Pharyngeal airway changes after mono- and bimaxillary surgery in skeletal class III patients: Cone-beam computed tomography evaluation

Evaluation of Minimum Axial Airway Area and Airway Volume in Orthognathic Surgery Patients: A Retrospective Study

The aim of this study was to compare preoperative and postoperative linear, planar, and volumetric measurements in the pharyngeal airway in orthognathic surgery patients. Preoperative and postoperative cone beam computed tomography (CBCT) images of 60 patients, who underwent maxillary advancement with mandibular setback (Group I, n=25) and bimaxillary advancement (Group II, n=35), were compared. The airway was divided into 3 regions as nasopharynx, oropharynx, and hypopharynx. Linear and planar measurements were made on the reference sections of each region. The minimum axial airway area, the volume of 3 regions, and total airway volume were also measured. Regarding the linear, planar, and volumetric measurements, while there was a statistically significant increase in the measurements for all three regions in Group II, in Group I only the measurements in the nasopharyngeal region demonstrated a statistically significant increase postoperatively (P<0.05). There was an increase in minimum axial airway areas in both groups; however, it was only statistically significant in Group II (P<0.05). There was a statistically significant increase in total airway volumes in both groups (P<0.05). A positive and good correlation was found between the percent increase in the minimum axial area and the percent increase in the total volume (P<0.05). While bimaxillary advancement surgery results in a significant increase in the pharyngeal airway, mandibular setback with maxillary advancement caused an increase in the total airway. Changes that may occur in the airway should be considered while planning orthognathic surgery.

Addressing Acromegaly-Related Malocclusion With Surgery-First Orthognathic Surgery: A Clinical Case Report

Angle's class III malocclusions are characterized by the anterior positioning of the mandible in relation to the maxilla. The discrepancy can be caused by an anterior deficiency of the maxilla, excessive mandibular prognathism, or a combination of both. Acromegaly is a dysfunction caused by the excessive production of growth hormone (GH), which leads to systemic changes and orofacial manifestations. In acromegaly caused by a pituitary adenoma, which secretes an excessive amount of GH, disproportionate mandibular growth may occur, leading to skeletal class III malocclusion in adulthood. Excessive growth stops when the tumor is removed, but the skeletal deformity persists, requiring orthognathic surgery to reposition the mandible. This article reports the case of a 31-year-old man referred to the maxillofacial surgery consultation due to severe Angle's class III malocclusion, with prognathism, mandibular asymmetry, and maxillary retrusion. He had a history of disproportionate soft tissue growth (hands and feet) up to 18 years old, less evident after that age. Considering the possibility of acromegaly due to a pituitary adenoma, imaging studies (CT scan and magnetic resonance imaging (MRI)) and directed analytical studies were requested. When the diagnosis was confirmed, the patient was referred to endocrinology and neurosurgery consultations. After undergoing endoscopic resection of the pituitary adenoma, the patient underwent surgery-first orthognathic surgery to correct the dental malocclusion.

Influencing factors for the development of obstructive sleep apnea after orthognathic surgery in skeletal class III patients: A systematic review

This systematic review aimed to investigate the factors that may contribute to the development of OSA after orthognathic surgery in patients with skeletal class III. Electronic searches of PubMed, Embase, Web of Science, and Cochrane databases were conducted up to December 10, 2022. In total, 277 studies were retrieved and screened according to the inclusion and exclusion criteria, and 14 were finally selected. All studies were of medium quality (moderate risk of bias). The occurrence of OSA after orthognathic surgery in patients with class III skeletal relationships depends on surgical factors and patient self-factors. Surgical factors include surgery type, amount of maxillary and mandibular movement, and the patient's postoperative swelling. Patient self-factors include weight, age, gender, and hypertrophy of the soft palate, tonsils, and tongue. According to information in the 14 selected articles, the incidences of OSA after Le Fort I impaction and BSSO setback, BSSO setback, and Le Fort I advancement and BSSO setback were 19.2%, 8.57%, and 0.7%, respectively, mostly accompanied with greater amounts of mandibular recession. However, no clear evidence exists to confirm that orthognathic surgery is a causative factor for postoperative sleep breathing disorders in patients with mandibular prognathism. The wider upper airway in patients with class III skeletal might be the reason for the rare occurrence of OSA after surgery. In addition, obesity and advanced age may lead to sleep apnea after orthognathic surgery. Obese patients should be advised to lose weight preoperatively.

