How Does Diploic Space Thickness Change With Age?

Cranial defects from trauma, surgery, or congenital conditions require precise reconstruction to restore cranial vault integrity. Autogenous calvarial grafts are preferred for their histocompatibility and biomechanical properties, but their success depends on a well-developed diploic space. Although prior studies have described overall skull thickness development, less is known about how diploic thickness changes through adulthood. This study aimed to quantify diploic thickness and density changes with age using computed tomography (CT) imaging.

A retrospective review of an institution-wide imaging database was performed to identify patients who received CT scans for non-traumatic indications. A total of 110 patients, balanced by sex, were selected across 11 age groups spanning 10 to 109 years. Each patient's skull was aligned to a standardized grid and segmented in 3-dimensional (3D) Slicer using consistent thresholding values to isolate the diploic space from the inner and outer cortical tables. Linear regression models were used to assess the effects of age and sex on diploic thickness.

No statistically significant trends were found between age and diploic thickness ( r =-0.06; P =0.50. However, a near-significant trend of decreasing diploic thickness with age was observed in men ( r =-0.25; P =0.05) but not in women ( r =0.11; P =0.42). The posteromedial parietal region consistently showed the greatest thickness across all age groups. Diploic density also increased significantly with age ( r =0.285; P =0.002), indicating progressive ossification of cancellous bone.

Diploic thickness remains stable across the lifespan with slight sex-based differences. However, examination reveals that the density of the diploe increases over time, suggesting age-related changes in cancellous architecture. These findings highlight the importance of individual anatomical variations when harvesting autogenous calvarial grafts to optimize cranial reconstruction outcomes.