Quantitative anatomical study of the posterior interosseous nerve

An anatomic study of the posterior interosseous nerve (PIN) in 20 cadaver upper limbs was performed to measure different segments of the PIN and its relationship with radius and ulna (results given as mean +/- SD). The length of the PIN from radial head to the arcade of Frohse (AF) was 26.5 +/- 1.6 mm and 25.3 +/- 1.1 mm in male and female cadavers, respectively. The length of the PIN from radial head to the PIN exit point from the supinator was 66.7 +/- 4.7 mm and 64.0 +/- 2.5 mm in male and female cadavers, respectively. The overall length of the PIN underlying the supinator muscle was 44.0 +/- 0.5 mm and 37.0 +/- 0.5 mm in male and female cadavers, respectively. The distance between the PIN exit point from the supinator and the radial margin of the radius was 15.0 +/- 0.9 mm and 14.5 +/- 0.9 mm in male and female cadavers, respectively. The distance between the PIN exit point from the supinator and ulnar margin of ulna was 18.2 +/- 0.6 mm and 17.9 +/- 0.7 mm in male and female cadavers, respectively. In 70% (n = 14) of the cadavers, the AF was tendinous and in 30% (n = 6), it was membranous. The length, width, and thickness of AF in males and females, respectively, were 18.6 +/- 1.2 mm / 18.5 +/- 1.3 mm; 2.8 +/- 0.4 mm / 2.5 +/- 0.4 mm; and, 0.8 +/- 0.08 mm / 0.7 +/- 0.07 mm. In all specimens, the PIN exited through the distal supinator muscle by penetrating the muscle. The PIN exit point from the supinator belly was about 11-19 mm from distal border of the latter. The mean distances between PIN exit point from the supinator and the origin of the extensor digitorum communis, abductor pollicis longus, and extensor pollicis longus branches were 7.5 mm, 31 mm, and 58 mm, respectively.