Natural history of Pott's kyphosis.

The natural history of Pott's kyphosis is different from that of other spinal deformities. After healing of the spinal infection, the post-tubercular kyphosis in adults is static but in children variable progression of the kyphosis is seen. The changes occurring in the spine of children, after the healing of the tubercular lesion, are more significant than the changes that occur during the active stage of infection. During growth, there is a decrease in deformity in 44 % of the children, an increase in deformity in 39 % of the children and no change in deformity in 17 % of the children. The critical factor leading to the progress of the deformity is dislocation of the facets. This can be identified on radiographs by the "Spine-at-risk" signs. Dislocation of facets at more than two levels can lead to the "Buckling collapse" of the spine, which is characteristically seen only in severe tubercular kyphosis in children. Age below 10 years, vertebral body loss of more than 1-1.5 pre-treatment deformity angle of greater than 30° and involvement of cervicothoracic or thoracolumbar junction are the other risk factors for deformity progression. In children, the kyphosis can progress even after healing of the spinal infection and hence children with spinal tuberculosis must be followed-up till skeletal maturity.