• Lars Hackenberg, Eberhard Hierholzer, Wolfgang Pötzl, Christian Götze, and Ulf Liljenqvist.
• Klinik und Poliklinik für Allgemeine Orthopädie, Universitätsklinikum Münster, Albert-Schweitzer-Strasse 33, 48149 Münster, Germany. lars.hackenberg@uni-muenster.de
• Clin Biomech (Bristol, Avon). 2003 Dec 1;18(10):883-9.

ObjectiveTo determine the accuracy of rasterstereographic three-dimensional back surface analysis and reconstruction of the spine in idiopathic scoliosis treated by posterior correction and fusion.DesignProspective imaging study of 25 patients with idiopathic scoliosis who underwent posterior correction and fusion and were followed for one year.BackgroundIn an earlier study published in this journal rasterstereography has proved to be an accurate imaging modality for quantifying the changes in the three-dimensional shape of the spine and posterior rib cage after anterior correction and fusion. Goal of the present study was to determine the accuracy for the more common posterior correction and fusion with attention paid to the presence of the posterior implants and scarring.MethodsTwenty-five patients with idiopathic scoliosis with maximum Cobb angles of 78 degrees were examined by rasterstereography and radiography. Seventy-one anterior-posterior radiographs were digitised. Twenty-four were preoperative and 47 postoperative radiographs. Rasterstereographic and radiographic curves were compared by best-fit superimposition. Root-mean-square differences were calculated as parameters of accuracy.ResultsThe accuracy of rasterstereography in severe idiopathic scoliosis with Cobb angles between 48 degrees and 78 degrees was satisfactory with root-mean-square differences of 5.8 mm for the lateral deviation and 4.8 degrees for vertebral rotation. Following posterior correction the accuracy was good. The root-mean-square difference was 4.5 mm for the lateral deviation and 4.3 degrees for vertebral rotation.ConclusionThe accuracy obtained for posteriorly-operated scolioses between 50 degrees and 80 degrees was similar to the findings for scolioses operated via anterior approach, as well as those with curves up to 50 degrees Cobb angle. Therefore rasterstereography can be used postoperatively to reduce the number of radiographs and radiation exposure. Additionally, the method provides an objective quantification of the postoperative improvement in the cosmesis of the back shape.RelevanceIn the treatment of severe idiopathic scoliosis rasterstereography provides both a considerable reduction of X-rays and an objective documentation of the cosmesis before after scoliosis surgery.

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