Crosado embalming related alterations in the morpho-mechanics of collagen rich tissues

Crosado-embalming has been successfully used as embalming technique in research and teaching for over 20 years. It is applied in biomechanical testing experiments if the fresh tissues are unavailable, e.g., for cultural, ethical, logistical or health and safety reasons. However, features of human Crosado-embalmed tissues biomechanical characteristics including its load-deformation properties in comparison to fresh tissues and its controllability through hydration fluids may be insightful and therefore need to be studied further. This study compared the uniaxial load-deformation properties and the cross-sectional area (CSA) measurements of fresh-frozen and Crosado-embalmed collagen-rich tissues, namely the iliotibial band (ITB, 16 unembalmed and 35 embalmed specimens) and cranial dura mater (DM, 60 unembalmed cadavers, and 25 embalmed specimens). The water content of 120 Crosado-embalmed ITB samples (30 cadavers) were analysed considering established rehydration treatments, including polyethylene glycol (PEG). Crosado-embalmed tissues presented an increased elastic modulus (EM) (all p < 0.050; e.g., Crosado ITB PEG only 306 ± 91 MPa vs. fresh-frozen ITB PEG only 108 ± 31 MPa; mean ± standard deviation; p < 0.001) and ultimate tensile strength (UTS) (e.g., Crosado ITB PEG only 46 ± 15 MPa vs. fresh-frozen ITB PEG only 21 ± 8 MPa; p < 0.001) when rehydrated similar to the fresh tissues. The maximum force was different for the dura mater (Crosado 25 ± 13 N vs. fresh 21 ± 20 N; mean ± standard deviation; p = 0.050) but not for the ITB. The CSA following rehydration in PEG only was decreased for Crosado-embalmed samples (3.4 ± 1.2mm², ITB; 1.1 ± 0.5 mm², DM) compared to fresh-frozen (5.8 ± 2.1mm², ITB; 3.1 ± 1.2mm², DM) (all p ≤ 0.003). Furthermore, rehydration effects were observed following 24 h of PEG treatment (untreated tissues, 49 ± 9% vs. PEG only, 77 ± 4%; p < 0.001), in comparison to fresh samples (69%) tissues were hyperhydrated. In conclusion, Crosado-embalming appears to alter collagen-rich tissues' morphological and mechanical properties. While an increase in material properties of Crosado-embalmed tissues was observed (Emod and UTS), the overall load-bearing capacity and peak structural strength remained unaltered for ITB tissues. This may result from CSA-related, geometric or molecular alterations after the fixative and osmotic water protocols related to changes in the collagen backbone and water-binding capacity.