Accuracy of cross-sectional area determining methods for tensile testing of iliotibial band

Determining accurate values on specimen cross-sectional areas is crucial when conducting biomechanical experiments in an effort to derive meaningful properties such as ultimate tensile strength and elastic modulus. Several studies have investigated various methods for cross-section measurements using various soft tissues and applications. Comparison between methods is missing to date especially for (human) biological soft tissues. This given study determined the cross-sectional areas of ten synthetic polyamide 12 and twenty-nine human iliotibial band specimens. It used the following four commonly deployed methods: caliper gauge (CG), molding compound (MC), X-ray micro computed tomography (μCT) and digital image correlation (DIC). The repeatability coefficient was calculated for the four methods and the agreement between the four methods were compared using Bland-Altman plots. All methods but CG offer consistent and reliable measurements of iliotibial band cross section determination, with no difference in their performance levels. In the polyamide specimens, cross-section determination using μCT appeared to provide the best repeatability coefficient RC (0.09 mm2 and 0.18 mm2 with reduced voxel resolution). It shows also for iliotibial band specimens the best agreements especially when compared to MC with a bias less than 1 % and limits of agreements lower ±25 %. The given data suggest that any of the given methods, μCT, MC or DIC can be used effectively for CSA measurements of soft tissues. Minor methodological discrepancies were observed exclusively in specimens with highly uniform geometries. The principal limiting factor appears to be inherent tissue-specific variability rather than the measurement precision of the applied systems. In contrast, due to systematic bias and poor concordance with all other methods investigated, CG cannot be recommended for accurate CSA determination of soft tissue specimens.