Combined push-pull distraction for correction of syndromic midfacial hypoplasia

Gradual midfacial advancement, applying the principle of distraction osteogenesis, reduces the restriction of the soft tissues and results in bony consolidation without need for grafting. The midface can be distracted by either pushing it forward, using semiburied devices, or pulling it forward by a rigid external device. For each method there are inherent technical problems, such as controlling the vector of movement, symmetry of advancement, and differential movement of the upper/lower face. We have used a combination of the 2 methods, called "push-pull," in an effort to control the distraction process. The purpose of this paper is to describe our push-pull distraction technique and summarize our early experience.

Ten patients (5 males and 5 females) with a mean age of 11 years 2 months underwent midfacial advancement using push-pull distraction. Two orthodontists, blinded for landmark identification, traced preoperative and postoperative cephalograms and determined linear and angular measurements of midfacial position. A Student t test was used to assess differences between the cephalometric measures on the 2 radiographs. Interexaminer reliability was calculated by an intraclass correlation coefficient.

Postdistraction cephalograms were taken a mean of 10 months (range, 3 to 20 months) after removal of the devices. Patients exhibited improvement at all levels of the midface after distraction. There was a statistically significant sagittal advancement from the infraorbital rim to dentoalveolus. The central midface was sufficiently advanced as shown by an improved convexity, nasolabial angle, and upper labial protrusion. There were no significant differences between examiners for any of the measurements in this study.

Push-pull distraction permits 1) equal movement at both the upper and lower facial levels, 2) advancement of the central midface, and 3) symmetric movement of the zygomaticomaxillary complexes. This method also provides a backup, in case one device malfunctions. In combination, the advantages of each device are additive; whereas the weaknesses are not. The push-pull technique is a practical method for midfacial distraction until a better single device is fabricated.