R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

182 Medical modelling
6.10 Rehabilitation applications case study 3: An
appropriate approach to computer-aided design
and manufacture of cranioplasty plates
6.10.1 Acknowledgements
The work described in this case study was fi rst reported in the reference
below and is reproduced here in part or in full with the permission of the
Institute of Maxillofacial Prosthetics and Technologists.
• Bibb R, Bocca A, Evans P, 2002, ‘An appropriate approach to computer
aided design and manufacture of cranioplasty plates’, Journal of
Maxillofacial Prosthetics & Technology, 5 (1), 28–31.
The authors would like to gratefully acknowledge Sarah Orlamuender,
Greta Green and James Mason from SensAble Technologies Inc. for their
assistance in this project.
6.10.2 Introduction
It has long been recognised in product design and engineering that
computer-aided design & manufacture (CAD/CAM) can have signifi cant
advantages over traditional techniques, particularly in terms of speed and
accuracy. These advantages can be realised at all stages from concept
through to mass production.
As these processes have become more widespread in industry attempts
have been made to transfer the technology to medical procedures. For
example, computer-aided production methods such as rapid prototyping
(RP) have been used to build highly accurate anatomical models from
medical scan data. These models have proved to be a valuable aid in the
production of reconstructive implants such as cranioplasty plates (a cranioplasty
plate is an artifi cial plate that is fi tted to the skull to restore the shape
of the head and protect the brain). Typically, RP is used to create accurate
models of internal skeletal structures, such as skull defects (1). The cranioplasty
plate is then handcrafted in wax on the model by the prosthetist (2,
3, 4). Alternatively, the anatomical model can be used to create moulds or
formers (5). Although this process has dramatically improved the accuracy
of cranioplasty plate manufacture, it incurs signifi cant time and cost to
produce the anatomical model. This current route does not fully exploit the
potential advantages of an integrated and optimised CAD/CAM process.
The major impediment to the application of CAD in prosthetics design
is the fact that it requires the integration of existing anatomical forms with
the creation of complex, naturally occurring, freeform shapes. Until recently,
CAD has been driven and developed specifi cally to defi ne geometry for
engineering processes and consequently the way they operate makes it