Longterm Skeletal Stability of Mandibular Distraction Osteogenesis

Mandibular distraction osteogenesis (MDO) is an alternative technique for
mandibular lengthening to the conventional bilateral sagittal split osteotomy
(BSSO) in patients with a mandibular hypoplasia. Both methods are surgical
procedures that are performed in a combined surgical-orthodontic treatment plan.
Longterm skeletal stability after BSSO has been studied en reported in the
literature for the conventional method. Influencing factors as the amount of
advancement, type of fixation, mandibular plane (high- and low angle patients),
surgical skills and bone, muscular and soft tissue have been reported.
An advantage of MDO is the possibility to achieve a larger amount of
lengthening (>10mm), which is required in some patients with an severe
mandibular hypoplasia, e.g. syndromic patients or children. Therefore, the
chances of skeletal relapse might be increased in these patients.
Short- and middleterm stability of MDO in comparison to the BSSO-technique
shows similar skeletal stability. However, to our knowledge the longterm
stability (at least more than 5 years) of MDO has not been studied or reported
in the literature. Since this technique has become a more routine procedure in
orthognatic surgery, it is of importance to establish the longterm stability
and amounts of possible skeletal relapse. These results could lead to
recommendations to the surgical protocol and could be beneficial to future
patients.

To investigate the long term stability (> 5 yrs) in patients treated with
mandibular distraction osteogenesis (MDO) for correction of a Class
II-occlusion.
Hypotheses:
1) MDO is a technique for mandibular lengthening with comparable stability to
other commonly used techniques (BSSO)
2) High-angle patients, lengthening > 10 mm and female patients (>38°) are more
at risk for relapse than low-angle patients, lengthening < 10mm and male
patients

This is a retrospective, cephalometric study to determine skeletal stability of
mandibular distraction performed between 1999-2006. Patients will be recalled
for a cephalometric radiograph. Cephalometric tracing will be carried out using
advanced software and manual tracing by two investigators.

In our opinion the nature and extrent of burden and associated risk is minimal.
The longterm stability (at least more than 5 years) of mandibular distraction
osteogenesis has not been studied or reported in the literature. Since this
technique has become a more routine procedure in orthognatic surgery, it is of
importance to establish the longterm stability and amounts of possible skeletal
relapse. These results could lead to recommendations to the surgical protocol
and could be beneficial to future patients.