The Ratio of Lumbar to Hip Motion during the Trunk Flexion in Patients with Mechanical Chronic Low Back Pain According to O'Sullivan Classification System: A Cross-sectional Study.

BACKGROUND: Static and dynamic postures of lumbopelvic in low back pain (LBP) are considered as two important aspects of clinical assessment and management of LBP. Thus, the focus of the current study was to compare the posture and compensatory strategy of hip and lumbar region during trunk flexion between LBP subgroupsand health subjects. LBP cases are subdivided into active extension pattern (AEP) and flexion pattern (FP) based on O'Sullivan's classification system (OCS).

METHODS: This work was a cross-sectional study involving 72 men, 21 low back pain patients with FP and 31 low back pain patients with AEP and 20 healthy groups. Lumbar and hip angles during trunk flexion were measured by a 3D motion analysis system in neutral standing posture and end-range of trunk flexion. The participants were asked to full bend without any flexion of the knees. The bending speed was preferential. Hip and lumbar ranges of motion were divided into four quartiles (Q). The quartiles were compared between groups. Data analysis was performed using one-way analysis of variance (ANOVA) and independent t-test.

RESULTS: There was no statistically significant difference in lumbar lordosis in standing and full trunk flexion positions between the healthy groups and heterogeneous LBP groups. In addition, there was not any statistically significant difference between the healthy group and the homogenous LBP group (FP and AEP). Moreover, no statistically significant difference was observed in hip angles during standing between the healthy group and the heterogeneous LBP group, and between the healthy group and the homogenous LBP group (FP and AEP). In full trunk flexion position, there was statistically significant difference in hip angles between the healthy group and the heterogeneous LBP group (P=0.026). In this position, the difference in hip angles between the healthy group and FP group was statistically significant ( P<0.05 ). In the second Q, there was no significant difference between the healthy group and the heterogeneous LBP group ( P=0.062 ), however, there was a significant difference between FP group and the healthy group in the fourth Q of the total hip range of motion. There was no statistically significant difference between the healthy group and the heterogeneous LBP group ( P=0.054 ) but there was a difference between FP group and the healthy group. Lumbar/hip motion ratio (L/H ratio) was different between and within the subgroups in the second Q.

CONCLUSION: This study supported the subgrouping of LBP and showed that the difference between subgroups could be determined effectively through subdividing the total range of lumbar and hip motions into smaller portions. It is possible that the neuromuscular system selects different strategies to compensate and prevent further injury of the chain components (muscle, joint, nerve and etc.).

LEVEL OF EVIDENCE: IV.