| Because it couples the ribs to the sternum, the costal cartilage has the potential to affect the mechanical characteristics of the ribcage as a whole, and should be included in computer models of the human body. There are several factors that may disconnect, however, the material behavior of the costal cartilage and the structural behavior of whole segments of the costal cartilage. The first is the perichondrium---a fibrous, tendon-like layer of connective tissue that surrounds the costal cartilage. Second, the costal cartilage can undergo progressive deposition and growth of local mineralized regions called calcifications. Third, computational models of the whole human body are limited in the mesh resolution with which they represent the costal cartilage.;The goal of this dissertation was to investigate the roles of calcification and the perichondrium in the structural behavior of the costal cartilage, and to provide recommendations on how to model the costal cartilage in finite element models of the human body. The structural behavior of the costal cartilage was quantified experimentally. Data from these tests suggested that the perichondrium contributes an average of approximately 50% of the structural stiffness of the cartilage segments under the loading condition investigated.;The effect of calcification on the structural behavior of the costal cartilage was studied with detailed FE models of cartilage specimens. Those simulations suggested that the structural stiffness of the costal cartilage may increase by an average of 20% with mild calcification, and may increase by as much as a factor of 3.5 with severe calcification.;Finally, a set of limited-mesh representations were developed for each tested cartilage segments. Optimization was used to determine the effective material properties required to reproduce the structural behavior of the cartilage segments. The average effective moduli of the costal cartilage segments (22 MPa) was significantly greater than the cartilage elastic moduli determined from material characterization testing (10 Mpa), presumably due to the presence of calcification and the perichondrium. These models were also used to estimate a relationship between age and effective modulus resulting from the growth of calcifications. |
