A virtual reality system for bone fragment positioning in multisegment craniofacial surgical procedures

This article reports our clinical experience since 1994 with rigid- motion tracking of bone fragments during craniofacial surgical procedures, using a virtual reality approach. Three noncollinear infrared diodes are fixed to the skull base. A pointer is used to register anatomic features on the patient to those on the computerized tomography-based model of the patient within a computer work station. Three diodes are then attached to each fragment just before the osteotomy is completed. Rigid motions of the fragment are thus tracked and reported to the surgeon by using virtual reality techniques. Errors in fragment positioning are reported both graphically and numerically with respect to a precomputed optimum fragment position. This guidance system allows multisegment midface osteotomies to be performed more precisely. The main problems encountered so far have been devascularization-infection and difficulties in maintaining correct position during application of rigid fixation. Devascularization-infection problems have been addressed by minimizing surgical exposure of the bone. Soft- fixation plates and temporary Kirschner wire fixation have helped with intermediate positioning, but an intraoperative mechanical positioning device would be useful in the future.