Orthognathic Surgery: Digital Planning and Osteotomy Techniques

Orthognathic surgery — surgery of the jaw bones aimed at correcting skeletal disharmonies not treatable with compensatory orthodontics alone — has undergone a methodological revolution over the last fifteen years with the introduction of the three-dimensional digital planning workflow. The era of two-dimensional planning on lateral and frontal cephalometrics, combined with direct clinical assessment, has given way to CAD/CAM systems integrating CBCT imaging, facial and occlusal surface scans, and interactive surgical simulation software. This has improved the predictability of aesthetic and occlusal results, reduced operating time and — through the use of custom 3D-printed surgical splints — standardized the surgical technique.

The main upper jaw osteotomy techniques — codified by Tessier (1964) for Le Fort III and Obwegeser (1969) for Le Fort I and the mandibular Sagittal Split Osteotomy — remain fundamentally unchanged in their surgical anatomy, but have been refined in technical detail through extensive accumulated experience. Le Fort I is the osteotomy of choice for correcting vertical and sagittal maxillary discrepancies. The osteotomy is performed at the level of the Le Fort I line — above the root apices, below the zygomatic process — through an upper vestibular incision, elevating the nasal and sinus periosteum. The mobile maxillary segment can be repositioned in any spatial direction: advancement (common in skeletal open bite), superior impaction (lowering the occlusal plane, treating gummy smile), lowering, clockwise/counterclockwise rotation.

The mandibular Bilateral Sagittal Split Osteotomy (BSSO) — commonly called "the sagittal" in clinical practice — is the procedure of choice for correcting mandibular prognathism and retrognathism. The principle is sagittal splitting of the mandibular body front-to-back along the Obwegeser-Dal Pont osteotomy line, separating the distal tooth-bearing segment (repositioned to the newly planned position) from the proximal condylar segment (which remains in the glenoid fossa). Fixation stability — achieved with titanium plates or transbuccal bicortical screws — determines the result's long-term stability. The condylar axis must be maintained in centric relation position: condylar displacement during fixation is the main cause of relapse and post-operative joint pain.

The timing of combined orthodontic-surgical treatment has undergone significant revision with the introduction of the "surgery first" protocol. The traditional protocol involves: pre-surgical orthodontics (12-18 months) to decompensate the incisors and create arches compatible with the surgical plan, then surgery, then post-surgical finishing orthodontics (6-9 months). The "surgery first" (SFA) protocol — introduced by Liou et al. (2011) and now common in East Asia and growing in Europe — reverses the sequence: surgery immediately, then orthodontics to the final result. The main advantage is reduced overall treatment time (often from 30-36 months to 14-18 months) and immediate aesthetic improvement that boosts compliance. The requirement is very precise pre-surgical virtual planning.

Digital surgical planning software (Materialise ProPlan CMF, DeltaMesh Simplant OMS, SurgiCase Ortho) allows integrating the segmented CBCT model with the three-dimensional face scan and digital dental model. In this virtual environment, the surgeon simulates the osteotomies and assesses the final result both cephalometrically and in terms of facial aesthetics, using soft-tissue profile analysis software (nose, lips, chin) that predicts changes in soft tissue in response to the planned bone movements. The most commonly used soft-tissue/bone ratios are: upper lip 0.5-0.6:1 for Le Fort I advancement, lower lip 0.8-0.9:1 for mandibular advancement.

Genioplasty — chin osteotomy performed separately or in combination with Le Fort I and BSSO — has become a routine procedure in modern orthognathic surgery to optimize profile balance. The chin can be advanced, set back, lowered, raised or shifted laterally to correct asymmetries, significantly expanding treatment possibilities compared to isolated bimaxillary surgery. In patients with maxillary and mandibular retrognathism corrected with bimaxillary surgery, additional advancement genioplasty is indicated when chin projection remains insufficient after the main skeletal movements.