Growth of the IVD takes place during the first 9 postnatal weeks, although cell proliferation ceases after 3 weeks. After birth, the early postnatal IVD differentiates into 3 tissue types, the NP, the fAF between the vertebrae, and the mineralized endplates over the surfaces of the vertebrae.

During growth and differentiation of the disc, its different components respond at different times to different intercellular signaling ligands. Most of these are dramatically downregulated at the end of disc growth.

A new classification of spinal deformity is proposed that provides a structure for defining deformity of all patient ages and spinal abnormalities.

During growth and differentiation of the vertebral growth plate, its different components respond at different times to different intercellular signaling ligands. Response to most of these signals is dramatically downregulated at the end of vertebral growth.

Reduction of hypermobility caused by extended arthrodesis may represent a new and ideally suited function for PDS devices. Mechanically, the devices were seen to kinematically restore abnormal distal motion, especially with placement of the PDS at the thoracolumbar junction.