Etiopathogenesis of M. semitendinosus and M. semimembranosus atrophy after performing experimental surgical and conservative restoration of ischial bone

Purpose. To reveal the pathologic changes and determine the response of m. semitendinosus and m. semimembranosus of experimental animals after ischial bone fracture under external fixation and conservative treatment. Materials and Methods. The experiments performed in 35 adult mongrel dogs. An unilateral transverse fracture of ischial bone body and branch produced with further surgical and conservative treatment. Radiographic, anatomical, and histological methods of studying used. Results. There was no bone fragment displacement in case of surgical treatment in Series I. As for Series II, when conservative treatment performed the displacement of ischial bone fragment revealed by X-rays by Day 35 of the experiments, and this displacement developed ventrally in the sagittal plane with forming the angle of 32.5±12.5°. Ischial bone restoration after fragmental fracture by surgical or conservative method accompanied by more marked injuring m. semimembranosus comparing with m. semitendinosus. When there was no stable fixation of bone fragments, or in case of their significant displacement m. semimembranosus didn’t recover in the previous volume by the end of the experiment, while m. semitendinosus tended to its recovery. Reposition and stable fixation of fragments with an external fixator accompanied by moderate destructive changes in the both muscles studied. When conservative treatment performed, histological signs of muscle atrophy were characteristic of the muscles yet at the early stages of the study, and besides the atrophy manifested itself as the increase of sarcolemmic nuclei in number, that of fatty degeneration of muscle fiber bundles, group atrophy of fibers, and also as the intensified fibrosis of endo- and perimysial spacing. Conclusion. Displaced ischial bone fractures should be treated using internal or external fixation.