Motion observed across maxillary continuity defects stabilized with plates and screws

The stability of fixation obtained with internal fixation devices (plates and screws) under functional loading of maxillary continuity defects was studied using fresh cadaver skulls. Micromotion (deformation) was recorded in the model across the level of the LeFort I osteotomies even when fixation was thought to be grossly stable. Deformation in this biologically static model proved to be mostly elastic in nature, and the amount of deformation in each skull appeared to be predictable from the average stability of all screws used in each plate. Such motion in viable bone could lead to permanent deformation due to resorption and remodeling of bone around the screws if initial overall fixation stability is tenuous. The results suggest that the term "rigid" is inappropriately used to describe plate and screw fixation of maxillary continuity defects.