Force level and strain patterns during bilateral mandibular osteodistraction

Purpose: Recent reports have demonstrated that device orientation is import ant during mandibular distraction osteogenesis. The purpose of this study w as to evaluate the force level and strain patterns on the mandible during b ilateral osteodistraction with devices oriented either parallel to the body of the mandible or parallel to the sagittal axis of distraction. Materials and Methods: Five unembalmed human cadaver mandibles were placed in a specially designed apparatus for stabilization of the proximal segment s during distraction. A force transducer was attached to the lateral aspect of the inferior ramus, and strain gauges were attached to the mandibular b one segments proximal and distal to the distraction device. Lateral force a nd bone strains were then measured at 5 and 10 mm of distraction. Osteodist raction proceeded first with the devices placed parallel to the mandibular body, then parallel to the axis of distraction. Results: Significantly greater lateral forces were seen when the devices we re oriented parallel to the mandibular body. With this device orientation, increased tensile strains were seen at the labial symphysis and medial ramu s, and increased compressive strains were found at the lingual symphysis an d lateral ramus, However, when the devices were oriented parallel to the ax is of distraction, the forces and strains were not detected, Conclusions: The results suggest that device orientation has important biom echanical effects on lateral forces and strain patterns during mandibular o steodistraction.