Repoziționarea scheletală maxilomandibulară și căile respiratorii superioare: rezultate funcționale în cazurile de chirurgie ortognatică

Introduction

Orthognathic surgery is traditionally framed as the correction of dentofacial deformity, yet its skeletal movements also reshape the anatomic boundaries of the upper airway. This interaction is clinically important in two overlapping scenarios: (1) patients with craniofacial phenotypes that predispose to obstructive sleep apnea (OSA) (e.g., mandibular retrognathism and/or maxillary hypoplasia) and (2) patients undergoing elective skeletal repositioning in whom airway compromise must be avoided (e.g., mandibular setback for class III correction)⁽¹⁾.

This narrative review summarizes: (i) the anatomic and physiologic basis for airway change after maxillary and mandibular repositioning, (ii) how different movement vectors (advancement, setback, rotation) differentially influence retropalatal and retroglossal segments, and (iii) how morphologic changes translate into functional endpoints, such as AHI, oxygenation, and patient-reported sleepiness. Particular emphasis is placed on mandibular advancement through bilateral sagittal split osteotomy (BSSO) and on maxillomandibular advancement (MMA), which is widely considered the most effective skeletal operation for moderate-to-severe OSA. The final sections address preoperative evaluation, expected outcomes, limitations of imaging-based airway assessment, and complications that shape long-term stability.

Materials and method

This article was designed as a narrative review of the literature on maxillomandibular skeletal repositioning and postoperative airway-related outcomes in ortho­gnathic surgery, with emphasis on mandibular advancement via BSSO and on MMA for OSA. The review was intended to integrate anatomic mechanisms, imaging-based airway surrogates and functional sleep outcomes into a clinically oriented synthesis.

Relevant publications were identified through searches of major biomedical databases (e.g., PubMed/MEDLINE) and targeted searches in related dental and sleep-medicine journals, supplemented by manual screening of reference lists from key reviews and highly cited primary studies. Search terms combined concepts related to orthognathic surgery (e.g., “maxillomandibular advancement”, “bilateral sagittal split osteotomy”, “Le Fort I”, “mandibular setback”) with airway and sleep outcomes (e.g., “upper airway”, “pharyngeal airway”, “airway volume”, “obstructive sleep apnea”, “apnea-hypopnea index”).

Evidence was prioritized for inclusion when it addressed: (i) a defined orthognathic movement (mandibular advancement, setback, maxillary advancement and/or MMA) and (ii) objective airway measurements (CT/CBCT or cephalometric metrics) and/or functional sleep outcomes (polysomnography or validated symptom scales). Systematic reviews and meta-analyses were used to frame overall effect estimates where available, and cohort studies were used to illustrate procedure-specific findings and sources of heterogeneity. In line with narrative-review quality recommendations such as the Scale for the Assessment of Narrative Review Articles (SANRA), the methods and citations were reported to support transparency of the literature search and the reasoning that underpins the synthesis.

Definitions and outcome measures

Obstructive sleep apnea severity is commonly stratified using the apnea-hypopnea index (AHI; events/hour): mild (5-14), moderate (15-29) and severe (≥30). Polysomnography remains the reference standard for diagnosis and for postoperative assessment⁽²⁾.

In the surgical literature on maxillomandibular advancement, the outcomes are often reported using two pragmatic categories: surgical success (postoperative AHI<20 events/h and a ≥50% reduction from baseline) and surgical cure (postoperative AHI<5 events/h). These thresholds facilitate comparison across cohorts, but should be interpreted alongside other endpoints (oxygen saturation nadir, Epworth Sleepiness Scale, blood pressure and quality-of-life instruments) and with attention to follow-up duration⁽³⁾.

Anatomy and physiology of the upper airway

The upper airway comprises the nasal cavity, nasopharynx, oropharynx and hypopharynx. For sleep-surgery reporting, the pharyngeal airway is often discussed by functional segments: retropalatal (behind the soft palate), retroglossal (behind the tongue base) and hypopharyngeal (inferior pharynx). Airway patency reflects both the osseous “container” (maxillomandibular position) and soft-tissue/neuromuscular factors that determine the collapsibility⁽⁴⁾.

The mandible contributes to airway stability through its muscular attachments, including the genioglossus and geniohyoid (via genial tubercles) and the suprahyoid complex. When the mandible is positioned posteriorly, the tongue base and hyoid-related soft tissues are more likely to sit closer to the posterior pharyngeal wall, reducing the retroglossal airway – particularly in the supine position⁽⁵⁾.

During sleep, physiologic reductions in upper-airway dilator muscle tone increase collapsibility. In patients with a relatively small skeletal framework or increased soft-tissue volume, this balance may shift toward repetitive partial or complete obstruction, producing apneas/hypopneas, intermittent hypoxemia and sleep fragmentation⁽⁶⁾.

How skeletal movements change the airway: key mechanisms

Mandibular advancement typically increases retro­glossal caliber by advancing the tongue base and by tensioning the suprahyoid/infrahyoid soft-tissue envelope. Maxillary advancement primarily influences the retropalatal segment by anterior translation of the maxillary complex and attached soft palate and by changing the spatial relationship between the soft palate and the posterior pharyngeal wall⁽⁷⁾.

