When surgical procedure to treat perineal hernia fails it is necessary to use salvage procedures for pelvic diaphragm reconstruction. The transposition technique of the semitendinosus muscle is one of the recommended methods. This study was undertaken to evaluate the transposition technique of the semitendinosus muscle for its utilization in the repair of pelvic diaphragm using electromyographic, ultrasonographic, and morphologic studies.

Ten male adults crossbreed dogs, from 3 to 4 years old were used. The left semitendinosus muscle was cut close to the popliteus lymph node, rotated and sutured at the perineal region. The contralateral muscle was considered as control. The motor nerve conduction study of both sciatic-tibial nerves, and electromyographic and ultrasonographic exams of both semitendinosus muscles were performed before the surgical procedure and at 15, 30, 60 and 90 days postoperatively. Samples of the semitendinosus muscles were collected for morphological analysis 90^th days after surgery.

The left semitendinosus muscle presented an accentuated degree of longitudinal shortening after transection (an average of 2.51 cm). In general, the transposed muscle acquired a heterogeneous pattern characterised by irregular distribution of the echoes with hyperechoic and hypoechoic areas. There was no difference in motor nerve conduction velocity, latency and amplitude of the sciatic-tibial nerves between members and among evaluation moments. In all animals activity at rest was normal and action potentials at slight effort were present on day 90 after surgery. The sections of the transposed semitendinosus muscle showed normal pattern areas and several degrees of abnormal areas by morphologic analysis.

It was possible to conclude that according to the electromyographic studies, the transposed muscle was able to contract, but showed some degree of atrophy detected by ultrasonographic and morphologic analyses.