The object of this study is to compare the growth and
development of a lumbar intervertebral disc with those in the
thoracic and cervical regions from embryonic life to childhood.
Particular attention is paid to changes during and following the
establishment of the secondary curvatures of the vertebral column.
Current knowledge of development of the intervertebral disc is
Postmortem material from 67 cases and a large series of
radiographs are used in histological and mensural studies. The
vertical dimensions of the 'total disc' (which includes the
cartilage plates), its parts, and the vertebral body above the disc
are measured in each region at every age. Notochordal remnants in
vertebrae and discs are used as 'natural markers' from which
horizontal dimensions are measured in the median plane to give an
indication of growth anteriorly and posteriorly from the position
of the notochord.
Notochordal cells appear to multiply during foetal life
and infancy, playing an important role in growth and extension of
the notochordal nucleus pulposus up to about three years, but
they degenerate and disappear from about three to seven years.
As the notochordal nucleus pulposus grows rapidly in
V volume, principally by increase in its macoid matrix (notably in
lumbar discs), the anulus fibrosus and cartilage plates bounding
it become thinner. Associated with thinning of the cartilage
plates, vertical growth of the central part of the 'total disc'
slows down during the first two postnatal years.
As secondary cervical and lumbar curvatures are
established, the cervical and lumbar notochordal nuclei pulposi
respectively move to more anterior and central positions, but the
thoracic notochordal nucleus pulposus remains posteriorly situated.
From two years onwards, the central parts of lumbar discs grow
rapidly in height though the heights of the central parts of
thoracic discs remain almost unchanged. The central situation of
the lumbar nucleus pulposus in childhood, and the rapid increase in
height of the central part of the lumbar 'total disc' from two to
seven years are associated with corresponding changes in the shape
of the cephalic and caudal end surfaces of lumbar vertebral bodies
from convexity to concavity.
During the same period (about two to seven years) there
is an increase in the rate of antero- posterior growth of the lumbar
vertebral column without any increase in its lateral growth rate.
The present investigation throws further light on the
work of Houston and Zaleski (1967) who demonstrate a relationship
between 'activity' and vertebral body shape, and suggests that the
rate of anteroposterior growth of the lumbar vertebral column, the
the rate of vertical growth of lumbar vertebrae and 'total discs',
and their changes in shape during childhood, all depend to some extent on the assumption of the normal erect posture.