0R3: THE EFFECT OF LOW-MAGNITUDE, HIGH-FREQUENCY VIBRATIONS ON REGENERATE BONE IN DISTRACTION OSTEOGENESIS

Abstract

Distraction osteogenesis (DO) is useful for bone lengthening and deformity correction. Unfortunately, this often requires prolonged use of an external fixator with concomitant morbidities. This study investigates whether low-magnitude, high-intensity vibrations (Dynamic Motion Therapy, DMT) can accelerate maturation of regenerate bone in DO, thus reducing the duration of external fixation. 28 NZ White Rabbits underwent a right mid-tibial osteotomy with application of an Orthofix M-103 fixator (Orthofix, Busselengo, Italy). Distraction commenced on day 3 at 0.5 mm every 12 hours for 12 days. All animals were sacrificed on day 45. Animals were randomly assigned into 4 groups:

1. control group;

2. DMT only during distraction period;

3. DMT only during consolidation period;

4. DMT during distraction and consolidation periods.

DMT was applied with the Juvent platform (Juvent, Somerset, NJ) for 10 minutes/day. X-ray and CT scans were taken prior to mechanical testing. All specimens were processed for histology. X-rays and CT scans showed evidence of cortical remodelling and re-establishment of the medullary canal in animals treated with DMT (groups 2, 3 and 4). This was most pronounced in animals treated during the distraction and consolidation phases (group 4). Regenerate bone in the control group (group 1) was more disorganised, with a delayed union evident in 1 animal. Group 1 achieved peak torque and stiffness values of 70% and 50% of the contralateral (unoperated) tibia respectively. No significant difference was seen in peak torque and stiffness between groups 2, 3, and 4, however each was significantly higher than group 1 (P< 0.05). H& E staining revealed less porosity in the newly formed cortical bone and a more defined medullary canal in animals treated with DMT than in the control group. Low-magnitude, high-intensity vibrations appear to accelerate cortical remodelling and reestablishment of a medullary canal. Regenerate bone in animals treated with DMT was also mechanically superior. The timing of DMT therapy did not appear to be important. Further studies are required to determine the optimal timing and duration of DMT therapy.