Estimation of 3D Pose of Femurs in Bi-planar Digital Radiographs

Abstract

Pre-operative planning in orthopedic surgery is essential to identify the optimal surgical considerations for each patient-specific case. Estimation of the three-dimensional (3D) pose of bones plays an important role in computer assisted diagnosis and surgery. However, understanding the 3D pose of femoral fractures on plain radiographs is challenging, and 3D imaging modalities such as Computed Tomography (CT) are still being restricted to a minority of complex orthopedic procedures. Although the existing application has focused on registering a 3D model of the bone to the images of the same bone intra-operatively, pre-operative 3D pose estimation is more valuable for surgery planning. This paper proposes a method for recovering 3D pose by registering a preoperatively prepared generic 3D model of a bone to bi-planar (frontal and lateral) digital radiographs (DR images) of different patients. It can perform 3D-2D registration with unknown correspondence automatically without invasive external fiducial markers. This 3D-2D registration will identify the position and orientation of the femur in six degrees (R x ,R y ,R z ,t x ,t y ,t z ) of freedom. Validation results using different femurs show that this method is robust and accurate in estimating the 3D pose of femurs in bi-planar radiographs of different patients.