THE EFFECTS OF HIGH FREQUENCY, LOW MAGNITUDE MECHANICAL VIBRATIONS USING THE JUVENT DYNAMIC MOTION THERAPY DEVICE ON FRACTURE HEALING IN OESTROGEN DEFICIENT RODENT MODELS

Abstract

Although effects of mechanical stimulation with high frequency, low magnitude vibrations on bone mass and bone mineral density in animal and clinical studies have been proven effective, its effects on fracture healing is less well described.

20 Sham and 20 ovarectomised (Ovx) Sprague Dawley rats at 22 weeks of age, had intra-medullary k-wire fixation followed by controlled mid-shaft fractures.

The animals were divided into subgroups of 3 week Sham and Ovx treated and non-treated and 6 week Sham and Ovx treated and non-treated groups.

The treated animals were vibrated for 20mins daily on a DMT (dynamic motion therapy) platform which had a frequency of 30hz, 8-micron vertical displacement and 3g force, the non treated animals allowed to move freely. Xrays, DEXA studies, micro computed tomography, Histological analysis and Mechanical studies performed at the end point.

DMT treated animals had more bridging callus on radiographic and micro computed tomographic analysis compared to non-treated groups especially the OVX groups at 3 weeks compared to controls or Shams (using Image J software). DEXA studies showed increased bone mineral density and bone mineral content in the treated animals compared to the controls. Histological analysis showed increased callus and woven bone being laid down in the treated OVX groups.

In the 6-week groups, the treated OVX groups had healed, remodelled fractures compared to the non-treated groups or Sham controls where the fracture gaps were still visible. Although significance was not achieved on mechanical analysis due to small sample size, in the OVX non-operated femora group that were treated with DMT there were indications that they were stronger than the control counterparts.

High frequency low magnitude vibrations with the Juvent DMT device enhances fracture healing in oestrogen deficient models and this model could be used as a platform for clinical studies in future.