A COMPARISON OF SINGLE-STAGE VERSUS GRADUAL FRONTOPARIETAL ADVANCEMENT IN TERMS OF EXTRADURAL DEAD SPACE AND BONE DEPOSITION

This study was designed to investigate the differences between single- stage and gradual advancement of cranial vault in adult cats. Fifteen animals underwent fronto-parietal craniotomy including the roof of the frontal sinus. They were randomly assigned to three experimental grou ps; single-stage advancement (n = 5), gradual distraction with intact dura-bone attachments (n = 5), and gradual distraction after separatio n of the dura from the fronto-parietal bone segment (n = 5). Developme nt of an extradural dead space and new bone formation were evaluated w ith CT scans at 1, 4 and 12 weeks. After sacrificing the animals at 12 weeks, midsagittal frozen sections and decalcified coronal sections o f the heads were obtained. The single-stage advancement group develope d an extradural dead space which communicated with the frontal sinus. The advanced bone segment, which was exposed to the air-filled dead sp ace, showed bony resorption. Both groups of gradual advancement showed enlargement of the cranial cavity and frontal sinus. As the dura and brain were stretched superiorly, no extradural dead space was produced . Although the distraction gap demonstrated deposition of new bone in both gradual advancement groups, the bone formation was less pronounce d in distraction after separating the dura from the bone segment. In c onclusion, gradual distraction of a fronto-parietal bone prevents extr adural dead space formation regardless of whether the dura is kept att ached to or it is separated from the distracted bone segment. Devascul arization of the bone segment by dissecting off the dura, however, dec reases new bone formation, and thus may increase a risk of relapse.