Bilateral Sagittal Split Osteotomy (BSSO)

Bilateral Sagittal Split Osteotomy (BSSO) is a surgical procedure used in orthognathic surgery to reposition the lower jaw, also known as the mandible. BSSO involves cutting the mandible in a specific manner and then repositioning it to correct various deformities or abnormalities of the lower face. This procedure allows for adjustments in the mandible’s position, including moving it forward, backward, upward, or downward. BSSO is typically performed intraorally, which means there are no visible external scars on the patient’s face.

BSSO surgery is a versatile procedure that can correct a range of lower face deformities, including:

• Bringing a protruding lower jaw backward if it extends too far forward.
• Advancing a retruded lower jaw forward if it is too far back.
• Correcting any tilt or deviation of the lower jaw to achieve proper alignment.
• Addressing a variety of lower face and jaw-related issues, from bite defects to traumatic injuries.

This surgical technique offers comprehensive solutions for lower face deformities while minimizing visible scarring.

BSSO surgery is considered a safe and reliable procedure when properly diagnosed and planned by the operating surgeon. The surgical process involves:

Intraoral Access: An incision is made inside the mouth, typically behind the last teeth of the lower jaw. This approach ensures there are no external scars.

Bone Cuts: The surgeon makes specific cuts on the top and side edges of the jaw to create an overlap of bone between the cut surfaces.

Jaw Separation: Special instruments, known as osteotomes, are used to split the jaw along these cut edges.

Repositioning: The lower jaw is repositioned to its corrected location based on the preoperative planning.

Fixation: The repositioned jaw segments are fixed securely using screws and plates.

Occlusion/Bite Correction: Intraoral wiring is sometimes used to ensure proper alignment and occlusion of the lower jaw.

Closure: The incision inside the mouth is closed in layers with absorbable sutures.

BSSO surgery is indicated for various conditions of the lower jaw or lower face, including:

• Obstructive sleep apnea.
• Temporomandibular joint ( TMJ ) disorders.
• Malocclusion issues arise from skeletal disharmonies.
• Orthodontic dental bite problems cannot be adequately treated with braces alone.
• A wide range of facial deformities where aesthetic improvement can enhance self-esteem.
• Speech defects and cases of facial trauma.

In cases of severe facial deformities, BSSO can be combined with LeFort Osteotomy , leading to a procedure known as Bi Jaw or Bi Max surgery. BSSO is often routinely combined with chin surgery or genioplasty to address multiple facial concerns comprehensively.

Before performing orthognathic surgery, it is essential to confirm that skeletal growth is complete. This usually occurs around 15 to 16 years in girls and 17 to 18 years in boys. Mandibular (lower jaw) growth typically continues for a short period after maxillary (upper jaw) growth.

Successful BSSO surgery relies on thorough preoperative planning, including investigations such as 3D CT scans of the face, frontal and lateral face photos, cephalometric X-rays, and dental impressions. Cephalometric X-rays are particularly important as they reveal abnormal growth patterns of the jaws concerning the cranial base. A detailed analysis of skeletal, dental, and soft tissue findings is conducted, and dental models are created for mock surgery planning.

Several factors and conditions may contraindicate BSSO surgery, including major medical comorbidities, cardiac diseases, active dental infections, patients in the active growth phase, psychiatric disorders, uncontrolled seizure disorders, substantial differences in patient and surgeon goals, smoking or substance abuse habits, and concerns about the blood supply to the mandible.

The surgical procedure of BSSO involves several steps:

Anesthesia: The procedure is performed under general anesthesia with nasal endotracheal intubation. Local anesthesia with lidocaine and epinephrine may also be used to minimize blood loss.

Intraoral Incision: An incision is made inside the mouth, typically behind and to the side of the patient’s last lower molars. This approach avoids external scars.

Bone Cuts: The surgeon makes cuts along the top and side edges of the jaw to create overlapping bone segments for repositioning.

Jaw Separation: Osteotomes are used to split the jaw along these cut edges.

Repositioning: The lower jaw is moved to its corrected position as determined during preoperative planning.

Fixation: The repositioned jaw segments are securely fixed in place using screws and plates.

Occlusion/Bite Adjustment: Intraoral wiring may be used to achieve proper occlusion and bite alignment.

Closure: The intraoral incision is closed in layers using absorbable sutures.

Distraction surgery in BSSO involves separating the mandible without immediate advancement. Instead, an internal or external distractor is applied to both mandible segments, gradually moving the lower jaw forward over time. This technique is beneficial for patients with significantly underdeveloped mandibles.

Recovery from BSSO surgery typically includes:

• Overnight monitoring in the post-operative recovery room.
• Swelling and bruising usually subside within a week, with the use of ice packs to reduce swelling.
• A soft diet for 4 to 6 weeks, starting with liquids for about a week.
• One week of antibiotic treatment.
• The use of soft elastics to maintain the lower jaw in its new position.
• Discharge from the hospital after 3 to 4 days, with a follow-up visit scheduled for a week later.
• Early postoperative occlusal changes due to edema and muscle adaptation.
• Strict postoperative oral hygiene practices, including the use of a soft toothbrush and antibacterial mouth rinse.

Orthodontists play a crucial role in BSSO surgery, both before and after the procedure. Pre-surgical orthodontic treatment lasting approximately 7 to 10 months may be required. Post-surgical orthodontics aims to settle the teeth into their final occlusion, and the duration of treatment can vary depending on factors like the pre-surgical setup and planned surgical movements.

While BSSO surgery is generally safe and reliable, it may entail certain complications, including bleeding, infective complications such as abscess formation, occlusal changes, dental and periodontal injuries, unfavorable fractures, nerve injuries affecting the lower lip and teeth, TMJ dysfunction, non-union of bony segments, malocclusion issues, retraction of the gingiva, and other possible complications specific to the patient’s case. Patients should consult with their healthcare providers and surgeons for a thorough evaluation and to discuss potential risks and benefits related to BSSO surgery in their specific situation.