Détermination rapide des paramètres caractéristiques des scolioses en vue frontale

Abstract

Scolioses are pathologies changing the three-dimensional shape of spines. Numerous biomechanical studies reconstructed spines, from photogrammetric radiography. Each vertebra is represented by several landmarks, of which frontal and sagittal projections are recorded on the digitised film. These reconstructions, involving a great number of points, are accurate, but are time consuming. They describe evolving pathologies but the technique requires a specific radiographic protocol. A new approach has been studied in order to decrease time needed recording and treating data and delivering accurately parameters used clinically. It is applied to frontal deformations due to scoliosis. One numerical radiographic image is only needed. Three-dimensional spine is considered as a continuous beam of which frontal projection is bounded by two continuous curves. A small number of points, from 6 to 9, are recorded representing bounds. A continuous curve (B-spline) is constrained to pass through the recorded landmarks. Interactive software allows experimenter to adapt the global continuous bounding curve to the real projection by acting on local records. A mean curve representing the beam frontal projection is drawn. This mean curve is segmented in regions showing homogeneous concavities. Parameters describing the shape and angular tilting of each region are proposed for clinical applications. Vertebral bodies are located along the mean spinal curve. Analogous techniques are applied estimating axial rotation of vertebrae about the mean line of spine. The new approach is displayed using radiographic files of scoliotic patients. The new technique will be extended to the sagittal view with the goal of three-dimensional reconstructions.