Posterior interosseous nerve

The deep motor branch of the radial nerve in the forearm. Its terminal branch runs on the floor of the fourth extensor compartment to the back of the wrist capsule, carrying sensation from the joint. It lies in the field of dorsal ganglion excision; a short segment may be excised (neurectomy) to reduce wrist pain, although its benefit at ganglion surgery has not been shown.

Related terms

• Condition

  Ganglion cyst

  A benign cyst filled with thick, clear mucin and joined by a stalk to a nearby joint capsule or tendon sheath; its wall has no true synovial lining. It is the commonest lump of the hand and wrist and arises most often on the back of the wrist over the scapholunate ligament, on the front of the wrist beside the radial artery, from a finger's flexor tendon sheath, or as a mucous cyst at the end joint. About half resolve without treatment.

• Anatomy

  Superficial radial nerve

  The sensory branch of the radial nerve that runs under the skin of the forearm to supply feeling over the back of the thumb and the web space. Its branches often cross the first extensor compartment, so they are protected during surgery there; handling them can cause temporary tingling, and injury can leave numbness or a painful neuroma.

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