Cumulative effect of low-level laser therapy and low-intensity pulsed ultrasound on bone repair in rats

Many studies have assessed the effects of either low-level laser therapy (LLLT) or low-intensity pulsed ultrasound (LIPUS) on bone repair; however, an evaluation of the combination of these modalities (LLLT + LIPUS) has not yet been considered. The aim of this study was to demonstrate the effects of LLLT + LIPUS on bone repair. Male Wistar rats (n = 128; four groups of 32) were used; the animals underwent a partial tibial bone osteotomy. One group had the osteotomized limb treated with LLLT, the second group with LIPUS, and the third group with the combined treatment protocols of the LLLT and LIPUS groups; the fourth group received no further treatment (control). Each group was divided into two subgroups for assessment at two different time-points, 14 and 21 days. After the completion of treatment rats were sacrificed and the tibias submitted to a three-point bending test or to histomorphometric analysis. Histological evaluation showed increased bone trabeculae, increased vascularization, and decreased inflammation in the LLLT + LIPUS group. Mechanical evaluation revealed increased biomechanical properties including maximum force, maximum stress, and stiffness, in the LLLT + LIPUS group. Combined LLLT + LIPUS treatment enhanced bone healing both histologically and mechanically, shortening the length of the treatment period, when compared to treatment with LLLT or LIPUS alone.