A number of papers have recently emphasised the importance of verification, validation and sensitivity testing in computational studies within the field of biomechanical engineering. This review examines the methods used in the development of spinal finite element models with a view to a standardised framework of verification, validation and sensitivity analysis. The scope of this paper is restricted to models of the vertebra, the intervertebral disc and short spinal segments. In the case of single vertebral models, specimen-specific methods have been developed, which allow direct validation against experimental tests. The focus of intervertebral disc modelling has been on representing the complex material properties and further sensitivity testing is required to fully understand the relative roles of these input parameters. In order to construct complex multi-component short segment models, many geometric and material parameters are required, some of which are yet to be fully characterised. There are also major challenges in terms of short segment model validation. Throughout the review, areas of good practise are highlighted and recommendations for future development are proposed, taking a step towards more robust spinal modelling procedures, promoting acceptance from the wider biomechanics community.
1 November 2003 in Journal of Bone and Joint Surgery
The spinal cord is an integral component of the spinal column and is prone to physical injury during trauma or more long-term pathological insults. The development of computational models to simulate the cord-column interaction during trauma is important in developing a proper understanding of the injury mechanism. Such models would be invaluable in seeking both preventive strategies that reduce the propensity for injury and identifying specific treatment regimes. However, these developments are hampered by the limited information available on the structural and mechanical properties of this soft tissue owing to the difficulty in handling this material in a cadaveric situation. The purpose of the present paper is to report the rapid deterioration in the quality of the tissues once excised, which provides a further challenge to the successful elucidation of the structural properties of the tissue. In particular, the tangent modulus of the tissue is seen to increase sharply over a period of 72 h.
The knee joint is a complex mechanical system, and computational modelling can provide vital information for the prediction of disease progression and of the potential for therapeutic interventions. This review provides an overview of the challenges involved in developing finite element models of the tibiofemoral joint, including the representation of appropriate geometry and material properties, loads and motions, and establishing pertinent outputs. The importance of validation for computational models in biomechanics has been highlighted by a number of papers, and finite element models of the tibiofemoral joint are a particular area in which validation can be challenging, due to the complex nature of the knee joint, its geometry and its constituent tissue properties. A variety of study designs have emerged to tackle these challenges, and these can be categorised into several different types. The role of validation, and the strategies adopted by these different study types, are discussed. Models representing trends and sensitivities often utilise generic representations of the knee and provide conclusions with relevance to general populations, usually without explicit validation. Models representing in vitro specimens or in vivo subjects can, to varying extents, be more explicitly validated, and their conclusions are more subject-specific. The potential for these approaches to examine the effects of patient variation is explored, which could lead to future applications in defining how treatments may be stratified for subgroups of patients.