Final answer:
The condition where long bones stop growing in childhood without affecting the axial skeleton is achondroplasia, a disorder affecting the epiphyseal plate.
Step-by-step explanation:
The disorder in which the long bones stop growing in childhood but the bones of the axial skeleton are not affected is called achondroplasia. Achondroplasia is a form of short-limbed dwarfism where the epiphyseal plate is abnormal, resulting in the stoppage of bone lengthening in long bones. The axial skeleton, which includes the skull, spine, and rib cage, typically continues to develop normally. In individuals with achondroplasia, the mutation affects the growth of the appendicular skeleton, which is primarily composed of the limbs, but does not affect the axial skeleton to the same degree.