Rat mandibular distraction osteogenesis: Latency, rate, and rhythm determine the adaptive response

Distraction osteogenesis is a well-established technique of endogenous tiss ue engineering. The biomechanical factors thought to affect the quality of the distraction regenerate include the latency, rate, rhythm, and consolida tion period. In an effort to understand the impact of these parameters on r egenerate bone formation, this study was designed to decipher the most adap tive response in a rat model of mandibular distraction osteogenesis. Ninety -six adult Sprague-Dawley rats were divided into 16 subgroups (n = 6 per su bgroup) based on variations in the distraction parameters (i.e., latency, r ate, and rhythm). After a 28-day consolidation period, the mandibles were h arvested, decalcified, and sectioned. A standardized histologic ranking sys tem was used to evaluate the effect of each protocol on the adaptive respon se of the regenerate bone. In this study, we have demonstrated that the lat ency period dramatically affects the success of distraction osteogenesis. F urthermore, distraction rates up to 0.50 mm per day stimulated excellent re generate bone formation, whereas greater distraction rates produced a fibro us union. Finally, higher frequency distraction (i.e., increased rhythm) ap peared to accelerate regenerate bone formation. We believe that defining th e critical parameters of this model will improve future analysis of gene ex pression during rat mandibular distraction osteogenesis and may facilitate the development of biologically based strategies designed to enhance regene rate bone formation.