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  1. Bilateral sagittal split osteotomy (BSSO) Presented by KANIMOZHIY SENGUTTUVAN 2nd year post graduate Thaimoogambigai Dental College and Hospital
  2. • Bilateral sagittal split osteotomy (BSSO) of the mandible is one of the most frequently performed surgical procedures. • This is a very popular, most versatile procedure performed on the mandibular ramus and body. • First described by Obwegeser and Trauner and later modified by Dal Pont, Hunsuck and Epker. INTRODUCTION
  3. • The osteotomy splits the ramus and the posterior body of the mandible sagittally, which allows either setback or advancement. • This is a highly cosmetic procedure, as it is done intraorally. • For mandibular advancement, there is no need for bone grafts. • Thus donor site morbidity and second operative site for the bone graft is totally avoided. • BSSO gives excellent results. Only drawback is the technique demands high level of operative skill and experience to minimize the surgical complications.
  4. • In 1957, Obwegeser and Trauner first described the sagittal split osteotomy of the ramus region, only by placing buccal and lingual cortical horizontal cuts. • The procedure has undergone numerous modifications over the years. HUGO OBWEGESER & TRAUNER 1957 HISTORY
  5. • In 1961, Dal Pont changed the lower horizontal cut to a vertical cut on the buccal cortex between the first and the second molars, thereby obtaining broader contact surfaces and requiring minimal muscular displacement with improved access. DALPONT (1961)
  6. • In 1968, Hunsuck further modified the technique, advocating a shorter, horizontal medial cut, just posterior to the lingula, to minimize soft tissue dissection. • His anterior vertical cut was similar to Dal Pont’s. HUNSUCK (1968)
  7. • In 1977, Epker suggested several modifications. • These include minimal stripping of the masseter muscle and limited medial dissection. • These modifications helped to reduce postoperative swelling, oedema, haemorrhage • Epker et al described completing the osteotomy through the inferior border of the mandible.
  8. INDICATIONS 1.Mandibular deficiency -with normal or short face, -with long face- increase maxillary vertical dimension -excessive chin height -for correction of sleep apnea Limitation- Additional surgery for most dentofacial deformity 2.Mandibular prognathism Limitation -Large setbacks of more than 7 -8 mm, IVRO/ inverted L osteotomy should be considered 3.Mandibular asymmetry - Hemi mandibular hypertrophy -Hemi mandibular elongation 4. Open bite 5. Cross bite
  9. CONTRAINDICATIONS • Severe decreased posterior mandibular body height • Extremely thin medial –lateral width of ramus • Severe ramus hypoplasia and • Severe asymmetries
  10. Surgical procedure Incision & Dissection • The incision begins at the anterior aspect of the ramus at a midpoint between upper and lower molars. • The incision is about 2 cm long. • It runs down the lateral crest of the external oblique ridge and ends in the facial vestibule at approximately the first molar region. • After sharp dissection of the mucosa, the buccinator muscle over the ramus is dissected off at its medial aspect so as to keep as much soft tissue laterally as possible. • Then, the cut is completed through periosteum to bone.
  11. Osteotomy cut • The procedure starts with three corticotomies. • The first cut is made through the lingual cortex just above the mandibular foramen parallel to the occlusion. • The corticotomy is extended from the anterior border of the ramus to just behind the entrance of the inferior alveolar canal (lingula).
  12. • The second corticotomy is made through the buccal cortex in a vertical direction at the level of the first or second molar.
  13. • We place the vertical cut at the horizontal ramus between the first and second molars and extend it downward to the inferior border, curving around it. • Cortical bone below the second molar is thick; this thickness protects the neurovascular bundle. • Nevertheless, the neurovascular bundle lies just below the cortical bone; thus, the osteotomy is required to go only through cortical bone.
  14. • The third corticotomy connects the first two osteotomy lines along the anterior border of the ascending ramus.
  15. The sagittal split • The final split is completed with a thin osteotome, splitting the entire ascending ramus from the anterior to the posterior border of the ramus.
