Intracranial migration of microplates versus wires in neonatal pigs after frontal advancement

Several case reports have demonstrated that microplates migrate intracranially when used in the reconstruction of the neonatal craniofacial skeleton. We conducted a study to analyze the validity of this finding, to calculate the rate of intracranial plate migration, and to compare the migration of microplates to standard surgical wire. We hypothesized that, because of constant bone generation and resorption in the developing cranial skeleton, both microplates and wires would migrate and resorption in the developing cranial skeleton, both microplates and wires would migrate intracranially. Bilateral supraorbital osteotomies were performed in five 6-week-old Yucatan minipigs. The right side was repaired by fixating the bone segment with 32-gauge stainless steel wire. The left side was fixed with two microplates (Leibinger Corp, Dallas, TX). The pigs were monitored for 6 months. During this time each pig was injected with a fluorescent bone dye on the first day of each month. One pig was killed at 3 months and used for midpoint comparison. We found that both microplates and wires migrated intracranially in these neonatal pigs. None of the plates or wires penetrated the dura, but several pieces of hardware from each group migrated far enough to rest directly on the dural surface. The rate of plate and wire migration also varied slightly among animals, but the mean rate remained relatively constant at 0.91 mm/month. Computed tomographic scans and morphometric analysis revealed no significant difference between the fracture healing and facial growth of the microplate and wire sides. We conclude that the biology of bone deposition in the calvarium causes any stationary foreign body on the surface of the skull to migrate intracranially in the neonate.