Purpose: During the past year our focus has been on the evaluation of patients who have had orthognathic (mandibular) surgery. We have specifically chosen to focus on anatomic relationships between the hyoid bone and the mandible during swallowing. Since the muscles needed to execute swallowing and support the base of the tongue are attached to the hyoid and the mandible, any surgical changes in the mandible could affect the swallow. We used both ultrasound and cephalometric X-ray tracings to quantify the relationship between the mandible and hyoid activity. Subjects and Methods: Fourteen subjects, referred to NIDR for orthognathic surgery, were evaluated in 3,6, and 12 month intervals. Eight patients had mandible advancement procedures and 6 had mandibular setback procedures. Ultrasound measurements made by frame-by-frame analysis of real-time video studies were used to study hyoid motion during swallowing. The maximal anterior hyoid motion was measured on both stimulated and unstimulated swallows. Two tailed t-tests for repeated measures were used to compare swallowing changes before and after surgery. Findings: We determined from our ultrasound data that there was a significant relationship between the amount of mandible adjustment post surgery and the time needed to complete a swallow. We found a consistent pattern of progressive incremental changes in swallowing function. These changes in the duration of the swallow were relative to the amount of surgical displacement of the mandible. That is, subjects with the greatest post-surgical anatomic change had the longest swallowing times and made the greatest improvements after surgery.
