Multi-scale simulations, combining muscle and joint contact force (JCF) from musculoskeletal simulations with adaptive mechanobiological finite element analysis, allow to estimate musculoskeletal loading and predict femoral growth in children. Generic linearly scaled musculoskeletal models are commonly used. This approach, however, neglects subject- and age-specific musculoskeletal geometry, e.g. femoral neck-shaft angle (NSA) and anteversion angle (AVA). This study aimed to evaluate the impact of proximal femoral geometry, i.e. altered NSA and AVA, on hip JCF and femoral growth simulations. Musculoskeletal models with NSA ranging from 120° to 150° and AVA ranging from 20° to 50° were created and used to calculate muscle and hip JCF based on the gait analysis data of a typically developing child. A finite element model of a paediatric femur was created from magnetic resonance images. The finite element model was morphed to the geometries of the different musculoskeletal models and used for mechanobiological finite element analysis to predict femoral growth trends. Our findings showed that hip JCF increase with increasing NSA and AVA. Furthermore, the orientation of the hip JCF followed the orientation of the femoral neck axis. Consequently, the osteogenic index, which is a function of cartilage stresses and defines the growth rate, barely changed with altered NSA and AVA. Nevertheless, growth predictions were sensitive to the femoral geometry due to changes in the predicted growth directions. Altered NSA had a bigger impact on the growth results than altered AVA. Growth simulations based on mechanobiological principles were in agreement with reported changes in paediatric populations.

There are many examples from the medical device design industry where poor requirements capture practice has led to post-market problems, including patient morbidity and mortality. There is a clear need to improve this process. The purpose of this paper is to present the results of several years of study by five researchers into the requirements capture process in this area of industry and to highlight the need by industry for further guidance. Various research methods were used to investigate the requirements capture problem and to develop and evaluate a workbook which provides guidance for designers. The workbook consists of a package of methods: a functional analysis approach, a matrix-based checklist and advice on regulatory requirements. It has been refined over the years and is now published [1] The matrix also forms part of a publication for the UK Department for Trade and Industry [2], and a web version is under development.