Changes in morphology of long bone marrow tissue of rats submitted to cryotherapy with liquid nitrogen.

Purpose: To study the main effects of local use of liquid nitrogen on bone marrow tissue in rats.
Methods: The femoral diaphyses of 42 Wistar rats were exposed to three local and sequential applications of liquid nitrogen for one or two minutes, intercalated with periods of five minutes of passive thawing. The animals were sacrificed after one, two, four and 12 weeks and the specimens obtained were analyzed histomorphologically.
Results: In the second experimental week of one-minute protocol, histological degree of inflammation obtained a mean score of one (mild), ranging from 0 (absent or scarce) and two (moderate) (Kruskal-Wallis test p=0.01). In the second experimental week of two-minute protocol, degree of inflammation to the medullar tissue obtained an average score of two (Kruskal-Wallis test p=0.01).
Conclusion: The degree of inflammation of the bone marrow tissue was higher in protocol of three applications of two minutes compared to protocol of three applications of one minute.