Rotation and vertical changes (e.g., counterclockwise rotation with advancement) can further enlarge the airway by advancing the chin and tongue base beyond the linear advancement amount. Conversely, clockwise rotation or posterior repositioning may reduce airway dimensions in susceptible phenotypes. Because airway measurements are posture-sensitive, comparisons should ideally use standardized imaging protocols and be interpreted alongside polysomnographic outcomes⁽⁸⁾.

Mandibular setback is consistently associated with a reduction in posterior airway space on imaging, but the degree to which this translates into new-onset OSA appears variable and likely moderated by baseline risk factors (age, Body Mass Index, sex and preoperative airway anatomy). This distinction – morphologic narrowing versus clinical sleep-disordered breathing – should be explicit in treatment planning and in patient counseling⁽⁹⁾.

Relationship between craniofacial morphology and OSA

Craniofacial phenotypes associated with OSA include mandibular retrognathism, maxillary hypoplasia, a steep mandibular plane and reduced posterior airway space. In such patients, narrowing is frequently observed in the retropalatal and retroglossal regions, where soft-tissue collapse during sleep is most likely to occur⁽¹⁰⁾.

Obstructive sleep apnea is characterized by repetitive episodes of partial (hypopnea) or complete (apnea) upper-airway obstruction during sleep, resulting in oxygen desaturation and arousals. Although AHI is the most widely reported metric, clinically meaningful assessment also includes symptom burden (e.g., daytime sleepiness), cardiometabolic comorbidities and objective oxygenation parameters⁽¹¹⁾.

Surgical strategies and expected airway effects

Orthognathic procedures influence the airway through predictable anatomic pathways, but the magnitude of change depends on movement direction (advancement versus setback), rotation and soft-tissue adaptation. Common skeletal strategies relevant to airway outcomes include:

• Le Fort I osteotomy (maxillary repositioning; with the greatest impact on retropalatal space);
• Bilateral sagittal split osteotomy (BSSO) (mandibular advancement or setback; primary impact on retroglossal space);
• Maxillomandibular advancement (MMA) (combined advancement; multi-level airway expansion)⁽¹²⁾.

For obstructive sleep apnea, continuous positive airway pressure (CPAP) remains the first-line therapy for many patients; however, among skeletal procedures, MMA is consistently reported as the most effective operation for moderate-to-severe disease, because it enlarges both retropalatal and retroglossal segments and reduces multi-level collapsibility⁽¹³⁾.

Mandibular advancement via BSSO: indications, mechanism and outcomes

Bilateral sagittal split osteotomy is a foundational mandibular procedure in orthognathic surgery, and can be used to advance, set back, and/or rotate the mandible with three-dimensional control. From an airway standpoint, advancement is the relevant movement in patients with mandibular deficiency and retroglossal narrowing, whereas setback may reduce airway dimensions and warrants risk-aware planning in susceptible patients⁽¹⁴⁾.

Technique overview (brief)

Classically attributed to Obwegeser and later modifications (e.g., Dal Pont), BSSO creates a sagittal split of the mandibular ramus to separate the proximal (condylar) and distal (tooth-bearing) segments, allowing controlled repositioning and rigid fixation. When the distal segment is advanced, the genial musculature and suprahyoid complex are carried anteriorly, providing a plausible anatomic basis for retroglossal enlargement⁽¹⁵⁾.

Clinically, this translates into anterior displacement of the tongue base and reduced crowding behind the mandible, which can decrease airflow resistance and lower the propensity for collapse in the retroglossal segment⁽¹⁶⁾.

Expected airway changes (imaging)

Three-dimensional imaging studies (CT/CBCT) commonly report that mandibular advancement via BSSO is associated with:

• increased anteroposterior dimension and/or minimum cross-sectional area in the oropharynx (often retroglossal);
• increased segmental or total pharyngeal airway volume;
• reduced tendency toward dynamic narrowing in susceptible phenotypes (inferred, not directly measured by static scans)⁽¹⁷⁾.

Because BSSO advancement does not directly advance the maxilla and soft palate, its effect on the retropalatal segment may be smaller than the effect achieved with MMA, which addresses both major collapse levels in many patients⁽¹⁸⁾.

BSSO advancement for OSA: when is it enough?

Isolated mandibular advancement may be considered in carefully selected patients with dominant mandibular retrognathism, relatively preserved maxillary position and evidence of retroglossal obstruction. Reported improvements in AHI and symptoms are variable, reflecting differences in baseline severity, Body Mass Index, concomitant soft-tissue procedures and follow-up duration⁽¹⁹⁾.

Several cohorts suggest that larger advancements (often cited in the range of approximately 8-10 mm or greater) are associated with better functional improvement, but the relationship is not strictly linear and should be individualized using virtual surgical planning, occlusal constraints and patient-specific risk factors⁽²⁰⁾.

