In vivo characteristics of spinal kinematics in senile degenerative lumbar spondylolysis

Abstract

Objective: To investigate the in vivo kinematics of the lumbar degenerative spondylolysis (LDS) in senile patients. Methods: From March to October in 2014, nine L(4-5) LDS patients [mean age (74±9) years] and nine healthy volunteers [mean age, (54±4) years] were recruited. Combined fluoroscopy and CT scanning technique were used to obtain the three dimension kinematic data of the vertebral anatomical structures (vertebral body anterior margin, vertebral body posterior margin, facet joints and spinous process) in various postures (supine, standing, flexion and extension) under physical loads, and to compare the stability of different anatomical structures. The L(4-5) segmental disc angle was also measured in different postures. Paired-samples t test was applied to compare the displacement differences between the two groups. Results: During flexion-extension motion, all anatomical structures of the LDS group were slightly larger than those in normal group, but the statistical difference was not obvious (all P>0.05). For normal group, in anterior-posterior and cranial-caudal direction, sub-movement analysis showed that the anterior vertebral body margin at the flexion range of motion [(-1.07±0.84) mm, (-1.27±1.01) mm] were larger than the extension range of motion [(0.66±1.38) mm, (0.63±0.99) mm] (t=3.21, 4.03, both P<0.05). Whereas for LDS group, in anterior-posterior and cranial-caudal direction, sub-movement analysis showed that the anterior vertebral body margin at the extension range of motion [(1.46±1.26) mm, (1.17±0.54) mm] were significantly greater than the flexion range of motion [(-0.43±0.47) mm, (-0.45±1.24) mm] (t=4.22, 3.59, both P<0.05). The disc angles of the LDS group were all smaller than those in normal group, but the statistical difference was not obvious (all P>0.05). However, the disc angles were significantly different under different postures, the flexion were both the smallest in the normal group and LDS group. Conclusions: The senile LDS patients may not necessarily have instability, stability may also occur in these patients. Increasing extension range of motion is one of the kinematic characteristics in senile patients with LDS. The intervertebral stability should be taken into account, but if instability develops, surgical procedure should be suggested for elderly patients with LDS.