OBJECTIVETo improve the design of the devices used for autoatic elasticity distraction osteogenesis, and to preliminarily testify their feasibility for clinical application.

METHODSThe internal automatic distraction devices were constructed by three parts, including sinusoid shape memory alloy distractor, reconstructive plate and mini-plate. The animal model of trifocal bone transport reconstruction of canine mandibular mentis was duplicated, in which a 6 cm mandibular mentis segment was removed and the transport disc was created by osteotomy in both ends of the mandibular defect. The plates were used for internal fixation and shape reconstruction of the mandible. They also served as transport distraction guidance for the elasticity distractor.

RESULTSThe new devices could complete bone transport as expected. Regenerated bone segments were formed in two months and both sides of the mandibular body were lengthened. Because of the narrow angle and obstruction from the thick soft tissues in the mentis area, the ultimate symphysis mentalis was not reconstructed.

CONCLUSIONThe design of the internal elasticity distraction devices showed potential feasibility for clinical practice. But further studies are still needed for better control of the strength and balance of distraction forces.