Maxillomandibular advancement (MMA) for OSA: airway effects and clinical evidence

MMA advances both jaws – typically through a Le Fort I osteotomy and BSSO –, thereby enlarging the skeletal framework that surrounds the pharyngeal airway. Compared with mandibular advancement alone, MMA more reliably expands the airway across multiple levels and can also reduce collapsibility by increasing soft-tissue tension: retropalatal, retroglossal and hypopharyngeal⁽²¹⁾.

Across systematic reviews and long-term cohort studies, MMA is generally associated with substantial reductions in AHI, improvements in oxygenation, and better patient-reported sleepiness and quality of life. Reported results vary by baseline severity and definitions used, but the “success” and “cure” rates are frequently reported as high in appropriately selected patients. Large relative reductions in AHI are common, particularly in moderate-to-severe OSA. Also, improvement in oxygen saturation metrics (e.g., nadir SpO₂, desaturation indices) along with improvement in symptom burden and quality-of-life measures (e.g., Epworth Sleepiness Scale)⁽²²⁾ are reported.

Long-term follow-up data suggest that benefits can remain durable for many patients, yet relapses may occur – often in association with weight gain, aging-related changes in soft tissue tone, or the incomplete correction of multi-level obstruction. For this reason, postoperative reassessment with sleep testing is recommended when symptoms recur or when risk factors evolve⁽²³⁾.

Patient selection and preoperative evaluation

Optimal outcomes depend on aligning skeletal movements with the patient’s obstruction pattern and overall risk profile. Preoperative evaluation should establish baseline OSA severity, identify likely collapse levels and document comorbidities that influence the perioperative risk and the long-term durability (e.g., obesity, hypertension, cardiopulmonary disease). A typical workup includes:

• sleep testing (polysomnography or home sleep apnea testing, as appropriate);
• craniofacial and occlusal assessment (including cephalometric analysis);
• upper-airway and ENT assessment (nasal obstruction, tonsillar hypertrophy, other anatomic contributors);
• 3D imaging (CT/CBCT) with attention to standardized head/neck posture and segmentation protocols⁽²⁴⁾.

Virtual three-dimensional planning supports coordinated maxillary and mandibular movements within occlusal and esthetic constraints, and can help anticipate airway-space changes. However, static CT/CBCT images are typically acquired awake, and may be sensitive to head/neck posture; therefore, imaging-derived airway changes should be interpreted as anatomic surrogates rather than direct measures of sleep-time collapsibility⁽²⁵⁾.

Functional outcomes: what should be measured?

Airway enlargement on imaging is not itself a clinical endpoint. Functional outcomes after skeletal repositioning should be evaluated using a combination of objective sleep-study metrics, physiologic oxygenation measures and patient-centered outcomes. Commonly reported domains include:

• polysomnographic indices (AHI; oxygen desaturation index; arousal index);
• oxygenation parameters (SpO₂ nadir; time below a saturation threshold);
• symptoms and quality of life (Epworth Sleepiness Scale; functional outcomes measures)⁽²⁶⁾.

Many series report high surgical success rates for MMA using standard AHI-based definitions, whereas outcomes after isolated mandibular advancement are more heterogeneous. Interpretation should account for baseline severity, Body Mass Index, movement magnitude and the timing of postoperative sleep testing⁽²⁷⁾.

Complications, limitations and long-term considerations

As with other orthognathic operations, the complications may be neurologic, skeletal, occlusal, or airway-related. Frequently discussed issues include:

• inferior alveolar nerve sensory disturbance (particularly after BSSO);
• skeletal relapse and/or unfavorable rotation affecting occlusion and airway;
• occlusal instability requiring orthodontic refinement or revision⁽²⁸⁾.

In OSA-focused cases, patient selection and movement planning are central to benefit-risk balance. The long-term durability is influenced by postoperative weight trajectory and aging, and the evidence base remains dominated by observational cohorts with variable imaging protocols and outcome definitions – factors that should temper overprecise expectations during counseling⁽²⁹⁾.

Future directions

Future progress will likely come from better phenotyping of obstruction patterns (multi-level collapse, positional dependency), standardized 3D airway measurement protocols and integration of virtual planning with functional prediction (e.g., biomechanical modeling and computational fluid dynamics).

Machine-learning approaches may help link movement vectors and patient factors (baseline AHI, Body Mass Index, craniofacial morphology) to expected postoperative trajectories, but prospective validation with long-term polysomnographic outcomes remains a key gap⁽³⁰⁾.

Table 1 presents a summary of procedures, airway effects and functional outcomes.

Figure 1 presents a step-by-step analysis and management of such a complex case.

Conclusions

Maxillomandibular skeletal repositioning can meaningfully influence the upper-airway anatomy and, in appropriately selected patients, improve the functional outcomes relevant to obstructive sleep apnea. Mandibular advancement via BSSO may provide benefit when the retroglossal compromise is dominant and the maxillary position is adequate, but the results are heterogeneous and should be interpreted alongside objective sleep testing. Maxillomandibular advancement offers the most consistent multi-level airway expansion among skeletal operations, and it is supported by systematic reviews and long-term cohort data showing substantial AHI and symptom improvements. Across all approaches, standardized evaluation, careful movement planning and postoperative follow-up are essential to optimize durability and patient-centered outcomes.