Pharyngeal airway subdivisions in 3-dimensional analysis: Differences between anterior and posterior anatomic boundaries

INTRODUCTION

This study aimed to evaluate if there were differences between anterior and posterior anatomic boundaries used for the 3-dimensional determination of pharyngeal airway.

METHODS

The sample included 150 cone-beam computed tomography scans from healthy patients divided according to (1) age: 6-11, 12-16, and ≥16 years; (2) sex: female and male; (3) anteroposterior skeletal pattern: Class I, II, and III; (4) vertical pattern: brachyfacial, mesofacial, and dolichofacial; and (5) craniocervical inclination (CCI): natural head posture, head flexion, and head extension. Anatomic regions were created to determine the correspondences between structures anteriorly and posteriorly to the pharyngeal airway.

RESULTS

The location of the epiglottis, vallecula, hyoid, C2, and C3 were statistically different according to the CCI, and the location of vallecula, C3, and C4 were different according to sex. However, no statistically significant differences were observed between the frequencies of anterior and posterior anatomic region locations among age and different anteroposterior and vertical skeletal patterns. Posterior landmarks tend to be located below the anterior ones; consequently, the anatomic subregion they define will also be located below.

CONCLUSIONS

Anterior and posterior structures and vertical and anteroposterior skeletal patterns may determine upper airway limits regardless of age. However, the studies must be paired according to sex, and CCI must be standardized.

Validation of a Finite Element Model for Clinical and Virtual Evaluation of the Changes in Airway Dimensions Following Class III Bimaxillary Orthognathic Surgery

Introduction

The aim of this study was to evaluate pharyngeal airway changes in adult skeletal Class III cases whose bimaxillary surgical treatments were planned with different amounts of maxillary and mandibular movement using lateral cephalometric radiographs and finite element analysis (FEA). Our null hypothesis was that bimaxillary orthognathic surgery in which maxillary forward movement (MF) is greater than mandibular backward movement (MB) will result in more expansion of the pharyngeal airway.

Materials and Methods

A total of 31 individuals (11 females, 20 males) with class III skeletal deformity were included in the study. Patients who underwent bimaxillary orthognathic surgery with greater maxillary advancement (MF > MB) were categorized in Group 1 (n = 15), and those with greater mandibular set-back (MB > MF) as Group 2 (n = 16). Changes in airway dimensions were evaluated from lateral cephalometric radiographs. In addition, FEA modeling was used to determine pharyngeal airway changes with 5 different MF/MB combinations performed in skeletal class III bimaxillary surgeries.

Results

Nasopharyngeal and oropharyngeal airway dimensions increased in direct proportion to the amount of MF. Hypopharyngeal volume decreased compared to preoperative value in direct proportion to the decrease in MB. According to the FEA models, total pharyngeal airway volume decreased when MF was less than or equal to MB, was nearly unchanged when MF was 2 mm greater than MB, and increased when MF was 4 mm greater than MB. The results of FEA and lateral cephalometric analysis were compatible.

Conclusion

Our results supported the null hypothesis. We concluded that when possible, planning slightly more maxillary advancement than mandibular set-back will not have an adverse impact on the airway. Although the skeletal deformity only causes forward displacement of the mandible, dividing the skeletal correction between the maxilla and mandible may be considered to avoid the risk to patients' quality of life in terms of respiratory function.

