Biomechanical and Microbiological Analyses in Dogs Cadavers Subjected to Different Protocols of Fixation

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Abstract Body : Introduction: This research aimed to determine the feasibility of new protocols related to anatomical techniques for the fixation and conservation of dog cadavers, through the injection of a curing salt solution, prior to the fixation agent composed of ethyl alcohol (EA) and formaldehyde in different proportions. The storage of the cadavers was in a tank with 30% sodium chloride aqueous solution (30% SACS). Biomechanical and microbiological analyzes were performed during fixation and conservation.
Materials and Methods: The cadavers were randomly assigned to 4 groups consisting of eight animals. Before injecting the curing salt and the fixative solution, three samples of skin and jejunum were collected (fresh samples/control). All the groups were injected with 120 mL/kg of curing salt solution (20% sodium chloride, 1% nitrite, and 1% sodium nitrate solution), and then, group 1 was injected (G1) with 100% formaldehyde, group 2 (G2) with 30% formaldehyde and 70% ethyl alcohol (AE), group 3 (G3) with 70% formaldehyde and 30% AE and, group 4 (G4) with 50% formaldehyde and 50% AE and were maintained for 7 days in a tank with a 10% formaldehyde solution. After, the cadavers were washed for 2 days and transferred to another tank with 30% SACS (considered day 0) and kept for 120 days. The skin and jejunum were collected before fixation, on 0 (D0), 30 (D30), 60 (D60), 90 (D90), and 120 (D120) days, and biomechanical analyzes were performed. For the microbiological analysis, the deep plating technique was tested using conservation solutions.
Results: One-way ANOVA was applied for all times and each treatment separately. Each treatment and time were compared to the control samples (fresh) with the paired T-test. There was no statistical difference in the skin and jejunum for the maximum rupture force (MRF) between the control, the fixation, and conservation times. When comparing fresh samples with D120, the smallest variations were observed in groups G2 and G3, which presented the MRF of the samples with differences between the skin (-14.2N) and jejunum (-0.28N) means, respectively. Regarding the rupture elongation (RE) of the skin, there were significant differences at D30 in G2 and G3 and, at D120 in all groups, whereas in relation to the jejunum there was a significant difference at D120 in G1 and G2. The G3 and G4 presented small variations in the RE of the samples, with a difference between the skin (1.32mm) and jejunum (0.23mm) means, respectively. In the microbiological analysis of the 30% SACS, no aerobic and anaerobic microorganisms were identified in Groups 1, 2, 3, and 4 at D120, and the presence of Bacillus sp was detected in 1.0 x 10 CFU/mL.
Conclusion: The protocol of G3 is the best option for the fixation of cadavers as permanent specimens, which could be used in anatomy and, eventually, veterinary surgery classes due their biomechanical characteristics and microbiological control.