 Implant failure due to aseptic loosening is thought to arise from both patient related factors such as age, sex and diagnosis, and from implant related factors such as design and materials used 5. Efforts at reducing aseptic loosening by changing implant design and cement formulation have occasionally resulted in products that perform well in the laboratory but fail miserably in real life, often after being implanted into large numbers of patients7-10. This has led to a call for careful and controlled introduction of new implant designs using randomized trials and precise radiographic assessment techniques such as radiostereometric analysis RSA to look for early signs of loosening and impending failure 7, 9, 11. 