Pharyngeal airway changes five years after bimaxillary surgery - A retrospective study

The aim of this study was to retrospectively evaluate pharyngeal airway (PA) changes after bimaxillary surgery (BMS). Preoperative, immediate- and 5-year postoperative cone-beam computed tomography images of subjects who underwent BMS were assessed. The primary outcome variable was the PA volume. The secondary outcome variables were the retropalatal and oropharyngeal volumes, cross-sectional area, minimal hydraulic diameter, soft tissue, skeletal movements and sleep-disordered breathing (SDB). A total of 50 patients were included, 33 female and 17 male, with a mean age of 26.5 years. A significant increase in the PA volume was seen immediately after surgery (40%), and this increase was still present at 5-year follow-up (34%) (P < 0.001). A linear mixed model regression analysis revealed that a mandibular advancement of ≥5 mm (P = 0.025) and every 1-mm upward movement of epiglottis (P = 0.016) was associated with a volume increase of the oropharyngeal compartment. Moreover, ≥5-mm upward movement of hyoid bone (P = 0.034) and every 1-mm increase in minimal hydraulic diameter (P < 0.001) correlated with an increase of the PA volume. A total of 30 subjects reported improvement in the SDB at 5-year follow-up. This study demonstrated that BMS led to an increase in PA dimensions in non-OSA patients, and these changes were still present at 5-year follow-up. BMS seemed to induce clinical improvement in SDB.

Three-Dimensional Evaluation of Upper Airway Changes After Bimaxillary Surgery of Skeletal Class 3 Patients

The aim of this study was to evaluate the 3-dimensional changes in upper airway space of class 3 patients after surgery with sleep-related breathing disturbance. This is a retrospective cohort study included 25 patients who had undergone bimaxillary orthognathic surgery with maxillary advancement and mandibular setback for skeletal class 3 deformity. The changes in minimum axial area, nasopharyngeal and oropharyngeal airway volume were determined by cone-beam computed tomography images, as well as the sleep parameters by polysomnography preoperatively and postoperatively. The impacts of mandibular setback and maxillary advancement amounts on the airway structures were evaluated and compared with other parameters. The results show that pharyngeal volume measurement means were found to be significantly increased postoperatively (P<0.05). No significant difference was observed in the mean values of minimum axial area and sleep parameters after the operation (P>0.05). A positive relationship was determined between the oropharyngeal volume and minimum axial area changes at a rate of 60% (r: 0.600). No relationship was revealed between airway volume changes and polysomnographic parameters. An increase in the total airway volume and no postoperative sleep-related disturbance symptoms were observed in the patients treated by maxillary advancement and mandibular setback surgery.

Cone beam computed tomography volumetric airway changes after orthognathic surgery: a systematic review

The aim of this systematic review was to provide a structured overview of three-dimensional airway volume changes in relation to various orthognathic surgeries. Clinical human studies performing pre- and postoperative three-dimensional airway volume assessments to investigate volumetric changes of the airway after orthognathic surgery were included. Pre-determined inclusion and exclusion criteria were applied in an extensive search of the PubMed, Embase, and Web of Science electronic databases. The cut-off date was set to January 1, 2022. Forty-one articles reporting retrospective and prospective case-control and case series studies were included. All studies were determined to be of medium quality (moderate risk of bias). The included studies were categorized by type of intervention. Pre- and postoperative volumes were extracted from the available data, and volume changes as a percentage of the preoperative levels were calculated. Isolated mandibular setback surgery generally decreased the airway volume. Isolated maxillary or mandibular advancement, bimaxillary advancement, and surgically assisted maxillary expansion generally increased the airway volume in the total airway and oropharynx, among which the effect of bimaxillary advancement surgery appeared most significant. High heterogeneity exists in the terminology and definitions of the airway and its segments. A more uniform methodology for airway volume measurement is needed to provide an insight into the impact on the airway of specific types of surgical intervention. In conclusion, airway volumes are affected after orthognathic surgery, which may be of clinical significance, especially in patients who are predisposed to obstructive sleep apnoea.

Changes in the pharyngeal airway after different orthognathic procedures for correction of class III dysplasia

Objective

This study was conducted to compare changes in pharyngeal airway after different orthognathic procedures in subjects with class III deformity.

Methods

The study included CBCT scans of 48 skeletal class III patients (29 females and 19 males, mean age 23.50 years) who underwent orthognathic surgery in conjunction with orthodontic treatment. The participants were divided into three groups of 16, as follows: Group 1, mandibular setback surgery; group 2, combined mandibular setback and maxillary advancement surgery; and group 3, maxillary advancement surgery. CBCT images were taken 1 day before surgery (T0), 1 day (T1), and 6 months (T2) later. The dimensions of the velopharynx, oropharynx, and hypopharynx were measured in CBCT images.

