Continuous and intermittent bone distraction using a microhydraulic cylinder: an experimental study in minipigs

Distraction osteogenesis of the mandible is an option in the treatment of mandibular hypoplasia. Today, only intermittent distraction devices are available for clinical application. The aim of this study in minipigs was to evaluate continuous bone distra ction using a microhydraulic cylinder. After a seven-day interval, continuous or intermittent distraction of 1.5mm/day was established for 10 days. Immediately after active distraction, two animals and 20 days later the other four animals were killed and radiographs taken. The mandible was then removed en bloc and the distracted bone examined histologically. Inter mittent distraction forces of up to 2500kPa were necessary to move the cylindersʹ piston. The pressure needed for continuous distraction was considerably lower (1200–1300kPa). While the specific histological structure of the varying zones in the distraction gap was similar after continuous and intermittent distraction, bone healing was accelerated after continuous distraction as shown by ultrasonography and scanning elec tron microscopy.