Bilateral sagittal split osteotomy
(BSSO)
Presented by
KANIMOZHIY SENGUTTUVAN
2nd year post graduate
Thaimoogambigai Dental College and Hospital

• 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

• 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.

• 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

• 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)

• 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)

• 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.

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

CONTRAINDICATIONS
• Severe decreased posterior mandibular body height
• Extremely thin medial –lateral width of ramus
• Severe ramus hypoplasia and
• Severe asymmetries

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.

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).

• The second corticotomy is made
through the buccal cortex in a vertical
direction at the level of the first or
second molar.

• 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.

• The third corticotomy connects the
first two osteotomy lines along the
anterior border of the ascending
ramus.

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.

Mobilization
• A special bone spreader can be used
to mobilize the segments

• After the bilateral split is completed
the large tooth bearing segment can
be moved three dimensionally.

• 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

• 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

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.’

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.

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.

Fixation techniques
• With wire at upper and lower border
• Lag screws/Bicortical screws
• Mini plates
• Bioresorbable plates and screws

• 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

• 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

• 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.

• 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.

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).

• 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

• 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.

• 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.

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.

• 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.

• 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.

COMPLICATIONS

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.

• 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

• 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.

• 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.

• 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.

• 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.

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.

• 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

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

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.

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

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.

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.

• The incidence of condylar resorption has
been reported at between 1% and 31%.
Resorption of Condyle

• 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.

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

• 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

• 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.

EARLY DIAGNOSIS

LATE DIAGNOSIS

(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,

NERVE CANAL IS STILL ATTACHED TO THE PROXIMAL BONE SEGMENT

RETROMOLAR BONE FRACTURE

• 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.

• 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

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.

• 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

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

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

• 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

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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