Publication

Development and Validation of Bone Surrogates for Tabula Externa Graft Lift Training

Publication, 2017

Outline

M. Hollensteiner - Development and Validation of Bone Surrogates for Tabula Externa Graft Lift Training - Phd Thesis, Paracelsus Medizinische Privat Universität Salzburg, Austria, 2017

Abstract

To avoid injuries of the patient during standard bone machining procedures a surgeon has to apply appropriate forces and speeds with the surgical instruments. Extensive training would be necessary to maintain a high quality health care system. Traditionally the education happens by watching a surgical procedure and gaining first hands-on experience under supervision of an experienced surgeon or during training on human and animal specimens, live animals and simulators. The risk for the patient during “first hands on” surgeries led to the development of new training tools. Model-based simulators with a sufficient degree of realism, either haptical and anatomical provide a safe training environment for surgical trainees. Taking grafts from the skull vault is an accepted standard practice and popular in facial-skeletal surgery to treat traumatic, reconstructive and even cosmetic deformities. Machining instruments are typically used to harvest these calvarial grafts. To reach a high degree of accuracy of an artificial skull model artificial bones were biomechanically validated. Measurements with real machining tools, penetrating all bony layers, were performed on autoclaved human parietal bone specimens. The skull layers were penetrated perpendicularly while forces were recorded. Based on these results appropriate materials for artificial skull bones were developed. First, two-layered blocks were created and tested. Second, a manufacturing process was determined and three-layered skulls were manufactured and tested to exclude material property changes due to the manufacturing process. Micro-computed tomography was used to determine the cortical and cancellous bone layer thickness of human and artificial bones. These measurements were also used as a reference to adjust the bone layer thickness in the manufacturing process. A suitable skull-cap model was covered with an artificial scalp. Within a pilot study, this model-based simulator was tested by experienced surgeons. Appropriate material mixtures for artificial parietal bones were identified based on penetration measurements on autoclaved human specimens. The artificial skull caps which were made of these materials were able to mimic human bone layers. Apart from the milling the artificial bone provided a realistic tactile feedback during surgical machinal instrumentation in comparison to the human reference. All procedural steps could be performed realistically with the simulator as reported by the surgeons. Both surgeons confirmed the suitability of the prototype as a valid educational tool for surgical residents. In conclusion, an artificial bone has been created which reflected the properties of human parietal bone and thus is suitable for tabula externa graft lift training. The grafting simulator presented in this study can contribute to the education of surgeons performing grafting procedures on the human parietal bone.