In spite of care taken in endoprosthetic joint replacement, migration of prosthetic components from fractions of a mm to one cm or more can occur. To detect such "micromotion" in a clinical environment, it is proposed that the positions of radiopaque markers implanted in both the prosthesis and the host bone and positions of their images on two or more conventional X-rays be used in a mathematical model. One implementation illustrates that estimates to within 0.5 mm are possible using prototype models.
James H. Verner,
Urs P. Wyss,
"Mathematical Modelling Of Micromotion In Artificial Joints", Proc. SPIE 1030, Biostereometrics '88, (14 April 1989); doi: 10.1117/12.950470; https://doi.org/10.1117/12.950470