft of the radius. Dissection of the radial nerve was performed under loupe magnification. In only one (2%) arm did the posterior interosseous nerve lie directly on the radius. The average distance from the posterior interosseous nerve to the plate was 5 +/- 1.2 mm. The nerve was not damaged by placement of the plate in any case. In two (4%) cases the nerve play on top of the distal portion of the plate within the supinator with the forearm in neutral rotation. The average distance from the radial head to the origin of the posterior interosseous nerve was 1.2 +/- 1.9 mm, with the takeoff being proximal to the radial head in 31 cases. The muscular branch to the extensor carpi radialis longus was located 7.1 +/- 1.8 mm from the radial head. These findings suggest that pronation of the forearm with blind subperiosteal dissection for plate placement does not place the posterior interosseous nerve at significant risk for structural injury. However, as with any approach done in the region of the nerve, caution should be used to avoid tension on the nerve that could lead to physiologic injury.