Low-intensity pulsed ultrasound promotes spinal fusion by regulating macrophage polarization.

•Spinal fusion is considered the gold standard procedure for treating spinal degeneration, tumors, and trauma.•We demonstrated that LIPUS promotes spinal fusion and stimulates the transition of macrophage expression from M1 to M2.•We demonstrated that LIPUS promotes and increase of spine bone density.•LIPUS promotes the polarization of Raw264.7 cells and bone marrow-derived macrophages to M2 in vitro.•LIPUS increases the expression of anti-inflammation genes, like IL-4.