POSTERIOR INTEROSSEOUS NERVE (PIN)

SUMMARY

1. Branch of the radial nerve.
 2. Enters the posterior compartment of the forearm through the two layers of the SUPINATOR. 
3. It then passes downwards over the APL origin to reach the interosseous membrane, on which it passes to the wrist.
4. Here it ends in a small nodule, from which branches supply the wrist & intercarpal ligaments. 

SUPPLY
5. Sensory supply - interosseous membrane, periosteum of radius & ulna, periosteum & ligament of carpal bones. 
6. Motor supply - supplies all the muscles on the radial side and dorsal surface of the forearm, except the ANCONAEUS, BRACHIORADIALIS, ECRL.

Image: Gray, Henry. Anatomy of the Human Body. Philadelphia: Lea & Febiger, 1918; Bartleby.com, 2000. www.bartleby.com/107/ [Accessed 17 Apr. 2019]. 

Reference(s)

R.M.H McMinn (1998). Last’s anatomy: regional and applied. Edinburgh: Churchill Livingstone.
Gray, H., Carter, H.V. and Davidson, G. (2017). Gray’s anatomy. London: Arcturus.