Page 127 - Clinical relevance of current materials for cranial implants
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Resection templates with 3D virtual planning
INTRODUCTION
The skull is a complex part of the skeleton, with convex and concave areas. It protects the brain from external impact and can be seen as the base for the facial skeleton. During decompressive craniectomy, a part of the cranial vault is removed for surgical access to reduce intracranial pressure caused by trauma, tumor, haemorrhage and empyema1.
The removed part of the cranial vault can be re-inserted immediately after decompressive craniectomy. In some cases this is not possible because of swelling or
increased intra-cranial pressure. In this situation the cranial reconstruction will be
performed at a later stage, when the patient is neurologically stable2. Resorption and
infection are frequently seen in cranial reconstruction, which makes removal of the
affected cranial vault necessary3. The remaining defect may cause both functional and
aesthetic problems, making reconstruction necessary. Ideally, the appropriate cranial 6 reconstruction does not affect the patient’s anatomy, thus ensuring optimal fit and
contouring.
The design of a patient-specific implant (PSI) can be based on the patient’s Computed Tomography (CT) data, using computer-aided design, manufacturing and surgery (CAD/CAM-CAS). Small inaccuracies in the design can lead to an impaired intra- operative fit. CAS aims to predict and mitigate intraoperative obstacles, ensuring an optimal fit of the PSI. If removal of the autologous bone is required, the original outline of the cranial defect may be difficult to predict. An example is the presence of persistent bony bridges in case of partial resorption of the autologous bone flap (Figure 1A). A resection template may be used to create a predetermined outline (Figure 1B and 1C).
Figure 1: CT axial slice with A) resorption of autologous bone B) resection outline C) planned resection template.
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