MORPHOMETRIC EVALUATIONS OF PERSONALIZED 3D RECONSTRUCTIONS AND GEOMETRIC-MODELS OF THE HUMAN SPINE

In the past, several techniques have been developed to study and analy se the 3D characteristics of the human spine: multi-view radiographic or biplanar 3D reconstructions, CT-scan 3D reconstructions and geometr ic models. Extensive evaluations of three of these techniques that are routinely used at Sainte-Justine Hospital (Montreal, Canada) are pres ented. The accuracy of these methods is assessed by comparing them wit h precise measurements made with a coordinate measuring machine oh 17 thoracic and lumbar vertebrae (T1-L5) extracted from a normal cadaveri c spine specimen. Multi-view radiographic 3D reconstructions are evalu ated for different combinations of X-ray views: lateral (LAT), postero -anterior with normal incidence (PA0 degrees) and postero-anterior wit h 20 degrees angled down incidence (PA20 degrees). The following accur acies are found for these reconstructions obtained from different radi ographic setups: 2.1+/-1.5mm for the combination with PAO degrees-LAT views, and 5.6+/-4.5mm for the PA0 degrees-PA20 degrees stereopair. Hi gher errors are found in the postero-anterior direction, especially fo r the PA0 degrees-PA20 degrees view combination. Pedicles are found to be the most precise landmarks. Accuracy for CT-scan 3D reconstruction s is about 1.1+/-0.8mm. As for a geometric model built using a multivi ew radiographic reconstruction based on six landmarks per vertebra, ac curacies of about 2.6+/-2.4 mm for landmarks and 2.3+/-2.0 mm for morp hometric parameters are found. The geometric model and 3D reconstructi on techniques give accurate information, at low X-ray dose. The accura cy assessment of the techniques used to study the 3D characteristics o f the human spine is important, because it allows better and more effi cient quantitative evaluations of spinal dysfunctions and their treatm ents, as well as biomechanical modelling of the spine.