Tensile Material Properties of Human Costal Cartilage Perichondrium

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Virginia Tech


Rib and costal cartilage fractures are the most common injuries resulting from blunt thoracic loading scenarios, including motor vehicle collisions. The costal cartilage is a cylindrical hyaline cartilage composed of two layers: a core interstitial matrix enveloped by the perichondrium. The perichondrium itself has an inner chondrogenic layer and an outer fibrous layer. The objective of this study was to evaluate the tensile material properties of human costal cartilage perichondrium at two loading rates for a range of subject demographics. Fifty-six (n=56) samples containing the fibrous layer and chondrogenic layer (i.e., two-layered samples) were fabricated from thirty-three (n=33) donors aged from 11 to 69 years of age (19 M, 14 F). Thirteen (n=13) samples without the fibrous layer (i.e., one-layered samples) were fabricated from eight (n=8) donors aged from 11 to 54 years of age (5 M, 3 F). The perichondrium was isolated from the interstitial matrix for all samples and the fibrous layer was removed for one-layered samples to assess the effect of the absence of the fibrous layer. The tissue was then stamped into a dog bone-shaped coupon and sanded down to a uniform thickness of ~1.3 mm for two-layered samples and ~1 mm for one-layered samples. The gage length of the completed coupons was marked with a black ink dot pattern to facilitate strain calculations via video tracking. The coupons were loaded axially in tension to failure at either a slow (0.005 s⁻¹) or fast (0.5 s⁻¹) target loading rate using a material testing system. The elastic modulus, ultimate stress, ultimate strain, failure stress, failure strain, and strain energy density (SED) were then calculated for each test. Material property data were compared by sample type and loading rate. Since there was no significant influence of sex on any material properties, the data were grouped together for the analysis. Modulus, ultimate stress, failure stress, and SED were found to significantly decrease with donor age at both loading rates and ultimate and failure strain also significantly decreased with donor age at the 0.5 s⁻¹ target loading rate. Failure stress in the two-layered samples was found to be greater than that of the one-layered samples at both loading rates. One-layered samples had a greater failure strain than two-layered samples at both loading rates. Perichondrium data were compared to interstitial matrix data from a previous study to further investigate the role of cartilage layer on material properties. The modulus, ultimate stress, and failure stress of costal cartilage decreased moving radially inward (greatest in two-layered perichondrium samples, least in interstitial matrix samples). The opposite was true for ultimate and failure strain, with the greatest failure strain values occurring in the interstitial matrix and the least in the two-layered perichondrium samples. The sample size of one-layered samples was too small to draw any substantial conclusions regarding age trends. This was the first study to analyze the material property trends in costal cartilage perichondrium. The results of this study can be incorporated into virtual human body models to improve the accuracy of thoracic injury prediction in the context of motor vehicle safety.



perichondrium, cartilage, thorax, thoracic injury, biomechanics, stress, strain, tension