Ortopedická protetika Praha sro - Společnost pro pojivové tkáně

somatic proportions. On the basis of characteristic
specific traits of growth dynamics
and development the process of child
ontogeny may be divided into several successive
stages constituting milestones of
the standard periodisation of child age (5).
Growth curves are constructed with
respect to data obtained by longitudinal
growth studies that provide figures concerning
an individual course of growth with
regard to an interindividual variability in
a given population. Average growth curves
of a given trait then serve as a normative
for evaluating its growth velocity in the
diagnostics of growth disorders. Regular
measurements of elementary somatic features
such as body height may signal abnormalities
and represent a limiting criterion
for diagnostic treatment.
The basic presupposition of longitudinal
studies is a long-term observation of the
same group of individuals and their repeated
follow-up examinations in precisely
defined intervals. This implies a number of
complications including projects exhibiting
high demands for organisation. The latter
consist in limited frequencies of examined
groups and a gradual loss of their representative
character owing to irresponsible
individuals, descending mostly from lower
social classes, who are not willing to come
to repeated follow-up examinations.
Another problem is represented by
the danger that some data lose their upto-date
topicality, because after long-term
observations the output results generalise
figures concerning child population that
were collected more than twenty years
ago and the research does not take into
consideration the role of long-term secular
changes. Information concerning growth
dynamics of somatic traits or the start of
course of pubertal growth acceleration
therefore may lose its validity for recent
child population at the time of presenting
scientific results.
Such deficiencies of longitudinal studies
may be solved by semilongitudinal
observations conceived in such a manner
that various age groups of individuals are
subjected to short longitudinal examinations
that take place simultaneously in the
same time interval. After finishing a single
study it is necessary to ensure that different
age groups exhibit neat mutual boundaries
and links. The advantage of correctly
conceived follow-up semilongitudinal
observation is the possibility of collecting
a representative sample of data in a short
interval of time. If we choose appropriate
mathematical models, data obtained
in this way may be applied conveniently
for constructing growth curves of somatic
parameters (14, 16).
MATERIAL AND METHODS
In statistical sense, the data from the
our study certainly fall into the broad category
of longitudinal studies (in the sense
that they contain repeated measurements
of different individuals). We use word
semilongitudinal to denote the particular
design used to distinguish it from the most
simple longitudinal design where observations
are repeated (or planned to be
repeated to be precise) at the same set of
times for all individuals (except perhaps
for random-dropout-related irregularities),
which is often referred to as “the longitudinal
study” in anthropology or other applied
disciplines). Our design is planned so that
it has different sets of time points at which
repeated measurements are taken for different
groups of individuals (for different
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