A novel pulsed electromagnetic field promotes distraction osteogenesis via enhancing osteogenesis and angiogenesis in a rat model

Background: Distraction Osteogenesis (DO) is a widely used surgical procedure for limb lengthening, deformity correction, and management of segmental bone defects. However, delayed bone consolidation during DO remains an unsolved clinical problem, which significantly and negatively affects the quality of healing outcome. Pulsed electromagnetic field (PEMF) therapy has been shown to promote osteogenesis and exhibit beneficial effects on the management of delayed union and nonunion fractures. Thus, we hypothesize that PEMF could have beneficial effects on DO. Methods: In this study, specialized PEMF devices employing a novel high slew rate signal were used to firstly investigate effects of PEMF on osteogenesis of MSCs in vitro. MSCs cultured in osteogenic inductive medium treated with or without PEMF (3hrs/day) were subject to qPCR test, Alizarin Red S and ALP staining on day 7. Secondly, an in vivo study was undertaken using a DO model with fifty-six SD-rats randomly divided into two groups. The PEMF group received daily PEMF treatment, 3hr/day, and the control group received no treatment. Histology and IHC staining, radiographic exams, mu CT, and biomechanical tests were used to evaluate the quality of bone healing. Immunofluorescence staining and vessel perfusion following by mu CT were used to evaluate the effect of PEMF on angiogenesis. Results: Significantly more bone volume and mineral density were observed in the PEMF group compared with the control group, along with better biomechanical properties. Histological results showed that better quality callus formation with less cartilage in callus in PEMF group than control group. Immunofluorescence staining and vessel perfusion results showed that more blood vessels at both early and late stage of DO in PEMF group compared with control group. Conclusion: Our study showed that new high slew rate PEMF signal could promote osteogenesis and angiogenesis in a rat model of DO, which provides insight into the development of new noninvasive mean to accelerate bone formation in the DO process. The translation potential of this article: This study provides supporting evidence for the use of high slew rate PEMF signal to promote bone formation in DO.