The anatomical relationship between the posterior interosseous nerve and the supinator muscle.

Understanding the anatomical relationships in the region of the supinator muscle is crucial in limiting surgical morbidity. The course, length, and muscular innervations of the posterior interosseous nerve, as well as a detailed dissection of the supinator muscle, were described and recorded in 31 specimens from 16 adult cadavers. In our study, the radial nerve bifurcated into the posterior interosseous nerve and superficial radial nerve 8.0 +/- 1.9 cm distal to the lateral intermuscular septum. The bifurcation of the radial nerve occurred 3.6 +/- 0.7 cm proximal to the leading edge of the supinator, with the posterior interosseous nerve exiting the supinator muscle 3.8 +/- 0.9 cm distal to the proximal margin. The arcade of Frohse was membranous in 68% of our specimens and tendinous in 32%. The supinator had one semicircular head or layer in 71% of specimens and 2 distinct heads or layers, as defined by diverging muscle fibers, in 29%. With 2 heads, or layers, the superficial layer extended to the lateral epicondyle while the deep layer extended to the ulna, below the radial notch.