Development of mapped stress-field boundary conditions based on a Hill-type muscle model.
Forces generated in the muscles and tendons actuate the movement of the skeleton. Accurate estimation and application of these musculotendon forces in a continuum model is not a trivial matter. Frequently, musculotendon attachments are approximated as point forces; however, accurate estimation of local mechanics requires a more realistic application of musculotendon forces. This paper describes the development of mapped Hill-type muscle models as boundary conditions for a finite volume model of the hip joint, where the calculated muscle fibres map continuously between attachment sites. The applied muscle forces are calculated using active Hill-type models, where input electromyography signals are determined from gait analysis. Realistic muscle attachment sites are determined directly from tomography images. The mapped muscle boundary conditions, implemented in a finite volume structural OpenFOAM (ESI-OpenCFD, Bracknell, UK) solver, are employed to simulate the mid-stance phase of gait using a patient-specific natural hip joint, and a comparison is performed with the standard point load muscle approach. It is concluded that physiological joint loading is not accurately represented by simplistic muscle point loading conditions; however, when contact pressures are of sole interest, simplifying assumptions with regard to muscular forces may be valid.
School of Mechanical and Materials Engineering, University College Dublin, Belfield, D4, Dublin, Ireland.
P
P
Cardiff
A
A
Karač
D
D
FitzPatrick
R
R
Flavin
A
A
Ivanković
D003198:Computer Simulation; D004576:Electromyography / Q000379:methods; D005269:Femur / Q000502:physiology; D005684:Gait / Q000502:physiology; D006621:Hip Joint / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008297:Male; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D013314:Stress, Mechanical; D055815:Young Adult
OpenFOAM; active Hill muscle models; contact stress analysis; electromyography; finite volume method; mapped muscle boundary conditions