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NESPS 27th Annual Meeting Abstracts

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The Evolution of Mandibular Distraction: Device Selection
Edward H. Davidson, MA MBBS, Daniel Brown, MD, Pradip R. Shetye, BDS MDS MOrthRCS DDS, Aina VH Greig, FRCS PhD, Barry H. Grayson, DDS, Stephen M. Warren, MD, Joseph G. McCarthy, MD.
New York University, New York, NY, USA.

BACKGROUND:
Mandibular distraction has evolved from the utilization of external to intraoral and to semiburied devices. The purpose of the present study is to highlight the evolution of the semiburied technique of mandibular distraction and make recommendations about device selection based on our clinical experience of the advantages, limitations and perioperative events associated with each device.

METHODS:
A retrospective review was conducted of patients undergoing mandibular distraction at NYU Langone Medical Center from our introduction of mandibular distraction in May, 1989 to June 30, 2009. We evaluated advantages and limitations for external and semiburied techniques to establish the indications for selection of the different devices. Perioperative events were stratified into three groups: a minor incident is defined as a perioperative event that does not lead to an adverse outcome and can be resolved with or without noninvasive therapy (e.g. pain); a moderate incident is defined as a perioperative event that could result in an adverse outcome but can be resolved with invasive therapy or return to the operating room (e.g. device dislodgment); a major incident is defined as a perioperative event that results in an adverse outcome and did not resolve or could not be resolved with invasive therapy (e.g. fibrous union).

RESULTS:
A total of 211 mandibular distraction procedures were performed (129 external procedures on native bone, 37 external procedures on grafted bone, and 45 semiburied procedures on native bone).
Clinical Experience: The external device is advantageous in distraction of the severely hypoplastic mandible and also enables multiplanar distraction but is limited by the associated scar burden and the psychosocial sequelae associated with a prominent facial prosthesis. Furthermore, the greater torque upon activation with this device, coupled with an inherent vulnerability to trauma, renders external devices with a greater risk of dislodgement. A semiburied device has the advantages of reduced visibility, reduced scar burden and greater ease of obtaining vertical vector. However, its use requires more bone stock (a mandibular width greater than 12mm) and it has the disadvantage of requiring a second operation for removal.
Perioperative incidents: Minor incidents were more common with the semiburied device (62%) compared to external devices on native (26%) and grafted (38%) bone. There were fewer moderate incidents with the semiburied device (18%) than the external device on native (22%) and grafted (30%) bone. In contrast to the external technique, no major incidents were seen with semiburied distraction.
CONCLUSIONS:
The semiburied distraction technique is a safe and reliable procedure for lengthening of the hypoplastic mandible. The choice between distraction techniques is dependent on the volume of mandibular bone and the desired vector of distraction. Our recommendation would be that a semiburied device is indicated in single plane distraction (especially a vertical vector) of native bone. Conversely, where bone stock is inadequate for placement of the semiburied device, such as in grafted bone, or when distracting with multiple vector planes, an external device should be used. When using external devices a greater scar burden and the risk of device dislodgement should be anticipated.


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