Stoppers in Red II Distraction Device: Is it Possible to Prevent Pin Migration? Mehmet Emin Mavili, I . brahim Vargel, and Go ¨ khan Tunc ¸ bilek Ankara, Turkey Distraction osteogenesis has become popular for the treatment of hypoplastic congenital craniomax- illofacial anomalies. Rigid external distraction (RED II) after Le Fort III osteotomy was shown to be a highly effective treatment for the management of midface hypoplasia. This device is used with a halo vest, which is placed at the cranial equator. Intracranial penetration of the fixation pins of the halo is one of the complications of an external dis- traction device. To prevent pin penetration in rigid external distraction, the authors designed polylactic acid/polyglycolic acid (PLA/PGA) plates that were circular; the plates were 0.8 cm in diameter and had 1.5-mm holes in the center, through which the tip of the pins would pass. To quantify the applied torque by manual tightening of the screws of the distraction device and to measure intraosseous cone depth created by the penetration of the conical part of the screws with and without the PLA/PGA composite stopper, first an in vitro experiment was undertaken on cadaver. Then these PLA/PGA plaques, or stoppers, were placed over the bone surfaces of the cranium of the patients where the tip of the pins press. PLA/PGA stoppers are mal- leable and adapt their shape to the interactive forces between bone and the pins. They act as a second barrier, and spread the pressure of the screws to larger surfaces, thus securing better sta- bilization. The penetration of wider portions of the screw into scalp is reduced, minimizing the scalp damage caused by the screws. Biodegradable and biocompatible PLA/PGA stoppers avoid intra- cranial migration of the fixation pins, especially in children. D istraction osteogenesis has become popular for the treatment of hypoplastic congenital craniomaxillofacial anoma- lies. Rigid external distraction was intro- duced for maxillary hypoplasia associated with cleft palate by Polley and Figueroa. 1 Then it was applied to more complex craniofacial deformities that re- quire Le Fort III osteotomy. The advantages of using a halo distraction could be summarized as (1) more precise positioning and effective traction of the bony segments, (2) better vector control of these osteoto- mized segments, and (3) the ease of the application and removal the distraction device. Rigid external distraction (RED II) after Le Fort III osteotomy was shown to be a highly effective treatment for the management of maxillary hypoplasia. This device is used with a halo vest, which is placed at the cranial equator. However, this technique has its own risks and complications. Common complications of the use of a halo have been reported to be pain, loosen- ing of the pins, soft tissue infection, and scarring around the pins. Less common but more serious complications are penetration of pins to the skull, intradural/extradural abscesses, and osteomyelitis of the skull. Intracranial penetration of the fixation pins caused by the use of an external distraction de- vice has been described. 2–14 In the current report, we describe a technique designed to prevent intracranial migration of halo fixation pins used in RED II distraction. CADAVER STUDY Torque Tests and Measurement of Intraosseous Cone Depth T o quantify the applied torque by manual tight- ening of the screws of the distraction device and to measure intraosseous cone depth created by the penetration of the conical part of the screws with and without the polylactic acid/polyglycolic acid (PLA/PGA) composite stopper, an in vitro experi- ment was undertaken on cadavers. The face-bow part of the device was secured to the skull between the bilateral temporal bones by manually tightening From the Department of Plastic and Reconstructive Surgery, Faculty of Medicine, Hacettepe University, Ankara, Turkey. Address correspondence to Dr. I . brahim Vargel, I . no ¨nu ¨ mah, 85, Sokak, Gu ¨ nes ¸kent Sitesi No. 4/7 Batıkent, Ankara, Turkey; e-mail: ivargel@hacettepe.edu.tr. 377