INTRAOPERATIVE OPTOELECTRONIC ANALYSIS OF 3-DIMENSIONAL VERTEBRAL DISPLACEMENT AFTER COTREL-DUBOUSSET ROD ROTATION - A PRELIMINARY-REPORT

Study Design. This study analyzed intraoperatively the three-dimension al displacement of vertebrae during rotation of the Cotrel-Dubousset r od for scoliosis correction, using an optoelectronic method. Objective s. To evaluate three-dimensional translations and rotations of instrum ented and uninstrumented vertebrae, produced by the Cotrel-Dubousset i nstrumentation ''derotation'' maneuver. Summary of Background Data. Pu blished reports indicate that Cotrel-Dubousset instrumentation has bee n more effective in producing spinal derotation than vertebral axial d erotation, but no study analyzed intraoperatively the effects on the V ertebrae produced solely by relation of the rod. Methods. Eight patien ts with idiopathic scoliosis treated with Cotrel-Dubousset instrumenta tion underwent intraoperative optoelectronic monitoring using infrared cameras (Vicon). Markers were implanted in the spinous processes of t he lower and upper instrumented vertebrae (LIV, UIV), the adjacent uni nstrumented vertebrae below and above (-LIV, +UIV), and the apical ver tebra. During rod rotation, acquisition and processing of cameras data were performed to obtain three-dimensional displacements of vertebrae . Results. Translations and rotations of LIV and UIV were in identical directions to those of -LIV and +UIV, respectively. Orientation of th e LIV hook influenced the displacement of LIV and -LIV. Posterior tran slation of the apical vertebra was commonly observed in thoracic King II, III, or V curvatures (apical vertebra = T9), and anterior translat ion in King I and IV and thoracolumbar curvatures (apical vertebra = T 11-T12). Axial rotation of the apical vertebra was increased in thorac ic curvatures and decreased in thoracolumbar and lumbar curvatures. La teral translation was the major displacement observed. Conclusions. Ro tation of the rod produces rotational and translational changes along each axis. These results are preliminary, but substantial. Technical i mprovement would allow more accurate results in the near future.