Distraction osteogenesis is a procedure that
uses the healing process that occurs between surgically osteotomized bone
segments and is also a prominent aspect of reconstructive surgery. Osteotomy
indicates the incision or transection of a bone.
The surgical therapy is divided into
presurgical phase, operative phase, lag phase, distraction phase, consolidation
phase, and retention phase.
In presurgical phase, based on the
radiographic studies, the orthodontist determines whether an internal or
external device is more suitable for the procedure and the vector of the
distraction.
 |
| Mandibular Fracture |
In operative phase, the mandibular distraction
can proceed when there is enough mandibular bone stock must be available for
the osteotomy and placement of the device. The choice between the use of internal
and external device is made mostly based on the degree of bony and soft-tissue
exposure for placing the device to make maxillary-mandibular opening. The
external devices facilitate multidirectional control of the distraction of
which the internal devices are not capable. On the other hand, the external
devices require multiple skin incisions which may derive facial scars. Either
devices can navigate the distraction vector. To avoid injury to the inferior
alveolar nerve and the developing dentition during the procedure, perpendicular
osteotomy line is demanded. The placement of the distractor before the making
the osteotomy can prevent the mobility of the proximal segment. The surgeon
employs standard principles of a sagittal split osteotomy when lengthening the
mandibular body. The nerves are preserved by using a reciprocating saw (fig 3) for the
buccal corticotomy (fig 4), and the lingual cortex (fig 1) is fractured with an osteotome (fig 2).
Patient will feel discomfort until fracture is completed.
In lag phase, there is a latency period to
allow for initial bone formation to happen. This phase endures for average 3~5
days. However, patients with skeletal maturity, the latency period lasts for
5~7 days.
In distraction phase, the bone segments are
gradually pulled apart using either an internal or external device. The rate of
distraction is normally set to 1.0mm per day. Exceptionally, for infants, the
rate is intentionally accelerated to 2.0mm per day to prevent early
consolidation and for elders, the rate is decelerated to 0.25~0.5mm per day.
The distraction can occur at once or in several increments throughout the day
depending on the rhythm or frequency of distraction. Based on the patient’s
demographics, the total time of the distraction phase is customized.
In consolidation phase, once the anticipated
bone length is approached, the mineralization of the immature bone occurs. The
distracting appliance is fixed into place to provide stability until the
immature bone has adequate strength to sustain. This phase varies in time, but
in average, it takes 6~8 weeks.
In retention phase, the device is removed.
This step may require occlusal splints to guide the maxilla into position when
the leveling of the mandibular cant creates a posterior open bite.
[Reference]
https://en.wikipedia.org/wiki/Distraction_osteogenesishttps://en.wikipedia.org/wiki/Corticotomy
http://medical-dictionary.thefreedictionary.com/osteotomy
http://emedicine.medscape.com/article/1280653-treatment
KSJ
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