The influence of low-intensity physiotherapeutic ultrasound on the initial stage of bone healing in rats: an experimental and simulation study

BACKGROUND: Low-intensity physiotherapeutic ultrasound has been used in physical therapy clinics; however, there remain some scientific issues regarding the bone-healing process. The objective of this study was to investigate the influence of low-intensity physiotherapeutic ultrasound on the initial stage of bone healing in rats. METHODS: Twenty-two male adult rats were assessed quantitatively and qualitatively using radiographic, biochemical, and histological analyses. Numerical simulations were also performed. Fractures in animals in the ultrasound group (n = 11) were treated with low-intensity ultrasound (pulsed mode, duty cycle 20 %) for 10 min daily at an intensity of 40 mW/cm(2) SATA (1.0 MHz) for 10 days. Fractures in animals in the control group (n = 11) were not treated. RESULTS: Alkaline phosphatase levels were non-significantly higher in the ultrasound group than in the control group in the time intervals considered (t(13) = 0.440; 95 % confidence interval (CI) −13.79 to 20.82; p = 0.67). Between-group serum calcium levels were also not significantly different (t(13) = −0.842; 95 % CI −0.48 to 0.21; p = 0.42). Finally, there were no significant differences in radiological scores between the two groups (U = 118; 95 % CI −1.99 to 1.99; p = 0.72). However, the diameter of the newly formed bone tissue was greater and more evident in the ultrasound group. CONCLUSIONS: Thirteen days after fracture, there was no significant between-group differences in bone-healing processes, although the increased alkaline phosphatase levels and diameter of new bone tissue need to be further investigated.