Scoliosis curve correction, thoracic volume changes, and thoracic diameters in scoliotic patients after anterior and after posterior instrumentation

Thoracic volume was calculated in 50 adolescent patients operated on for se vere idiopathic thoracic scoliosis. In 25, anterior instrumentation was use d (group 1), and posterior instrumentation in the other 25 patients (group 2). Calculation of thoracic volume was made from measurements of pre-operat ive and post-operative radiographs. The mean spinal curvature in group 1 wa s 73 +/- 12.4 degrees before the operation, and 19 +/- 15 degrees after the operation, and in group 2 the curvature was 75 +/- 13 degrees before the o peration and 37 +/- 10 degrees after the operation. The calculated thoracic volume in the group with anterior instrumentation increased from 5234 ml p re-operatively to 6043 ml post-operatively, while with posterior instrument ation it increased from 5155 ml to 5489 ml. The correlation between the cha nge in the Cobb angle and the thoracic volume change was poor for both grou ps. To determine the role in the thoracic volume increase of the frontal, s agittal and vertical thoracic diameters, further correlation tests were mad e between these and the thoracic volume increase in each diameter. The best correlation was found between the frontal and vertical increase of diamete rs in group 1, whereas in group 2 the best correlation was found between th e volume increase and the sagittal parameters.