A Comparison of Lumbosacral Kinematics during Prolonged Sitting in Non-specific Chronic Low Back Pain Subgroups; a cross-sectional study

Abstract

Background: Although, non-specific chronic low back pain (NSCLBP) has been associated with abnormal lumbosacral kinematics, little is known about the possible driving mechanisms of pain development overtime during prolonged sitting period. Therefore, the purpose of this study was to examine the differences in lumbosacral postures in adults with and without NSCLBP, and their role on pain development during a 1-hour of prolonged sitting task. Methods: Twenty NSCLBP subjects with motor control impairment (MCI) [10 classified as having flexion pattern (FP) disorder, and 10 with active extension pattern (AEP) disorder], and 10 healthy controls participated in the study. Subjects underwent a 1-hour sitting protocol on a standard office chair. Lumbosacral postures including: sacral tilt (ST), third lumbar vertebrae (L3) position, and relative lower lumbar angle (RLLA) were recorded using a two-dimensional inclinometer over the 1-hour period. Perceived back pain intensity was recorded using a numeric pain rating scale every 10 minutes throughout the sitting period. Results: All study groups presented with significantly distinctive lumbosacral kinematics at the lowest level of pain (the beginning of the sitting period) (p<0.05), as well as at the highest level of pain (the end of the sitting period) (p£0.05). The MCI subgroups showed a significant deterioration in lumbosacral kinematics and pain levels overtime (p<0.01). The directions of deterioration in lumbosacral kinematics over the 1-hour sitting period occurred in the direction of the motor control impairment (kyphosis for FP subgroup or lordosis for the AEP subgroup). Both MCI subgroups reported a similarly significant increase in pain through mid-sitting (p<0.001). However, after mid-sitting, the AEP subgroup displayed a significantly reversed decrease in the lordotic postures (p=0.001) which was accompanied by much less increase in pain level compared to the FP subgroup. Conclusion : The present study’s findings suggest that MCI subgroups presented with distinctive underlying maladaptive postural patterns. However, the significant increase in pain over the 1-hour sitting might not be only attributed to the inherent maladaptive postures, also it may be related to the directional deterioration in lumbosacral postures overtime.