High-rhythm automatic driver for bone traction: an experimental study in rabbits

The distractors currently used in clinics are activated manually by intermittent advancement. An automatic driver has been developed to attach to custom-made or commercially available distractors and activate advancement at a high rhythm of 8 steps per second. One 1.5-V lithium button battery is used as the power source to drive a step motor and the driving torque is transmitted to the distractor through a flexible shaft at a rate of 2 revolutions per day. This automatic driver was tested in 5 rabbits for mandibular lengthening. Osteotomy was performed on one side of the mandible and the custom-made distractor was adapted. After a latency period of 3 days. the automatic driver was attached to the distractor's arm and mandibular lengthening was activated. After 11 days of continuous distraction the automatic driver was detached from the distractor's arm. All the rabbits were euthanized after 4 weeks of consolidation. The distraction regenerates were analysed by plain radiography, micro-computerized tomography and histological examination. All 5 rabbits completed the experimental process and healed uneventfully. The mandibles were confirmed to have lengthened successfully and the distraction gap was filled with newly formed bone.