title: 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.
authors.affiliation: Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, MD 21205-2196, USA.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Inoue
authors.forename: Isao
authors.initials: I
authors.lastname: Ohnishi
authors.forename: Dongan
authors.initials: D
authors.lastname: Chen
authors.forename: Luke W
authors.initials: LW
authors.lastname: Deitz
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Schwardt
authors.forename: Edmund Y S
authors.initials: EY
authors.lastname: Chao
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004285:Dogs; D004599:Electric Stimulation Therapy; D004574:Electromagnetic Fields; D017102:Fracture Healing; D008297:Male; D010027:Osteotomy; D011859:Radiography; D013314:Stress, Mechanical; D013977:Tibia / Q000000981:diagnostic imaging / Q000293:injuries* / Q000502:physiology; D013997:Time Factors; D019415:Torque; D016896:Treatment Outcome; D016474:Weight-Bearing / Q000502:physiology