Three-dimensional Impact of orthognathic surgery on the upper airway and the apnea-hypopnea index.

The present PhD investigation is a compendium of five related publications broadening the current state-of-the art and long-term three-dimensional effects of orthognathic surgery on the upper airway (UA) and the sleep-related disorders, such as the Obstructive Sleep Apnea-hypopnea syndrome (OSA). This PhD project, coordinated by Prof. Dr. Federico Hernández-Alfaro and Dr.Adaia Valls-Ontañón at the Universitat Internacional de Catalunya, started in January 2018 as a three-year program, and was granted by the competitive predoctoral fellowship ID: FI_B200134 by the AGAUR (Agencia de Gestió d’ajudes Universitàries i d’investigació) of the Generalitat de Catalunya. With the support of the Secretariat of Universities and Research of the Generalitat de Catalunya and the European Social Fund. Globally, the aim of this whole investigation through a PhD project was to assess the 3D-clinical impact of OS, with regard to direction, magnitude and type of surgical movement, on the upper airway and the clinical improvement and/or cure of the OSA syndrome at long term. Thus, to verify the stability of OS surgical movements when maximizing the PAV and the minimum cross-sectional areas (mCSA), results were evaluated at three time points: pre-, immediate (1-month) and late postoperative (12-months follow-up) throughout the whole investigation. These three time points allowed the authors to be able to state firm conclusions on identifying both the surgical and volumetric gains and possible relapses (short term) and the stability of OS (long-term). Hence, to address the global and specific research purposes, the authors designed and implemented 5 different studies as follows though this rationale: - A systematic review (SR) to study the current the state-of-the art regarding the impact of MMA on the PAV and the AHI in the surgical treatment and definitive cure of OSA (Paper I). Assuming the scarce and lack of homogenic data on this topic: - A retrospective cohort study was performed to demonstrate the relevance of the relationship between the head positioning through the natural head position (NHP) and the Frankfort Horizontal (FH) planes patients with different dentofacial deformities (DFD) (i.e. maxilla/mandibular retrognathia and/or prognathism) and malocclusions (i.e. class I,II or III), thus demonstrating which horizontal plane should be properly executed when planning for OS (Paper II). - As there is no rigorous data regarding the AHI reduction and volumetric, linear and cross-sectional parameters gain after OS, a retrospective longitudinal study of consecutive patients was designed and performed to study the effect of maxillary and mandibular movements (isolated or jointly) on the PAV (nasopharynx, oropharynx, and hypopharynx) and the mCSA on a 3D basis using cone-beam computed tomography (CBCT). In turn, a proposed surgical planning protocol to maximize the UA was designed and validated through this investigation (PaperIII). - On the need of further studies to individualize a required magnitude and direction of surgery-induced movements to patients with DFD, a three case-series study was implemented to validate a protocol and algorithm for the surgical management of DFD in Down syndrome (DS) patients with OSA, when the main concerns are the narrowing of the UA, malocclusion, feeding and speech problems aside from aesthetics (Paper IV). - Finally, the results of a pilot study of an ongoing three arm prospective controlled clinical trial (CCT) (ClinicalTrials.gov ID NCT03796078 registration) are depicted in this PhD project to correlate the magnitude, type, and direction of these skeletal movements with the airway dimension gain or impairment at 12 months follow-up, to propose OS as the definitive and first line treatment armamentarium in selected patients to cure OSA (in terms of AHI and sleep patient-centered parameters) (Paper V).