NZ scientist sheds new light on knee injuries

Award-winning NZ scientist sheds new light on knee injuries

University of Auckland scientist Dr Vickie Shim has beaten more than 600 people from around the world to take out the Young Investigator Award Competition at the World Congress on Medical Physics and Biomedical Engineering in Germany.

Dr Shim, who works at the University’s Auckland Bioengineering Institute, won the competition for helping to develop a state-of-the-art computer model of the human knee that could help clinicians design knee braces and knee implants.

The model is believed to be one of the first in the world to include all the soft tissues of a specific person’s knee, including the cartilage, menisci and ligaments.

Musculoskeletal disorders are the leading cause of disability in New Zealand, affecting one in four adults, and costing the country an estimated $5,570 million a year. Knee injuries – including osteoarthritis and injuries to soft tissues - account for 31 percent of these disorders, behind injuries to the lower back and neck. An injury to ligaments or cartilage in the knee is one of the most common injury claims for medical insurance in New Zealand.

“The knee is the most complex – and most injured – joint in the body,” says Dr Shim. “We wanted to create an anatomically correct computer model of the knee that can be customised to take into account a person’s own measurements. We can then predict what’s happening inside the knee without having to cut it open.”

Dr Shim and her colleagues at the Auckland Bioengineering Institute attached special markers to their subject’s lower body to record the movement between the hip, femur, tibia and foot. The subject then walked on special plates to measure the forces exerted on the knee at about every 100th of a second. Finally, an MRI (magnetic resonance imaging) scan was taken of the subject from hip to toe. All this information was plugged into a softwῡre programme to create a unique computer model of the subject™s knee based on a generic knee model.

“Once we have this customised model of a person’s knee we can simulate the movements of the knee joint and contact pressure changes in the knee. By doing this, we can show in more detail how an injury occurred and what the best treatment options might be.”

Previous experiments have measured the contact forces acting on the knee from when the heel of the foot strikes the ground to when the toes touch down. However, Dr Shim and her team have tracked the contact forces over the whole walking cycle, as well as over other activities such as running and climbing stairs.

Dr Shim says the next step is to find out what force the individual muscles around the knee exert, that is the hamstrings, calf muscles and quadriceps.

The modelling work is part of a project by eBonz, a start up company of the Auckland Bioengineering Institute. Dr Shim’s winning paper was co-authored by Dr Iain Anderson from the University’s Department of Engineering Science and Dr Kumar Mithraratne and Professor Peter Hunter of the Auckland Bioengineering Institute.
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