Abstract
Summary Statement
Computational models are the primary tools for efficient design-phase exploration of knee replacement concepts before in vitro testing. To improve design-phase efficiency, a subject-specific computational platform was developed that allows designers to assess devices in realistic conditions by directly integrating subject-specific experimental data in these models.
Introduction
Early in the design-phase of new implant design, numerous in vitro tests would be desirable to assess the influence of design parameters or component alignment on the performance of the device. However, cadaveric testing of knee replacement devices is a costly and time-consuming procedure, requiring manufacture of parts, preparation of cadaveric specimens, and personnel to carry of the experiments. Validated computational models are ideally suited for pre-clinical, high-volume design evaluation. Initial development of these models requires substantial time and expertise; once developed, however, computational simulations may be applied for comparative evaluation of devices in an extremely efficient manner [Baldwin et al. 2012]. Still, computational models are complementary of experimental testing and for this reason, computational models tuned with subject-specific experimental data, e.g. soft tissue parameters, could bring even more efficiency in the design phase. The objective of the current study was to develop a platform of tools that easily allows for subject-specific knee simulations. The system integrates with commercially available medical imaging and finite element software to allow for direct, efficient comparison of designs and surgical alignment under a host of different boundary conditions.
Patients & Methods
MRI image was acquired, and 3D bone models were generated using the Mimics Innovation Suite® (Materialise NV, Leuven, Belgium). The two models (1) tibiofemoral (TF) joint laxity including ligamentous constraint and (2) whole joint (TF and patellofemoral (PF)) mechanics during dynamic activities of daily living (e.g. gait, squat, chair-rise), developed in Abaqus/Explicit (SIMULIA, Providence, RI), were then be adapted with integrated subject-specific attachment sites.
Results
The suite of tools provides a platform for baseline evaluation of design factors, comparison of new implant designs with predicate devices, and assessment of robustness to surgical alignment. This platform is currently capable of taking into account subject-specific factors in order to provide realistic results in relation with experimental data. Implant material properties, ligament properties and initial conditions can be varied, and results compared, to evaluate the influence of a host of design and surgical factors on implant performance. The interface allows users without complex finite element expertise to setup, analyze and compare devices and interpret results.
Discussion/Conclusion
A platform which allows implant designers to evaluate their design ideas in realistic conditions integrating subject-specific parameters and to compare with predicate devices has the potential to substantially decrease the development time for new devices. Designers can perform iterative modification to their devices to focus on an optimal design solution prior to in vitro testing, reducing the number of pre-clinical cadaveric experiments that may be required, and ultimately improving TKR mechanics in the patient population.