  16. Mobilization • A special bone spreader can be used to mobilize the segments
  17. • After the bilateral split is completed the large tooth bearing segment can be moved three dimensionally.
  18. • Once the osteotomy has been completed on both sides, a prefabricated interocclusal acrylic wafer splint is placed. • We achieve maxillo-mandibular fixation (MMF) with three wire ligatures. • Some centers do not use an occlusal wafer splint. • In this case, the teeth must be placed in good three-point contact for a stable MMF to avoid any shift when screws or plate and screws are set. Positioning of the tooth bearing segment
  19. • Care must be taken to maintain the normal fossa-condyle relation (see upper insert) and to avoid condylar displacement (see lower insert). • Usually this is achieved by manual positioning of the condyle bearing segment superiorly into the glenoid fossa Positioning of condyle bearing segment
  20. A. Custom splint that lies along the lateral surface of the maxillary teeth is placed before osteotomy. The splint has a guide wire attached, extending along the lateral surface of the ramus. A saw is used to score a groove in the bone along this guide wire. B. After the osteotomy, the distal segment is wired into the final splint (MMF). The condylar positioning splint is reapplied and alignment of the scored mark in the ramus with the guide wire is examined. In this illustration, the ramus has rotated counterclockwise. C. The ramus can be rotated around the condyle until the scored groove aligns with the guide wire. Fixation between the proximal and distal segments can then be performed. Condylar positioning technique described in 1976 by Leonard.’
  21. Condylar positioning device connecting the maxillary dentition to the ramus with a stiff wire. A.Placement of device before osteotomy. The device is removed, the osteotomy performed, and the distal segment wired into the final splint (MMF). B. The positioning device is replaced and fixation between the proximal and distal segments can be performed. Such devices prevent rotation of the proximal segment but do not provide three-dimensional control.
  22. Condylar positioning technique that produce three-dimensional control of the proximal segment. A.A bone plate is adapted and secured between the proximal segment and zygomaticomaxillary buttress. The screws in the buttress are removed, the osteotomy performed, and the distal segment wired into the final splint (MMF). B. The screws are then replaced in the buttress, repositioning the ramus into its preosteotomy position.
  23. Fixation techniques • With wire at upper and lower border • Lag screws/Bicortical screws • Mini plates • Bioresorbable plates and screws
  24. • In the past, osteosynthesis was achieved with upper border wire, lower border wire, or circum-ramus body wire. • Today, this inveterate method is no longer justifiable for use on a routine basis because MMF is mandatory for weeks following surgery with this type of fixation. UPPER AND LOWER BORDER OR CIRCUM-RAMUS WIRING
  25. • Lag screws are indicated only when passive bone contact with no tension or torque to the condyle is sufficient. • Two or three 2.0-mm position screws are used for stabilization. • These are placed transorally at the superior border of the osteotomy site. Lag Screws/ position screws
  26. • It is important to place the first screw where bone contact is sufficient and passive with no tension, to avoid displacement of the condyle. • The proximal segment is positioned slightly into the fossa and is held with a ramus pusher.
  27. • For placement of a 2.0-mm screw, a 1.5-mm drill hole is positioned through the proximal and distal segment. • The two segments must be kept aligned and are held together as the first hole is drilled with a 1.5-mm wire-passing bur. • Then, a 2-mm self-tapping screw engages both segments of cortical bone.
  28. Osteosythesis With Miniplates • Fixation can be accomplished by bridging the osteotomy with a bone plate. • Usually, a four-hole bone plate with two screws on each side of the cut is sufficient for stable fixation. • Self retaining monocortical screws provide adequate stability. • The plates we use are 2.3-mm rigid standard titanium plates (Martin).