Results

In all groups, there was a significant decrease in airway variables immediately after surgery, with a significant reversal 6 months later (P < 0.05). In subjects who underwent maxillary advancement, the airway dimensions were significantly greater at T2 than the T0 time point (P < 0.05), whereas in the mandibular setback and bimaxillary surgery groups, the T2 values were lower than the baseline examination (P < 0.05). The alterations in airway variables were significantly different between the study groups (P < 0.05).

Conclusions

The mandibular setback procedure caused the greatest reduction in the pharyngeal airway, followed by the bimaxillary surgery and maxillary advancement groups, with the latter exhibiting an actual increase in the pharyngeal airway dimensions. It is recommended to prefer a two-jaw operation instead of a mandibular setback alone for correction of the prognathic mandible in subjects with predisposing factors to the development of sleep-disordered breathing.

Postoperative changes in the pharyngeal airway space through computed tomography evaluation after mandibular setback surgery in skeletal class III patients: 1-year follow-up

Background

This study evaluated the pharyngeal airway space changes up to 1 year after bilateral sagittal split osteotomy mandibular setback surgery and bimaxillary surgery with maxillary posterior impaction through three-dimensional computed tomography analysis.

Methods

A total of 37 patients diagnosed with skeletal class III malocclusion underwent bilateral sagittal split osteotomy setback surgery only (group 1, n = 23) or bimaxillary surgery with posterior impaction (group 2, n = 14). Cone-beam computed tomography scans were taken before surgery (T0), 2 months after surgery (T1), 6 months after surgery (T2), and 1 year after surgery (T3). The nasopharynx (Nph), oropharynx (Oph), hypopharynx (Hph) volume, and anteroposterior distance were measured through the InVivo Dental Application version 5.

Results

In group 1, Oph AP, Oph volume, Hph volume, and whole pharynx volume were significantly decreased after the surgery (T1) and maintained. In group 2, Oph volume and whole pharynx volume were decreased (T2) and relapsed at 1 year postoperatively (T3).

Conclusion

In class III malocclusion patients, mandibular setback surgery only showed a greater reduction in pharyngeal airway than bimaxillary surgery at 1 year postoperatively, and bimaxillary surgery was more stable in terms of airway. Therefore, it is important to evaluate the airway before surgery and include it in the surgical plan.

Upper Airway Changes Following Different Orthognathic Surgeries, Evaluated by Cone Beam Computed Tomography: A Systematic Review and Meta-analysis

PURPOSE

This study sought to assess the upper airway changes following different orthognathic surgeries using cone-beam computed tomography.

METHODS

An electronic search of the literature was conducted in major electronic databases including Medline (PubMed), Web of Science, Scopus, and Open Grey for articles published up to January 20, 2018. Human studies that evaluated the changes in the volume and minimum cross-sectional area of the upper airway or its subdivisions in patients who had undergone orthognathic surgery by use of cone-beam computed tomography were included. Manual search of the bibliographies of the included articles was also conducted. The included studies underwent risk of bias assessment.

RESULTS

A total of 1330 articles were retrieved. After excluding the duplicates and irrelevant articles, 41 studies fulfilled the eligibility criteria for this systematic review; out of which, 30 entered the meta-analysis. The majority of studies had a medium risk of bias. Mandibular setback, and maxillary advancement + mandibular setback decreased the volume of the upper airway (-6042.87 mm3 and -1498.78 mm3, respectively) and all its subdivisions in long-term (>3 months), except for the nasopharynx, the volume of which increased following maxillary advancement + mandibular setback. Mandibular advancement and maxillomandibular advancement both increased the upper airway volume in long-term (7559.38 mm3 and 7967.06 mm3, respectively); however, only the changes after the former procedure were significant. The minimum cross-sectional area increased after maxillomandibular advancement (161.43 mm2), and decreased following maxillary advancement + mandibular setback (-23.79 mm2) in long-term.

CONCLUSION

There is moderate evidence to suggest that mandibular advancement is the only orthognathic movement that provides a statistically significant change in long-term upper airway volume.

