22 November 2008
Muscle model assists kids
1 September 2006
By Cameron Broadhurst: Te Waha Nui Online
More than 7000 people in New Zealand have trouble walking normally because of cerebral palsy. Te Waha Nui investigates groundbreaking research that could change this.
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Photo: Cameron Broadhurst
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The treatment of cerebral palsy could be transformed through research being conducted at the Auckland Bioengineering Institute into the complicated anatomy of human muscles.
Among the team modelling the human musculo-skeletal system in the international physiome project is Swiss student Katja Oberhofer.
She is working on a computer tool to assess how human leg muscles contract and lengthen when walking.
More than 7000 New Zealanders and countless people worldwide have trouble walking normally because of cerebral palsy.
Dr Kumar Mithraratne, Oberhofer’s superviser and a musculo-skeletal researcher, says the neuromuscular disease stops muscles voluntarily contracting, a problem surgeons attempt to fix by cutting fibres to lengthen the muscle.
Currently there is no way to directly measure muscle length during walking.
Oberhofer’s thesis project is specifically aimed at telling surgeons more about how children with cerebral palsy move, and which muscles to target for surgery. She says she hopes to have a working tool by the end of her thesis, in the next three to four years.
Yet the research has implications beyond just cerebral palsy. Oberhofer says it could apply “wherever you are interested in locomotion”, from knee and hip replacements to coaching sport.
While the study of walking, or gait analysis, is commonplace in fields as diverse as shoe design and computer games, Oberhofer says the current methods lack necessary detail because they are only taken from skin points.
Surgeons working from a stick-figure type model then have to estimate which muscles to operate on.
Her tool will use MRI images to flesh out points throughout the muscle mass, giving patient-specific detail which can be matched to an existing generic model.
The generic musculo-skeletal model is based on data from the donated body of an executed American prisoner.
The data, collected through the Visible Human Project, is made up of more than 1800 cross sections at one millimetre intervals, taken from the corpse and digitised to create maps of the whole human body.
Oberhofer has already taken MRI scans of her own legs to work on, but doesn’t yet know how the leg muscles of children with cerebral palsy will be different to those of the generic model.
“We don’t really know their anatomy. We don’t know if they have huge deformities or not,” she says. “It’s computationally really, really big.”
When testing begins in October, 12 children with cerebral palsy and 12 without will be scanned and analysed over the course of two years to create patient-specific models.
Dr Peter Hunter, director of the institute and overseeing most of the work on the Physiome Project, says models are never finished: “You just keep on improving them.”
He says the idea is “to make use of the information that’s obtained from those children to make better surgical decisions”.
But Oberhofer says if the patients do differ significantly from the generic model, assessing them will be a lot more complicated.
Associate professor of paediatric orthopaedic surgery, Susan Stott, works at Starship Children’s Hospital with children who have cerebral palsy.
She says the computer methods of gait analysis now in use take account of different weights and heights, but don’t use patient-specific models of legs and body.
Stott says it is impractical to carry out an MRI scan on every patient, but hopes the research will help adjust the models according to patients’ ages and specific problems, and aid surgeons in predicting how much individual patients could benefit from surgery.
