A comparison of radiographic and computer-assisted measurements of thoracic and thoracolumbar sagittal curvature.

Sagittal plane curve characteristics of the thoracolumbar spine were evaluated from 286 lateral chest radiographs comparing the Cobb technique with a computer-aided digitizer. Thoracic kyphosis and curve apex were measured from the T3 to T11 segments, and in 120 cases, the level of the thoracolumbar curve inflexion point was determined. An age-related increase in curve magnitude was similar for both measurements, although computer generated kyphosis angles were generally larger. The apex of thoracic kyphosis was consistently located near T7 for males compared with greater variability with age for females. The thoracolumbar inflexion point shifted caudally with increasing years, being most marked for females. The computer method was more reliable, producing a coefficient of variation of 1.4% on repeated measurement. The ability to describe quantitatively the thoracolumbar curve characteristics, calculate angles between selected segments, determine points of inflexion and maximum curvature, indicates that radiographic evaluation of sagittal spinal curvature is improved with the use of computer-aided measurement.