Determination of strength and deformation behavior of human cartilage for the definition of significant parameters

Abstract

In reconstructive surgery, an artificial supporting scaffold made from autogenous cartilage from the rib, the ear concha, or the nasal septum is used as a substitute for the destroyed endogenous tissue in the ear concha, the nose, the trachea, and in parts of the facial skeleton. For the successful use of polymer materials in reconstructive surgery, an exact knowledge of the material properties of the natural tissues is required. The applicability of conventional material test methods was examined with regard to the suitability of the test methodology. Materials properties are to be assessed for different specimen sizes and geometries. Human cartilage specimens from the septum, rib, and ear were subsected to the following test methods: (1) tension, (2) bending, (3) compression, and (4) micro-hardness measuring. Specimen geometry was evaluated for each experimental method by taking into account the dimensions of samples used in plastics testing as well as the appropriate model of miniaturization. Elastic properties determined using test methods (1), (2), and (3) are Et-sep=(7.2+/-3.4) MPa, Ef-rib=(8.8+/-2.9) MPa, and Ec-rib=(103+/-30) MPa. The micro-hardness values hpl fluctuate for septum from 1 to 4 N/mm2 and for the rib from 0.5 to 1.3 N/mm2. The experiments have shown that, beside the sex- and age-specific values recorded, the standard values and their variation are particularly influenced by preparation technique and by the conditions of storage. As a result of these first investigations, characteristic values for strength and deformation were determined under quasistatic and dynamic load conditions. The aim of this study was not the determination of statistically firmed properties, but the examination of the applicability of mechanical test methods of the polymer testing for these materials.