Trend in the development of bony acetabulum in newborns with developmental
hip dysplasia was examined during the first year of life. The study compris
ed 120 newborns with developmental hip dysplasia. The degree of dysplasia w
as determined by measuring the acetabular angle (AC) on X-rays of the hips
in the anteroposterior projection. The experimental trend curve was most ad
equate for both the whole group and each subject. The coefficient of trend
was assesed by specially designed iterative method. The exhibited trend for
m allows the extrapolation and prognosis of treatment outcome already after
3-5 measurements of the AC angle. The applied iterative method for the det
ermination of the coefficinet of exponential trend iterated rather quickly.
The chosen. form of the trend curve proved to be adequate for manifestatio
ns in which a constant value is expected after a longer period of time. The
exponential curve represents a mathematical model of the acetabular develo
pment dynamics, with allometric exponents and coefficients of the equation
being numerical parameters that define developmental changes. As the AC ang
le reaches the constant value with the closure of triradiate cartilage, thi
s parameter is an objective measure of the development of bony acetabulum.
When assessing the acetabular growth in developmental dysplasia it is neces
sary to bear in mind that duration, specific position and quantity of newly
formed and remodelled bone are determined genetically, and that external f
actors have a significant influence on the definitive formation.