  29. • More flexible plates such as low-profile plates with 1.8- mm diameter do not provide enough strength for function. • Therefore, if we use non-rigid plates for fixation, we add a second plate or position screws to give additional stability. • Usually, two screws on each side of the cut is sufficient. • In unusual splits (bad splits), it is sometimes necessary to use longer plates to stabilize the osteotomy. • After the segments have been stabilized
  30. • Before the osteotomy site is closed, it is wise to proof the occlusion. • Therefore, the MMF is released, the splint is removed, and functions such as extent of mouth opening and left and right lateral and protrusive functions are checked and compared with original data.
  31. • The need for screws or plates and screws is temporary until the sagittal split has healed. • Some centers remove metallic hardware on a routine base; others do so only if symptoms are present. • The wounds are then irrigated meticulously with saline. • For wound closure, we use a 4.0 non-resorbable suture in a horizontal mattress suture technique; this suture is removed 10 to 12 days after completion of surgery.
  32. Osteosynthesis With Resorbable Fixation Implants • The use of biologically inert resorbable implants eliminates the need for a second operation to remove fixation material. • Polyglycolic acid, polylactic acid, and polyester polyparadioxanon are organic macromolecular compounds that are degradable and absorbable by the body.
  33. • These compounds possess physical properties such as rigidity and tensile and flex strength that are necessary for their use as internal fixation devices in orthognathic surgery. • As experiments have shown, the degradation process in itself does not imply immediate absorption of an implant.
  34. • About 70% of the material in the implant (depending on the material) remains in situ for about 3 months before the degradation process starts. • The rate of degradation is dependant on several factors: molecular weight, crystalline, and thermal history and geometry of the implant.
  36. Injury to the Inferior Alveolar Nerve (IAN) • Postoperative neurosensory deficit generally is considered to be caused by mechanical damage of the IAN (open injuries). • Even in cases in which the IAN is not visibly traumatized during surgery, postoperative neurosensory deficit can occur (closed injury). • This may result from edema, hematoma, or direct damage to cancellous bone fragments after stabilization or incorrect placement of screws.
  37. • Nerve injuries are described clinically as “open” or “closed.” • Open injuries are those observed by the surgeon at the time they occur. • Immediate primary repair by suturing of the nerve guarantees the best result. • Closed injuries are not visualized at the time of their occurrence (e.g., laceration of nerves by osteosynthesis screws), and they may or may not be suspected. • Closed injuries are followed by repeat examination every 4 weeks. • If unacceptable loss of sensation or painful or unpleasant sensation occurs, microsurgical repair is the only way to regain sensation of the nerve
  38. • The IAN is occasionally lacerated during osteotomy at the site of its entrance into the mandible. • This can be prevented by protecting this site during osteotomy with a freer. • Lesions of the IAN in the anterior vertical part of the osteotomy are most often due to the close relationship of the mandibular canal to the lateral mandibular cortex in the second molar. • The risk for neurosensory disturbance is significantly greater if the distance between the mandibular canal and the buccal cortex of the mandible is 2 mm or less.
  39. • Tear of the IAN can be the consequence of forced manipulation during the splitting process. • To avoid this, only rotating instruments and saws may be used to open the mandibular cortex. • Therefore, the osteotome may penetrate only very superficially into the mandible during splitting.
  40. • The IAN is variable with respect to its anatomic location in the mandible. • However, some mandibular deformities seem to be associated with certain abnormal locations of the IAN. • The presence of an unerupted third molar during surgery has been proposed as a factor that increases the risk of neural deficit. • In addition, roots of third molars are frequently located close to the mandibular canal and tear the nerve upon mobilization.
  41. • Paresthesia is an expression of increased manipulation that is performed if the neurovascular bundle has to be dissected from the proximal segment or released from the bone canal in the proximal segment.
  42. Injury to the Lingual Nerve • Occasionally, a temporary disturbance of the lingual nerve occurs. • Two well-known reasons have been put forth for lingual nerve disturbance: bicortical screw placement and pressure of a hematoma at the lingual side of the mandible. • Bicortical screws that are placed near the superior border of the mandible in the region of the third molar must not extend beyond the inner cortex of the mandible because they may damage the lingual nerve in this region.
