BACKGROUND: The clinical application of one-level osteotomy and multilevel osteotomy has been well documented, but currently few studies were reported to compare their biomechanical characteristics.OBJECTIVE: To investigate the biomechanical characteristics of one-level osteotomy with Dick screw fixation and multilevel osteotomy with Luque instrumentation in the treatment of kyphosis.DESIGN: Randomized comparative experiment.SETTING: Laboratory of the Department of Orthopedics, Renmin Hospital of Wuhan University.MATERIALS: Fresh specimens of thoracic and lumbar spinal segments obtained from 12 3 or 4-year-old calves.METHODS: The experiment was conducted in the laboratory of the Department of Orthopedics, Renmin Hospital of Wuhan University between September 2002 and September 2003. Fresh spinal segments T8-L5 from 12 calves were randomized into an intact group, Dick screw group with one-level osteotomy with Dick screw fixation and Luque group with multilevel osteotomy with Luque instrumentation, with 4 spesimens in each group. Lateral bending test of the specimens was performed to examine the physiological overload using an Instron 5 500 universal material testing machine at the constant speed of 10 mm/minute until fracture or dislocation was induced. Changes in the loading were recorded and the induced injuries observed to obtain the load-displacement curve of the injury test.MAIN OUTCOME MEASURES: The load-displacement curve of the destructive right bending test in each group.RESULTS:All the data of 12 canines were involved in the result analysis.The spinal segments of the intact group yielded to the force of 3 600 N with a flat and smooth load-displacement curve, and those of Dick screw group yielded to a load of 2 800 N with also a relatively flat curve, while in Luque group, the segments did not yield until a load of 7 160 N, followed by drastic decrease of the resistance to less than 4 000 N, generating a flat and smooth curve afterwards.CONCLUSION: Luque instrumentation is a little more preferable than Dick screw in terms of the maximum resistance, but this difference does not justify the clinical decision of their superiority. Both techniques benefit postoperative recovery of spinal function with strong stability.