Histomorphological comparison of immobilization and denervation atrophies.

OBJECTIVE: The aim of this study was to compare the histomorphological changes in the muscle tissue after immobilization and denervation atrophies in an animal model. METHODS: The study included 30 Ross-800 hybrid chickens (60 legs) divided into two study (immobilization and denervation) and two control groups. The knee and ankle joints were fixed with a Kirschner wire in the immobilization atrophy group and sciatic nerve resection was performed in the denervation group. The unaffected side of each group was used as controls. The weight, volume, height, diameter and the rate of elongation of the Achilles tendons, and the amount of fat deposition, degeneration and fibrosis were compared between the two groups at the end of 3 weeks. Hematoxylin-eosin staining was performed for a histopathological assessment of the muscles. The Mann-Whitney U-test was used for comparisons. RESULTS: Loss of the volume, weight and muscle length was significantly lower in the denervation group than the immobilization group (p<0.05). Differences between the diameter of the Achilles tendon and length and diameter of the short heads were not statistically significant. There were statistically significant differences in fat deposition, degeneration and fibrosis between the degeneration group and the immobilization group (p<0.05). Pixel counting revealed a significant difference in the number of pixels in the fatty tissue area (white area) between the denervation group and the immobilization group (p<0.05). CONCLUSION: Our results showed that histomorphological changes were more in the denervation group than the immobilization group in an experimental chicken model.

The effect of femoral lengthening on skeletal muscle: an experimental study in rats.

BACKGROUND: To investigate the muscular changes occurring during femoral lengthening performed in 42 rats. METHODS: The rats were randomly divided into six groups and different rates of lengthening were utilized and the rats were sacrificed at the end of the distraction. Histopathologic and histomorphometric measurements were done for all specimens. The results were analyzed statistically by Mann-Whitney U test. RESULTS: By increasing the rate of lengthening, the severity of pathologic changes such as degeneration of muscle fibers, number of vacuoles and cellular infiltration was increased. Phagocytosis of degenerated muscle fibers was observed after 14 days and cellular infiltration decreased sharply and fibrosis formed in the vacuoles and around the muscle fibers after 21 days of lengthening. Cellular infiltration was lost, the muscle had gained its normal appearance and endomysial, perimysial and epimysial fibrosis formed in the group, which were observed for 31 days. Twenty one percent of muscle fibers were atrophic but the ratio of type I to type II muscle fibers did not change. CONCLUSIONS: The findings of the current study showed that different regions with different phases of degeneration occur in the same muscle and irreversible changes in the muscle may develop even in 10 percent lengthening.