Upper airway changes following high oblique sagittal split osteotomy (HSSO)

The aim of this study was to evaluate volumetric changes of the posterior airway space (PAS) following bimaxillary surgery using a high oblique sagittal split osteotomy (HSSO) of the mandibular ramus. The cone beam CTs of Class II and Class III patients taken before (T0) and 6-12 months after surgery (T1) were analyzed using 3D software (Mimics® Innovation Suite 18.0). The PAS was divided into three segments (superior, middle, inferior) by three planes parallel to the Frankfurt horizontal plane intersecting at the posterior nasal spine, the velum palatinum and the epiglottis. Total (TPAS) and partial volumes (SPAS = superior, MPAS = middle, IPAS = inferior) were calculated. For the 25 Class II patients, a highly significant increase (p<0.001) of the total, middle and inferior airway space (TPAS: +33.6%, MPAS: +43.1%, IPAS: +55.9%) was found, while the increase of the upper airway space was statistically not significant (+5.4%, p = 0.074). For the 28 Class III patients, the total, middle and inferior airway space increased statistically insignificantly (TPAS: +4.6%, p = 0.265, MPAS: +2.7%, p = 0.387, IPAS: +2.8%, p = 0.495), while the increase of the upper airway space was statistically significant (+9.7%, p = 0.010). Bimaxillary orthognathic surgery using the HSSO technique led to a significant increase of PAS for Class II patients and could conserve the PAS for Class III patients.

Why most patients do not exhibit obstructive sleep apnea after mandibular setback surgery?

Maxillomandibular advancement (MMA) is effective for the treatment of obstructive sleep apnea (OSA). In previous studies, the airway was increased in the anteroposterior and transverse dimensions after MMA. However, the effect of the opposite of mandibular movement (mandibular setback) on the airway is still controversial. Mandibular setback surgery has been suggested to be one of the risk factors in the development of sleep apnea. Previous studies have found that mandibular setback surgery could reduce the total airway volume and posterior airway space significantly in both the one-jaw and two-jaw surgery groups. However, a direct cause-and-effect relationship between the mandibular setback and development of sleep apnea has not been clearly established. Moreover, there are only a few reported cases of postoperative OSA development after mandibular setback surgery.

These findings may be attributed to a fundamental difference in demographic variables such as age, sex, and body mass index (BMI) between patients with mandibular prognathism and patients with OSA. Another possibility is that the site of obstruction or pattern of obstruction may be different between the awake and sleep status in patients with OSA and mandibular prognathism. In a case-controlled study, information including the BMI and other presurgical conditions potentially related to OSA should be considered when evaluating the airway. In conclusion, the preoperative evaluation and management of co-morbid conditions would be essential for the prevention of OSA after mandibular setback surgery despite its low incidence.

Silent Changes in Sleep Quality Following Mandibular Setback Surgery in Patients with Skeletal Class III Malocclusion: A Prospective Study

Mandibular setback surgery (MSS) for skeletal class III patients can result in a relative reduction of pharyngeal airway space (PAS). Consequently, there is a possibility of the decline of sleep quality after surgery. We investigated changes in sleep quality measured by overnight polysomnography (PSG) and the three-dimensional (3D) volumes of PAS following MSS with or without Le Fort I osteotomy (LF I) in class III patients (N = 53). Overnight PSG and cone beam computed tomography were conducted at preoperative stage (T0) and postoperative 3 months (T1). Measurements of PAS volumes were performed, and the subjective symptoms of sleep were evaluated by self-questionnaires. There were significant increases in respiratory disturbance index (RDI) and total respiratory effort-related arousal (RERA) index during T0-T1. The 3D volumes of PAS showed significant decreases in the oropharyngeal airway, hypopharyngeal airway, and total airway spaces. No significant changes were observed in subjective symptoms of sleep. MSS with or without LF I for class III patients could worsen sleep quality by increasing sleep parameters such as the RDI and RERA in PSG, and reduce volumes of PAS at postoperative 3 months. Although subjective symptoms may not show significant changes, objective sleep quality in PSG might decrease after MSS.

