Analysis of muscle morphology and knee joint range of motion of rat preserved using a modified Larssen solution

Cadavers are essential for anatomical education, but limited availability necessitates long-term preservation. While formalin is widely used, it is carcinogenic and alters muscle morphology and joint mobility, reducing anatomical accuracy. The modified Larssen solution (MLS) has shown promise in improving joint flexibility, yet its efficacy remains underexplored. This study aimed to evaluate muscle condition and joint range of motion in rat specimens preserved with 4% formalin followed by MLS immersion, compared to continuous 4% formalin preservation. Eighteen rat cadavers were allocated into three groups: intracardiac perfusion followed by 0.9% NaCl immersion, intracardiac perfusion and three-month immersion in 4% formalin, and intracardiac perfusion with 4% formalin followed by three-month immersion in MLS. Statistical analysis included the t-test or Mann-Whitney test, depending on data distribution. Pearson correlation was used to assess the relationship between muscle fiber fragmentation and joint range of motion. Data from the NaCl group were excluded due to sample decomposition. The MLS group showed significantly redder muscle color (P<0.05), softer muscle consistency (P<0.05), and a non-significant increase in joint range of motion (P>0.05), without observable muscle fiber fragmentation. Correlation analysis could not be conducted due to the absence of fragmentation. MLS may serve as an effective alternative preservative by maintaining muscle color, texture, and structural integrity. Although the increase in joint mobility was not statistically significant, it was more pronounced than in the 4% formalin group. Future studies should explore longer observation periods and potential correlations with histological findings.