3D reconstruction of a patient‐specific surface model of the proximal femur from calibrated x‐ray radiographs: A validation studya)

Abstract

Twenty-three femurs (one plastic bone and twenty-two cadaver bones) with both nonpathologic and pathologic cases were considered to validate a statistical shape model based technique for three-dimensional (3D) reconstruction of a patient-specific surface model from calibrated x-ray radiographs. The 3D reconstruction technique is based on an iterative nonrigid registration of the features extracted from a statistically instantiated 3D surface model to those interactively identified from the radiographs. The surface models reconstructed from the radiographs were compared to the associated ground truths derived either from a 3D CT-scan reconstruction method or from a 3D laser-scan reconstruction method and an average error distance of 0.95 mm were found. Compared to the existing works, our approach has the advantage of seamlessly handling both nonpathologic and pathologic cases even when the statistical shape model that we used was constructed from surface models of nonpathologic bones.

Radiographic reconstruction of lower-extremity bone fragments: a first trial

“…The 2D/3D reconstruction of the bone fragments is based on a previously developed methodology [16]. This methodology was originally developed for the reconstruction of the proximal femur, but can be applied for the reconstruction of any other bone.…”

“…A final non-rigid deformation step is applied to optimally reconstruct the underlying bone geometry. For more details of this algorithm we would like to refer to this work [16].…”

“…We are mainly interested in the rotational arrangement of the fragments and not in the precise fragment length or the appearance of the fracture site. Both bone fragments are then independently matched to the radiographic scene based on the methodology introduced in [16]. In the first step five pre-defined landmarks were picked for each fragment on both radiographs.…”

“…The contours are drawn along the bone edges, whereas the fracture site is omitted. The remaining steps were performed as described in [16]: The model fragments were first iteratively fit to the image scene, instantiated and then non-rigidly deformed to recover the shape of the underlying bone fragments.…”

“…(1) In order to assess the rotational alignment of the bone fragments, 2D/3D registration technique is employed to reconstruct surface models of the proximal and distal fragments from a set of conventional X-ray radiographs. We will present the adapted 2D/3D reconstruction framework [16] for extracting patient-specific surface models of fractured femur and tibia bones from biplanar radiographs. (2) Two studies were performed to validate the accuracy of the overall system.…”