[Effects of inflammation-induced spinal fusion of the lumbar area on movement of the lumbar spine].

Lateral x-rays of the lumbar spine in standing position and functional flexion-extension roentgenograms of 21 patients with spontaneous fusion within the lumbar area after spondylitis were checked related to kyphosis of the block, lordosis and mobility of the lumbar spine and the single discs, and the appearance of degenerative spondylolisthesis. 76% demonstrated degenerative spondylolisthesis of the neighbouring discs, the half of them more than 5 mm with a significant higher number of segmental loosening of the disc caudal to the fusion. The kind of instability is a pseudo-spondylolisthesis (Junghans 1930) above and a retrolisthesis below the fused area. No higher mobility (no significant difference of mobility between the two cranial and the two caudal discs) can be seen as cause of this behaviour. The increased lordosis of the caudal segments is discussed to be the cause of the retrolisthesis distal the fusion. Altogether, kyphosis of the fused area leeds compensatory to a higher grade of lordosis in the mobile part of the lumbar spine without reaching the physiological lordosis of total lumbar spine. Kyphosis of the block does not influence mobility of the discs or the total lumbar spine, but increases significantly the rate of degenerative spondylolisthesis in the vicinal segments. These results suggest the operative reduction of lumbar lordosis in cases of kyphotic spondylitic destruction within the lumbar or thoracolumbar region in younger patients.