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‘On my own I would achieve nothing’

Edward Valstar, Biomechanica department

Professor Edward Valstar carries out research into mechanical loosening of artificial hips and knees, his aim being to create prostheses that last a lifetime. In late 2012, he was appointed Antoni van Leeuwenhoek Professor in Delft. Originally a mechanical engineer, he divides his time between Leiden University Medical Center (LUMC) and TU Delft, where he works in the Biomechanics department. He also heads the Biomechanics and Imaging Group (BIG) in the Orthopaedics department of the LUMC.

Standing on the shoulders of giants. It is an oft-used metaphor to describe how scientific successes would not be possible without work previously carried out by other scientists. Edward Valstar, too, praises the contributions of his predecessors and colleagues towards his work, but in his case the shoulder has actually played a physical part in his career. His graduation project was on Frans van der Helm, Gijs Pronk, and Henk Stassen’s well-known muscle and skeletal model of the shoulder. For this, he worked on an x-ray/video project in Leiden. “I was carrying out tests with a few other students, when a Leiden professor of orthopaedics asked who would like to stay for three months in order to help develop software. The labour market for mechanical engineers was very bad in 1993, so I thought it would at least be a good chance to get some experience. That was twenty years ago.”

As the years passed, his interest moved from the shoulder to the hip and the knee, the places where artificial joints can be implanted. A significant development in those twenty years is that of Roentgen Stereophotogrammetric Analyse (RSA), a technique for showing in 3D to the last micrometre whether artificial joints are moving in relation to the bone. That is crucial because early migration of artificial joints is a clear sign of future failure. “Threequarters of artificial joints that have to be replaced work themselves loose”, explains Valstar. Around ten per cent of hip implants fail within a year. That might not seem very many, but given that 2.5 million joint implants are made each year worldwide, the number of failures in absolute terms is very high. Moreover, the number of operations is expected to rise to around 7.5 million in the years to come, given that we are all living longer and getting heavier.

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