Fetal vertebrae develop through endochondral ossification from a preexisting model. fracture repair of these same bones involves the formation of callus.

Fetal vertebrae develop through endochondral ossification from a preexisting hyaline cartilage  model. fracture repair of these same bones involves the formation of fibrocartilage callus.

Explanation:

Hyaline cartilage is the type of cartilage most easily found in the human body, such as the nose, tracheal rings, larynx, bronchi, ventral ribs, epiphyseal discs (located between the diaphysis and epiphysis of the growing long bones. responsible for bone growth in extension) and joints.  The hyaline cartilage also forms a large part of the embryo's skeleton and is replaced according to the baby's growth by bone skeleton, called endochondral growth. This type of cartilage provides resistance to the tissue. It is through this cartilage that the fetal vertebrae develop through endochondral ossification.

Fibrocartilage is an intermediate tissue between hyaline cartilage and dense connective tissue. It is always associated with dense connective tissue and it is difficult to determine the boundaries between them. However, it is known that the repair of fracture of the fetal vertebrae involves the formation of fibrocartilage callus.