The natural history of post-tubercular kyphosis in children - Radiologicalsigns which predict late increase in deformity

The progression of post-tubercular kyphosis in 61 children who received amb ulatory chemotherapy was studied prospectively. The angles of deformity and kyphosis were measured for each patient at diagnosis, 3, 6, 9, 12 and IS m onths later and every year thereafter for 15 years. During the course of th e disease signs of instability appeared on the radiographs of some of the c hildren. These were dislocation of the facets, posterior retropulsion of th e diseased fragments, lateral translation of the vertebrae in the anteropos terior view and toppling of the superior vertebra. Each sign was allocated one point to create a spinal instability score. The influence on the progre ssion of the deformity of the level of the lesion, the vertebral body loss, the number of segments involved, the angle of deformity before treatment a nd the spinal instability score was analysed. The mean angle of deformity at the start of treatment was 35 degrees. This increased to 41 degrees at 15 years. Progression occurred during the active phase of the disease and again after cure when variations in progression w ere observed. Type-I progression showed an increase in deformity until grow th had ceased. This could occur either continuously (type Ia) or after a la g period of three to five years (type Ib). Type-II progression showed decre ase in deformity with growth. This could occur immediately after the active phase (type IIa) or after a lag period of three to five years (type IIb). Type-III progression showed minimal change during either the active or heal ed phases and was seen only in those with limited disease. Multiple regression analysis showed that a spinal instability score of more than 2 was a reliable predictor of patients with an increase of more than 30 degrees in deformity and a final deformity of over 60 degrees. Since sig ns of radiological instability appear early in the disease, they can be rel iably used to identify children whose spine is at risk for late progressive collapse. Surgery is advised in these cases.