Influence of mandibular setback surgery on three-dimensional pharyngeal airway changes

The aim of this study was to investigate the factors influencing three-dimensional changes in pharyngeal airway space after mandibular setback surgery. Airway changes in 48 skeletal class III patients who had undergone mandibular setback surgery alone (n=25, group 1) or with maxillary surgery (n=23, group 2) were analyzed. Linear parameters, cross-sectional area, and volumes of the pharyngeal airway were evaluated before (T0), immediately after (T1), and 1year after surgery (T2) by cone beam computed tomography. Although the reduced airway volume and cross-sectional area recovered slightly in the long term after surgery, the total pharyngeal airway volume (TPV) was significantly reduced compared to baseline, by 15% in group 1 and 12% in group 2. Regression analysis showed that maxillary posterior impaction in two-jaw surgery had a protective effect on preserving TPV. A change in body mass index from T0 to T2 was an important predictor of decreased TPV in one-jaw surgery patients. Maxillary posterior impaction can be a reliable option for compensating the pharyngeal airway reduction after mandibular setback surgery. Postoperative weight gain can increase the risk of postoperative pharyngeal airway reduction. Therefore, these factors need to be considered before and after mandibular setback surgery.

Three-dimensional analysis of the pharyngeal airway space and hyoid bone position after orthognathic surgery

PURPOSE

The aim of this study was to evaluate changes in the pharyngeal airway space (PAS) and hyoid bone position after orthognathic surgery with cone-beam computed tomography (CBCT).

MATERIAL AND METHODS

This study was conducted with the tomographic records of 30 patients with skeletal class II or III deformities submitted to two different types of orthognathic surgery: Group 1 (n = 15), maxillary advancement, and mandibular setback; and Group 2 (n = 15), maxillomandibular advancement. CBCT scans were acquired preoperatively (T₀); and at around 1.5 months (T₁) and 6.7 months (T₂) postoperatively. PAS volume, minimum cross-sectional area (min CSA), and hyoid bone position changes were assessed with Dolphin Imaging 3D software, and results analyzed with ANOVA and a Tukey-Kramer test (p < 0.05).

RESULTS

The hyoid bone was significantly displaced in the horizontal dimension, moving posteriorly in Group 1, and anteriorly in Group 2. Although PAS volume and min CSA increased after both surgeries, these measurements were significantly larger only in Group 2. The significant differences that existed between groups preoperatively no longer existed after the surgeries.

CONCLUSIONS

Both orthognathic surgeries assessed resulted in changes in hyoid bone position and increased PAS volume and min CSA, particularly after maxillomandibular advancement surgery.

No correlation between two-dimensional measurements and three-dimensional configuration of the pharyngeal upper airway space in cone-beam computed tomography

The aim of this study was to evaluate both the 2-dimensional (2D) and 3-dimensional (3D) configuration of the posterior airway space (PAS) in healthy 239 patients using cone-beam computed tomography (CBCT). In particular, we investigated the correlation between the 2D and 3D measurements in view of the potential impact on diagnosis of upper airway obstruction. The pharyngeal airway of each patient was studied at five levels: the level of the posterior nasal spine (PNS), the level of half-height of the PNS and the tip of the soft palate, the level of the tip of the soft palate, the level of the anterior-inferior point of the second vertebra, and at least the level of the top of the epiglottis. At each of these levels, the anterior-posterior dimension as well as the corresponding cross-sectional area was measured. Furthermore we measured the volume of the whole PAS between the first and the last level and compared it with the corresponding 2D values. Differences between genders and age effects were estimated in an analysis of covariance. P values <.05 were considered significant. Linear models were fitted to find the optimal formula to calculate the area or volume from measured distances. Limits of agreement were calculated as 2 ± residual standard deviations. We generated normal 2D and 3D values of the PAS for a normal population. In regard to age, no significant differences were observed. Significant differences were assessed between healthy males and females; however no correlation was observed between the obtained measurements in 2D axial view and the corresponding cross-sectional areas and mean volume in 3D view. In summary, radiologic imaging is a helpful tool to evaluate the airway space in patients with OSAS. However, drawing conclusions from 2D PAS imaging to assess 3D PAS configuration is not reliable, since there is no sufficient correlation between posterior-anterior distances and the corresponding cross-sectional areas.