Effects of kyphosis and lordosis on the remaining lumbar vertebral levels within a thoracolumbar fusion: an experimental study of the multisegmental human spine.

This study was done to determine the motion of the whole lumbar spine after internal fixation and the effect of kyphosis and lordosis on the remaining vertebral levels. Baseline motion analysis of sagittal, frontal, and transverse planes was done to determine the intact range of motion. Three fusion configurations were tested: neutral position (0 degrees), 4.6 degrees +/- 2.0 kyphosis, and -6.2 degrees +/- 3.6 lordosis. The sagittal and frontal plane relative rotation of the instrumented segments (T12/L2) decreased an average of 74% and 60%, respectively, as compared with intact testing. Sagittal plane motion at the remaining segments increased for all fusion configurations when compared with intact motion and reached statistical significance at the L4/L5 level. No significant differences were found between fusion configurations (ie, fused neutral, kyphosis, and lordosis).