Validation of the non-stereo corresponding points stereoradiographic 3D reconstruction technique

Several 3D reconstruction techniques deriving from stereoradiographic DLT have been presented during the last 15 years, but these techniques have usually been limited in accuracy because of the small number of corresponding anatomical landmarks identified on both radiographs. A new technique has recently been proposed to perform 30 reconstruction of the spine using not only the stereo-corresponding anatomical landmarks (seen on both frontal and sagittal X-ray films) but also some non-stereo-corresponding ones. This technique (called non-stereo-corresponding points or NSCP) has already been used for cervical dry vertebrae. In the present study, we focus on the validation of this technique for lumbar vertebrae by comparing four techniques: direct measurement, CT scan, 30 reconstruction by stereoradiography using a direct linear transformation (DLT) algorithm and the NSCP technique. The accuracy of the NSCP technique was also evaluated on different vertebral regions. The global results show mean errors of 1.1mm and maximum of 7.8mm with regard to direct measurements. These mean errors are close to those obtained using 30 reconstructions from CT scan using 1mm cuts.