The relationship of kyphosis to the shape of vertebral bodies.

An index which measures the wedge deformity of vertebral bodies in lateral chest radiographs in older people was calculated by dividing the sum of the vertical anterior heights of the lower six thoracic vertebral bodies and discs by the corresponding sum of vertical posterior heights. This index increased with increasing age in a similar manner in men and in women, in contradistinction to an index measuring kyphosis in which the age effect was greater in women. The index of wedging explained 42 per cent and 48 per cent of the variation in kyphosis in men and in women respectively. Additional effects due to age, detected in women only, added a further 4 per cent to the explained variation and may be due to ageing of soft tissues.