Table 1.

Mechanisms of action of electrical stimulation technologies

Study	Technique	Model	Results
Fredericks et al. [24]	DC	Rabbit posterolateral spinal fusion	Upregulates BMP-2, -6, and -7 mRNA
Bodamyali et al. [5]	DC	Calvarial organ culture	↓ Oxygen concentration, ↑ pH and produces hydrogen peroxide.↓ oxygen concentration: ↑osteoblastic activity [12].↑ pH: ↑ osteoblastic activity and ↓ osteoclastic activity.Hydrogen peroxide: stimulates macrophages to produce VEGF [15]
Smith et al. [61]	PEMF	Rat cremaster muscle	Elicits arteriolar vasodilation
Ryaby et al. [58]	CMF	Rat fracture callus culture	↑ IGF-II levels
Fitzsimmons et al. [20, 21]	CMF	Human osteosarcoma-derived osteoblast-like cell culture	↑ IGF-II levels and receptors
Brighton et al. [11]	CMF	Mouse osteoblastic cell-line MC3T3-E1	↑ Cytosolic Ca2+ concentration from Ca2+ release from intracellular stores
Fredericks et al. [23]	CC	Rabbit posterolateral spinal fusion	Upregulates BMP-2, -4, -6, -7, TGF-β1, FGF-2, and VEGF mRNA (preliminary data)
Lorich et al. [45]	CC	Rat calvarial bone cell culture and mouse osteoblastic cell-line MC3T3-E1	↑ PGE2. ↑ cytosolic Ca2+ concentration from transmembrane Ca2+ translocation via voltage-gated calcium channels
Zhuang et al. [69]	CC	Mouse osteoblastic cell-line MC3T3-E1	↑ TGF-β1 mRNA

DC direct current, PEMF pulsed electromagnetic field, CMF combined magnetic field, CC capacitive coupling,↑ increases, ↓ decreases, BMP bone morphogenetic protein, VEGF vascular endothelial growth factor, IGF insulin-like growth factor, TGF transforming growth factor, FGF fibroblast growth factor, PGE₂ prostaglandin E₂, Ca²⁺ calcium ion