Sagittal Split Osteotomy Techniques and Postoperative Recovery

Sagittal split osteotomy is a surgical procedure used to correct jaw misalignment, primarily involving the mandible. It improves bite function, facial symmetry, and overall oral health. Advances in technique and fixation methods have enhanced outcomes and reduced complications, making it a reliable option for many patients.

Successful surgery depends on precise execution and proper postoperative care. Understanding the anatomy, indications, procedural steps, and recovery process is essential for optimizing results.

Mandibular Anatomy

The mandible, or lower jaw, is the largest and strongest bone of the human face, essential for mastication, speech, and facial structure. It articulates with the temporal bones at the temporomandibular joints (TMJs), allowing for complex movements such as elevation, depression, protrusion, and lateral deviation. Its unique morphology and biomechanical properties make it a focal point in orthognathic surgery, where precise anatomical knowledge is crucial.

Structurally, the mandible consists of a horizontal body and two vertical rami, forming the condylar and coronoid processes. The condylar process articulates with the temporal bone, forming the TMJ, which is critical for jaw mobility. The coronoid process serves as the attachment site for the temporalis muscle, a key muscle in mastication. The mandibular body houses the inferior alveolar nerve within the mandibular canal, requiring careful handling during osteotomy to prevent neurosensory deficits. The mental foramen, located on the anterior surface, allows passage of the mental nerve and vessels, supplying sensation to the lower lip and chin.

The mandible’s internal structure consists of dense cortical bone externally and porous cancellous bone internally. Cortical bone provides stability for fixation, while cancellous bone facilitates healing. The mandibular angle, a region of high biomechanical stress, requires careful handling during surgery. The lingual aspect features the mylohyoid ridge, which serves as an attachment for the mylohyoid muscle, contributing to floor-of-mouth support.

Indications For This Surgery

Sagittal split osteotomy corrects mandibular discrepancies affecting function and aesthetics. One common indication is mandibular prognathism, where the lower jaw protrudes excessively beyond the upper jaw, leading to an imbalanced bite and potential difficulties with mastication and speech. This condition, often associated with Class III malocclusion, places strain on the TMJs and surrounding musculature, increasing the risk of temporomandibular disorders (TMDs). By repositioning the mandible, sagittal split osteotomy improves occlusal harmony and alleviates functional impairments.

Mandibular retrognathia—an underdeveloped or recessed lower jaw—also necessitates surgical correction. This condition is linked to Class II malocclusion, where the upper teeth significantly overlap the lower teeth, compromising chewing efficiency and potentially affecting speech. Additionally, mandibular retrognathia is associated with obstructive sleep apnea (OSA), as the posterior displacement of the mandible can contribute to airway obstruction. Studies show that sagittal split osteotomy, often combined with maxillary advancements, improves airway patency and reduces apnea-hypopnea index (AHI) scores.

Jaw asymmetries, whether congenital or acquired, also warrant sagittal split osteotomy. Conditions like hemimandibular elongation or hyperplasia result in unilateral overgrowth, creating facial asymmetry that affects function and appearance. Trauma-induced discrepancies, including malunion of mandibular fractures, may require surgical intervention to restore alignment. By repositioning the affected segments, sagittal split osteotomy improves facial symmetry and reduces the psychological impact of jaw deformities.

Technique Steps

Sagittal split osteotomy requires meticulous planning and precise execution. The procedure begins with intraoral incisions along the mandibular ramus and body, avoiding the mental foramen to protect the mental nerve. Subperiosteal dissection exposes the lateral and medial cortical surfaces, ensuring a clear surgical field without excessive soft tissue disruption. A reciprocating saw or piezoelectric device creates controlled osteotomies along the external oblique ridge, extending inferiorly toward the mandibular angle. This approach minimizes thermal injury and promotes clean bony cuts essential for healing.

After dividing the lateral cortices, the split is propagated through the cancellous bone using chisels to achieve controlled separation of the proximal and distal segments. This maneuver requires balanced force to prevent unfavorable fractures, particularly in dense cortical regions near the lingula. Surgeons must ensure the split follows the intended path, maintaining the integrity of the inferior alveolar nerve. In some cases, nerve mobilization is necessary to prevent compression or stretching, reducing the risk of postoperative paresthesia. Proper handling of the proximal segment is crucial, as it retains the muscular attachments needed for mandibular function and stability.

The distal segment is repositioned according to the preoperative plan, which may involve advancement, setback, or rotation for optimal occlusal alignment. The proximal segment must also be carefully aligned to preserve TMJ function and avoid condylar displacement. Occlusal splints or three-dimensional surgical planning software guide precise adjustments for both aesthetics and biomechanics. Once positioned, rigid fixation methods, such as titanium plates and bicortical screws, stabilize the osteotomy. The choice of fixation depends on bone quality, movement magnitude, and surgeon preference, ensuring adequate vascularity for bone remodeling.

Bony Fixation Methods

Stabilizing the mandibular segments after sagittal split osteotomy is essential for healing and long-term function. Rigid fixation techniques have largely replaced maxillomandibular fixation (MMF), providing immediate skeletal stability and allowing early jaw mobilization. Titanium plates and screws are commonly used, offering strong mechanical support while minimizing interference with bone remodeling. These devices are placed along the lateral cortical surface, avoiding excessive compression that could compromise vascular supply.

The choice between monocortical and bicortical screws depends on case-specific requirements. Monocortical screws, secured into the lateral cortex without penetrating the lingual side, reduce the risk of inferior alveolar nerve injury while maintaining stability. Bicortical screws pass through both cortical layers, providing enhanced resistance to shear forces, particularly in larger mandibular advancements. Studies indicate that bicortical fixation reduces micromovement at the osteotomy site, lowering the risk of delayed union or relapse, though precise angulation is required to prevent stress on surrounding structures.

Postoperative Healing

Recovery after sagittal split osteotomy involves multiple phases requiring careful management. The immediate postoperative period includes swelling, discomfort, and limited jaw mobility due to soft tissue trauma. Cold therapy in the first 48 hours minimizes edema, while analgesics and anti-inflammatory medications manage pain. Patients typically follow a liquid or soft diet for several weeks to reduce strain on the osteotomy site and allow gradual adaptation to the new mandibular position. Protein-rich foods and adequate hydration support tissue repair and metabolic balance.

Functional rehabilitation is crucial as healing progresses. Jaw exercises, guided by a physical therapist or oral surgeon, restore range of motion and prevent muscle stiffness. Controlled movements, such as gentle opening and lateral excursions, encourage neuromuscular adaptation without excessive stress on the bony segments. Maintaining meticulous oral hygiene is essential, as limited mouth opening can hinder routine brushing and flossing. Antibacterial mouth rinses help reduce bacterial load and prevent infections.

Long-term stability is assessed through follow-up imaging, evaluating bone remodeling and fixation integrity. Most patients achieve full recovery within three to six months, with adherence to postoperative protocols significantly influencing outcomes.