The Tridimensional Orthognathic Gauge: An External Intraoperative Device for the Verification of Virtual Surgical Planning

Virtual Surgical Planning is a game changing advance for Orthognathic surgery.  While this paradigm shift in treatment planning has the propensity to be more accurate and time efficient, the issue of accuracy cannot be wholly disregarded. Verification of the surgical treatment plan still presents a challenge to the surgeon, especially when he or she has elected to perform maxillary surgery first or the bite registration of the patient is inaccurate.

While mobile intraoperative CT scanners can be used to determine that the surgical treatment plan has been accurately accomplished, not all hospital facilities have this technology and not all surgeons are familiar with its use.  Performing the mandible first when operating both jaws helps to ensure the proposed surgical treatment plan by removing any preoperative or intraoperative discrepancies in condylar position.  However, once again, not all surgeons are proficient in this surgical protocol and not all combined maxillary/mandibular surgeries lend themselves to this technique.

The Tridimensional Orthognathic Gauge™ is an innovative, safe and technically simple appliance used as an external reference device for intraoperative verification of the virtual surgical treatment plan.  It has the advantage of low cost, no radiation exposure and significantly reduces the potential for returning the patient to the operating room when post operative CT scanning or clinical evaluation reveals an inaccurate result. The device consists of a halo apparatus with an adjustable insert for the attachment of vertical and horizontal rods that capture the position of the maxilla in three planes of space thereby transferring the natural head position of the patient from the computer generated models to the patient on the operating room table.  The adjustable vertical and horizontal rods measure in the same plane as the maxilla and mandible moves on the computer generated models during model surgery. This, then, accurately targets and verifies the position of the maxilla and the mandible at the end of the surgical case to document that the movement of the jaws at he time of surgery reflects the planned movement demonstrated in Virtual Surgical Plan.  A case will be presented illustrating the application and use of the device.  Pre and post-operative CT scanning measurements will be presented.

Bell, Byan R: Computer Planning and Intraoperative Navigation in Orthognathic Surgery. J Oral and Maxillofacial Surgery 69: 592-605 2011

Turvey, Timothy:  Sequencing of Two-Jaw Surgery: The Case for Operating on the Maxilla First. J Oral and Maxillofacial Surgery 69: 2225, 2011