Predictive modelling of trabecular and cortical bone structural architecture is a transdisciplinary research area made possible by funding from the Royal British Legion Centre for Blast Injury Studies and collaboration with the Human Performance Laboratory at Charing Cross Hospital. The research uses a sophisticated range of data recording and computational modelling techniques. Movement data is collected using an array of infra-red cameras to pick up the positions of reflective markers attached to a volunteer carrying out activities of daily living in a defined volumetric space. Coupled with ground reaction force data collected at the same time movement data is used in an open chain inverse dynamics model to find joint moments for the joints of the lower limb (and in more recent research the spine). An optimisation problem is then solved using OpenSim musculoskeletal modelling software, to predict muscle forces resulting in movement at the joints. This is a problem with a high degree of indeterminacy as the number of muscles crossing a joint is in excess of the number of degrees of freedom at the joint. The resulting muscle forces are used in unique structural finite element models of the musculoskeletal system, with a strain driven adaptation algorithm to derive optimised structures, capable of resisting the demands of the range of activities humans undertake on a daily basis, with a minimum volume of bone material.

An advantage of the unique structural approach that the Structural Biomechanics Group takes to modelling the skeletal system is the ability to rapidly run fracture modelling, of value in investigating osteoporotic fragility fractures, civilian injuries sustained in vehicle collisions, and in the field of blast injury studies. A further advantage is the ability to additively manufacture the derived structures, with application in the design of frangible surrogates (work funded by DSTL), tissue engineering scaffolds (work ongoing through an EPSRC KTS award with Embody Orthopaedics), and manufacture of endoprosthetics (collaboration being developed with an orthopaedic device manufacturer).

The work uses similar tools to those employed in digital design and has attracted interest from several engineering consultancies interested in innovative techniques in structural optimisation. A related project on structural optimisation through multiple construction phases is being carried in the EPSRC CDT in Sustainable Civil Engineering, sponsored by Robert Bird Group. Arup, Ramboll and Foster+Partners have also undertaken joint projects at UG and PG level.

The research demonstrate how rigorous basic science research can lead to innovative design solutions in a range of industries.

Dr Andrew Phillps

Structural Biomechanics