  43. • Hematoma following severe bleeding at the inner side of the mandible exerts pressure on the lingual nerve. • This can lead to temporary paresthesia of the tongue that is characterized by sensible defects of the affected side of the tongue
  44. Displacement of the Condyle • Failure to seat the proximal segments properly into the fossa during surgery may result in condylar displacement. • This is the main reason for TMJ symptoms after BSSO • Rotation of the proximal segment • Condylar sag • Condylar torque
  45. Condylar Sag • Condylar sag can be defined as an immediate or late caudal movement of the condyle in the glenoid fossa after surgical establishment of a pre-planned occlusion and rigid fixation of the bone fragments, leading to a change in the occlusion.
  46. CENTRAL CONDYLAR SAG • In central condylar sag, the condyle is positioned inferiorly in the glenoid fossa and makes no contact with any part of the fossa • After removal of the IMF and in the absence of intracapsular edema or hemarthrosis (causing hydraulic pressure), the condyle will move superiorly after removal of maxillo-mandibular fixation, leading to a malocclusion
  47. PERIPHERAL CONDYLAR SAG - I • Two types of peripheral condylar sag may occur. • In Type 1, the condyle is positioned inferiorly, with some fossa contact (lateral, medial, posterior, or anterior) with the maxillo-mandibular fixation in position (teeth in occlusion) and rigid fixation placed. • This type of condylar malpositioning provides physical support to the occlusion. • Postoperative resorption or change in condylar shape will lead to late relapse.
  48. PERIPHERAL CONDYLAR SAG - II • In Type II, the condyle is positioned correctly in the fossa with the maxillo- mandibular fixation in position (teeth in occlusion); however, with the placement of rigid fixation, a torqueing force is applied to the condyle and ramus of the mandible. • The tension on the ramus is released when the maxillo-mandibular fixation is removed, and the condyle will move either laterally or medially and slide inferiorly in the fossa.
  49. • The incidence of condylar resorption has been reported at between 1% and 31%. Resorption of Condyle
  50. • Predisposing factors for condyle resorption include the following: • High mandibular plane angle, condyle with posterior inclination, and a low posterior-to-anterior face/height ratio are predisposing skeletal factors for condylar resorption. • Contributing are surgical factors such as counter-clockwise rotation of the proximal segment, preoperative TMJ dysfunction, and vascular necrosis of the condyle that occurs as a consequence of traumatic stress during surgery. • Proper positioning of the proximal segment into the fossa after the mandible is split is of utmost importance for avoiding postoperative TMJ problems such as condylar resorption.
  51. UNFAVORABLE BONY SPLIT • Poor split of the distal segment most often affects the lingual cortical bone posterior to the third molar. • This may result in sequestration of the fragment, delayed union, malunion of the osteotomy site, or even infection. • Stabilization of the unfavourable fracture prevents postsurgical instability. • Unanticipated splits of the proximal segment may occur before or after splitting of the mandible
  52. • Often, the reason for a poor split is improper wedging with osteotome, especially in cases where bone is used as a fulcrum during splitting. • Therefore, careful inspection of the inferior border and the outer cortex is mandatory. • Predisposing factors include • difficult anatomy, • poor osteotomy design, and • the presence of impacted third molars. • Anatomic features such as width and thickness of the ascending ramus and the relationship between positions in the canal have to be studied previously. • Lack of cancellous bone between the two cortical bone layers makes the split more difficult
  53. • Correct cuts through cortical bone with the use of a reciprocating saw or a bur are essential for avoiding a bad split. • This is especially true for the cut at the inner side of the ascending ramus and the inferior border prior to application of the chisel to the osteotomy. • An increased risk of unanticipated fracture during BSSO has been associated with the presence of impacted third molars, which have been postulated to compromise the anatomic structure of the mandible, causing adverse proximal and distal segment splits. • Stabilization is more challenging than in non-fractured splits, and more osteosynthesis material is required. • Plates, bicortical screws, or a combination of these can be used to stabilize fractured bony segments.
