There are three primary ossification centers and five secondary sites of development in the human vertebra. The centrum and two halves of the vertebral arch form as primary centers and are present at birth. During puberty, epiphyses appear at the tips of the transverse processes, the spinous process, and the superior and inferior surfaces of the vertebral body (epiphyseal rings). Fusion rates are variable with developmental completion occurring at approximately 25 years of age.