There is debatable opinions as to the nature and clinical significance of the changes that may occur in the spine after posterior spine fusion performed in growing children. Clinical survey is known to be difficult because X-ray films in children are not easy to interpret and measure in the presence of disease and accuracy is uncertain due to magnification on X-ray films. Authors selected 8 cases of tuberculous spondylitis which were managed with posterior spine fusion under the criterias that cases had surgery under 10 years old, no evidence of pseudoarthrosis clinically and roentgenologically on serial examinations at least once 1 year, follow-up more than 2 years since 3 months after surgery, enough spines are included on lateral X-ray films, and accurate measurement and correction of magnification are possible. The cases were surveyed for changes occured in fused spines after posterior spine fusion and the results were as follows: 1. There was actual lengthening of grafted bone mass after solid fusion in all cases although the amounts were minimal. 2. The fused spines grew 46% on an average less than adjacent normal unfused spines. 3. The vertebral bodies of fused spines grew nearly same as the adjacent normal vertebral bodies. 4, The intervertebral disc spaces of the fused spines were narrowed in all cases. 5. The intervertebral angles had tendency to increase and kyphosis angles to decrease.