R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

6.54 The result of the Boolean subtraction.
Case studies 187
from the wax to leave a freeform shape that would repair the defect as
shown in Fig. 6.54. To allow the implant to be inserted from the outside of
the skull, the inner edges of the plate were worked back as shown in Fig.
6.55. The fi nal shape can then be accurately fabricated using RP techniques.
This can then be used as a pattern from which an implant can be made
using an appropriate material.
In this case, a highly accurate stereolithography model was made of both
the implant and the defect to test the design for fi t and accuracy, see Figs.
6.56 and 6.57. In this case, the fi t was excellent and comparable to the results
achieved when using stereolithography models and traditional wax up
methods. The stereolithography resin used is approved for patient contact
under theatre conditions, which will allow the plate to be test fi tted to the
actual defect at the time of surgery. However, the material is not approved
for implantation and so the actual implant used will be cast from the stereolithography
master into an approved acrylate.
6.10.4 A second case study
This case followed similar techniques to the initial case yet proved more
challenging due to the complex nature of the implant required. The added
complexity further illustrated the potential benefi ts of utilising this approach.