Computational fluid dynamics analysis for the preoperative prediction of airway changes after maxillomandibular advancement surgery

Abstract

Maxillomandibular advancement surgery is useful for treatment of sleep apnea. However, preoperative analysis and evaluation to facilitate decision-making regarding the direction and distance of maxillomandibular movement has primarily consisted of morphological analysis; physiological function is not evaluated. To improve preoperative prediction, this study used fluid simulation to investigate the characteristics and effects of airway changes associated with maxillomandibular movement. A one-dimensional model with general applicability was thus developed. Actual measurements of flow in patients were used in this fluid simulation, thus achieving an analysis closer to clinical conditions. The simulation results were qualitatively consistent with the actual measurements, which confirmed the usefulness of the simulation. In addition, the results of the one-dimensional model were within the error ranges of the actual measurements. The present results establish a foundation for using accumulating preoperative measurement data for more-precise prediction of postoperative outcomes.

A preoperative predictive study of advantages of airway changes after maxillomandibular advancement surgery using computational fluid dynamics analysis

“…Our previous studies [ 19 , 20 , 23 ] demonstrated that CFD simulations could largely reproduce patients’ actual respiratory flow dynamics. This study suggests that CFD can be used to analyze respiration air flows in areas that cannot be measured by rhinomanometric methods, i.e.…”

“…CT scans of the nose, sinuses, and upper airway of participants were obtained with 1-mm-thick 3D-CT image slices preoperatively and at the 1-year postoperative follow-up; 3D-CT scans were evaluated using the same methodology as in our previous study [ 19 ]. To measure airway geometries of all cases in the following condition, X-ray CT (X-CT) scanning measurements were conducted.…”

“…To reproduce inlet airflows accurately, coming from outside the external naris and into the nasal airway, the calculation mesh was accurately formed from the space in front of the face to the nasal cavities and pharynx airway. Since our previous CFD studies showed that small, but non-negligible, swirling flows existed in the paranasal sinuses, the CFD meshes for this study also included the paranasal sinuses [ 16 , 19 ]. Furthermore, the surrounding four plane surfaces of box-like spaces before the face surface were defined as slip solid surfaces because they were used only for limiting the CFD domain to prevent unnecessary calculations of very low-speed flow far from the nostrils [ 14 ].…”

“…The first process, as shown in Fig 3 , is a CFD analysis using preoperative measurement data from clinical practice. The CFD methodology is described above; its accuracy has been proven in a previous paper [ 19 ]. Since MMA+GA surgery may enlarge the cross-sections near the exit of the nasal airway, nasopharynx, and oropharynx, both preoperative and postoperative rhinomanometric evaluations in the same patient can be used to assess improvements in nasal patency following surgery.…”

“…CFD analysis may help to clarify the pathogenesis of OSA [ 16 ] and can be combined with the geometry of the pharyngeal airway, both before and after treatment, to calculate reductions in pressure and flow resistance [ 18 ]. Moreover, our previous study evaluated MMA-associated airway changes using CFD and rhinomanometry to simulate fluid dynamics in inhalation, and we found that simulated projections were comparable to actual measurements [ 19 ]. In this study, we aimed to develop a simulation approach for predicting MMA-induced airway changes using CFD.…”