Roentgen Stereophotogrammetric Analysis is a highly accurate radiographic technique developed in Lund, Sweden and has for some time been the gold standard in Europe for assessing the stability of implants within bone [13-16]. It is at least ten times more accurate than conventional radiography [17]. The technique involves the insertion of small tantalum markers (0.8mm) into the bone and prosthesis at the time of surgery [15-19]. By using a calibrated cage with additional markers and simultaneous bi-planar x-rays, micromotion at the prosthesis-bone interface can be very precisely determined [20].

The pattern of micromotion exhibited by various prostheses and fixation techniques within the first post-operative year has been shown to be predictive of the long-term fixation of the component to bone [15, 17, 18, 21]. The value of this precise radiographic technique is that new technologies and techniques can be introduced in vivo while limiting their exposure to as few patients as possible. It is a proven, safe and invaluable method for assessing implant component fixation as well as different design concepts [22-27].