Incremental Maxillomandibular Advancement: The Relationship Between Skeletal Advancement and Airway Volume

Abstract

IntroductionObstructive sleep apnea (OSA) is characterized by repetitive episodes of supra‐laryngeal airway collapse during sleep, causing increased airflow resistance and reduced respiration. Obstruction and reduced volume mainly occurs in the retropalatal (RPS) and/or retroglossal space (RGS). The most effective surgical treatment (save tracheostomy) is maxillomandibular advancement (MMA). During MMA, the skeletal framework is modified, thereby reducing airway collapse upon inspiration. A clear mechanistic understanding of MMA surgery describing airway dimensions and resulting volumetric increases does not yet exist. The primary objective of the study was to define volume changes during incremental MMA. The secondary objective was to measure where maximal airway tissue movement occurs.MethodsAn oral surgeon performed MMA on three fresh cadaveric heads (n=3). The mandible and maxilla were advanced by four implanted distraction devices (KLS Martin Inc.). The devices were bilaterally advanced by 2mm increments to 14mm to encompass the full range of clinical advancements. Computerized tomography (CT) scans, (0.6 mm isotropic, Siemens, O‐arm), were taken at baseline (no advancement) and each advancement level (2, 4, 6, 8, 10, 12, 14mm). For the primary objective, total airway volume and linear anteroposterior (AP) and lateral (LAT) 2D dimensions of the RPS and RGS were analyzed at each incremental advancement using Amira™ (Thermo Fisher Scientific). To address the secondary objective, translation of airway tissues, radiopaque microbeads (800 μm, Ortech) were implanted at borders of the RPS and RGS using a syringe and endoscope and their movement was tracked through each advancement.ResultsDuring incremental MMA, airway volume increased at each increment compared to baseline. For 0–2, 2–4 & 4–6mm, normalized volume increases were incrementally larger with each advancement [mean0–2mm = 20.3 ± 22.8%; mean2–4mm = 34.9 ± 13.8%; mean4–6mm = 62.4 ± 17.2%]. Consistent volumetric increases occurred during the advancements from 6mm to 10mm [mean6–8mm = 50.8 ± 27.0%; mean8–10mm = 45.6 ± 28.7%]. Preliminary analysis (n=1) shows that during early MMA (2mm–6mm), lateral dimensions increased at a greater magnitude compared to later advancements (8–14mm). Microbead migration supports these findings while highlighting airway wall movement.ConclusionWhile volumetric increases occur at each advancement, the greatest relative change occurs at the advancement from 4–6mm. Relative volumetric increases show a consistent increase in airway volume with each incremental advancement throughout 6–10mm. Lateral wall widening is the chief mechanism for early volume change, at advancements between 2–6mm, while AP dimensions are affected at 8–14mm advancements. The relationships between 2D (AP/LAT) changes and 3D (volume) demonstrate that volume change in initial advancements are primarily due to lateral enlargement. Depending on OSA severity, clinicians may exploit these relationships when performing MMA.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.