Segmental lumbar rotation in patients with discogenic low back pain during functional weight-bearing activities

Abstract

Background: Little information is available on vertebral motion in patients with discogenic low back pain under physiological conditions. We previously validated a combined dual fluoroscopic and magnetic resonance imaging system to investigate in vivo lumbar kinematics. The purpose of the present study was to characterize mechanical dysfunction among patients with confirmed discogenic low back pain, relative to asymptomatic controls without degenerative disc disease, by quantifying abnormal vertebral motion.

Methods: Ten subjects were recruited for the present study. All patients had discogenic low back pain confirmed clinically and radiographically at L4-L5 and L5-S1. Motions were reproduced with use of the combined imaging technique during flexion-extension, left-to-right bending, and left-to-right twisting movements. From local coordinate systems at the end plates, relative motions of the cephalad vertebrae with respect to caudad vertebrae were calculated at each of the segments from L2 to S1. Range of motion of the primary rotations and coupled translations and rotations were determined.

Results: During all three movements, the greatest range of motion was observed at L3-L4. L3-L4 had significantly greater motion than L2-L3 with left-right bending and left-right twisting movements (p < 0.05). The least motion occurred at L5-S1 for all movements; the motion at this level was significantly smaller than that at L3-L4 (p < 0.05). Range of motion during left-right bending and left-right twisting at L3-L4 was significantly larger in the degenerative disc disease group than in the normal group. The range of motion at L4-L5 was significantly larger in the degenerative group than in the normal group during flexion; however, the ranges of motion in both groups were similar during left-to-right bending and left-to-right twisting.

Conclusions: The greatest range of motion in patients with discogenic back pain was observed at L3-L4; this motion was greater than that in normal subjects, suggesting that superior adjacent levels developed segmental hypermobility prior to undergoing fusion. L5-S1 had the least motion, suggesting that segmental hypomobility ensues at this level in patients with discogenic low back pain.

Fig. 1

Creation of the three-dimensional model. a: Typical T2-weighted magnetic resonance image showing degenerative disc disease at L4-L5 and L5-S1 in a patient with low back pain. b: Digitized contours of the lumbar vertebrae in the sagittal plane. c: Three-dimensional anatomical vertebral model from L1 to S1, constructed from the magnetic resonance imaging.

Fig. 2

The experimental setup of the dual fluoroscopic imaging system (DFIS). a: The dual fluoroscopic system allows for capturing the lumbar spine positions of living subjects. b: The virtual dual fluoroscopic system mimics the actual fluoroscopic system and was used to reproduce the in vivo vertebral positions.

Fig. 3

Local coordinate systems used to calculate the relative six-degrees-of-freedom kinematics of the cephalad vertebra with respect to the caudad vertebra. Three rotations were defined as the orientations of the cephalad vertebral coordinate system in the caudad vertebral coordinate system with use of Euler angles: a (flexion-extension rotation), b (left-right bending rotation), and γ (left-right twisting rotation).

Fig. 4

Bar graphs showing primary rotation range of motion (ROM) (and standard deviation) of patients with degenerative disc disease (DDD) and normal subjects at different levels during physiological activities. The numbers on the x axis indicate the vertebral level; for example, “23” indicates L2-L3, “34” indicates L3-L4, and so on. *Significantly different within degenerative disc disease group (p < 0.05). #Significantly different between degenerative disc disease group and normal group (p < 0.05).