An Application Study Of A Novel Internal Bidimensional Distractor

Distraction osteogenesis has been widely used in the treatment of craniomaxillofacial deformities since McCarthy first lengthened human mandibles by gradual distraction in 1992. Mandibular retrognathia is a common type of maxillomandibular deformities with manifestation of bone mass inadequacy in mandibular ramus and/or body. If treated with DO, the patients need have their mandibles lengthened both vertically and horizontally. However, existed DO devices for mandibular elongation are mostly linear, which only lengthen bone in one direction, so a novel internal bidimensional distractor was invented by our team in hope to elongate mandibular ramus and body simultaneously and provide an alternative solution for mandibular retrognathia.The application study was divided into three parts.Part 1: Design of a novel internal bidimensional distractor and an experiment in vitro.A novel internal bidimensional distractor for mandibular elongation was designed in cooperation with Xi'an Zhongbang Titanium Biomaterial Ltd. Co. The distracor is composed of two targeting bodies with a 15-millimeter working length for each, two mobile wings which act to move along targeting body as well as to fix the device, a double-united-immobile wing connecting the two targeting bodies to make an angle of about 120°that is similar to that of the gonion of human mandible, and two swivel holders which cause 0.4 millimeter slide forward within one turning. An experiment in vitro was performed at first. Osteotomy was made at the mandibular angle, and the two mobile wings were fixed on the mandibular ramus and body; turning the swivel holders could make the two mobile wings dock onto the end of the targeting body, the mandibular ramus and body got lengthened simultaneously, and the distracted gap was of a curved contour.Part 2: Establishing animal models of mandibular bidimensional distraction osteogenesis on goats by using a novel internal bidimensional distractor.Animal models of bidimensional DO were established afterwards on four goats, all the goats were X-rayed during the distraction phase and consolidation phase, and histological sections were collected at the end of distraction phase and the end of an eight-week consolidation. The outcome indicated that the regenerated bone was restored in the distracted gap, and both the radiographs and the histological sections demonstrated that after eight weeks of consolidation the regenerated bone tissue was similar to normal. A conclusion might be drawn that the novel distractor could complete bidimensional DO of mandible on goat and might have a promising prospect for clinical treatment of mandibular retrognathia.Part 3: Correction of mandibular retrognathia by using a novel internal bidimensional distractor.Based on the success of animal experiment, two patients suffering from mandibular retrognathia were studied. The two patients both underwent distraction phase at the activated rate of 0.5mm/d after a seven-day latent phase, and activated distraction stopped when the wanted mandibular contour was achieved, Both the patients got much facial alleviation as planed without complications after a three-month consolidation.Clinical success indicated that the novel bidimensional distractor could perform mandibular bidimensional DO and might provide an alternative solution for mandibular retrognathia.