A. 30-year-old male underwent excision of the right radial head. Following surgery, the patient developed inability to extend the fingers and thumb of the right hand. He did not have any sensory deficit. Which one of the following is the most likely cause?

Radial nerve injury -        High radial nerve palsy- Injury above the spiral groove. o   Paralysis of all muscles supplied by radial nerve. o   Clinical features Wrist drop, finger drop, thumb drop Extension affected of- elbow, wrist, thumb and fingers Sensation affected of- posterior surface of arm and forearm and lower lateral half of forearm. -        Low radial nerve palsy- Injury below the spiral groove. o   Type I- Injury between spiral groove and elbow. Elbow extensors are spared- Triceps and Anconeus. Wrist, thumb and finger extensors paralysed- wrist drop, thumb drop, finger drop. Loss of sensation on dorsal side of first web space. o   Type II- Injury below the elbow joint. Elbow and wrist extensors spared Thumb and finger extensors paralysed.(extensor digitorum, extensor digiti minimi, extensor indicis, extensor pollicis longus, extensor pollicis brevis)- Thumb drop and finger drop. Loss of sensation on dorsal side of first web space.  In radial nerve head surgery, the most common nerve to get injured is posterior interosseous nerve. There is thumb and finger drop. Extension of wrist is spared.