Why move both jaws in one operation?

When the deformity involves disproportion of both jaws, or when one-jaw movement cannot give both a stable bite and balanced facial proportions, repositioning the maxilla and mandible together lets the correction be shared between them for a better and more stable result.

How does two-jaw advancement help sleep apnoea?

Advancing the maxilla and mandible together pulls the soft palate, tongue base, and attached muscles forward, enlarging the space behind them. This maxillomandibular advancement widens the pharyngeal airway and reduces apnoeic events in obstructive sleep apnoea.

Bimaxillary Surgery and Combined Procedures

Bimaxillary surgery repositions both the upper and lower jaws in a single operation, combining a Le Fort I maxillary osteotomy with a mandibular sagittal split. It is used when a balanced facial result and a stable occlusion cannot be achieved by moving one jaw alone, and — as maxillomandibular advancement — to enlarge the airway in obstructive sleep apnoea.

Definition

Bimaxillary surgery is the combined surgical repositioning of the maxilla (by Le Fort I osteotomy) and the mandible (by sagittal split or other osteotomy) in one operation, planned so that each jaw reaches its predetermined position to correct dentofacial deformity or enlarge the upper airway.

Scope

This topic covers two-jaw (bimaxillary) surgery: why both jaws are moved together, how the procedure is sequenced and planned, the use of intermediate and final splints, and the special case of maxillomandibular advancement for obstructive sleep apnoea. It also touches on simultaneous genioplasty as a combined procedure. The entry is reference material, not operative guidance.

Core questions

When does correcting a deformity require moving both jaws rather than one?
How are the two jaw movements sequenced, and how do intermediate and final splints transfer the plan to the operating room?
How does maxillomandibular advancement enlarge the pharyngeal airway in obstructive sleep apnoea, and how effective is it?

Key concepts

Two-jaw (bimaxillary) repositioning
Operative sequencing of maxilla and mandible
Intermediate and final occlusal splints
Maxillomandibular advancement (MMA)
Pharyngeal airway enlargement
Adjunctive genioplasty
Three-dimensional virtual surgical planning

Mechanisms

In a typical bimaxillary procedure the maxilla is osteotomised and mobilised first; an intermediate splint then positions the maxilla relative to the as-yet-unmoved mandibular condyles, the maxilla is fixed, and the mandibular sagittal split is completed so that the lower jaw is brought into a final occlusal relationship defined by a final splint. Moving both jaws lets the surgeon distribute the correction between them and control the occlusal plane and facial proportions more freely than single-jaw surgery. When the maxilla and mandible are advanced together (maxillomandibular advancement), the attached soft palate, tongue base, and suprahyoid musculature are carried forward, enlarging and stabilising the pharyngeal airway (Naran, 2018; Holty, 2010).

Clinical relevance

Bimaxillary surgery illustrates how distributing movement across both jaws expands the correction achievable and how the same skeletal advancement can serve both an occlusal-aesthetic and an airway purpose. The content is explanatory and does not constitute advice on whether any individual should undergo surgery.

Epidemiology

Two-jaw procedures are common in contemporary orthognathic practice and, being longer and more extensive, carry the combined morbidity of both osteotomies, including greater blood loss; large reviews nonetheless report low rates of major complications (Chow, 2007). As maxillomandibular advancement, the operation produces large reductions in the apnoea-hypopnoea index in meta-analyses of obstructive sleep apnoea, with generally favourable patient-reported aesthetic outcomes (Holty, 2010; Jamal, 2023).

History

As rigid internal fixation and cephalometric prediction matured, surgeons increasingly combined maxillary and mandibular osteotomies in one operation, and the development of model surgery and occlusal splints made the transfer of two-jaw plans reliable. The recognition that advancing both jaws enlarges the airway established maxillomandibular advancement as a surgical option for obstructive sleep apnoea, later supported by systematic review (Holty, 2010), while three-dimensional virtual planning has since refined combined movements (Naran, 2018).

Debates

Maxillomandibular advancement as a treatment for obstructive sleep apnoea: Meta-analytic data show large reductions in the apnoea-hypopnoea index after maxillomandibular advancement, but its place relative to continuous positive airway pressure and other surgery, and concerns about the magnitude of facial change, keep its indications under discussion.

Key figures

William R. Proffit
Larry M. Wolford
Christian Guilleminault

Seminal works

holty-2010
naran-2018

Frequently asked questions

Why move both jaws in one operation?: When the deformity involves disproportion of both jaws, or when one-jaw movement cannot give both a stable bite and balanced facial proportions, repositioning the maxilla and mandible together lets the correction be shared between them for a better and more stable result.
How does two-jaw advancement help sleep apnoea?: Advancing the maxilla and mandible together pulls the soft palate, tongue base, and attached muscles forward, enlarging the space behind them. This maxillomandibular advancement widens the pharyngeal airway and reduces apnoeic events in obstructive sleep apnoea.