2010 Volume 10 Issue Special_Issue Pages s247-s250
Currently, stem insertion during total hip arthroplasty (THA) is not well controlled. The present study investigated a method for improving stem setting in accordance with preoperative planning using a three-dimensional (3-D) computed tomography (CT) model of the femur and RGB images of the excised femoral head. We utilized three femoral heads removed during THA and modeled each head using three spherical acrylic markers. Each femoral head was osteotomized using a parallel jig and three rectangular images of the osteotomized head were taken using a CCD camera. Each femoral head was then set on a camera base and RGB images were taken from three orthogonal directions using the CCD camera. The B-images of the femoral head and the 3-D bone model were processed through image-matching software using an automatic outline extraction and downhill simplex method. The position of the contralateral side of the jig, related to the femur, was measured using a 3-D measuring system in order to validate the accuracy of the image-matching. However, since validation of the accuracy of the image-matching is difficult once the femoral head is excised, a six-degree-of-freedom board was used to facilitate the accuracy validation.
