The effect of ultrasound on the healing of muscle-pediculated bone graft in spinal fusion

Study Design. A rabbit model of posterolateral inter-transverse process spine arthrodesis with and without the application of low-intensity ultrasound was used. Objective. To determine the effects of low-intensity ultrasound on the healing of muscle-pediculated bone graft. Summary of Background Data. Earlier animal and clinical studies demonstrated the efficacy of low-intensity ultrasound stimulation in the acceleration of osteogenesis and fracture healing. This is the first study in which the beneficial effects of ultrasound on the healing of muscle-pediculated bone graft in spinal fusion have been assessed. Methods. In this study, 20 New Zealand rabbits were randomly assigned to two groups to undergo either spinal fusion using muscle-pedicle bone graft with ultrasound (ultrasound group) or muscle-pedicle bone graft without ultrasound (control group). Muscle-pediculated bone grafts were prepared from the posterosuperior iliac crest, erector spine-muscle, and internal and external oblique muscle. This graft was placed bilaterally between the L5 and L6 transverse processes. Ultrasound was performed 20 minutes per day over the rabbits' lumbar-spine. The rabbits were killed 6 weeks after surgery. The lumbar spines were evaluated radiologically, macroscopically, and histologically. Results. By macroscopic and radiologic findings, fusion was detected in 11 control group rabbits (55%) of the control group, and in 17 ultrasound group rabbits (85%). The fusion success rate for the rabbits treated with low-intensity ultrasound were statistically higher (P < 0,05) than that for the control group. Histologic specimens showed increased bone formation in the fusions exposed to ultrasound. Mature fusions were present in rabbits that received ultrasound. Conclusion. Low-intensity ultrasound in white rabbits increased the rate and quality of spinal fusion using muscle pediculated bone grafts.