| Cranial bone flaps are refixed to the cranium not only for cosmetic reasons but also to assure the patient's safety; visible defects cause psychosocial stigmatization and also permanent danger of mechanical damage to the unprotected brain. A fixation device must therefore not only secure primary attachment but also ensure a fast and optimal bony healing to avoid pseudoarthrosis and subsequent osteolytic changes. Formerly, the fixation of bone flaps had been performed using stainless steel wires. The introduction of computed tomography (CT), however, demonstrated extensive metal artifacts caused by these wires, which led to a worldwide shift to fixation by sutures. Mechanically, sutures can not provide a safe attachment of the bone flap to the cranium because there is no locking connection but only a low-grade connection by friction. The common problem of skull flap depression , was experienced often, particularly in cases of minimally invasive or stereotactically guided microsurgical procedurein which saw gap is relative broad. Recently, a new rivet-like titanium clamp (CranioFix) have been used to secure bone flaps and improve cosmetic and protective outcomes. The purpose of this study was to determine the time required for fixation , quality of the strength of CranioFix , as compared with stainless steel wires and sutures.MATERIALS AND METHODSSix cranial bone specimens were used for the study , which are provided by department of Anatomy, college of Medical Science, Zhejiang University. Four circular craniotomies were made in each head and 24 overall. The four locations used for the craniotomies were frontal, left temporal, right temporal and posterior parietal. The average craniotomy diameter was 6.0 cm. Three types of fixation were used for 8 cranial flap each: stainless steel wires, sutures and CranioFix. For stainless steel wire and suture fixation, three holes were drilled in each flap and in the adjacent skull edge, and were positioned apart along the circumference of the craniotomy defect and the free cranial flap. Stainless steel wire or suture were passed through the holes in the flap and the adjacent skull, then fixed. For CranioFix fixation, clamps were positioned 120?apart along the circumference of the craniotomy defect and the free cranial flap, with the inner disc placed partly in the epidural space under the bone edge. The application forceps was then placed over the free end of the pin and sequentially squeezed and released to advance the out table. After a final tightening of each element, the excess pin projecting above the outer disc was snipped off with the pin cutter. Variables recorded included the time required for fixation, maximal and meanoffset. The mechanical load-bearing tests for fixation devices were conducted with the universal test machine, a defined quasistantic mechanical force was applied to the fixed bone flap and the ratio of impression depth to the actual force was recorded automatically until failure of the fixation system. Difference in variables of each fixation device were analyzed for statistical significance by the Student-Newman-Keuls test with a significance level of P<0.05.RESULTSThe time for fixation in the stainless steel wire group was 399 ± 45 seconds, and that in suture group was 172±14 seconds, whereas the time for fixation in the CranioFix group was 94±13 seconds. The difference between the former two groups and the latter group was statistically highly significant.The maximal offset of the bone flap was found to average 2.00 ± 0.34mm for stainless steel wire fixation, and 2. 98 ± 0.36mm for suture fixation, whereas 0.30±0.18mm for CranioFix fixation. The mean offset fo the bone flap for stainless steel wire fixation was 1.32 ± 0.34mm, 2. 20 ± 0.24mm for suture fixation, and for CranioFix fixation it was 0.20 ± 0.12mm. CranioFix fixation show less offset than either stainless steel wire (p<0.001) or suture fixation (p<0.001).The results of the load-bearing tests was demonstrated: the stainless steel wire pro...
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