Page 133 - Clinical relevance of current materials for cranial implants
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                                Resection templates with 3D virtual planning
DISCUSSION
This study reports the use and accuracy of resection templates and control template in cranial reconstructions. Cranioplasty with autologous bone has a relatively high complication rate. Resorption and infection are the most mentioned complications in literature, that lead to removal of the cranioplasty1,3,4. One-stage reconstruction can reduce postoperative complications, due to an accurate fit of the PSI, avoidance of a second procedure, and a reduction in overall operating time.
A representative case of a total resection of an ossifying meningioma and reconstruction
with a PEEK PSI in a one-stage surgical procedure using a resection template is
described in detail. This technique has been developed to reduce the burden on the
patient. Since only one surgical procedure is required, hospitalisation time is reduced
and no helmet needs to be worn during revalidation. During surgery, this technique
prevents extensive intra-operative positioning, achieves an accurate PSI fit (absolute 6 mean difference <1.0mm), and seems to reduce operation time. In this case, after three
years, no complications were observed and the aesthetic result was satisfactory.
The procedure is relatively new, although similar techniques are described in literature5–8. In this study, the resection outline of the meningioma was virtually preplanned according to the CT-scan. Other studies describe intermediary steps. For example, the craniectomy of the affected bone is pre-planned on a plaster head phantom based on a CT-scan. This allows the surgeon to draw the outline of the desired resection on the phantom5. Other surgeons perform the craniectomy on the gypsum phantom, acquire a CT-scan of the phantom with the defect, and a silicon mold is created based on this CT-scan6.
The use of the indirect molding technique is well described in the literature. With the use of a CT-scan and mirroring technique a mold of different materials can be created6,7. Different techniques to fabricate the final PSI are mentioned. Poly (methyl methacrylate)(PMMA) can be mixed by hand intra-operatively and casted into the mold. Post-processing of the implant on the operating room is required because the burrs will prevent a good fit. Due to limitations in the operating room, post-processing is performed with a surgical knife7. The preoperative manufacturing of PSI of PMMA is also described8. This reduces the aforementioned limitation, yet still often is fabricated by an indirect molding technique9.
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