Effect of pulsed electromagnetic fields (PEMF) on late-phase osteotomy gap healing in a canine tibial model

Abstract

The effects of a pulsed electromagnetic field (PEMF) on late bone healing phases using an osteotomy gap model in the canine mid-tibia were investigated. A transverse mid-diaphyseal tibial osteotomy with a 2-mm gap was performed unilaterally in 12 adult mixed-breed dogs and stabilized with external fixation. Animals in the variable group ( n=6) were treated with PEMF for 1 h daily starting 4 weeks after surgery for a total of 8 weeks, whereas no stimulation signal was generated in the control group ( n=6). Functional load-bearing and radiographic assessments were conducted time-sequentially until euthanasia 12 weeks after surgery. Torsional tests and an analysis of undecalcified histology were performed on the retrieved mid-tibial diaphysis containing the osteotomy site. In the PEMF group, load-bearing of the operated limb recovered earlier when compared to the control group ( p<0.05). Load-bearing in the PEMF group at 8 weeks was greater than in the control group ( p<0.02). The periosteal callus area increased following surgery at 6 weeks ( p<0.05) and thereafter ( p<0.01) in the PEMF group, while a significant increase was observed at 8 and 10 weeks after surgery ( p<0.05) in the control group. Both the normalized maximum torque and torsional stiffness of the PEMF group were significantly greater than those of the control group ( p<0.04 and p<0.007, respectively). Histomorphometric analyses revealed greater new-bone formation ( p<0.05) in the osteotomy gap tissue and increased mineral apposition rate ( p<0.04) and decreased porosity in the cortex adjacent to the osteotomy line ( p<0.02) in the PEMF group. PEMF stimulation of 1 h per day for 8 weeks provided faster recovery of load-bearing, a significant increase in new bone formation, and a higher mechanical strength of the healing mid-tibial osteotomy. This study revealed enhancing effects of PEMF on callus formation and maturation in the late-phase of bone healing.