Morphometric analysis of variation in the ribs with age and sex

Abstract

Rib cage morphology changes with age and sex are expected to affect thoracic injury mechanisms and tolerance, particularly for vulnerable populations such as pediatrics and the elderly. The size and shape variation of the external geometry of the ribs was characterized for males and females aged 0-100 years. Computed tomography (CT) scans from 339 subjects were analyzed to collect between 2700 and 10 400 homologous landmarks from each rib. Rib landmarks were analyzed using the geometric morphometric technique known as Procrustes superimposition. Age-and sex-specific functions of 3D rib morphology were produced representing the combined size and shape variation and the isolated shape variation. Statistically significant changes in the size and shape variation (P < 0.0001) and shape variation (P < 0.0053) of all 24 ribs were found to occur with age in males and females. Rib geometry, location, and orientation varied according to the rib level. 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. The increased roundedness of the rib cage and horizontal angling of the ribs relative to the spine with age influences the biomechanical response of the thorax. With the plane of the rib oriented more horizontally, loading applied in the anterior-posterior direction will result in increased deformation within the plane of the rib and an increased risk for rib fractures. Thus, morphological changes may be a contributing factor to the increased incidence of rib fractures in the elderly. The morphological functions derived in this study capture substantially more information on thoracic skeleton morphology variation with age and sex than is currently available in the literature. The developed models of rib cage anatomy can be used to study age and sex variations in thoracic injury patterns due to motor vehicle crashes or falls, and clinically relevant changes due to chronic obstructive pulmonary disease or other diseases evidenced by structural and anatomic changes to the chest.

Ontogeny of 3D rib curvature and its importance for the understanding of human thorax development

“…Such lowering, which has been observed previously (Openshaw, 1984;Bastir et al, 2013a,b;Weaver et al, 2014), could be a mechanical rotation at the costovertebral joint (extrinsic rib factor). In fact, a classic text book on human anatomy (Gray, 1918) suggests that this lowering is caused by rotation of the ribs because of gravitational effects related to posture.…”

“…Specifically, some authors (Openshaw et al, 1984;Bastir et al, 2013a, b;Weaver et al, 2014) have found that from newborns to young adults (not the elderly), lowering of the ribs relative to the spine into the sagittal plane and medio-lateral expansion of the ribcage in the axial plane are the main factors which configure the shape of the adult rib cage. However, Bastir et al (2013b) have suggested that these factors do not occur in the same way at the upper and lower thorax, suggesting modular growth.…”

“…Some authors have addressed ribcage ontogeny considering it as a whole (Openshaw, 1984;Gayzik et al, 2008;Shi et al, 2014;Weaver et al, 2014) but there is evidence that morphological growth changes at the upper rib cage could be different from those at the lower (Bastir et al, 2013a,b). Different morphometric patterns of the upper and lower thorax have been observed not only during human ontogeny but also in the sexual dimorphism of the thoracic vertebrae or even throughout the evolution of the thorax shape in different hominin lineages (Bastir et al, 2013bSchmid et al, 2013;Garc ıa-Mart ınez et al, 2014a,2014bGarc ıa-Mart ınez and Bastir, 2015).…”

“…Nevertheless, in recent years it has received special attention in different fields of study such as biomechanics or evolutionary biology (Gayzik et al, 2008;Bastir et al, 2013a,b;Shi et al, 2014;Weaver et al, 2014). This is in part due to methodological advances and improvements in morphometric quantification due to the use of semilandmark methods (Bastir et al, 2013a(Bastir et al, ,b, 2015Garc ıa-Mart ınez, 2013;Garc ıa-Mart ınez et al, 2013Shi et al, 2014;Weaver et al, 2014). However, it should be noted that this research has mainly focused on the variability of thorax morphology in anatomical connection.…”

Development and Validation of a Musculoskeletal Model of the Fully Articulated Thoracolumbar Spine and Rib Cage

“…For instance, the study of vertebral fracture etiology requires a model representative of an older adult population. Other factors that vary between individuals and likely influence in vivo loads, such as spine curvature [63][64][65] and rib cage size and shape [17,66,67], can also easily be incorporated in future versions of the model to provide an even better subject-specific model.…”