The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Robusticity in the axial skeleton: An example of the rib


1Skeletal Biology Research Lab, Division of Anatomy, The Ohio State University, 2Orthopaedic Research Lab, University of Michigan

March 27, 2015 , Archview Ballroom Add to calendar

Skeletal robusticity, (total cross-sectional area relative to bone length) reflects the biological relationship between longitudinal growth and transverse expansion. Many have found robusticity to covary with several morphological traits (e.g., cortical area) and tissue-level properties (e.g., cortical tissue mineral density) throughout the appendicular skeleton. These traits play a critical role in determining whole bone stiffness and strength, a direct reflection of the bone’s ability to functionally adapt to its loading environment. However, the relationship among traits has yet to be investigated in the axial skeleton. We used the rib to preliminarily explore how these traits associate among one another. Cross-sectional images from midshaft of ribs 4-6 from 40 individuals (9 females, 31 males) between 17-48 years of age were analyzed to obtain total area (Tt.Ar), cortical area (Ct.Ar) and section modulus (Z). Curve Length (Cr.Le) was used as a proxy for bone length in calculations of rib robusticity (Tt.Ar/Cr.Le). Preliminary results reveal significant (p<0.01), positive relationships between robusticity and Ct.Ar (R2=0.172), ZPLEURAL (R2=0.532), and ZCUTANEOUS (R2=0.416) that improve slightly with adjustment for age, but not body size. These results indicate that slender ribs have less bone tissue and less resistance to bending, as has been shown in long bones of the extremities, but may be affected differently by body size than appendicular bones. Regardless, robust bones have a consistent functional advantage over slender bones throughout the skeleton. Future analyses will incorporate whole bone bending stiffness and tissue-level properties as a possible source of functional compensation.