Sagital Split Osteotomy

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Surgical Procedure:	Steps 1 to 4
1. General and Local Anesthesia (Fig:1)    Sagital split osteotomy is done under general anesthesia. Naso-endotracheal intubation is used. This specially designed tube which has got an extranasal curve will not kink nor exert traction on the nose. Hypotensive anesthesia is preferred since it reduces the bleeding. A throat pack to prevent any inadvertent aspiration of fluids is placed.   Local anesthesia with adrenaline is given at the site of incision. A Mouth-prop is placed to keep the mouth opened in a stable position.
2. Incision (fig:2)    A vertical incision on the buccal alveolus extending into the sulcus at the anterior region of the 1st molar (posterior to the mental foramen) and a horizontal incision 2 mm. below the cervical region of the tooth is made.   Another incision in the retromolar region extending upwards through the anterior border of the ramus up to a little above the deepest part of its concavity is also made.
3. Subperiosteal Dissection & Flap Elevation (fig:3)    At the region of the horizontal ramus subperiosteal dissection is done up to the inferior border of the mandible. At the vertical ramus the buccal flap is raised to expose about 1 cm of bone.   On the lingual side of the vertical ramus after dividing the insertion of the temporalis muscle, subperiosteal tunneling is done up to the level of the mandibular foramen. (The mandibular foramen is almost at the level of the deepest part of the concavity at the anterior border).   Using a heavy curved Crocker's forceps the coronoid process is held. This will give proper stabilization and good retraction. The sigmoid notch is identified and tunneling is made downward, and the mandibular nerve entering the foramen is identified. A channel retractor is inserted subperiosteally above the foramen to protect the nerve from injury.
4. Bone Cutting (fig:4)     Using a bur or a saw (surgeon's preference) a horizontal cut is done above the mandibular foramen on the medial aspect of the ramus. Care should be taken to cut only the cortical bone. The cut is stopped just behind the mandibular foramen. (The most common cause for a wrong split is the extension of the cut deeper into the lateral cortical plate). The cut is then taken just medial  to the lateral oblique ridge to the horizontal ramus about 2.5 mm. below the bony cervical margin. This is brought up to the level of 2nd molar or a little anterior. (The buccal part of the bone at the horizontal ramus is thickest at the 2nd molar region). If the cut is brought too much forward chances of splintering of the buccal plate while splitting is high.     The vertical cut of the bone is done from the anterior end of the cut downward to the inferior border. (All these cuts should be done only on the cortical bone. Too much deepening of the cut on the buccal side may injure the inferior alveolar neurovascular bundle resulting in paraesthesia and bleeding).      The inferior border is cut and the cut is directed backward by about a mm. or two through the inferior border so that while splitting, there is no splintering of the bone.

Prof. (Dr) Varghese Mani, Oral and Maxillofacial Surgeon
Member Dental Council of India
Past President Oral and Maxillofacial Surgeons of India.
Consultant
Mani Specialty Clinic, MG Road, Trichur, Kerala 680004, India. Phone -- 0091-0487-385996
Trichur Institute of Head and Neck Surgery (TIHANS), Shornur Road, Trichur.

updated Aug2002.