The influence of different sample preparation on mechanical properties of human iliotibial tract

Abstract

In the run-up to biomechanical testing, fresh human tissue samples are often frozen in order to inhibit initial decomposition processes and to achieve a temporal independence of tissue acquisition from biomechanical testing. The aim of this study was to compare the mechanical properties of fresh tissue samples of the human iliotibial tract (IT) to fresh-frozen samples taken from the same IT and those modified with different concentrations of Dimethylsulfoxide (DMSO) prior to freezing. All samples were partial plastinated and destructive tensile tests were conducted with a uniaxial tensile test setup. A plastination technique already established in the laboratory was modified to improve the clamping behaviour of the samples. Material failure was caused by a gradual rupture of the load-bearing collagen fibre bundles. Contrary to our expectations, no significant difference was found between the tensile strength of fresh and fresh frozen specimens. The addition of 1 wt% DMSO did not increase the tensile strength compared to fresh-frozen samples; an addition of 10 wt% DMSO even resulted in a decrease. Based on our findings, the use of simple fresh-frozen specimens to determine the tensile strength is viable; however fresh specimens should be used to generate a complete property profile.

Figure 1

Left: Harvested IT with extraction area of the four samples (black outline). The curvature is a result of the placement of the iliotibial tract; Right: Extracted samples prior to plastination.

Figure 2

Scheme of sample preparation.

Figure 3

Dimensions of the beech wood panels used (5 × 25 × 30 (H × W × D) mm).

Figure 4

Cross section through the plastinated clamping zone. A conclusive material bond between wood (A), resin-hydroxide mixture (B) and plane-parallel embedded iliotibial tract specimen can be recognized (C).

Figure 5

Procedure for uniaxial tensile testing. Left: Under preload. Clearly visible at the edges left and right of the test area is the superficial tissue layer, which is not load bearing and masks the collagen fibre bundles, Mid: Immediately before failure, Right: After exceeding tensile strength and incipient failure of collagen fibre bundles at the bottom right area.

Figure 6

Stress–Strain-curves of different sample types: fresh (I), 0% DMSO (II), 1% DMSO (III) and 10% DMSO (IV).

Figure 7

Mean tensile strength (MPa) and Mean Young’s Modulus (MPa).