Experts at the Morriston Hospital in Swansea have successfully used a combination of virtual and solid modelling to provide surgeons with an accurate drilling template for implanting a prosthetic ear. This process significantly reduced the time and costs associated with the more usual method of using anatomical models
Working with researchers at the National Centre for Product Design and Development Research (PDR), the surgeon and prosthetists used virtual imagery to evaluate various options for implant surgery. Once an operating plan was finalised, a template to guide the surgeon to the precise drilling sites for ear implantation was produced using stereolithography modelling and a photopolymer from Vantico, called RenShape.
‘With virtual surgical planning and RenShape stereolithography templates, we achieved the required accuracy and surgical time reduction without incurring the time and costs to produce anatomical SL models,’ said Dr Richard Bibb, Head of Medical Applications at PDR.
For the prosthetic ear implant, PDR and prosthetists began with a three-dimensional computed tomography scan. Data was used to create virtual models of the soft head tissue, the healthy ear and the bone structure at the implant site. With this information the process went as follows:
• Three-dimensional software was used to create a mirror image of the patient's existing ear.
• The ear was then virtually positioned in the correct place.
• Cylinders, representing the implants, were positioned on the virtual ear, and soft tissue was virtually removed to reveal the points at which the implants would intersect with bone.
• After checking bone quality, a virtual block was created to overlap the head and implants.
• The skull and implant cylinders were subtracted from the block to create the template design, which was produced at PDR.
• After sterilisation, the template was placed on the patient's head to indicate to the surgeon where to drill.
‘This process wouldn't have been possible without a medically approved sterilisable resin,’ said Dr Bibb.