Anterior interosseous syndrome (Kiloh-Nevin s.)

AI s is due to injury to the branch of the median nerve just past the pronator teres muscle and can be unilateral or bilateral. There is pain in the forearm and elbow, made worse by resisted proximal ip flexion of the middle finger. Asked to make the "OK" sign, patients will make a triangle sign instead (pinch sign). Spontaneous recovery occurs over 6 weeks to 18 months. Identical syndromes can be caused by more proximal lesions, including antecubital level or the brachial plexus, due to prearrangement of the bundles of nerves proximally. Weakness also is seen in fl dig profundus 1 and 2 and PQ.

Nerve conduction may be normal or show a delay from pronator quadratus. EMG is abnormal in the flexor pollicis longus, flexor digitorum profundus I and II, and pronator quadratus.

Associations include trauma, forearm (midshaft radial) fractures, humeral fracture, injection/phlebotomy of antecubital vein, stab wounds, fibrous bands, related to exercise. Occassionally associated with brachial neuritis, CMV infection, bronchogenic carcinoma mets or spontaneous. Consider plexitis.

Other median entrapments occur at the ligament of Struthers, Lacertus fibrosis and the tendinous insertion of FDS. Humeral spur at supracondylar site can produce brachial claudication and radial artery obliteration, exacerbation of numbness and pain by resisted elbow extension and forearm supination.