This is a retrospective clinical and roentgenographic study to measure the correction of deformity and rigidity of Harrington SSI in the stabilization of unstable thoracic and lumbar spine fractures. 35 patients with unstable thoracic and lumbar spine fracture were treated with Harrington SSI from Feb. 1985 to Mar. 1987 in SNUH and 29 patients were followed up for more than 1 year, average 15.6 months. At final follow up of these 29 patients, 73.1% of patients gained neurologic improvement. Measurement of correction of anterior, middle and posterior column height, local kyphosis and anteroposterior offset were 29.7%, 5.2%, 31.2%, 12.8°and 5.3mm and loss of correction of these were 6.5%, 0.1%, 5.8%, 3.1°and 1.1 mm.