IDEAS AND INNOVATIONS A Virtual Reality Tracking System for Distal Mandible Movement during Distraction Osteogenesis

Compared with traditional one-stage orthognathic surgery, distraction osteogenesis of the facial skeleton is a dynamic process.1 The distracted bone segment is gradually moved in three dimensions at a rate of 1 mm a day to achieve the desired position over the course of days or weeks. The current standard of imaging and recording bone movements during distraction is the static, one-dimensional plain film radiograph, or cephalogram.2,3 Not only are cephalogram series limited in representing the three-dimensional movements of distraction, they also require repeated radiation exposure, which is a concern in the pediatric population. The purpose of this study was to adapt the current technology in rigid-motion tracking and computer imaging previously reported by our group to develop a radiation-free virtual reality tracking system for mandible distraction. TECHNIQUE Tracking Device Design We previously reported the use of infrared diodes to track the intraoperative movement of bone fragments during complex multisegment craniofacial surgery.4,5 This technology, as well as the advances in three-dimensional rendering software, was adapted to design a splint-based tracker for mandible distraction osteogenesis. Three noncollinear, custom-made, infrared diodes were rigidly attached to an acrylic occlusal splint using an embedded locking-post interface. The machined interface allowed the same diode array to be interchanged repeatedly with the locking posts of different occlusal splints without changing the relationship of the array to the splint. This allowed the same diode array to be used for different patients. Tracking of the three diodes in each array defined both rotation and translation of the attached splint along the three-dimensional x, y, and z axes.4 One array was attached to the maxillary dentition of the subject by pressure fit of the occlusal splint, and a second was attached to the mandibular dentition (Fig. 1). The maxillary array served as a stable reference to the patient’s skull base, allowing tracking of relative movement of the mandible array. Because the maxillary array served as a stable reference of head position, the patient could move during the imaging process while the relative position of the mandible array was still being recorded. The three-dimensional position and movement of the arrays were tracked using a Flashpoint optical tracking camera (Image From the Craniofacial Center, Children’s Hospital and Regional Medical Center, and the Institute of Reconstructive Plastic Surgery, New York University Medical Center. Received for publication October 7, 2004; revised November 16, 2004. Presented at the 59th Annual Meeting of the American Cleft Palate-Craniofacial Association, in Seattle, Washington, May of 2002, and at the Third International Congress of Craniofacial and Maxillofacial Distraction, in Paris, France, June of 2001. Readers may also refer to the online version of the article at the Journal’s Web site (www.plasreconsurg.org) for additional materials. Copyright ©2006 by the American Society of Plastic Surgeons