All the joints on the left elbow of a newborn are extended, the whole arm hangs vertically along the trunk with the forearm pronated. Active movements in the elbow joint are absent but present in the shoulder joint. The hand is flattened, atrophied, cold to the touch, hangs passively. Grasp reflex and hand-mouth reflex on the affected side are missing. Haemogram values are normal. What is the most likely diagnosis?