Generic Asian Pelvic Bone Model

A 50-piece zero series of the world’s first evidence-based anatomical model of the Asian pelvis is now in production and will be demonstrated at the AO Davos Courses 2018 in December. Funded by the Strategy Fund, the two-year project was made possible by the strong three-way partnership between the AO Research Institute Davos (ARI), SYNBONE AG, and the University of Malaya.

With Asia today representing approximately 60 percent of the global population and trauma being the most prevalent orthopedic problem in developing countries, the Generic Asian Pelvic Bone Model project has the potential to meaningfully contribute to the training and education of orthopedic trauma surgeons treating Asian patients. Project Leader Professor Boyko Gueorguiev-Rüegg, Program Leader Biomedical Development at AO Research Institute Davos, said the Strategy Fund funding—which originated with an idea from AO Research Institute Davos Director Professor Geoff Richards—made it possible to bring a great idea to life.

“The main milestones were collecting the computed tomography (CT) scans, processing the CT data and creating the statistical model, and producing the 3-D printed and small series composite bone models in order to present them to the AO surgeon community including the AO Technical Commission Pelvic Expert Group, and AO Pelvis and Acetabulum Education Taskforce,” Gueorguiev-Rüegg explained, adding that all three partners played important roles in advancing the project to completion.

The generic Asian pelvic model is based on 100 randomized CT scans collected and pre-processed by the University of Malaya. Those scans represent Asian patients of Indian, Chinese and Malay descent; Malaysia was the ideal source for the required scans because it is the most appropriate Asian country with populations of those ethnic groups to meet the project’s data needs.

In a second step, Gueorguiev-Rüegg added, several members of his team at AO Research Institute Davos—including a medical research fellow—carried out the data processing, including CT scan segmentation, definition of certain anatomical landmarks on each pelvis, and generating a statistical shape model of the pelvis by the method of principal component analysis. Nine anatomically homologous models were sent as standard-triangle-language (STL) files to SYNBONE, which 3-D printed nine generic Asian pelvic models; these were demonstrated during two meetings at the AO Davos Courses 2017.

“These 3-D printed models represented nine variations: male, female, and unisex, each in three pelvis sizes: average size, a larger size, and a smaller size,” he said. “Feedback was very positive, and we gained some valuable insights.”

For example, Gueorguiev-Rüegg explained, expert surgeons suggested that the project team consider producing versions representing both intact and fractured pelvises of the same size, and remarked that the data implemented in the statistical model could be the basis for future projects.

“For instance, the statistical model could be applied in a project focusing on the acetabular socket,” Gueorguiev-Rüegg said.

In addition, the AO Pelvis and Acetabulum Education Taskforce recommended that the project team eventually develop—based on the existing statistical model—a more specific pelvic model with missing first sacral (S1) bony corridor to reflect the over-proportional occurrence of this anatomical variation that affects approximately 20 percent of the Asian population.

“This is a useful recommendation because such an anatomical variation of the pelvis requires a different fixation method, and the more specific model could better accommodate the surgical training for treatment of such patients,” he added.

After gathering and integrating feedback, the Generic Asian Pelvic Bone Model project team was ready to collaborate with SYNBONE on development of the prototype series.

“Based on all of that feedback, we decided to produce an Asian male model with a common pelvic shape and a female model with the anatomical variation. We sent the corresponding STL files to SYNBONE and their experts converted them to computer-aided design (CAD) files which were adapted by, for example, adding surface roughness to make the models more closely resemble genuine bone,” Gueorguiev-Rüegg said. At its subsidiary in Malaysia in June 2018, SYNBONE developed the aluminum production molds and produced the polyurethane prototypes of the small series (30 pelvises), which the project team demonstrated at the Generic Asian Pelvic Bone Model booth during the 2018 AO Foundation Trustees Meeting in Basel, Switzerland.