title: Finite Element Modelling of the Femur Bone of a Subject Suffering from Motor Neuron Lesion Subjected to Electrical Stimulation.
abstract: Bone loss and a decrease in bone mineral density is frequently seen in patients with motor neuron lesion due to lack of mechanical stimulation. This causes weakening of the bones and a greater risk of fracture. By using functional electrical stimulation it is possible to activate muscles in the body to produce the necessary muscle force to stimulate muscle growth and potentially decrease the rate of bone loss. A longitudinal study was carried out on a single patient undergoing electrical stimulation over a 6 year period. The patient underwent a CT scan each year and a full three dimensional finite element model for each year was created using Mimics (Materialise) and Abaqus (Simulia) to calculate the risk of fracture under physiologically relevant loading conditions. Using empirical formulas connecting the bone mineral density to the stiffness and ultimate tensile stress of the bone, each element was assigned a unique material property, based on its density. The risk of fracture was estimated by calculating the ratio between the predicted stress and the ultimate tensile stress, should it exceed unity, failure was assumed. The results showed that the number of elements that were predicted to be at risk of failure varied between years.
authors.affiliation: (1) Institute of Biomedical and Neural Engineering (BNE), Reykjavik University , Iceland.
authors.forename: Magnus K
authors.initials: MK
authors.lastname: Gislason
authors.affiliation: (2) Department of Rehabilitation, Landspitali , Reykjavik, Iceland.
authors.forename: Páll
authors.initials: P
authors.lastname: Ingvarsson
authors.affiliation: (1) Institute of Biomedical and Neural Engineering (BNE), Reykjavik University, Iceland; (3) Research Department, Landspitali University Hospital, Reykjavik, Iceland.
authors.forename: Paolo
authors.initials: P
authors.lastname: Gargiulo
authors.affiliation: (2) Department of Rehabilitation, Landspitali , Reykjavik, Iceland.
authors.forename: Stefán
authors.initials: S
authors.lastname: Yngvason
authors.affiliation: (2) Department of Rehabilitation, Landspitali , Reykjavik, Iceland.
authors.forename: Vilborg
authors.initials: V
authors.lastname: Guðmundsdóttir
authors.affiliation: (2) Department of Rehabilitation, Landspitali , Reykjavik, Iceland.
authors.forename: Sigrún
authors.initials: S
authors.lastname: Knútsdóttir
authors.affiliation: (1) Institute of Biomedical and Neural Engineering (BNE), Reykjavik University, Iceland; (3) Research Department, Landspitali University Hospital, Reykjavik, Iceland.
authors.forename: Þórður
authors.initials: Þ
authors.lastname: Helgason
keywords: Bone; Finite element modelling; risk of fracture; spinal cord injury