  56. (a)The buccal cortex fractures separately from the lower border, while the fracture runs superiorly toward the coronoid notch. The splitting maneuver is stopped and the lower border captured to form part of the proximal segment. (b) The buccal cortex fracture continues superiorly and includes the coronoid process. The buccal osteotomy is redefined and the lower border captured. Rigid fixation is achieved using a bone plate and by securing the fractured cortex by means of bicortical screws,
  59. • Reason for bleeding in this phase is inadvertent laceration of the masseter muscle during incision of the vestibular mucosa. • This can be avoided by meticulous cutting of the mucosa all the way through to the periosteum. HEMORRHAGE • Uncontrolled hemorrhage is a rare condition in mandibular surgery. • It occurs in most cases as the consequence of clumsy use of rotating instruments or chisels, which reflects obvious inexperience of the surgeon in performing the surgical procedure. • Bleeding from the pterygoideus medialis muscle may occur during osteotomy at the lingual surface of the ascending mandibular ramus, if the periosteum is not completely released from the bone.
  60. • Bleedings from the facial artery may occur during removal of soft tissue from the mandibular border; this must be treated with a suture. • Bleeding from the inferior alveolar artery can occur when bone fragments after osteotomy are separated via forced use of a bibeveled osteotome. • This complication can be avoided by a cautious split performed under good vision. • This can be achieved by placement of the suction tip into the bottom of the split. In addition, careful preparation and release of vessels (and nerves) from the proximal fragment is necessary
  61. INFECTION • Wound dehiscence and/or infection is now a rare complication and is most often related to poor oral hygiene. • Tobacco smoking seems to be an additional risk factor. • Contributing factors include long duration of the surgical procedure, the patient’s age, the presence of foreign bodies, sequestering after bone fracture, and hematoma. • The mandatory use of prophylactic antibiotics during and after surgery has substantially reduced the risk of infection.
  62. • Relapse is a multifactorial problem that cannot be attributed to a single cause. • Proper diagnoses, adequate treatment planning, correct and skillful surgical technique are essential contributions of the surgeon. • Soft tissue and muscle tension may influence postoperative stability. • Factors that have an effect on relapse include type of fixation, magnitude and type of mandibular movement, position of proximal segment, and disk displacement. Relapse
  63. Stability depends on : • Adequate presurgical orthodontics. • Long-term maxillomandibular fixation (MMF). • Non-rigid fixation that allow muscular adaptation. • Minimal muscle alteration, Good bony contact, and control of the proximal segment
  64. Factors : • Magnitude of mandibular advancement or setback, • Stretch of surrounding soft tissue, • Positioning of mandibular condyles • Method of fixation • Growth of mandible • skeletal behaviour among hyper/ hypo divergent skeletal patterns
  65. • Obligate relapse after mandibular advancements >7mm • Mandibular setback >12 mm - skeletal relapse • Closure of anterior open bite with only mandibular osteotomies How to reduce/avoid : • Counter-clockwise rotation of the mandible be avoided • Mandibular advancement limited to < 7mm • Bimaxillary surgery
  66. REFERENCES • FONSECA -Oral and Maxillofacial Surgery, Second edition Volume 3, Orthognathic surgery Esthetic surgery. • Johan P. Reyneke, Essential of orthognathic surgery • Textbook of Oral and Maxillofacial Surgery, Third Edition- Neelima Anil Malik. • Intraoperative diagnosis of condylar sag after bilateral sagittal split ramus osteotomy, Johan. P. Reyneke, C. Ferretti , British Journal of Oral and Maxillofacial Surgery (2002) 40, 285–292 • Condylar Positioning Devices For Orthognathic Surgery, EDWARD ELLIS III, DDS, MS, J Oral Maxillofacial Surgery 52 536.552(1994).
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