Reverse engineering of pelvic bone for hip joint replacement

CT Conversion Workflow for Intraoperative Usage of Bony Models: From DICOM Data to 3D Printed Models

This paper presents the application of a low-cost 3D printing technology in pre-operative planning and intra-operative decision-making. Starting from Computed Tomography (CT) scans, we were able to reconstruct a 3D model of the area of interest with a very simple and rapid workflow, using open-source software and an entry level 3D printer. The use of High Temperature Poly-Lactic Acid (HTPLA) by ProtoPasta allowed fabricating sterilizable models, which could be used within the surgical field. We believe that our method is an appealing alternative to high-end commercial products, being superior for cost and speed of production. It could be advantageous especially for small and less affluent hospitals that could produce customized sterilizable tools with little investment and high versatility.

Obtaining patient-specific point model of the human ilium bone in the case of incomplete volumetric data using the method of parametric regions

In this paper, we present the methodology for determining the point model of the ilium bone in cases when volumetric data of the whole bone are not available. An extreme traumatic bone damage, osteoporosis, destruction of bone tissue by malignant bone tumors or the existence of only 2D medical image (X-ray) can be the reason for the lack of complete volumetric data. Points on the bone surface were defined at the curves that run through 26 previously defined parameters, at the edges of anteroposterior (A-P) and lateral projections and at the parts of the surface between some parameters. Those parts of the surface, enclosed by parameters, represent ten parametric regions. The values of coordinates, which represent the input data in the statistical program, were measured in a uniquely defined coordinate system. After establishing the correlations between the values of coordinates, 8869 different linear and nonlinear regression models were obtained. The prediction values for point coordinates were calculated and exported to a CAD program. Results obtained were tested on a randomly chosen male right ilium bone, applying the methodology for creating the prediction model using the method of parametric regions, which allows creating a complete polygonal model, for each region separately or just for some parts of the region. Results obtained in the form of regression equations for the right ilium bone can be applied to the left ilium bone. The results of the research were verified using a comparative deviation and distance analysis between the initial and obtained polygonal models.

Application of quality by design for 3D printed bone prostheses and scaffolds

3D printing is an emergent manufacturing technology recently being applied in the medical field for the development of custom bone prostheses and scaffolds. However, successful industry transformation to this new design and manufacturing approach requires technology integration, concurrent multi-disciplinary collaboration, and a robust quality management framework. This latter change enabler is the focus of this study. While a number of comprehensive quality frameworks have been developed in recent decades to ensure that the manufacturing of medical devices produces reliable products, they are centred on the traditional context of standardised manufacturing techniques. The advent of 3D printing technologies and the prospects for mass customisation provides significant market opportunities, but also presents a serious challenge to regulatory bodies tasked with managing and assuring product quality and safety. Before 3D printing bone prostheses and scaffolds can gain traction, industry stakeholders, such as regulators, clients, medical practitioners, insurers, lawyers, and manufacturers, would all require a high degree of confidence that customised manufacturing can achieve the same quality outcomes as standardised manufacturing. A Quality by Design (QbD) approach to custom 3D printed prostheses can help to ensure that products are designed and manufactured correctly from the beginning without errors. This paper reports on the adaptation of the QbD approach for the development process of 3D printed custom bone prosthesis and scaffolds. This was achieved through the identification of the Critical Quality Attributes of such products, and an extensive review of different design and fabrication methods for 3D printed bone prostheses. Research outcomes include the development of a comprehensive design and fabrication process flow diagram, and categorised risks associated with the design and fabrication processes of such products. An extensive systematic literature review and post-hoc evaluation survey with experts was completed to evaluate the likely effectiveness of the herein suggested QbD framework.

Accuracy evaluation of a lower-cost and four higher-cost laser scanners

Knowing the accuracy of laser scanners is imperative to select the best scanner to generate bone models. However, errors stated by manufacturers may not apply to bones. The three objectives of this study were to determine: 1) whether the overall error stated by the manufacturers of five laser scanners was different from the root mean squared error (RMSE) computed by scanning a gage block; 2) the repeatability of 3D models generated by the laser scanners when scanning a complex freeform surface such as a distal femur and whether this differed from the repeatability when scanning a gage block; 3) whether the errors for one lower-cost laser scanner are comparable to those of four higher-cost laser scanners. The RMSEs in scanning the gage block were 2 to 52µm lower than the overall errors stated by the manufacturers. The repeatability in scanning the bovine femur 10 times was significantly worse than that in scanning the gage block 10 times. The precision of the lower-cost laser scanner was comparable to that of the higher-cost laser scanners, but the bias was an order of magnitude greater. The contributions of this study are that 1) the overall errors stated by the manufacturers are an upper bound when simple geometric objects like a gage block are scanned, 2) the repeatability is worse on average three times when scanning a complex freeform surface compared to scanning the gage block, and 3) the main difference between the lower-cost and the higher-cost laser scanners is the bias.