A 3D Analysis of Mandibular Plating Strategies in Oromandibular Reconstruction.

Overview

Reconstruction of the mandible commonly employs the use of metal plates to provide a framework for placement of bone grafts. The standard approach to reconstruction involves bending these plates to the mandible intraoperatively. A novel technique involves bending plates to three dimensional (3D) printed models of the mandible prior to surgery. No study has performed a quantitative analysis and comparison of these two different strategies. The purpose of this study is to compare reconstructive plating strategies (preoperative versus intraoperative bending) for mandibular reconstruction using 3D quantitative analysis. Preoperative diagnostic CT scans of the head/neck of 20 patients scheduled to undergo mandibular reconstruction will be obtained and imported into 3D modeling software. A computer based 3D reconstructed mandible will be printed. Simulated reconstruction will be replicated by contouring mandibular reconstruction plates to each model. The plates will be marked, sterilized and brought to the operating room on the day of surgery. Each patient will be randomized to either preoperative (n=10) or intraoperative (n=10) plate bending groups. The group will be revealed to the primary surgeon on the day of surgery and the patient will either be fit with the plate bent preoperatively or will undergo fitting with a plate bent intraoperatively. Following reconstruction of the mandible, the patient will undergo intraoperative cone beam scanning. Using scans performed pre- and post-mandibular reconstruction, the 3D simulated mandibles will be compared based on the position of the mandibular condyle within the Temporomandibular Joint. In addition, the percentage of surface area contact between the plate and mandible and the postoperative occlusion attained will be determined and compared between groups. It is expected that the preformed plates will have improved contact surface area, and better achieve pre-reconstruction occlusion when compared to plates bent intraoperatively.

Patients will be identified through attendance at the Wharton Head and Neck Clinic at Princess Margaret Hospital or attendance at the Toronto General Hospital Otolaryngology - Head \& Neck Surgery clinic as requiring resection of mandibular pathology and subsequent reconstruction with bony free flap. Chart review (electronic) of these patients will be performed to obtain demographic information and factors such as tumor type, site, stage and prior treatment. Data will be obtained from CT scans to create 3D models, including anatomic parameters required for 3D printing of the mandible. Following reconstruction, a number of variables will be collected (i.e. position of the mandibular condyle within the temporomandibular joint, percentage of surface area contact between the plate and bone, type of occlusion/bite and degree of conformance). All of this data will be stored in a password protected Excel spreadsheet located on a secure University Health Network computer. Twenty participants will be enrolled into this study and randomized to one of two groups: intraoperative plate bending (n=10) or preoperative plate bending (n=10) using a 3D printed model. While the participant can be blinded to the strategy that will be pursued, the surgeon performing the reconstruction will not be blinded.