Musculo-skeletal System Group current projects

This research aims to analyse body shape differences within the population using 3D body surface scanning and relate these findings to underlying musculoskeletal structure and function. 3D body scanning is a non-invasive procedure that takes only a few seconds. The result is a detailed virtual representation of the body surface. Anthropometric analysis provide useful information to health care providers, fashion industry and manufacturing sectors.

We are currently conducting pilot work in setting up measurement system and imaging protocols.

Contact
Katja Oberhofer
Email: k.oberhofer@auckland.ac.nz

This project is aimed at creating a detailed model of skeletal muscle function, incorporating a full set of anatomical and physiological data. Individual skeletal muscle fibres are represented within a 3-dimensional muscle geometry. The muscle geometry is created from CT sections of the body and includes important anatomical information such as fibre angles and intramuscular tendons. The muscle is activated using a detailed control system, which can represent normal muscle activation, or altered activation. The mechanical deformation of the muscle as a result of muscle activation is calculated using a novel constitutive law. The project has been done in collaboration with AgResearch.

In addition, work involving the simulation of electrical stimulation of skeletal muscle and nerve tissue has been undertaken. Finite element models have been created of the strength of electrical fields passing through skin, and other body tissue, and the resulting action of skeletal muscle and nerve tissue as a result of the electric field.

Contact
John Davidson
Email: jdav108@aucklanduni.ac.nz

Oliver Roehrle
Email: roehrle@mechbau.uni-stuttgart.de

Juliana Kim
Email: juliana.kim@auckland.ac.nz

Deep vein thrombosis (DVT) is a common problem in hospitalised patients. A commonly used prophylaxis against DVT is application of external pressure (e.g. compression stocking). The aim of this computational model is to simulate the action of external compression on the lower leg, investigate the flow in deep as well as superficial veins and estimate the vessel wall shear stress changes. The wall stress influences the tissue plasminogen activator (t-PA) and its gene expressions. t-Pa then converts plasmingen to active plasmin, which dissolves fibrin and prevents thrombus formation. We intend to simulate dorsi and plantar flexion of the foot to determine the effect of these manoeuvres on blood flow. The coupled model has other applications such as comfort analysis in sitting.

Contact
Kumar Mithraratne
Email: p.mithraratne@auckland.ac.nz

Fractures of the pelvis and acetabulum are among the most serious injuries treated by orthopaedic surgeons, requiring rapid and precise treatment and, in some cases, one or more surgical procedures. Biomechanically based computer models of the hip joint will be a great aid in understanding mechanisms of the fracture and hence in developing better fixation techniques. Moreover subject-specific finite element models of patients with pelvic/acetabular fractures will be a powerful tool for surgical planning and patient management. We are developing a computer model of the hip joint that includes all the major bones and soft tissues in the joint. The model will be used to investigate how fracture occurs under various impact conditions. Moreover the fracture pelvis model will be used to optimize techniques for fracture reduction by performing extensive biomechanical testing in silico.

Contact
Vickie Shim
Email: v.shim@auckland.ac.nz

A framework is currently being developed to analyse tibio-femoral contact pressure during gait with a view of using it for a variety of clinical applications. Optimisation techniques with suitable constraints are used to estimate the individual muscle forces based on inverse dynamics. The individual muscle forces thus estimated will be prescribed as boundary conditions for a continuum model to investigate the bony surface contact pressure during joint articulation. We perform kinematic and kinetic analyses, optimisation and continuum modelling using subject-specific, bio-physically based models. The resulting framework will be extended, once validated, to other joints of the human body.

Read more about the ABI gait research project.

Contact
Kumar Mithraratne
Email: p.mithraratne@auckland.ac.nz

Katja Oberhofer
Email: k.oberhofer@auckland.ac.nz

We have developed a three dimensional finite element model of human mastication with a special focus on an anatomically realistic model of the masseter muscles. A motion capture system is used to track the jaw motion of a subject chewing standard foods. The deformation of the masseter muscles are calculated via the finite element method, using the jaw motion data as boundary conditions. A particular focus of one of our studies was to compare the muscle force output from the three dimensional muscle model with a more traditional one-dimensional model. The results strongly suggest that modelling skeletal muscles as conventional one-dimensional lines of action might introduce a significant source of error.

Contact
Oliver Roehrle
Email: roehrle@mechbau.uni-stuttgart.de

Modelling the morphology, that is the shape and density, of individual bones is useful in surgery planning and biomechanical modelling. Finite Element (FE) models have been successfully applied to this end. On a population basis, variations in bone morphology can offer insights into the health of the population, as well as provide guidelines for prosthesis design and use. Coupling bone morphology to other patient information allows for inferences regarding patient background to be carried out. Statistical shape analysis (SSA) has the ability to decompose and model shape variations present in a training set using relatively few parameters. We aim to use SSA and FE methods to create workflows for automatically extracting, representing, and analysing the morphological variations of bones in large populations.

Contact
Ju Zhang
Email: jzha263@aucklanduni.ac.nz

Cerebral Palsy (CP) results from an injury in the developing brain which often leads to progressive musculoskeletal impairments. Recent studies suggest that the structure and material properties of muscles in children with CP are significantly altered. However, the details of the changes are not well understood, and the biomechanical consequences difficult to measure. The aim of this project is to provide more insights into muscle architecture and muscle function in children with CP by means of subject-specific, anatomically-based modelling of the musculoskeletal system. Relevant research questions are investigated in collaboration with Starship Children’s Hospital.

Contact
Katja Oberhofer
Email: k.oberhofer@auckland.ac.nz

A novel virtual reality tool for training surgeons is under development. The simulator uses the CT scans of a patient's hip to customise a model allowing the surgeon to virtually operate on a model specific to the patient's anatomy. The simulator provides objective feedback on the surgeon's performance. Once fully developed the simulator may allow comparison between trainees, and assessment of improvements and learning. We are currently assessing the system as a training tool for hip fracture procedures.

Contact
Phil Blyth
Email: phil.blyth@otago.ac.nz

A finite element model of the equine hoof is being created to investigate the biomechanical effects of different hoof shapes. Mesh geometry is automatically generated from a parametric CAD model and a wide variety of shapes are possible. A non-homogenous and anisotropic material model is used to account for the effect of the varying moisture content and the tubule microstructure of the keratinous hoof capsule. Lamellar tissue, connecting the capsule to the underlying pedal bone, is modelled by a non-linear anisotropic material law. Potential uses are studying the effects of hoof trimming and balancing methods, modelling ground interaction and investigating the functional morphology of the hoof.

Contact
Glenn Ramsey
Email: g.ramsey@auckland.ac.nz

Martyn Nash
Email: martyn.nash@auckland.ac.nz

We have developed a three dimensional finite element model of the tongue, which includes an anatomically realistic description of the muscle fibre distribution, in order to investigate the complex deformation patterns of the tongue during normal mastication, swallowing, and speech production. The material properties of the tongue are modelled using a multi-fibre-reinforced hyper-elastic material description superimposed with active contractile properties along the fibre directions. The activation of specific muscle fibre groups within the model has reproduced simple but realistic deformations of the tongue.

Contact
Yikun Wang
Email: yikun.wang@auckland.ac.nz

Martyn Nash
Email: martyn.nash@auckland.ac.nz

Oliver Roehrle
Email: roehrle@mechbau.uni-stuttgart.de

This research project is investigating bone remodelling in the cortical bone to better understand fracture susceptibility. The project is conducted in collaboration with the School of Dentistry at Melbourne University, Australia, and the CSIRO Computational Modelling group.

Contact
Justin Fernandez
Email: j.fernandez@auckland.ac.nz