A parametric ribcage geometry model accounting for variations among the adult population

Abstract

The objective of this study is to develop a parametric ribcage model that can account for morphological variations among the adult population. Ribcage geometries, including 12 pair of ribs, sternum, and thoracic spine, were collected from CT scans of 101 adult subjects through image segmentation, landmark identification (1016 for each subject), symmetry adjustment, and template mesh mapping (26,180 elements for each subject). Generalized procrustes analysis (GPA), principal component analysis (PCA), and regression analysis were used to develop a parametric ribcage model, which can predict nodal locations of the template mesh according to age, sex, height, and body mass index (BMI). Two regression models, a quadratic model for estimating the ribcage size and a linear model for estimating the ribcage shape, were developed. The results showed that the ribcage size was dominated by the height (p=0.000) and age-sex-interaction (p=0.007) and the ribcage shape was significantly affected by the age (p=0.0005), sex (p=0.0002), height (p=0.0064) and BMI (p=0.0000). Along with proper assignment of cortical bone thickness, material properties and failure properties, this parametric ribcage model can directly serve as the mesh of finite element ribcage models for quantifying effects of human characteristics on thoracic injury risks.

The effect of age and demographics on rib shape

“…; Wang et al. ), albeit with age capable of explaining a relatively low proportion of the overall population variation in rib angle (4% and 7% as reported for males by Kent et al. () and Weaver et al.…”

“…() and Wang et al. (), who reported an increase in the whole rib cage AP depth with age that was associated with a decrease in rib cage width especially in the middle of the rib cage. To the best of our knowledge this is the first study to directly identify these effects as shape changes to the ribs that are independent of other thoracic changes, and the first to quantify both the shape changes themselves and the ability of demographics‐based regression to represent the overall population variability.…”

“…() and a follow‐up study by Wang et al. () applied GPA and PCA to landmarked rib cages from 89 and 101 subjects, respectively, and confirmed an increase in rib angle with age along with increased rib cage depth coupled with reduced rib cage width. Although techniques such as GPA and PCA provide an overall quantification of the rib cage, their results usually combine the changes in bone shape with the changes in bone position and orientation, and the large number of resulting coefficients can be difficult to interpret.…”

Regional maps of rib cortical bone thickness and cross‐sectional geometry

“…(), and local cross‐section (Choi & Kwak, ; Wang et al. ). Nevertheless, the combination of CT and histological image modalities used in this study allows us to establish methods for validating the typical full‐rib properties of this mid‐level rib.…”

“…With ribs of different levels in the rib cage serving different mechanical roles, it is expected that both global and local anatomies will differ accordingly. Indeed, ribs do differ by level in terms of global size and shape (Weaver et al 2014;Wang et al 2016;Holcombe et al 2017), overall mechanical stiffness Kindig et al (2011), and local cross-section (Choi & Kwak, 2011;Wang et al 2016). Nevertheless, the combination of CT and histological image modalities used in this study allows us to establish methods for validating the typical full-rib properties of this mid-level rib.…”