Growth and transverse line formation in contemporary children
Transverse lines are a frequently used non-specific skeletal indicator of environmental insult in skeletal populations. The prevailing assumption is that transverse lines reflect acute episodes of nutritional, disease, or psychological insult followed by recovery. However, the patterning of transverse lines in skeletal samples generally does not correspond well with other indicators of nutrition and disease insult. Clinical studies suggest that the etiology of transverse line formation is not well understood.
It has also been suggested that transverse line formation is conditioned by rate of growth, although this has not been systematically investigated for contemporary populations. This study was undertaken in order to examine the relationship between bone lengthening and the formation of transverse lines.
Serial tibial radiographs from 104 individuals participating in the Denver Child Research Council growth study were used in this study. Analysis focused on semi-annual change in maximum tibial diaphyseal length and transverse line characteristics.
The results of this study show that there is significant, positive relationship between greater semi-annual growth increment and the formation of transverse lines. This association is observed when all individuals are considered together and is shown within individuals as well. As demonstrated in other studies, line formation is age-related. Even accounting for variation due to age, there is still a statistically significant positive relationship between growth and line formation in both males and females, although this is slightly stronger among males. When the sample is treated cross-sectionally by age, the generally positive relationship between growth velocity and line formation holds, but it infrequently reaches statistical significance.
An alternative explanation for transverse line formation derives from a body of experimental literature which examines the hormonal regulation and control of growth at the epiphyseal cartilage plate. It is argued that transverse lines are a by-product of local, tissue-level control of growth rate. These controls over cartilage cell proliferation would occur in circumstances of rapid bone lengthening as well as inadequate nutrition. Thus, while nutritional insult may be a sufficient but indirect cause of transverse line formation, it is not a necessary condition for lines to form.