How much do you change? An evaluation of the anatomical consequences of maxillomandibular advancement surgery
Authors: Ly Cathy Ong , Rubin Benjamin D. , Tassi Ali D. , Wilson Timothy D. 
Published: June 2021

BackgroundObstructive sleep apnea (OSA) is a chronic sleep disorder characterized by recurrent collapse of the upper airway causing complete or partial blockage during sleep. Severity of sleep apnea and surgical success rate of MMA surgery is often characterized by the apnea‐hypopnea index (AHI) which evaluates these events per hour. Maxillomandibular advancement surgery (MMA) is an effective intervention for OSA with a surgical success rate exceeding 85%. However, details regarding which anatomical features are changed by MMA within the pharyngeal airway remain unclear. Previous studies demonstrate that the velopharyngeal region (VPR) posterior to the soft palate, has the greatest obstruction potential during OSA. Accordingly, it is hypothesized that MMA surgery will specifically alter VPR, increasing anterior to posterior distance in the velopharynx.MethodsTo address the hypothesis, a retrospective analysis of anterior to posterior distances of the VPR were measured in cephalometric x‐rays of OSA patients before and after MMA. The experimental sample consisted of twenty‐two patients (11 males and 11 females) with a mean age of 44 ± 13.9 years. Three key measurements were obtained by lateral cephalometric analysis consisting of two velopharyngeal anteroposterior lengths (VAPL1,2) and the minimal velopharyngeal anteroposterior length (VAPLM). All distances were measured electronically (Osirix, 9.0.1) and parallel to the occlusal plane (OP), VAPL2 were measured directly on the OP, and VAPL1 were measured 10 mm above the OP.ResultsApnea‐hyponea index prior to MMA was considered in the severe range with a mean of 48 ± 31 events per hour. Following MMA surgery, mean AHI was reduced to 14 ± 15 and considered to be in the mild range of OSA. Mean change in distances among the three variables VAPL1, VAPL2, and VAPLM, were 1.6 ± 5.4 mm, 3.9 ± 5.0 mm and 4.7 ± 3.0 mm, respectively. Average VAPL1 pre‐MMA surgery was 13.5 ± 4.5 mm and subsequently was 15.1 ± 4.2 mm post‐MMA surgery. Average VAPL2 pre‐MMA and post MMA increased from 8.8 ± 3.1 mm to 12.7 ± 4.3 mm, respectively. The mean VAPLM after MMA surgery increased significantly to 10.6 ± 3.6 mm compared to before surgery, 5.9 ± 2.6 mm, (t21 = 7.37, p < 0.001). Overall, there was a strong correlation between mean VAPL1 and VAPL2 (r = 0.835), (t20 = 4.55, p < 0.001) and between VAPL2 and VAPLM (r = 0.738), (t20 = 2.81, p < 0.01).ConclusionMaxillomandibular advancement surgery does significantly alter the minimal velopharyngeal region and decreases AHI. Based on the results of this experiment, the greatest change in unidimensional airway lengths occurs at the minimal VPR. This enhances our understanding by identifying intrinsic anatomical airway changes arising from MMA and may be useful for clinicians and surgeons treating OSA. More precise measurements of volume will further explore how regional airway anatomy is altered during MMA. In a pilot study, computed tomography (CT) scan analysis of incremental MMA on a cadaver demonstrates the ability to correlate regional linear measurements and relate them to volumetric outcomes. Future directions will explore volumetric alteration and pharyngeal tissue distortion in cadaveric patients undergoing incremental MMA.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.