The only way to determine minimal abrasion, such as that which occurs between the two metal surfaces of an artificial hip joint, with high levels of precision is to use a new test method. The amount of wear debris from the articulating surfaces that falls into the surrounding liquid is determined using a movement simulator; the liquid is analysed with a high-resolution mass spectrometer. This highly precise method, which also shows high accordance with patient reality, has the potential to contribute to the development of lifelong prostheses. On 16th June, Dr. Jan Philippe Kretzer, Head of the Laboratory of Biomechanics in the Department of Orthopaedics at the University Hospital Heidelberg, was awarded the German Arthritis Foundation Science Prize worth 5,000 euros.
In Germany, around 180,000 patients per year are given hip joint implants. As the prosthesis loosens and wears over time, it becomes necessary to replace the implant after an average of 15 to 20 years. Changing the hip joint is time-consuming and can also lead to complications. Young people in particular as well as the young at heart who lead active lives are especially interested in the possibility of having a long-life artificial joint implanted.
Before becoming Head of the Laboratory of Biomechanics and Implant Research at the Department of Orthopaedics at the University of Heidelberg, Kretzer worked on modern methods for the diagnosis of brain disorders. In his new position, Kretzer is primarily focused on the abrasion of artificial hip and knee joints. When two metal articulation surfaces slide along each other, even minimal abrasion causes the smallest metal particles and ions to be released from the prosthesis material. The concentrations are so small that they can only be precisely determined with a high-resolution mass spectrometer (HR-ICP-MS). “With our measurement method we are able to obtain new insights into the abrasion behaviour of implant materials that might be used for the development of innovative joint replacement materials that are more stable than existing ones,” said the researcher explaining the importance of the new method.
Kretzer has developed a simulation system that realistically models the load on an artificial hip joint under 24-h operation. The small abrasion particles and the soluble metal ions pass into the surrounding liquid, which can subsequently be analysed. The results provide information about abrasion phenomena and production-related effects that affect the wear of the material. The method is able to precisely determine the actual wear and debris generation and provides similar results to those obtained in clinical studies with patients. "The test is clearly superior to conventional methods used to determine abrasive wear," said Kretzer who has also shown that abrasion occurs mainly during the first months after surgery. After this initial run-in period, abrasion drops to minimal values. And it is this phase where improvements to prolong the lifetime of articulation pairing components can be made.
The Science Prize is mainly given to young researchers for outstanding scientific achievements in the field of arthritis research and therapy. The 2009 winner was selected by a jury from a total of 12 doctoral theses. There are still no effective arthritis treatments available, as damaged joint cartilage does not regrow. Arthritis is the major reason why patients are given artificial hip joints. Many arthritis sufferers are condemned to a life with extreme back pain and inability to move around as they would like, which has an effect on the quality of life and sometimes can even lead to sufferers losing their job. The objective of the German Arthritis Foundation is to find effective remedies for the treatment of this disease.