Outline of research projects

With more than 20 PhD students affiliated to CIRRO and the senior researchers projects in addition, only a few projects will be mentioned here. Our projects fits well into the research strategy of South-Eastern Norway Regional Health Authority in that they are usually directly transferable to clinical practice, and has consequences for single patients as well as health economic perspectives. CIRRO was originally started to be able to measure both implant stability and bone remodelling, and our first publication showed that the NTNU-developed femoral stem Unique was more stable than a conventional stem, but lost more bone during the first 2 years postoperatively 11. We implanted the first femoral stem with a new biological bone-like coating, and have shown that it is as stable as an ordinary coating and retains more bone in the femur 18. Measuring bone remodelling around a cemented prosthesis is difficult since bone cement contains radioopaque contrast medium. After a large in-vitro study 15, we have randomized patients to cement with and without contrast. This will be very important, and new, knowledge for understanding bone remodelling with cemented prosthesis. The optimal time for doing reference examination for bone remodelling studies has never been established. We measured patients day 1, 5 and 14 after surgery and found that there was no early bone loss 16. This is an important finding since the time window for doing DXA has been proved to be at least 14 days, which makes it possible to study injured and newly operated patients.DXA has been used in numerous animal studies at CIRRO. Dimmen showed in his PhD that the new selective COX-2 inhibitors impaired bone and tendon healing just as much as the unselective cox-inhibitors. In a clinical multicentre study 9, we found that the widely used COX inhibitors (e.g. Ibumetin) given to hip fracture patients increased the risk for non-union by a factor of 2.55 (these findings are under publication). Berntsen showed that obese children who trained lost fat mass even if they did not lose total weight, an encouraging finding for this group which is difficult to treat 10.
We have as the first group in the world used RSA to study wear of cartilage in humans. Tantalum balls was implanted in the acetabulum during insertion af a hemi-prostheis for femoral neck fractures. Wear was low during the first year (Figure 6).
In a study of multiple sclerosis (MS) patients it was shown that at onset of disease they had already lower bone density than a control group 19. This is compatible with a common etiological or pathogenic factor in MS and osteoporosis, and will be a topic for further research.