###### Abstract  
Distraction Osteogenesis (DO) revolutionizes bone lengthening without donor sites, which is crucial in maxillofacial reconstruction (MRA). Manual DO devices are standard, but continuous DO devices promise faster treatments and better outcomes. Current continuous distractors lack ideal MRA due to size, force generation, and power source limitations. This study introduces a passive distractor system for continuous DO in MRA, aiming to bridge existing gaps and provide an ideal solution for human MRA use. It utilizes a miniaturized mechanism powered by a passive energy source, eliminating the need for active power. Advanced manufacturing methods enable the reduction of device size while hydraulic systems ensure controlled and smooth movement. The system includes a proximal bone fixture, movable distractor components, and passive drive means for distraction force application. Results show promising potential to address existing limitations. By utilizing passive energy for continuous force generation, the device size is reduced, and the need for force transition mechanisms is minimized. This innovative system and method offer an ideal treatment environment for MRA in humans. Further research and clinical evaluation are essential to validate its efficacy and safety in clinical practice. distraction osteogenesis; continuous distractor; bone reconstruction; tissue regeneration; surgical innovation; medical device +
Footnote †: journal: Medical Reconstruction  
techniques), prosthetics (both metallic and non-metallic), and vascular flaps (including local, regional, and distant-free flaps). These techniques collectively offer a comprehensive approach to reconstructive procedures in the field [11]. Figure 2 illustrates the method of DO in MRA. A standard DO protocol in MRA encompasses several phases: osteotomy and installation of the distractor; a latency phase where the distractor remains inert; an activation phase where the distractor initiates movement, gradually shifting the bone segment (BS) towards its final position in a linear axis; a consolidation phase during which the distractor remains inactive, fostering tissue regeneration and consolidation. Following this, the device is removed, marking the conclusion of the reconstruction procedure. Throughout the activation phase, the distractor exerts a smooth distraction force (DF), facilitating the incremental movement of the BS. The conventional method of manual distractors involves an operator manually adjusting the DF to activate and move the BS in DO treatment. Two types of manual distractors exist: intra-oral and extra-oral. However, the use of extra-oral distractors has led to severe complications, including nerve injuries, scarring, infection, and patient discomfort, limiting their application. In contrast, intra-oral distractors have shown more favorable results. Both intra- and extra-oral manual distractors involve daily activations, with a distraction accuracy of 0.5 to 1 mm. Nonetheless, they suffer from limitations such as unstable move  
Figure 1: The place of DO in MRA [11]. Figure 2: Distraction osteogenesis standard protocol [12]. ment, low accuracy, a low distraction rate (DR), and infrequent adjustments, resulting in lengthy treatment periods and patient discomfort [8; 13; 14; 15; 16; 17]. Recent research has indicated that increasing the distraction rhythm during the activation phase of DO treatment can lead to improved bone regeneration quality, better consolidation conditions, and shorter treatment durations [18; 19; 20; 21; 22]. This discovery has spurred interest in the development of automatic continuous distraction osteogenesis (ACDO) devices [10; 15; 23]. ACDO devices automate the process, ensuring a continuous DF and controlled movement of the BS along a predetermined path. Compared to manual distractors, ACDO devices offer significantly higher distraction accuracy, enabling a higher DR and rhythm. These advancements lead to shorter treatment periods, reduced patient discomfort, and improved treatment outcomes.