A person with an injury is not able to extend fingers but able to extend the wrist. The nerve which is injured

Posterior lnlerosseous Nerve It is marked by joining the following three points. A point 1 cm lateral to the biceps brachii tendon just below the level of the lateral epicondyle . The second point at the junction of the uPPer one third and lower two-thirds of a line joining themiddle of the posterior aspect of the head of the radius to the dorsal tubercle at the lower end of the radius or Lister's tubercle . The third point on the back of the wrist 1 cm medial to the dorsal tubercle. Posterior interosseous nerve supplies the muscles of posterior aspect of the forearm . Extension of wrist joint - .The main extensors are; Extensor carpi radialis longus. Extensor carpi radialis brevis. Extensor carpi ulnaris. It is assisted by the extensors of the fingers and thumb . Ref - bdc 6th edition 153,155