Thermal Effect of Therapeutic Ultrasound on Muscle-Bone Interface of Swine Tissue (Sus Scrofa Domesticus) with Metallic Implant

Therapeutic ultrasound (UST) has thermal biological effects produced by mechanical waves that vibrate continuously to reach temperatures between 40 and 45 °C for about 5–10 min to produce beneficial physiological changes. Several researches with the objective of studying the field and the thermal effect of UST in metallic implants, were carried out in phantoms, animals in vivo and ex vivo. This work aimed to investigate the effects of therapeutic ultrasound on the muscle/bone tissue-swine interface (Sus scrofa domesticus) with metallic implant through thermography and histopathology. After placing the metallic implant, the piece was sutured, and placed in a controlled thermal bath at 36 °C and irradiated with therapeutic ultrasound for 10 min, at a frequency of 1 MHz, intensity 2 W/cm², stationary mode. The tissue temperature was measured before and after the application of therapeutic ultrasound. The thermographic image of the piece after the ultrasound application clearly shows the points of greatest heating were outside the metal region, in the lateral musculature with an average of around 49.1 °C. The muscular region above the metallic part had an average temperature of 46.3 °C while the metallic implant had an average temperature of 40.7 °C. Histopathology shows some cell injuries in the skeletal striated fibers (peroneal muscle) in an area where there was a metallic implant. The causes of cell injuries have not been clarified in the current study. It was not possible to diagnose whether the use of UST contributed to the formation of physical cellular lesions found in the fibers.