RESUMO
This study was performed to compare the ultrastructural changes of muscles in fracture(group A), fracture with shortening(group B), neurectomy(group C) and fracture with neurectomy(group D) and to search for factors that lead to muscular atrophy. A total of 65 rats weighing about 350g were used as experimental animals. These animals were sacrificed in 3 weeks, 5 weeks and 7 weeks after the operation. The superficial portion (3 X 1 X 1mm3) of the gastrocnemius muscle was dissected and was prepared by routine methods. The results were as follows. 1. The contracted gastrocnemius muscle returned to its normal size at 7th week in group B. However in group C and D, the gastrocnemius muscles atrophied gradually. 2. Under light microscope, fibrotic change and atrophy in the muscles in group C and D progressed as time passed. 3. Myofibrillolysis and kinking of myofibrils in the muscles was observed in group B, and segmentation of Z-line was seen in group 4. At 7th week in group B, the muscles returned to its normal ultrastructures. Irregular shaped myofibrils, streaming of Z-line, dilation of cisternae of sarcoplasmic reticulum and mitochondria with dilation of cristae and electron lucent matrix in group C and the helical complex in the myofibrils of muscle fibers of the rats at 7th week in group D were observed. Consequently, it is suggested that 7 weeks after 20% shortening of tibia in length, contracted gastrocnemius muscles were reformed to its normal shape and the loss of nerve stimuli was a more significant factor that lead to atrophy of the muscle than the decrease of working tension by shortening of bone.
