Preliminary investigation of the biomechanics of internal fixation of sagittal split osteotomies with miniplates using a newly designed in vitro testing model

Purpose: This article reports a preliminary study undertaken to investigate the biomechanics of internal fixation systems for sagittal split ramus osteotomy of the mandible with advancement, using a newly designed 3-point bovine rib testing model. Materials and Methods: After 1 of 5 different miniplates internal fixation systems was placed, a vertical load was applied just below the superior border of sagittal split osteotomy gaps in bovine ribs positioned in a custom-made cradle using a compound cantilered bar device. Load/displacement data were gathered, and the mean elastic limits of the 5 miniplate designs were compared by using a 1-way analysis of variance (ANOVA) with Tukey multiple comparisons. Results: The elastic limit of the rigid fixation system was higher when using a curved plate design than with a straight plate design. Conclusion: The 3-point bovine rib model used in this study is an inexpensive, discriminating, and reproducible method for testing internal fixation systems on sagittal ramus osteotomies under conditions that more accurately represent the human mandible in function. © 2001 American Association of Oral and Maxillofacial Surgeons