Thoracic anthropometry variations with age and gender are expected to affect thoracic injury mechanisms and tolerance. The objective of this research was to quantify the age and gender-specific variations in the thoracic skeletal morphology for both genders and across the entire age spectrum (ages 0-100). A semi-automated image segmentation and registration algorithm was developed to collect homologous thoracic skeleton landmarks from 343 normal computed tomography (CT) scans. Rigid, affine, and symmetric diffeomorphic transformations were used to register landmarks from an atlas to homologous locations to each subject-specific coordinate system. Between 2,700 and 11,000 landmarks were collected from each rib and sternum and over 55 million total landmarks were collected from all subjects.

The Generalized Procrustes Analysis (GPA) was used to analyze the homologous landmark data. Age and gender-specific functions of 3D rib and sternum morphology were produced representing the combined size and shape variation and the isolated shape variation of each bony structure. Statistically significant changes in the size and shape variation (all p < 0.0001) and shape variation (all p < 0.0053) of all 24 ribs and the sternum were found to occur with age in males and females. From birth through adolescence, the rib cage experienced an increase in size, a decrease in thoracic kyphosis, and inferior rotation of the ribs relative to the spine within the sagittal plane. From young adulthood into elderly age, the rib cage experienced increased thoracic kyphosis and superior rotation of the ribs relative to the spine within the sagittal plane. More dramatic changes in sternum morphology occurred in childhood and young adulthood when the sternum was undergoing ossification. From birth through age 30, the sternal size increased, the manubrium became wider in relation to the sternal body, and the distal sternal body became wider than the proximal sternal body. The morphological functions were used to create detailed models representing thoracic variation with age and gender. These models can be used to study age and gender variations in thoracic injury patterns due to motor vehicle crashes (MVCs) or falls, and clinically relevant changes due to chronic obstructive pulmonary disease (COPD) or other diseases.