Measurement of 3D Distance between Artificial Cement-Type Cup and Head After THR

The purpose of our study is a measurement of 3D (three dimensional) distance between an artificial cement-type cup and a artificial femoral head in a living patient´s body after THR(total hip replacement) from an AP(anterior-posterior) Roentgen image and a lateral image, when the angle between the two images is unknown. Recently we proposed a measurement method for non-cement-type cup. We modified the 3D measurement method for a non-cement cup with evolutionary computation(EC) and extend the framework for a cement-type cup. Our method needs only two times of shots using an ordinary Roentgen equipment without measurement the angle of the two images. So our method is superior to Martell´s Method. And it needs no metal balls in a patient body unlike RSA (Roentgen stereophotogrammetric analysis). We show the result of a computer simulation with CG (computer graphics) image we made and the result in vitro with Roentgen images of artificial cup and head moved by a micro-manipulator.