The effect of rim mandibulectomy configuration and residual segment size on postoperative fracture risk: An in vitro study

Purpose: This study evaluated the effect that size and shape of rim mandibulectomy has on residual mandibular strength and resistance to fracture, with the ultimate goal of improving the use of this technique and establishing a threshold for the application of prophylactic internal fixation. Materials and Methods: Ten partially dentate dry human mandibles were mounted in a manner replicating the pterygomasseteric musculature. Unilateral midbody serial rim excisions of increasing size were completed in both a curvilinear and right-angled fashion, and physiologic forces were gradually applied to a level of residual segment fracture. Dimensional measurements were taken of the specimens before and after fracture to understand which factors contributed to failure. Results: On average, a curvilinear excision configuration resisted higher occlusal forces with a smaller residual segment than did the right-angled excision configuration. A residual inferior border thickness of Less than 9 mm could not predictably withstand force application within the limits of the experimental model. Conclusion: These data support the use of a curvilinear excision configuration for rim mandibulectomies. Reproducibility of the location of the residual segment failure and other consistent residual segment dimensional information have implications regarding the limitations of this technique, beyond which the use of adjunctive support in the form of maxillomandibular fixation or prophylactic internal fixation may be indicated. (C) 2001 American Association of Oral and Maxillofacial Surgeons.