Comparison of Bending Properties in Paired Human Ribs with and without Costal Cartilage

Thoracic injuries, most frequently rib fractures, commonly occur in motor vehicle crashes. With an increased reliance on human body models (HBMs) for injury prediction in various crash scenarios, all thoracic tissues and structures require more comprehensive evaluation for improvement of HBMs. The objective of this study was to quantify the contribution of costal cartilage to whole rib bending properties in physical experiments. Fifteen bilateral pairs of 5th human ribs were included in this study. One rib within each pair was tested without costal cartilage while the other rib was tested with costal cartilage. All ribs were subjected to simplified A-P loading at 2 m/s until failure to simulate a frontal thoracic impact. Results indicated a statistically significant difference in force, structural stiffness, and yield strain between ribs with and without costal cartilage. On average, ribs with costal cartilage experienced a lower force but greater displacement with a longer time to fracture compared to isolated ribs. Comparisons were complicated by varying levels of calcification between costal cartilages and varying geometry with the inclusion of the costal cartilage. This study highlights the important effects of costal cartilage on rib properties and suggests an increased focus on costal cartilage in HBMs in future work.